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Is I
THE MICROSCOPY OF DRINKING WATER
BV
GEORGE CHANDLER WHIPPLE
Gordon McKay Professor op Sanitary^nginbbring,
Harvard University
WITH A CHAPTER OX
THE USE OF THE MICROSCOPE
By JOHN W. M. BUNKER, Ph.D.
THIRD EDITION, REWRITTEN AND EXLARGED
WITH COLORED PLATES
SECOND THOUSAND
NEW YORK
JOHN WILEY & SONS, Inc. London: CHAPMAN & HALL, Limited
Copyright, 1899, 1905, 1914
BY
GEORGE CHANDLER WHIPPLE
WORKS OF 6. C. WHIPPLB
PUBUSBKD BT
JOHN WILEY A SONS, Inc.
The Microscopy of Drlnklns-water.
Third edition, rewritten. 8vo. zzi+400 pages. 73 figures and 6 pUtcs in the text and 19 full- page plates in colors. Cloth. $4.00 net.
The Value of Pure Water.
Large 12mo, viii +84 pages. Cloth. $1.00.
Typhoid Fever— Its Causation, Transmission and Prevention.
Introduction by Wiluam T. SsDawicK. Ph.D. Large 12ino, zzzvi +407 pages. 50 figures. Cloth, $3.00 net.
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DEDICATED
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PREFACE
This book has a twofold purpose. It is intended primarily to serve as a guide to the water analyst and the water-works engineer, describing the methods of microscopical examina- tion, assisting in the identification of the common microscopic organisms found in drinking water and interpreting the results in the light of environmental studies. Its second purpose is to stimulate a greater interest in the study of microscopic aquatic life and general limnology from the practical and economic standpoint.
The work is elementary in character. Principles are stated and briefly illustrated, but no attempt is made to present even a sununary of the great mass of data that has accumulated upon the subject during the last decade. The illustrations have been drawn largely from biological researches made at the laboratory of the Boston Water Works and from the reports of the Massachusetts State Board of Health. In considering them one should remember that the environmental conditions of the Massachusetts water-supplies are not universal, and that every water-supply must be studied from the standpoint of its own surroundings. As far as the microscopic organisms are concerned, however, the troubles that they have caused in Massachusetts may be considered as typical of those experienced elsewhere.
The descriptions of the organisms in Part II are necessarily brief and limited in number. The organisms chosen for descrip- tion are those that are most common in the water-supplies of New England, and those that best illustrate the most important groups of microscopic animals and plants. In many cases whole
vu
viii PREFACE
families and even orders have been omitted, and some readers will doubtless look in vain for organisms that to them seem important. The omissions have been made advisedly and with the purpose of bringing the field of microscopic aquatic life within the scope of a practical and elementary survey. For the same reason the descriptions stop at the genus and no attempt has been made to describe species and varieties. Notwithstand- ing this it is believed that the illustrations and descriptions are complete enough to enable the general reader to obtain a true conception of the nature of the microscopic life in drinking water and to appreciate its practical importance. To the student they must serve as a skeleton outline upon which to base more detailed study.
The illustrations, for the greater part, have been drawn from living specimens or from photo-micrographs of living specimens, but some of them have been reproduced from pub- lished works of standard authority. Among these may be mentioned: Pelletan and W0II6 on the Diatomaceae; W0II6, Rabenhorst, and Cooke on the ChlorophycetT and Cyanophyceae; Zopf on the Fungi; Leidy, Biitschli, and Kent on the Protozoa; Hudson and Goss on the Rotifera; Baird and Herrick on the Crustacea; Lankester on the Bryozoa; Potts on the Spongidaj; and Griffith and Henry on miscellaneous organisms.
This book has been prepared during the leisure moments of a busy year. Its completion has been made possible by the kind assistance of my present and former associates in the laboratories of the Boston and Brooklyn water-supply depart- ments and of other esteemed friends, to all of whom I tender my sincere thanks. I desire also to acknowledge the valuable assistance of my wife, Mary R. Whipple, in revising the manu- script and correcting the proof. To many others I am indebted indirectly, and among them I cannot refrain from mentioning the names of Prof. W. T. Sedgwick of the Massachusetts Institute of Technology; Mr. Geo. W. Rafter, C.E., of Rochester, N. Y.; and Mr. Desmond FitzGerald, C.E., formerly Super- intendent of the Boston Water Works and now Engineer of the Sudbury Department of the Metropolitan Water Works. To
PREFACE iz
Prof. Sedgwick and Mr. Rafter water analysts are indebted for the most satisfactory practical method of microscopical examina- tion of drinking water yet devised, and Mr. FitzGerald will be remembered not only as an eminent engineer but as the foimder and patron of the first municipal laboratory for biological water-analysis in this country.
George Chandler Whipple.
New York, January, 1899.
PREFACE TO THE THIRD EDITION
In reviewing the scientific literature incident to the prepara- tion of this third edition of the Microscopy of Drinking Water, the author has been amazed at the enormous amoimt of work that has been devoted to the study of the microscopic organisms, both in this country and abroad, since he first became interested in the subject more than twenty years ago. But with all the work that has been done, the mystery of the comings and goings of the algae and the protozoa in our lakes and reservoirs still remains unsolved. Yet it cannot be said that no progress has been made, for our studies have at least made clearer some of the laws which control the circulation of water in lakes, the effect which this circulation, or the absence of it, has upon the dissolved gases, and the relation which exists between such gases as oxygen and carbonic acid and the presence of microscopic chlorophyllaceous plants. We have, too, a better idea of the effect which the seasonal changes in the viscosity of water have upon the distribution and even upon the shape of some of the plankton.
If, leaving the natural history of the subject, we turn our attention to its practical aspect and consider the artificial means of controlling plankton growths and the purification of water containing them, we find that gratifjdng progress has been made. The copper sulphate treatment has proved to be conspicuously successful as a means of eradicating algaj. The free use of aeration has been demonstrated to be beneficial in the removal of tastes and odors from algaj-laden water and necessary to its successful filtration. The stripping of soil from reservoir sites has been found to reduce growths of algaj,
zi
xii PREFACE TO THE THIRD EDITION
but not to prevent them entirely. The important part played by the plankton in the self -purification of polluted waters has been established. All of these matters are of great practical importance to the human race.
The Sedgwick-Rafter method has become almost imiversally used by American water analysts. The principal modifications here suggested relate to its more convenient use in the field. The sling filter affords a rapid and satisfactory means of con- centrating the organisms, while the round cell is much cheaper than the original rectangular form. The cotton filter is another useful inovation.
The first part of the book has been rewritten. New mate- rial has been inserted in almost every chapter and several new chapters have been added, the most important being on the copper treatment, the stripping of reservoir sites, the purifica- tion of algae-laden water, and the use of the microscope and photomicrography. The last named chapter was written by Dr. John W. M. Bunker, Instructor in Sanitary Analysis in Harvard University. In this chapter free use has been made of Edward Bausch's excellent little hand-book on the ^^ Use of the Microscope," with the kind permission of the Bausch & Lamb Optical Company. The data on soil stripping have been taken largely from the report made by Messrs. Allen Hazen and George W. Fuller to the chief engineer of the Board of Water Supply of New York City.
The plates showing the common organisms found in water- supplies have been printed in colors, thus making the identifica- tion of the organisms somewhat easier. For this color work the author is again indebted to Dr. Bunker. It is a matter of regret that a larger number of organisms could not have been depicted and described, but this could not have been done without unduly increasing the cost of the book.
The bibliography which occupied more than twenty pages in the preceding editions has been abridged. To have brought it up to date would have required at least a hundred pages. A few references chosen with regard to their value to students, are given at the end of some of the chapters.
PREFACE TO THE THIRD EDITION xiii
m
In bringing this preface to a close the author wishes to express his conviction that the micrology of water is going to play an increasingly important part in the science of sanitation. The demand for clean water is growing. Popular standards of purity are rising. Our cities need water of such quality that the people not only can drink it with safety, but will drink it with pleasure. " Safety first " is as good a motto for the water-supply service as it is for railroad service, but safe water that is not also clean loses, psychologically, much of its value.
In the interest of clean water it is hoped that the study of the microscopic organisms will not be confined to specialists, but will be undertaken by all superintendents of water-works, who are in charge of storage reservoirs. It is for such men and for students of water analysis that this book has been especially prepared. G. C. W.
Cambridge, Mass., January i, 1914.
CONTENTS
PART I
CHAPTER I
PAGB
Historical i
CHAPTER n The Object of the Microscopical Examination 8
CHAPTER m Collection of Samples 14
CHAPTER IV Methods of Microscopical Examination 28
CHAPTER V The Microscope and its Use. Photomicrography 49
CHAPTER VI Microscopic Organisms in Water from Different Sources 73
CHAPTER VII Limnology 83
CHAPTER Vin Dissolved Gases and their Relations to the Microscopic Organisms. 117
XV
xvi CONTENTS
CHAPTER IX
PAGI OCCURKENCE OF MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 1 33
CHAPTER X Seasonal Distribution ov Microscopic Organisms 164
CHAPTER XI Horizontal and Vertical Distribution of Microscopic Organisms 175
CHAPTER Xn Odors in Water-supplies 186
CHAPTER Xm Storage of Surface Waters ao6
CHAPTER XIV Soil Stripping 218
CHAPTER XV Storage of Ground Water 246
CHAPTER XVI Copper Treatment for Algae 351
CHAPTER XVn Purification of Water Containing Algae 261
CHAPTER XVm Growth of Organisms in Water Pipes 277
CONTENTS xvii
PART n
CHAPTER XIX
PAGE
Classification of the Microscopic Organisms 286
CHAPTER XX
DlATOlCACEAE jgi
CHAPTER XXI ScmzouYCBTES. The Iron Bacteria 312
CHAPTER XXII . Cyanophyceae 316
CHAPTER XXm Chlorophyceae 325
CHAPTER XXIV Fungi 341
«
CHAPTER XXV Protozoa 344
CHAPTER XXVI
ROTIFERA 365
CHAPTER XXVII Crustacea 373
CHAPTER XXVni Bryozoa, or Polyzoa 378
xviii CONTENTS
CHAPTER XXIX
PAGi:
Spongidae 381
CHAPTER XXX Miscellaneous Organisms 384
Glossary 387
Tables and Formulae 391
SaENTiFic Literature 303
Index 401
LIST OF ILLUSTRATIONS
Aerator at the Springfield Filter Frontispiece
No. PAGB
1. Whipple's Apparatus for Collecting Samples 15
2. Steuer's Sample Collecting Rig 16
3. Steuer*s Stopper Attachment 17
4. Eurich's Stopper 18
5. Eurich*s Stopper with cap on 19
6. Eurich's Stopper with cap off 19
7. Strainer Jar 20
8. Plankton Net 21
9. Plankton Pump 24
10. Bottle for Collecting Dissolved Oxygen Samples 26
11. Sedgwick-Rafter Funnel 29
1 2. Battery of Filters 30
13. Revolving Stand for Filters 31
14. Sling Filter 33
15. Concentrating Attachment 34
16. Counting Cell 35
17. New Form of Counting Cell 35
18. Ocular Micrometer 36
iQ. Wizard Sediment Tester 47
20. Air Compressor for Sediment Tester 48
21. Compound Microscope Stand 50
22. Optics of Simple Magnification 57
23. Optics of Compound Microscope 58
24. Use of Plane and Concave Mirrors 59
25. Use of the Condenser 60
26. Use of Plane and Concave Mirrors with Condensers 60
27. Leitz Step Micrometer 64
28. Abb6 Camera Lucida 65
29. Photomicrogfaphic Camera 66
30. Edinger Drawing and Projecting Apparatus 67
31 . Demonstration Eye-piece 68
xix
XX LIST OF ILLUSTRATIONS
No. PAGE
32. Microscope for Water Examination 69
33. Portable Microscope 70
34. Field Work at Squam Lake 71
35. Weighte^i Thermometer Case 86
36. Thermophone 88
37. Temperatures at Lake Cmhituate 00
38. Temperatures in Frozen I^kes q 5
39. Temperature of Lake Cochituate in Summer 05
40. Temperatures at Squam Lake gf)
41. Temperatures at Squam Lake (,7
42. Cross-section of Lake, showing Transition Zone 08
43. Classihcation of Likes according to Temfveraturc gg
44. Classification of Lakes according to Temperature 100
45. Horizontal Currents in a I^ke 105
46. U. S. Geological Sur\'ey Color Apparatus 108
47. U. S. Geological Survey Turbidity RcxI 112
48. Disk for Comparing Transparencic*s of Waters 115
49. Dissolved Oxygen and Carbonic Acid in Frt»sh Pond up
50. Dissolved Oxygen in Lake Mendota 1,^0
51. Organisms in Genesee River i()i
52. Seasonal Distribution of Organisms in Lake Cochituate i()4
53. Succession of Diatoms in Chestnut Hill Reser\'oir 106
54. Growth of Diatoms and Intensity of Light 107
55. Seasonal Distribution of Diatoms and Blue (ireen Algie 1 74
56. Hyalodaphnia, changes in shape 1S2
57. Anunea, changes in shape 182
58. Vertical Distribution of Organisms 183
59. Aesthetic Deficiency of Water 202
60. Stagnation Effects, Lake Cochituate 212
61. Organisms in Baiseleys Pond 21b
62. Aeration at Sodom Dam 204
63. Spillway at Croton Dam 266
64. Aeration at Albany, N. Y 20()
65. Sprinkling Fitters at Baltimore 267
66. Aeration at Ludlow Filters, Springfield 267
67. Aerator at Rye Pond 268
68. Aerator at Rye Pond 268
69. Newcomb Filter 275
70. Temperature of Water in Pipes 277
71. Organisms in Boston Water Pipes 279
72. Construction of Diatom Cell 295
73. Iron Bacteria 314
LIST OF ILLUSTRATIONS xxi
PLATES IS TEXT
No. PAGB
A. Sediment in Cambridge Water opposite 48
B. Photo-micrographs of Organisms 298
C. Photo-micrographs of Organisms. 317
D. Photo-micrographs of Organisms 326
E. Photo-micrographs of Organisms 335
F. Photo-micrographs of Organisms 346
PLATES AT END OF VOLUME
I. Diatomaceae.
II. Dtiaomaceae.
in. Diatomacese.
IV. Schizomycetes. Cyanophyceae. V. Cyanophyceae. Chlorophyceae. VI. Chlorophyceae. VII. Chlorophyceae. VIII. Chlorophyceae. IX. Chlorophyceae. X. Chlorophyceae. Fungi. XI. Fungi. Protozoa. XII. Protozoa.
XIII. Protozoa.
XIV. Pro tozoa.
XV. Protozoa. Rotifera.
XVI. Rotifera.
XVII. Rotifera. Crustacea.
XVIII. Crustacea. Bryozoa. Spongidse.
XIX. Miscellaneous.
THE
MICROSCOPY OF DRINKING WATER
PART I
CHAPTER I HISTORICAL
The study of the microscopic organisms in water dates back to the seventeenth century. With the invention of the com- pound microscope enthusiastic observers began to search ponds and streams and ditches for new and varied kinds of microscopic life. Among the pioneers in this field of Natural History were Hooke, 1665; Leeuwenhoek, 1675; Ray, 1724; Hudson, 1762; Muller, 1773; Dillwyn, 1809; Kiitzing, 1834; Ehrenberg, 1836; Dujardin, 1841; and Stein, 1849.
It was not until 1850 that the study of the organisms in drinking water was recognized as having a pra.ctical sanitary value. Dr. Hassall of London was the first to call attention to it. His method of procedure is unknown, but in all proba- bility it consisted of the examination of a few drops of the sediment collected in a deep vessel after allowing the water to stand for a longer or shorter interval. Radlkofer, 1865, of Munich, and Cohn, 1870, Hirt, 1879 ^^^ Hulwa of Breslau, pursued the study and emphasized its importance, but they made no radical improvement in the method.
2 THE MICROSCOPY OF DRINKING WATER
In 1875 ^r. J. D. Macdonald, of London, suggested improve- ments in the sedimentation method, and made a rude attempt to obtain quantitative results by allowing the water to settle for a definite length of time, collecting the sediment on a removable glass disk or watch-glass at the bottom of a tall jar, and afterward transferring this glass disk with its accumulated sediment to the stage of the microscope for direct examination.
In 1884 Dr. H. C. Sorby, of England, attempted to obtain a more exact enumeration by passing a gallon of the sample through a fine sieve (200 meshes to an inch) and then washing the collected organisms into a dish and in some way counting them.
In America important researches were made by Torrey, Vorce, Mills, Leeds, Potts, Nichols, Farlow, and others, but previous to 1888 the work was chiefly of a qualitative character.
American Investigations. In 1887 the Massachusetts State Board of Health began a systematic examination of all the water-supplies of the State, which has been maintained for twenty-five years. Two years later the State Board of Health of Connecticut began a similar but less extensive series of examinations. In 1889 the Water Board of the City of Boston established a biological laboratory at the Chestnut Hill reservoir for the purpose of studying systematically the biological char- acter of the various sources of supply. For the first eight years of its existence it was conducted by the author under the general direction of Mr. Desmond FitzGerald, Superintendent of the Western Division of the Boston Water Works. Subsequent biologists in charge of this laboratory have been Dr. F. S. Hollis, Horatio N. Parker, Edward P. Walters, A. W. Walker and Charles E. Livermore. After the water-supply of Boston came under the control of the Metropolitan Water Board this laboratory was removed to No. i Ashburton Place where it is still in operation.
In 1893 a small laboratory was established by the Public Water Board of the City of Lynn, Mass. In 1897 Mt. Prospect Laboratory, connected with the Department of Water Supply of Brooklyn, N. Y., was equipped and put in operation. It was
HISTORICAL 3
devoted to general water-analysis, and the microscopical examina- tion of water from the different sources of supply formed an important part of the routine work. After Brooklyn became a part of Greater New York, in 1898, the work of this laboratory was extended to cover all the water-supplies of the city, and branch laboratories were established on the Croton and Ridge- wood watersheds. From 1897 to 1904 these laboratories were under the direction of the author; from 1904 to 191 3 under the direction of D. D. Jackson, and now are in charge of Dr. Frank
E. Hale.
Similar biological work has since been imdertaken by boards of health and water departments and by sanitary experts in all parts of the world.
The method of microscopical examination first used by the Massachusetts State Board of Health was that suggested by Prof. G. H. Parker, now of Harvard University. A piece of cotton cloth was tied firmly over the end of a glass funnel and 200 c.c. of the sample were made to pass through it. The organsims were left as a deposit on the cloth. After this strain- ing the cloth was removed and inverted over an ordinary micro- scopical slip. The organisms, together with a small quantity of water, were dislodged upon the slip by blowing downward upon the cloth through a piece of glass tube. This method was useful, but it did not give accurate quantitative results. Mr.
F. F. Forbes, of Brookline, Mass., used a modification of the cloth method. The water was filtered as in Parker's method, but the neck of the funnel passed into a tank from which the air was exhausted by an aspirator. This hastened the filtration and allowed a larger amount of water to be filtered.
The present method of examination was foreshadowed in the work of Mr. A. L. Kean. He filtered 100 c.c. of his samples through a small quantity of coarse sand placed at the bottom of a glass funnel and supported by a plug of wire gauze. After filtration the plug was removed and the sand with its contained organisms was washed into a watch-glass with i c.c. of water. This was stirred up to separate the organisms from the sand and a portion was transferred to a cell holding one cubic milli-
4 THE MICROSCOPY OF DRINKING WATER
meter. From the number of organisms found in this cell the approximate number originally present in the water could be obtained. This method became known as the " sand method."
In 1889 Prof. W. T. Sedgwick, of the Massachusetts Institute of Technology, and Mr. Geo. W. Rafter, of Rochester, made valuable improvements upon Kean's original idea. Prof. Sedgwick suggested the use of a cell much larger than that used by Kean, bounded by a brass rim and having an area of 1000 square millimeters ruled by a dividing engine into 1000 squares. The filtration was made as before, and the sand was washed into the cell with one or two cubic centimeters of water and distributed over the bottom. The cell was then placed under the microscope and the organisms counted in a certain number of the small squares. From this count the number of organisms present in the sample was estimated. A modification of this method was the one first used by the Connecticut State Board of Health. In the Connecticut method precipitated silica was used instead of sand for the filtering medium, and this was sup- ported upon a plug of absorbent cotton.
Mr. Rafter's improvements consisted in the substitution of a ruled square in the ocular of the microscope for the ruling upon the plate, in the separation of the sand from the organisms by decantation, in the use of a cell covered by a cover-glass and containing just one cubic centimeter, and in the use of a specially constructed mechanical stage. The Sedgwick-Rafter method has been modified somewhat by recent experimenters, but its essential character has not been changed.
Dr. Gary N. Calkins substituted a perforated rubber stopper capped by a circle of bolting-cloth in place of the plug of wire gauze. Mr. D. D. Jackson suggested a cylindrical funnel in place of the ordinarj' flaring chemical funnel, and added an attachment at the lower end to control the concentration and prevent the sand from becoming dry. The author has graduated the funnels, designed a simple automatic concentrating device, applied an aspirator to hasten the filtration and devised the portable sling filter for field work. He also designed the ocular micrometer and the record blank now used, and suggested the
HISTORICAL 5
idea of a standard unit of size for estimating the organisms and amorphous matter. Dr. J. W. M. Bunker has devised a convenient stand for the filters and a cheap circular cell.
European Plankton Studies. — While sanitarians were pursu- ing the study of the microscopic organisms because of their effect on the quality of water-supplies, other scientists have approached the subject from an entirely different standpoint. In 1887, the same year in which the Massachusetts State Board of Health began its examination of the water-supplies of the State, Victor Hensen of the University of Kiel, Germany, published a descrip- tion of a new method of studying the minute floating organisms found in lakes. To these organisms he gave the name " plank- ton," from the Greek word plank tos, which means " wander- ing." This collective word was applied to all of the minute animals and plants that float free in the water and that are drifted about by waves and currents. Plants attached to the shore, and animals that possess strong powers of locomotion, were not included in the plankton, but fragments of shore plants, fish-eggs, young fish-fry, and the like, were included. The term may be said to be practically synonymous with the term " microscopic organisms " of the sanitary biologist.
Hensen's method was radically different from the Sedgwick- Rafter method. It consisted of a net by which the organisms could be concentrated in the field, so that only the collected material need be taken to the laboratory. The plankton net has been much improved in recent years.
Even before the publication of Hensen's paper, saentists on the Continent had become interested in the study of lakes. The work of Prof. F. A. Forel, of Morges, Switzerland, on Lake Geneva described in " Le Leman " was epoch making. It was followed by the establishment of a Linmological Conmiission in Switzerland, imder the direction of which many valuable lines of physical and biological research were undertaken. This was followed in 1890 by an International Conunission. From this time increased attention has been given to the biology of ponds and lakes. A biological station was established by Zacharias .at Lake Plon in 1891, and a group of scientists
6 THE MICROSCOPY OF DRINKING WATER
have contributed a long series of important articles to its reports which have been published annually since 1893. Apstein at Kiel, Schroeter at Zurich, Wesenburg-Lund in Denmark and many others have made extensive and valuable observations. Biological stations have multiplied during recent years, and the work has extended to France, Italy, Austria, Denmark, Norway, Scotland and other coimtries.
Special attention should be called to the work of Sir John Murray and his associates in Scotland. The results of their studies are embodied in a recently published work, entitled " Bathymetrical Studies of the Scottish Lakes." The European writings on the subject are now very voluminous. Abstracts of most of the important articles may be found in the " International Revue der Gesammten Hydrobiologie und Hydrographie," a monthly journal edited by R. Woltereck and published by Dr. Werner Klinkhardt at Leipzig.*
Another very valuable source of information is the laboratory of the Koniglichen Landesanstalt fiir Wasserhygiene in Berlin- Dahlem. The " Mitteilungen " published imder the direction of Dr. Rudolf Abel and Dr. Carl Gunther contain many articles relating to limnology and the micrology of water.
Plankton Studies in the United States. — Similar investiga- tions have been carried on in the United States. In 1893 Prof- J. E. Reighard, acting \mder the direction of the Michigan Fish Commission, made a biological study of Lake St. Clair. This was followed by an examination of Lake Michigan by Prof. Henry B. Ward, and by studies of the Crustacea in Lake Men- dota by Prof. E. A. Birge, and in Green Lake by Prof. C. Dwight Marsh.
Biological stations were soon established by a number of western universities on or in the vicinity of the Great Lakes, and on the shores of smaller bodies of water.
Summer-school courses in planktology and general micro- scopic ecology are given at these stations. In 1900 an American Limnological Commission composed of Dr. E. A. Birge, Dr. H.
* This can be obtained from G. £. Stechert & Co. 129 West 30th St., New York City.
HISTORICAL 7
B. Ward, Dr. Charles A. Kofoid, Dr. C. H. Eigenmen, and George C. Whipple, was organized for the purpose of stimulat- ing scientific work along the various lines of natural science involved, and of co-ordinating the work of various individuals and institutions.
This commission, not receiving proper support, was discon- tinued, but its work resulted in increased individual activity. Dr. Kofoid carried on an extensive investigation of the plankton of the Illinois River, and Dr. Birge and Dr. Juday have made most valuable studies of the temperature of lakes and the gases dissolved in lake waters at different depths.
For several years the late Prof. James I. Peck, acting under the direction of the U. S. Fish Commission, made important studies of the food of certain fishes, notably the menhaden. He used the Sedgwick-Rafter method instead of the plankton net for concentrating the microscopic organisms. This method has also been used in the study of the food supply of oysters.
In 1896 Dr. C. S. DoIIey, of Philadelphia, suggested the use of the centrifugal machine for the purpose of concentrating the microscopic organisms. This " planktonokrit," as it is called, has not been developed to completeness, but was studied by Field, Kofoid, and others.
Prof. H. B. Ward and Mr. Chas. Fordyce devised a plankton pump for collecting Crustacea and other plankton organisms at particular depths below the surface of a lake. In many ways this was a decided improvement over the plankton net.
These special methods have more value for strictly scientific studies of the organisms than for the practical uses of the water analyst or the sanitary expert.
The extensive investigations of the Massachusetts State Board of Health and the Metropolitan Water Board of Boston begim nearly a quarter of a century ago are still being continued, as well as those of the water dei>artment of New York City.
Important advances have also been made in the direction of controlling the growths of alga^ in reservoirs and the purifica- tion of water containing microscopic organisms.
CHAPTER II THE OBJECT OF THE MICROSCOPICAL EXAMINATION
A COMPLETE sanitary examination of water, as conducted in modem laboratories, consists of four parts — the physical, the microscopical, the bacteriological, and the chemical analysis. For a description of the methods of analysis the reader is referred to the Report of the Committee on Standard Methods of Water Analysis of the American Public Health Association, Revised in 191 2.* The data commonly obtained by these analyses are as follows:
Physical Examination.
Temperature — Turbidity — Color — Odor (both cold and hot). Microscopical Examination.
Quantity of microscopic organisms per c.c. — ^Amount of inorganic matter, amorphous matter, etc. Bacteriological Examination.
Number of bacteria per c.c. — Presence of B. coli and other intestinal bacteria associated with pollution. Chemical Ex.\mination.
Total Residue on Evaporation — Loss on Ignition — Fixed Solids — Alkalinity — Hardness — Incrustants — Chlorine —Iron— Nitrogen as Albuminoid Ammonia— Nitrogen as Free Ammonia — Nitrogen as Nitrites — Nitrogen as Nitrates — Total Organic Nitrogen (Kjeldahl Method) — Oxygen Consumed — Dissolved Oxygen — Free Carbonic Acid. (Some of these are of use only in special cases.)
* Copies of this report may be obtained from the Secretary of the Association, 289 Fourth Ave., New York City.
8
THE OBJECT OF THE MICROSCOPICAL EXAMINATION 9
Such an analysis is intended to show whether the water is of such a character that it would be liable to cause sickness if used for drinking; whether it contains any- thing that would render it distasteful or unpalatable; and whether it contains ingredients that would make it unfit for laundry use or for general domestic or industrial purposes. Analyses are necessary also, and perhaps have their chief use, in studying the effect of processes of purification of water and sewage.
Opinions regarding the function and value of sanitary water- analyses have undergone a change in recent years. The nu- merical results of a single analysis of a sample of water, when considered by themselves, are now believed to have little intrinsic value. It has been found that the value of the analysis lies in its interpretation, and that each part of the analysis must be interpreted by comparison with all the other parts and in the light of exact knowledge of the environment of the water. The interpretation of aji analysis is as much a matter of expert skill as is the making of the analysis itself. The physical, biological, and chemical examinations should be interlocking in their testimony, yet these different parts are to be given different weight in the study of different problems. For example, in the detection of pollution the chemical and bacterial examinations furnish the most information, in the study of the aesthetic qualities of a water the physical and microscopical examinations are most important, while in inves- tigations concerning the value of a water for industrial piuposes the chemical and physical examinations may alone suffice.
The biological examination is concerned with the micro- organisms found in water. The term " micro-organisms," when used in its broadest and most literal significance, includes all organisms which are invisible or barely visible to the naked eye. It is frequently used in a narrower sense, however, as a synonym for bacteria. Using the word in its broad sense we may divide the micro-organisms found in water into two classes, as suggested by Professor Sedgwick.
10
THE MICROSCOPY OF DRINKING WATER
MlOtO-ORGANISMS.
Organisms, either plants or animals, invisible or barely visible to the naked eye.
Microscopic Organisms. {Plankton,)
Not requiring special culture. Easily studied with the microscope. Microscopic in size, or slightly larger. Plants or animals.
Bacterial Organisms,*
Requiring special cultures. Difficultly studied with the microscope. Microscopic or sub-microscopic in size. Plants.
This subdivision is convenient for the sanitarian as well as for the biologist, because the two classes of organisms affect water in different ways. With certain reservations it may be said that bacteria make a water unsafe, microscopic organisms make it unsavory.
Microscopical Examination.~The microscopical examina- tion of water may be considered in five aspects: i. As indicating sewage contamination. 2. As indicating the progress of the self -purification of streams. 3. As explaining the chemical analysis. 4. As explaining the cause of turbidity, odors, etc., in water. 5. As a means of identifying the source of a water (in special cases). 6. As a method of studying the food of fishes, oysters and other aquatic organisms.
Sewage Pollution. — The microscopical examination cannot be depended upon to determine the pathogenic qualities of a drinking water. To be sure, the germs of disease are micro- scopic bodies, and when artificially cultivated or when found in the tissues of the body can be studied with microscopes of high power; but when scattered through a mass of water they can- not be detected by ordinary microscopical methods, on account of their small size and because they are greatly outnumbered by the ordinary water bacteria. It is not easy to discover them even by methods of culture. Not only may water contain pathogenic bacteria without discovery, but it may contain the ova or larvae of some of the endoparasites of man. It is probable
* The bacteria are not considered in this volume. The reader is referred to the numerous works on Bacteriology, and especially to Prescott and Winslow's ** Elements of Water Bacteriology."
THE OBJECT OF THE MICROSCOPICAL EXAMINATION 11
that endoparasitic diseases are more common than has been generally supposed; and while diseased pork, beef, etc., are the chief agencies of infection, it is known that water polluted by animal excrement may contain the ova or larvae of such endoparasites as Tcmia soliuniy Tcmia saginata, Botrioce- phalusplatuSj Ascaris lumbricoideSy Trichocephalus dispar, and Afichylostomum duodenale. Infection of animals by the drink- ing of water contaminated by barnyard wastes has been several times recorded, while a microscopical examination of the water has seldom revealed the presence of the suspected ova or larvae. This is not because they are too minute to be detected, but because the quantity of water examined is necessarily too small.
The microscopical examination cannot show definitely whether a water is polluted by sewage unless the pollution is excessive. It can, however, give evidence which, taken with the chemical and bacterial examinations, may establish the proof. A microscopical examination of sewage reveals few of the li\dng organisms that are found ordinarily in water. Ciliated infusoria, such as Paramaecium and Trachelocerca; fungus forms, such as mold hjphae, Saprolegnia Leptomitus, Leptothrix, and Beggiatoa; and miscellaneous objects, such as yeast-cells, starch-grains, fibres of wood and paper, fibres of muscle, epithelial cells, threads of silk, woolen, cotton and linen, insect scales, feather barbs, etc.,m{iy be observed. Most of these objects are foreign to unpolluted water, and their presence in a sample of water leads one to suspect its purity.
Furthermore, there are other organisms, such as Euglena viridiSy which live on decaying vegetable matter and which, though not found in sewage, are often associated with it in polluted water. Their presence in a sample is a cause of sus- picion. These evidences, however, should be weighed only in connection with an environmental study and with the entire sanitary analysis. The common microscopic organisms found in water are not themselves the cause of disease, nor does their presence indicate sewage pollution.
Self-ptirification of Streams. — The progress of the self- purification of streams may also be studied by noting the changes
12 THE MICROSCOPY OF DRINKING WATER
in the character of the microscopic organisms. That a proper balance must be maintained between different groups of organisms in order that condition of fouhiess may not follow seems to be one of the results of recent investigations.
Interpretation of Chemical Analysis.- The chemical exam- ination determines the amount of organic matter that a sample of water contains, but it does not determine the nature of it. As the character and condition of the organic matter are very important from the sanitary point of view, the microscopical examination gives valuable information by showing not only whether the organic matter in suspension is vegetable or animal, but by determining whether it is made up of living organisms or of decomposing fragments. For example, the amount of albuminoid ammonia in suspension is sometimes so great that one might suspect that the water was polluted did the microscope not show that the high figure was due to a growth of some organ- ism; or in a series of samples from a reserv^oir it might be dif- ficult to accoimt for a sudden decrease in the nitrates or free ammonia were it not for the appearance of some microscopic organism that had appropriated the nitrogen as a part of its food.
Cause of Odors. — Perhaps the most important service that the microscopical examination renders is that of explaining the cause of the taste and odor of a water and of its color, turbidity, and sediment. Several of the common microscopic organisms give rise to objectionable odors in water and, when sufiiciently abundant, have a marked influence on its color. They also make the water turbid and cause unsightly scums and sediments to form. Upon all such matters related to the aesthetic qualities of a water the microscopical examination is almost the only means of obtaining reliable information.
Origin of Waters. — ^The presence of certain microscopic organisms in water sometimes gives a clue to its origin. In this way the presence of surface-water in a well may be detected. In the Chicago Drainage Canal case the presence of Lake Michigan water in the St. Louis water-supply was indicated by finding in it a certain diatom characteristic of the Lake Michigan water.
THE OBJECT OF THE MICROSCOPICAL EXAMINATION 13
Food Supply of Fish Life. — The microscopic organisms form the basis of the food-supply of fish and other aquatic animals. Sometimes the relation is a direct one; that is, the microscopic organisms are themselves eaten by fish. This was well illustrated by Peck in his study of the menhaden. This fish when feeding swims with its mouth open. The water enters the mouth and passes out through the gills which act as a filtering apparatus by which the minute organisms are caught. It was found that the presence or absence of these fish from certain sections of the Massachusetts coast depended upon the abundance of microscopic life in the water, and also that the weight of fish of any particular length depended upon the quan- tity of this food material at hand. Forbes has simwned up the relation by saying, " No plankton, no fish."
The relationship between the plankton and fish life is not always so direct. In many cases the fish feed upon Crustacea and insect larv^ae; the Crustacea feed upon the rotifera and protozoa; the rotifera and protozoa feed upon algae and bac- teria; while the algae nourish themselves by the absorption of soluble inorganic substances and gases provided in part by the decomposition of animal and vegetable matter brought about by bacteria.
Oysters feed largely upon diatoms, and the Sedgwick-Rafter method has proved very useful in the study of this problem in the Great South Bay, Long Island, and elsewhere.
Ecology. — The interrelations between different organisms of the lower world, and between the organisms and their environ- ment are matters of intense s.cientific interest, and limnology and microscopical ecology are fast assuming important places in scientific literature. The physical condition of lakes, the currents, waves, temperature, and transparency of water, the chemistry of water, the life-history of organisms, and various bio-chemical and bio-physical problems are more and more attracting the attention of scientists and of water-works engineers.
CHAPTER in
COLLECTION OF SAMPLES
It cannot be too strongly emphasized that samples of water for analysis must be collected with great care. When- ever possible the analyst himself should supervise the collec- tion. If he attemps to draw inferences from analyses of samples of water about the collection of which he knows nothing he does so at the risk of his reputation.
The quantity of water required for a microscopical examina- tion depends upon the nature of the water. Usually one quart is sufficient, but a gallon is to be preferred and this amount is necessary when a chemical analysis also is to be made. Glass- stoppered bottles should be used, and they should be scrupu- lously clean. When sent by express they should be packed in covered boxes that have compartments lined with suitable packing-paper to prevent breaking. In winter it may be necessary to use a felt lining to prevent freezing.
Sample Collecting. — In collecting a sample of water from a service-tap the water should be allowed to run for several minutes before the bottle is filled and the bottle should be rinsed several times before the final filling. The bottle should not be filled completely, but a small air-space should be left for expan- sion. If the sample be from a stream care must be taken not to stir up the deposit on the bottom, or to allow floating masses of vegetable matter to enter the bottle. This may be sometimes prevented by pointing the mouth of the bottle down stream. In collecting a sample from a pond good judgment must be used in securing a representative sample. The bottle should be filled in such a way that the surface-scum may not enter. When col- lecting samples from streams or lakes the nature of the littoral
14
COLLECrriON OF SAMPLES
15
growths in the vicinity should be noted. These notes are sometimes of value in the interpretation of an analysis.
Deep Sample Colle.ctoT. — Numerous methods have been sug- gested for collecting samples from depths below the surface. The simplest method con^sts of lowering a weighted stoppered bottle to the desired depth and putting out the stopper by means of a separate cord. When the bottle is full it may be drawn to the surface with little probability that the water will be displaced. An extra precaution to avoid ad- mixture with the upper layers of water may be taken by using a rubber stopper fitted with a glass tube bent at right angles above the stopper and sealed at the end. With this arrangement the water is allowed to enter the bottle by breaking the glass tube by a pull from an auxiliary cord, or an inflated rubber ball may be put into the bottle. When the water enters, the ball will be forced up into the neck of the bottle on the inside and make an effective seal.
Steuer's Rig. — Steuer, in his Planktonkunde has described a con- venient method of lashing a bottle and weight to the end of a rope. This rig is shown in Figs. 2 and 3.
Whipple's Collecting Device.— When collecting samples from depths greater than 50 ft, it is desirable to avoid the use of the auxiliarj' cord. The following apparatus has proved very satisfactory down to depths of 400 ft. (See Fig. i.)
The frame for holding the bottle consists of a brass wire, A, attached to a weight, B, which is made by rolling a sheet of brass so as to form the sides of a shallow pan and filling this with melted lead to the height indicated by the dotted line. At each side where the wire rod is attached a strip of brass
-Apparatus for Collecting Samples of Water. After Whipple.
16
THE MICROSCOPY OF DRINKING WATER
extends upward, terminating in a clip, C. These brass strips have considerable spring and are designed to hold the bottle in place, as shown in the cut. Guides, Z), prevent the strips from being bent too far inward, and the uprights, A, prevent
them from being bent too far outward. The bottle may be inserted easily by hold- ing back the springs, C, and pushmg it between the clips. The frame is supported by the spring, F, joined to the sinking- rope, E. A flexible cord, C, extends from the top of the spring, £, to the stopper, F, of the bottle, /. The length of this cord and the length and stiffness of the spring are so adjusted that when the apparatus is suspended in the water by the sinking- rope the cord will be just a little slack. In this condition it is lowered to the depth at which one wishes to fill the bottle. A sudden jerk given to the rope stretches the spring and produces sufficient tension on the cord, G, to pull out the stopper. As a precaution against a possible loss of the apparatus through breaking of the spring, a safety-cord, not shown in the figure, extends through the helix connect- ing the sinking-rope, £, directly to the frame, /. This safety-cord, which is always somewhat slack, is also adjusted to prevent too great a stretching of the spring.
With great depths it is necessary to reduce the size of the aperture through which the water enters the bottle and to close this with a suitable valve. This may be done by passing a piece of brass tube through a rubber stopper and closing this tube at the top with a brass plug ground to fit; or the spring may be used to break the end of a sealed glass tube inserted in the stopper. A still better
Weight
Fig. 2.— Rig for Bind- ing Bottle to Rope and for Drawing the Stopper.
After Steuer.
COLLECmON OF SAMPLES 17
caethod is that devised by Mr. Richard H. Eurich, while a student of sanitary engineering in Harvard University.
Eurich's Stopper for Water Sampling Bottle. In order to obviate the trouble experienced in drawing the stopper of a bottle against heavy pressure, when collecting a sample of water from a conaderable depth, a balanced valve is used for admitting the water to the bottle.
The valve, or stopper, shown in Fig. 4 is constructed of brass or other suitable non-corroding metal. It is in two pieces, an imier one, A, and an outer one, B. The lower part of A is ground to fit into the neck of the bottle, and the upper part contains the ports through which the water enters. The outer piece is a cylin- drical shell which slips down easily
over the inner piece, just closing the
,1. , . ,. . „ , J Fig- 3— Method of Attaching ports. The releasing hne is attached stopper lo Corf
to the outer piece, so that when the After Steuer.
line is jerked the piece is pulled off,
allowing the water to enter the bottle through the ports. The apparatus is hauled to the surface without any attempt at closing the ports, experience having shown that the entrance of water on the way up is negligible.
Strainer Jars. — For collecting material for qualitative examination strainer jars are useful. They may be made in several ways. A convenient arrangement is that shown in Fig. 7. Bolting-cloth makes the best strainer, but muslin or a linen handkerchief will serve.
Plankton Net Method. — The plankton net originally designed by Hensen, consists of a conical net of silk bolting-cloth sus- pended from an iron ring and terminating at the lower end in a flat metal ring to which is attached the filtering-bucket. The latter consists of a metal frame covered on the sides with bolting- cloth, and having a slightly conical bottom. In the middle of the bottom there is an outlet-tube closed with a removable plug. The bucket is about 2J inches in diameter. It is sup-
18 THE MICROSCOPY OF DRINKING WATER
|
-m\ |
M |
|
B |
|
Fio. 4. — Eurich's Stopper for Water Sampling Buttle.
COLLECTION OF SAMPLES
|
»[4 |
Fic. 5.— Collecting Bottle Showing Stopper with Upper Part in Place. After
;. fi.— CnlterliriK Roltle Showing Stopper with Upper Pan UlT. After Eurich.
20
THE MICROSCOPY OF DRINKING WATER
ported on three legs when detached from the net. The filtermg- net of bolting-cloth is protected by a twine net which helps to bear the strain when the net is drawn through the water. Cords extend from the iron ring to the bucket in order to further relieve the filtering-net from strain. Above the filtering-net there is a truncated canvas cone that serves as a guard, pre- venting the entrance of mud when near the bottom and prevent- ing the contents of the net from spilling over the edge. It is this diameter that determines the volume of water filtered
Fig. 7. — Apparatus for Concentrating Microscopic Organisms.
when the net is drawn through the water. The whole net is suspended by three cords attached to radiating iron arms fastened to the rope by which the apparatus is raised and lowered.
The nets are made of various dimensions. Reighard's net, used in Lake St. Clair was 3 ft. in length, 2 ft. in maximum diameter, with an opening 16 inches in diameter. Birge has used a smaller net and for water-supply investigations the author prefers this to the larger form.
Operation of Plankton Net. — The plankton net is operated as follows: It is lowered to the bottom or to the desired depth
COLLECTION OF SAMPLES
21
and then drawn to the surface, the velocity of its ascent being noted. On the way down it takes in no water except what is filtered through the gauze. On the way up it filters a column of water the cross-section of which is that of the opening of the guard net and the height of which is equal to the distance through
8.— Plantton Xet. After Reighard.
which the net was drawn. This is the theoretical amount filtered. Actually the net does not strain the whole column of water through which it passes, as a portion of the water is forced aside. Therefore in order to obtain the volume of plank- ton in the column traversed it is necessary to multiply the observed result by a factor or coefficient. This net-coefficient
22 THE MICROSCOPY OF DRINKING WATER
varies for each net and for different velocities of ascent through the water. It also varies with the amount of clogging. With velocities of 2 to 3 ft. per second the coefficient is about 2.5. It is necessary to know the coefficient for each net at different velocities and to correct the results of each haul for the par- ticular velocity used. Evidently the results obtained are not of great accuracy.
When the net reaches the surface it is allowed to drain. A stream of water played on the outside of the net detaches the organisms from the bolting-cloth and washes them down into the bucket. The bucket is then detached from the net and its collected material is transferred to a small bottle for transporta- tion to the laboratory.
A plankton net once used by Birge differs from the one just described in that it has a cover instead of a guard-net. The cover slides in a rectangular frame. It is moved by delicately adjusted weights set in action by a releasing device which is operated by messengers sent down the rope. The cover may be opened or closed at any depth at the will of the operator. This enables one to collect material from the lower strata with- out having it contaminated with that above it.
Quantitative Estimation of the Plankton.- -The amount of plankton collected may be determined by four methods: (i) by estimation of the volume; (2) by determination of the weight; (3) by chemical analysis; (4) by enumeration of the organisms.
The volume is obtained by allowing the material to stand in alcohol in a graduated cylinder for 24 hours. At the end of that time the plankton will have settled and the volume in cubic centimeters may be read from the scale. This gives the total volume in one catch. It is customary to express results in " number of cubic centimeters of plankton under one square meter of surface " or in " number of cubic centimeters of plank- ton in one cubic meter of water."
The approximate weight may be determined by drying on filter-paper and weighing. The results are usually expressed in grams of plankton under one square meter of surface or in one cubic meter of water.
COLLECTION OF SAMPLES 23
The chemical analysis of the plankton usually consists of the determination of the percentage of organic material, ash, silica, etc.
The enumeration of the organisms is the most important part of the laboratory investigation. The material is evenly distributed in a definite amount of alcohol by shaking, and a portion is removed to a small trough or cell and placed under the microscope. The various organisms are then counted. Lines drawn on the bottom of the cell aid the observer in cov- ering the entire area of the cell. As in the case of volume and weight, the results are generally expressed either in " number of organisms under one square meter of surface " or in " number of organisms per cubic meter of water." Both these methods are objectionable because so many figures are involved. They often extend to the millions and sometimes to the billions. It is preferable to express the smaller organisms, such as the algae and protozoa, in " number per cubic centimeter," and the larger organisms, such as the Crustacea, rotifera, etc., in " num- ber per liter.''
It is evident that the " plankton net method " involves many sources of error. Neither the amount of water strained nor the completeness of the filtration can be definitely ascer- tained. The loss of the smaller organisms by leakage through the meshes of the silk is very great, and many of the delicate organisms are crushed upon the net. The methods of estimat- ing the volume and weight of the plankton, moreover, are exceedingly inaccurate. The method of enumerating the organisms is much to be preferred. Except in the case of com- paratively large organisms, such as the Rotifera, Crustacea, etc., the results of the net method cannot be depended upon within 50 per cent.
In spite of these inaccuracies, however, the plankton net is deserving of greater use by those interested in the biology of water-supplies. It is a valuable adjunct to the Sedgwick- Rafter method, which because it is applied to small samples is liable to miss the presence of important organisms at depths different from those at which the samples were collected.
24
THE MICROSCOPY OF DRINKING WATER
PlanktoQ Pump.— The plankton pump is designed to collect the plankton from any particular depth in a lake. It consists of a sort of force-pump so arranged that a definite and measurable quantity of water is delivered at each stroke; an adjustable hose through which the water is drawn from the desired depth; and a filtering-bucket into which the water is pumped. The straining is effected by allowing the water to pass through a cylinder of fine wire gauze at the lower end of the filtering-
Flo. 5.— Plankton Pum]>. After Wilhelmi.
bucket. The efficiency of the strainer is increased by cover- ing the wire gauze with fine bolting-cloth.
This method has the advantage of measuring the quantity of water strained with greater accuracy than is possible in the net method, but the error from imperfect filtration is large.
The method is easily applied and is susceptible of a greater accuracy than has usually been obtained. A bicycle pump, with valves changed so as to produce suction, may be used instead of a force-pump. Fig. 9 shows the arrangement of a plankton pump.
This improved form of plankton pump is described by
COLLECTION OF SAMPLES 25
Dr. Julius Wilhelmi in Mitteilungen aus der Koniglichen Landesanstalt fiir Wasserhygiene, Vol. 17, p. 126.
Preservation of Microscopic Organisms. For the technique of killing and preserving microscopic organisms the reader is referred to works on histology, and microscopical technique. The following are a few of the solutions that will be found useful.
The microscopic organisms may be preserved in permanent mounts upon glass slips but for practical study it is more convenient to preserve them in mass in 2-oz. bottles. For this purpose the following killing and preservative fluids may be found useful:
King^s Fluid (for preserving alga?, etc.). —
•
Camphor- water * 50 grams.
Distilled water 50 * *
Glacial acetic acid 0.50 * *
Copper nitrate, crystals o. 20
Copper chloride, crystals o. 20
t (
Corrosive Acetic Acid (for killing). — Saturated solution of mercuric chloride plus 10 per cent of acetic acid. After using, wash with water. Preserve in alcohol.
Formaldehyde. — For killing, use a 40 per cent solution, sold under the name of " Formalin." For preserving, use solutions varying from 5 to 10 per cent, according to the organisms.
Picro-sulphuric Acid (for killing). —
Distilled water saturated with picric acid. . . . 100 c.c. Sulphuric acid, strong 2 c.c.
After using, wash with 60 per cent alcohol.
Corrosive Sublimate (for killing Protozoa). — To water con- taining the organisms add an equal volume of saturated cor- rosive sublimate. Decant, and add 50 per cent alcohol, changing this in an hour to 70 per cent.
* Made by letting a lump of camphor stand in distilled water for a few days.
26
THK MICBOSCXJl'Y OF DRINKING WATER
Collectum of Samples for the Detenninatioii of Dissolved Oxygen. — Many devices have been used for collecting samples of water for the determination of dissolved oxygen. The one shown in Fig. lo, has proved very satisfactory.
The small " dissolved oxygen " bottle b is clamped to the .^de of the cage which holds the large bottle and is connected
Flc. lo.— Botlle for CollectLon of Dissolved Oiygen Samples.
with the large bottle B by the metal tube C which leads from near the top of b to near the bottom of B. The upper end of a small tube A, inside of C, communicates freely with the outside water at a, and its lower end terminates near the bot- tom of 6. A straight tube D leads from the upper part of B up to the outside water.
COLLECTION OF SAMPLES 27
With both bottles B and b empty and the rubber stoppers through which the tubes are inserted firmly in place, the apparatus is lowered rapidly to the desired depth. The action then taking place is as follows : The air in B escapes through D and draws the water in at a, filling b and then drawing water over through C into B. Thus a flow is set up through the small bottle with the result that finally a sample is left in it which has not come in contact with any air, and which, consequently is a proper sample from which to determine the dissolved oxygen in the water. The relative sizes of the two bottles determine the volume of water flowing through the small bottle. In the apparatus here described the small bottle held about 300 c.c.
CHAPTER IV METHODS OF MICROSCOPICAL EXAMINATION
The best method of determining quantitatively the abundance of microscopic life in water is the Sedgwick-Rafter method, to be described in the present chapter. The plankton net is used largely by those who are most interested in the rotifers, Crustacea and the larger forms of organisms. The plankton pump and the planktonokrit, described later, are but little used, although they are capable of development.
The Sedgwick-Rafter Method. — ^The Sedgwick-Rafter method consists of the following processes: the filtration of a measured quantity of the sample through a layer of sand upon which the organisms are detained; the Separation of the organisms from the sand by washing with a small measured quantity of filtered, or distilled, water and decanting; the microscopical examina- tion of a portion of the decanted fluid; the enumeration of the organisms found therein; and the calculation from this of the number of organisms in the sample of water examined. The essential parts of the apparatus are the filter, the decantation- tubes, the cell, and the microscope with an ocular micrometer.
Filtration. — The sand may be supported upon a plug of rolled wire gauze at the bottom of an ordinary glass funnel 7 or 8 inches in diameter, but the cylindrical funnel shown in Fig. II is preferable. The inside diameter of this funnel at the top is 2 inches; the distance from the top to the beginning of the slope is 9 inches; the length of the slope is about 3 inches; the length of the tube of small bore is 2| inches, and its inside diameter is ^ inch. The capacity of the funnel is 500 c.c. The support for the sand consists of a perforated rubber stopper pressed tightly into the stem of the funnel and capped with a
28
METHODS OF MICROSCOPICAL EXAMINATION
29
circle of fine silk bolting-cloth. The circles of bolting-cloth may be cut out with a wad-cutter. Their diameter should be a little less than that of the small end of the rubber stopper. When moist the cloth readily adheres to the stopper. The sand resting upon the platfonn thus prepared should have a depth of at least three-fourths of an inch. The quality of the sand b important but no very definite degree of fine- ness need be sought. Ordinary sand is un- satisfactory unless very thoroughly washed. Pure ground quartz is preferable. Its white- ness is a decided advantage. The necessary degree of fineness of the sand depends somewhat upon the character of the water to be filtered. A sand which will pass through a sieve having 60 meshes to an inch, but which will be retained by a sieve having 120 meshes, will be found satisfactory for most samples. Such a sand is described as a 60-120 sand. When very minute organisms are present a finer sand must be used — say a 60-140 sand. The sand used for many years by the author had an effective size of 0.15 mm.
The filter may be supported on a ring stand. If many are required they may be arranged conveniently in a row against the laboratory wall as shown in Fig. 12, or on a revolving circular frame as in Fig. 13, The filtered water may be collected in a sloping trough and carried to a sink, or jars may be placed under the separate funnels. A hinged covering-shelf above the filters is useful to prevent the access of dust.
The sample to be filtered may be measured in a graduated cylinder or flask, or the filter-fimnel itself may be graduated. The graduated filter-funnel is especially useful for field work,
:i. — Graduated Cylindiical Funnel
Used in the Sedg- wick-Raftei Method.
30
THE MICROSCOPY OF DRINKING WATER
as it saves the necessity of canning an additional graduate. The quantity of water that should be filtered depends upon the number of organisms and the amount of amorphous matter present. An inspection of the sample mil enable one to judge the proper amount. Ordinarilj' looo c.c. for a groimd-water and 500 c.c. for a surface-water will be found satisfactory. In some cases 250 c.c. or even 100 c.c. of a surface-water will be
â– Batteiy of Ftlteis. Sedgwick-Ratter Weihod,
found more convenient. When the water b poured into the funnel care should be taken not to disturb the sand more than 15 necessary, otherwise organisms are liable to be forced through the filter. The best way is to make the sand com- pact by pouring in enough distilled water to just about fill the neck of the funnel, pouring in the measured sample before the sand has become uncovered. The collection of air in the sand may be prevented bj- first putting in a small portion of
METHODS OF MICROSCOPICAL EXAMINATION
31
the sand, and adding a small amount of distilled water into which the rest of the sand is allowed to fall. The filtration otdinarily takes place in about half an hour, but occasionally a sample is so rich In organisms and amorphous matter that the filter becomes clogged. It then becomes necessary to agitate the sand with a glass rod or to apply a suction to hasten the
Fig. 13. — Revolving Stand For Su|iport[ng Filler Funnels. After Bunker.
filtration. If the filters are located near running water an aspira- tor may be attached to the faucet and connected with the filter by a rubber tube having a glass connection that fits the bore of the rubber stopper. The use of the aspirator enables the filtration to be made in a few minutes, and not only effects a sa\Tng in time, but reduces the error caused by the organisms settling on the sloping surface of the funnel.
32 THE MICROSCX)PY OP DRINKING WATER
The Sling Filter. — For using the Sedgwick-Rafter method in the field the sling filter has been found serviceable. This is made of metal instead of glass. Filtration is hastened by swinging the funnel around an axis, thus making it virtually a centrifugal machine. The construction of the sling filter is shown in Fig. 14.
Concentration. — As a result of the filtration the organisms and whatever other suspended matter the sample contained will have been collected on the sand. When all the water has passed through and before the sand has become dry the rubber stopper is removed and the sand with its accumulated organisms is washed down into a wide test-tube by a measured quantity of filtered or distilled water delivered from a pipette. The amount of water used for washing depends upon the number of organsims collected on the sand. If 500 c.c. of the sample is filtered it is usually best to wash the sand with 5 c.c. thus concentrating the organisms one hundred times. The amount of water filtered divided by the amount of water used in wash- ing the sand gives the " degree of concentration.'' The degree of concentration may vary from 10 to 500 according to the contents of the sample. Ordinarily it should be 50 or 100.
By shaking the test-tube the organisms will become detached from the sand-grains. If this is followed by a rapid decanta- tion into a second test-tube most of the organisms, being lighter than the sand, will pass over with the decanted fluid, while the sand is left upon the walls of the first tube. To insure accuracy the sand should be washed a second time and the two decanted portions mixed together. If, for example, it is desired to con- centrate a sample from 500 c.c. to 10 c.c. the sand should be washed twice with 5 c.c. and the two portions poured together. This will give a more accurate result than a single washing with 10 c.c.
To prevent fragile organisms from disintegrating on the sand surface after filtration, when the sand tends to become dry, an attachment may be used as shown in Fig. 15. The glass tube, bent twice at right angles and inserted in the rubber stopper, checks filtration when the level of the water in the funnel
METHODS OF HICBOSCOFICAL EXAMINATION
Flo. 14.— The Sling Filter for Use with the Sedgwick-RafUc Method ia the Field.
34
THE MICROSCOPY OF DEINKINft WATKE
has fallen to that of the open arm of the tube. If the operator is watching the filtration even tliis form of attachment is unneces- sary, as the filtration may be stopped by inserting a plug in the rubber stopper as soon as the level of the water has fallen to the desired point. If fragile organisms are present this method of concentrating b to be preferred to the usual one described above in which the surface of the sand is allowed to become uncovered before the sand is washed into the test-tube. As the use of either form of attachment described above retards the rate of filtration it is better not to put on the attach- ment until the water has fallea almost to the desired level.
If the concentrated water is allowed to stand in the funnel for any length of time some of the organisms are Uable to become attached to the glass sides. To prevent error from this cause the neck of the funnel may be washed with a small measured quantity of filtered water, and this may be caught in the large test-tube and used for washing the sand a second time as described above. This pro- cedure is seldom necessary. The Cell. — The cell into which a measured portion of the concentrated fluid is placed for examination is made by cement- ing a brass rim to an ordinary glass slip. The cell originally used was rectangular. Its internal dimensions were length 50 mm., width 20 mm., and depth i mm. It therefore has an area of 1000 sq. mm. and a capacity of i c.c. A thick cover- glass (No. 3) having dimensions equal to those of the outside of the brass rim (55 mm. by 25 mm.) forms a roof to the cell. The concentrated organisms in the decantation-tube are dis- tributed uniformly through the fluid by blowing into it through a
15. — Conccniraling Attach-
METHODS OF MICROSCOPICAL EXAMINATION
35
pipette, and the cell is then filled with the fluid in such a manner as to distribute the organisms evenly over the entire area. This may be done by laying the cover-glass diagonally over the cell so that an opening is left at either end, and flowing the
Fig. i6. — Counting Cell, Showing Method of Filling.
water in at one end while the air escapes at the other (see Fig. i6).
It is not necessary to use a rectangular cell. A circular cell is equally satisfactory, is much cheaper and is easier cleaned. The capacity of the cell is immaterial, but a volume of about one cubic centimeter is most convenient. It is necessary, however, that the depth be exactly one millimeter. The circular cell is shown in Fig. 17.
The Microscope. — An expensive microscope is not needed for the numerical estimation of the common microscopic organ- isms found in water. A simple, compact stand with a §-inch objective and a loX ocular is sufficient. For studying the
•>■>•>. >
â– '^^^k
Fig. 17.— New Form of Counting Cell. After Bunker.
36 THE MICR08CX>PT OF DBINKIHa WATER
organisms in detail and for general laboratory use in the study of water a large stand, with substage condenser, iris diaphragm, mechanical stage, etc., should be provided. The list of objec- tives should include a 3-inch, a j-inch, a i- or J-inch, and a i*i-inch homogeneous immersion, or their equivalents, and there should be several oculars magnifying from 4 to 12 times.
The use of the microscope is described at greater length in Chapter V.
dcular Micrometer.— -The ocular micrometer is an essential feature of the Sedgwick-Rafter method. It consists of a square
ruled upon a thin glass disk which is placed upon the diaphragm of the ocular. The square is of such a size that with a certain combination of objective and ocular and with a certain tube- length of the microscope, the area covered by it on tlie stage is just one square millimeter. Hence with a cell one miUuneter thick, the volume within the outlines of the ruled square will be one cubic millimeter. For convenience it should be sub- divided as shown in Fig. 18. The size of the largest square is one square millimeter. The size of the smallest square is one standard unit. The best micrometers are made by engraving, but a serviceable micrometer for occasional use may be made
METHODS OF MICROSCOPICAL EXAMINATION 37
by photography.* With a J-inch objective and a No. 3 ocular the square ruled for the ocular micrometer should be 7 mm. on a side. Before using the micrometer the proper tube-length must be determined by trial using a stage micrometer for comparison.
Enumeration. — ^The cell, filled with the concentrated fluid, is placed upon the stage of the microscope and the organisms included within the area of the ruled square are counted. This, of course will give the number in one cubic millimeter of the concentrate. The cell is then moved so that another portion of the cell comes into the field of view and another square is coxmted. This is continued until a sufficient number of repre- sentative millimeter cubes has been examined. It is obviously impracticable to coimt all of the squares which compose the area of the cell. It is usually sufficient to count ten or twenty squares, but a larger number ought to be scrutinized. In count- ing it should be remembered that the cell is one millimeter deep and that some of the organisms are heavy and sink to the bottom, while others are light and rise to the top. The observer \hould make a practice of changing the focus of the microscope so that both the upper and lower portions of each cube may be examined.
From the number of organisms found in the ten or twenty squares or, more exactly cubes, it k an easy matter to calculate the number originally present in one cubic centimeter of the sample.
Let » = the number of squares counted, i.e., the number of cubic millimeters of the concentrate actually examined. / = the total number of organisms foimd in all of the
squares counted. i>= number of cubic centimeters of the sample filtered. c = number of cubic centimeters of water used in wash- ing the sample.
*Tlus idea was suggested by Mr. Wallace Goold Levison, Brooklyn N. Y.
38 THE MICROSCOPY OF DRINKING WATER
Then the number of organisms per c.c. (N) will be represented by the formula
,^ / lOOOC
iV=-X -,
n V
If, for example, 500 c.c. of water was iiltercd and 5 c.c. of water was used for washing the sample, and if 20 squares, i.e. 20 cubic millimeters, were counted •
, ,^ / loooXs I ,
then A^ = — X ^ =-/.
20 5C0 2
The number by which the total number of organisms counted must be multiplied in order to reduce the result to " number per c.c." is commonly called the multiplier.
It should be noted that this is independent of the area of the cell.
Sources of Error. — The operations of the Sedgwick-Rafter method involve several sources of error. They may be classified as follows :
1. Errors in sampling.
2. Funnel error, or the error caused by the organisms adhering to the sides of the funnel.
3. Sand error, or the error caused by imperfect filtration.
4. Error of disintegration, due to the breaking up of organisms on the surface of the sand.
5. Decantation error, or the error caused by the organisms adhering to the particles of sand, and by the water used in wash- ing the sand being held back by capillarity during the process of decantation.
6. Errors caused by the organisms not being uniformly' distributed in the cell.
Errors in Sampling. -These errors arise chiefly from* the fact that organisms vary in specific gravity and in their behavior toward light. If the bottle containing the sample is allowed to stand even for a short time, some of the organisms will sink to the bottom, some will rise to the surface; some will
METHODS OF MICROSCOPICAL EXAMINATION 39
collect on the side of the bottle toward the light, others will shun the light as much as possible; while some will attach them- selves quite firmly to the sides of the glass. Evidently the bottle must be skaken before the portion for examination is withdrawn. Errors in sampling are common, but, to a great extent, are avoidable.
Funnel Error. — The funnel error, due to the organisms settling upon and adhering to the sloping sides of the funnel, varies greatly according to the character of the water filtered. It is highest in the case of samples rich in the Cyanophyceae and amorphous matter. These, being of a somewhat gelatinous nature, adhere readily to the glass, making a rough surface on which other organisms lodge. If the funnel is wet when the sand is put in, some of the sand-grains are liable to adhere to the sloping walls. This tends to increase the deposition of organisms. The fimnel error is less in the cylindrical fimnels than in the flaring funnels. Slow filtration, whether due to the character of the funnel or to the sample filtered, increases the error — ^indeed it may be said that the funnel error is almost proportional to the time of filtration. Numerically the funnel error may vary from o to 15 per cent. A long series of exper- iments with waters that varied greaUy in character gave an average fimnel error of i per cent for the organisms and 3 per cent for the amorphous matter.
Sand Error. — The sand error, due to imperfect filtration, depends upon the character of the organisms, upon the size of the sand-grains, and upon the depth of the sand. In select- ing a sand two opposing conditions must be adjusted. The sand must be fine enough to form an efficient filter, and yet the grains must be large enough to settle readily in the decanta- tion-tubes. A ^-inch layer of the sand described on page 29 ought not to give a sand error greater than 5 per cent unless the water contains minute , organisms. When very minute organisms are present in large numbers the error from incom- plete filtration may be as great as 25 per cent or even 50 per cent. The effect of the size of the sand-grains on the sand error is well illustrated by the following table compiled from exper-
40
THE MICROSCOPY OF DRINKING WATER
iments by Calkins on the filtration of water containing yeast- cells and starch-grains:
|
Sise of Sand. |
Percenatce Sand Error. |
|
|
Yeast -cells. |
||
|
40-60 |
21 6 |
4 4 |
|
60-80 |
8-7 |
7 3 |
|
80-100 |
5 3 |
7.4 |
|
100-120 |
i i |
1.3 i |
Most of the organisms that pass through the sand do 80 during the early part of the filtration, before the sand has become compacted. If, before the sample is poured into the funnel, the sand is compacted by passing through it some distilled water, using the aspirator to increase the pressure, the sand error will be reduced considerably.
Errors of Disintegration. — Many of the microscopic organisms are extremely delicate. They are verj' susceptible to changed conditions of temperature, pressure, and light. As soon as a sample of water has been collected in a bottle some of the organ- isms begin to disintegrate; and if the sample stands long before examination and if it is submitted to the joltings of a long trip by express, some of the organisms ^^dll break up and become unrecognizable. The process of filtration helps to disintegrate them by bringing them in violent contact with the surface of the sand, but the method of concentrating the sample by arresting the filtration as described above reduces this error to some extent by keeping the sand from becoming drj- and by preventing many of the organisms from even reaching the surface of the sand. The errors due to disintegration during transit and before examination can be avoided only by making the exami- nation at the time of collection. This is often necessary, par- ticularly when one is searching for such delicate organisms as Uroglena. The errors of disintegration during filtration cannot be entirely avoided, but if the examination of the con- centrated fluid is supplemented by a direct examination of the water gross mistakes may be prevented. Uroglena, Dinobryon,
METHODS OF MICROSCOPICAL EXAMINATION 41
and other forms may be detected in the sample with the naked eye after a little practice. They may be taken up with a pipette and transferred to the stage of the microscope for more definite identification. This direct examination is important and always ought to be made, but its value is qualitative and not quantitative.
Decantation Error. — The dccantation error depends to a great extent upon care in manipulation. When the attempt is made to separate the organisms from the sand by agitating with distilled water in one test-tube and decanting into a second tube, some of the organisms remain behind attached to the sand-grains, ajtid, what is quite as important, some of the water used in washing remains behind.
The two errors act in opposition. If the sand retains a larger percentage of organisms than of water, the figures in the result will be too low; if it retains a larger percentage of water than of organisms, the concentration will be too great and the figures in the result will be too high. With the fractional method of washing the sand and with due care in decanting the decantation error ought not to exceed 5 per cent.
Errors in the Cell. — The errors due to the imequal distribu- tion of the organisms over the area of the cell are extremely variable and cannot be well stated in figures. If the concen- trated fluid is evenly mixed and well distributed over the cell, if the coimt is made just as soon as the material in the cell has settled, apd if a large niunber of squares are counted, the error will be reduced to a minimum. If a sample happens to contain such motile organisms as Trachelomonas or Euglena they may collect at the edges of the cell in search of air, or if the cell stands in front of a window for any length of time organisms sensitive to light may migrate from one side of the cell to the other.
Precision of the Sedgwick-Rafter Method. — Examination of himdreds of samples has shown that the results are usually precise within 10 per cent, i.e., two examinations of the same sample seldom differ by more than this amount. The accuracy, however, depends greatly upon the character of the organisms in the water examined. On accoxmt of the unavoidable errors
42 THE MICR06COPT OF DRDOONO WATER
in this method care should be taken to avovl fictitious accuracy in tabulating the final results. No decimals or fractions should be used.
Results of Kraminatioa, — ^The microscopical examination of most samples of surface-water will show that the concentrated fluid contains minute organisms of various kinds, fragments of larger animals and plants, masses of a grayish or brownish flocculent material, and fine particles of inorganic matter. The inorganic or mineral matter is usually not considered in the Sedgwick-Rafter method; more information about it can be obtained by a direct examination of the sediment and by chemical analysis. The brownish flocculent material has been called amorphous matter " because of its formless nature, and zoogloca " because of its supposed bacterial origin. The term zoogloca has a definite meaning in bacteriology and is applied to a mass of bacteria held together by a more or less transparent glutinous substance. It is not strictly appropriate as applied to the brownish flocculent matter, which is not so much a collection of bacteria as the product of bacterial action. The word phytoglcea might be used in its place, but the term " amorphous matter " is a broader term and quite as appropriate. The amorphous matter, then, includes all the irregular masses of unidentifiable organic matter. It does not include vegetable fibers, vegetable tissue, etc., nor does it include mineral matter except as this is intimately mixed with the flocctdent material. Standard Unit. The amorphous matter occurs in a finely divided state or in lumps of varj-ing size. In order to estimate correctly its amount it is necessary to have some unit of size. A unit of volume is impracticable because of the great labor involved in determining the dimensions of the masses observed, but a unit of area approaches closely to what is desired. Such a unit was suggested by the author in 1889, and has come into use under the name of " standard unit." The standard imit is represented by the area of a square 20 microns * on a side i.e. by 400 square microns.
* One micron = .001 millimeter.
METHODS OF MICROSCOPICAL EXAMINATION 43
The ocular micrometer shown in Fig. i8 was subdivided to correspond to this imit. The large square, which covers one square millimeter on the stage of the microscope, is divided into four equal squares. Each of these quarters is subdivided into 25 smaller squares, and each of these squares contains 25 standard units. The eye will readily divide the side of a small square into fifths, and this division is the side of the standard imit square. If desired, one of the small squares may be further subdivided into squares the actual size of the standard unit as shown in the figure.
The microscopic organisms vary in size and in their mode of occurrence. Some are found as separate individuals, some are joined together into filaments, or into masses or colonies; some are one-celled, some are many-celled; some are extremely simple, some are complex; some are scarcely larger than the bacteria, some are easily visible to the naked eye. It is dif- ficult to establish a satisfactory system for coimting these varied forms. If an individual coimt is adopted one has to decide what shall be the imit, whether a cell, or a filament, or a colony, or a mass. Practice has varied in this matter. The best system of coimting by individuals is that used by the Massa- chusetts State Board of Health. All diatoms, desmids, rhizo- pods, Crustacea, the imicellular algse, and nearly all rotifera and infusoria are counted as individuals; the filamentous algas are coimted as filaments; the social forms of infusoria and rotifera are coimted as colonies; and many of the algae that occur as irregular thalli are counted as masses.
This system, which, for convenience, we may call the " in- dividual coxmting system," does not always give satisfactory results. In the Boston water-supply it was found often that a sample which a simple inspection showed to be heavily laden with algse and which was offensive both in appearance and in odor gave a low figure in the coimt, while a sample that was clear and agreeable to the taste gave a very high figure. This was due largely to the great difference in the size of the organ- isms. A great mass of Clathrocystis was given no more weight in the result than a tiny Cyclotella. Each counted one, though
THE UICKOeCOPY OF DBINKINO WATER
MICROSCOPICAL EXAMINATION.
SamfU of CrotOH Water, Nfw York CUy.
Date of ColUaiim, Au[. 2S, 1897; Dale of Examinalim, Aug, »$, 1857.'
Omcentration, 500 ce. to 10 u. MultifiUr, 1.
|
' |
3 |
< |
s |
A |
1 |
« |
• |
„ |
, |
2 |
^1 11 |
ii |
||
|
''iuSSonSu' |
\ |
00 JO |
.« |
i |
•i |
» |
,„ |
,„ |
i |
J J |
1 10 T Prwent |
JO.O |
« |
|
|
ISO |
||||||||||||||
|
:? |
||||||||||||||
|
rS |
||||||||||||||
|
13D )40 |
||||||||||||||
|
"2 |
||||||||||||||
|
)4>o |
||||||||||||||
|
X |
||||||||||||||
|
Fungi and 5ciiiiu>ivibibs: |
â– |
. |
||||||||||||
|
Rotifeha: |
||||||||||||||
|
"'SllS." |
||||||||||||||
|
Other OnGAHifiMS^ |
||||||||||||||
|
•• |
â– â– |
.. |
as |
IS |
^ |
" |
" |
is |
" |
'" |
^= |
4641 140 |
||
|
pong p |
METHODS OF MICROSCOPICAL EXAMINATION 45
the former sometimes contained a thousand tunes as much organic matter as the latter. In order to make the figures representing the total number of organisms bear some close relation to the actual character of the water as shown by the physical and chemical analyses, it was suggested that the standard unit already in use for the amorphous matter might be applied to the organisms as well. This " standard unit method" was adopted at the Boston Water Works, and was soon used extensively elsewhere. Its use is now almost universal.
The unit system does not involve much extra labor in the coimting. Many organisms are- so constant in size that they may be coimted individually and then reduced to standard tmits by multiplying by a constant factor. Filamentous forms of constant width may be measured in length and then reduced to units. Irregular masses and variable colonies may be estimated directly in units. In practice it has been foimd desirable to modify the unit somewhat in cases where organisms are especially thick or thin in order that the results may approximate a volumetric determination as nearly as possible.
It is not always that the imit system gives better results than the coimting system. Sometimes it is advisable to state the results both in number of individuals and in standard units.
Records. — ^The results of analysis may be recorded on a blank similar to the one shown on page 44. The ten numbered vertical columns correspond to ten squares coimted. The three right-hand columns give the number of organisms per c.c, the average size of the organisms and the final result in Number of Standard Units per c.c.
The names of the common organisms are printed in the left- hand column, and are grouped according to the system of class- ification described in Part II. The table on page 46, shows the schedules of classification used by different observers. It may be foimd useful in the comparison of different reports.
The Planktonokrit. The planktonokrit is a modification of the centrifugal machine. The water to be examined is placed in two funnel-shaped receptacles attached to an upright shaft, with the necks of the funnels pointed outward. The receptacles
46
THE MICROSCOPY OP DRINKINa WATER
have a capacity of one liter each. The funnel portion is made of tinned copper; the stem is a glass tube that has a bore of 2^ to s nun. The glasses are held in place by a cover, such as is employed in mounting a water-gauge. The shaft is driven by hand or belt through a series of geared wheels, so arranged that 50 revolutions of the crank, or pulley-wheel, produce 8000 revolutions of the upright shaft. By this rapid revolu- tion of the sample the organisms are thrown outward by centrifugal force and collect in the neck of the funnel, from which they may be removed for examination.
SCHEDULES OF CLASSIFICATIONS USED AT DIFFERENT TIMES
AND IN DIFFERENT LABORATORIES.
|
Individual Counting Systkm |
t |
Standard Unit System. |
|||
|
Ma^s. St. nd. of Health. Parker, 1887. |
Boston Water Works. Whipple. i%%9* |
Mass. St. nd. of Health. I Calkins, 1890. |
Conn. .St. Bd. of Health. 1891. |
Brooklyn Water Dept. WhippU, 1897. |
Boston WaUr Works. HoUis, 1897. |
|
Diatomaces |
Diatomaccx Diatomaccx |
Diatomacece |
Diatomacea |
DiatomsnwB |
|
|
DcsmidieflB PalmellaccflB Z<K>sporeac ZyRTicmaces Vulvociniex |
Dcsmidicx Chlorophyce.-c |
Alga â– |
Desmidieflc Protococcoi- dcn Confcrvaceas |
Chlorophycea |
ChlorophyoeB |
|
CyanophycciB |
C y anoph y ocas C ' y an( >ph y co.ts |
Cy anoph ycea |
Cy anoph ycea |
Cyanophyces |
|
|
SchiKomycctcs |
Fungi |
Fungi |
Fungi |
Fungi and Schizomycetet |
Fungi |
|
Protozoa |
Rhizopo<la Infusoria |
Rhizopoda Infusoria |
Rhizopoda Infusoria |
Protozoa |
Rhiaopoda Infusoria |
|
Rotifcra |
Rotifcra |
Vermes |
Rotifcra |
Rotifcra |
Rotifera |
|
Entomostraca |
Crustacea |
Crustacea |
Crustacea |
Crustacea |
|
|
Spongiaria Ncinato<la Annelida |
Miscellaneous |
Miscellaneous (including ZoogUea) |
Ova Spores |
Other Organizmi |
Miscellaneous |
|
Total Total Organisms Organisms |
Total Organisms |
Total Organisms |
|||
|
Amorphous Matter 1 |
Amorphous Matter |
Amorphous Matter |
|||
|
Miscellaneous Bodies |
|||||
* The Standard Unit System has been used since Jan. i, 1893.
There are certain practical objections to the forms of appa- ratus now constructed. It is not only difficult but dangerous to use high speeds when large quantities of water are operated on. Field has been unable to use a speed greater than 3000
METHODS OF MICROSCOPICAL EXAMINATION 47
revolutions per minute. This speed maintained for four minutes, however, was sufficient to throw out all the organisms except the Cyanophycese. By reducing the volume of the samples and by perfecting the mechanical parts of the apparatus it seems probable that excellent results may be obtained by this method.
FlO. 19.— The Wizard Sediment Tester.
mtrati<m Through Cotton. — An interesting and valuable method of keeping a permanent record of the amount of sus- pended organic matter in water is that of filtering a large volume of water through a thin sheet, or plug, of cotton. While this method is not one of great accuracy from the standpoint of the analyst it is an excellent one for showing to the eye the changes which take place in the algs growths in public water-supplies.
THE >nO?.' >>*;«"'?¥ '"'F r^RTVilN'T WATER
The ?>?<: meih-^i L? :±j.: Tzich w-±5 orizizjlly de\Tsed for the determiz^iuoc: cc iir: in =iili k^-r^:: j^ the Wlciird Sediment Te<:er. =iiJ.e ry the l r^fjjincr/ Pick-Lre M±z.i:jc:uring Com- pdzy cc .Xlb^LZ} X Y The lltcrlzx zieciuzi Lsa tain plug of cc::cc ircu: in -zjc j: ziinsfier lezizz :< *e.c becwieen two 5urccr:5 c: •arj« clc:J: iz j. ^Mr i::i^:i;fi :j j. i.i» zulk bottle. Tbt -x-iitz ': re i'.tiri'i if r.^^i-i in :h^ bc:we iz-i ^oved to £."»■j«: inr^u^h :hsf j:::;z F':nu:z i? ba5:ez.edby increas- izj: :he 7:^*<5urf ;: :r.^- i.ir a-;::-.:-. :n-: Vtii-f ry the use of a
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Plate A ibridge Tap Water Colleclcd 01 dur[ne the Autumn of loij.
CHAPTER V
THE MICROSCOPE AND ITS USE By John W. M. Bunker, Ph.D.
To obtain satisfactory results from the use of the microscope one must be familiar with the construction, use, and care of the instrument, and have an intelligent understanding of the optical principles of magnification. The microscope, like any other finely adjusted optical instrument requires intelligent care, and is easily injured by a person not familiar with it. The object of its use is to have presented to the eye a clear image which is larger than the object viewed. The size and clearness of the image obtained with any instrument are depend- ent largely upon its manipulation.
Construction of the Microscope. — The compound micro- scope is a system of lenses set in a mounting suitably adjust- able for their manipulation. The first microscope known was essentially this, being a glass bead mounted on a wire loop. The supporting parts of the modern microscope are the results of years of experience and study, and since the needs are the same, are similar in all the best microscopes.
There is always a base (B Fig. 21) of heavy metal, into which is cast a pillar (P), which in turn is joined to a flat stage (5) for supporting the object to be examined. An inclination joint (I) allows the stage and attached portions to be tipped as a unit to any convenient angle. Moving with the stage and supporting the optical parts is the handle arm (HA) which carries the body tube (T). This tube receives at its lower end by means of a society thread fitting known as the nose-piece (RN) a brass mounting containing the first set of lenses, known as the
49
THE MICROSCOPY OF DRINKINQ WATKE
objecivee (0). At its other end the body tube recdves an exten- sion known as a draw tube (D) by means of which the t^tical
Fig. zi. — Compound Microscope Suitable lor the Examination of Water.
|
E Eyqiiccc. |
S Stage. |
|
D Draw tube. |
SS Substage. |
|
T Body Tube. |
M Minor. |
|
RN Revolving Nose-piece. |
D Base. |
|
O Objective. |
K Rack. |
|
PH Pinion Head. |
P Pillar. |
|
MH Micrometer Head. |
I Inclioatiim |
|
HA Handle Arm. |
path is lengthened or shortened. The upper end of the draw tube carries the second set of lenses in a slip fitting known as ihc eyepiece (£).
THE MICROSCOPE AND ITS USE 51
By varying the distance of these two sets of lenses from the object viewed the clarity of the image is affected. By changing the distance of these two sets of lenses from each other, the size of the image is aflfected. When in the position where the greatest clearness is present, the lenses are said to be in focus, and the adjustment of the system to attain this position is called focusing.
To make focusing easy and certain, the body tube is attached to the handle arm by means of a tongue and groove joint which allows motion in a vertical line through the agency of rack and pinion adjustment screws. There are two of these, the coarse adjustment pinion head (PH) operating directly to bring about a considerable movement, and the fine adjustment micrometer head {ME) working by means of a lever to move the body tube very slowly.
Ever>' microscope is fitted also with a mirror (M) for reflect- ing the light used for illumination up. through the aperture in the stage to the object under examination. In the best micro- scopes there is an optical arrangement of lenses in a convenient mounting swung below the stage in the path of light known as the condenser (55) which reduces the volume of light admitted to the object, at the same time intensifying it.
Use of the Microscope. — The bench upon which the micro- scope is to be set should be at such a height that observa- tions can be made without straining the back of the neck or, on the other hand, compressing the chest. To this end an adjustable stool is desirable.
The microscope should always be used in an upright position owing to the liquid nature of the cell contents to be examined, and the observer should adjust the height of his stool so that he shall sit as upright as is compatible with comfort. Rest the arms on the table as much as its height will permit.
Bring the heel of the microscope to the edge of the table. Grasp the milled head of the draw tube with one hand while holding the body tube with the other, and with a spiral pull bring the tube to the standard length for which the objectives
52 THE MICROSCOPY OF DRINKING WATER
are corrected.* Lower eyepiece into draw tube, attach objective, place object on stage, adjust illumination, and focus on the object.
Placing the Eyepiece. — The exterior surface of the eye-lens and field-lens, being exposed, are apt to become dusty, and should always be carefully cleaned before using. Lens surfaces should be cleaned only with lens paper or a camel's hair brush- Eyepieces should be so loosely fitted that they will drop into the tube as far as the collar by their own weight. Care must be used in placing the eyepiece, or sliding the draw tube, as the objective may be forced against the object and thus destroy it, or injure the lens.
An eyepiece magnifying ten times is most convenient for water work.
Attaching the Objective. — Taking the objective (i6 nmi.) from its box, see that its front lens is clean; elevate the body tube by means of the coarse adjustment {PH) so that the nose- piece {RN) shall be at least two inches from the stage (5).
To properly attach an objective is not always simple, and cannot be done too carefully. There is danger of dropping the objective onto the object, thereby damaging either or both, also of starting the threads wrongly by holding the objective sideways, and thus injuring the threads.
Grasp the upper knurled edge of the objective between thumb and forefinger of the left hand; bring the screw in con- tact with the screw of the nose-piece, and, keeping the objective in line with the tube and gently pressing upward, revolve the objective with the thumb and forefinger of the right hand by the lower milled edge until shoulder sets against shoulder.
Finding an Object. — La general practice, a low power objective is used to find and center an object, after which the power under which it is to be studied is swung into place. In water work, however, the low power of magnification involved makes the use of any other objective superfluous. By grasping the slide containing the object with the thumb and the first or second finger of the right hand and racking the objective to about
* Bausch and Lomb, i6o mm.; Carl Zeiss, i6o mm.; Ernst Leitz, 170 mm.
THE MICROSCOPE AND ITS USE 53
three-eighths of an mch from it and then passing the slide to and fro, the shadow of the image can usually be seen as the object flits by.
Illuminating the Object. — ^Illumination is an extremely impor- tant detail, and should always be carefully regulated, as one may easily fail to obtain the best results, may be led to wrong con- clusions, or may injure the eyes. The mirrors (M) of the microscope are usually plane and concave, and are adjustable so as to be able to reflect the light from any source in front or at the side of the microscope.
The plane mirror reflects the light in its initial intensity; the concave mirror concentrates the rays on the object, thereby giving intensified illumination.
When a substage condenser is used, the plane mirror is employed.
The sources of lihgt are either daylight or artificial light. If the former the light of a northern sky is preferred, and if the latter a Welsbach gas burner. An ordinary gas flame should not be used on account of the difficulty of obtaining even illumina- tion and the constant flickering which is injurious to the eyes. If using a flat-wick lamp the narrow edge of the flame should be used, as this is more intense than the broad side.
In general, artificial light will give better color values if the blue glass screen is inserted in the clip below the substage condenser. It is, even under the best conditions, not to be compared with daylight from the point of view of desirability.
When using daylight, place the microscope as nearly as possible before a window. If artificial light must be employed, set it in front of the microscope or at one side with a screen between so adjusted on a stand that the upper part of the microscope and the eye of the observer are shaded from the light which is allowed to fall below the screen onto the mirror.
Light is transmitted to illuminate transparent objects, and passes through the object from below the stage into the objective. With opaque objects this is impossible and reflected light is required, which is directed onto the object from above and
M THE 3UCRC^X>Py OF DRIXKDCG WATER
iUununates its upper surface. In the foUowing instnictioDS it is assumed that transmitted light is used.
Before lighting on object moke certain that the minor bar is in e.\actly central position, and set the nurror at such an angle to the light that it will be rejected u{x» the object, which can be done more quickly at the outset by ohserx'ing the object or the o|vning of the stage, keeping the head at one side of the tulx\ Now remow the ex-epiece. and obser\"e the light vvtv.inc thrvnisih the v^b\v:ive. I: should be central and of ev;u,ri in:cnsi:\ . which w::h cl jvlichi is sometimes difficult to oVMir; as the s^ish c: :hc window rjiay be reflected and show itscl: in the delvi as dark bonds, or in the case of lamplight the blue jx^rtion o: the r.an:e r.iay apixur as a dark spot. These are or.Iy prelir.ur.An d;rxv::or.s bu: wil! su5ce for a b^;inmng. There will :v lizzie vi::r.cul:\ in obzoining pn.'»per iHumination at the outsc: •: or.e will observe :he following:
Kenwe :hc e>epicce ar-c. looking ihnx:;^ the bac^ of the ob recti ve, havv
er.zr.i; :
M%% ••• • •
rV'vV'.s I" iV.,:-v:n,i:v" ^\>.ur. r.^y not Sf apparent will Wr.cr zr.c v^v.:'.iv..*s x*: .m x^^;cc: .irc brl^iti: oc oce side and
^ ..r*. . •• «. X--. >v> , X ^, . x" *-L-. j< _..jLx-c ;/» ^^iiiam\
.Iv. ..'*' .^ ,.->^ .x>. ,.-.. X. ...x V. .-i>^ ** 7xV-»Cing UDC
.•_..■X, . ^... x» ...X ..>v X. ,-.x — > x- '.4»,— . x<«<ive2 uiiiior
^^ .^ . . . X X • -
m • ... > . *%•
.> . , ■» ^ , x . . . ^ .. . x\ . xv ■, >v , ■JL . .'- i.j> "fcttt me
• X
^. , . . « ^"V *'.V .X ..... .X.. . ^ . m ."...... ■X«X « X ^Mi.7
.â– vv*.v" :".:: :>.'^ cva*^'*^
-— r^ ^ • — ^ .^.:^- -. > — .V. X. ■.^>. .c sJL.ct* acofpteu
â– K
THE MICROSCOPE AND ITS USE 55
that, if the eye tires or feels uncomfortable, the light should be moderated.
Focusiiig. — The act of focusing is merely the bringing of the objective to that distance from the object where a clear image is obtained. Care must be exercised against allowing the face of the objective to come in contact with the cover-glass, which is almost sure to bring injury to one or both. To that end,
ALWAYS FOCUS UPWARD
Having attached the 16 mm. objective to the nose-piece, lower the eyes to the level of the stage so as to be in a position to observe the face of the objective; lower the tube by the coarse adjustment until the face of the objective is one quarter of an inch from the object; look through the eyepiece and slowly revolve the coarse adjustment pinion head in a contra- clockwise direction, elevating the optical system until the image comes into view. With the left hand continue the adjustment of focus until a sharp image is obtained. At the same time, with the right hand, manipulate the iris diaphragm below the substage condenser until the amount of illumination is present which is optimum for your vision.
The upward movement should be slow so that, if the object be faint, it is not missed and the adjustment not run beyond its focal distance. It is possible that, in the case of a very minute object, it may be out of the center, and thus out of the field of vision, in wliich case the surface of the cover-glass, or the minute particles of dust upon it should be distinguishable.
The object will first appear with faint outlines and indis- tinct; then gradually more distinct and finally sharply defined, and if adjustment goes beyond this point, it will gradually become dimmer, in which case return to the point of greatest distinctness.
It is also an aid in focusing on isolated specimens in a clear field to move the cell slpwly in different directions, as the flitting shadows and colors moving across the field of view give warning of the approach of the focal point.
56 THE MICROSCOPY OF DRINKING WATER
Use of Substage Diaphragm. — ^The purpose of the dia- phragm mounted below the substage condenser is to modify the amount of light and by this attain sharpness of definition which otherwise would be impossible. By its use, so much light as would produce a glare is avoided as well as so small an amount that eye strain would result. The opening best suited varies with lighting, the density of the object observed, and the sensitiveness of the eye of the observer.
Which Eye to Use. — The writer has found it more convenient to use the left eye for observations, lea\dng the right free for the drawing paper or note-book without turning the head.
Cultivate the habit at tlte outset of keeping both eyes open. — There is a point just above the eyepiece called the eye-point at which rays cross withiii the smallest compass, and this is the proper position for the eye. When not at this point shadows or colors appear in the field which becomes reduced in size.
Practice Exercises. — i. Place a piece of lens paper torn apart as much as possible on a clean slide (the back of your counting cell will do) and place a drop of water on it. Lay the cover slip over the whole letting one edge touch the wet area first so that in falling the slip will force out under the other edge any air bubbles. Place this mounted preparation on the stage and focus on it.
2. Mount and examine in the same way a cotton fiber, a wool fiber, one of silk, a small pinch of dust.
3. Scrape the inside of the cheek with a clean glass rod or sliver of wood and wash it off carefully in a drop of water, mount and examine with light cut way down.
4. With a pin or sharp knife tease off a minute scale of the skin of an onion or a bit of celery, mount and examine.
5. Dissolve a small portion of yeast in warm water, let stand a few hours, and examine a drop of the liquid.
6. Scrape a bit of green from the north side of a tree and examine in a drop of water.
7. Soak a handful of hay chopped fine in a pint of water in a warm place for a few days. The liquid will be swarming with various micro-organisms.
THE MICROSCOPE AND ITS USE
57
ReUnal Image
E70
Slmpto Leni
8. Gather a bit of scum from a stagnant puddle and examine.
Ponds, ditches, stagnant pools, all are prolific sources of objects, animals, and plants which are interesting to observe and which accustom one to the appearance of microscopic life.
Optics of the Microscope. — The niagnification brought about by a microscope depends upon the fact that rays of light passing from one medium to another at an angle become bent according to the angle at which they pass from the first mediiun to the second. By controlling this angle of in- cidence the degree of bending can be greatly increased, and lines of light which passing through the air, would meet the lens of the eye at a sharp angle are made, by the inter- position of glass in the form of a lens to meet the eye in a wider angle. As the eye cannot diflferentiate such bent lines from straight ones, the sensation recorded upon the retina is that of viewing a large object. This is graphi- cally shown in the accompanying diagram. Fig. 22.
If the rays of light from the object had not been inter- cepted by the lens of the eye they would have continued on to. a point where they would have been again sorted out, as it were, and a sheet of paper held at this point would have shown a real image magnified and inverted. This principle is utilized in the compound microscope, in which a second simple lens (the eyepiece) picks up the magnified inverted real image formed in the tube of the microscope by the objective. This real image is again magnified and presented to the eye of the observer as a virtual image of the original object, greatly enlarged and turned end for end, cf. Fig. 23.
Object
Apparent Image
Fig. 22. — Optics of Simple Magnification.
58 THE MICEOSCOPY OF DRINKINa WATER
Fic. 13. — Oi)iics of the Compound Mierowope. After Bausch.
Scv uppoiite paRG for dcacription al Bfvn.
C MICROSCOPE AND ITS USE
SO
niummatioii. — It is evident that too much care cannot be taken to secure the proper adjustment of illumination. Hence the manipulaUon of the condenser is all important. As previously mentioned only the plane mirror should be used with a condenser. The optical reason for this is shown in Figs. 34, 25 and 26.
tu- .
Fig. 34. — Methods o( Illun:
Concave Minor. uting Objects with Plane and Concave MicTOiS.
Care of the Microscope. — Besides acquiring the ability to use an instrument with its accessories, it is important to know how to keep it in the best working condition. It may be said without reserve that an instrument properly made at the outset and judiciously used should hardly show any ^gns of wear either in appearance or in its working parts, even after the most protracted use.
Index to Fig. 23.
Upper local plane of objective.
Lower focai plane of eyepiece.
Optical lube length = distance between Fi and Fi-
Object.
Real image in Fi, transposed by the collective lens, lo
Real image in eyepiece diaphragm.
Virtual image foniied at the projection disUnoe C, 150 mm. Irom
Eye-point.
Condenser diaphragm.
Mechanical tube length (160 mmO.
Three pencils of parallel light coming From different points of a distant
illuminanl, tor Instance, a white cloud, which illuminate three different
points of the object.
THE MICROSCOPY OF DRINKING WATER
Especial care should be given to the optical parts, in fact such care that they will remain in as good condition as when first received, after any amount of use.
Care of the Stand. — Keep free from dust is one of the first rules to be observed. \Mien not in use place the microscope in its case, or cover with a bell jar or close-mesh cloth such as
1
With Candennr. Without Canitnat
Fio. IS— Path of the Illuminating Rays with and without the Use □( i
cotton flannel or velvet which should reach to the table. If dust settles on any part of the instrument remove it first with a camel's hair brush and then wipe carefully with a chamois skin, wiping with the grain of the finish of the metal and not across it, as in the latter case it is likely to cause scratches.
Fig. 26. — Illuminali
lUuminating Object with Condenter ud The wrong w»y. with Plane and Concave Mirrors.
When handling the stand, grasp it by the pillar or handle arm. While the arm is the most convenient part it is at the same lime the most dangerous to the fine adjustment except in instruments of the handle-arm tyyte.
Avoid sudden jars, such as pladng upon the table or into the case with force.
THE MICROSCOPE AND ITS USE 61
Remove any Canada balsam or cedar oil which may adhere to any part of the stand with a cloth moistened with xylol and wipe dry with chamois.
Use no alcohol on lacquered parts of the instrume^t as it will remove this finish. As the latter is for the purpose of preventing oxidization of the metals, it is important to observe this rule. Parts finished in black are usually alcohol proof.
To use the draw tube impart the spiral motion.
Before using a screw driver grind its two large surfaces so that the)' are parallel and not wedge-shaped, so it will exactly fit in the slot of the screw-head. Turn the screw with a slow steady motion pressing the screw-driver firmly into the slot. No screw-head will ever be injured if these points are observed.
Care of the Coarse Adjustment. — Special care should be given to keep the coarse adjustment free from dust as its effect is particularly pernicious. The slides and rack and pinion are necessarily exposed and the lubricant is apt to catch dust and also to gum. The tube should be occasionally with- drawn from the arm and the slides carefully wiped with a cloth moistened with xylol. Lubricate by applying a small quantity of parafl&ne oil to a cloth and wiping well over the surfaces, removing the superfluous amount with a dry cloth. The teeth of neither rack nor pinion should ever be lubricated. An occasional cleaning of the teeth with an old tooth brush is advisable.
It is advisable occasionally to lubricate the pinion shank on both sides of the arm with a very minute quantity of parafl^e oil.
If the pinion works loose from jar incident to transporta- tion or long use, which sometimes occurs to such an extent that the body will not remain in position, increase the friction upon it by tightening the screws on the pinion cover.
Fine Adjustment. — In a general way it may be said that if the fine adjustment ceases to work satisfactorily the instru- ment had better be returned to the marker, as it involves the most delicate working and few people are conversant with its construction. There is very seldom any occasion for this, however, if used with reasonable care.
62 THE MICROSCOPY OP DRINKING WATER
If the fine adjustment does not respond to the turning of the micrometer screw, or if it comes to a stop, it indicates that the adjustment screw has come to the limit of its motion at either end. It should by no means be forced; it should at all times be kept at a medium point.
Care of Lens Surfaces. — ^No dust should be allowed to settle on the eyepiece nor should any lens be touched by a finger. Occasional cleaning is desirable on all surfaces, however. To accomplish this use a camel's hair brush to remove dust, breathe upon the surface, and imparting a spiral motion to the lens wipe it gently with lens paper. Hold in the blast of a fan, or dust with a cameFs hair brush to remove final fibers that may adhere.
Eyepiece. — ^\'isible defects in the field are always traceable to impurities in the eyepiece, not in the objective, and are easily recognized by rcvoh-ing it. Indistinctness in the image or loss of light may be due to soiled or coated surfaces in either eyepiece or objective.
Dust if on either the ejc-lens or field-lens is apparent as dark, indistinct spots.
Objective. — This should be used with the utmost care. The systems should never be separated, even if they can be unscrewed, as they are liable to become decentered and dust may enter.
Avoid all violent contact of the front lens with the cover glass.
Occasionally examine the rear surface of the objective with magnifier and if dust be present remove with camel's hair brush.
While cleaning give the objective a revolving motion.
If any part of the microscope cannot be brought to a satis- factory working condition by the foregoing instructions, or any part is injured b}' accident it should invariably be sent to the maker or to a reliable manufacturer of microscoiw^.
Measurement of Microscopic Objects.— In measuring objects viewed through the microscope, it is necessary to have two scales, one fixed for all conditions, and the other variable for
THE MICROSCOPE AND ITS USE 63
each magnification. These scales are called micrometers. The fixed scale is an arbitrary one and may take the form of parallel lines with each tenth one accentuated, or of rectangles of varying or similar sizes, or any recurring geometric form. It is placed on the diaphragm of the eyepiece which is set by the makers at that plane in the eyepiece at which the real image is projected by the objectives. In looking through such a system the real image of the object under observation will coincide with the lines etched on the eyepiece micrometer and will be projected with them into the eye of the observer. It is possible then to express either the length or breadth of this object in terms of unit divisions by careful inspection.
To calibrate a given microscope is merely to determine the actual value in terms of linear measurement of each of these units for a given fixed .condition of magnification. This is done by placing upon the object stage a slip of glass accurately ruled off into certain suitable divisions of known length. This slip is called the object micrometer. It is customarj' for such a micrometer to have a space of i nmi. accurately divided into one hundred parts with each tenth division suitably indicated. By focusing upon this ruled portion it is possible to read off on the eyepiece micrometer the equivalent in hun- dredths of a millimeter of each of its divisions.
This gives the apparent image value of a known distance (i mm.) in terms of the eyepiece micrometer units which value can then be substituted for the equivalent in eyepiece units in determining the length of any object observed.
It is customary in micrometry to take as a unit of length the distance one one-thousandth of a millimeter which unit of measurement is called the micron (plural, micra) whose sym- bol is the Greek letter ;jl.
If the lines of the stage micrometer do not coincide with any divisions in the eyepiece micrometer, they can be made to do so by increasing the length of the draw tube by pulling it out with a rotary motion.
Once the proper position is obtained the tube length should be read from the graduations on the draw tube and recorded,
64
THE MICROSCOPY OF DRINKING WATER
along with the power of the eyepiece and of the objective and the eyepiece micrometer value.
This insirumeni al this tube length, with ike same ocular and objective will always have the same micrometer value when in focus,
A new departure in the ruling of eyepiece micrometers is shown by the Leitz step micrometer shown in Fig. 27.
In this micrometer the intervals are arranged in groups of ten, each group being set of! by a black echelon rising from the first interval. The intervals instead of being iV or ^ mm. wide, as is usually the case, have a definite value of .06 nmi. in order to obtain for each objective at the Leitz tube length (170 nun.) convenient and integral micron values for these divisions.
s s 8
s 8
8 g §
Fig. 27. — Leitz Step Micrometer. (Stage Micrometer.)
In the enumeration of micro-organisms a special form of eyepiece micrometer has proved to be convenient. This con- sists of a ruled square of such a size that with a 16 mm. objective and a iojc eyepiece and the proper tube length the area covered by it on the stage is one square millimeter. It is further sub- divided into four equal squares one of which is further divided into twenty-five equal squares, each of which will cut off on the stage tV of a millimeter. The square nearest the center is again subdivided into twenty-five equal squares each of which measures 20^1 on a side. The area of one of these smallest squares is a convenient unit for estimating the area of micro- organisms and is called a slufuiard unit. (Fig. 18.)
Magnification. — Magnification is the ratio between the linear size of the object and the size of its visual image. It may be determined by the use of a device which allows the image to be projected virtually onto a sheet of paper at the side of the
THE MICROSCOPE AND ITS USE 65
microscope which may then be measured by dividers while the observer is looking down through the scope with both eyes open. This is known as a camera lucida and will be explained elsewhere.
If the observer use a stage micrometer he can measure the Mze of the virtual image of i mm. which will give directly the magnification. Magnification can be varied by one of three methods :
By using a higher or lower powered objective.
By using a higher or lower powered eyepiece.
By varying the length of the tube of the microscope.'
Flo. aS.— Abbfi Caxnera Lucida.
Drawing and Photographing Organisms. — There are two ways in which the study of micro-organisms may be accelerated and the results made permanent. As new species are met with and identified it is useful to have their pictures for further reference.
An accurate drawing can be made to scale by the use of a simple attachment known as the camera lucida, by which the drawing surface and the visual field are superimposed in the eye so that it appears that the visual image is projected onto the drawing board where its outlines can be traced with a pencil.
60 THE MICR()SCX)FY OF DRINKING WATER
The best form is that of the Abbe camera lucida which is depicted in Fig. 28.
It should be noted that in drawing with the camera lucida it is necessur)' to have the drawing board tilted a little so that the vertical from it to the center of the mirror is at a right angle to the center of the board. Usually the stage of the microscope interferes if the mirror is set at exactly 45** and the board laid flat.
|
J |
1 |
V\<: .VI, -r'h..l..nii. roiriMiilii, CiuiuT;!,
A more accunilc rc|iroiluiti<)n can he niadi' wilh ihe camera, .Viiy camera box of the l)cllow> type with suflicienlly long e,\tfn>inn can Ik- utilized 1>\ replacing ihc lens with a collar over which a black iiafi can be lied, the ulher end being f;(s(em'(l Dver ihe tiilK' iif the scope. The camera should be suppnrtei! by a rin^ staiiil or special support dirtvlly over the micriiscdpe in such a imsitiuii that the groinid glass screen
THF. MICBOSCOFK A.NI) ITS USE 67
68 THE MICROSCOPY OF DRINKING WATER
is about lo inches above the eyepiece. By bringing the micro- scope to a focus, a real image is projected onto the ground glass screen which may be photographed. Strong artificial iUumina- tion is necessary.
A camera box for this purpose can be purchased from any of the standard optical companies. See Fig. 39.
For really good results a rigid frame with adjustments for manipulating the magnification, light, color screens etc., is desirable. These are made in different sizes and cost from S200 and upward.
The author has found the Edinger drawing and projection apparatus fitted with a camera bellows, satisfactory for photo-
Fic, 31. — Leiti Double Demonstration Eye-piece.
graphing micro-organisms. It is rigid, easily manipulated, and with it the amateur need waste very few plates to obtain excellent re.-iults. The photomicrographs appended herewith were made on this instrument. It takes standard eyepieces and objectives so that this equipment need not be duplicated. The same instrument can be used for drawing by removing the camera bellows and substituting a drawing board for the ground glass focusing screen.
Projection.— For introducing classes to the study of the microscopic organisms, and for demonstrating unusual species some form of projection may be profitably employed — either the direct microscopic projection of specimens in their natural
THE MICROSCOPE AND ITS USE 69
state or lantern slides of photomicrographs may be employed. For the former any of the standard micro-projective or photo- micrographic apparatus may be adapted, but it is unsatisfactory owing to the difficulty of bringing an object mounted in fluid
— Type of Microscope Siiiiable for ihc Examiiiai Organisms in Wiitcr.
I to a focus in one plane. The short distance from the microscope lat which the screen must be placed in order to retain a sufR- t'ciently brilliant image, and the impossibility of rendering true I colors by artificial light are also objc'ctions.
Lantern slides of photomicrographs, if properly colored,
70 THE MICROSCOPY OF DRINKING WATER
give an accurate picture that is permanent and portable. A crudely 'Colored slide is, however, less desirable than caie in monochrome.
Color photography is a newly opened field to the micro- scopist. It is said that the new duplicating process of the Paget Company of London makes it possible to print any number
Fig. 3s. — Bausch and Lomb's Portable Microscope.
of panchromatic slides from one properly taken negative. The process, still in its infancy, involves manipulations that bar it from the ordinary amateur, but which are not insurmount- able to the photographer of some experience. It is to be hoped that attention will be given in the future to the development of the means of increasing the pleasure and the profit of study- ing microscopic organisms through the medium of color-photo- micrography and projection.
THE MICROSCOPE AND ITS USK 71
Demonstration Eyepiece. — ^In class work and for simul-
1 taneous examination of objects by two observers the Leitz
double demonstrating eyepiece is valuable. This eyepiece
fits any standard lube, and contains a prism which deflects
30 per cent of the light rays collected by the lield-lens through
a side tube to a second eye-lens, allowing 60 per cent to travel
in their normal course, 10 per cent being lost. The eyepiece
is equipped with a pointer on a universal joint in the plane
Lof the real image so that structures pointed out by either observer
Bare brought to the attention of the other. (Fig. 31.)
I
Fic. 34. — Microscopical Field Work at Squam Lake, Hatva.rd EnKintering Schuul Course In Limnology.
Field Work. — In the examination of water in the field a light portable outfit is desirable. For a low priced but efficient microscope that made by Bausch & Lomb and illustrated in Fig. 32 is sufficient. .\ lac eyepiece should be specified instead of the one usually furnished.
Folding microscopes are also made whose equipment is of the best. These arc satisfactory, though about twice as expensive as regular styles.
In addition the field equipment should contain a sling filter for concentrating organisms, a. counting cell or two, and a sup-
72 THE MICROSCOPY OF DRINKING WATER
ply of cover-glasses which are very liable to be broken in the field.
Field work is most important as there on can get the organisms in a fresh state and study their distribution in a thorough manner doing away with the difficulty of transporta- tion of samples.
Fig. 34 shows how it can be carried on under very pleasurable circumstances.
REFERENCES
Bagshaw, W. 1909. Elementary Photomicrography. London. Iliffe & Sons,
Ltd. Barnard, J. E. 191 1. Practical Photomicrography. London. Edward
Arnold. Bausch, E. 1901. Manipulation of the Microscope. Rochester. Bausdi&Lomb
Optical Co. Carpenter, \V. B., and Dalunger, W. H. 1891. The Microscope and Its
Revelations. Philadelphia. P. Blakiston, Son & Co. Gage, S. H. 1904. The Microscope. Ithaca. Comstock Publishing Co. Hanausek, T. F. 1907. The Microscopy of Technical Products. New York.
John Wiley & Sons. Spitta, E. J. 1909. Microscopy. Ix)ndon. John Murray. VViNSLow, C.-E. A. 1905. Elements of Applied Microscopy. John Wiley &
Sons, New York. Wrkiht, Sir A. E. 1907. Principles of Microscxjpy. New York. Macmillan
Co.
CHAPTER VI
MICROSCOPIC ORGANISMS IN WATER FROM DIFFERENT
SOURCES
In studying the distribution of microscopic organisms in nature it will be convenient to consider the following classes of water-supplies separately:
1. Rain-water.
2. Ground- WATER.
Springs, Wells, Infiltration-galleries, InfiUration-basins*
3. Surface-water.
Streams, Catials, Ponds, Small Natural Lakes, Artificial Reservoirs, Great Lakes.
4. Filtered Water.
Rain-water. — Rain-water is perhaps the purest water found in nature, yet it sometimes contains micro-organisms. For the most part they are so minute that an examination by the Sedgwick-Rafter method fails to reveal them, but larger forms are sometimes observed.
The study of the organisms found in rain-water is really the study of the organisms found in the air. It is worthy of more attention than has been given to it. The presence of organisms, or their spores, in the air may be demonstrated by sterilizing some water rich in nitrogenous matter and exposing it to the air in the light. After a week or two it will contain numerous forms of microscopic organisms which must have settled into the liquid from the air or developed from spores floating in the air.
Rain-water collected in a sterilized jar and allowed to stand protected from the air often develops a considerable growth of algae, usually some Protococcus form, showing that
74 THE MICROSCOPY OF DRINKING WATER
the rain has not only taken up the organisms or their spores, but has absorbed sufficient food material for their growth. Samples of rain-water sometimes contain a surprisingly large amount of nitrogenous matter, especially if collected in the vicinity of a large city and at the beginning of a storm.
It has been noticed frequently that vigorous growths of alga^ have appeared in ponds or reservoirs immediately after a rain-storm, the growth occurring suddenly and simultaneously throughout the whole body of water. It has been suggested that these sudden growths may be caused by the dried spores of the algaj being lifted from the shores of the ponds and scat- tered through the air by the wind, and then washed into the water by the rain. This supposition is in harmony with the theory that in the case of certain algaj sporadic development occurs only after the desiccation of the six)res.
Ground-water. — Ground-water is water that has filtered or percolated through the ground. It comes to the surface as springs or is collected in wells or infiltration-galleries.
Ground-water collected directly from the soil before it has had an opportunity to stand in pipes or be exposed to the light is almost invariably free from microscopic organisms. Its passage through the soil filters them out. It usually con- tains an abundant supply of plant food, extracted from the organic and mineral matter of the soil and modified by bacterial action, and when the water reaches the light this food material is seized by the micro-organisms. One will recall the luxuriant aquatic vegetation at the mouth of some spring or in some watering-trough supplied with spring-water. Organisms are occasionally met with in ground-water supplies, but their pres- ence usually indicates that some surface-water is also present. With the exception of the Schizomycetes, the number of organ- isms depends upon the exposure of the water to the light and air; that is, it is only as a ground- water becomes a surface-water that the microscopic organisms develop.
The table on page 76, compiled from the examinations of the Massachusetts State Board of Health, gives an idea of the organisms met with in ground-water supplies. Except in the
MICROSCOPIC ORGANISMS IN WATER 75
case of the springs, the figures represent the average of monthly observations extending over one or more years.
Spring-waters usually contain no microscopic organisms. Several exceptions are noted in the table — one at Westport, where 455 Himantidiimi were present, and one at Millis, where the water contained 180 Chlamydomonas per c.c. That these were accidental is shown by the fact that in 1893 five examina- tions of the Aqua Rex Spring showed an entire absence of organisms.
Well-waters also are ordinarily free from organisms, but in some cases Crenothrix grows abundantly in the tubes of driven wells. This is particularly true if the water is rich in iron and organic matter and deficient in oxygen. Wells driven in swamps are often thus affected. The tubular wells at Provincetown are an example. Crenothrix is sometimes found there as numerous as 20,000 per c.c. The water contains more than 0.125 parts of albuminoid ammonia per million, and the iron varies from i.o to 5.0 parts per million. Many similar cases might be cited. GalHonella, Clonothrix, Chlamydothrix, and Cladothrix are also observed in well-waters rich in iron and manganese. Crenothrix grows in tufts or in felt-like layers on the inner walls of the tubes. By the deposition of iron oxide in its gelatinous sheath it clogs up the tubes and strainers and even the sand around the well tubes with iron-rust.
Infiltration-galleries are practically elongated wells located near some stream or pond. They are similar to wells in regard to the presence of micro-organisms. Few organisms other than Crenothrix are found, except when surface-water gains admission.
Infiltration-basins are infiltration-galleries open to the light. The water in them is sometimes affected with algae- growths. The infiltration-basin at Taunton, Mass., for example, has given trouble from this cause. In October 1894 there were more than 1000 Asterionella per c.c. present, and they were followed by a vigorous growth of Dinobryon. Infiltration- basins are practically open reservoirs for the storage of ground- water, a subject treated in another chapter.
76
THE MICROSCOPY OF DRINKING WATER
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MICROSCOPIC ORGANISMS IN WATER 77
Surface-water. — ^The term " sxirface-water " includes all collections of water upon the surface of the earth, such as. lakes, reservoirs, ponds, rivers, pools and ditches.
The table on page 78 shows that surface-waters contain many more microscopic organisms than ground-waters, and that standing water contains more organisms than running water.
River Waters. — River waters unless draining lakes or reser- voirs seldom contain large numbers of microscopic organisms, and water-supplies drawn from rivers and subjected to limited storage are not often troubled with animal or vegetable growths. This may be true even where the banks of the stream are covered with aquatic vegetation. The organisms foimd in streams- often include a great variety of genera and of these many are likely to be sedentary forms. Their food-supply is brought to them by the water continually passing. In quiet waters there are found free-swimming forms that must go in search of their food. It is difficult to draw a sharp line between these two- classes of organisms. Some are free-swimming at will or dur- ing a part of their life-history, and some free-swimming organisms- are always found associated with sedentary forms. In most rivers there are some quiet pools where free-swimming forms- may develop and in many streams there are dams which back up the water so as to form large reservoirs. Here luxuriant growths often occur. Thus we find that the water of the Ohio- River at Louisville and elsewhere often contains so many diatoms as to have a marked influence on the filter through which the city water is passed.
In a sample of river-water, then, one is likely to find sedentary forms which have become detached, organisms which have developed in the quiet places or in tributary ponds, and spores or intermediate forms in the life-history of sedentary organisms. In streams draining large ponds or lakes the water naturally has the character of the pond- or lake-water, and organisms may be abundant.
The number of microscopic organisms found in rivers is. subject to great fluctuations. If the water is rich in foodt
78
THE MICROSCOPY OF DRINKING WATER
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MICROSCOPIC ORGANISMS IN WATER 79
material, littoral growths often develop with rapidity, while a heavy rain that increases the current of the water and the amount of scouring material that it carries may suddenly wash away the entire growth. With such conditions the number of organisms collected in a sample may be above the normal. At other times a rain may diminish the number of organisms in a sample by dilution. But the fluctuations are due chiefly to changes that take place in the growths in tributary ponds or swamps, and to the fact that rains may cause these ponds to overflow.
The table on page 78 shows that the Diatomacese are the organisms found most constantly in rivers. Navicula, Cocco- nema, Gomphonema and other attached forms are common, but their numbers are small compared to those found in standing water. Some of the Chlorophycese, particularly Conferva, Spirogyra, Drapamaldia and other filamentous forms, are often observed. The Cyanophyceae, except the Oscillarise, seldom occur. Stony Brook, in the table, represents a stream affected by tributary ponds where Cyanophycea? abound. Crenothrix is quite often reported in river-waters, but Antho- physa is often mistaken for it, and this may account in part for the high figures in the table. Leptomitus sometimes occurs in foul waters. Animal forms are not common in rivers unless the water is polluted, but when this is the case there may be a succession of protozoa, alga:, rotifers, Crustacea and fish down- stream.
Canal Waters. — In the slowly nmning water of canals and ditches organisms sometimes develop in large numbers, but the conditions are not often such as to cause trouble in public water-supplies. The following instance, however, is worth noting:
On Sunday, July 12, 1896, it was observed by some of the residents living in the western part of the city of Lynn, Mass., that the water drawn from the service-taps had a green color. A glass of it showed a heavy green sediment when allowed to stand even for a few minutes. On the following day it became worse, and when the water was used for washing in the laundry
80 THE MICROSCOPY OF DRINKING WATER
it was found to leave green stains on the clothes. These acted like grass-stains. Investigation showed that the stains were caused by Raphidomonas, and that these organisms were abundant in the city water. Examination of the four storage- reservoirs showed that they were not present there in sufficient numbers to account for the trouble. The water from one of the supply-reservoirs, Walden Pond, reaches the pumping-station by means of an open canal, tunnel, and pipe-line. It was in this open canal that the Raphidomonas were found. The sides of the canal were thickly covered with filamentous algae^ chiefly Cladophora. The water in the canal had a dark green color. WTien a bottle of it was held to the light it was almost opaque and was seen to be densely crowded with moving green organisms. As many as 2000 per c.c. were present. Evidently the organisms had developed among the algae in the canal and had gradually scattered themselves out into the water from Walden Pond as it passed through the canal on its way to the city. The trouble was remedied by emptying the canal through the wasteways and cleaning the slopes to prevent later development. This is the only case on record where Raphidomonas has caused trouble, though the organism is often found in surface-water supplies in small numbers.
Lakes and Reservoirs. — All quiescent surface-waters are liable to contain microscopic organisms in considerable num- bers. The water that is entirely free from them is very rare. It is scarcely possible to collect a sample of stagnant water at any season of the year without obtaining one or more forms of microscopic life They are present not only in the mud puddles in the streets, but in large reservoirs; not only in rain barrels, but in the Great Lakes and even in the ocean. The extent and character of the growths vary greatly in different ponds and at different seasons.
As it is in ponds, lakes and reservoirs that the micro- scopic organisms cause the most trouble, it is these bodies of water that chiefly interest us. Before considering the organ- isms in this class of water-supplies it is important to know something about the physical conditions of water in ponds
MICROSCOPIC ORGANISMS IN WATER 81
and lakes. These are discussed in the following chapter. In passing, one should observe from the table that all classes of organisms, except perhaps the Schizophyceae, are much more abimdant in natural ponds and in reservoirs than in rivers.
Filtered Water. — Water which has been filtered, either by the method of slow sand filtration or by mechanical filtration, sel- dom contains many microscopic organisms. Their presence in a filter effluent generally indicates that the filtration is imper- fect. In the case of mechanical filtration microscopic organisms are somewhat more likely to appear in the effluent, than in sand filters. This is apparently due in part to the use of coarser sand and a higher rate of filtration and in part to the fact that the organisms become attached to the sand-grains near the surface and are carried to the bottom of the tank during the process of washing, where they become dislodged. The presence of a few microscopic organisms in the effluent of a mechanical filter, therefore, does not necessarily indicate a very imperfect filtration.
Occasionally growths of Crenothrix and allied species occur in the under-drains of sand filters. They usually appear where the conditions are such that the water is deprived of part of its oxygen, or where, through leakage, ground-water, containing iron and carbonic acid in solution becomes mixed with the filtered water.
Growths of microscopic organisms often occur in filtered water when exposed in open reservoirs to the sunlight, as described in Chapter XV.
Dr. Marsson's Investigations. — One of the most interesting descriptions of the relation of the various classes of microscopic organisms to each other and to their environment is that given by the late Dr. Maximilian Marsson who for many years was connected with the Royal Testing Station for Water Supply and Sewage Disposal at Berlin, Germany. An excellent transla- tion of one of Dr. Marsson's lectures, made by Emil Kuichling may be found in the Engineering News for Aug. 31, 191 1. The lecture is entitled *'The Significance of Flora and Fauna in Maintaining the Purity of Natural Waters."
82 THE MICROSCOPY OF DRINKING WATER
Importance of the Biological Balance. — ^Although the sub- ject of stream pollution and self -purification is not a part of the subject of this book, it is well for the reader to understand the importance of maintaining a proper balance of animal and plant life in rivers and lakes. The author believes that ulti- mately the great question of the permissible limit of stream pollution will be solved on this basis. Dr. Marsson's lecture above mentioned is well worth reading in this connection.
Potamology. — ^This science remains to be developed. It will include the physical, chemical and biological studies of the waters of streams, the inter-relations of the various organisms and the effect of changing environment upon them. It will do for running waters what limnology is doing for the more quiet waters of reservoirs and lakes.
CHAPTER VII LIMNOLOGY
Limnology is that branch of science that treats of lakes and ponds — their geology, their geography, their physics, their chemistry, their biology, and the relations of these to each other. This subject has taken shape only within the past twenty-five years, but already a vast number of valuable publications has appeared.
In this and the next chapters only such limnological studies as are closely related to the microscopic organisms will be con- sidered. The most important of these are: the movements of the water, the temperature of the water at different depths, the amount of light received and transmitted by the water, and the food material of the organisms found in the water. The location of lakes, their shape, size, and depth, the source of their supply, the character of the watershed, the meteorology of the region, all have their effect upon the organisms living in the water, but they can be considered only incidentally.
Physical Properties of Water. — The density of water varies with its pressure, with its temperature, and with the substances dissolved in it.
Grassi gives the coefficient of compressibility of pure water as .0000503 per atmosphere at 0° C, and .0000456 at 25° C. Therefore if the density at the surface of a lake is unity, at a depth of 339 ft. (10 atmospheres) it will be 1.0005; at 678 ft. (20 atmospheres), i.ooi; and at 1017 ft. (30 atmospheres), 1.0015.
Water attains its maximum density at about 4° C. or 39.2° F. Assuming its density at 4° C. to be unity, its density at other temperatures is given in the following table.
83
84
THE MICROSCOPY OF DRINKING WATER
DENSITY OF WATER AT DIFFERENT TEMPER.\TURES.
|
Temperature. |
T> |
t . |
Temperature. |
T\ |
• A |
||
|
Centigrade. |
Fahrenheit. |
Densuy. |
Centigrade. |
Fahrenheit. |
Denniy. |
||
|
O'' 1.6 4.0 4-4 7.2 10. 0 12.7 155 |
32. o** 350 39-2 40.0 450 50.0 550 60.0 |
I |
99987 99996 .00000 99999 99992 99975 99946 99907 |
i8.3' 21. I 23.8 26.6 29.4 32.2 350 37-7 |
65.0° 70.0 750 80.0 85.0 90.0 95 0 100. 0 |
99859 99802 99739 99669 99592 99SIO 99418 99318 |
Water freezes at o® C, or 32.0** F. Ice is lighter than water, floats in water at 0° C.
It readily
Water has a very high specific heat. It is a poor thermal conductor. Prof. W. H. Weber * gives its coefficient of con- ductivity as 0.0745.
Water is extremely mobile. This property renders it sub- ject to displacement by mechanical agencies, such as wind and currents (mechanical convection), and permits it to become stratified according to the density of its particles.
The viscosity of water has an important influence on micro- scopic organisms, as it materially affects their flotation. It also affects the sedimentation of fine particles in water and even the circulation of the water itself. Viscosity varies with the temperature. It is twice as great near the freezing-point as at ordinary summer temperatures. This is shown by the table on page 85.
When water is stratified with the warmer layers above the colder, the stratification is said to be " direct." This occurs when the temperatures are above that of maximum density. When water is stratified with the colder layers above the warmer the stratification is said to be " inverse.'' Tliis occurs when the temperatures are below that of maximum density. With the temperatures above 39.2° it sometimes happens in a deep lake that a colder layer of water is found above a warmer layer.
* Vicrteljahreschrift der Zurich Nat. Cos., xxiv. 252, 1879.
LIMNOLOGY
85
VISCOSITY OF DISTILLED WATER AT DIFFERENT TEMPERATURES.
|
Temperature (C.) |
Viscosity Coefficient (Dynes per |
Percentage of Viscosity at o«»C. |
|
Sq. Centimeter). |
||
|
o'' |
0.017780 |
100. 0 |
|
5 |
0.015095 |
84.9 |
|
lO |
0.013025 |
73-2 |
|
IS |
O.OII425 |
64.2 |
|
20 |
O.OIOOI5 |
S6.3 |
|
25 |
0.008910 |
SO. I |
|
30 |
0.007975 |
44.8 |
|
35 |
0.007200 |
40. s |
|
40 |
0.006535 |
36.8 |
|
SO |
0.005475 |
30.8 |
|
66 |
0.004680 |
26.3 |
|
70 |
0.004060 |
22.8 |
|
80 |
0.003560 |
20.0 |
|
90 |
0.003155 |
17.7 |
|
100 |
0.002830 |
IS 9 |
This is a paradox theoretically possible, because the density of the water at any point in a lake depends upon its depth as well as its temperature. Thus water at 45° F. has a density of .99992. If this water were at a depth of 1017 ft., where the pressure is 30 atmospheres its density would be .99992 +.001 5 = 1.00142, i.e., more than that of water at 39.2° F. at the sur- face. In nature, however, such a condition of temperatures seldom exists for a long period, and practically represents a state of imstable equilibrium. A thermal paradox may be caused also by differences in the density of different strata due to sub- stances in solution.
Water has a slight power of diathermancy, i.e., it permits the penetration of radiant heat to a slight degree. Forel experimented on the diathermancy of water by comparing the readings of thermometers with blackened and with ordi- nary bulbs at a depth of i meter. He obtained the results foimd in the table on page 86.
Lake Thermometry. — The observation x)f the temperature of the water at the surface of a lake is a comparatively easy matter, but it requires an accurate thermometer and a careful observer. Where the water is smooth the thermometer-bulb
86
THE MICROSCOPY OF DRINKING WATER
TEMPER.\TURE OBSERVATIONS ILLUSTRATING DIATHERMANCY
|
Date. |
Time of Bxposxire. |
Temperature of Water. (Fahrenheit.) |
Bxceas of Temperature of Black Bulb Ther- mometer, in Pahr. Deg. |
|
Mar. 27, 1871.. . . July 25, 1873 July 26, 1873 Aug. 1, 1873 |
10 hours 17 ** IS ** 12 ** |
44 4* 72.0 74.3 75-2 |
10. 8* 14.0 153 7.6 |
may be immersed just beneath the surface in an inclined posi- tion and the reading taken removing it from the water. In taking the reading one must be careful to avoid parallax by holding the thermometer exactly at right angles to the line of sight. When the water is too rough for reading directly some of the surface-water may be dipped up and the temperature of that ascertained. Thermometers with bulb immersed in a cup are prepared for this purpose. Direct observations are much to be preferred.
The best thermometer for general use is a " chemical thermometer," that is one with a cylindrical bulb and graduated directly on the stem. A good length is 9 inches. The most convenient range is from 20° to 120® F., and the graduations should be to the nearest half degree. If the Centigrade scale is used the range may be from 5° to 40"^ and the graduations to the nearest fifth of a degree. To protect against breakage the thermometer may be mounted in a wooden case as shown in Fig. 35. If weighted, this may be put inside a bottle and used to obtain sub-surface temperatures.
Sub-surface Temperatures. — ^The observa- tion of the temperature of the water at depths below the surface is more difficult.
Lead
Fig. 35. — Weighted Case for Holding a Thermometer.
LIMNOLOGY 87
The simplest method of obtaming results that are in any way accurate is to enclose a weighted thermometer in a stoppered empty bottle and to lower this to the proper depth and fill it by drawing out the stopper. After allowing a sufficient time for the apparatus and thermometer to acquire the exact tem- perature of the water the bottle is drawn to the surface and the reading taken before the thermometer is removed from the bottle. If the bottle is of sufficient size, if it is allowed to remain down long enough, if it is drawn rapidly to the surface and the reading taken at once, the error ought not to exceed one degree Fahrenheit. This method is impracticable for lakes much deeper than so ft., and beyond that depth some form of deep-sea thermometer is necessary. Several forms of maximum and minimum thermometers and of self-setting thermometers have been devised. The Negretti and Zambra thermometers have been used extensively for obtaining the temperature of very deep water. Several forms of electrical thermometers have been suggested, but the thermophone invented by H. E. Warren and George C. WTiipple is one that has proved of great practical value. Dr. Howard T. Barnes, of McGill University, has also devised a serviceable instrument.
The Thermophone. — ^The thermophone (see Fig. 36) is an electrical thermometer of the resistance type. It is based upon the principle that the resistance of an electrical conductor changes with its temperature and that the rate of change is different for different metals. Two resistance-coils of metals that have different electrical temperature-coefficients, as copper and German silver, are put into adjacent arms of a Wheatstone bridge and located at the place where the temperature is desired, the two coils being joined together at one end. The other extremities of the coils are connected by leading wires to the terminals of a slide-wire which forms a part of the indicator. A third leading wire extends from the junction of the two coils to a movable contact on the slide-wire, having in its cir- cuit a telephone and a current-interrupter — the latter operated by an independent battery connection. The telephone and interrupter serve as a galvanometer to detect the presence
88 THE MICBOSCOPY OP DRINKING WATER
of a current. The slide-wire is wound around the periphery of a mahogany disk, above which there is another disk carry- ing a dial graduated in degrees of temperature. The movable contact which bears on the slide-Â¥vire b attached to a radial ann placed directly under the dial-hand, the two being moved
Fiu. 36. — Thermophone.
together by turning an ebonite knob in the center of the dial. This indicator is enclosed in a brass case in a box that also contains the batteries. The sensitive coils are enclosed in a brass tube of small diameter which is filled mth oil, hermetically sealed, and coiled into a helix. Connections with the leading wires are made in an enlargement at one end. The leading wires are three in number and are made to form a triple cable.
LIMNOLOGY 89
The temperature of the leading wires does not affect the read- ing of the instrument because two of them are of low resistance and are on opposite sides of the Wheatstone bridge. They neu- tralize each other. The third leading wire is connected with the galvanometer and does not come into the equation. The read- ings of the instnmient are independent of pressure.
The operation of taking a reading is as follows: The coil is lowered to the depth where the temperature is desired, the three leading wires are connected to the proper binding-posts of the indicator-box, the current from the battery is turned on, the telephone is held to the ear, and the index moved back and forth over the dial. A buzzing soimd will be heard in the telephone, increasing or diminishing as the index is made to approach or recede from a certain section of the dial. A point may be found at which there is perfect silence in the telephone, and at this point the hand indicates the temperature of the dis- tant coil. With thermophones adjusted for atmospheric range, i.e., from —15° to 115° F., readings correct to 0.1° F. may be made. With a smaller range greater sensitiveness may be obtained. It is possible to make thermophones that will read to thousandths of a degree.
Because of its accuracy, because of the ease with which the coil may be placed at any depth from the surface to the bottom of a lake, because of its extreme sensitiveness and rapidity of setting (one minute is sufficient), and because of its portability, the thermophone is better adapted than any other instrument for taking series of temperature observations in lakes at various depths. It has been used for that purpose at depths as great as 400 ft., and it was used by Prof. A. E. Burton in Greenland at much greater depths for obtaining tem- peratures in the crevasses of glaciers.
TexE^erature Changes in a Lake. — The general character of the temperature changes that take place in a body of water are illustrated by Fig. 37, which shows the temperatures at the surface and bottom of Lake Cochituate. The curves are based on a seven-years series of weekly observations, but some irregularities have been omitted for the sake of simplicity.
90
THE MICROSCOPY OF DRINKING WATER
tf one traces the line of surface temperatures, he wQl observe that during the winter the water immediately under the ice stands substantially at 32° F., although the ice itself often becomes much lower than 32° at its upper surface. As soon as the ice breaks up in the spring the temperature of the water be^ns to rise. This increase continues with some fluctuations until about the first of August. Cooling then begins and continues regularly through the autumn until the lake freezes in December. If this curve of surface temperature were com- pared with the mean temperature of the atmosphere for the same period a striking agreement would be noticed, and it would be seen tliat the v(ater temperature is the higher of the two. When the surface is frozen there is no comparison between the air and water tempera- tures. During the spring and early summer, when the water is warming, the water is but slightly warmer than the air,* but drmng the late summer and autumn it is about 5° warmer. The surface temperature of the water fluctuates with the air temperature during the course of the day as well as <m different days. The maximum is usually obtained between 2 and 4 P.M. and the minimum between 5 and 7 A.M. The daily range is seldom greater than 5°, though it may be much more. At the latitude of Boston the maximum surface temperature of the water of lakes during the summer is seldom above 8o°.t
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t A surface temperature at 92° w.is obscncd by the author at Chestnut Hill keservoir on Aug. u, iSgb, at ^ I'.u., allw a weolt of eitessively hot weather, during which the maximum daily temperature remained above 90°, while the ■' ' • " ._[■At the time • ' ■.....
humidity varied from 61%
le of the observation the air t(
LIMNOLOGY 91
In small shallow ponds the surface temperature follows the atmospheric temperature much more closely than in large deep lakes where the water circulates to considerable depths. Li the latter the surface temperature is often below that of the mean atmospheric temperature during the early part of the summer, and occasionally during the entire summer.
Lake Cochituate is 60 ft. deep. The temperature at the bottom during the winter, when the surface is frozen, is not far from that of maximum density (39.2° F.). The heaviest water is at the bottom; the lightest is at the top; and the intermediate layers are arranged in the order of their density. With these conditions the water is in comparatively stable equilibrium. It is inversely stratified. It is the period of " winter stagnation."
As soon as the ice has broken up in the spring the surface- water begins to grow warmer. Until it reaches the temperature of maximum density it grows denser as it grows warmer, and tends to sink. Thus until the water throughout the vertical has acquired the temperature of maximum density there are conditions of unstable equilibrium caused by diurnal fluctuations of temperature that result in the thorough mixing of all the water in the lake. These conditions, together with the mechanical effect of the wind, usually cause a slight temporary lowering of the bottom temperature at this season. Finally the tem- perature throughout the vertical becomes practically uniform, and vertical currents are easily produced by slight changes in the temperature of the water at the surface and by the mechanical effect of the wind.
This is the period of " spring circulation " or the " spring overturning." It lasts several weeks, but varies in duration
perature was 95® and the humidity 70%. The temperatures of the water below the surface were as follows:
Surface 92,0® 10 ft 76 . 2®
I ft 91. 5 15" 74.0
2** 89.2 20" 65.7
3** 85.6 25*' 54.5
4** 80.2 27** S3. 1
5'* .790
92 THE MICROSCOPY OF DRINKING WATER
in different years. As the season advances the surface-water becomes warmer than that at the bottom, and finally the dif- ference becomes so great that the diurnal fluctuation of surface temperature and the effect of the wind are no longer able to keep up the circulation. Consequently the bottom temperature ceases to rise, the water becomes " directly stratified," and the lake enters upon the peroid of " summer stagnation." During this period, which extends from April to November, the bottom temperature remains almost constant, and the water below a depth of about 25 ft. remains stagnant. In the autunm the surface cools and the water becomes stirred up to greater and greater depths, until finally the *' great overturning " takes place and all the water is in circulation. At this time there is a slight increase in the bottom temperature that corresponds to the temporary lowering of the temperature in the spring. Then follows the period of '* autumnal circulation," during which the surface and bottom strata have substantially the same tem- perature. In December the lake freezes and " winter stagna- tion " begins.
The use of the thermophone for obtaining series of tem- peratures at frequent interv^als in the vertical enables one to study the temperature changes in more detail, and see how they are affected by the geography of the lake and the meteorology of the region.
Winter Conditions. — In a frozen lake the water in contact with the under surface of the ice stands always at 32° F. The temperature at the bottom varies with the depth and with the meteorological conditions at the time of freezing. In most lakes, and particularly in deep lakes, it stands at the point of maximum density; in shallow lakes it may be lower than that; under abnormal conditions, as referred to on page 52, it may be slightly higher. During the period of winter stagnation the bottom temperature sometimes rises very slightly on account of direct heating by the sun^s rays. This is because of the diathermancy of the water. The temperatures of the water between the surface and the bottom are illustrated by Fig. 38.
The cold water is usually confined to a thin layer — seldom
LIMNOLOGT 98
more than s or lo ft. thick — under the ice, and below that layer the temperature changes but little to the bottom. This is shown by the Lake Cochituate curve. This and the(abnormal) change in the curve at the bottom may be explained as follows: During the period of autumnal circulation the temperature is uniform throughout the vertical. As the weather gets colder the temperature throughout the vertical drops. Until the tem- perature has reached the point of maximum density the circula-
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Fic, 38, — Temperature of Water in Frozen Lakes. After FitzGerald.
tion of the water through the vertical takes place in part by thermal convection; below that temperature it takes place chiefly by wind action. If the wind is not sufficiently strong to induce complete circulation the bottom temperature ceases to fall at 3Q.2**. Thus the bottom temperature at Lake Cochituate in December, 1894, was left at that point. Later the wind stirred the water to a depth of 45 ft., and above that depth the tem- perature became uniform at about 38.5°.
Freezing usually occurs on a cool, still night. The surface-
94 THE MICROSCOPY OP DRINKING WATER
water cools and freezes before the wind has had a chance to mix it with the warmer water below. The suddenness with which a lake freezes and the intensity of the wind prior to freez- ing determine the depth of the layer of cold water, and the tem- perature of the air and the intensity of the wind previous to the time of freezing determine the temperature of the water at the bottom. The Lake Winnipesaukee curve (Fig. 38) represents the effect of a current flowing between two islands. A layer of cold water about 18 ft. thick was flowing over a quiet body of warmer water. The dividing line, at a depth of about 20 ft., was very sharply defined. The Crystal Lake curve (Fig. 38) shows abnormal conditions produced by springs at the bottom of the lake.
Summer Conditions. — During the sunmier the temperature of the water is similarly affected by meteorological conditions. After the ice has broken up, the temperature of the water at all depths rises. Above 39.2° circulation takes place chiefly by the action of the wind. If there were no wind, or if the wind were not sufficient, the temperature at the bottom would not rise above 39.2°. In very deep lakes this happens, but in most lakes the wind causes it to rise somewhat above that point. It continues to rise as long as the difference in density between the water at the surface and at the bottom does not become too great for the wind to keep up the circulation. In Lake Cochit- uate this difference of density is produced by a difference ol about 5° in temperature. When stagnation has once begun the temperature at the bottom changes very little during the summer. It sometimes rises slightly on account of direct heating, as it does in the A^'inter. If warm weather occurs early and suddenly in the spring the required difference of temperature between the upper and lower layers is soon obtained, and consequently the temperature at the bottom through the summer remains low. But if the season advances slowly the bottom temperature will become fixed at a higher point. In Lake Cochituate the bottom temperature varies in different years from 42° to 45°.
The temperatures of the water between the surface and
bottom during the summer may be illustrated by the two typical curves in Fig. 39. Previous to May 13, 1895, the season had progressed gradually. On that day the atmospheric temperature rose to 90° and there was little wind. These con- ditions produced a uniform curve. Then followed several days of cold, windy weather. The surface temperature fell and the water became stirred to a depth of about 17 ft. Below 20 ft., however, there was little change. These conditions usually continue through the summer, the upper layers becoming warmed and stratified or cooled and mixed, the lower layers remaining stagnant.
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Fig. 31
On account of the diurnal changes of the surface temperature due to alternations of day and night, sunshine and clouds, winds and calm, convection currents are almost continuously at work in the upper strata. An increasing surface temperature on a sunny day produces a condition of temporary stratification during the day, which is likely to be followed by a cooling at night which equalizes the temperatures and mixes the water by vertical convection.
The Transition Zone. — Figs. 40 and 41, show the results of temperature observations made at Squam Lake, N. H., during August 1913, by students taking the course in limnology at the Harvard Engineering Camp.
These diagrams show in a striking way that between the upper and lower layers there is a relatively thin layer where the
96
THE MICROSCOPY OF DRINKING WATER
temperature changes rapidly — sometimes io° in one vertical foot. This region has been variously named. In Geimany it is called the " Spningschicht," in Scotland, the " Discontinuity Layer." Dr. Birge has called it the " Thermocline." A
more satisfactory term, the reasons for which will appear later, seems to be the " Transition Zone." The position of the transi- tion zone and the rate of temperature change vary according to the depth of the lake, the intensit;- of the winti, and the temper- <xe of the water above and below. Its upper boundary is
LIMNOLOGY
sometimes very sharp, particularly in the autunin; the lo boundary is less distinct. In the fall the position of transition zone drops toward the bottom as circulation ezte to greater and greater depths.
. Tempenituro
A better conception of the transition zone may be obtained from Fig. 42, which shows the cross-section of a lake as well as the temperature changes. Above the transition zone is the zone of circulation, and below it, the region of stagnation. Dr.
THE MICROSCOPY OF DEINKING WATER
Birge calls the region above the transition zone, or thermocline, the " epiUmnion," and that below it the " hy- polimnion."
Within the drcula- tion zone the water moves horizontally under the influence of the wind, and vertically by con- vection. It is also well aerated and almost de- carbonated. In the stag- nation zone, however, the horizontal currents arc \-Bry slight and the vertical currents negli- gible. Then the condi- tion of the dissolved gases may be reversed, oxygen being depleted or exhausted and carbonic acid increased. Hence the region of rapid tem- perature change is a transition layer in more ways than one, in tem- perature, density, nts- cosit)', movement of the water and conditi(m of the dissolved gases.
Classificatton of Lakei According to Itaaptn.- ture. — Lakes may be divided into three types, according to thdr surface
UMNOLOGY 99
temperatures, and into three orders, according to their bottom temperatures. The resulting nine classes are shown in Fig, 43. On these diagrams the boundaries of the shaded areas represent the limits of the temperature fluctuations at dif- ferent depths. The horizontal scale represents temperatures in Fahrenheit degrees increasing toward the right, and the vertical scale represents depth. The three types of lakes are designated as polar, temperate, and tropical. In lakes of the polar type the surface temperature is never above that of maximiun density; in lakes of the tropical type it is never below that point;
Fig. 43. — Classification of Lakes According to Temperati
in lakes of the temperate type it is sometimes below and some- times above it. This division into types corresponds some- what closely with geographical location.
The three orders of lakes may be defined as follows: Lakes of the first order have bottom temperatures which are prac- tically constant at or very near the point of maximum density; lakes of the second order have bottom temperatures which undergo annual fluctuations, but which are never very far from the point of maximum density; lakes of the third order have bottom temperatures which are seldom very far from the
100
THE MICROSCOPY OP DRINEINa WATER
surface temperatures. The division into orders correqx>nds in a general way to the character of the lakes; i.e., their size, contour, depth, surrounding topography, etc.
The temperature changes which take place in the nine classes of lakes according to this system of classification are exhibited in another manner in Fig. 44. These diagrams show by curves the surface and bottom temperatures for each season of the year, the dates being plotted as absdsse, and
POLAR TYPE
f:r8T order
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TEMPERATE TYPE |
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FIRST ORDER
88.2* «.0*
TROPICAL TYPE
FIRST ORDER
POLAR TYPE
TEMPERATE TYPE
TROPICAL TYPE
SECOND ORDER
30.2" 32.0"
SECOND ORDER
89.2* 82.0*
SECOND ORDER
POLAR TYPE
TEMPERATE TYPE
TROPICAL TYPE
""^ >er^
8B.2* 82.0*
THIRD ORDER ""'^ THIRD ORDER THIRD ORDER
Fig. 44. — Classification of Lakes According to Temperature.
the temperatures as ordinates. The shaded areas show the difTerence between the surface and bottom temperatures, the wider the shaded area the greater being the difference.
A study of these diagrams brings out some interesting facts concerning the phenomena of circulation and stagnation. In Fig. 43 it will be seen that the circulation periods occur when the curve showing the temperatures at various depths becomes a vertical line; that is, when all the water has the same tem- perature. The stagnation periods are shown by the line being
LIMNOLOGY 101
curved, the top to the right when the wanner layers are above the colder, and to the left when the colder layers are above the warmer. In Fig. 44 the circulation periods are indicated by the surface and bottom temperature curves coinciding, and the stagnation periods by these lines being apart. The distance between the lines indicates, to a certain extent, the difference in density between the top and bottom layers, and we see that the farther apaft the lines become the less likelihood there is that the water will be stirred up by the wind.
In lakes of the polar type there is but one opportunity for vertical circulation, except in the third order; namely, in the sxmimer season, when the water approaches the temperature of maximum density. In a lake of the first order, that is, in one where the bottom temperature remains constantly at 39.2°, the circulation period would be very short indeed, if not lacking altogether. In a lake of the second order circulation might and probably would continue for a longer period. In a lake of the third order the water would be in circulation nearly all the time except when frozen. The minimum temperature limit indicated for this order, i.e., 32° at all depths, would be possible only in very shallow bodies of water, and would simply indicate that all the water was frozen. The temperature of the ice would probably be below 3 2 ° at the surface. It is probable that very few polar lakes exist.
In lakes of the tropical type there is likewise but one period of circulation each year, except in the third order. This would occur not in summer, but in winter. In the first order this circulation period would be brief or entirely wanting; in the second it would be of longer duration; in the third order the water would be liable to be in circulation the greater part of the year. Tropical lakes are quite numerous, but observations are lacking to place them in their proper order.
Most of the lakes of the United States belong to the tem- perate type. In this type there are two periods of circulation and two periods of stagnation except in the third order, as we have seen illustrated in the case of Lake Cochituate. In lakes of the first order the circulation periods would be very
102
THE MICROSCOPY OF DRINKING WATER
short or entirely wanting; in the second order the circulation periods would be of longer duration; in the third order the water would be in circulation throughout the year when the surface was jiot frozen. The above facts may be recaptiulated in tabular form as follows:
CIRCULATION PERIODS.
|
Polar Type. |
Temperate Type. |
Tropical Tjrpe. |
|
|
First Order. |
One circulation period possible, in summer, but generally none. |
Two circulation periods possible, in spring and fall, but gener- ally none. |
One drcuktion period poasible, in winter, but |
|
Second Order. |
One circulation period, in sum- mer. |
Two circulation periods, in spring and autumn. |
One circulation period, in win- ter. |
|
Third Order. |
Circulation at all seasons, except when surface is frozen. |
Circulation at all seasons, except when surfaxre is frozen. |
Circulation at all seasons. |
Speaking in very general terms, one may say that lakes of the first order have no circulation, lakes of the third order have no stagnation, except in winter, and lakes of the second order have both circulation and stagnation.
In view of the comparatively few series of observations of the temperature of our lakes, the author refrains from making any classification of the lakes of the United States, but the resuUs thus far obtained seem to indicate that the first order will include only those lakes more than about two himdred feet in depth, such, for instance, as the Great Lakes, Lake Champlain, etc.; the second order will include those with depths less than about two hundred feet, but greater than about twenty-five feet; and the third order will include those with depths less than twenty-five feet. These boundaries are only approximate, and it should be remembered that depth is not the only factor which influences the bottom temperature.
Stagnation is sometimes observed in small artificial reser-
LIMNOLOGY 103
voirs even when the depth is less than twenty feet. It is usually of short duration.
Horizontal Currents. — The most important horizontal cur- rents in a lake or reservoir are those induced by the wind. As the moving air impinges upon the surface of the water it causes the water to move in the same direction. The ratio of the velocitv of the surface-water to that of the air has been shown by experiment to be in the vicinity of s per cent in the case of a large lake like Erie. In a small lake it is less than this. Exper- iments made at Owasco Lake, N. Y., by Ackermann showed that the percentage which the surface-water movement was of the air movement decreased as the wind velocity increased, being about 3 per cent for a wind velocity of 5 miles per hour, and about I per cent for a wind velocity of 30 miles per hour. Of course the actual movement of the surface-water was greater with the higher wind velocity. According to the Owasco Lake experiments a wind velocity of 5 miles per hour would cause the surface-water to move at the rate of about 13 ft. per minute, while a 30-mile breeze would cause a water movement of 26 ft. per minute. While the direction of the surface-water move- ment is about the same as that of the wind it is not always so. In small lakes the surrounding topography and the vary- ing contours of the lake bottom influence the movements of the water.
As the surface-water travels the water beneath the surface is carried along with it, but at a slower rate, the velocity decreas- ing with the distance below the surface. Thus at Owasco Lake, the velocity at a depth of 10 ft. was about 60 per cent of the surface velocity, and at 20 ft., 25 per cent of the surface velocity.
Undertow Currents.— As the water in the upper strata is driven toward the windward shore it raises the level there and the increased head causes return currents at depths below the surface. These are known as undertow currents. They are well known to exist at bathing beaches, but it is not so well known that they extend for long distances from the shore. These return currents are especially marked when the wind
104 THE MICROSCOPY OF DRINKING WATER
drives the surface-water into a cove where the only chance for the water to return is below the surface. In large open lakes where there are jutting points the surface-water approaching a shore may be deflected and return as eddy currents at the surface.
The nature of the circulation of the water induced by the wind may be illustrated by a generalized summary of float experiments made at Squam Lake by the Harvard class in limnology in 191 3. Fig. 45, shows how floats very near the surface drifted with the wind, while the deeper floats went in the opposite direction. It was found that the greater part of the return circulation was above the transition zone, but that even below the transition zone there was some movement of the water. When the bottom water is spoken of as stagnant, therefore, it must be understood that this term is not absolutely accurate.
Shearing Plane. — ^Within the zone of circulation there is a plane which divides the upper currents which follow the wind from the return currents. At this plane a float has almost no motion. The depth of the shearing plane depends to a con- siderable extent upon the depth of the upper boundary of the trajisition zone, but it is also influenced by the contours of the bottom of the lake, and by other factors. As the wind velocity increases, more and more water is carried with the surface-water in the direction of the wind, and the stagnant layers are more and more affected by the return currents.
With high winds the upper boundary of the transition zone is more distinct than with light winds.
Effect of Horizontal Currents. — The surface currents induced by the wind and the accompanying undertow currents have a very important influence on the lake as an environment for growths of microscopic organisms. By continually carrying surface-water downward at the windward shore oxygen is carried to the water of the underlying strata, while conversely carbonic acid may be carried upward and liberated at the sur- face. The plankton themselves may be carried with the mov- ing waters, while the currents flowing over shallow areas may
LIMNOLOGY
105
106 THE MICROSCOPY OF DRINONO WATEB
pick up the spores, or seeds, of organisms and distribute them widely throughout the lake. This is the principal reason for the rapid seeding of a reservoir. It will be shown later that certain organisms tend to concentrate in the transition zone just below the region of the actively circulating water.
Seiches. — After a strong wind has been blowing in one direction for a considerable time and then subsides, the water which has been piled up at the windward end falls to and below its normal level. This is accompanied by a rising of the water at the lee end of the lake. Then the water on the lee falls, while that on the windward rises. These synchronous risings and fallings of the water give rise to the phenomenon known as the " seiche " (pronounced sSsh). The amplitude of the sdche vibrations may vary all the way from a few hundredths of an inch to several feet, but it is only in very large lakes that the latter are observed. The time of oscillation is fairly constant for any particular lake. One authority has given the following formula, which, while not accurate, illustrates the nature of the factors involved.
2/
3600 Vrfg'
where / = time of oscillation in hours.
/ = length of the lake (or width in the case of transverse
seiches) in feet. d = mean depth in feet of lake along the axis of observa-
tion. g = acceleration of gravity (32.16).
This formula applied to Lake Erie gave a calculated seiche period of 14.4 hours, while the observed periods have ranged from 14 to 16 hours.
Other causes than the wind may produce seiches, such as sudden and unequal changes of barometric pressure at opposite ends of a lake, and sudden rainfalls at one end of a lake. Seiches are of less importance to the sanitary engineer than are the horizontal currents that accompany them.
LIMNOLOGY 107
Transmission of Light by Water. — The amount of light received by the micro-organisms in a lake depends upon the intensity of the light at the surface of the water and upon the extent to whiclj the light is transmitted by the water. The transmission of light by water varies chiefly with the amount of dissolved and suspended matter that it contains. The former aflfects its coeflSdent of absorption; the latter acts as a screen to shut out the light. In studying the penetration of light into a body of water it is necessary to take account of its color and its turbidity. Dr. H. C. Jones says that salts like the chlorides of calciiun and magnesium which combine with large amounts of water in aqueous solution diminish the absorption of light.
Color of Water. — Some surface-waters are colorless, but in most ponds and lakes the water has a more or less pronounced brownish color. This may be so slight as to be hardly per- ceptible, or it may be as dark as that of weak tea. It is darkest in water draining from swamps, and the color of the water in any pond or stream bears a close relation to the amount of swamp- land upon the tributary watershed. The surface water in granite regions is generally darker than in regions of shale or slate.
The color is due to dissolved substances of vegetable origin extracted from leaves, peaty matter, etc. It is quite as harm- less as tea. The exact chemical nature of the coloring matter is not known. It is complex in composition. Tannins, gluco- sides, and their derivatives are doubtless present. The color of a water usually bears a close relation to the albuminoid anmionia present. Carbon, however, is the important element in its composition. The color of a water varies very closely with the " oxygen consumed." Iron is present, and its amount varies with the depth of the color. In some waters iron alone imparts a high color, but in peaty vaters it plays a subsidiary part. Manganese may also play a part.
The color of a water is usually stated in figures based on comparisons made with some arbitrary standard, the figures increasing with the depth of the color. The Platinum-Cobalt Standard, the Natural Water Standard, and the Nessler Standard
108
THE MICROSCOPY OP DRINEINO WATER
are those which have been most commonly used. The first is now the accepted standard. Comparisons of the water with the standard may be made in tall glass tubes or in a colorim- eter such as that used at the Boston Water Works.*
For field-work a color comparator, by which the color of the water is compared with disks of colored glass, is very use- ful. The water is placed in a metallic tube with glass ends and its color compared with a second tube containing distilled water and with one end covered with one or more of the glass disks. This apparatus, devised for the United States Geologoical
mm
Fig. 46. — U. S. Geological Survey Apparatus for Measuring the Color of Water.
Survey by Dr. Allen Hazen and the author, is illustrated in Fig. 46.
The amount of color in the water collected from a water- shed has a seasonal variation. This may be illustrated by the color of the water in Cold Spring Brook, at the head of the Ashland Reservoir of the Boston Metropolitan Supply. This brook is fed in part from several large swamps. The figures given are based on weekly observations.
♦See FiuGerald and Foss, "On the Color of Water," Jour. Erank. Inst., Dec. 1894.
LIMNOLOGY 109
AVERAGE COLOR OF WATER IN COLD SPRING BROOK, 1894.
Jan. Peb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov. Dec. Av. 99 88 96 93 142 159 98 75 60 69 144 120 104
There are usually two well-defined maxima, one in May or June and one in November or December. In the winter and early spring the color of the water is low because of dilution by the melted snow. As the yield of the watershed diminishes the color increases until the water standing in the swamp areas ceases to be discharged into the stream. During the summer the water in the swamps is high-colored, but its effect is not felt in the stream until the swamps overflow in the fall. Heavy rains during the summer may cause the swamps to discharge and increase the color of the water in the reserv'oirs below. It has been found that in general the color of the water delivered from any watershed bears a close relation to the rainfall. In some localities this is more noticeable than in others. In Massapequa Pond of the Brookljn water-supply the color varies greatly from week to week, and the fluctuations are almost exactly proportional to the rainfall. In large bodies of water the seasonal fluctuations in color are less pronounced.
The hue of the water in the autumn is somewhat different from that in the spring. The fresh-fallen leaves and vegetable matter give a greenish-brown color that is quite different from the reddish-brown color produced from old peat.
Bleaching. — ^When colored water is exposed to the light it bleaches. A series of experiments made at the Boston Water Works by exposing bottles of high-colored water to direct sun- light for known periods showed that during 100 hours of bright sunlight the color was reduced about 20 per cent, and that with sufficient exposure all the color might be removed. The bleaching action was found to be independent of temperature. Sedimentation had but little influence on it. It was depend- ent entirely upon the amount of sunlight. The percentage reduction was independent of the original color of the water.
This bleaching action takes place in reservoirs where col- ored water is stored. Stearns has stated that in an unused reservoir 20 ft. deep the color of the water decreased from
110
TlIE MICROSCOPY OF DRINKING WATER
40 to 10 in six months. In the Ashland reservoir referred to, the average color of the water ir. the influent stream for the year 1894 was 104. For the same year the average color of the water at the lower end of the basin was 71. It should be stated that this difference is not due wholly to bleaching action. The amount of coloring-matter entering the reservoir is not cor- rectly shown by the figure 104, for the reason that the quantity of water flowing in the stream b not uniform. It is greatest in the spring when the melting snows give the water a color lower than the average. Furthermore, some colorless rain- water and ground-water enters the basin. There is also a loss of high-colored water at the wasteway at a season when the color of the water is above the average. It is a difficult matter to ascertain just the amount of bleaching action that takes place in a reservoir through which water is constantly flowing.
Experiments (by the author) made by exposing bottles of colored water at various depths in reservoirs have shown that the bleaching action that takes place at the surface of a reservoir is considerable, sometimes 50 per cent in a month. It decreases rapidly with increasing depth, and the rapidity with which it decreases below the surface depends upon the color of the water in the reservoir, as the following table will show:
EXPERIMENTS TO DETERMINE THE AMOUNT OF BLEACHING
ACTION AT DIFFERENT DEPTHS.
20
Color of water in reservoir. . . .
Time of exposure ' Aug. 6-Sept. 4
Expt. No. I.
Color of water exposed
PercentaRe reduction of color: At depth of 0.0 ft
0.5 "
<<
< I
I (
< (
I (
I f
K
(<
( (
( (
1.25"
25
7 5 10. o
15 o
( (
( (
( I
1 1
n
Dark room
175
65%
32,0 21% â– 4%
3 /o 1 .0
0%
Expt. No. 2.
37 May 5-June 4
272
52%
29% or/
4% 4% 0%
0% 0% 0%
Expt. No. 3.
44 July 2-Aug. 3, 170
41% 20%
12% 4% 3% 0% 0% 0% 0%
LIMNOLOGY 111
From these and many similar experiments it has been found possible to calculate the extent of the bleaching action that takes place m any reservoir. The results agree closely with the observed color-readings of the water in the reservoir. The experiments also bear directly upon the penetration of light into the water of a reservoir.
Turbidity of Water. — The turbidity of water is due to the presence of particles of matter in suspension, such as clay, silt, finely divided organic matter, and microscopic organisms.
There are three principal methods used for measuring tur- bidity which give fairly comparable results. These are: i. Comparison with silica standards. 2, Platinum- wire method. 3, Turbidimeter method. In all cases the results of the observa- tions are expressed in numbers which correspond to turbidities produced by equivalent amounts of finely-divided silica in parts per million.
The standard of turbidity has been defined by the U. S. Geological Survey as follows:
" The standard of turbidity shall be a water which contains ICO parts of silica per million in such a state of fineness that a bright platinum wire i millimeter in diameter can just be seen when the center of the wire is 100 millimeters below the surface of the water and the eye of the observer is 1.2 meters above the wire, the observation being made in the middle of the day, in the open air, but not in sunlight, and in a vessel so large that the sides do not shut out the light so as to influence the results. The turbidity of such water shall be 100."
The most convenient method for Hmnological field-work is the platinum-wire method. This method requires a rod with platinum wire of a diameter of one mm. or 0.04 inch, inserted in it about one inch from the end of the rod and projecting from it at least one inch at a right angle. Near the end of the rod, at a distance of 1.2 meters (about four feet) from the platinum wire, a wire ring is placed directly above the wire, through which, with his eye directly above the ring, the obsers-er looks down- ward in making the examination. The rod is graduated as follows:
112
THE MICROSCOPY OF DRINKINa WATER
The graduation mark of loo is placed on the rod at a distance of loo mm. from the center of the wire. Other graduations are made according to the table on p. 113, which is based on the best obtainable data and in which the distances are intended to be such that when the water is diluted the turbidity reading will decrease in the same proportion as the percentage of the original water in the mixture. These graduations are those used to construct what is known as the U. S. Geological Survey Turbidity Rod of 1902. (See Fig. 47.)
Fin. 47— U. S. Geological Survey Turbidity Rod.
Procedure. — "Push the rod vertically down into the water as far as the wire can be seen, and then read the level of the surface of the water on the graduated scale. This will indicate the turbidity."
The following precautions should be taken to insure correct results:
" Observations should be made in the open air, preferably in the middle of the day and not in direct sunlight. The wire should be kept bright and clean. If for any reason observations cannot be made directly under natural conditions a pail or tank may be filled with water and the observation taken in that,
LIMNOLOGY
113
but in this case care should be taken that the water is thoroughly stirred before the observation is made, and no vessel should be used for this purpose unless its diameter is at least twice as great ^s the depth to which the wire is immersed. Waters which have a turbidity above 500 should be diluted with clear water, before the observations arc made, but in case this is done the degree of dilution used should be stated and form a part of the report."
GRADUATION OF TURBIDITY ROD
|
Turbidity. Parts per Million. |
Vanishing Depth of W^ire, mm. |
Turbidity. Parts per Million. |
Vanishing Depth of Wire. mm. |
Turbidity, Parts per Million. |
Vanishing Depth of Wire, mm. |
|
7 |
lOQS |
28 |
314 |
120 |
86 |
|
8 |
971 |
30 |
296 |
130 |
81 |
|
9 |
873 |
35 |
257 |
140 |
76 |
|
10 |
794 |
40 |
228 |
150 |
72 |
|
II |
729 |
45 |
205 |
160 |
68.7 |
|
12 |
674 |
50 |
187 |
180 |
62.4 |
|
13 |
627 |
55 |
171 |
• 200 |
57.4 |
|
14 |
587 |
60 |
158 |
250 |
49.1 |
|
IS |
SS^ |
65 |
147 |
300 |
43.2 |
|
16 |
520 |
70 |
138 |
350 |
38.8 |
|
17 |
493 |
75 |
130 |
400 |
35.4 |
|
18 |
468 |
80 |
122 |
500 |
30.9 |
|
19 |
446 |
85 |
116 |
600 |
277 |
|
20 |
426 |
90 |
no |
800 |
23.4 |
|
22 |
391 |
95 |
105 |
1000 |
20.9 |
|
24 |
361 |
100 |
100 |
1500 |
17. 1 |
|
26 |
336 |
no |
93 |
2000 |
14.8 |
|
3000 |
12. 1 |
For very clear waters the use of a black-and-white disk, as suggested later, will be found more satisfactory than that of the platinum wire.
Transparency of Water. — The transparency of water pro- foundly influences the intensity of light at different depths and hence has a marked effect on the growth of algae. To compare extreme cases we observe that when very clear waters, such as ground-waters, are exposed to the light in open reservoirs algae grow abundantly, but that plant life is very meager in the water and along the shores of the silt-laden streams of the Middle West, such as the Mississippi and the Ohio rivers.
114 THE MICROSCOPY OF DRINKING WATER
Some light is absorbed by all waters, even distilled water, but the amount of light absorbed decreases as the suspended mat- ter held by the water increases. As muddy waters become clarified on standing the growths of organisms tend to increase. The most complete studies of the transparency of large bodies of water were those made by Forel and others in Switzer- land. Three methods of experiment were employed. The first was that of the visibility of plates. This method, used by Secchi in 1865 in determining the transparency of the water in the Mediterranean Sea, consisted of lowering a white disk (20 cm. in diameter) into the water and noting the depth at which it disappeared from view, and then raising it and noting the point at which it reappeared. The mean of these two depths was called the limit of visibility. The second method^ known as that of the Genevan Commission, was similar to the first, but instead of a white disk an incandescent lamp was lowered into the water. This light when seen through the water from above presented an appearance similar to that of a street-lamp in a fog; that is, there was a bright spot surrounded by a halo of diffused light. When the light was lowered into the water the bright spot first disappeared from view. The depth of this point was noted as the " limit of clear vision." Finally the diffused light disappeared, and the depth of this point was called the ** limit of diffused light." Both these methods were useful only in comparing the relative transparency of different waters or of the same water at different times. In order to get an idea of the intensity of light at different depths a photographic method was used. Sheets of sensitized albumen paper were mounted in a frame in such a way that half of the sheet was covered with a black screen, while the other half was exposed. A series of these papers was attached to a rope and lowered into the water; they were equidistant and so supported that they assumed a horizontal position in the water. They were placed in position in the night and allowed to remain 24 hours. On the next night they were drawn up and placed in a toning-bath. A comparison of prints made at different depths enabled the observer to determine the depth at which the light
LIMNOLOGY
115
ceased to affect the paper and to obtain an idea of the relative intensity of the light at different depths. To assist in this comparison an arbitrary scale was made by exposing sheets of the same paper to bright sunlight for different lengths of time. The results of the experiments are given by Forel as follows: In Lake Geneva the limit of visibility of a white disk 20 cm. in diameter was 21 m. The limit of clear vision of a 7- candle-power incandescent lamp was 40 m. ; the limit of diffused light was about 90 m. The depth at which the light ceased to affect the photographic paper was 100 m., when the paper was sensitized with chloride of silver, and about 200 m. when sen- sitized with iodobromide of silver. These depths were less in summer than in winter on account of the increased tur- bidity of the water. The transparency of the water in other lakes, as shown by the limit of visibility of a white disk, is cited as follows: Lake Tahoe, 33 m.; La Mer des Antilles, 50 m. ; Lac Lucal, 60 m.; Mediterranean Sea, 42.5 m.; Pacific Ocean, 59 m. It should be remembered that these are all com- parativelj'^ clear and light-colored waters, and that in them the light penetrates to far greater depth than in turbid and colored water. For example, in Chest- nut Hill reservoir, a disk lowered into the water at a time when the color was 92 disappeared from view at a depth of six feet.
The author's experiments have shown that the limit of visibility may be determined most accurately by using a disk about 8 inches in diameter, divided into quadrants painted alternately black and white like the target of a level-rod, and looking vertically down upon it through a water-telescope
Welffh<
Fig. 48. — Disk for Compar- ing the Transparencies of the Water in Different Lakes.
116 THE MICROSCOPY OF DRINKING WATER
provided with a suitable sunshade. It has been found that the limit of visibility obtained in this manner bears a dose relation to the turbidity of the water as determined by a tur- bidimeter. It also varies with the color of the water, but the relation has not been carefully worked out.
Absorption of Light by Water. — ^The absorption of light by distilled water is said to var>' with the temperature. The following coefficients are given by Wild as the result of laboratory experiments. It seems probable that the figures are too low-
Temperature.
Intensity of Light after paMing through I dm. of Distilled Water.
24.4° c. 0-9179
17.0 0.93968
6.2 0.94769
The coefficient of absorption of light by colored water is quite unknown.
The reduction of light in passing downward through a body of water is supposed to follow the law that as the depth increases arithmetically the intensity of the light decreases geometrically. For example, if the intensity of the light falling upon the surface of a pond is represented by i, and if J of the light is absorbed by the first foot of water (some colored waters absorb even more than this), then the intensity of light at the depth of I ft. will be J; the second foot of water will absorb i of J, and the intensity at the depth of 2 ft. be A; and so on. At this rate of decrease the intensity of light at a depth of 10 ft will be only about 5 per cent of that at the surface.
Dr. Birge, who has made extensive studies of Lake Mendota, says that at a depth of one meter the solar energy varies in dif- ferent lakes from 2 per cent to 20 per cent of that at the same surface.
There are few accurate data extant regarding the quality of the light at different depths, but theory would lead us to infer that in passing downward from the surface to the bottom of a lake the light varies considerably in character. The red and yellow rays are most readily absorbed by the water.
CHAPTER VIII
DISSOLVED GASES AND THEIR RELATIONS TO THE MICRO- SCOPIC ORGANISMS
The gases dissolved in water exert such an important influence on the growth of the microscopic organisms that they deserve consideration in a special chapter.
Photo-synthesis. — Most of the organisms which are of interest to the water-supply specialist belong to the vegetable kingdom. Algae may be most simply defined as microscopic plants the cells of which contain chlorophyll. By virtue of this substance they have that power of food building by which water and carbonic dioxide are united to form starch and other carbohydrates, energy for the plant thus being stored up. This process, which is known as photo-synthesis, can take place only in the light. In lakes therefore it is confined to the strata relatively near the surface. In turbid water it is limited to depths of a few inches, but in very clear waters it may take place at depths of 25 ft. or more, although at these depths its activity is slight. In photo-synthesis carbonic acid, by which term we mean carbon dioxide, is taken in while oxygen is given out.
Respiration. — Another phase of the life process is summed up in the word respiration, which is common to both animals and plants. By it oxygen is taken in and carbonic acid given out, the released energy appearing as heat and work in the cells. Unlike photo-synthesis the process of respiration goes on in the dark as well as in the light. In the light, however, the respiration of green plants may be masked so far as gas relations are concerned by the greater effects of photo-synthesis. Animal organisms, such as the protoza, rotifers and Crustacea, and the
117
118 THE MICROSCOPY OF DRINKING WATER
fungi, which contain no chlorophyll do not have the photo- synthetic power of food building and hence must consume food already prepared.
Decomposition." Bacteria live upon organic matter, taking in oxygen and giving out carbonic acid. In the absence of dissolved oxygen gas in water they take their oxygen from the organic matter itself, that is they decompose it, giving out not only carbonic acid but also carbon monoxide, methane and other gases. This process has been sometimes called anaerobic respiration, that is respiration without air. It is also known as putrefaction. Decomposition takes place at the bottom of deep lakes where the water lies stagnant for long periods — hence in the stagnant layers there is always a tendency for dissolved oxygen to become depleted and for carbonic add to increase in amount.
Determination of Dissolved Oxygen. — The following descrip- tion of the method of ascertaining the amount of dissolved oxygen in water is taken from the Re[>ort of the Committee on Standard Methods of Water Analysis of the American Public Health Association.
There are three methods in use for the determination of atmospheric oxygen dissolved in water, viz., those of Winkler, Thresh, and Levy. Each of these methods has its own particular field of usefulness. All are capable of giving sufficiently accurate results.
The Winkler method is in the most common use in this country, and i)ossesses the advantage of requiring only simple and not readily breakal)le apparatus. It is therefore rcconmiended as the standard method, and is here described.
The method of Thresh is perhaps slightly more accurate than the Winkler method, but the apparatus is not so well adapted to field work. For certain i>urp()ses, however, as, for example, the determination of dissolved oxygen before and after incubation, it is more practical than the Winkler method because the apparatus allows the taking of representative samples direct from bottles or other containers.
What is true of the disadvantages of the Thresh method
DISSOLVED GASES AND MICROSCOPIC ORGANISMS 119
is also true to a great degree of the Levy method. With both of these methods the samples are taken in a special stoppered, separatory funnel.
"^I^^nkler Method. — Reagents. — i. Manganous sulphate solu- tion: Dissolve 48 grams of manganous sulphate in 100 c.c. of distilled water.
2. Solution of sodium hydrate and potassium iodide: Dis- solve 360 grams of sodium hydrate and 100 grams of potassium iodide in one liter of distilled water.
3. Sulphuric acid. Specific gravity 1.4 (dilution 1:1).
4. Sodium thiosulphate solution. Dissolve 6.2 grams of
chemically pure recrystallized sodium thiosulphate in one liter
N of distilled water. This gives an — solution each c.c. of which
^ 40
is equivalent to 0.2 mg. of oxygen or 0.1395 c.c. of oxygen at
o^ C. and 760 mm. pressure. Inasmuch as this solution is not
permanent it should be standardized occasionally against an
N . . .
— solution of potassium bichromate as described in almost
any work on volumetric analysis. The keeping qualities of the thiosulphate solution are improved by adding to each liter 5 c.c. of chloroform and 1.5 grams of ammonium carbonate before making up to the prescribed volume.
5. Starch solution. Mix a small amount of clean starch with cold water until it becomes a thin paste, stir this into 150 to 200 times its weight of boiling water. Boil for a few minutes, then sterilize. It may be preserved by adding a few drops of chloroform.
Collection of the Sample. — The sample shall be collected with extreme care in order to avoid the entrainment or absorption of any oxygen from the atmosphere. The sample bottle shall be preferably a glass stoppered bottle which has a narrow neck and which holds at least 250 c.c. The exact capacity of the bottle shall be determined and for convenient reference this may be scratched upon the glass with a diamond.
If the sample is to be collected from a tap the water shall be made to enter the bottle through a glass or rubber tube which
120 THE MICROSCOPY OF DRINKING WATER
reaches to the bottom of the bottle, the water being allowed to overflow for several minutes, after which the glass stopper b carefully replaced so that no bubble of air is caught beneath it.
If the sample is to be collected from the surface of a pond or tank two bottles shall be used, the ordinary sample bottle and a second bottle of four times the capacity. Both bottles shall be provided with temporary stoppers of double perforation and in both cases a glass tube shall extend through one hole of the stopper to the bottom of the bottle and a short glass tube shaU enter the other hole of the stopper but not project into the bottle. The short tube of the sample bottle shall be connected with the long tube of the larger bottle. In collecting the sample the sample bottle shall be immersed in the water and suction applied to the short tube of the lafge bottle and enough water drawn through the hole to fill the large bottle. In this way the water in the smaller bottle will be changed several times and a fair sample secured.
If the sample is to be taken at a depth below the surface both bottles may be connected, lowered to the desired depth, and if the smaller bottle is placed beneath the larger one the water will enter the small bottle and pass from that into the larger bottle, the air escaping from the short tube of the large bottle. As soon as the small bottle has been filled remove the temporary stopper and insert the permanent glass stopper using care not to entrain any bubbles of air.
Procedure, — Remove the stopper from the bottle and add 2 c.c. of the manganous sulphate solution and 2 c.c. of the sodium hydrate potassium iodide solution delivering both of these solutions beneath the surface of the liquid by means of a pipette. Replace the stopper and mix the contents of the bottle by shaking. Allow the precipitate to settle. Remove the stopper add about 2 c.c. of sulphuric acid and mix thor- oughly. Up to this point the procedure shall be carried on in the field but after the sulphuric acid has been added and the stopper replaced there is no further change and the rest of the operation may be conducted at leisure. For accurate work there are a number of corrections necessary to be made, but in
DISSOLVED GASES AND MICROSCOPIC ORGANISMS 121
actual practice it is seldom necessary to take them into account as they are ordinarily much less than the errors of sampling.
N
Rinse the contents of the bottle into a flask, titrate with —
40
solution of sodium thiosulphate using a few c.c. of the starch
solution toward the end of the titration. Do not add the starch
imtil the color has become a faint yellow; titrate until the blue
color disappears. If nitrates be present, correction must be made.
Caktdatian of Results, — The standard method of expressing results shall be by parts per million of oxygen by weight.
It is sometimes convenient to know the nimiber of c.c. of the gas per liter at 0° C. temperature and 760 mm. pressure and also to know the percentage which the amount of gas present is of the maximum amount capable of being dissolved by distilled water at the same temperature and pressure. All three methods of calculation are therefore here given.
Oxygen in parts per million
Oxygen in c.c. per liter
0.0002N X 1 ,000,000 200N
0.1395NX1000 I39-5N
200NX100 20000N
Oxygen m per cent of saturation = — yTTTSj — = ''~VC)~
N
Where N =* number of c.c. of — thiosulphate solution.
40
V = capacity of the bottle in c.c. less the volume of the manganous sulphate and potassium iodide solution added (i.e., less four c.c).
0 = the amount of oxygen in parts per million in water satiurated at the same temperature and pressure.
Solubility of Dissolved Oxygen. — The solubility of dissolved oxygen in fresh water varies with the temperature as shown by the following table. These figures are based upon the normal pressure that exists at sea-level, i.e. 760 mm. For elevations above the sea i p>er cent should be deducted for
122
THE MICROSCOPY OF DRINKING WATER
every 270 ft. of elevation. In comparing results expressed in parts per million by weight, i.e., milligrams per liter, it is con- venient to note that i c.c. of oxygen, at normal temperature and pressure weighs 1.4291 mg.
DISSOLVED OXYGEN IN WATER SATURATED WITH AIR AT
DIFFERENT TEMPERATURES.
|
Cubic |
Cubic |
||||
|
Temp. |
Parts per Million. |
Centimeters per liter, («t 0** C. and 760 mm.) |
Temp. |
Parts per MiUion. |
Centimeter* per liter. (at o* C. and 760 mm.) |
|
0 |
14.70 |
10.29 |
16 |
9-94 |
6.95 |
|
I |
14.28 |
9 99 |
17 |
9. 75 |
6.83 |
|
- 2 |
13 88 |
9 70 , |
18 |
9.56 |
6.70 |
|
3 |
13 50 |
9 44 |
19 |
9 37 |
6.56 |
|
4 |
13 M |
9.20 |
20 |
9.19 |
6.44 |
|
5 |
12.80 |
8.95 |
21 |
9.01 |
6.32 |
|
6 |
12.47 |
8.72 |
22 |
8.84 |
6.19 |
|
7 |
12. 16 |
8.50 |
23 |
8.67 |
6.07 |
|
8 |
11.86 |
8.30 |
24 |
8.51 |
5 96 |
|
9 |
11.58 |
8.10 |
25 |
8.35 |
5.8s |
|
10 |
II. 31 |
7.92 |
26 |
8.19 |
S 74 |
|
II |
II .07 |
7-75 |
27 |
8.03 |
5.62 |
|
12 |
10.80 |
7-55 |
28 |
7.88 |
5 S3 |
|
13 |
10.57 |
7.38 |
29 |
7-74 |
5 42 |
|
14 |
10-35 |
724 |
30 |
7.60 |
S 33 |
|
15 |
10.14 |
7 09 |
Determination of Carbonic Acid. — The following description
of the method of ascertaining the amount of dissolved carbonic acid IS taken from the Report of the Committee on Standard Methods of Water Analysis of the American Public Health Association.
Carbonic acid may exist in water in three forms, free car- bonic acid, bicarbonate and carbonate. One-half the carbonic acid as bicarbonate is known as the " half bound carbonic acid.'' The carbonic acid of carbonate plus half that of bicar- l)onate is known as the " bound carbonic acid."
DISSOLVED GASES AND MICROSCOPIC ORGANISMS 123
FREE CARBONIC ACID
N Reagents. — Standard — solution of sodium carbonate.
Dissolve 2.41 grams of dry sodium carbonate in i liter of dis- tilled water which has been boiled and cooled in an atmosphere free from carbonic acid. Preserve this solution in bottles of resistant glass, protected from the air by tubes filled with soda- lime. One c.c. equals i mg. of CO2.
Procedure. — Measure 100 c.c. of the sample into a tall narrow vessel, preferably a 100 c.c. nessler tube, and titrate rapidly
N with the — sodium carbonate solution, stirring gently until
a faint but permanent pink color is produced by phenolphthalein.
N
The number of c.c. — sodium carbonate solution used in
22
titrating 100 c.c. of water, multiplied by 10, gives the parts per million of free carbonic acid as CO2.
Owing to the ease with which free carbonic acid escapes from water, particularly when present in considerable quantities, it is highly desirable that a special sample should be collected for this determination, which should preferably be made on the ground. If the analysis cannot be made on the ground, approxi- mate results from water not high in free carbonic acid may be obtained from samples collected in bottles which are completely filled so as to leave no air-space imder the stopper.
BICARBONATE (HCO3), CARBONIC ACID AS BICARBONATE (CO2)
AND HALF BOUND CARBONIC ACID
When a water is acid to phenolphthalein these three forms are computed as follows, from the alkalinity expressed in terms of calcium carbonate.
Bicarbonate (HC03) = i.22 times the alkalinity.
Carbonic acid (CO2) as bicarbonate =0.88 times the alka- linity.
Half bound carbonic acid = 0.44 times the alkalinity.
124 THE MICROSCOPY OP DRINKING WATER
When the water is alkaline to phenolphthalein, bicarbonates are present only when this alkalinity is less than one-half that by methyl red or erythrosine. Then the bicarbonate alkalinity is equal to the total alkalinity by methyl red or erythrosine minus twice the alkalinity by phenolphthalein. When this difference is expressed in terms of calcium carbonate, the bicarbonate, carbonic acid as bicarbonate, and half-bound car- bonic acid are determined from it by the factors given above.
CARBONATE (CO3), CARBONIC ACID AS CARBONATE (CO2), AND
BOUND CARBONIC ACID
Carbonate is computed as 1.2 times the alkalinity expressed in terms of calcium carbonate, as determined by phenolphthalein.
Carbonic acid as carbonate is computed as 0.88 times the same. Bound carbonic acid is computed as 0.44 times the alkalinity expressed in terms of calcium carbonate as determined by methyl red, lacmoid, or erythrosine.
It should be noted that half-bound carbonic acid is equal to one-half the bicarbonate carbonic acid and that the bound is the sum of the carbonic acid as carbonate and one-half that as bicarbonate.
For the determination of alkalinity the reader is referred to the Report of the Committee on Standard Methods of Water Analysis.
Solubility of Carbonic Acid. — Carbonic acid will dissolve readily in water. The amount that will remain in solution depends upon the partial pressure of CO2 in the atmosphere over the water. In the open air this partial pressure is low, and water exposed to the open air in drops seldom contains more than i or 2 parts per million of free CO2. The air in dug wells often contains a good deal of carbonic acid, so that ground- waters often held very large amounts of this gas.
Carbonic acid has a natural affmity for calcium carbonate and in water will combine with it to form the soluble bicarbonate. In fact, waters become hard only as this action takes place, both limestone and the dissolved gas being necessary.
DISSOLVED GASES AND MICROSCOPIC ORGANISMS 125
SOLUBILITY OF CARBONIC ACID IN WATER.
(Compiled from Sutton's Volumetric Analysis and Fox's paper in the TraiiBactioiiS
of the Faraday Society, September, 1909.)
|
CC. per Liter. |
Parts per Million for Suted Partial Prenores of OOi |
||||
|
in the Atmosphere. |
|||||
|
Temperature, |
— . . |
||||
|
Centigrade. |
|||||
|
X part per |
I part per |
4 parts per |
6 parts per |
Spartsper |
|
|
10,000. |
10.000. |
10.000. |
10.000. |
z 0,000. |
|
|
0 |
.1713 |
•34 |
1.4 |
2.0 |
3.8 |
|
4 |
.1473 |
.29 |
1.2 |
1-7 |
2.4 |
|
8 |
.1283 |
.26 |
I.O |
IS |
3.0 |
|
13 |
.1117 |
.22 |
•9 |
1-3 |
1.8 |
|
16 |
.0987 |
.19 |
.8 |
1.3 |
z.6 |
|
20 |
.0877 |
.17 |
.7 |
1.0 |
3.0 |
|
24 |
.0780 |
IS |
.6 |
.9 |
1.8 |
|
38 |
.0780 |
IS |
.6 |
•9 |
1.8 |
Sources of Oxygen and Carbonic Acid. — ^The principal sources of dissolved oxygen in the water of lakes are the atmosphere and the process of photo-synthesis which lakes place in green plants. The principal sources of dissolved carbonic acid are decomposition of organic matter and the respiration of animals and plants. Only to a slight extent is carbonic acid absorbed from the atmosphere. Sometimes, however, this is an important item. Ground-water usually contains more carbonic acid than surface-water and when this is discharged into a lake it naturally adds carbonic acid to the water.
Carbonic acid also exists in water in loose combination with the carbonates of calcium and magnesium — forming the so- called bicarbonates. In this form the carbonic acid is said to be half-bound. Certain organisms have the power of taking this half-bound carbonic acid away from the bicarbonates and utilizing it, leaving the water slightly alkaline to phenol- phthalein. Such water has the power of taking up carbonic acid from the air more readily than water which is slightly acid to this indicator.
Absorption and Diffusion of Oxygen and Carbonic Acid. — The rate of absorption of oxygen, from the air and its diffusion through water is very slow in still water. To a very con-
126 THE MICROSCOPY OF DRINKING WATER
siderablc extent the absorption is dependent upon mechanical mixture by wave action by currents produced by the winds, by vertical convection currents, and by artificial agitation, such as by boats, etc. These factors however are very important.
The greatest interchange of gases between water and air takes place in the processes of aeration when the water is brought in contact with the air as thin films or as drops.
A Lake as a Closed Community. — Dr. Birge has well said '' The inhabitants of an inland lake form a closed community in a stricter sense, perhaps, than the term can be applied to any other non-parasitic assemblage. The munber of species living under these conditions is small and closely similar in different lakes. Only small additions are made to the food supply from without and these come slowly. The lake is dependent on its own stock of green plants for the stock of organic matter avail- able for food of other organisms; and the possible amount of green plants is limited by the raw material supplied for photo- synthesis from the lake itself. The critical factor then, in the economy of a lake with small in- and outflow of water, is the provision for the vertical circulation of the water in the lake. But this circulation is very imperfectly effected at best, and is often wholly absent for most of the water.
" All of these factors co-operate to produce an annual cycle in the distribution of the dissolvcHl gases, whose fundamental features are the same, but whose details differ endlessly in different lakes.''
Seasonal Changes in Dissolved Oxygen. — It must be remem- bered in the first place that water at a summer temperature — say 20^ C. — holds, when saturated, only five-eighths as much dissolved oxygen as at winter temperature — 0° C. So that water saturated at summer temperature actually contains less oxygen than water only 65 per cent saturated in winter.
In Jakes and reservoirs used for public water-supply the water above the transition zone is usually saturated with oxygen. This is because of the constant circulation of the water which continually brings it in contact with the air. In the stagnation zone there is usually a depletion of the oxygen,
DISSOLVED GASES AND MICROSCOPIC ORGANISMS 127
and if the amount of organic matter at the bottom is large, so that decomposition is active, the oxygen may be nearly or completely exhausted. Usually there is a gradual reduction within and below the transition zone. Sometimes however the change is very sharp. Thus in Irondequoit Bay, near Rochester, N. Y., on Aug. 8, 191 2, analyses showed the follow- ing percentages of saturation with dissolved oxygen at different depths.
DISSOLVED OXYGEN IN IRONDEQUOIT BAY
|
Depth in Feet. |
Temperature, Deg. F. |
Per cent of Saturation. |
|
0 |
69.8 |
100. 0 |
|
27 |
63.6 |
80.0 |
|
28 |
61.5 |
12. 1 |
|
29 |
60.5 |
2.2 |
|
30 |
59 5 |
1.5 |
|
36 |
52.0 |
0.0 |
|
75 |
45 3 |
0.0 |
The decay of algae in a reservoir may reduce the dissolved oxygen even at the surface. Thus during the autumn of 1913 the dissolved oxygen in the water of Fresh Pond, Cambridge, remained below 80 per cent for several weeks.
It sometimes happens that algae are concentrated at the transition zone and that through photo-synthesis oxygen is produced more rapidly than it can be diffused — hence a con- dition of super-saturation there may result, the percentage of saturation rising to 200 per cent or even 300 per cent. In this condition the oxygen is probably in or attached to the orgam'sms rather than actually in solution.
In the winter, when the surface is frozen, the oxygen supply from the air is cut off, while the photo-synthetic processes are at a low ebb, partly because of the cold and partly because the amount of simlight received is less. Yet respiration and decom- position continue, although these processes also are reduced in activity. The result is that beneath the ice the oxygen in the water tends to diminish. It is seldom greatly reduced imless the bottom of the lake is foul and the decomposition excessive.
128 THE MICROSCOPY OF DRINKINa WATER
At the times of the spring and fall overturn the water is usually well aerated from top to bottom.
Again in shallow bodies of water the decay of organisms and organic matter may cause a depiction of oxygen sufficient to kill fish.
Seasonal Changes in Carbonic Acid. — In lakes and reser- voirs where there are few algae or aquatic plants, that is where photo-synthesis is not taking place to any extent, the water near the surface contains normally a small amount of carbonic add — usually less than 2 parts per million. If decomposition is tak- ing place this amount may be somewhat greater. If, however, green plants are present and food building is in process, the amount of carbonic acid may be entirely absent. And, more than that, some of the carbonic acid may be removed from the bicarbonates, leaving normal carbonates of calcium and mag- nesium, which are not very soluble. If the amounts of bicar- bonates were originally large there may be a precipitation of calcium carbonate brought about in this way. When carbonic acid has been thus removed from the bicarbonates the water is alkaline to phenolphthalein, (the indicator used to detect carbonic acid), that is, the carbonic acid result becomes negative.
Just what algae and water plants are able to take away carbonic acid from the bicarbonates is not known. Possibly all of them do. It is believed that such water weeds as Potamo- geton, Carex, and Batrachium, draw heavily on the bicarbonates, and it is also known that blue-green algae, such as Anabaena and Clathrocystis, and diatoms, such as Asterionella, will do the same.
In general, then, in summer the carbonic acid tends to de- crease above the transition zone and to increase below it. This is illustrated by Fig. 49.
In shallow ponds the rise and fall of the carbonic add indi- cates the relative importance of the changes of growth and decay.
The most complete study of dissolved carbonic add in lake waters is that made by Dr. Birge and Dr. Juday. Fig. 50, copied from their valuable monograph, illustrates these changes in a very striking way.
DISSOLVED QASES AND MI0ROSCX)PIC 0RQANI8U3 129
Relation <tf Dissolved Gases to Algte. The best discussion of this subject b to be found in a paper by Dr. Charles O. Cham- bers published in the twenty-third annual report of the Missouri Botanical Gardens, issued Dec. i8, 1912. Chambers has not only compiled data from various foreign laboratories but has carried on a series of experiments made in the lagoons of the
|
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Carbon DlozldQ(p«iTtB per mlUlonl
Fic. 4g.
botanic gardens at St. Louis, where blue-green algce were grow- ing. Of especial interest is his observation thai on dear, sunny days the water became supersaturated with dissolved oxygen, while on cloudy days the percentage of oxygen fell below satu- ration, sometimes as low as 40 per cent. In general the carbonic acid increased as the oxygen decreased, but this reciprocal relation did not always hold. This same fluctuation in gaseous
130 THE MICROSCOPY OF DRINKING WATKB
contents also occurs between day and night according to authorities quoted. Another interesting finding is that aera- tion tends to the formation of individual ceUs, while in pooriy aerated water there is a tendency for organisms to fonn colomes and filaments.
Chambers has summarized the results of his findings as follows: I. There is an intimate and mutual relation between the algie and submerged aquatics in a body of water and the gases dissolved in that water. They fluctuate together.
Fig. 50. — Dissolved OnyRcn at Diffc:rL'nl Depths i After Birgc and Juday.
2. Air, or its constituents, oxygen and COa, are as essential to water plants as water is to land plants, and equally difficult to secure.
3. Warm and stagnant water is poorer in these essentials than colder water gently agitated by wind or currents.
4. Currents arc especially beneficial to attached plants by renewing or removing these gases.
DISSOLVED GASES AND MICROSCOPIC ORGANISMS 131
$. Some species demand more aeration than others. Some species are more tolerant of stagnant waters than others.
6. Filamentous forms with large cells and thin outer walls are best adapted to stagnant waters. Such forms predominate in warm, tropical fresh waters, which are poorly aerated.
7. The photo-synthesis of rapidly-growing algae and aquatic plants in a body of water may diminish or deplete the supply of CO2 and increase the oxygen content beyond saturation.
8. In the absence of free CO2 the plants may utilize the half- bound CO2 of the dissolved bicarbonates, chiefly those of caldum and magnesium.
9. The process of photo-synthesis may be so vigorous as to exhaust the half-bound CO2 and render the water alkaline. By respiration and absorption of CO2 from the air more bicar- bonates may be formed. This serves as a mechanism for the conservation of CO2.
10. Waters rich in lime-carbonates are also rich in vegeta- tion. Bog waters, containing humic acids, and, consequently, poor in carbonates of lime, are known to be poor in vegetation.
11. Stagnant water, on account of the large amount of CO2 and the small amount of oxygen, favors the formation of colonies and filaments rather than of free individual cells.
12. Colonies and filamentous forms may be produced artifi- cially with some plants, by increasing the amount of CO2 or diminishing the amount of oxygen in the culture solutions.
13. Narrow, much-branched filaments are adapted to and produced by poorly aerated waters.
14. Aeration, or abundance of oxygen, apparently favors the formation of chlorophyll; and algae are brighter green when well aerated.
15. The periodicity of spore formation is not readily influenced by aeration or gas content of the water. It seems to be more a matter of heredity.
Death of Fish in Weequahic Reservation, Newark, N. J. — In August, 1906, a large number of fish suddenly died in the lake at the Weequahic Reservation, Newark, N. J. This was investigated by Herbert B. Baldwin and the author, the results
132 THE MICROSCOPY OP DRINKING WATER
of which may be found in a report made to the Park Com- mission of Essex County, N. J., for that year.
The lake covered about 80 acres and had an average depth of between 5 and 6 ft., although in a few spots the water was 12 ft. deep. The site of the reservoir was a swamp in which the depth of mud and peaty matter varied from 2 to 10 ft. This mud was not removed when the reservoir was constructed. Aquatic plants, water weeds and filamentous alga; flourished in the lake and at times great masses of peat and stimips have floated to the surface. In the summer heavy growths of blue- green algae have occurred.
On the night of August 19 twelve two-horse loads of dead fish were picked up on the shore and it was estimated that more than fifteen tons died in two days. The dead fish included bass, roach, sunfish, horn pout, suckers, eels, and a few carp. They varied in size from sunfish 2 inches long to black bass weighing 5 pounds. The investigation showed that the probable cause of the death of the fish was an almost complete exhaustion of oxygen which resulted from the sudden decay of the algae which had been occurring in the lake. The analyses made by the investigation offered additional testimony to the dose relations which exist between carbonic acid, dissolved oxygen, and alga; growths in water.
CHAPTER IX
OCCURRENCE OF MICROSCOPIC ORGANISMS IN LAKES AND
RESERVOIRS
The microscopic organisms that are found most conmionly in the water-supplies of Massachusetts taken from lakes or storage reservoirs are given in the following table, arranged according to the usual system of classification and divided into groups according to their abundance and frequency of occurrence. The first group includes those genera which, in their season, are often foimd in large numbers; the second group includes those which are foimd but occasionally in large numbers; the third, those which often occur in small numbers; the fourth, those which are rarely observed. This division, while not wholly satisfactory, enables one to separate the important from the unimportant forms. As observations multiply, the list may be extended and some genera may be changed from one group to another. The organisms printed in heavy type have given trouble in water-supplies, either by producing odors or by making the water turbid and unsuitable for laundry purposes.
DIATOMACEiE
Commonly found in large numbers. Asterionellay Cyclo- tella, Melosira, Synedra, Tabellaria.
Occasioftally found in large numbers. Diatoma, Fragilaria, Nitzschia, Stephanodiscus.
Commonly found in small numbers. Epithemia, Gom- phonema, Navicula, Stauroneis.
Occasionally observed. Achnanthes, Amphiprora, Amphora, Badllaria, Cocconeis, Cocconema, C>Tnbella, Diadesmis, Enco- nema, Eunotia, Grammatophora, Himantidium, Isthmia, Mer-
133
134 THE MICROSCOPY OF DRINKING WATER
id ion 9 Odontidium, Orthosira, Pinnularia, PleurosigmEy Schizo- nema, Striatella, Surirella, Tetracyclus.
CHLOROPHYCE^
Commonly found in large numbers. Chlorococcus, Pro- tococcus, Scenedesmus.
Occasionally found in large munbers. Coelastniniy Cos- marium, Palmellay Pandorina, Polyedrium, Raphidium, Stau- rastrum, Volvox.
Commonly found in small numbers, Closterium, Conferva, Desmidium, Euastrum, Eudorina, Gonium, Micrasterias, Ophi- ocytium, Pediastrum, Sphajrozosma, Staurogenia, Tetraspora, Ulothrix, Xanthidium.
Occasionally observed. Arthrodesmus, Bambusina, Botryo- coccus, Characium, Chaetophora, Cladophora, Dactylococcus, Dictyosphxrium, Dimorphococcus, Draparaaldia, Glceocjrstis, Hyalotheca, Mesocarpus, Nephrocytium, Penium, Selenastrum, Sorastmm, Spirogyra, Stigeoclonium, Tetmemorus, Zygnema.
CYANOPHYCEiE
Commonly found in large numbers. Anabsena, Clathro- cystis, Coelospha^rium, Microcystis.
Occasionally found in large numbers. Aphanizomenon, Chro- ococcus Oscillaria.
Commonly found in small numbers. Aphanocapsa. Occasionally observed. Gloeocapsa, Lyngbya, Merismopedia, Microcoleus, Nostoc, Rivularia, Sirosiphon, Tetrapedia.
SCHIZOMYCETES AND FUNGI
Commonly found in large numbers. Crenotlirix.
Occasionally found in large numbers. Cladothrix^ Chlamydo- thrix, GalHonella.
Commonly found in small numbers. Beggiatoa, Leptothrix, Molds. '^
Occasionally observed. Achlya, Leptoinitus, Saprolegnia, Sarcina, Spirillum.
MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 135
PROTOZOA
Commonly found in large numbers, CryptomonaSy Dino« bryony Peridiniuniy Synura, Uroglena.
Occasionally found in large numbers, Bursaria, Chloro- monas, Qlenodinium, Mallomonas, Raphidomonas.
Commonly found in small numbers. Actinophrys, Amoeba^ Anthophysa, Ceratium, Cercomonas, Codonella, Epistylis, Monas, Tintinnus, Trachelomonas, Vorticella.
Occasionally observed, Adneta, Arcella, Chlamydomonas, Coleps, Colpidium, Cyphodera, Difflugia, Enchelys, Euglena, Euglypha, Euplotes, Glaucoma, Halteria, Heteronema, Nas- sula, Paramaecium, Phacus, Pleuronema, Raphidodendron, Stentor, Syncrypta, Trichodina, Uvella, Zoothamnium.
ROTIFERA
Commonly found in small numbers, Anursea, Conochilus, Polyarthra, Rotifera, Synchaeta.
Occdsionally observed, Asplanchna, . Colurus, Eosphora, Floscularia, Lacinularia, Mastigocerca, Microcodon, Mono- cera, Monostyla, Noteus, Sacculus, Triarthra.
CRUSTACEA
Commonly found in small numbers, Bosmina, Cylcops> Daphnia.
Ouasionally observed, Alona, Cypris, Diaptomus, Sida.
MISCELLANEOUS
Occasionally observed, Acarina, Anguillula, Batrachosper- mum, Chajtonotus, Gordius, Hydra, Macrobiotus, Meyenia, Nais, Spongilla; besides spores, ova, insect scales, pollen grains, vegetable fibers and tissue, yeast-cells, starch-grains, etc.
136
THE MICROSCOPY OF DRINKING WATER
The above may be summarized numerically as follows:
ClustficAtion.
Diatomaceae
Chlorophyce«
Cyanopbyceae
Fungi and Scbizomycetes.
Protozoa
Rotifera
Crustacea
Miscellaneous
Total
Number of Generm.
Commonly
found
in Urge
numbers.
5 3 4 I
5 o
o
o
i8
Occasion- ally found in large numbers.
4 8
3
3
5 o
o
o
23
Commonly
found
in small
numbers.
4
14
I
3 II
5
3 o
41
Occmrion-
aUy obeenred.
22
21
8
5 24
12
4
lO
io6
TotaL
35 46 16 10
45
17
7 10
188
It will be observed that 188 genera have been recorded, — no plants and 78 aminals. Of these only 18 are conunonly found in large numbers — 13 plants and 5 animals. 23 more are occasionally found in large numbers — 18 plants and 5 animals. 41 genera are frequently seen in small nimibers, while 106 genera, or more than one-half of all are seen occa- sionally, some of them rarely. The most important classes are the Diatomacea?, Chlorophyceaj, Cyanophyceae, and Protozoa, as shown by the large number of genera and by their greater abundance. Furthermore, these classes include all the most troublesome genera that have been found in large numbers. There are 10 genera that are particularly troublesome because of their wide distribution, the frequency of their occurrence, and their unpleasant effects. They are Asterionella, Anabxna, Clathrocystis, Calospha^rium, Aphanizomenon, Dinobryon, Peri- dinium, Synura, Uroglena, and Glcnodinium. This list seems like a short one when one considers the annoyance that the microscopic organisms have caused in various water-supplies.
Wide Distribution of the Plankton. — The observations of sanitarians and the planktologists show that the microscopic organisms are very widely distributed in nature. They are found in all parts of the world, and under great varieties of climatic conditions. It is probable that they appeared on the
MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 137
earth at an early geological age. Some of them arc found as fossils — notably the diatoms, which have silidous walls that are almost indestructible.
In spite of the vast amoimt of study that has been given to the microscopic organisms we are still verj^ far from imder- standing the laws governing their distribution. ^Tiy it is that a certain genus will grow vigorously in one pond and at the same time be absent from a neighboring one where the conditions apparently are as favorable, or why a form may suddenly appear in a pond where it has never before been seen, we are still imable to say with certainty. Solution of such problems involves a far-reaching knowledge of the chemical constituents and the life-history of the organisms, besides the effect of physical conditions, such as temperature, pressure, and light. Mention was made in the last chapter of the probable ^influence of the dissolved gases, carbonic acid and oxygen. The sciences of bio-chemistry and bio-physics are yet in their infancy. Until these have been further developed many problems connected with the microscopic organisms must remain imsolved.
Classification of Massachusetts Data made in 1900. — ^The following statistics compiled by the author are of some value in connection with this subject, as they show the relative abim- dance of the different classes of organisms in some of the important surface-water supplies of Massachusetts, together with some of the elements of the sanitary chemical analysis.
For the purpose of this comparison 57 ponds and reser- voirs were selected where monthly examinations, both chemical and biological, were carried on for a number of years by the State Board of Health. The results of these examinations were carefully studied, and the lakes, which, for convenience, are made to include lakes, ponds, and storage reservoirs, are divided into groups as shown in the table on pages 138 and 139.
The first two columns in this table give the names of the lakes and the citites which they supply. The third gives the depth, whether shallow or deep. The next four columns show the relative abundance of the four most important classes of organisms; namely, the Diatomaceae, Chlorophyceae, Cyano-
138 THE MICROSCOPY OF DRINKINO WATER
0O0O++0O+0++0+O++OO+OOO+0OOO
MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 139
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140
THE MICROSCOPY OF DRINKINa WATER
phyceae, and Protozoa. The four groups are characterized as follows: the group to which each pond belongs is indicated by a Roman numeral.
Group I. Number of organisms often as high as looo per c.c.
Group II. Number of organisms only occasionally as high as looo per c.c.
Group m. Number of organisms ordinarily between loo and 500 per c.c.
Group rV. Number of organisms never above 100 per c.c.
These figures refer not to the numbers present in the average sample of water, but to the numbers during the season of maximum growth. The boundaries of the groups were not sharply defined, and in a number of cases it was hard to tell whether a lake should be classed in Group 11 or HI. The last five columns show the lakes divided into classes according to some of the elements of the chemical analysis; namely, color, excess of chlorine, hardness, albuminoid ammonia (in solution), free ammonia, and nitrates. In each case four classes are given, division being made according to the schedule pven at the bottom of the table.
If we consider the lakes with reference to the growths of organisms, we obtain from the above table the following summary:
|
Number per c.c. |
Number of Lakes and Reservoirs. |
||||
|
Group. |
Diato- maceae. |
Chloro- phyces. |
Cyano- phyce«. |
Protosoa. |
|
|
I |
Often above lOOO ner c.c |
24 8 19 6 |
5 II 29 12 |
7 10 18 22 |
8 |
|
II III IV |
Occasionally above lOoo per c.c, . . Usually between lOO and 500 per c.c. Below 100 oer c.c. |
7 35 7 |
|||
From this it appears that the Diatomacea? were the organ- isms most commonly found in large numbers. There were 24 ponds (42 per cent of the ponds considered) which often had these organisms as high as 1000 per c.c, while in only 6 (11 per cent) were they always below 100 per c.c. The Chloro- phyccaj were not often found in great abundance, though many lakes contained them in moderate numbers. Only 5 lakes
MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 141
(9 per cent) had growths of 1000 per ex., while 29 (70 per cent) had growths of from 100 to 500 per c.c. The Cyanophyceae were not as common as the Chlorophyceae, but where they did occur their growth was usually greater and they caused more trouble. There were 7 lakes (12 per cent) that commonly had growths above 1000 per c.c, while in 22 (39 per cent) they were never above 100 per c.c. The Protozoa were somewhat more abundant than either the Chlorophyceae or Cyanophyceae. Eight lakes (12 per cent) often had growths above 1000 per c.c; 35 lakes (60 per cent) had growths between 100 and 500 per cc.
From the table on pages 138 and 139 it also appears that 28 lakes (49 per cent) often had large growths of one or niore of these classes of organisms at some time during the year. Such growths, except in the case of certain diatoms, were nearly always noticeable and frequently were very troublesome. In 17 lakes the Diatomaceae alone reached 1000 per cc; in i lake the Cyanophyceae alone; and in 3 lakes the Protozoa alone. One lake had heavy growths of Diatomacea?, Chlorophyceae and Protozoa; two, of Diatomaceae, Chlorophyceae and Cyano- phyceae; two, of Diatomaceae, Cyanophyceae and Protozoa. In two lakes all four classes were found in large numbers. There was but one lake where the organisms never rose above 100 per c.c; there were 16 where no class of organisms showed numbers greater than 500 per cc.
E£fect of Depth. — For the purpose of determining whether the depth of the lake exercised any important influence upon the growth of the organisms the following table was compiled:
|
Number per c.c. |
Number of Lakes. |
||||
|
Depth.* |
Diato- macese. |
Chloro- phyceae. |
Cyano- phyceae. |
Protoxoa. |
|
|
Deep. . . . Deep. . . . Deep .... Deep. . . . Shallow. . |
Often above looo oer c.c |
8 |
3 2 8 3 2 9 21 9 |
a I 6 7 5 9 12 IS |
2 |
|
Occasionally above lOOO per c.c. . . . Utually between loo and 500 per c.c. Alwavs below 100 oer c.c |
2 6 0 16 6 13 6 |
0 12 2 |
|||
|
Often above 1000 oer c.c |
6 |
||||
|
Shallow. . Sballow. . Shallow. . |
Occasionally above 1000 per c.c. . . . Ustially between xoo and 500 per c.c. Always below 100 per c.c |
7 23 5 |
* Lakes of the Second Order are here called "deep lakes;" lakes of the third order 'shallow lalcM'/'; no lakes of the First Order are included. See page 99-
142 THE MICROSCOPY OF DRINKING WATER
There were i6 deep and 41 shallow lakes. Of the deep lakes 63 per cent at times had growths of the Diatomaces above 1000 per c.c, while of the shallow lakes 54 per cent had such growths. There were no deep lakes where the Diatomacese were lower than 100 per c.c, while in 15 per cent of the shallow lakes they were lower than that figure. It thus appears that the heavy growths of the Diatomacese were somewhat more likely to be found in the deep than in the shallow lakes. The same may be said of the Chlorophyceae, though the difference was not so marked. 31 per cent of the deep lakes and 27 per cent of the shallow lakes at times had growths as high as 1000 per c.c. The Cyanophyceae and Protozoa, on the other hand, inclined toward shallower water. In the case of the former, 18 per cent of the deep lakes and 34 per cent of the shaUow lakes at times had growths of 1000 per c.c, while in the case of the latter the figures were 12 per cent and 32 per cent respect- ively.
In this connection it would be of interest to show statis- tically the relation that undoubtedly exists between the growths of organisms and the character of the material forming the bottoms of the ponds, but unfortunately the necessary data are lacking in too many cases. So far as observations have been made, it appears that muddy bottoms are very largely responsible for excessive growths of microscopic organisms. This topic is mentioned again in Chapter XIII.
Relation to the Chemical Analysis. — An important question, and one which is of particular interest to water analysts, is the relation between the growths of organisms and the chemical analysis of the water in which the organisms are found. Unques- tionably there must be some relation, but thus far our knowledge of the food requirements of the plankton is not sufficient to enable us to tell what this relation is. Something may be learned, however, by considering the subject statistically.
The tables given on pages 144 and 145 show in a very general way the relation between the organisms in the 57 selected Massa- chusetts lakes and reservoirs and some of the important elements of the chemical analysis.
MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 143
These tables reveal several important facts: first, it is seen that the color of the water has an important influence upon the number of organisms that will be found in it. Of the 24 cases where the Diatomaceae were commonly found higher than 1000 per c.c, 12 (or 50 per cent) occurred in light-colored waters, i.e., water having a color less than 30, and none occurred in water where the average color was above 100. The same fact was noticed in the case of the other organisms, but not as mark- edly as with the Diatomaceae. The reason for this may be on account of the difference in specific gravity between the diatoms and the other organisms. The diatoms are heavy by reason of their siliceous cell-walls, but the other organisms are much lighter and it is easier for them to keep near the sur- face. The depth to which light penetrates in a body of water makes less difference with the growth of the Cya^ophyceae, for example than it does with the diatoms, which constantly tend to sink and which are kept near the surface chiefly by the ver- tical currents in the water.
Relation to Excess of Chlorine. — The " excess of chlorine " means the difference between the amount of chlorine found in a sample of water and that found in the unpolluted water of the same region. To a certain extent it represents the amount of pollution which the water has received. It is important to know whether this element of the analysis bears any relation to the organisms and whether one may rightly infer that a large growth of organisms in a reservoir is any indication of the pollu- tion of a water-supply. A study of the tables shows that only to a small extent did the excess of chlorine accompany the number of organisms observed, though there was a slight tendency for heavy growths of organisms to accompany high excess of chlorine. This fact corresponds with the common observation that vigorous growths of organisms are often observed in ponds or lakes far removed from any possible contamination.
Relation to Hardness. — The hardness or a water, i.e., the abundance of carbonates and sulphates of calcium and mag- nesium, appears to have some influence upon the organisms. This is noticed in all four classes, though it is most marked
144
THE MICROSCOPY OF DRINKINa WATER
A.
|
Number of LAket and Rawnroirt In |
wliklltlM |
||||
|
1 Analsrtis. |
Diatomaces are. |
||||
|
ChemicA |
|||||
|
(parts per |
1, 000,000). |
Often |
OccasionaUy |
UioaUTbe. |
|
|
above |
above |
tween 100 |
B«km |
||
|
1000 per c.c. |
1000 per ex. |
andsoo per ex. |
100 per ex. |
||
|
Color |
0 to 30 |
13 |
|||
|
30 to 60 |
6 |
||||
|
60 to 100 |
6 |
||||
|
above 100 |
0 |
||||
|
BzceM of |
0 |
4 8 |
|||
|
Chlorine |
0.1 to 0.3 |
||||
|
0.4 to 2.5 |
8 |
10 |
|||
|
above a . 5 |
4 |
||||
|
Hardness |
0 to 5 |
a |
|||
|
. S to 10 |
7 |
||||
|
• |
x.o to 20 |
8 |
10 |
||
|
above 20 |
7 |
||||
|
Albuminoid |
0 too. 100 |
a |
|||
|
Ammonia |
o.ioo too. 150 |
6 |
|||
|
(dissolved) |
0.150 to 0.200 above 0 . aoo |
8 |
|||
|
8 |
5* |
||||
|
Free |
0.000 too. 010 |
3 |
|||
|
Ammonia |
o.oio too. 030 |
6 |
10 |
||
|
0.030 to O.IOO |
8 |
||||
|
above 0. 100 |
7 |
||||
|
Nitrates |
0 to 0 . 050 |
3 |
|||
|
0.050 too. 100 |
IX |
13 |
|||
|
0. 100 to 0.200 |
6 |
a |
I |
||
|
above 0 . 200 |
4 |
I |
0 |
B.
|
Number of Lakes and Reservoirs in which the |
|||||
|
(^hlorophyceae are |
|||||
|
Chemical Analysis |
|||||
|
(parts per 1,000,000). |
Often |
Occasionally |
Usually be- |
||
|
above |
above |
tween 100 |
Below |
||
|
1000 per c.c. |
1000 per c.c. |
and soo per c.c. |
100 per ce. |
||
|
Color |
0 to 30 |
2 |
5 |
14 |
|
|
30 to 00 |
a |
5 |
|||
|
60 to 100 |
I |
8 |
|||
|
above 100 |
0 |
3 |
|||
|
Excess of |
0 |
X |
4 |
||
|
Chlorine |
0.1 to 0 . 3 |
I |
II |
||
|
0.4 to 2.5 |
0 |
13 |
|||
|
above 2.5 |
3 |
X |
|||
|
Hardness |
0 to 5 |
0 |
3 |
||
|
5 to 10 |
I |
8 |
|||
|
10 to 20 |
I |
13 |
|||
|
above 20 |
3 |
5 |
|||
|
Albuminoid |
0 too. 100 |
0 |
3 |
||
|
Ammonia |
0. 100 to 0. 150 |
0 |
7 |
||
|
(dissolved) |
0 . 1 so to 0 . 200 above 0 . 200 |
a |
13 |
||
|
3 |
8 |
||||
|
Free |
0 to O.OIO |
0 |
7 |
||
|
Ammonia |
O.OIO to 0.030 |
0 |
13 |
||
|
0.030 to 0.010 above 0. 100 |
3 |
8 |
|||
|
3 |
I |
||||
|
NiUates |
0 to 0.050 |
0 |
8 |
||
|
0.050 too. 100 |
3 |
13 |
|||
|
0 . 1 00 to 0 . 200 |
0 |
7 |
|||
|
above 0 . 200 |
3 |
X |
MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 145
|
Number of Lakes and Reservoirs in |
which the |
||||
|
1 Analysis |
Cyanophyceae are |
||||
|
Chemica |
|||||
|
(parts per |
i.ooo.ooo). |
Often |
Occasionally |
UsuaUy be- |
|
|
above |
above |
tween 100 |
Below |
||
|
1000 per c.c. |
1000 per c.c. |
and 500 per c.c. |
100 per cc |
||
|
Color |
0 to 30 |
2 |
4 |
12 |
II |
|
30 to 6o |
2 |
3 |
4 |
3 |
|
|
6o to loo |
3 |
I |
7 |
||
|
above loo |
0 |
I |
I |
||
|
Excess of |
0 |
2 |
3 |
3 |
|
|
Chlorine |
O.I too. 3 |
I |
S |
10 |
|
|
o . 4 to 2 . 5 |
I |
8 |
9 |
||
|
above 2.$ |
3 |
2 |
0 |
||
|
Hardness |
o to 5 |
0 |
I |
6 |
|
|
S to 10 |
2 |
4 |
10 |
||
|
10 to 20 |
2 |
7 |
s |
||
|
above ao |
3 |
6 |
I |
||
|
Albuminoid |
0 to 0. lOO |
0 |
I |
t |
|
|
Ammonia |
O. lOO to o.iso |
0 |
6 |
||
|
(dissolved) |
0.150 t0 0.200 above o . aoo |
2 |
8 |
7 |
|
|
5 |
3 |
s |
|||
|
Free |
o to o.oio |
0 |
I |
10 |
|
|
Ammonia |
o.oio to 0.030 |
0 |
9 |
8 |
|
|
0.030 too. 100 |
3 |
6 |
4 |
||
|
above o.ioo |
4 |
2 |
0 |
||
|
Nitrates |
0 to 0.050 |
I |
I |
13 |
|
|
0.050 to O.IOO |
3 |
10 |
10 |
||
|
0. 100 to 0.200 |
I |
3 |
5 |
0 |
|
|
above 0 . 200 |
2 |
I |
2 |
0 |
D.
|
Number of Lakes and Reservoirs in |
which the |
||||
|
cal Analysis |
Protozoa are |
||||
|
Chemi |
|||||
|
(parts per i.ooo.ooo). |
Often |
Occanionally |
Usually be- |
||
|
above |
above |
tween 100 |
Below |
||
|
1000 per c.c. |
1000 per c.c. |
and 500 per c.c. |
100 per cc |
||
|
Color |
0 to 30 |
5 |
2 |
20 |
|
|
30 to 60 |
I |
3 |
6 |
||
|
60 to 100 |
2 |
2 |
8 |
||
|
above 100 |
0 |
0 |
I |
||
|
Excess of |
0 |
I |
2 |
5 |
|
|
Chlorine |
0.1 to 0 . 3 |
I |
2 |
13 |
|
|
0 . 4 to 2 . 5 |
2 |
3 |
15 |
||
|
above 2.5 |
3 |
0 |
3 |
||
|
Hardness |
0 to 5 |
0 |
0 |
7 |
|
|
5 to 10 |
3 |
0 |
12 |
||
|
10 to 20 |
I |
6 |
10 |
||
|
above 20 |
4 |
I |
6 |
||
|
Albuminoid |
0 to O.IOO |
0 |
0 |
4 |
|
|
Ammonia |
O.IOO to 0.150 |
0 |
0 |
13 |
|
|
(dissolved) |
0. ISO to 0.200 |
5 |
2 |
12 |
|
|
above 0 . 200 |
3 |
4 |
7 |
||
|
Free |
0 to O.OIO |
I |
I |
9 |
|
|
Ammonia |
O.OIO to 0.030 |
I |
I |
13 |
|
|
0.030 to O.IOO above o.ioo |
2 |
5 |
10 |
||
|
4 |
0 |
3 |
|||
|
Nitrates |
0 to 0 . 050 |
0 |
I |
12 |
|
|
0.050 to O.IOO |
3 |
4 |
17 |
||
|
O.IOO to 0.200 |
3 |
2 |
3 |
||
|
above 0 . 200 |
2 |
0 |
3 |
0 |
146 THE MICROSCOPY OF DRINKmO ^W ATKR
in the case of the Diatomaceae and Protozoa. For example, of the I o lakes low in hardness not one had the Protozoa as high as looo per c.c, wlule of the ii lakes high in hardness every one had Protozoa above loo per ex., and 4 commonly had them above 1000 per c.c. It is probable that it is the greater amoimt of free carbonic acid accompanying the waters of high hardnessL which stimulates the growth of the organisms, rather than the salts of calcium and magnesium.
Relation to Nitrates. — The sanitary chemical analysis ordi- narily states the amount of nitrogen present in four different forms, namely, albuminoid ammonia (dissolved and suspended), free ammonia, nitrites and nitrates, which represent four stages in the change of organic to inorganic matter. Since nitrogen is essential to all living matter we naturally expect that organ- isms will thrive best in waters rich in that element. The above statistics show that this is the case, and that it is true for each class of organisms and for the different conditions of nitrogen tabulated. The free ammonia and nitrates appear to be partic- ularly influential in determining the amount of life present. For example, 10 of the 13 lakes low in free ammonia never show maximum growths of the Cyanophyceae above 100 per c.c, while 4 of the 7 lakes high in free ammonia commonly have growths above 1000 per c.c.
One must be careful in these matters, however, not to mistake cause for effect. Free ammonia, for example, indi- cates organic matter in a state of decay, and instead of repre- senting the food of the organisms in question it may represent their decomposition. The interaction of the various organisms is a very complicated question, and the extent to which one organism lives upon the products of decay of another is not well known.
Studies of Steams and Drown. — In 1900, Mr. F. P. Steams, Chief Engineer, and the late Dr. T. RI. Drown, Chief Chemist, of the Massachusetts State Board of Health made a statistical study of Massachusetts Ponds and Reservoirs to ascertain the relation between pollution and the occurrence of bad tastes and odors caused by organisms. Their results, which included
MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 147
data for 70 ponds and reservoirs for a period of two years were summarized as follows:
CLASSIFICATION OF PONDS AND RESERVOIRS WITH REFERENCE TO TROUBLES FROM BAD TASTES AND ODORS.
|
Ponds. |
ReaervoirB. |
|||||
|
Conditioni. |
Trouble. |
Trouble. |
||||
|
• |
Much. |
Little. |
None. |
Much. |
LitUe. |
None. |
|
Polluted ShaUow and hish color. |
• • • ■• • . • .... 4 4 • • • • I 2 4 7 |
• • • • • • • • • • • • • a • ■• • • • I • • • • 2 16 19 |
I • • • • • ■• • • • • « I 10 I 1 3 IS |
• • • • • • • • I • • • • I ■• • • • • • • 2 2 4 |
||
|
Deep and hiffh color |
I 3 4 |
|||||
|
Deep and low color |
||||||
|
Total Polluted |
||||||
|
Unpolluted Shallow and hiffh color. ^ , . , |
||||||
|
Shallow and low color |
3 |
2 |
||||
|
Deep and hizh color |
A |
|||||
|
Deep and low color |
I 4 |
I |
||||
|
Total unpolluted |
7 |
|||||
|
/ |
||||||
|
Total polluted and unp>olluted. |
8 |
II |
19 |
16 |
S |
7 |
" The above table shows that, out of a total of 38 ponds, 8, or 21 per cent, have given much trouble from bad tastes and odors; while, of the 28 reservoirs, 16, or 57 per cent are sim- ilarly affected.
" In comparing the polluted and unpolluted ponds, the effect of pollution is very obvious. All of the polluted ponds are deep; but, notwithstanding this advantage, all are affected to some extent, and half of them give much trouble. Of the 25 deep, unpolluted ponds, only one has given much trouble, 6 have given a little trouble, and 18 no trouble whatever. This indicates that there is little danger of having serious trouble from bad tastes and odors, if a water supply can be taken from a deep pond which is xmpolluted. The shallow, unpolluted
148 THE MICROSCOPY OF DRINKING WATER
ponds appear to be subject to bad tastes and odors, as 3 out of a total of 5 give much trouble, and i a little trouble.
" Only 2 of the reservoirs are polluted, but these give the same indications as the 8 polluted ponds, i giving much trouble and the other a little. Of the 26 unpolluted reservoirs, one-half are shallow. Of these 11 give much trouble and 2 give none. In nearly all of these cases in which trouble has occurred, the reservoirs have been constructed on new sites, and the soil and vegetable matter have not been removed from their bottoms and sides. In one of the cases where there is no trouble the reservoir was used to furnish power for a mill before being used as a source of domestic water-supply. The conclusion to be drawn from this comparison is, that a shallow reservoir large enough to hold a supply for a month or more is quite sure to give trouble if the soil and vegetable matter are not removed from it before filling. The experience at the present time is too limited to enable us to predict what proportion of deaned or old shallow reservoirs are likely to give trouble.
" Of the 13 deep, unpolluted reservoirs, 4 give much trouble, 4 a little and 5 none. It is noticeable that, of the 5 which give no trouble, 4 have had the soil and vegetable matter removed from them, and i was previously a storage reservoir for mill purposes; while, of the 8 which have given more or less trouble, none have been thoroughly cleaned, and only one was previously used for mill purposes, and even this has since been raised. Two of the older reservoirs, which are classed as giving little trouble, have not given any trouble in recent years.
" Among the 4 deep reservoirs classed as giving much trouble, is the Ludlow reservoir, at Springfield, which has furnished bad water in summer for 16 years. The other 3 reservoirs of this class have not given nearly as much trouble.
" In several other instances the reservoirs which have given trouble are flowed over swamps and meadows."
Classification of New England Data made in 1906. — ^In 1906 in connection with a report made by Messrs. Allen Hazen and George W. Fuller, to the Board of Water Supply of the City of New York, on the advisability of removing the soil from the
MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 149
Ashokan and Kensico reservoirs, the author made a statis- tical study of the available data relating to the occurrence of microscopic organisms in stored waters. Data were collected for 66 lakes and reservoirs in New England.
In making this comparison the reservoirs were separated into groups according to the frequency of the occurrence of microscopic organisms and into classes according to the odors attributed to the waters.
Index of Frequency. — ^For purposes of comparison the fre- quency of the occurrence of microscopic organisms and the intensity of their growth were used to obtain a single figure for each reservoir, which was intended to represent relatively the trouble caused by organisms in each reservoir as compared with similar figures for other reservoirs. This figure, which came to be known as the index of frequency was calculated as follows.
It was assumed that when the organisms were less than 500 per c.c. they would cause no trouble; between 500 and 1000 per c.c, little trouble; between 1000 and 2000 noticeable trouble; between 2000 and 3000, decided trouble, and that above 3000 the trouble would be serious. From the analyses the per cents of the time when the organisms were present within these limits were ascertained. These were then weighted as follows and added together: For numbers between 500 and 1000, one- half the per cent; for numbers between 1000 and 2000, the per cent as computed; for numbers between 2000 and 3000, twice the per cent; and for numbers above 3000, three times the per cent. The above was based on organisms of all kinds disregarding genera.
Let us suppose that weekly microscopical analyses gave the results shown in the first two columns of the table on p. 150. The method of computing the index of frequency is indicated by the later columns.
An index of 50 would mean that the growth of organisms were noticeable half of the time, or that if they were present for less than half the time they were more troublesome during the time when they were present.
150
THE MICROSCOPY OP DRINKING WATER
|
Number of Organisms per c.c. |
Number of Days when Orsanisms were Pound between the Given Limits. |
Per Cent of Time |
Por Coot Woighted. |
|
0-500 |
20 |
38 |
0 |
|
500-1000 |
IS |
29 |
14. S |
|
1000-2000 |
10 |
19 |
19 |
|
2000-3000 3000- |
4 3 |
8 6 |
X6 x8 |
|
52 |
100 |
67. S Index of Frequency |
The maximum figure for the index of frequency passible by this method of computation would be 300, but it is rare indeed that any natural water gives an index of more than 100, and in the best stored waters the index is generally less than 10. The minimum of course is o.
The following figures show the niunbers of organisms found in three groups of lakes classified according t6 the index of the frequency as computed in the manner described:
LAKES CLASSIFIED ACCORDING TO THE INDEX OF FREQUENCY.
Number of Lakes and Reservoirs in the group
Limits of Frequency Index
Average index of frequency
Organisms per c.c. mean yearly average
Organisms per c.c, minimum yearly average . . Organisms per c.c, maximum yearly average . Organisms per c.c, mean average for 4 summer
months
Organisms per c.c, minimum average for 4
summer months
Organisms per c.c, maximum average for 4
summer months
Group I.
28 0-25
12 362
54 1413
414
66
1058
Group II.
18
25-50
39 776
441
2800
1023
227
4588
Group III.
20 50-100
78 1410
984
3090
196s
98s 7659
MICROSCOPIC ORGANISMS IN LAKES AlSfD RESERVOIRS 151
Relation of Odor to Index of Frequency. — Forty-five lakes and reservoirs classified according to odor, and to the index of frequency fell into the following groups:
Gronp.
Frequency Index
ODOR.
Practically none
Faint
Distinct
Decided
Strong
Number of Lakes.
Group I. o-as
2 8
5
I
I
17
Group II. aS-SO
3 3
4 4 o
14
Group III. So-xoo
O O
2
6 6
14
The relation between the frequency of occurrence of micro- scopic organisms and the odor of the water is thus seen to be very marked.
Relation to Area of the Lake. — The following figures show that the relation between the size of the lake and the frequency of occurrence of the organisms was not marked:
|
Group. |
Number of Laket. |
||
|
PrBduencv Index |
I o-as |
II 2S-S0 |
III SO-ioo |
|
Area in square miles: O.OO-O.IO 0.10-0.25 0.25-0.50 0.50-1.00 z .00 and over |
7 9 6 2 3 |
3 7 3 3 I |
8 4 3 2 4 |
|
27 |
17 |
21 |
152
THE MICROSCOPY OF DRINKINa WATER
Relation to Depth. — ^The relation between depth and fre- quency of occurrence of the microscopic organisms is shown as follows:
|
Group* |
Number of Lakm. |
||
|
Index of Frequency |
I o-as |
II as-so |
III SO-ioo |
|
Average depth in feet: o-io I0-20 20-30 30-40 40 and over |
6 12 3 0 I |
2 8 X X p |
2 XO 4 0 0 |
|
22 |
12 |
x6 |
Relation to Period of Storage. — The following figures show the relation between the nominal period of storage of water in a reservoir and the frequency of the occurrence of microscopic organisms:
|
Group. |
Number of Laket. |
||
|
Index of Frequency |
I o-as |
II as-so |
III so-xoo |
|
Period of storage, days: 0-50 50-100 100-200 200-500 500 and over |
I 2 7 8 2 |
I I 2 4 5 |
X X 3 7 2 |
|
20 |
13 |
14 |
MICROSCJOPIC ORGANISMS IN LAKES AND RESERVOIRS 153
Relation to Color of the Water.— There seems to be a slight tendency for the larger growths of organisms to occur in the lighter colored waters:
|
Group. |
Number of Lakes. |
||
|
Index of Frequency |
I 0-25 |
II 35-50 |
III 50-100 |
|
Color of water: 0-20 20-40 40-60 60-80 80-100 |
7 12 5 2 I |
4 9 4 0 0 |
3 13 5 0 0 |
|
37 |
17 |
21 |
Relation to Population on Watershed. — ^The following figures do not show any marked tendency for the organisms to increase as the population on the watershed increases, that is to say the element of pollution is not a controlling one. Yet we know that when the population per square mile is greater than any given in the table this may be a matter of importance.
|
Group. |
Number of Lakes. |
||
|
Index of Frequency |
I 0-25 |
II 2S-S0 |
III so- 100 |
|
Population per Sq. Mile: o-io 10-50 50-100 100-200 300 and over |
4 6 3 4 3 |
s 3 3 I 3 |
4 6 2 I 2 |
|
20 |
IS |
IS |
164
THE MICR08CX)PY OP DRINKING WATER
Occurrence of Anabena. — The following statistics show the relation between the occurrence of a typical blue-green alge and some of the various factors previously mentioned.
|
Oronp. |
Number of Lakes and Reetnroin. |
||
|
A |
B |
C |
|
|
Trouble from Anabena. |
None. |
SUght. |
Mttdu |
|
Area of Lake, miles: |
|||
|
a-. I |
24 |
14 |
ID |
|
.I-.2S |
9 |
6 |
14 |
|
.25-50 |
3 |
6 |
7 |
|
.50-1.00 |
2 |
0 |
z |
|
x.oo and over |
I |
2 |
a |
|
Average depth, feet: |
|||
|
o-io |
17 |
6 |
z |
|
10-20 |
10 |
7 |
17 |
|
20-30 |
I |
0 |
3 |
|
30-40 |
0 |
0 |
0 |
|
40- |
0 |
0 |
0 |
|
Length of storage, days: |
|||
|
0-50 |
5 |
I |
X |
|
50-100 |
I |
0 |
a |
|
100-200 |
2 |
4 |
z |
|
200-500 |
6 |
4 |
II |
|
500- |
2 |
I |
4 |
|
Color of water: |
|||
|
0-20 |
29 |
16 |
16 |
|
20-40 |
9 |
5 |
13 |
|
40-60 |
0 |
6 |
a |
|
60-80 |
2 |
I |
a |
|
80-100 |
I |
0 |
0 |
|
Population per sq. mile: |
|||
|
o-io |
15 |
5 |
9 |
|
10-50 |
15 |
8 |
8 |
|
50-100 |
7 |
8 |
5 |
|
100-200 |
4 |
3 |
4 |
|
200- |
4 |
3 |
7 |
Algae in the Croton Water-supply of New York City. — The present water-supply of New York City is taken from artificial reservoirs and natural lakes on the Croton River catchment area. In no case was the soil removed from the sites before the
MICBOSCOPICOBGANISMS IN LAKES AND RESERVOIRS 155
reservoirs were filled. Very heavy growths have accordingly occurred in all of the reservoirs and this is also true of the dis- tribution reservoirs in Central Park. The water as delivered in the city usually has a taste and odor caused by these growths. At times it is very noticeable and most unpleasant. It is largely for this reason that filtration of the water has been repeatedly urged in recent years.
The table on page 1 56 shows the index of frequency of the occurrence of growths of organisms in a number of the Croton reservoirs, together with various data that bear upon the problem.
Algae in the Metropolitan Water-supply of Boston. — Most of the reservoirs of the Metropolitan Water-supply of Boston are less troubled with algae than the reservoirs of the Croton supply. This may be seen by comparing the table on page IS7 with the preceding.
Algse in Massachusetts Water-supplies. — ^The relative occur- rences of algae in other reservoirs in Massachusetts are shown by the following indices of frequency :
|
City. |
Lake or Reservoir. |
Index of Frequency. |
|
Wobum |
Horn Pond |
IIO |
|
Winchester |
Middle Reservoir |
97 92 81 |
|
Soriiurfieldr |
Ludlow Reservoir |
|
|
I^eominster , ,,.,.,. |
Haynes Reservoir |
|
|
Cambridge |
Fresh Pond |
73 71 6S 56 ^^ 45 41 |
|
Canibridflre. |
Hobb's Brook |
|
|
Lynn |
Glen Lewis Reservoir |
|
|
Salem |
Wenham Lake |
|
|
Holvoke |
Whitine St. Reservoir |
|
|
Lvnn |
Walden Pond |
|
|
'^j "** Cambridge |
Stony Brook Reservoir Morse Reservoir |
|
|
Leominster |
39 37 33 33 21 |
|
|
Winchester |
North Reservoir |
|
|
Winchester |
South Reservoir Tatnuck Brook Storage Buckmaster |
|
|
Worcester |
||
|
N^orwood |
||
|
Lvnn |
Breeds Pond |
17 16 |
|
Hudson |
Gate Pond |
|
|
Lvnn |
Hawkes Pond |
IS 9 |
|
Worcester |
Leicester supply |
|
|
Salem |
Langham Reservoir |
|
|
Taunton |
Elders Pond |
4 |
|
T |
THE UICBC^COPT OF DRINKINO WATER
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HICBOSCOPICOROAmSHS In LAKES AND BESERV0QI8 157
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158
THE MICROSCOPY OF' DRINKING WATER
AIg» in Connecticut Water-supplies.— The following figures show the relative occurrences of algae in certain water-supplies of Connecticut.
|
I City. |
Lake or Reservoir. |
ladmof Praqueacy. |
|
BridffeDort |
Island Brook Suf^Iy |
83 |
|
New Haven ', |
Dawson T^ke |
70 |
|
Meriden |
Mcrimere T^ke. |
74 |
|
New BritAin |
Shuttle Meadow Lake |
# ^ |
|
Middletown |
Laurel Brook Reservoir Poquonnock River Supply Reservoir No. 6 |
45 |
|
Bridgeport |
40 |
|
|
Hartford |
29 32 |
|
|
Norwich |
Fairview Reservoir |
|
|
New Haven |
Whitney Lake |
21 |
|
Hartford |
Reservoir No. i |
18 |
|
BridffeDort |
Mill River Supply |
18 |
|
Hartford |
Reservoir No. ^ |
12 |
|
New Haven |
Wintergreen T^ke |
Z2 |
|
New Haven |
Saltondell Lake |
0 |
|
Hartford |
Reservoir No. 2 |
0 |
|
Hartford |
Reservoir No. 5 |
0 |
|
New London |
Lake Konomoc |
0 |
Algsd in Lake Ontario. — In August, 191 2, studies of the plankton were made by the author in Lake Ontario and the (Icnesce River, assisted by Mr. Melville C. Whipple and Dr. J. W. M. Bunker, instructors in the Harvard School of Engineer- ing. These studies illustrated the effect of horizontal currents on the distribution of the organisms near the shore, and also the relations between different classes of organisms. Speaking of the lake studies the report states:
*' Determinations of the microscopic organisms in the lake water were made on July 27th, August 2d and August 5th. In all of these samples diatoms and algae were present in considerable variety. Generally speaking, these were more numerous at the surface than at the bottom, although certain species were occasion- ally found in greatest abundance at some intermediate p>oint. In the samples collected near the shore, the number of microscopic organisms in the bottom samples varied according to the direc- tion of the wind. When the wind caused the surface-water to flow out at the bottom, the microscopic organisms were abundant
MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 159
in the bottom samples, but when the wuid was oflF shore and cold, deep water being brought in at the bottom, the nimibers of microscopic organisms in the bottom samples were lower. The microscopical examination of the surface-water along the beaches corroborated the temperature findings in indicating that with an off-shore wind the water at the shore line came from the bottom of the lake."
The protozoa that live upon bacteria and other microscopic organisms were most abundant in the immediate vicinity of the river mouth, and this was even true of the Crustacea and rotifera. On August isth a special study was made of the distribution of these larger organisms constituting the plankton, by the use of a plankton net. This net, kindly furnished by Prof. Charles Wright Dodge, was lowered to a depth of about 20 ft. and drawn to the surface at the rate of i ft. per second, in such a way as to collect the organisms present in about 100 gallons of water. The numbers of organisms found in the collected material were counted with the following approxiipate results:
PLANKTON IN LAKE ONTARIO
|
Samples from |
Approximate Number of Organisms per Liter. |
|
|
Rotifera. |
Crustacea. |
|
|
Genesee River, opposite Naval Resen^e Station Genesee River, at mouth |
12 28s 200 140 25 |
20 23 968 103s 30 |
|
Lake Ontario, i mile from mouth of river |
||
|
Lake Ontario J mile from mouth of river |
||
|
Lake Ontario i mile from mouth of river |
||
Self Purification in the Genesee River. — At the present time all of the sewage of Rochester is discharged into the (Jenesee River. The self-purification that takes place in the river in the six-mile reach between the main sewer outfall and the lake is due to a considerable extent to the microscopic organisms. The report says:
160 THE MICROSCOPY OP DRINKING WATER
" For convenience the results of the microscopical examina- tions of the river water have been summarized according to their natural classification, namely, (i) Bacteria,(2) Algas, (3) Protozoa, (4) Rotifera, and (4) Crustacea.
" Sedimentation is only one method by which the bacteria in the river are removed from the water. Another important factor is their destruction by larger microscopic organisms. These microscopic organisms, algae, protozoa, rotifera, Crustacea, etc., play an important part in the self-purification of the Genesee River during warm weather. A somewhat extended study of these organisms was made. Samples for microscopical examination were collected on different days at various points between the East Side Trunk Sewer and the lake at the surface, mid-depth and bottom. The variations in the relative numbers of the organisms of these different groups at various places in the river below the East Side Trunk Sewer illustrate in a typical way the biological action involved in the self-purification of a stream.
Immediately below the outlet of the trunk sewer there was a zone of heavy pollution within which the numbers of bacteria were very high, but the Crustacea relatively low. Below this point of maximum bacterial life, the numbers of bacteria decreased to the lake. In the vicinity of the intense bacterial pollution and for a short distance below it, the numbers of protozoa were high, as might be expected from the fact that these organisms consume bacteria as food. At the same time there was a slight increase in the algae, and their numbers were well maintained down-stream to the river mouth. These vegetable cells utilize as food the oxidized products of the organic matter from the sewage. In the lower course of the river, for two or three miles back from the lake, the rotifera and Crustacea made their appearance. They live upon the algae and bacteria and especially upon the protozoa. Large numbers of Crustacea were found in the lake hovering around the mouth of the river, waiting for the food that was being carried to them. Studies of these so-called plankton forms were made in the lake by the use of the plankton net, the results of which are
MICROSCOPIC OROANISMS IN LAKES AND RB8ERVOIBS 161
given above. These Crustacea serve as food for fish and that is why fish are attracted to the mouth of the river and why fishermen congregate along the breakwaters at the river mouth that extend about a third of a mile into the lake. These
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HSea from Lake Ontario
Fio. SI- — Changes in MicroscOfnc Organisms in the Genesee River between the Rochester Sewer Outlet and Lake Ontario. August, 1911.
changing biological conditions are illustrated by diagram in Kg. SI-
Forbes* Investigatioiis of the Illinois River. — A very important investigation of the plankton in the water in the Illinois River before and after the opening of the Chicago Drainage Canal was
162 THE MICROSCOPY OF DRINKING WATER
made by Forbes and Richardson of the University of Illinois. They found that there has been a threefold increase in the spring plankton since the canal was opened and the food-supply of the organisms increased by the turning of the sewage of Chicago into the river. In their very interesting paper published in 1913, they state:
" No change has recently occurred in the Illinois River system, or in the basin of the Illinois, to account for the increased productivity of its water except the opening of the sanitary canal connecting the Illinois and the Chicago rivers at the beginning of 1900. The effects of this occurrence on the plant and animal products of the stream may conceivably have been produced in one or more of these three principal methods: (a) by a mere increase of the waters themselves, which, in so slug- gish a stream as the Illinois, with bottom-lands so extensive and so widely overflowed by so small a rise of the river levels, will take effect mainly in great expansions of shallow water, long continued or permanently maintained, with muddy bottoms and more or less weedy shores — situations quite capable of producing a relatively enormous plankton as weU as an abundant supply of shore and bottom animals and plants; (6) by the addition of increased quantities of organic matter to the contents of the stream in the form of a larger inflow of sewage from Chicago and its suburbs, in condition to increase the plankton by increasing the supply of food available to the minute organisms which compose it; and (c) by the addition to the plankton of the river, of that of Lake Michigan brought down in the waters of the canal."
'* The efficacy of the first of these conditions is undoubted and that of the second is, generally speaking, quite possible. The importance of an abundance of organic matter in the water as a means of producing a rich plankton is, in fact, so well known that growers of pond fishes in Europe deliberately manure their ponds to increase the supply of food for their fish; and there is considerable evidence, also, that the plank- ton of the Elbe is largely increased by the sewage of Hamburg and Altona poured directly into that stream."
MICROSCOPIC ORGANISMS IN LAKES AND RESERVOIRS 163
In order to show the variations in the quantity of plankton in the river through the course of a year, the following figures are also quoted from their report.
QUANTITY OF PLANKTON IN THE WATER OF THE H-LINOIS RIVER AT HAVANA, ILL. BEFORE AND AFTER THE OPEN- ING OF THE CHICAGO DRAINAGE CANAL.
|
Month. |
Cubic Centimeters of Plankton per Cubic Meter of Water. |
|
|
1896. |
1909-10. |
|
|
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. |
.01 .01 .07 5.69 I 30 .71 1.44 1. 17 .38 1. 10 .02 .76 |
.01 .21 2.18 29.60 12.27 11.89 •23 .06 .10 2.58 1.38 .38 |
Algse in Ice. — ^Algae sometimes become frozen in the ice of ponds. They give the ice a dirty appearance and on decay may cause foul odors months after the ice is harvested. In artifidal ice algae may be concentrated in the " core," so as to produce a noticeable discoloration and taste.
CHAPTER X
SEASONAL DISTRIBUTION OF MICROSCOPIC ORGANISMS
The microscopic organisms found in water show variations in their seasonal occurrence as great and almost as character- istic as those of land plants. The succession of dandelions, buttercups, and goldenrod in our fields finds its counterpart in the succession of diatoms, green aigs, and blue-green algx in our lakes and ponds. If one examines the water of a lake continuously for a year some interesting changes in its flora and fauna may be observed. If the lake is a typical one the water during the winter will con- tain comparatively few organisms; in the spring various diatoms will ap- pear; these will disappear in a few weeks and in their place will come the green alga;; at the same time, or a little later, the blue- green algie may be found; in the fall both of these will vanish and the diatoms will appear again; as the lake freezes these in ' turn will dis- appear. Similar but less characteristic fluctuations take place among the animal forms. These facts are shown graphically in Fig. 52, which represents the seasonal changes that occur among the more important organisms in Lake Cochituate. The diagram is based on weekly observations
104
3 — i—?^
- ». ^ — ^yjl-^ «>
S ». — -_ — - .i«
^IC. 51. — Seasonal Distribulion of Micro- scupic Organisms in Lake Cuchiluatc.
SEASONAL DISTRIBUTION OF MICROSCOPIC ORGANISMS 165
extending over a number of years. The seasonal distributions of the diatoms^ algae, and protozoa, are so different that it is best to consider each class by itself.
Seasonal Distribution of Diatamacese. — ^In most natural ponds and storage reservoirs diatoms are far more abundant in the spring and fall than at other seasons. New growths seldom begin in the sununer or winter, but the spring and fall growths sometimes linger into the summer and winter for a niunber of weeks.
The occurrence of diatoms in ponds is greatly influenced by the vertical circulation of the water. They generally appear after the periods of stagnation and during the periods of complete vertical circulation. It has been found that in temperate lakes of the second order, which have well-marked periods of stagnation in summer and in winter, the spring and fall growths of Asterionella occur with great regularity and with about equal intensity, while in temperate lakes of the third order, which are stagnant only during the winter, the Asterionella growths in the autumn are either small compared with the spring growths or are lacking altogether. In deep ponds the spring growths occur earlier and the fall growths considerably later than in shallow ponds, thus again correspond- ing to the periods of circulation. In lakes of the third order diatoms are sometimes found during the summer after periods of partial stagnation.
Of the many genera of diatomaceae that are observed in water only those that are true plankton forms exhibit the spring and fall maxima. The most important of these are Asterionella, Tabellaria, Melosira, Synedra, Stephanodiscus, Cyclotella, and Diatoma. Other genera are more uniformly distributed through the year. All of these seven genera are sometimes, but not often, observed during the same season in the same body of water. As a rule certain ponds have cer- tain diatoms peculiar to them. For example, Lake Cochituate often contains large growths of Asterionella, Tabellaria, and Melosira: other diatoms are to be found, but they are seldom very numerous. Sudbury Reservoir, No. 3 of the Boston Water
166 THE UICR08C0PY OF DRINKING WATER
Works contains Asterionella, Tabellaria, and Synedra, but few Stephanodiscus or Melo^ra. In Sudbuiy ResermNr No. 3 only Synedra and Cyclotella are found. In the Ashland Reservoir Cyclotella usually predominates. Fresh Pond, Cam< bridge, Mass., is famous for its Stephanodiscus, and Diatoma is common in the water-supply of Lynn, Mass.
The genera that appear in any pond are not the same every year. In Lake Cochituate the spring growth in 1890 conasted of Asterionella and Tabellaria; in 1891 of .^terionella with a
Fig. 53. — Succession of Diatoms Id ChesUiut Hill Reservaii, 1891.
few Melosira; in 1892 of Melosira chiefly; in 1893 of Melosira and Asterionella; and in 1894 of Tabellaria, Asterionella, and Melosira. Furthermore, in any season it is seldom that two genera attain their maximum development at the same time — sometimes one appears first and sometimes another. The most interesting succession of genera that the author has observed occurred in 1892 in Chestnut Hill Reservoir of the Boston Water Works. The spring growth began in April and continued through July. For three months the total munber of diatoms present did not materially change, but
SEASONAL DISTRIBUTION OF MICROSCOPIC ORGANISMS 16/
during this time six different genera appeared on the scene, culminated one after another, and disappeared. This is shown in Fig. 53-
The explanation of the peculiar seasonal distribution of diatoms involves the answers to many questions. To what extent are diatoms influenced by light, by temperature, by mechanical agitation? To what extent are they dependent upon oxygen or carbonic acid dissolved in water? What sort of mineral matter do they require? These are questions not yet fully answered. Attempts have been made to solve the problems by experiment, but it has been found difficult to control all the necessary conditions in the laboratory.
The optimum temperature for the development of the diatomacefe is not known. Diatom growths have been observed at temperatures ranging from 35° to 75° F. In Lake Cochituate the average temperature of the water at the time of maximimi Asterionella growths is not far from 50°. In some lakes it is nearer 60°. Experimental evidence upon the subject is weak, but there is reason for believing that the optimum temperature for the diatomacete is lower than for the green or blue- green algsE.
Relation of«Light to Dia- tom Growth. — It is known that diatoms are very sensi- tive to light. They will not grow in the dark nor in bright sunlight. Experi- ments made by the author in which diatoms were al- lowed to grow in bottles at various depths below the surface have shown that their growth is nearly propor- tional to the intensity of the light. This is illustrated by Fig. 54. It will be noticed that near the surface,* where the light
*The scowth at the depth o( 6 inches was greatci than at the immediate â– urloce, wbeie the direct sunligbt naa tcN> strong.
|
,. 4.14.14, . |
â– -'-^ |
|
|
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168 THE MICROSCOPY OF DRINKING WATER
was strong, they multiplied rapidly, but below the surface the rate of multiplication was much slower, and at a certain depth no multiplication took place. This depth-limit of growth varied according to the color and transparency of the water, being greatest in the water having the least color. In one reservoir, where the color was 86, the limit of growth was 5 u.] in another, where the color was 6o, it was 12 ft.; and in another, with a color of 29, it was 15 ft. No observations were made in colorless waters, but in them the limit of growth is as great as 25 or 50 ft., and perhaps even much more than this.
The specific graxity of diatoms plays an important part in their seasonal distribution. In absolutely quiet water most diatoms sink to the bottom, but very slight vertical currents are sufficient to prevent them from sinking. A few forms appear to have a slight power of buoyancy, and some genera are somewhat motile. Diatoms also liberate oxygen gas dur- ing growth and this tends to give them buoyancy.
Diatoms are said to be positively heliotropic, that is, they tend to move toward the light. In some of the motile forms this power is quite strong. In most of the plankton genera this power is weak. They will not move upward toward the light through any great depth of water. It is possible, how- ever, that the power of heliotropism varies wit]j the intensity of the light, but experimental evidence on this point is lacking.
Diatoms require air for their best development. Exf)eri- ment has shown that they will not multiply in a jar where a thin layer of oil covers the surface of the water; that in cul- tures in jars of various shapes, the one that has the least depth of water and the greatest amount of surface exposed to the air will show the greatest multiplication; that in bottles exposed at the same depth beneath the surface of a reservoir, one with bolting-cloth tied over the mouth will show a greater develop- ment of diatoms than one tightly stoppered.
The nature of the food-material of diatoms is not well known. Observations seem to show that they require nitro- gen in the form of nitrates or free ammonia (perhaps both), silica, and more or less mineral matter, such as the salts of
SEASONAL DISTRIBUTION OP MICROSCOPIC ORGANISMS 169
magnesium, calcium, iron, manganese, etc., but the amounts of these various substances required has not been determined.
The facts at hand enable one to formulate a theory for the explanation of the occurrence of maximum growths of diatoms after the periods of stagnation and during the periods of cir- culation.
During the periods of stagnation the lower stratimi of water in a deep lake undergoes certain changes that are very pro- nounced if the bottom of the lake holds any accumulation of organic matter. The organic matter decays, the oxygen becomes exhausted, decomposition proceeds under the action of the anarobic bacteria, the free ammonia mcreases, and other organic and inorganic substances become dissolved in the water. During the period of circulation this foul water reaches the surface, further oxidation takes place, and compounds favorable to the growth of diatoms are formed. At the same time the vertical currents carry to the surface the diatoms, or their spores, that have been lying dormant at the bottom, where they could not grow because of darkness or because of the absence of proper food conditions. Carried thus toward the surface, where there is an abundance of light, air, and nutrition, they multiply rapidly. The extent of their develop- ment depends upon the amount of food-material present, the temperature of the water, and the amount of vertical circula- tion. If. the upper layers become stratified and the surface remains calm for a number of days the diatoms will settle in the water into a region where the light is less intense. If they sink far enough they enter a region where the light is not suf- ficient for their growth, and if they sink below the transition zone succeeding vertical circulation of the upper strata will not aflfect them. Unable to reach the surface by their own power they will sink to the bottom and remain through another period of stagnation.
In small reservoirs that are constantly supplied with water rich in diatom food and that are so shallow that even at the bottom the light is strong enough for their development, the seasonal distribution follows somewhat different laws. This
170 THE MICROSCOPY OF DRINKING WATER
is the case in many open reservoirs where ground-water is stored.
Seasonal Distribution of Chlorophyceae.— The Chlorophyceae are most abundant in water-supplies during the summer. They are seldom found in winter. The curve showing their develop- ment is more nearly parallel with the curve showing the tem- perature of the water than is that of any other class of organisms. The maximimi growth is usually in July or August, though some genera culminate as early as June and others as late as Septem- ber or even October. The late growths are usually associated with the phenomenon of stagnation.
The optimum temperature for the different genera is not known. It seems probable that most of the conunon forms are able to grow vigorously between 60° and 80° F. if their food-supply is favorable and the light sufficient. It b possible for some of the green alga; to become acclimated to considerable extremes of heat or cold. Protococcus nivalis is found in the arctic regions, and Conferva has been observed in water at a temperature of 115° F.
Seasonal Distribution of Cyanophyceae. — The seasonal dis- tribution of the Cyanophycea* is similar to that of the Chloro- phycea;, but as a rule the maximum growths occur a little later in the season. The Cyanophycea; seem to be attuned to a slightly higher temperature than the Chlorophyceae. They often show a great increase after a period of hot weather. Ana- baina, Clathrocystis, and Ccclospha^rium seldom give trouble unless the temperature of the water is above 70° F. This is the reason that blue-green alga; seldom give trouble in England. The surface water there seldom reaches this temperature even in summer.
Aphanizomcnon is more independent of temperature. It apparently prefers a lower temperature than most of the Cyano- phycea;. In some ponds it is present throughout the entire year, even when the surface is frozen. On one occasion it grew under the ice in Laurel Lake, Fitzwilliam, N. H., and became frozen into the ice to such an extent that the ice-cutters were alarmed at the green color. In Lake Cochituate, Aphanizomenon
SEASONAL DISTRIBUTION OP MICROSCOPIC ORGANISMS 171
reaches its greatest growth m the autumn. This accounts for the maximum of the curve of Cyanophyceae in Fig. 52 occurring in October instead of in August or September.
Schizomycetes and Fungi. — These forms have no well- marked periods of seasonal distribution. I'hey are liable to be found at any season. Mold hyphae are occasionally found at the bottom of lakes during the summer, and at the surface under the ice in winter. Crenothrix may be found in the stagnant water at the bottom of a deep lake during the sum- mer, and at all depths in the autimm after the overturning of the lower layers of water. Crenothrix has been observed during the summer in swamps in company with Anabaena and other Cyanophyceae. Attention is called to the possi- bility of mistaking the stems of Anthophysa for Crenothrix.
Seasonal Distribution of Protozoa. — The seasonal distri- bution of the Protozoa, taken as an entire group, is extremely variable and differs considerably in different ponds. No curve can be drawn that will represent all cases. In Lake Cochituate the curve has a major maximum in the spring, a minor maximum in the autumn, with the summer minimum lower than that in the winter. In Mystic Lake the curve has but one maximum — in the summer. These differences are due to the fact that the group of Protozoa is a broad one, and includes organisms that differ widely in their mode of life.
The Rhizopoda are found at all seasons of the year, but they are most numerous in the plankton in the autumn after the period of summer stagnation. These organisms live upon the ooze on the bottom and sides of ponds and upon twigs and aquatic plants. There they are found most abundantly in the summer. The vertical currents of the autumnal circula- tion scatter them through the water and cause the maximum number of floating forms to be observed during October and November. There is a minor maximum during the period of spring circulation. Some plankton forms, such as Actinophrys, are most abundant in summer.
Of the Flagellata, Euglena, Raphidomonas and Phacus are most abundant from June to September; Trachelomonas
172 THE MICROSCOPY OF DRINKINQ WATER
is found at all seasons, but is most common in the fall after the period of summer stagnation; Mallomonas is found from April to October, but is usually most abundant in the autumn; Cryptomonas occurs in some ponds only in the late fall and winter; Synura and Dinobyron are generally most nimierous in the spring and autumn, but heavy growths have been observed at all seasons; Uroglena seems to prefer cold weather, but vigorous growths have been noted in June.
The Dino-flagellata, Glenodinium and Peridinium, are usually most abundant during warm weather, but they are liable to occur at any season. Ceratium seldom appears before July, and it usually disappears before cold weather.
Of the Infusoria, most of the dUated forms prefer warm water; Codonella and Tintinnus occur after periods of stag- nation; Vorticella and Epistylis are distinctly summer organ- isms; and Bursaria and Stentor are also found in summer.
Adneta is most abundant during warm weather.
The Protozoa that attain their greatest development in summer are those forms that are closely allied to the vegetable kingdom, and that are perhaps more properly classed with the algaj: namely, the Dino-flagellata and some of the Flagellata that arc rich in chlorophyll. A few genera that occur most abundantly in the spring and fall have a brownish-green color like that of the diatoms, which also have spring and fall max- ima. The Ciliata that live upon decaying organic matter are attuned to a comparatively high temperature — about 75° F. This has been demonstrated by experiment, and it corresponds with the time of their observed maximum. Those Protozoa that exhibit a strictly animal mode of nutrition are most abun- dant at those seasons when there is plenty of food-material in the shape of minute organisms or fmely divided particles of organic matter. This partially explains why growths are sometimes present in the winter when bacteria are numerobs or after periods of stagnation when particles of organic matter from the bottom have been scattered through the water.
Seasonal Distribution of Rotifera. — Rotifera are found at all seasons of the year, but are most numerous between June and
SEASONAL DISTRIBUTION OF MICROSCOPIC ORGANISMS 173
November. In many ponds the maximum occurs in the autunm. Some genera are perennial, others are periodic in their occurrence. Anuraea and Polyarthra are found throughout the year, but their numbers rise and faU at intervals corresponding to the hatching season. Conochilus is often abundant in Jime, Asplanchna in July and August, and Synchaeta in August and September. The littoral Rotifera are most abundant during the sunmicr.
The Rotifera feed upon the smaller microscopic organisms, and their seasonal distribution is largely influenced by the amoimt of this food-supply. The reactions of the Rotifera to light, temperature, etc., are not well known.
Crustacea. — ^The number of Crustacea present at different seasons varies greatly in different bodies of water. It is influenced largely by the genera that are present. Different genera vary considerably in their seasonal distribution. Some are found at all seasons, while others occur only at certain times. The perennial forms may have several maxima dur- ing the year, corresponding to the hatching of different broods. As a rule Crustacea are most numerous in the spring, but minor maxima may occur during the sunmier and autumn and rarely in the winter.
Temperature, food-supply, and competition are said to be the chief factors that influence the seasonal distribution of the Crustacea.
For a full discussion of the seasonal distribution of the Crus- tacea the reader is referred to Dr. Birge's studies of the Crustacea of Lake Mendota. The organisms are given scant attention in this book because they have but little direct significance in public water-supplies.
Seasonal Distribution of Organisms in Lake Cochituate. — The irregularity of the seasonal occurrence of the micro- scopic organisms may be seen from Fig. 55, which shows the changes that took place in the water of Lake Cochituate during a period of five years.
THE MICROSCOPY OF DRINKING WATEE
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49)3ini 11193 'IVKi «»1 Eiin^ pi^nns JO Jaqnnit
CHAPTER XI
HORIZONTAL AND VERTICAL DISTRIBUTION OF MICRO- SCOPIC ORGANISMS
The plants and animals that inhabit lakes and ponds may be classified according to their habitat, but it is sufficient here to consider them either as littoral or limnetic.
The littoral organisms may be said to include all those forms that are attached to the shore or to plants growing on the shore, besides a host of others which, though free-swimming are almost invaribly associated with the attached forms.
The limnetic, or pelagic, organisms are those that make their home in the open water. They float or swim freely and are drifted about by everj- current. Collectively they make up the greater part of the plankton. They include almost all the troublesome odor-producing organisms in water-supplies. In the open water, however, one often finds some of the littoral forms that have been detached from the shore and scattered through the water by the currents, or that are parasitically attached to some of the limnetic forms. Then there are organ- isms that may be said to be facultative limnetic forms, that is, they are sedentary or free-swimming at will. The true limnetic forms, however, are the most important in water-supplies, and their horizontal and vertical distributions are now to be considered.
Horizontal Distribution. — The horizontal distribution of the limnetic organisms is usually quite uniform within any limited area, but through the entire body of a lake the num- ber of organisms may show considerable variation. This is quite noticeable in long, narrow reservoirs that have streams
175
176 THE MICROSCOPY OF DRINKING WATBB
entering at one end and discharging at the other. In such reservoirs the organisms are generally most numerous at the lower end. If, however, the water in the influx stream con- tains many organisms the numbers may be higher at the upper end, diminishing gradually as the water of the stream becomes mixed with that of the reservoir. Sometimes the mixing takes place slowly and the influent water passes as a current far into the reservoir. This tends to distribute the organisms in streaks. In lakes with uneven margins the horizontal distribution may vary greatly, and the number of organisms found in coves may be quite different from the nmnber foimd in the open water. The horizontal distribution of diatoms is influenced to some extent by the depth of the lake. There is in Massachusetts a lake covering about 250 acres. Near one side of it there is a deep hole, that has an area of about live acres, where the stagnation phenomena are very pro- nounced. When the growths of diatoms occur in the spring and fall the numbers are very much higher in the vicinity of this deep hole than elsewhere in the lake.
Areas of shallow flowage exert a marked effect on the hori- zontal distribution of the microscopic organisms.
The wind also has a great influence, and in many bodies of water it is the controlling influence. The organisms, par- ticularly the Cyanophycea^, are driven in the direction of the wind and accumulate toward the lee shore.
The undertow currents also play a very important part in the horizontal distribution of the organisms. Alga; thslt have developed within the transition zone may by a sudden increase in the wind movement be carried into the circulating waters near the surface.
Flotation of the Plankton. — Some of the microscopic organ- isms are heavier than water, some are lighter and many have about the same specific gravity. Various means are used by the heavier organisms to float themselves.
1. Some secrete a gelatinous watery envelope which b lighter than water.
2. Some form vacuoles.
HORIZONTAL AND VERTICAL DISTRIBUTION 177
â–
3. Some produce substances lighter than water, either
a. Gas confined in the upper parts of the bodies or
in special holders, or
b. Oily or fatty substances.
4. Some expand their surface area and thus increase the surface friction with the water. This is accomplished in several ways.
a. By the enlargement of the entire surface.
b. By the formation of grooves, or markings, as in
some of the diatoms.
c. By the attachment of many cells to form a filament
and by the development of long needle-like forms.
d. By the formation of special swinuning attachments,
as cilia, flagella, and the antennae and legs of Crustacea.
e. By the formation of colonies of organisms of con-
siderable size.
Vertical Distribution. — The laws that govern the vertical distribution of the microscopic organisms are more compli- cated than those which govern their horizontal distribution. The latter affect the organisms mechanically; the former vitally. While their specific gravity and the vertical currents produced mechanically or thermally play an important part, the amount of food-material and dissolved oxygen and the amount of heat and light influence the very life of the organisms.
In a lake of the second order the determining factors vary at different depths and at different seasons. In the summer, for example, the conditions above the transition zone are very different from those below it. Near the surface the water is warm, the li^ht is strong, oxygen is very abundant, and there are vertical currents. Carbonic is present early in the season. Near the bottom the water is cold, the light is weak, the oxygen may be exhausted, and the water is perfectly quiet. With these conditions chlorophyll-bearing organisms naturally thrive best above the transition zone. They seldom develop below it. Often they are found concentrated within the transition zone itself.
178
THE MICROSCOPY OP DRINKING WATER
It has been shown by experiment that the development of diatoms is greatest near the surface and that it decreases downward as the light decreases. In nature, however, it cannot be expected that the number of diatoms in the differ- ent layers of water will follow this law closely, because the diatoms are heavy and constantly tend to sink, and because the water above the transition zone is more or less stirred up. One would expect rather to find a uniform vertical distribution above the transition zone, and below it a rapid decrease in the number of organisms. Such a distribution is common. The following mstances of the vertical distribution of Asterionella and Tabellaria in Lake Cochituate may be cited in illustra- tion; in both instances the transition zone was located between 20 and 30 ft.
VERTICAL DISTRIBUTION OF ASTERIONELLA AND TABELLARIA IN LAKE COCHITUATE.
Depth in Feet.
Surface 10 ft. 20
25
30 40
SO 60
Numbers per c.c.
Asterioncll.i. May 7, 1891.
3752 3736 3716
1784
456
53^ 178
Tabellaria. May 24. 1890.
1886
1448
1396
484
298
96
This manner of distribution is most common during periods of rapid development, when a gentle breeze is stirring. In very quiet weather and during periods of declining growth diatoms sink rapidly, and at such times they may be found most numerous at the transition zone or at the bottom. Dur- ing periods of complete vertical circulation the vertical distribu- tion may be quite uniform from top to bottom. The diatoms found at the bottom of a deep lake are usually less vigorous than those near the surface.
HORIZONTAL AND VERTICAL DISTRIBUTION 179
The ChlorophyceaB and Cyanophyceae are much lighter in weight than the diatoms, and some of them contain oil globules and bubbles of gas. The forces tending to keep them near the surface are greater, therefore, than in the case of the diatoms. These forms are seldom found below the transition zone, and even above it show considerable variations at different depths. The Cyanophyceae especially collect near the surface. In quiet waters they often form unsightly and ill-smelling sciuns. Occasional exceptions to the general' rule are observed. Micro- cystis, for example, is usually more abundant in Lake Cochit- uate just below the transition zone than it is at the surface. On July 31, 189s, the numbers of standard imits of Micro- cystis at different depths were as follows: Surface, 94; 30 ft., 342; 60 ft., 140.
It is interesting to notice that a sudden wind may affect the vertical distribution of the Cyanophyceae and the Dia- tomaceae in opposite ways. It may tend to decrease the number of blue-green algae at the surface by preventing the formation of scums, while it increases the number of diatoms by prevent- ing them from sinking.
The Protozoa, as a class, seek the upper strata of water. Euglena sometimes forms a scum upon the surface. Uroglena, Synura, etc., are often most numerous in winter just beneath the ice. The Dino-flagellata are distinctly surface forms. Some of the Protozoa seem to avoid direct sunlight and keep away from the upper surface of the water, though they may be very abundant at a depth of one or two feet. These organ- isms as elsewhere pointed out, contain chlorophyll and perhaps ought to be classed as algae. The Cilia ta and those Protozoa that have a distinctly animal mode of nutrition are more irreg- ularly distributed through the vertical. The Rhizopoda are most abundant near the bottom.
Concentration of Organisms in the Transition Zone. — ^At times some of the microscopic organisms are more numerous in the transition than elsewhere in the vertical. An interest- ing illustration of this occurred in Lake Cochituate in the siunmer of 1896. Mallomonas are not ordinarily abundant
180
THE MICROSCOPY OF DmNKING WATER
in this lake, but on June 24 they suddenly appeared just below the upper boundary of the transition zone. At the mid- depth (30 ft.) there were 116 per c.c, at the bottom there were 42 per c.c. but at the surface there were none. They developed rapidly, and on August 4 there were 3640 at the mid-deptlL The growth continued until September, and during this time the largest number observed at the bottom was 276 per cc, while above the transition zone scarcely an individual was foimd. On July 17 the vertical distribution was as follows:
VERTICAL DISTRIBUTION OF MALLOMONAS IN LAKE
COCHITUATE, JULY 17, 1896.
|
Depth. |
Number per c.c. |
Temperature P. |
|
Surface |
0 |
77-3* |
|
10 ft. |
0 |
75-2 |
|
IS " |
2 |
62.0 |
|
20 '* |
14S4 |
47.7 |
|
2$ " |
794 |
43 7 |
|
30 ** |
S48 |
43.2 |
|
40 ** |
112 |
42.5 |
|
so " |
88 |
41.4 |
|
60 " |
64 |
40.8 |
Synura and other organisms have shown a similar vertical distribution and the phenomenon is probably more common than we used to think. Whether this concentration at the transition zone is due to food-material, to light, or to temperature is not definitely known. Mallomonas are motile and are known to be positively heliotropic. In the winter they are often nu- merous under the ice. It is possible that they have a low tem- perature attunement, and that in the instance above cited they collected as near the surface as their temperature attune- ment would permit. This would accord with the fact that they are most numerous in the spring and fall. It is possible that the dissolved gases are a factor in the problem and also the increased density and viscosity of the water at lower tem- peratures. Supersaturation of the water with oxygen at the transition zone has already been alluded to.
Another explanation also suggests itself. The organisms most frequently found concentrated at the transition zone,
HORIZONTAL AND VERTICAL DISTRIBUTION 181
partake of the animal nature, that is Synura, Dinobryon, Mallomonas and the like are classed by Calkins among the Protozoa. Presimiably they depend, in part at least, upon other organisms, as food — as for example, bacteria. It is possible that in the process of sedimentation the bacteria in a lake, are temporarily checked in their fall by reason of the greater density and viscosity of the colder water at the trans- ition zone, and that the Protozoa congregate there to devour them; while the Crustacea congregate there to devour the Protozoa. As the Protozoa mentioned also contain chloro- phyll, the process of phytosynthesis also takes place.
This explanation would not apply to the blue-green algae, one of which, Aphanizomenon, is often found concentrated in the transition zone.
Rotifera and Crustacea are often numerous above the transition zone, but on the other hand, they are commonly more numerous in or below it. Apparently their food-supply is a controlling factor. During the winter they are sometimes abimdant at the bottom. Different genera react differently to light, and heat. Some of them show a slight daily migra- tion toward the surface at night, and away from the surface in the daytime.
The Schizomycetes are usually more abundant at the bottom of a pond than at the surface. Mold hyphae are often numerous in winter just under the surface of the ice.
Adaptation of Organisms to Changed Viscosity of Water. — Although the density of water changes but slightly with variations in temperature its viscosity changes greatly. At 25® C. (77° F.) the viscosity of water is only one-half of what it is at 0° C. (32° F.), consequently the tendency of organisms to sink at 25° is about twice as great as at 0° C. Unless the organisms can adapt themselves to this change and in some way increase their buoyancy during warm weather they will sink to a colder stratum and perhaps even to the bottom. Possibly slight changes in the temperature of the water in the upper strata between day and night may be an important fac- tor in the vertical migration of certain Crustacea, the organisms
182
THE MICROSCOPY OF DRINKING WATER
rising to the surface as the water cools at night and sinking to lower strata as the sun warms the water.
Dr. C. Wcscnbcrg-Lund claims that certain organisms adapt themselves to changes in viscosity, by expanding during warm
a h c d e f
Vir.. 56. — Ilyalodaphnia. Showing; changes of shape supposed to adapt their flotation to (iiflcrcnt densitic's and vis(.H>sities of water, a, 6, and / are winter forms; c, J, and c arc summer forms.
ijOvyU M^
Fig. 57.-
a b c d
-Seasonal Changes in the Shape of Anuria.
J, r, and/, winter forms.
a, bf and c, summer forms;
weather, thus increasing the surface exposed to the water, or by changing their shape or the location of their center of gravity. This theory is interesting, but it has not been fully demon- strated. Dai)hnia hyalina is said to ho round-headed during the winter but point-headed during the summer; Bosmina coregoni enlarges in summer; Asplanchna priodonta becomes elongated;
HORIZONTAL AND VERTICAL DISTRIBUTION
183
vhile Ceratium hinindinella grows an extra horn that increases its floating power. Tabellaria increase the number of cells in their colonies and thus attain greater flotation and doubtless 3ther diatoms do the same. These changes take place at a tem- perature of 12 to i6° C. {47.6 to 5o.8° F.), that is during May uid June, and again in the autumn; and the change is not gradual but takes place in the course of two or three weeks.
FiO 58.— Vertical Dbtribution of Organisms in McGregor Lake, near Ottawa, Ontario. July it, igii,
Wesenberg-Lund has also shown that these variations ire regional as well as seasonal. There is a gradual decrease in TOliune of many well known plankton forms from the south to the north, and in regions where there is the greatest range of temperature there is also the greatest seasonal variation, rhe low temperature forms of the plankton tend to uniformity, 3Ut the high temperature forms in different lakes.
Studies at McGregor Lake near Ottawa. --Fig. 58 shows the distribution of certain organisms in McGregor Lake situated
184
THE MICROSCOPY OF DRINKING WATER
in the Province of Ontario a few miles north of Ottawa. Here in July, 191 1, it was found that the diatom, Tabellaria and the blue-green algae, Anabaena, were most abimdant near the surface, but that Dinobryon and Synura were much more abundant in the transition zone. The studies in this lake were of especial interest by reason of its high latitude. The full report by the author was published in the Annual Report of the Provincial Board of Health of Ontario, Canada for the year 191 1.
Average Conditions at Different Depths. — In spite of the tendencies of the organisms to choose their favorite habitat in a body of water, the mechanical efifects of winds, currents, gravity, and other factors are so great that in most ponds and reservoirs used for water-supply, except in very deep ones, the average number of organisms of all kinds through the year does not vary much at different depths. This is illustrated by the following table:
TABLE SHOWING THE RELATIVE NUMBER* OF MICROSCOPIC ORGANISMS OF ALL KINDS AT THE SURFACE, MID-DEPTH, AND BOTTOM OF THE RESERVOIRS OF THE BOSTON WATER WORKS.
|
Locality. |
Depth. |
i8»;o. |
1891. |
l8g2. |
1893. |
1894. |
1895. |
1896. |
|
Surface |
454 |
736 |
523 |
389 |
416 |
355 |
507 |
|
|
Lake Cochituate |
30 ft. |
304 |
569 |
528 |
33^ |
365 |
373 |
657 |
|
60 ft. |
357 |
650 |
626 |
316 |
309 |
353 |
544 |
|
|
Sudbury Reservoir |
Surface |
68 |
322 |
268 |
116 |
45 |
61 |
87 |
|
No. 2 |
13 ft. |
80 |
273 |
256 |
98 |
49 |
S6 |
120 |
|
25 ft. |
64 |
268 |
229 |
98 |
33 |
47 |
78 |
|
|
Sudbury Reservoir |
Surface |
152 |
277 |
514 |
381 |
289 |
621 |
524 |
|
No. 3 |
iS^t. |
182 |
267 |
523 |
303 |
194 |
543 |
467 |
|
30 ft. |
131 |
323 |
481 |
3" |
179 |
485 |
498 |
|
|
Ashland Reservoir |
Surface |
50 |
129 |
269 |
112 |
28 |
57 |
94 |
|
20 ft. |
38 |
95 |
268 |
84 |
20 |
35 |
108 |
|
|
40 ft. |
25 |
83 |
235 |
66 |
20 |
25 |
106 |
|
|
Hopkinton |
Surface |
87 |
105 |
189 |
||||
|
Reser\'oir |
25 ft. 50 ft. |
52 72 |
58 53 |
118 104 |
♦For the years 1890 to t8o3 the results were given in Number of Organisms per c.c Since Jan. i. 1893. the results have been given in Number of Standard Unit* per c.c. (One standard unit equals 400 square microns.)
HORIZONTAL AND VERTICAL DISTRIBUTION 185
The vertical distribution varies at different seasons, as the following table illustrates:
TABLE SHOWING THE RELATIVE NUMBER OF ORGANISMS (STAND- ARD UNITS) PER C.C. AT THE SURFACE, MID-HEPTH, AND BOTTOM OF THE RESERVOIRS OF THE BOSTON WATER WORKS DURING 1895.
|
1 |
s |
|||||||||||||
|
LociUty. |
Uept |
" i |
1 |
1 |
1 < |
S |
i |
1 |
1 |
i J |
1 |
^ |
1 |
3 |
|
Siirfa |
IM |
^Rn |
||||||||||||
|
4JJ |
Hi |
|||||||||||||
|
SuilbDry Reiervoir |
Surim |
'â– 6 |
9 |
;; |
il |
" |
& |
ifl; |
i |
S |
i! |
1? |
511 47 |
|
|
Sadbury Reacrvolr |
SurfK jofi |
*1 |
4 |
;; |
61 46 |
^Bâ– . |
â– ai |
IfiTS |
l4si |
'•1% |
=K |
11 |
'& |
|
|
HurfK |
e n |
V |
in |
7rt |
i«| rs |
?" |
11 |
,, |
||||||
|
40(1 |
II |
to |
A 36 |
64 |
— |
ji |
.y |
ib |
IS |
|||||
|
Hopklnton RcKr- |
Surf. |
0. 4; |
SO |
»4J |
186 |
4. |
13 |
'-S |
||||||
|
,oir. |
SOU |
â– â– |
* |
" |
76 |
SI |
35 |
>M |
60 |
A futther analysis of the results at Lake Cochituate shows the vertical distribution of the different classes of organisms to be as follows:
|
DiMO- |
Chlorn. phyccs. |
ph''"â„¢. P""â„¢"' Roii'""- |
MiKsUn- |
ToUl. |
||
|
Suriace Bottom, 60 ft.. |
144 i6o' |
75 16 |
108 67 |
.7 ! . i |
4 |
3SS 3S3 |
t Chiefly Crenothrii.
CHAPTER Xn ODORS IN WATER-SUPPLIES
The senses of taste and odor are distinct, but they are closely related to each other. There are some substances, like salt, that have a taste but no odor, and there are other substances, like vanilla, that have a strong odor but no taste. Many of the so-called tastes arc really odors, the gas or vapor given off by the substance tasted reaching the nose not only through the nostrils but through the posterior nares. Thus an odor " tasted " is often stronger than an odor smelled.
Chemically pure water is free from both taste and odor. Water containing certain substances in solution, as sugar, salt, iron, may have a decided taste but no odor. Such taste producing substances are met with in mineral waters or in brackish or chalybeate waters, but as a rule they are not offensive and they seldom affect large bodies of water. Most of the bad tastes observed in drinking water are due not to inorganic but to organic substances in solution or suspension and to microscopic organisms. These produce odors as well as tastes. The subject may be pursued therefore from the standpoint of odor alone, though in many instances the best way to observe the odor of the water is to taste it.
Water taken directly from the ground and used immediately is usually odorless. In certain sections of the country deep well water has a sulphurous odor. Contaminated well water or water drawn from a swampy region may be somewhat moldy or unpleasant.
Almost all surface-waters have some odor. Many times it is too faint to be noticed by the ordinary consumer, though it can be detected by one whose sense of smell is carefully
186
ODORS IN WATER-SUPPLIES 187
trained. On the other hand, the water in a pond may have so strong an odor that it is ofiFensive several hundred feet away. Between these two extremes one meets with odors that vary in intensity and in character, and that are often the source of much annoyance and complaint.
Classification of Odors — It is difficult to classify the odors of surface-waters on a satisfactory basis, but they fall into three general groups: i. Odors caused by organic matter other than living organisms. 2. Odors caused by the decomposi- tion of organic matter. 3. Odors caused by living organisms.
Odors Caused by Organic Matter. — The odors caused by organic matter other than li\ing organisms may be included under the general term vegetable. They vary in character in different waters and at different seasons. It is difficult to find terms that will describe them exactly. It is seldom that two observers will agree as to the most appropriate descriptive adjective. To one person the odor of a water may be straw- like, to another swamp-like, to another peaty. This is due to the fact that the sense of smell in man is not well ciUtivated. In practice, therefore, it has become customary among analysts to use the general term vegetable instead of the terms straw-like, swamp-like, marshy, peaty, sweetish. The intensity of an odor may be indicated by using the prefixes very faint, faint, distinct, decided, very strong. A better method, however, is to use numerical prefixes, which may be approximately defined as shown in table on p. 188. According to this method the expres- sion "3 f " would indicate a " distinct fishy odor," "2 v " a " faint vegetable odor," etc. The reader will understand that the above definitions are far from exact, and that the intensity of odors varying in character canont be well compared. A faint fishy odor, for example, might often attract more attention than a distinct vegetable odor. Heating a water usually intensifies its odor. In the laboratory the " cold odor " is observed by shaking a partly filled bottle of the water and immediately removing the stopper and applying the nose. The " hot odor " is obtained by heating a portion of the water in a tall beaker covered with a watch-glass to a point just short of
188
THE MICROSCOPY OF DRINKmO WATER
boiling. When sufficiently cool the cover is slipped aside and the observation made. A water that has a faitU odor when cold may have a distinct odor when hot.
|
Numerical Value. |
Terra. |
Approximate Definitkm. |
|
o |
None. |
No odor perceptible. |
|
I |
Very Faint. |
An odor that would not be ordinarily detected by the average consumer, but that could be obser\'er. |
|
2 |
Faint. |
An odor that the consumer might detect if his attention were called to it, but that would not otherwise attract attention. |
|
3 |
Distinct. |
An odor that would be readily detected and that might cause the water to be regarded with disfavor. |
|
4 |
Decided. |
An odor that would force itself upon the attention and that might make the water unpalatable. |
|
5 |
Very Strong. |
An odor of such intensity that the water would be absolutely unfit to drink (a term to be used only in extreme ca.ses). |
Most of the vegetable odors are caused by vegetable matter in solution. Brown-colored waters invariably have a sweetish- vegetable odor, and the intensity of the odor varies almost directly with the depth of the color. Both color and odor are due to the presence of certain glucosides, of which tannin is an example, extracted from leaves, grasses, mosses, etc. In addition to the odor, these substances have a slight astringent taste. Colorless waters containing organic matter of other origin may have vegetable odors, but they are usually less sweetish and more straw-like or peaty. Akin to the vegetable odors are the earthy odors caused by finely divided particles of organic matter and clay. The two odors are often associated in the same sample.
Odors of Decomposition. — Odors produced by the decom- position of organic matter in water are not uncommon. They
ODORS IN WATER-SUPPLIES 189
are described, somewhat imperfectly, by such terms as moldy^ musty, unpleasant, disagreeable, offensive. An unpleasant odor is produced when the vegetable matter in water begins to decay. It may be said to represent the first stages of decomposition. As decomposition progresses the unpleasant odors become disagreeable, and then offensive. It is seldom that the decom- position of vegetable matter in water produces odors worse than decidedly unpleasant. The disagreeable odors usually can be traced to decaying animal matter, and, as a rule, offen- sive odors are observed only in sewage or in grossly polluted water. The terms moldy and musty are more specific than the terms unpleasant, disagreeable, and offensive, but they are difficult to define. They are quite similar in character, but the musty odor is more intense and is usually applied only to sewage-polluted water. The moldy odor suggests a damp cellar, or perhaps a decaying tree-trunk in a forest. The bacteriologist will recognize this odor as similar to that given off by certain bacteria growing on nutrient gelatine.
The odors of decomposition naturally are associated with the odors of the other groups, and one often finds it conven- ient to use such expressions as distinctly vegetable and faintly moldy, i.e,, "3v-f2m," or decidedly fishy and disagreeable, i.e., " 4f +4d."
Odors Caused by Organisms. — The odors of drinking water due to the presence of living organisms are the most important because of their common occurrence, because of their offensive nature, and because they affect large bodies of water. It is only within recent years that these odors have been well understood, and even now there is much to be learned about the chemical nature of the odoriferous substances and their relation to the life of the organisms. At one time it was supposed that it was only by decay that the organisms became offensive. It is now a well-established fact that many living organisms have an odor that is natural and peculiar to them, just as a fresh rose or an onion has a natural and peculiar odor. It has been found, also, that in most cases — and it may be true in all cases — the odor is produced by compounds analogous
190 THE MICROSCOPY OF DRINKING WATER
to the essential oils. In some cases the oily compounds have been isolated by extraction with ether or gasoline. Odors due to these oils have been called " odors of growth " because the oils are produced during the growth of the organisms. The oil globules may be seen in many genera if they are examined with a sufficiently high power. They are usually most numer- ous in the mature forms and are often particularly abundant just before sporulation or enc>'stment. The production of the oil represents a storing-up of energy. The odors have been called " odors of disintegration," because they are most notice- able when the breaking up of the organism causes the oil globules to be scattered through the water. It is sufficient, however, to call them the " natural odors " of the organisms, to distinguish them from the very different odors produced by their decomposition.
It was stated in Chapter VI that the microscopic organ- isms are not found in ground-waters (except when stored in open reservoirs) or streams in sufficient abundance to cause trouble. It is in the quiescent waters of ponds and lakes and reservoirs that they develop luxuriantly, and it is to the reser- voir that one should look first when investigating the cause of an odor in a public water-supply.
The littoral organisms found on the sides of reservoirs include the flowering aquatic plants, the Characea) and the filamentous algx, of the vegetable kingdom and the fresh-water sponge, Bryozoa, etc., of the animal kingdom. The effect which they exert on the odor of a water is difficult to determine because they arc seldom found in a reservoir where the floating micro- scopic organisms are wholly absent. In many cases where a peculiar odor of a water has been charged to some of these littoral forms, subsequent investigation has made it probable that the odor was really caused by limnetic organisms that had been overlooked in the first instance.
Speaking generally it may be said that in reser\'oirs that are large and deep the organisms attached to the shores pro- duce little or no effect on the odor of the water; and that in small shallow reservoirs where the aquatic vegetation is thick
ODORS IN WATER5UPPLIES 191
they do not impart any characteristic " natural " odor, but may produce a sort of vegetable taste and a disagreeable odor due to decomposition.
Odors of Littoral Plants. — Some of the littoral aquatic plants, such as Myriophyllum and a number of the filamentous algae, possess a natural odor that is strongly " vegetable " and, at times, almost fishy; but the odor is obtained only when the plants are crushed or when fragments are broken off and scat- tered through the water. Under ordinary conditions of growth in a reservoir this does not happen and therefore no odor is imparted to the water except through decomposition.
There are on record some apparent exceptions to the rule that the attached growths cause no odor. Hyatt described a growth of Meridion circulare at the headwaters of the Croton River, in 1881, that was supposed to have affected the entire supply of New York City; Rafter has connected odors with Hydrodictyon utriculatum and other Chlorophyceae; Forbes investigated a water-supply where a growth of Chara was thought to be the cause of a bad odor; Tighe has also reported a troublesome growth of Chara at Holyoke. Weston has stated that serious trouble was caused in Henderson, N. C, by an extensive growth of Pectinatella. All of these caseis where odors in water-supplies have been attributed to certain littoral organ- isms lack coroboration.
The author once examined a reservoir where a mass of Melosira varians several feet thick covered the slopes to a con- siderable depth. A severe storm tore away the fragile fila- ments, and masses of Melosira passed into the distribution- pipes and caused a noticeable vegetable and oily odor in the water.
Cucumber Taste in Farm Pond. — In connection with the relation of the littoral organisms to odors in water-supplies some reference should be made to the " cucumber taste " thwt has been a frequent cause of complaint against the Boston water-supply. In 1881 the trouble was very severe. The water had a decided odor of cucumbers, which was intensified at times to a " fish-oil " odor. Heating made the odor very strong and
192 THE MICROSCOPY OF DRINKING WATER
offensive. A noted expert made an examination and concluded that the seat of the trouble was in Farm Pond — one of the sources of supply. This pond was so situated that all the water of the Sudbury system passed through it on its way to the dty. Chemical analysis of the water and microcsopical examination of the mud failed to reveal the cause of the odor. It was found, however, that fragments of fresh-water sponge (Spon- gilla fluviatalis) were constantly collecting on the screens and that these had the " cucumber odor." It was decided therefore that the fresh-water sponge was the cause of the odor. The conclusion was quite generally accepted and the report has been quoted extensively.
At that time some water experts disagreed with this opin- ion. They claimed that the amount of sponge foimd in the pond was not sufficient to produce the odor. In the light of modem microscopical examinations we have come to believe that the dissenters were right and that the fresh-water sponge was not the cause of the cucumber odor. The author took masses of Spongilla and allowed them to rot in a small quan- tity of water till the odor was unbearable. This water was then diluted with distilled water to see how large a mass of water the decayed sponge would affect. It was found that with a dilution of i to 50,000 there was no perceptible odor. At this rate it would take a mass of sponge several feet thick over the entire bottom of Farm Pond to produce an odor as intense as that observed in 1881. Moreover the odor pro- duced by decaying sponge is not the " cucumber odor," although similar to it.
There is good reason to believe that the cucumber odor observed in 188 1 was due to Synura. One need not dispute the observation that the sponge that collected on the Farm Pond screens had the cucumber odor, for no doubt the sponge was covered with Synura, as it is often covered with other organisms. It is not surprising, either, that the Synura should have been overlooked in the water, because the organism disintegrates readily and a comparatively small number of colonies is able to produce a considerable odor. The times
ODORS IN WATER-SUPPLIES 193
of the occurrence of the odor — ^namely, in the spring and autumn — are worth noting, as they correspond with the seasons when Synura grows best and when it is most commonly foimd.
In Februar}', 1892, the cucumber taste again appeared in the Boston water. This time it was definitely traced to Synura that was growing in the water just under the ice in Lake Cochituate. Since then it has reappeared at intervals in other parts of the supply — notably in Basin 3 and Basin 6. It has been found that 5 or 10 colonies per c.c. are sufficient to cause a perceptible odor.
Synura has often been the cause of bad odors in the Croton supply of New York.
Odors of the Plankton. — The floating microscopic organisms, or the plankton, are responsible for most of those peculiar nauseating odors that are the cause of complaint in so many public water-supplies. In most, if not in all, cases the odor is due to the presence of an oily substance elaborated by the organisms during their growth. This has been proved by long-continued observations and experiments, during the course of which the following facts have been noted:
The odors referred to vary in character. They are difficult to describe, but they can be readily identified. Particular odors are associated with particular organisms. If an organ- ism is present in sufficient numbers its particular odor will be observed; if it is not present in sufficient numbers its odor will not be observed. Further, with some exceptions the intensity of the odor varies with the number of organisms present. If water that contains an organism which has a natural odor is filtered through paper, the odor of the filtered water * will be much fainter than before, and the filter-paper on which the organisms remain will have a strong odor. If the organisms are concentrated by the Sedgwick-Rafter method, the concentrate will have a decided taste and odor. If these organisms are placed in distilled water, the water will acquire
* In some cases the odoriferous substances from the organisms pass through the filter, and the disintegration of the organi:-ms gives the filtered water an increased odor over the unfiltcred water.
194 THE MICROSCOPY OF DRINKINa WATER
the odor of the original water. Thus, the relation between particular odors and particular organisms has been well estab- lished. Indeed, in the absence of a microscopical examination^ experienced observers are often able to tell the nature of the organisms present by a simple observation of the odor.
That the odors are not due to the decomposition of the organism is proved by the character of the odors themselves and by the fact that they are not accompanied necessarily by large numbers of bacteria or by the presence of free ammonia or nitrites. Further, when the organisms do decay, the bacteria increase in number and the odor of the water changes in char acter.
The natural odor is given off by some substance inside the organism, and when this substance becomes liberated the odor is more easily detected. The odor is intensified by heat- ing, by mechanical agitation, by pressure, and by change in the density of the water containing the organisms. Many of the odor-producing organisms are very delicate. Heat- ing breaks them up and drives off the odoriferous substances. The flow of water through the pipes of a distribution system is sufficient to cause the disintegration of many forms, and it is a matter of common observation that in such cases the odor of a water at the service-taps is more pronoimced than at the reservoir. If the density of a water is increased by adding to it some substance, such as salt, the organisms may become distorted if not actually broken up. This causes an intensifica- tion of their odor. Increased pressure leads to the same result.
The natural odor of the organisms is due to some oily sub- stance analogous to those sub;>tanccs found in higher plants and animals, and that give the odor to the peppermint and the herring. The fact was noted long ago that the addition of salt to water that was affected with certain odors developed an oily flavor. INIany of the odors caused by organisms are of a marked oily nature. The oil globules in these organ- isms may be observed with the microscope. The number of oil globules varies according to the age and condition of the
ODORS IN WATER-SUPPLIES 195
organisms, and the intensity of the odor varies with the num- ber of oil-globules present. Finally, the oily substances have been extracted from the organisms and it has been found that they possess the same odor as that observed in the water containing them.
Odors of Essential Oils* — A series of experiments was made at one time to show that the amount of oil present in the organisms was sufficient to account for the odors observed in drinking water. Some of the familiar essential oils, such as oil of peppermint, oil of clove, cod-liver oil, etc., were diluted with distilled water, and the amoimt of dilution at which the odor became unrecogni- zable was noted. The oil of peppermint was recognized when diluted i: 50,000,000; the oil of clove, i: 8,000,000; cod- liver oil, i: 1,000,000; etc. The odor of kerosene oil could not be detected when diluted i: 800,000. The amoimt of oil present in water containing a known number of organisms was estimated for comparison. It was found that in water containing 100 colonies of Synura per c.c. the dilution of the Synura oil was i: 25,000,000; and that in a water with 50,000 Asterionella per c.c. the dilution was only i: 2,000,000. Thus, the production of the odor by the oil is quite within the range of possibility. An interesting fact brought out by the experi- ments was that the odor of the oils varied with different degrees of dilution not only in intensity but in character. On one occasion seven people out of ten who were asked to observe the odor of very highly diluted kerosene oil declared that it smelled like " perfumery." This variation of the character of the odor with its intensity is important to notice, as it accounts for the different descriptions of the same odor in a water-supply at different times and by different people.
The nature of the odoriferous oils or oily substances is not well known. Calkins, who isolated the odoriferous prin- ciple of Uroglena with gasoline and ether, describes it as being similar to the essential oils. It was non-volatile at the tem- perature of boiling water. Jackson and Ellms extracted a similar substance from Anaba^na with gasoline. On standing it oxidized and became resinous. It contained needle-like
196 THE MICROSCOPY OF DRINKING WATER
crystals. Experiments by the author have shown that the oils of Asterionella and Mallomonas are quite similar in char- acter.
Most, if not all, of the organisms produce oil during their growth to a greater or less degree. In many cases it is quite odorless. Water is often without odor even when large num- bers of organisms are present. This is either because the organisms have not produced oil, or because the oil is odor- less. Sometimes water rich in organisms will have an oily flavor with no distinctive odor. This is true in the case of some species of Melosira. Many organisms impart a vegetable and oily taste, without a distinctive odor. This is true of Synedra pulchella and Stephanodiscus. There are, moreover, microscopic organisms that produce oils that have a distinct- ive odor, but that occur in drinking water in such small num- bers that the odor is not detected. The organisms that have a distinctive odor and that are found in large nmnbers are comparatively few. Not more than twenty-five have been recorded and only about half a dozen have given serious trouble. More extended observations may lengthen this list.
Odors of Particular Organisms. — The distinctive odors pro- duced by these organisms may be grouped around three general terms — aromatic, grassy, and fishy — and for convenience they may be tabulated as in the table on page 197.
Aromatic Odors. — The aromatic odors are due chiefly to the Diatomacex. The trongest odor is that produced by Asterio- nella. The character of this odor changes with its intensity. When few organisms are present the water may have an unde- finable aromatic odor; as they increase the odor resembles that of a rose geranium; when they are very abundant the odor be- comes fishy and nauseating. The other diatoms given in the table produce the aromatic odor only when present in very large numbers. There are two protozoa that have an aromatic odor. The odor of Cryptomonas is sweetish and resembles that of the violet. The odor of Mallomonas is similar to that of Cryptomonas, but when strong it becomes fishy.
ODORS IN WATER-SUPPLIES
197
|
Group. |
Organism. |
Natural Odor. |
|
ASOMATIC |
DlATOMACEiE |
|
|
Odor. |
Asterionella |
Aromatic — geranium — fishy. |
|
Cyclotella |
Faintly aromatic. |
|
|
Diatoma |
Faintly aromatic. |
|
|
Meridion |
Aromatic. |
|
|
Tabellaria ' |
Aromatic. |
|
|
Protozoa |
• |
|
|
Cryptomonas |
Candied violets. |
|
|
MaUomonas |
Aromatic — violets — fishy. |
|
|
Grassy |
CYANOPHYCEiE |
|
|
Odor. |
AnabaMia |
Grassy and moldy — green-corn — ^nasturtiums, etc. |
|
Rivularia |
Grassy and moldy. |
|
|
Clathrocystis |
Sweet, grassy. |
|
|
Ccelosphxrium |
Sweet, grassy. |
|
|
Aphanizomenon |
Gra.ssy. |
|
|
Fishy |
CHLOROPHYCEiE |
|
|
Odor. |
Volvox |
Fishy. |
|
Eudorina |
Faintly fishy. |
|
|
Pandorina |
Faintly fishy. |
|
|
Dictyosphaerium |
Faintly fishy. |
|
|
Protozoa |
||
|
Uroglena |
Fishy and oily. |
|
|
Synura |
Ripe cucumbers — bitter and spicy tatse. |
|
|
Dinobryon |
Fishy, like rockweed. |
|
|
Bursaria |
Irish moss — salt marsh — fishy. |
|
|
Peridinium |
Fishy, like clam-shells. |
|
|
Glenodinium |
Fishy. |
Grassy Odors. — The grassy odors are produced by the Cyano- phyceae. Anabajna is the most important organism of this class. There are several species that have slightly different odors. The grassy odor is usually accompanied by a moldy odor, which is probably due to decomposition, as this organism decays rapidly. When very strong the odor of Anabacna much re- sembles raw green-corn J or even a nasturtium stem. The pre- vailing odor, however, is grassy^ i.e. the odor of freshly cut grass. The other blue-green alga^ have odors that may be called grassy, but they are less distinctive than in the case of Anabsena.
Fishy Odors. — The fishy odors are the most disagreeable of any observed in drinking water. That produced by Uroglena is per-
198 THE MICROSCOPY OF DRINKING WATER
haps the worst. It is quite common. Water rich in Uroglena has an odor not unlike that of cod-liver oil. The odor of Synura is ahnost as bad and ahnost as conmion. It resembles that of a ripe cucumber. Synura also has a distinct bitter and spicy taste. It " stays in the mouth " and is most noticeable at the back part of the tongue. Glenodinium and Peridmixmi both produce fishy odors. The latter somewhat resembles clam- shells. Dinobryon has a fishy odor and suggests sea-weed. The odor of Bursaria is said to be like that of Irish moss. It also reminds one of a salt marsh. With certain degrees of dilution some other Protozoa have the salt-marsh odor, remind- ing one of the sea. Fishy odors are said to be produced by Volvox, Eudorina, and Pandorina. These Chlorophyceae are sometimes classed with the Protozoa, so that it may be said in a general way that the fishy odors are produced by micro- scopic organisms belonging to the animal kingdom.
Odors of Decomposition. — Some of the microscopic organisms have distinctive odors of decomposition. The Cyanophyceae when decaying give a " pig-pen '* odor. Beggiatoa and some species of Chara give the odor of sulphureted hydrogen. All the odors given off by the decomposition of microscopic organ- isms arc offensive. They are particularly so when the organisms contain a high percentage of nitrogen. Jackson and Ellms, in an interesting study of the decomposition of Anabxna circinnalis, found that that organism contained 9.66 per cent of nitrogen. They found that the " pig-pen " odor was due " to the breaking down of highly organized compounds of sulphur and phosphorus and to the presence of this high percentage of nitrogen. The gas given off during decomposition was found to have the following composition :
Marsh-gas 0.8%
Carbonic acid i . 5%
Oxygen 2.9%
Nitrogen 12.4%
Hydrogen 82 . 4%
100.0%
ODORS IN WATER-SUPPLIES 199
The gas that remamed dissolved in the water containing the Anabaena was practically all CO2 and represented a large per- centage of the total gas produced. "
Besides the odors above described, water-supplies some- times become affected with what have been called " chemical odors" — such as those of carbolic acid, creosote, tar, etc. They can be traced usually to some pollution by manufactur- ing waste, though a vigorous decomposition of organic matter has been known to give an odor resembling carbolic acid. Similar odors are sometimes caused by the coating on the inside of new distribution-pipes.
Occurrence of Different Odors in Massachusetts Reservoirs. — The extent to which water-supplies are afficted with odors was well shown by the investigations of the Massachusetts State Board of Health. Out of 71 water-supplies taken from ponds and reservoirs, 45, or 63 per cent, were foimd to have given trouble from bad tastes or odors, and about two thirds of these had given serious trouble. Calkins has stated that in 1404 samples from surface-water supplies in Massachusetts odors were observed as follows:
nA^w P^r Cent of
^°^' Samples Affected.
No odor 20
Vegetable 26
Sweetish 7
Aromatic 6
Grassy 15
Fishy 3
Moldy 10
Disagreeable 6
Offensive 7
The intensity of these odors was not stated. Many of them probably were not strong enough to cause complaint.
It must not be inferred from this that Massachusetts is more afficted in her surface-water supplies than other sections of the country. The same troubles are observed almost every- where. It is only because the Massachusetts supplies have been more carefully studied than elsewhere that attention has
200 THE MICROSCOPY OF DRINKING WATER
been drawn to them. In a previous chapter it was stated that the microscopic organisms are widely distributed both in this country and abroad. Wherever they are foimd in abundance they must inevitably aflfect the odor of the D^ter.
Are Algae Injurious? — The question is often asked, " Are growths of organisms such as Asterionella, Synura, etc., injurious to health?" This cannot be answered authoritatively, but from the data at hand it is believed that such organisms are not injuri- ous— certainly not to"persons in good health. The actual amount of solid matter contained in the organisms is much smaller than might be supposed. For example, it has been calculated that the weight of one Asterionella is .0000000004 gram. A growth of 100,000 Asterionella per c.c. would render a water unfit to drink because of its odor, yet a tiunblerful of such water would contain but eight milligrams of solid matter, and only ene-half of this would be organic matter. It is almost incdn- ceivable that such a small amount of organic matter could cause trouble unless some poisonous principle were present, and so far as is known no such substance has been found. The alleged cases of poisonous alga^ rest upon too uncertain evidence to be received as facts.
Nevertheless there is some reason to believe that people accus- tomed to drinking water free from organisms may be subjected to temporary intestinal disorders when they begin to drink water rich in microscopic organisms — just as people are affected by changing from a hard to a soft water and vice versa. It is possible that with young children and invalids such disorders may be more common than has been supposed. Decomposition of the organisms by bacteral action may possibly contribute to intestinal disorders.
Yet, whether harmful or not the presence of large nmnbers of organisms in a public water-supply is most objectionable.
Value of Pure Water.— In his little book entitled " The Value of Pure Water '' the author has attempted to express in terms of money the value to a community of a supply of clean water over a water that is unattractive by reason of color, turbidity and the presence of alga^. The following paragraphs are taken from this work.
ODORS IN WATER-SUPPLIES 201
Attractiveness. — ^The analytical determinations which relate to the general attractiveness of a water are those of taste, odor, color, turbidity, and sediment. As these quantities increase in amount, the water becomes less attractive for drinking purposes, until finally a point is reached where people refuse to drink it. In order to use these results in a practical way, it is necessary to combine them so as to obtain a single value for the physical characteristics or, as they say abroad, for the " organoleptic " quality of the water. An attempt has been made by the author to obtain what may be termed an aesthetic rating of the water, and the result is shown in the diagram on page 202.
This diagram, it should be said, is based almost entirely upon estimates and very little upon statistical data. It rests upon the assumption that people differ in their sensibilities or their aesthetic feelings as to the use of water. Some persons are much more fastidious than others in regard to what they drink. A water which would be shunned by one person, even though he were thirsty, might be taken by another with apparent relish. As a rule, people are more fastidious about the odor of water and the amount of coarse sediment which it contains than they are about its color and turbidity. This is perhaps natural, as a bad odor suggests decay, and decay is instinctively repug- nant. Often, however, people do not discriminate between odors which are due to decomposition and those which are not. Habit and association have much to do with a person^s views as to the attractiveness of water. In New England, where the clear trout brooks run with what Thoreau called ** meadow tea,'' few people object to a moderate amount of color, while they do object to a water which is very turbid. In the Middle West, where all the streams are muddy, it is the unknown colored waters which are disliked. People who are accustomed to well- water object to both color and turbidity. With most people a fine turbidity, such as is produced by minute clay particles, is less a subject of complaint than an equal turbidity produced by comparatively coarse sediment. In the diagram an attempt has been made to reconcile these different points of view, so as to put them, as well as may be, on the same footing. In this connection several series of comparisons were made.* Turbid waters were viewed by a group of Western people, who made some comparisons with colored and turbid waters, while colored waters were viewed by a group of students in New York, and vice versa.
* Acknowledgments are due to Mr. J. VV. EUms, of Cincinnati, Ohio, and Mr. Andrew Mayer, Jr., of Brooklyn, N. Y.
THE MICROSCOPY OF DRINKINQ WATER
The abscissae of the diagram represent turbidity, color, and odor, as given in the ordinary water-analy^. llie ordi-
nates represent the " per cent of objecting consumers." By this is meant the proportion of the water-takers who would ordinarily choose not to drink the water because of the quality
ODORS IN WATER-SUPPLIES 203
indicated by the curve, or who would buy spring water, or bottled water, rather than use the public supply, if they could afford to do so. This number would increase, of course, as the general attractiveness of the water decreased. From the curves one may calculate what may be called the (Esthetic deficiency of the water by adding together the per cents of objecting con- sumers for color, turbidity, and odor. If the aesthetic deficiency equals loo, it indicates that the water is of such a character that every one would object to it, and figures in excess of loo only emphasize its objectionable character.
It will be seen from the diagram that when the color of water is less than 20, or the turbidity less than 5, only one person in ten would object to it, but when the turbidity or color is 100, one-half of the people would object to it. It may be thought that this proportion is too low, but it must be remem- bered that colored waters are invariably accompanied by a vegetable odor and often by a slight turbidity, and that it is the sum of the several quantities which determines the aesthetic rating.
Experience has shown that objection to color varies directly with its amount; consequently this curve has been plotted
from the equation, pe= -, i.e., a straight line, where pe stands
for the per cent of objecting consumers, and c for the color.
In the case of turbidity, however, small amounts count for more, relatively, than larger amounts. The equation for
the turbidity curve has been taken, therefore, as pt = S\/ty where / stands for the turbidity.
With odor, however, the opposite condition prevails: faint odors count for little, but distinct and decided odors cause much more complaint. Consequently, the per cent of objecting consumers has been made to vary as the square of the intensity of the odor expressed according to the standard numerical scale. The quality of the odor makes quite as much difference as its intensity, and for that reason three curves have been plotted, one representing vegetable or pondy odors (Or), one repre- senting odors due to decomposition (Od) , and one representing the aromatic, grassy and fishy odors due to microscopic organisms (Oo). These curves are plotted from the following equations:
pQ = 2O?,
pQ=ysO^, P^ = sOq^
in which Oo, Od, and 0. stand for the intensity of the three groups of odors mentioned.
204 THE MICROSCOPY OF DRINKING WATER
These curves represent somewhat imperfectly our present ideas as to the relative effects of color, turbidity, and odor; and on further study they are likely to be considerably modified.
It is a well-known fact that in cities which are supplied with water which is not attractive for drinking purposes, large quantities of spring "water and distilled water are sold, and that consumers go to much expense in the purchase of house-filters in order to improve the quality of the water furnished by the city mains. It is fair to' assume that in any community the amount of money expended for bottled water and house-filters will vary in a general way, according to the attractiveness of the water, although there is no doubt that the presence of typhoid fever in the community, or the fear that the water is contam- inated, will greatly increase the use of auxiliary supplies for drinking. For purposes of calculation it may be assumed that the diagram just described represents this tendency to use vended waters, and that each ** objecting consumer " would go to the expense of buying spring water or putting in a house- filter, if he could afford it. It may be argued, also, that the poor consumer who may be unable to do this is as much entitled to satisfactory water as is the well-to-do consumer.
From a study of price-lists of spring waters sold in New York and other cities, it has been found that the ordinary wholesale price of spring water is seldom more than lo cents a gallon. In some places it is as low as i cent. The average is about 5 cents. To filter water through house-filters costs less, but generally it is less satisfactory.
As a convenient figure for calculation, and as a most con- servative one for general use, a cost of i cent per gallon to the ordinary consumer for an auxiliary supply of drinking water (either spring water or well-filtered water) has been taken. In cities where the cost of procuring and distributing bottled water exceeds i cent per gallon, as it does in such a city as New York for example, this should be taken into account in making local use of the data. For the illustrative purposes of the present study, and for general comparisons, the figure mentioned will serve as a satisfactory basis. The average person drinks about 1.5 quarts of liquid per day, of which one-half may be assumed to be water, the rest being tea, coffee, etc. Therefore one-fifth cent per capita daily may be taken as a reasonable figure for the cost of an auxiliary su])ply. If the entire population used such a supply, and if the daily consumption of the public water- supply were 100 gallons per capita, then one-fifth cent per hundred gallons, or $20 per million gallons, would represent the loss to the consumers due to an imperfect water-supply which
ODOKS IN WATEIC-SUPPLIES
205
had an aesthetic deficiency of loo. If the aesthetic deficiency were less than loo, say 37, then the loss to the consumer would be ^ of $20, or $7.40 per million gallons. In other words, the figure for the aesthetic deficiency divided by 5 gives the financial depreda- tion of the water-supply in dollars per million gallons, or
D=20
Pe + pt + pO
100
Example: Suppose the turbidity of a water is 3, its color 65, and its odor 2/ (that is, faintly fishy), because of the presence of microscopic organisms; then
12+32 + 20 . „ ^ - = $12.80;
D=20
100
that is, the depreciation of the water, because of its unsatis- factory physical qualities, amounts to $12.80 per million gallons.
DEPRECIATION DUE TO ODOR Values of D for different values of Ov, Oct, and Oo in the formula
2o(20,«-h3.50rf»+sOo«
Z?=
100
Dollars per million gallons.
|
Odor. |
Vegetable Odor iOV). |
|
|
0 |
None Very faint Faint Distinct Dec? Jed Stronp |
0.0 |
|
I |
0.4 1.6 |
|
|
2 |
||
|
a |
3.6 6.4 10. 0 |
|
|
A |
||
|
s |
Odor of Decomposition.
Odor Due to
Organisms
(Oo).
0.0 i.o 4.0 9.0 16.0 25.0
Algae as Local Nuisances. — Thus far in this chapter the algae have been considered from the stanpdoint of the odor imparted to water used for drinking. The odors are sometimes strong enough to be noticed in the vicinity of the reservoirs, in fact in some cases, the odors have been wafted by the wind for distances of a quarter of a mile. The decay of littoral growths of filamentous algae sometimes cause objectionable odors along the shore. The odors derived from the exposed bottoms of reservoirs, when the water has been drawn down, are familiar to all, but it is not generally considered that such odors are due largely to algae. The " odor of the sea " that is so much loved, is similarly due largely to sea-weed.
Algae are sometimes driven inshore by the wind and stranded on beaches, where they decay and produce foul conditions.
CHAPTER XIII STORAGE OF SURFACE-WATER
To obtain a permanently safe and satisfactory surface-water supply without filtration the rainfall must be collected quickly from a clean watershed and stored in a clean reservoir,
A dean watershed may be defined as one upon which there are no sources of pollution and no accumulations of decompos- ing organic matter. The subject of pollution is of paramoimt importance, but it will not be emphasized here as its discus- sion leads into bacteriology rather than into microscopy. No watershed can be wholly free from organic matter, and this must eventually decompose. The grass dies, the leaves fall, and a thin layer of decay is spread over the surface of the ground. This is repeated year by . year. Normally this organic matter disappears by rapid oxidation, and if the ground is sloping the rain that falls upon it runs off rapidly and absorbs comparatively little organic matter. If, however, the decay- ing vegetation has accumulated in thick layers, if the ground is level and becomes saturated or covered with water, decom- position takes place under different conditions, and the water may become highly charged with organic matter and the prod- ucts of decay.
Effect of Swamp Land. — The effect of swamp areas upon the color of water has been referred to. Water from a clean watershed seldom has a color higher than 30 of the Platinum Scale. The amount of color above this figure can be generally traced to swampy land. The color of the stagnant water of swamps is sometimes very high — often 300 and sometimes as high as 500 or 700 on the Platinum Scale. From this it is easy to see that even a comparatively small percentage of swamp-
206
STORAGE OF SURFACE-WATER 207
land upon a watershed may have an important eflfect upon the* color of the combined yield.
A highly colored water means a water rich in organic matter. If the color is much above 50 the water has an unsightly appearance, a distinct vegetable odor, and a sweetish and some- what astringent taste. But the presence of organic matter is objectionable for another reason. It helps to furnish food- material for the microscopic organisms, and these may render the water very disagreeable. Swamps are breeding-places for many of the organisms that cause trouble in water-supplies, and numerous instances might be cited where organisms have developed in a swamp and have been washed down into a storage reservoir, rendering the water there almost unfit for use.
Cedar Swamp, at the head of the Sudbury River of the Boston water-supply, furnishes an example of this. During August, 1892, Anabaena developed abundantly in a small pond in the middle of this swamp. At one time there were 8400 filaments (about 50,000 standard units) per c.c. A heavy rain washed the Anabaena down-stream, and on August 15 there were 2064 filaments per c.c. at the upper end of Sud- bury Reservoir No. 2, which is long and narrow. On August 17 the water entering the basin contained but 600 filaments, and a week later it contained none. The Anabxna were washed down-stream in a sort of wave, which passed through the basin, down the aqueduct, through the Chestnut Hill reservoir, and into the service-pipes. On August 22 Anabaena were first observed at the gate-house at the lower end of Reservoir No. 2, where there were 647 filaments per c.c, and on the following day they appeared at the terminal chamber of the conduit at Chestnut Hill reservoir, where there were 326 filaments per c.c. In another week they became disseminated through this reservoir and were found in the service-pipes. As the water from Reservoir No. 2 passed toward the city it became mixed with the water from other sources, so that by the time it reached the consumers the Anabaena were not sufficiently abun- dant to cause complaint. After the first wave of Anabaena had passed through Reservoir No. 2 the organisms began to increase
208 THE MICROSCOPY OP DRINKING WATER
throughout the basin, and the growth continued for several weeks. It was evident that the water from the swamp carried down not only the Anabaena themselves, but enough food- material to support their growth in the basin.
Instances are still more common where organisms ftom swamps have seeded storage-reservoirs. Entering the reser- voir in comparatively small numbers, the organisms frequently find in the quiet water conditions favorable to their growth. Growths of some of the Flagellata may be traced directiy to seeding from swamps. The draining of swamps makes a vast improvement in the quality of the water delivered from a watershed. In general it should be carried out in such a way that the water falling upon the clean portions of the water- shed is not obliged to pass through the swamp before entering the reservoir. This may be accomplished by a system of marginal drains or canals. The lowering of the water-table of a swamp also improves the quality of the water delivered from it.
Small mill-ponds and other imperfectly cleaned ponds or pools are also frequent breeding-places of microscopic organ- isms. Again the Boston water-supply furnishes an example. A short distance above Sudbury reservoir No. 3 there were at one time several mill-ponds. These ponds were favorite habitats of Synura. These organisms were often found there in large numbers, and when the water was let down-stream through the mills or when heavy rains caused the ponds to over- flow, the Synura would become numerous in the reservoir.
Effect of Pockets. — Thus it is seen that in order to avoid the growth of troublesome organisms the water should be delivered from a water-shed quickly, and should not be allowed to stand in shallow ponds or pools in contact with organic mat- ter. As far as possible a watershed should be self-draining. It may be added that the storage reservoir also should be self- draining. It often happens, when the bottom of a reservoir is uneven, that water is left in small pools as the reservoir is drawn down. These pools are usually shallow and the water becomes warm and stagnant. They often become filled with rich cultures of organisms, and when they overflow the organ-
STORAGE OF SURFACE- WATER 209
isms are scattered through the reservoir. Such pools or pockets should be provided with an outlet. If this is impossible it may be advisable to fill them up. The author once observed a pocket in a reservoir that was excavated to a considerable depth for the sake of removing all the organic matter at the bottom. This pocket could not be drained, and during the simmier it became the breeding-place of Synura and other organisms. It would have been better to have removed a portion of the organic matter and to have covered the remainder with clean material.
It has been stated that water should not be allowed to stand for any length of time in contact with organic matter. It is quite as bad for water to stand over a swamp as it is for it to stand in a swamp. It may be worse, for if the water has sufficient depth the decomposition of the organic matter at the bottom may take place in the absence of oxygen, and under these conditions some of the resulting products are more easily taken up by the water. This brings us to the consideration of the so-called " stagnation effects.*'
Effects of Stagnation in Reservoirs. — By this term is meant a continued state of quiescence of the lower layers of water in a lake or reservoir caused by thermal stratification, as described in Chapter VII. During these periods of quiescence the water below the transition zone, i.e., the stagnant water, undergoes certain changes, the character and amount of these changes varying with the nature of the water and especially with the presence or absence of organic matter at the bottom of the reservoir. Stagnation may be studied best in ponds where there is a considerable deposit of organic matter at the bottom, and of such ponds Lake Cochituate is an excellent example.
Near the efflux gate-house the lake has a depth of 60 ft. At the bottom there is a layer of organic matter of unknown thickness. The upper portion of this is due to deposition of organisms and other organic material transported by the water. The period of summer stagnation extends from April to No- vember, and during this time the deposit of organic matter at the bottom is accumulating.
THE MICROSCOPY OF DRINKING WATER
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STORAGE OF SURFACE-WATER
211
The changes that take place in the water at the bottom of Lake Cochituate during the summer are shown in the fol- lowing table, where the analyses of the water at the surface and bottom are compared. The most conspicuous change is that of the color (see Fig. 60). While the water at the surface is bleaching under the action of the sunlight, that at the bottom grows rapidly darker imUl, near the close of the stagnation
w ^^__ V i m
J. .^^j^ J_
Fig. 60.— Stagnation Effects, Lake Cochituate.
period, it* has a decided opalescent turbidity and a rich brown color. A peculiarity of the water is that its color deepens rapidly after being drawn to the surface These color phenomena are due to the presence of iron in the water. By sedimentation of iron in combination with organic matter and of ferric hydrate produced by oxidation in the upper layers, a considerable deposit of iron has been formed at the bottom. As the oxygen dissolved in the water at the bottom disappears during the summer, the ferric iron gives up its oxygen to the organic matter
212 THE MICROSCOPY OF DRINKING WATER
and bee mes reduced to the ferrous state. In this state it is soluble. As stagnation continues it becomes dissolved in increasing amounts. When carried to the surface it becomes oxidized to the insoluble ferric state, deepening the color of the water for a time, but later precipitating as a brown sediment and leaving the water with little color. Important changes in the organic matter in the lower layers take place during the stagnation periods. The amount of organic matter in the water increases by sedimentation from above and by solution from the ooze at the bottom. The albuminoid ammonia increases. Decomposition of the organic matter takes place. The dis- solved oxygen disappears and the nitrates and iron become reduced. The free ammonia and nitrites increase, and the free carbonic acid increases greatly. After the supply of oxygen has become exhausted, putrefaction through the agency of the anaerobic bacteria takes place and the water acquires ofiFensive odors. Increasing amounts of mineral matter are taken up from the bottom by the lower layers of water. This is true not only of iron, but also of silica, manganese, and some of the calcium and magnesium salts. The bacteria below the transition zone increase and forms resembling B. coli sometimes multiply.
These stagnation effects are observed only below the transition zone. The relative changes that occur at different depths are well shown by the amount of dissolved oxygen, and the progress of the changes through the season may be studied by a series of such observations. Elaborate studies upon this subject have been made at Jamaica Pond by the Massachusetts State Board of Health for the details of which the reader is referred to the Special Report of 1890 on Examina- tion of Water sui)plies, and to the Annual Reports for 1891 and 1892. The following tables serve to illustrate these phenomena.
The effect of stagnation upon the microscopic organisms has been referred to. In deep reservoirs relatively little life exists below the transition zone. The ooze at the bottom is largely an accumulation of dead organisms. The few living organisms that are found there are Bacteria, Fungi, Protozoa and Crustacea,
STORAGE OF SURFACE-WATER
213
organisms that are parasitic or that play the part of scavengers. The water at the bottom, however, acquires a supply of food- material — both organic and mineral — suitable for microscopic life. After stagnation ceases and the period of circulation begins, this food-material is carried to the upper regions where, with light and oxygen, the plankton are able to utilize it. The diatoms in particular depend upon the food-supply acquired by the water during periods of stagnation.
DISSOLVED OXYGEN AT VARIOUS DEPTHS IN LAKE COCHITUATE, IN PER CENT OF SATURATION.
Surface 79
10 ft. 20'*
{<
it
30 40
4S so"
S6"
S7i"
|
16, 1891. |
Sept. |
28. 189X. |
|
79 |
90 |
|
|
84 |
81 |
|
|
36 |
33 |
|
|
21 |
9 |
|
|
20 |
8 |
|
|
2 |
— |
|
|
0 |
0 0 |
FREE CARBONIC ACID AT VARIOUS DEPTHS IN LAKE COCHITUATE.
(Parts per million.)
|
Depth. |
May 24, 190 1. |
Oct. 11. 1901. |
Nov. 14, 1991. |
|
Surface |
I-S |
4.0 |
6.0 |
|
10 |
2.0 |
30 |
6.0 |
|
20 |
6.8 |
10.0 |
6.0 |
|
30 |
6.0 |
II .0 |
6.0 |
|
40 |
10. 0 |
II. 0 |
6.0 |
|
SO 60 |
8.0 8.0 |
19.0 23.0 |
6.0 6.0 [52 ft.) |
The stagnation of a pond that has deposits of organic matter at the bottom affects the quality of the water in two ways When the bad water at the bottom is carried to the surface during the periods of circulation the entire body of water is affected by it. The color increases, the organic mat- ter increases, and the odor may become unpleasant. These are the direct effects. Odors of the water that are caused by the growth of organisms that have been stimulated by the acquired food-materials are the indirect effects.
214 THE MICROSCOPY OF DRINKING WATER
Effect of Organic Matter on Reservoir Bottoms. — ^The dis- agreeable effects of stagnation are not dependent upon the depth of a pond, except in so far as the depth affects thermal stratifica- tion. They depend somewhat upon the character of the water stored, but much more upon the amount and character of the organic matter at the bottom and upon the length of the stagna- tion periods. If the bottom of the reservoir contains no organic matter the phenomena described above will not occur. It has been found that in the Wachusett reservoir of the Boston water-supply, where the organic matter was carefully removed from the bottom, the dissolved oxygen at the bottom does not become exhausted during the stagnation periods, although it is appreciably reduced in amount.
The author once collected a sample from Lake Champlain at a depth of nearly 400 ft. The temperature was 39.2® — i.e., maximum density — and the water was probably in a state of permanent stagnation. The sample was bright, clear, colorless, and without odor. The material on the bottom was found to be ahiiost perfectly clean gravel.
Organic matter at the bottom of shallow reservoirs will cause a deterioration of the water stored in them. K there is no summer stagnation the water at the bottom becomes warm, and decomposition goes on rapidly. The products of decay taken up by the water support the growth of organ- isms i)arlicularly the blue-green algaj. Moreover, during the winter when the surface is frozen these shallow ponds grow stagnant and the conditions become similar to those in (lee[) ponds. After the periods of winter stagnation, shallow ponds often contain heavy growths of diatoms. Organic mat- ter at llie bottom of a shallow reservoir affects the quality of the water in another way. It offers support for fixed aquatic plants, and these may injure the quality of a water directly by their decay or indirectly by harboring microscopic organisms.
Stagnation in Reservoirs at Panama.— Mr. John R. Downes, Physiologist to the Isthmian Canal Commission, has described the stagnation of the reservoirs of the water supplies at Panama. This occurs even though the reservoirs are relatively shallow
STORAGE OF SURFACE-WATER • 216
and the temperature of the water high. For example, in the Cocoli reservou-, 9 feet deep, the temperature on one occasion was 83® at the surface and 80° at the bottpm, yet the dissolved oxygen varied as follows: Surface, 8.6; 5 feet, 6.2; 7 feet, 0.8; 9 feet, 0.0 parts per million. In Carabali reservoir, 12 feet deep, there was no dissolved oxygen below 8 feet. In Comache reservoir, 26 feet deep, there was none below 14 feet. At certain seasons of the year there are periods of overturn as elsewhere. This stagnation of the bottom water has been the cause of some bad tastes and odors in the water supplies. Algae occur in these waters but apparently do not cause as much trouble as one might think.
Sanitary Effect of Algae Growths. — While the growth of algae and other microscopiG organisms in surface-waters is often troublesome, yet at times they tend to improve the sanitary quality of the water. The following instances, taken from the records of Mt. Prospect Laboratory, illustrate this:
Baiseley's Pond, one of the sources of water-supply of Brooklyn, is fed by a number of streams which are more or less polluted. During August, 1899, the water of the pond con- tained a large amount of Clathrocystis. Bacteriological examina- tions of the inflowing streams showed that the water contained from 1000 to 17,000 bacteria per c.c. while the water at the lower end of the pond contained less than 50 per c.c. A study of the analytical records for the same pond during the years 1898-9 showed that the number of bacteria varied inversely with the number of Clathrocystis. (See Fig. 61.)
Laboratory experiments made by Strohmeyer and others corroborate the above and show that certain algx tend to reduce the number of bacteria in water. More recent experiments by Emmerich have indicated that certain Protozoa exercise a similar purifying effect on surface-waters. He has found that two species of the genus Bodo will very greatly reduce the number of typhoid-fever germs in water. Staining of the organ- isms shows that the bacteria are absorbed by the animal-cell, the action being analogous to that of the white-blood corpuscles in the human body upon which Metchnikoff 's theory of phago-
216
THE MICROSCOPY OF DRINKING WATER
cytosis was based. Emmerich considers that these and othe*- Protozoa play an important part in the self-purification of streams.
Experiments by Mr. C. P. Hoover, at the Columbus, Ohio, water filtration plant have shown that the removal of the free
1898
tmmu
1899
Fig. 6i. — Diagram Showing the Number of Standard Units of Clathrocystis and the Number of Bacteria per cubic centimeter in the Water of Baiseley*s Pond, Brooklyn Water Supply.
carbonic acid and the half-bound carbonic acid from water will destroy any typhoid bacilli that may be present in the course of a few hours. Inasmuch as the algae are able to thus render the water alkaline to phenolphthalein, as already men- tioned, wc have hero a possible explanation cf the great reduc- tion of bacteria by algte that sometimes occurs in reservoirs.
STORAGE OF SURFACE-WATER
217
Strohmeyer's Experiments. — Strohmeyer, at Hamburg, made some interesting laboratory experiments showing how growing Enteromorpha influenced the number of bacteria in the water placed in direct sun-light and in diffused light. Thus in diffused light he obtained the following results:
|
Date. |
Time. |
Number of Bacteria per c.c. |
|
|
Enteromorpha Present. |
Enteromorpha Absent. |
||
|
July 4 4 4 5 5 5 6 6 |
11.30 A.M. 2.00 P.M. 6.00 P.M. 8.30 A.M. 2.00 P.M. 6.30 P.M. 9.00 A.M. 7.30 P.M. |
145 160 152 IIOO 180 7 24 0 |
108 144 243 5900 26000 50000 63«x> 80000 |
CHAPTER XIV
SOIL STRIPPING
In 1907 Messrs. Allen Hazen and George W. Fuller made a study of the advisability of stripping the soil from the sites of thcAshokan and Kensico reservoirs about to be constructed by the Board of Water Supply of the City of New York, Mr. J. Waldo Smith, Chief Engineer. In the course^ of this study a large amount of valuable information was accumulated, the general results of which were published in the annual report of the Board of Water Supply for 1907. Because of the importance of this report and the very thorough manner in which it was compiled the following quotations are taken from the report in cxicnso. They constitute this entire chapter. The author justifies this long quotation on the ground that he him- self had a part in the preparation of the report.
History of Reservoir Stripping. — The stripping or remov- ing of soil from the bottom and sides of reservoirs so as to eliminate at the outset practically all organic matter is a Massa- chusetts custom. For the most part the practice has been con- fined to that State. In fact, so far as we can ascertain, there is scarcely an impounding reservoir outside of New England which has been thoroughly stripped.
In Europe, impounding reservoirs have not often been stripped; sometimes they have not even been grubbed. We have been able to learn of only three impounding reservoirs there which have been stripped. These are small and have been built on i)eaty areas. Stripping was undertaken appar- ently for the reason that at lower points on the same streams older reservoirs were found to have given trouble for a time in earlier years. One of these stripped reservoirs is near Brad- ford, England.
In India there are quite a number of large impoimding
218
SOIL STRIPPING 219
reservoirs, but so far as we can ascertain, none of them has been stripped. The same is true of several projects in Australia of which we have record.
About twenty-five years ago, particularly during the unusually dry seasons of 1881-82, seriously objectionable tastes were experienced in the water from some of the reservoirs supply- ing Boston. At that time the more recently constructed storage reservoirs of Boston had had the trees and brush grow- ing on the bottom and sides cut down and removed or burned. Shallow flowage had also been eliminated somewhat, but, generally speaking, there was no radical departure in Massa- chusetts from the practice elsewhere, although there was a well-d6fined tendency to make flooded areas cleaner.
Beginning about 1883 ^^ cleaning of the bottoms and sides of the reservoirs then imder construction was imdertaken systematically. Thus Reservoir No. 4 of the Boston water- works, now known as the Ashland reservoir, built in 1882-85, was thoroughly cleaned of all loams, stumps and vegetable matter, and was deepened wherever the original depth below high water was less than 8 ft. The Hopkinton reservoir, built a little later, was similarly prepared, and the same has been true of all large reservoirs since built for the Boston supply. Two of the older reservoirs, namely, Framingham reservoirs Nos. 2 and 3, of the Boston water- works, were also improved about this time by removing all stumps and much of the muck from the sides and bottom as far as they could be exposed by drawing down the water, and by increasing the depths at points of shallow flowage. There were also a few comparatively small reservoirs elsewhere in Massachusetts which were prepared with clean bottoms and sides during this period.
Early Discussions of Stripping. — Various reports and records show that twenty years ago and more, distinctly unpleasant conditions in the quality of public water-supplies, especially as regards tastes and odors, were experienced in quite a large number of American cities outside of Massachusetts. Of particular interest is the report made in 1859 to the Croton Aqueduct Board by the late Dr. John Torry. (Transactions American Society of Civil Engineers, Vol. XXI, 1889, p. 555.) A good account of the experiences in early years may be found in the following reports and papers:
I. Prof. Wm. Ripley Nichols, a report upon the cause of algae growths in water with reference to filtration, in the 1878 Report of the Massachusetts State Board of Health, p. 158.
220 THE MICROSCOPY OF DRINKING WATER
2. Mr. Alphonse Fteley's report upon the algae observed in the Boston water-supply in 1879, ^ ^^ Massachusetts State Board of Health Report, 1879, p. 123.
3. Prof. W. G. Fowler's report upon vegetable growths in drinking water, in the 1879 I^eport of the Massachusetts State Board of Health.
4. Prof. Wm. Ripley Nichols* paper on tastes and odors of surface waters before the Boston Society of Civil Engineers, Journal of the Association of Engineering Societies, Vol. I, 1882, p. 97.
5. Mr. Geo. W. Rafter's paper before the American Society of Civil Engineers on fresh-water algae and their relation to the purity of public water-supplies, Transactions of the American Society of Civil Engineers, Vol. XXI, 1889, p. 483.
A number of the writings of the late Messrs. Fteley and Nichols are of much historical significance. Each of these gentlemen had unusual opportunities for making personal studies of important cases. Mr. Fteley was resident engineer for many years of the Boston reservoirs and later became chief engineer to the Croton Aqueduct Commission of New York City. In discussing Mr. Rafter's paper in 1889 (see above reference), Mr. Fteley stated, on p. 518, in connection with the large new Croton reservoir, which was then being planned.
" As to the advisability of removing the loam and all perish- able matters from its area before construction it is clearly out of the range of practicability.
** It is certainly better, when within practical limits, to remove the loam from the surface of reservoir grounds near the water mark, although experience shows that inside of a very few years after flowagc nature produces that result within the limits of fluctuation,, except on flat grounds; but a general removal of the top-soil is not to be advised."
Prof. Wm. Ripley Nichols was a careful observer of these matters, particularly as they related to the reservoirs for the Boston supply. An excellent summary of his various writings and reports is to be found in his book on " Water Supply," published in 1883. His descriptions of the history of organic matter on the bottoms and sides of reservoirs are so clear that several paragraphs, pp. 84-89 of his book are quoted at length.
*^ A word or two may be in place with reference to the action of fresh water upon vegetable matter in its bearing upon impounding reservoirs. When vegetable matter decays in moist soil, it is converted into a brown or black substance
SOIL STRIPPING 221
generally known as ' humus;' this is really a mixture of a num- ber of different bodies, and from it chemists have isolated a variety of substances, such as humic acid and humin, ulmic acid and ulmin.* The acids of the humus, by oxidation, undergo chemical change, to be sure, being converted into crenic and ap)ocrenic acids which, or rather the salts of which, are found in surface-waters; but when the vegetable matter is thoroughly ' humified,' as in the case of peat, it exerts apparently no bad eflfect on the water, except by giving it a brown color and a somewhat earthy taste.
" When a recently felled tree is exposed to the action of the water, or when bushes or even grass and weeds are killed by being flooded with water, the sap and more soluble matters are bleached out and putrefy, or, in the presence of much air, undergo other forms of decomposition. This action will take place, no matter under what depth of water the vegetable matter may be placed, but the effect will be less marked as the amount and motion of the water is greater.
" After the more soluble portions are extracted, the sub- sequent decay proceeds with extreme slowness, provided the remaining cellulose or woody fiber is kept continually covered with water, but alternate exposure to the air and water soon causes decay, as every one knows. In a natural or artificial reservoir the inevitable variations of level are very disadvan- tageous. As the level is lowered those aquatic plants which grow in shallow water die, and if the water rises after only a short interval it becomes impregnated with the products of their decay; if a considerable interval elapses, land plants grow upon the exposed surface, and being drowned by the rising waters, tend to its contamination in the same manner.
" It appears from this, that in the construction of impound- ing reservoirs, the mass of growing plants, as well as the soil in which they have their roots, and which of itself contains more or less soluble organic matter, should be removed as thoroughly as possible, especially if the water is to be of no great depth above it when the reservoir is flooded. If the reservoir is filled without such removal of the organic accumula- tions, a long time may be required before the chemical changes have combined themselves and the water becomes well suited for use, but tlie complete removal of the soil, as far as such removal
* For a r6suin6 of the investigations on the composition of humus, see Julien, Proceedings American Association, XXVIII, 1879, p. 313 and following.
222 THE MICROSCOPY OF DRINKING WATER
is practicable, is not a guaranty that no trouble will arise from a newly filled reservoir. Occasionally the vegetable decay in a new reservoir gives rise to much oflFense from the formation of sulphureted hydrogen. A marked instance of this ocoirred in one of the basins of the Sudbury River supply, Boston, Mass., the sunmier after it was first filled. The whole mass of water in the basin was permeated with the odor, which was so strong on the leeward side of the pond as to incommode the passers-by. The odor was not that of pure sulphureted hydrogen as pre- pared in the laboratory, and the gas was no doubt accompanied by other chemical products. The water drawn from the depths of the pond had the odor of an antiquated privy. The presence of sulphureted hydrogen was made very manifest by sus- pending in the gate-house cloths wet with a solution of acetate of lead; these became yellowish-red, and finally jet black, owing to the formation of sulphide of lead.
** The formation of the sulphureted hydrogen is readily explained. The flooding of the basin started the decay of a large quantity of organic matter; this taking place in the presence of the sulphates contained in the water changed them into sulphides, and from these sulphides thus formed sulphureted hydrogen is liberated by the acid products of decay. This same change takes place to a less degree in almost all ponds and reservoirs. The gas is formed, however, mainly at the bottom, and as it difTuscs upward and mixes with the overly- ing water it comes into contact with the oxygen in the water and is decomposed. The sulphur is set free and sinks to the bottom, or in a very finely divided state flows oflF with the water. . . .
*' These alga?, when present in any considerable quantity, give a repulsive appearance to the water, and when they are in a state of decay they communicate to it an offensive taste and odor. Fortunately, in most cases, the trouble which they cause is of short duration, although often recurring in the same water-supply year after year. Their presence is not a sign of contamination, as they occur in natural ponds removed from all polluting influences. WhilCy however, they do grow in pure waters and in old and clean ponds, they seem to grow more abun- dantly in water containing mud and vegetable extractive matter, as in newly filled rcserooirs; so that, while immunity from their presence cannot be guaranteed in the case of any pond, tfiey may with some certainly be looked for in dirty and especially shallow ponds, A warm temperature and shallow water are perhaps of even more importance than the products of decay of higher
SOIL STRIPPING 223
plants, far all surface-waters contain tite amnumiacal and mineral salts necessary for the growth of tIte algce.
^^ As far as our present knowledge extends , there is nothing that can be done to exterminate the algcF from ponds in which they occur. . . ."
Discussion of Stripping by Dr. Drown. — Between 1890 and 1895 Mr. Frederick P. Steams, and Dr. T. M. Drown, the Chief Engineer and Chemist, respectively, of the Massachusetts State Board of Health, carried on important researches on soil stripping, based on extensive analyses and surveys of local water-supplies. Their studies were simimarized by Dr. Drown as follows:
1. Waters containing organic matter in the presence of oxygen are decomposed by bacterial action and in this oxida- tion the carbon and the hydrogen of the organic matter take precedence over the nitrogen. Objectionable tastes and odors seldom result from this decomposition of organic matter in the presence of oxygen. The measure of this change in organic matter was taken as being indicated by the free ammonia.
2. Where oxygen becomes exhausted the organic matter in water is subjected to the activity of other kinds of bacteria. Such waters are spoken of as " stagnant " and the bacterial process which stagnant waters undergo is spoken of as ** putre- faction." Resulting from the putrefaction of organic matters, stagnant waters possess offensive odors, due largely to sul- phureted, carbureted and phosphoreted hydrogen.
3. The stagnation of water is stated not to be objectionable in itself, and a practical suggestion of much merit is made with regard to the correction of the offensive odors from stagnation by means of aeration.
4. The several reports made it plain by inference that the objectionable tastes and odors of stagnant waters are due to gases of decomposition and not to growths of organisms. In fact, recent evidence makes it appear that the fungi arc only organisms capable of growing prolifically in stagnant water and they do not directly cause objectionable tastes and odors.
5. Stagnant waters are improved by aeration partly by the mechanical removal of objectionable gases and partly by the oxidation of dissolved compounds, especially salts of iron.
6. The opinion was restated that the character of the bottom of reservoirs affects stagnation and putrefaction of the water therein contained more than does the dissolved and suspended organic matter in the water itself.
7. Cases were noted where reservoirs contained stagnant
224 THE MICROSCOPY OF DRINKING WATER
and offensive bottom layers in which the amount of organic matter was less than in the top water when the latter contained both oxygen and organic growths producing seriously dis- agreeable odors.
8. It was recognized that one of the beneficial effects of aeration in stopping excessive growths of algae was contributed by the agitation of the water.
As a result of these investigations and of others made under the direction of Desmond FitzGerald Superintendent of the Boston Water Works, the following conclusions were reached in 189s in regard to the stripping of the Wachusett res- ervoir.
" As a preliminary conclusion, based on the facts determined in this investigation, it may be said that the effect of the organic matter in these various soils on the water in contact with them is simply a question of its amount, and that its origin and composition seem to be without marked influence. The watershed from which the samples were taken is very sparsely populated, and the organic matter in all cases is mainly of vegetable origin."
** It is probable, therefore, that we need only concern our- selves with the amount of organic matter in a soil of this character in determining the necessity of its removal, and as a provisional standard wc may perhaps fix 1.5 to 2 per cent of organic matter, as determined by the loss on ignition of the sample dried at 100° C, as the permissible limit of organic matter that may be allowed to remain on the bottom and sides of a reservoir.''
Results of Stripping in Massachusetts. — In the 1904 Report of the Massachusetts State Board of Health, p. 144, is given a record of the results of extended observations made by the Board upon surface-waters throughout the State. In this table the waters are divided into five groups, the first group being of waters having the least odor, and the fifth group of waters containing the most offensive and objectionable odors.
There are 64 reservoirs in this list. Many of these are very small, and for that reason are not comparable with large reservoirs. For the puq^ose of this discussion we have excluded all reservoirs less than 100 acres in area. This leaves only 17 reservoirs, 11 of which were more or less completely stripped. These II are practically the only reservoirs of considerable size in the United States which have been stripped.
The essential facts as to stripping have been supplied by Mr. X. H. Goodnough, Chief Engineer of the Board. These
SOIL STRIPPING
225
data for the large reservoirs of the State are classified accordin to stripping as follows :
STRIPPED RESERVOIRS IN MASSACHUSETTS OVER 100 ACRES IN
AREA.
|
Place. |
Reacrvoir. |
Year Put in Service. |
Area in Acres. |
""TS!" |
Average Depth. Pee*. |
(Days) |
Odor Group. |
|
Worcester ft It (< Met. Water District << f < <{ Cambridge |
Lower Holden. Kent Upper Holden. Leicester Sudbury Wachusett. . . . Framingham 2 Framingham 3 Ashland Hopkinton . . . Lower Hobbs . |
1897 19OS 1878 1878 188s 1894 |
149 3 119 185 143 1292 4200 134 253 167 185 467 |
742 513 794 681 7253 63100 530 1 183 1464 1521 1450 |
15 2 13 -2 16.8 14.6 18 46 12 IS 26 26 10 |
161 142 174 235 332 534 12 43 227 261 220 |
I II II II II III III III III III III |
Average odor group 2.5
UNSTRIPPED RESERVOIRS IN MASSACHUSETTS OVER 100 ACRES
IN AREA.
Holyoke
Holyoke New Bedford Lynn Springfield Whitman.
Wright &
Ashley
Whiting
Old Storage. . .
Walden
Ludlow
Hobart's Pond
280
115 300
128
387 175
1510 500 400
403 1344
16
13
4
12
II
500 300
550 308
75
III
IV
IV
V
V
V
Average odor group 4.3
DESCRIPTION OF ODOR GROl^PS
Group I. Waters which are odorless or which have occasional faint odors.
Group II. Waters which are usually odorless but have occa- sionally a distinct and at times an unpleasant odor.
Group III. Waters which have frequently a noticeable and at times a distinct or unpleasant odor.
226 THE MICROSCOPY OF DRINKING WATER
Group IV Waters which have generally a noticeable odor which is frequently unpleasant or disagreeble.
Group V. Waters which have generally a strong and frequently an unpleasant or disagreeable odor.
These results indicate a substantial reduction in odor in the stripped reservoirs and the reduction is no doubt largely due to stripping.
The chief fact, however, to be learned from the practical application of reservoir stripping in Massachusetts is that it does not entirely or uniformly eliminate unpleasant or offensive odors from impounded surface-waters. This is shown by occa- sional tastes and odors even in the Ashland, Hopkinton and Wachusett reservoirs as they continue in service. It certainly reduces these odors to a considerable extent when compared with the results obtained under more or less comparable con- ditions from unstripped reservoirs. But the evidence is clear that stripping alone cannot be relied upon to produce an impounded water satisfactory as to tastes and odors at all times.
Effect of Stagnation Upon the Quality of Water. — ^There are four ways by which the quality of water is unfavorably affected by stagnation in the bottom layers of deep reservoirs which become stratified, namely:
1. The amount of free carbonic acid in the water increases during the time when the oxygen is being exhausted through the action of bacteria upon the organic matter. This increase in free carbonic acid, facilitates the solvent action of the water upon lead pipes and in Great Britain seems to have had con- siderable practical significance with reference to lead poisoning.
2. Odors of decay due to putrefaction of organic matters are found in the water as drawn from the bottom layers. These odors are largely due to compounds containing more or less sulphur and phosphorus. They result from the putrefaction of the organic matter originally present in the bottom and sides of the reservoir and in the water flowing into the reservoir, and also from that resulting from the organisms which either grow in the bottom layers or which reach there by settling down from the upper portions of the reservoir.
3. The appearance of the water is made quite unsightly due to the marked increase in the amount of organic matter dissolved by the water and to the iron which is extracted from the soil and which in a ferrous condition unites with the organic matter. The color and appearance of such stagnant waters
SOIL STRIPPING 227
is very high and unsatisfactory, particularly after partial aera- tion by exposure to the air.
4. In the bottom layers many kinds of organisms are found; but so far as we can ascertain it is chiefly the fimgi which grow in large numbers in the stagnant layers. Algae and diatoms when present in the bottom layers appear to arrive there only by settling down from above.
In this country the increase in color in stagnant bottom waters is noticed in practically every instance, and this is true to a greater or less extent of the odors of decay.
Comparatively little has been heard in this country of the increased power of impounded water to dissolve lead or objec- tionable fungus growths in bottom layers, but in Great Britain, as has already been stated, lead poisoning has been more or less of a practical matter. Indeed, in order to neutralize free carbonic acid in the water of the new Elan Valley reservoirs of the Birmingham supply, it was found desirable to add lime at times.. This has also been done at Burnley and else- where.
Heavy growths of Cladothrix and other fungi have been noted in several large reservoirs, particularly those of the Elan Valley works (Birmingham) and the Vymwy works (Liverpool) in Wales. Neither of these reservoirs was stripped and Lake Vymwy was not even grubbed. Although in each case water is drawn from the top, these growths have caused deposits in tunnels and pipes leading from the reservoirs to the filters and materially rjcduced their carrying capacity. So far as known these fungi do not directly cause bad odors or tastes either by growth or disintegration.
Irregularity of the Occurrence of Objectionable Growths. — We have been impressed with the evidence showing that while some reservoirs are regularly subject to troublesome growths, there are others which are troubled only at intervals. With increasing knowledge upon this subject it appears that numer- ous ponds and reservoirs, which were formerly supposed to have such clean bottoms and sides that no serious growths could result, are actually subject to such growths at intervals; and that it is more difficult than was believed in 1890 to prevent such growths.
Current views need to be more or less changed upon the following points:
a. Irregularities of seeding reservoirs with organisms.
b. Growths temporary and frequently not noticed or recorded.
228. THE MICROSCOPY OF DRINKING WATER
c. Available food for organic growths other than nitrogenous matter from reservoir bottom and sides.
J. Effect of winds and other means of securing agitation and aeration and thus preventing growths.
We will review briefly the present evidence upon the above points.
Seeding. — Troubles arise from growths of organisms in reservoir waters only when the water is seeded or infected with the organisms. This is a difficult element to take fully into account, as there are cases where reservoirs have been used for years with satisfactory results, after which, without warn- ing, objectionable growths of organisms have started. It is obviously possible and easy to confuse the absence of seeding and the absence of conditions favoring growths in seeking the true reason for freedom from objectionable growths in ponds, lakes and reservoirs.
There is not a great deal of definite information available as to how reservoirs become seeded. Sometimes the spores of organisms are brought into a reservoir by the water coming from the watershed. In other cases the spores seem to be transferred by the wind from swampy places in the general neighborhood . There seems to be no way of keeping the germs or seeds of organisms out of a reservoir ; and, although the absence of seeding appears to have been an important element in some phenomena which have been observed and which are otherwise difficult of explanation, it must be assumed that in every case a reservoir may sooner or later become seeded with objection- able vegetable or animal growth.
Among the best illustrations as to the freedom from growths of organisms through absence of seeding are those to be found in numerous ponds and lakes in the South, some of which are used as sources of water-supply and where all other conditions seem to favor abundant growths of organisms.
It may be that there is some antagonism exerted by some groups of organisms which prevents the growth of other groups. We simply mention this point as a possibility. W^e have obtained no evidence which enables us to discuss it even in gen- eral terms.
Other illustrations of the irregularity of organic growths in surface-waters are to be found in many of the large natural ponds and lakes throughout the North and including coves and arms of some very large lakes.
The development of water filtration in this country has also furnished illustrations as to the irregularity of organic growths
SOIL STRIPPING 229
in uncovered filtered water reservoirs. We have examined all available experiences in this regard and find that the results are conspicuous by the absence of growths under conditions where we would certainly expect them if the water was seeded. The list of such filtered water reservoirs, where the clear filtered water more or less resembles ground water, included experiences obtained both with sand filters and mechanical filters. Alnong such reservoirs we may mention the distributing reservoirs at Paterson, N. J., and Watertown, N. Y.
Growths Temporary and Frequently not Noticed or Recorded. — Recent information tends strongly to show that growths which would be objectionable in a public water-supply are far more frequent in natural ponds and lakes than was formerly supposed. Such growths frequently are of short duration and casual examinations do not reveal their existence. For this reason less importance is to be attached to the supposed favorable conditions in lakes having clean and sandy bottoms than was formerly believed to be the case. In fact, we know of several cases where very deep natural lakes with clean bottoms such as Lake Champlain, have developed vegetable growths in the upper layers of water.
It is also a fact that objectionable growths are frequently of an intense character for a short time and then disappear quite suddenly and leave the water in a satisfactory condition. This, of course, has much significance where the water requires a considerable period for its passage from a storage reservoir through a distributing reservoir to the consumer. It is believed that growths in some quite clean storage reservoirs have in this way escaped detection by the water consumers.
Another factor bearing upon our knowledge as to growths of organisms in reservoirs is that the results of analyses made at intervals sometimes fail entirely to show the presence of objec- tionable conditions. Even where the analyses are made at intervals of about one month, as in Massachusetts, it has been foimd in a number of instances that the reports from the lab- oratory do not correctly portray the conditions existing at the reservoir. Actual experience at Springfield and Holyoke, Mass., and elsewhere has still further shown that the agitation and aeration of samples of water during transportation to the laboratory frequently minimize the apparent amount, intensity and effect of growths of organisms.
Taking all of these elements together it is certain that more growths of organisms and more objectionable results therefrom at the source have resulted in reservoirs and natural lakes with
230 THE MICROSCOPY OP DRINKING WATER
comparatively clean sides and bottoms than was formerly supposed to be the case.
Nitrogenous Food. — The food for growths of organisms does not necessarily come from organic matter stored on the bottom of flooded areas within the flow line. Much of the organic matter may reach a storage reservoir by entering with flowing water.
Instances are numerous where large bodies of water stored in reservoirs of entirely artificial construction have been troubled with growths of organisms. The Central Park reservoirs in New York City, and the Ridgewood reservoirs of Brooklyn, are notable illustrations. Another case where organic growths obtained their food-supply outside of the reservoir is that of the Waban Hill reservoir in Newton, Mass., now used by the Metropolitan Water Board.
Weeds as Source of Food. — It is found that the organic matter which most influences the composition of the impounded water is that of the grass, shrubs and weeds which are sub- merged. Should a reservoir after having been stripped have its sides exposed so that the weeds may grow, it is difficult and expensive to prevent more or less organic matter reaching the water from this source. Experience shows that this factor relates principally to the case of large reservoirs which from time to time during dry seasons are drawn down and in the case of reservoirs which require a considerable period for their initial filling after the completion of the original stripping.
Growths of Organisms as Sources of Food. — It has already been stated that the albuminoid ammonia contents in some Massachusetts waters sometimes reach in summer about three times the normal. This increase is due to the organisms them- selves which may grow in quite large quantities in the top water of deep reservoirs and which may be entirely independent of the character of the original bottom of the reservoir. Such growths sooner or later subside in large part to the bottom of the reservoir and tend to accumulate upon it. The decomposi- tion of the matter so deposited furnishes the material for sub- sequent growhs.
It is quite apparent that stripping affords no assurance that ample food will not be available in the upper water for organic growths sooner or later. This is all the more apparent when it is realized that during periods of vertical circulation follow- ing periods of stagnation there is such a mixing of the water that the top layers may be supplied with necessary food coming from the decomposition of organisms deposited on the bottom.
SOIL STRIPPING 231
Sewage Pollution as Source of Food. — In the early Massa- chusetts data it was stated, that where there was a population of 300 or more per square mile of drainage area, the organic matter and other substances, such as nitrates, etc., resulting from this population had a pronounced influence upon the organic growths. In recent large projects for impounded water-supplies the catchment areas have usually been so sparsely populated that sewage pollution appears to be a very small factor. Indeed it is believed that it may be practically ignored in such cases. The population upon the Esopus watershed is very small.
Temperature of Surface-water. — Objectionable growths of Prot07X)a and diatoms are sometimes found in reservoir waters during the winter when the water is covered with ice. Diatoms and some forms of algae appear in objectionable quan- tities during the spring and fall periods of overturning. It is during warm weather, however, when the temperature of the water is near or above 70 degrees that the greatest and most objectionable growths of blue-green algae are encoun- tered, and it is these growths which have given the greatest amount of trouble in this country. The temperature of the water is apparently of controlling importance with reference to growths of anabaena and some other blue-green algae.
The fact that in Great Britain the summer temperature of reservoir waters seldom exceed 65 degrees and only exceeds 60 degrees for short periods, is probably the explanation of why the upper layers of water in the large English reservoirs have been so singularly free from objectionable growths of blue-green algae. Accordingly the British experiences are not to be used as safe precedents as to midsummer complications from growths in American reservoirs. Wc understand that this fact was appreciated by the Massachusetts authorities in 1890.
Wind and Agitation. — Increasing information has shown that a vigorous development of certain filamentous algae is reached only in a fairly quiet state of water. As pointed out by Dr. Drown, this is one reason why they do not occur in river waters. The waves produced by the winds in compratively large reser- voirs and lakes are often sufficient to prevent such growths. At Ludlow reservoir, in Springfield, vigorous growths of anabaena have sometimes appeared, and a single windy day has sufficed to eliminate them. This wind action breaks up the growths, causing them to subside, and it may be weeks before they appear again. Toward the end of the season they may not start again after having been once broken. Small
232 THE MICROSCOPY OF DRINKINQ WATER
lakes are less disturbed by wind. This is one of the reasons why small lakes, other things being equal, are much more subject to growths than larger lakes or reservoirs. This also explains in part why organic growths often develop in coves protected from wind action, and particularly where water weeds prevent agitation of the water.
The wind not only affects the organisms mechanically, but influences their growth by controlling the amount of car- bonic acid in the water. A gentle breeze, just suflident to stir the water of a shallow reservoir to the bottom, but without causing high waves, may increase the amount of carbonic add in the upper layers by carr>'ing it upward from the bottom; while a heavy wind in the same reservoir might reduce the carbonic acid in the upper layers by making Qie loss to the atmosphere greater than the increase from the bottom.
Reference may also be made to the growth of organisms in a distributing reservoir supplied with water from a large lake where the organisms do not grow, as has been frequently observed. It seems to be accounted for by the relative pro- tection of the water from the action of the wind in the smaller area of this distributing reservoir. A striking example of this is furnished by Syracuse, where objectionable growths have occurred in the distributing reservoir supplied with water from Skaneateles lake. Other examples are the reservoirs of Burlington, Vt., and Cleveland, Ohio, which are supplied with water from Lake Champlain and Lake Erie, respectively.
In this connection it is interesting to cite the explanation • of Prof. Shaler as to why some of the large lakes and ponds have continued to the present day without becoming entirely filled up with peat and muck resulting from vegetation in the water, as in the case of most of the lakes left by the glacial period in New England which have become filled. He states that the controlling factor is the existence of wave action which prevents the growth of organisms which would otherwise fill up the lake.
Conclusion as to Advantages of Stripping the Reservoirs. — We conclude from the available evidence that the effect of stripping the bottoms and sides of reservoirs upon the quality of the reservoir water as regards stagnation, is as follows:
1. The stripping of the sides and bottom of a reservoir will ordinarily prevent stagnation of the bottom layers for a period of years the length of which depends upon various local conditions. In the Boston reservoirs this period does not seem to exceed from lo to 20 years.
2. Ultimately it makes comparatively little difference as
SOIL STRIPPING 233
to stagnation of the bottom layers whether the sides and bottom of a reservoir are stripped or not.
3. By aeration and filtration of the bottom water of deep reservoirs there can be obtained a better quality of water without the benefit of stripping, than it is possible to obtain with the aid of stripping in the absence of aeration and filtration.
4. In the absence of stripping substantially as good a quality of bottom water may be obtained after aeration and filtration, as in the presence of stripping. In fact, as just stated, decolor- ization and purification are facilitated by the absence of stripping due to bacterial agencies which make some of the iron in the soil available as a coagulant.
5. In view of the above and as aeration and filtration will ultimately be required in order to obtain satisfactory results in this climate, present evidence and experience indicate that beyond grubbing a reservoir it is unwise to spend money for further removing organic matter from the bottom and the sides.
We may add that we are aware that materials obtained in stripping may be used successfully in building dikes, as at the Wachusett reservoir, and that by so doing the net cost of stripping may be reduced. We also take into account the fact that any deep deposits of muck when sufficiently firm to carry it may be covered with sand at less expense than would be required for their complete removal. We will not enter into a discussion in this report of different methods of reservoir con- struction, but will simply state that in the preceding paragraph we have had in mind the net cost of stripping.
Comparative Cost of Stripping. — The cost of stripping the Ashokan reservoir would be very great, possibly as much as five million dollars. Aeration of the water as it leaves the reservoir will do as much, if not more to remove the tastes and odors than stripping would do to prevent them, and the cost of aeration would be only a small fraction of the cost of stripping.
For the cost of thoroughly stripping the Ashokan reservoir it would be possible to build a filter plant to filter all the water that could be obtained from the Esopus watershed; and a filter plant between the Kensico reservoir and New York City, following aeration, would be far more efficient in preventing tastes and odors and in otherwise improving the quality of the water, as supplied to the consumers, than stripping could be, even under the most favorable conditions.
We are firmly of the opinion that materially better results, due to the stripping of the Ashokan reservoir, could not be
234 THE MICROSCOPY OF DRINKINa WATER
obtained by such aeration and filtration, as regards either the quality of the purified water or the cost of purification.
Further, if for financial reasons it is necessary to defer the construction of filters until after the first water is delivered to the City from the Ashokan reservoir, it still will be unwise to strip the reservoir. It is better to save any money that might be so spent for use in providing filters when that becomes pos- sible.
Recommendations as to the Treatment of the Ashokan Reser- voir.— Our conclusions, after careful deliberation upon this matter, in the light of experience now available from various large city water-works, lead us to the following recommenda- tions:
1. Clearing and Grubbing. — Cut all trees and bushes close to the ground over the entire area of the sides and bottom.
2. Burning Vegetation. — Bum all grass, weeds and shrubs and see that this is done shortly before the areas are flooded. In other words, do not allow the water to flood any areas on which expansive growths of weeds have occurred since the original preparation of the area.
3. Preparing the Shores, — Around the shore of the reservoir, to a vertical depth of at least 20 ft. below high water, remove all stumps, and, so far as necessary, roots and other matters which might become exposed by continued wave-action; and leave the surface with even slopes, so that the shores will be maintained in a presentable condition when the water is drawn down. We do not think it is necessary to spend a large amount of money in this prcp^^ration. The wave-action will tend to clean it and accomplish the desired results, but some extra attention should be given to it with reference to its appearance when exposed, and also to prevent as far as possible the leaving of enclosed shallow areas which might serve as places where the spores of organisms would remain and serve as centers of infec- tion when conditions in the reservoir became favorable.
4. Preparing the Bottom, — After removing all the top vegeta- tion from the swamp areas, which can be done by cutting it off close to the surface and burning, careful examination should be made for places where the surface ** crust '' is so loosely attached to underlying soft material that it might rise after the reservoir is full. Wc have given this question some atten- tion when examining the swamps, and their surfaces wherever we have seen them arc such that this factor does not appear to he of much importance here. However, experience elsewhere indicates that it should be given further attention.
SOIL STRIPPma 235
5. Each Basin to Have OuUeL — ^The separation of the reser- voir into two parts, with outlets so that water may be drawn from either or both basins into the aqueduct, seems advantage- ous to us.
6. Draw at Any Level. — ^We recommend that the reservoir outlets be arranged so as to permit water to be drawn from any desired depth.
7. Aeration, — ^Arrangements should be provided to aerate thoroughly all the water passing from the reservoir to the aqueduct, except perhaps at times of extremely low stages of water in the reservoir. This can be accomplished by fountains and basins, or other effective appliances to make available the head of the water in leaving the reservoir for bringing it in contact with air to remove the gases, which produce tastes and odors and which result from putrefaction in the stagnant layer and odors from the growth of organisms in the water; and also the carbonic acid which otherwise might serve as a food for further growths in the Kensico reservoir.
In making the foregoing recommendations we desire to state clearly, that we consider:
First, that the stripping of the Ashokan reservoir in itself will not sufficiently prevent tastes and odors so as to allow water of satisfactory quality to be obtained from it at all times.
Second, that aeration at a small fraction of the cost will do fully as much in removing tastes and odors as stripping would do in preventing them.
Tlurd, that water of perfectly satisfactory quality can be obtained by aeration and filtration.
Fourth, that this result can be just as certainly and fully accomplished in this way if the Ashokan reservoir is not stripped as if it is stripped.
It is certainly more important to consider the questions of the quality of the water leaving the Kensico reservoir than that of the water leaving the Ashokan reservoir. In accordance with your instructions, we shall report upon the treatment of the Kensico reservoir in a subsequent communication after further local data are available.
Effect of Aeration and Filtration upon the Quality of the Kensico Water and the Relation of the Same of Stripping. — This matter was carefully considered by Messrs. Hazen and Fuller in connection with the report on the stripping of the Ashokan and Kensico reservoirs of the New York City water- supply. The following extended quotation from their report bear upon the subject:
236 THE MICROSCOPY OF DRINKING WATER
We have considered the question whether, with aerators and filters installed, the tastes and odors resulting from growths in the reservoir would be entirely removed at all times, and whether it would not be worth while to strip this reservoir for the sake of securing a better water after filtration.
We have considered this question in the light of all avail- able evidence as to the effect of aeration and filtration in the removal of tastes and odors. We are most decidedly of the opinion that after aeration and filtration the water will be uni- formly of satisfactory quality whether the reservoir is stripped eor not, and that stripping the reservoir will make no appredabl difference in the quality of the filtered water.
Aeration. — The effect of aeration alone in reducing taste and odors in a number of well established examples was set forth in our report on the stripping of the Ashokan reservoir. Among these we mentioned the removal of odors from the water from the Newark, N. J. reservoirs; from the Grassy Sprain reservoir at Yonkers, N. Y.; from the Whiting Street reservoir at Holyokc, Mass.; and from the Ludlow reservoir at Springfield, Mass. These cases are all well attested. We believe there can be no doubt as to the results that are prac- tically obtained by aeration. These cases have great weight with us, because we have known about them personally, and have observed the great reduction in tastes and odors which has been brought about by a simple and inexpensive method of adequate exposure to air.
Aerating as we have it in mind is not comparable with that resulting from exposing the water to air in the aqueduct. We take aeration to mean the exposure of water in fine drops, practically spray, for an interval of say 2 seconds or more cor- responding to a nozzle discharge under at least 16 feet head. The 16-foot head and the 2-second interval are not given in any way as limits. Actually, more head will be used when available, and with the reservoir drawn down smaller amounts of head and exposure will be used which, though less effective, will still be serviceable. Such aeration for the head and interval mentioned will not only oxygenate water, but it will, as indicated by the data at our disposal, reduce free carbonic acid from about 20 to about 5 parts per million and remove considerably more than half or probably three-quarters of the odors of growth and of decomposition.
Filtration. — The reduction of tastes and odors by filtration to a greater or less extent, and often to the extent of entire removal has been a matter of common observation. We have
SOIL STRIPPING 237
personally noted such reductions in many cases. We have also known some cases where filtration, as actually carried out, has failed to sufficiently remove tastes and odors, but we have known of no case where tastes and odors could not be sufficiently removed by filtration and adequate aeration.
)\Tiere waters have contained abnormally large amounts of organic matter, much more thorough methods of treatment are required than in other cases. The application of methods, sufficient for the treatment of water that is only moderately bad, have failed when applied to the treatment of the worst waters. We have kept clearly in mind all such comparative failures that we have known about, and we fully believe that they do not afford the slightest ground for assuming that well selected methods at moderate cost will not be fully adequate in this case.
Among the cases where filtration has served to entirely remove tastes and odors we may mention the English expe- riences, where waters from many impounding reservoirs are supplied after filtration without any complaint from tastes and odors. We may also mention the case of Reading, Pa., where filters were constructed for the specific purpose of removing tastes and odors from the water of an impounding reservoir. These filters operate at a rate of 5,000,000 gallons per acre daily while one of the filters is out of service for cleaning, which, in sum- mer time, is a considerable percentage of the time; otherwise at a somewhat lower rate. These filters were installed as the result of successful experiments upon the removal of tastes and odors from these reservoir waters, and have been in service for a sufficient length of time to fully test them. Mr. Emil L. Nuebling, Superintendent of Water Works, writes as follows:
" Our Antietam filters operate at a rate of 5,000,000 gallons per acre daily only when one bed is out of commission on account of scraping and refilling, but they have at all times successfully removed the tastes and odors which were formerly so obnoxious that the water, at times, could not be used during the periods of Anaba^na growths. Some of the success in removing the odors may be attributed to the aeration of the raw water before it passes through the filters.''
At Brisbane, Australia, with experimental filters, water from the Enoggera reservoir, having very bad tastes and odors, has been purified so that the effluents from certain devices, corresponding in a general way to those proposed for the New York water-supply, though with much worse water and with a lower rate of filtration, have uniformly produced effluents
238 THE MICROSCOPY OF DRINKING WATER
entirely free from tastes and odors. This was tested by one of us to his personal satisfaction at the time of his recent visit to Australia by most carefully tasting and smelling of the various waters upon the ground; and we have the assurance of the chemist and other competent persons as to the con- ditions at other times.
As stated above, there are some limits to the removal of tastes and odors by filtration. These limits are investigated at length at Springfield, Mass., and the investigations were conducted partly by the Massachusetts State Board of Health. The quality of the water of the Ludlow reservoir at times went beyond the point where simple filtration at such rates as are proposed for the Ashokan water was capable of removing the tastes and odors, but it only went beyond the limit at a certain season of the year. The State Board of Health in their report of April 3, 1902, states as follows in regard to the filtration of the Ludlow reservoir water:
** This filter was operated, except for a short time, as a con- tinuous filter at a rate of 2,500,000 gallons per acre per day, and in the latter part of the year at a considerably higher rate, and was successful in removing the objectionable odors from the reservoir water except at the time of the presence of the excessive quantities of organic matter in August and September when the eflluent of the filter had for a time the odor character- istic of the water of the reservoir and in nearly as pronounced a degree. The results obtained by filtering the water through other similar filters at a rate nearly twice as great as that employed during the year with a large filter were nearly equal to those obtained with that filter. None of these filters, how- ever, to which the Ludlow water was directly applied removed the characteristic odor from the reserv^oir water during the time in August and September when this water contained excessive quantities of organic matter.*'
Filtration at this high rate, practically as high as proposed by us for the Catskill supply, thus sufficed to fully remove the tastes and odors from Ludlow water for ten months of the year or more.
The Ludlow reservoir is perhaps the most notoriously bad smelling reser\^)ir in the United States. Some other reservoir waters are no doubt worse, but they are less well known than the Ludlow reservoir and have not been studied so care- fully. It is certain that the water of the Ashokan and the Kensico reservoirs will never reach a condition even approx- imating the worst conditions at Ludlow. It is reasonably
SOIL STRIPPING 239
certain that these reservoirs will never become charged with organisms, and with the tastes and odors resulting fuom their growth, to a greater extent than was reached by the water of Ludlow reservoir during those ten months of the year when simple filtration at a high rate sufficed to completely remove tastes and odors. The Springfield experiments made by the Massachusetts State Board of Health, therefore, give assurance of the success of the method of filtration proposed as applied to the waters of the Ashokan and Kensico reservoirs.
Still additional data from Springfield, Mass., are available in reports of Mr. E. E. Lochridge, now Engineer of the Water Department of that city. For some ten weeks in 1903 he conducted an elaborate series of tests, under the direction of Messrs. Gray and Fuller, with, results as set forth in a special report to the City Council of Springfield, March 28, 1904. These tests were made during the " Anabajna period," when the water is in its worst condition and included experiments not only with the Ludlow reservoir water, but also with the much worse water of the Belcherton reservoir which was abandoned as a source of water-supply years ago.
The water from the reservoirs was put through a strainer or roughing filter and also aerated before it was put through various sand filters at rates ranging from 3,000,000 to 10,000,000 gallons per acre daily. Taking into consideration the quality of these reservoir waters as applied to the sand filters, as shown by daily analyses, in comparison with the quality of the water of the Catskill supply, and bearing in mind that the Catskill water can be readily aerated much more thoroughly than was actually done in the Springfield tests, there is no room for doubt that the filtration of the water from the Ashokan and Kensico reservoirs at rates averaging 5,000,000 gallons per acre daily will be entirely satisfactory.
We do not refer to the actual successful experience with the intermittent filtration of the Ludlow water, because intermittent filtration is adapted to treat very bad water and probably is no better than continuous filtration for treating waters that are not exceptionally bad. It could be used at Kensico, should the conditions require it; but there is no indica- tion that it will be required, or that any better results could be secured with it.
The removal of tastes and odors from the water of Goose Creek reservoir at Charleston, South Carolina, may also be mentioned as an extreme case. Goose Creek reservoir was made by flooding 1,800 acres of uncleared marsh covered
240 THE MICROSCOPY OF DRINKING WATER
â–
with much vegetation to an average depth of 3.5 ft. The water in it is exposed to a sub-tropical sun, and has growths of organisms greater than could ever be anticipated in tihe latitude of New York. It has been treated with substantially satis- factory results. It is true that the process is more elaborate and extended than is proposed for New York. Allowing for the difference in conditions it is clear that no such methods as are actually used at Charleston would ever be required for treating the New York waters. We dte the Charleston case, from among a number of successful experiences in treating bad-smelling waters, simply to show that tastes and odors can be sufficiently removed eve.i when present to an extent many times greater than can be reasonably anticipated in the waters under consideration.
We are perfectly satisfied as a result of the evidence herein mentioned, and of our general experience with filters, and of observing their operation and of noting the odors before and after filtration, that the proposed filtration works will serve to fully remove tastes and odors from the proposed Kensico reservoir water, and that, practically si)eaking, this result will be reached with equal certainty whether the reservoir is stripped or only cleared and grubbed as herein recommended.
Effect of Stripping on the Cost of Filtration. — It is pos- sible that the stripping of the Kensico reservoir would reduce the growths of organisms in such a way as to reduce the cost of filtration. It might be possible to operate the filters, tak- ing water from a stripped reservoir, at a higher rate, thus reduc- ing the size and first cost of the plant; and it might also be that they could be operated for longer periods between cleanings, thereby reducing the cost of operation. These matters we have considered at length.
Generally speaking, the conditions which limit the rate of filtration and size of a filter plant are the winter conditions. Any filter plant sufficient to meet the winter conditions will be able to perform satisfactorily during any summer conditions likely to exist in the proposed Catskill supply, or in any ordinary reservoir supply. There is no evidence that the stripping of the Kensico reservoir would make any material difference with the condition of the water in the winter. If the winter conditions should be the limiting ones at Kensico, then the stripping of the reservoir would make no difference with the allowable rate of filtration . It may be, however, that the removal of tastes and odors in summer would be the limiting condition of the rate that could be used. There is no indication, from
SOIL STRIPPING 241
the records of the present Kensico reservoir water nor from any other data elsewhere which we have at hand, that this would be so for a plant provided with adequate aeration. Practically, we do not believe that this would be the limiting condition. Conceding, however, for the moment for purposes of discussion, that summer growths might control, we can at least make an approximate calculation of the additional cost that would be involved.
In a previous communication we proposed the use of an average rate of 5,000,000 gallons per acre daily as a proper one for the purification of this water. This is based on the use of water from an unstripped reservoir.
For the purpose of calculation assume that with a stripped reservoir a rate of 6,000,000 gallons per day could be used instead of the 5,000,000 rate above assumed. It should be distinctly understood that we have no reason for believing that such a relative increase in rate would be possible, and we do not believe, that the difference in conditions would justify such an allowance; but we make the computation to show the amount of money that could possibly be saved in case such an assumed increase in rate were made possible by stripping. Conceding for the moment that such a difference might be made, for an average yield of 250,000,000 gallons per day from the Ashokan watershed, it would make the difference between 50.00 acres and 41.67 acres of filter surface. The difference in area would thus be 8 1-3 acres, costing perhaps $600,000, without including the piping and general appliances that would be the same whatever the rate. This is certainly the largest possible estimate which can be placed upon the difference in cost of filter plant attributable to stripping.
Stripping would make no difference in the settling basins which were suggested and have been considered in some of the filter projects. Such settling basins are clearly unnecessary in connection with the treatment of any and all waters to be derived from the Ashokan watershed. Such basins were con- templated only for use in connection with the waters from other watersheds yielding highly colored waters to be ultimately diverted to the Ashokan system ; and in the light of the present evidence it seems unlikely that such treatment would be required even with these matters after they had passed the Ashokan reservoir. Certainly the stripping of the Ashokan and Kensico reservoirs would have no tendency to remove the color from such waters.
We have also considered the probability of obtaining longer
242 THE fflCROSCOPY OF DraNKING WATER
periods between the cleanings of filters with the cleaner water from a stripped reservoir, and the consequent reduction in the cost of operation.
In considering this point the operation of covered filters and open filters must be sharply distinguished. Most of the filters with which the experiences in removing tastes and odors have been obtained have been open filters. For the filtration of this water we are considering the use of covered filters. Open filters are often choked and clogged more rapidly by organisms which grow in the water upon them than by organisms which may already be in the incoming water. For this reason the evidence as to the frequency of cleaning of open filters does not have much bearing on the frequency of cleaning to be reason- ably expected in the operation of covered filters.
Considerable experience has been had with the rate of clogging of filters by other substances than vegetable growths on the filters, and this allows some idea to be formed of the probable effect of a greater or smaller number of organisms upon the cost of operation. Taking it up on the basis of such general experience, the rapidity of clogging would not be proportional to the number of organisms. Doubling the num- ber of organisms would not reduce the period by more than one-fourth. P'urther, the expense of operating a filter plant is not directly proportional to the amount of cleaning and of washing and of handling sand. Takmg it altogether, a wide difference in the number of organisms would be necessary to produce a considerable effect upon the cost of of>eration of filters.
For eight months in the year there is no reason to suppose that stripping would affect the frequency of cleaning or the cost of filtration in any way. For four months in the year, more or less, it is possible that some difference in the length of the runs would be made. A very liberal estimate is that the cost of operation for this period might be reduced one-third by stripping. This would represent a reduction of one-ninth in the cost of operation of the filters for the whole year, attributable to stripping.
The cost of operating filters with the Ashokan water, and with modern appliances for cleaning filters and handling sand, would certainly not exceed 75 cents per million gallons. It is likely that it would be much less than this figure. One- ninth of 75 is 8 1-3 cents per million gallons as the extreme amount of saving which could be made in the cost of operation by stripping. For 250,000,000 gallons per day, the amount
SOIL STRIPPING 243
of water which can be obtained from the Ashokan watershed, this saving would amount to $20.83 P^^" day, or $7,600 per year, equal to 5 per cent on a $152,000 investment; and this repre- sents the largest possible amount, as we see it, which could be saved in the cost of operation by stripping the Ashokan and Kensico reservoirs. With less than the full amount of water used the sjiving would be proportionately less. The total saving possibly made in the case of filtering on these lines would, therefore, be:
Saving in cost of plant $600,000
Capitalized cost of operation 152,000
Total amoimt to be saved $752,000
We repeat what we said at the outset: We have no reason to believe, and do not believe, that any such saving could be made. The calculation is given to show the maximum possible saving which could be made under assumed conditions. The saving even if made in the first years would not be permanent. It would gradually decrease to nothing as the deposit which forms on the bottom of reservoirs in this climate gradually covers the present surface and eliminates its effect upon the water. The significance of such deposits in several of the present reservoirs of New York City has already been recorded in this report.
As against this possible saving, which we believe is much larger than could actually be reached, the cost of stripping the Kensico reservoir is roughly estimated at $1,100,000, and the cost of stripping the Ashokan reservoir is estimated at $5,000,000, making the total cost of stripping $6,100,000.
There is no possible way in which the cost of stripping, or any considerable portion of it, could be saved through a resulting reduction in the cost of construction and operation of filters.
Questions Connected with the General Operation of the Plant. — We do not deem it necessary at this time to enter into a discussion as to whether it would be best to draw the water from the top or from the bottom of the Kensico reservoir, or for what portions of the time it would be best to draw from the top or the bottom or from any intermediate [)oint. When the plant is put in service it will be operated under trained and intelligent supervision. The results actually to be obtained by the use of water from different points will be soon ascer- tained, and water can and should be drawn at all times from
244 THE MICROSCOPY OF DRINKING WATER
that part of the reservoir which yields the best results. In our previous report upon the stripping of the Ashokan reser- voir we have attempted to give some description of the prin- cipal changes and growths taking place in the different parts of such a reservoir, and of their practical effects upon the quality of the water, and of the ways in which water from the different parts can be most advantageously handled; but we regard it as a useless speculation to attempt to determine in detail at this time how the plant can best be operated in practice, in view of all the varying conditions from season to season. .
In the same way, we have in mind that in practical operation water will be drawn to the filters directly from Kensico, or through the aqueduct and by-pass from Ashokan, according as the best results can be obtained. The usefulness of the Kensico reservoir as a reserve against accidents and repairs to the aqueduct, will not be in the least reduced by the direct use on the filters of Ashokan water whenever better results can be obtained in that way.
We have also considered the possibility or probability that disagreeable odors in troublesome quantities will be evolved by the aerators. In considering this question we have kept in mind that the water quantities will be large; that strong growths of objectionable organisms are sometimes to be antic- ipated, and that water which has been through vigorous putrefaction would necessarily be drawn at times. This would happen at the times of the spring and fall turn-overs, even though bottom water were never drawn. We have considered that there might be times, when, because of these odors, it would be inexpedient to use the Kensico water drawn through an aerator at the outlet of that reservoir, and that at such times it would be desirable to use water coming directly from the Ashokan reservoir. We have considered that probably for a large part of the year it would make but little difference in the practical results whether the aerators at Ashokan and at Kensico were used or not. There will be times, however, when the use of the aerators will be absolutely essential to secure the desired quality of water. The aerators at both reservoirs must be provided for these occasional periods. When they are provided, with the proposed arrangements, it will cost practically nothing to operate them. Aerating the water at other seasons of the year than when necessary will tend in a general way to improve its quality. The tendency may be slight for a large part of the time, but it will be in the right direction. The aerating plants that we have suggested will
SOIL STRIPPING 245
also be more or less pleasing features of the landscape, and objects of interest to the public.
We, therefore, consider that the aerators will no doubt be often used, even when they have but little efifect upon the quality of the water.
Conclusions as to Stripping. — ^After full consideration of the question of stripping the proposed Kensico reservoir we are firmly convinced that stripping without filtration will not produce at all times water of satisfactory quality.
If, however, for financial reasons it is necessary to defer the construction of filters it is still unwise to strip the reservoir. It is better to save any money that might be so spent for use in providing filters when that becomes possible. We are equally convinced that stripping will not materially affect the efficiency or the cost of filtration.
Filtration and aeration, without the stripping of either the Ashokan or Kensico reservoirs, will enable an entirely satis- factory quality of water to be delivered to The City, and this is the treatment which we advise.
We recommend that the sides and bottom of the Kensico reservoir be well cleared, as recommended for the Ashokan reservoir, and that they be not stripped.
We recommend that the shores of the Kensico reservoir be treated with special care to a vertical depth of 35 feet, in the way that was suggested for the treatment of the shores of the Ashokan reservoir, to a depth of 20 ft. This additional depth is with reference to the possible depth that the reservoir will be drawn, and to its location near to New York City, and in a populous district, where it will be under observation, and where the maintenance of the shores in a sightly condition, at all times is highly desirable.
CHAPTER XV STORAGE OF GROUND-WATER
Ground-water must be stored in the dark in order to prevent the growth of microscopic: organisms.
Water that has passed through the soil usually carries mineral matter in solution, some of which forms an important ingredient of plant-food. It also usually contains free carbonic acid. WTien such water is stored in an open reser\'oir it is liable to deteriorate. Diatoms especially are liable to develop, because their mineral contents are greater than those of most plants, much silica being required. These growths are less likely to occur in a new reservoir than in one that has been long in use. The seeding of the reservoir must first take place. As a rule some of the littoral organisms develop first, growing on the sides or even on the bottom of the reservoir. Gradually a de- posit of organic matter collects at the bottom, and the con- ditions become favorable for the growth of the limentic organisms.
Of the diatoms that occur in ground-water exposed to the light Asterionella is by far the most troublesome. Others may make the water turbid, but the Asterionella is very odoriferous. In surface-waters it has been found that this organism develops most vigorously after the stagnation periods. It is probable that this is true also in ground-waters. Most reservoirs for the storage of ground -water are shallow and of comparatively small size. Often water is not pumped directly through them. Such reservoirs become stagnant at times, and it has been observed that in them the Asterionella show a spring and fall seasonal distribution like that observed in surface-
246
STORAGE OF GROUND-WATER 247
waters. It sometimes happens that for many years an open reservoir gives no trouble, but that finally a layer of organic matter acounulates at the bottom, the water in some way becomes seeded with Asterionella, and thereafter regular growths of these organisms occur. If open reservoirs are to be used for the storage of groimd-water they should be kept clean.
Mixed Surface and Ground-water. — ^When a water-supply is taken partly from the surface and partly from the groimd it is even more necessary that covered storage reservoirs should be used. This is because the surface-water may contain organisms the growth of which in the reservoir would be stimulated by the food-material in the ground-water, and because organic matter will be deposited from the surface-water, increasing the effects of stagnation and making it possible for Asterionella growths to occur. The water-supply of Brooklyn, N. Y., presents an interesting example.
The supply of this city is derived from a number of small storage reservoirs along the southern shore of Long Island and from driven-well stations and infiltration galleries along the line of the aqueduct. The well-water is drawn from depths varying between 25 and 200 ft. The waters become mixed in the aqueduct and are stored in three basins comprising Ridgewood reservoir. The different sources of water vary greatly in character. Some contain an abundance of organic matter; some have high free ammonia, nitrites, and nitrates; some have considerable iron; and one or two have high chlorine and hardness due to admixture of a small amount of sea-water. All have carbonic acid. The watershed is sandy, and the waters are rich in silica.
Asterionella in Ridgewood Water. — In 1896 Asterionella developed in Ridgewood reservoir in great abundance, and since then it has reappeared at intervals. In a general way these growths have shown the spring and fall distribution, but they also correspond to some extent with increased propor- tions of ground-water used. At times the numbers of Asterio- nella present have been very high — 25,000 or 30,000 per c.c.
248 THE MICROSCOPY OF DRINKING WATER
For many years Ridgewood reservoir caused no trouble and the water-supply bore an enviable reputation. It was not until a considerable deposit of diatoms and other organic matter had accumulated on the bottom of the basins and until the amount of groimd-water had come to be about 40 per cent of the total supply that the conditions became favorable for such enormous growths of Asterionella. Fortunately for the consumers, a by-pass aroimd the distributing-reservoir permits the water to be pumped from the aqueduct directly into the distribution system. This was used whenever the Asterionella in the reservoir become abundant enough to cause a bad odor. During recent years copper sulphate has been used.
Storage of Filtered Water. — ^Water that has been filtered resembles groimd- water, and microscopic organisms may develop in it to such an extent as to cause trouble. For this reason provision is generally made for storing filtered water in covered reservoirs. Often, however, from motives of economy, it is necessary to use existing reservoirs which are not covered. Such reservoirs at times become affected with microscopic organ- isms, but these seldom cause as much trouble in filtered water as in ground-water exposed under similar conditions. Water which has been filtered by the mechanical system of filtration is somewhat more liable to growths than the same water filtered by sand filtration. This is because the use of sulphate of alumina leaves a certain amount of dissolved free carbonic acid in the water, which tends to favor the growth of the organ- isms. On the other hand the effluent of a sand filter may con- tain a larger amount of nitrogen in the form of nitrate, a con- dition in which it is more available for use by the algae. The controlling factor, however, is usually the length of storage in the reservoir. If the period is short the growths are usually insignificant, but if the water is kept in the reservoir for many days algx are likely to develop to a troublesome extent.
As an illustration of the effect of storage on a filtered water the following figures taken from analyses of the Hudson River water at Poughkeepsie, New York, before and after filtration are interesting:
STORAGE OF GROUND- WATER
249
|
Date. 1903. |
Microscopic Organisms per c.c. |
|
|
Raw Water. |
Filtered Water after Storage. |
|
|
April 2^ |
60 70 95 65 205 230 185 |
1455 135 65 130 655 2440 2265 |
|
May II |
||
|
June 8 |
||
|
June 20 |
||
|
Julys |
||
|
J **^^ " July 2^ |
||
|
AuiTust 6 |
||
Growth of Organisms in the Dark. — ^Darkness is not always sufficient to prevent a ground-water from deteriorating. There are some organisms that can live without light, and indeed prefer darkness. Of such a nature are the fungi (using the word in its broad sense as including those vegetable forms destitute of chlorophyll) and some of the Protozoa and larger animal organisms.
Crenothrix in Ground-water. — Crenothrix is the most important organism of this character that affects ground-water supplies. It is a small filamentous plant, the cells of which are but little larger than the bacteria. Its filaments have a gelatinous sheath colored brown by a deposit of ferric oxide. It grows in tufts, sometimes matted together into a felt-like layer. Other organisms similar to Crenothrix are Clonothrix, Gallionella and Chlamydothrix.
Crenothrix is liable to occur in groimd-water rich in iron and organic matter. It frequently infests water obtained from wells driven in swampy land. It is often observed in imper- fectly filtered water. It may grow in almost any part of the system — ^in the driven wells, filter-galleries, reservoirs, and distribution-pipes. It is especially liable to occur about wood- work.
Crenothrix causes trouble in tubular wells by choking them with deposits of iron. It causes trouble in the service-pipes by reducing the capdty of the pipe. But it causes most trouble when the filaments break off and become scattered through
250 THE MICROSCOPY OP DRINKINa WATER
the water. It is then liable to make the water unfit for laun- dry use on account of deposits of iron-rust.
Crenothrix has caused annoyance in many water-supplies. The " water calamity " in Berlin first drew attention to is evil effects. In 1878 the water from the Tegel supply became filled with small, yellowish-brown, flocculent masses which settled to the bottom when the water was allowed to stand in a jar. The odor of the water and the effects of the iron oxide in washing were decidedly troublesome. Crenothrix was not found in Lake Tegel, but was foimd in many wells, in the reservoirs at Charlottenburg and in the unfiltered water of the river Spree.
In 1887 the water-supply of Rotterdam was badly affected with Crenothrix. The water was drawn from the river Maas, and, after sedimentation, was filtered. At the time when Crenothrix appeared the system was being enlarged. New filter-beds were in use, but the filtered water was conducted through the old conduits and the old reservoir to the old pumps. In the old conduit, or flume, there were many wooden timbers, and on these Crenothrix was found growing in abundance. Inspection showed that some of the water was imperfectly filtered, and that this impure water was the chief cause of the sudden and extensive development of Crenothrix.
It has been recently found that Crenothrix thrives best in water which contains little or no oxygen but where carbonic oxygen is present in considerable amounts.
For a more complete description of the organisms in this group the reader is referred to ** Die Eisenbakterien," by Dr. Hans Molisch.
Floating Roofs. — Various attempts have been made to prevent the access of light to reservoirs by constructing cheap roofs or floating rafts of boards. It is said that in some cases these have effectually prevented the growth of algae. They do not appear to have been permanently successful and their economy is questionable, except for very small reservoirs. If used at all the entrance of sunlight through the cracks between the boards should be prevented.
CHAPTER XVI COPPER TREATMENT FOR ALGiE
In 1904 Dr. George T. Moore and Karl F. Kellerman, of the Bureau of Plant Industry, U. S. Department of Agri- culture published a report stating the results of successful experiments made by them in the eradication of algae and other microscopic organisms from reservoirs by the use of copper sulphate. This report immediately attracted wide attention and .the method was tried in many places. Nearly ten years' experience has shown its advantageous use in many situations and has likewise developed some of its short- comings.
Copper sulphate had been used as a fungicide long before Moore proved its worth for destrojang algae. Many experiments had been made by Miquel, Devaux, and many others, which showed that very minute doses of poisonous substances were able to destroy the imicellular microscopic organisms, but Moore deserves full credit for the use of copper sulphate in water-supplies. The first practical test on a working scale was made by him at the water-cress beds in Ben, Va., in 1901, where a troublesome growth of Spirogyra was eliminated.
Effect of Copper on the Human System. — ^The first question that was naturally raised when the copper treatment was mentioned was its possible effect on the human system. Moore had collected extensive data to show the extent to which copper salts were used in medicine and the wide distribution of copper in nature, its presence in vegetables and even in natural waters themselves. Clark showed that some natural waters in Massachusetts contained small amounts of copper. Experience with the use of copper in many water-supplies has fully demon-
251
252 THE MICROSCOPY OP DRINKINa WATER
strated the innocuous character of this treatment if prt^rly carried out. It is not a matter, however, that should be left to the ordinary laborer. It needs intelligent and continual supervision.
Method of Applying Copper Su^hate. The method of application is extremely simple. Ordinary conunerdal crystals of blue-vitriol are used. The required quantity of these cr)rstals is placed in a coarse bag, gunny-sack, perforated bucket, or wire basket, attached to a rope and drawn back and forth in the water at the stem of a rowboat. Or an out-rigger may be arranged so as to drag two or more bags at the same time, thus cutting a wider swath. By rowing slowly along about loo lbs. can be thus dissolved in an hour. By using several boats quite a large reservoir can be covered in a working day. For a very large reservoir a motor laimch may be used. In making the trips the parallel paths of the boats should be about 20 ft. apart. Care must be taken not to row too slowly, as too great a con- centration may be obtained near the bags, and if fish should swim into this overdosed water they might be poisoned.
It is generally preferable to carry out the treatment on a day when the wind is blowing, so that the circulation of the water may more readily distribute the chemical. Advantage may be taken also of vertical convection currents. If the algae to be killed are near the surface the application should be made early in the day when the surface-water is warming and tending to become stratified; but if the algae are well scattered through the water it is better to make the application toward night. It will often be found best to row against the wind. A knowl- edge of the currents such as may be obtained from Chapter VII, will be an aid to judgment in this matter. It has been found difiicult to treat a frozen reservoir with copper sulphate, as the chemical does not diffuse readily, but precipitates at the bottom near the point of application. The solution of copper sulphate is heavier than water.
Nature of the Reaction. — Just how the copper sulphate acts in the destruction of algae it is difficult to say, involving as it does intricate problems of cytological chemistry. That
COPPER TREATMENT FOR ALGiE 253
copper exerts a toxic effect is, however, well known. Much interest is attached to the fate of the copper that is not involved in the reaction with the organisms, for manifestly not all of copper sulphate is so utilized. Does it remain in solution or is it deposited at the bottom of the reservoir, where it cannot possibly harm those who drink the water? Generally speak- ing the latter condition prevails.
The sulphate of copper reacts with caldimi bicarbonate, which is present to a greater or less extent in nearly all natural waters, to form sulphate of calcium and basic copper carbonate, some carbonic acid being liberated. The basic copper car- bonate may then become decomposed, copper hydrate and carbonic acid being formed. Copper hydrate is almost insoluble in water. Basic copper carbonate is somewhat soluble in water which contains carbonic acid, especially if the hardness of the water is low. Experiments have shown that in hard waters the reactions above mentioned take place in the course of a few hours, the copper hydrate first becoming a colloid and then precipitating as solid matter in suspension. In softer waters the reaction takes place more slowly. It seems probable, however, that the reduction of the carbonic acid brought about by the organisms themselves may hasten the reaction. The presence of organic matter in solution tends to retard it. The reaction is more rapid in warm than in cold water. The pre- cipitation of the copper hydrate is hastened by the presence of suspended matter. This is probably a physical action. These are all important matters, for Ihe quantity of copper sulphate required to remove the algae is closely related to the speed of the reaction.
The precipitated copper settles to the bottom and later may be recovered from the mud. Goodnough found that the mud in the reservoir at Arlington, Mass., contained as high as 0.3 per cent of copper. This precipitated copper, in the mud after it has ceased to be in a colloidal condition, does not appear to be objectionable.
Quantity of Copper Sulphate Required. — It is of great importance that just the right quantity of copper sulphate be
254 THE MICROSCOPY OF DRINKING WATER
used. If too little is applied the algsc will not be destroyed; if too much is used, there is danger that fish may be killed and there is also the money waste.
In deciding upon the quantity to be used several factors need to be considered, such as the kind of algae present, the amoimt of organic matter in the water, the hardness, the presence or absence of carbonic acid, the temperature, the kind of fish present, and of course the quantity of water to be treated. Some of these matters were considered in the preceding section.
It IS hazardous for one not familiar with the various matters involved to attempt to treat a water-supply with copper, as the effect of overdosing may produce disastrous results in the destruction of fish and other animal organisms. Of particular necessity is it to know what organisms are present that need to be killed. For this a microscopical examination is essential. Fortunately this is an easy matter for a water-works super- intcndant to determine. A simple equipment like that described in Chapter III and a general knowledge of the different organ- isms such as may be obtained from the plates at the end of this book should be sufficient to furnish the desired information.
Quantity Required to Eradicate Different Organisms. — Organisms (iiffcr considerably in their susceptibility to copper sulphate. Some of the blue-green alga? are destroyed by the application of only one part of copper sulphate in ten million parts of water, while other organisms require more than ten times as much as this, and some twenty times as much. One of the organisms most easily killed is Uroglena which can be eradicated by using as little as one part of copper' sulphate in twenty million parts of water.
It is probable that the stage of growth of the organisms is also a determining factor and that the presence or absence of carbonic acid is impt^rtant. Different observers have brought in different figures for the quantities that have proved efficacious with the same organisms. It is impossible to state any very definite figures for the quantities required, but the following figures chiefly given by Kellerman, one of the originators of the method, are believed to be as reliable as any.
COPPER TREATMENT FOR ALG^
255
QUANTITY OF COPPER SULPHATE REQUIRED FOR DIFFERENT
ORGANISMS.
Organisms.
Dialomacea
Astcrionella
Fragilaria
Melosira
Synedra
Navicula
Chlorophycea
Cladophora
Conferva
Hydrodictyon. . . Scenedesmus . . . .
Spirogyra
Ulothrix
Volvox
Zygnema
Microspora
Drapamaldia . . .
Raphidium
Coelastnim
Cyanophyce r:
Anabaena
Clathrocystis . . . Coelosphsrium. .
Oscillaria
Microcystis
Aphanizomenon .
Protozoa:
Euglena
Uroglena
Peridinium
Glenodinium. . . . Chlamydomonaa Cryptomonas . . . Mallomonas. . . .
Dinobryon
Synura
Schizomyceies'
Beggiatoa
Cladothrix
Crenothrix
Leptomitus . . . .
|
Parts per Million. |
Pounds per Million Gallons of Water. |
|
O.IO |
0.8 |
|
0.2S |
2.1 |
|
0.30 |
2.5 |
|
1. 00 |
8.3 |
|
0.07 |
0.6 |
|
1. 00 |
8.3 |
|
1. 00 |
8.3 |
|
0.10 |
0.8 |
|
0.30 |
2 5 |
|
0.20 |
1-7 |
|
0 20 |
1.7 |
|
0.25 |
2.1 |
|
0.70 |
5.8 |
|
0.40 |
3 3 |
|
1 0.30 |
25 |
|
1 0.30 |
25 |
|
0 30 |
2.5 |
|
1 O.IO |
0.8 |
|
O.IO |
0.8 |
|
0.30 |
25 |
|
0.20 |
17 |
|
0.20 |
17 |
|
o.iS |
1.2 |
|
0.50 |
4.2 |
|
0.0s |
0.4 |
|
2.00 |
16.6 |
|
0.50 |
4.2 |
|
0.50 |
42 |
|
0.50 |
4.2 |
|
0.50 |
42 |
|
0.30 |
2.5 |
|
O.IO |
0.8 |
|
• |
|
|
5 00 |
41-5 |
|
0.20 |
1.7 |
|
0.30 |
2.5 |
|
0.40 |
3 3 |
256 THE MICROSCOPY OF DRINKING WATER
The figures given may be assumed to apply at a temperature of 15° C. or 59° F. Moore and Kellerman state that these should be increased or decreased by about 2.5 per cent for each centigrade degree below or above 15° C.
They also state, though with less assurance, that an increase of 2 per cent should be made for each ten parts of organic matter per million and an increase of 0.5 to 5 per cent for each ten parts per million of alkalinity. A 5 per cent increase should be made if the amount of carbonic acid is small.
Calculating the Volume of Water to be Treated. — ^Usually the quantity of water to be treated is not known exactly, but has to be estimated. The following data will assist in making this estimate.
The problem is first to find the nimiber of million gallons of water in the reser\^oir. When this has been found, the total quantity of copper sulphate required is ascertained by multiply- ing this by the figure in the last column of the preceding table corresponding to the organism that is to be killed. This must then be increased or decreased slightly to take account of the other factors above mentioned.
One million gallons of water represents a depth of about 3 ft. over one acre. Hence the number of acres of water surface, multiplied by the average depth of the water divided by 3 gives approximately the number of million gallons of water in the reservoir. In an ordinary reserv^oir the average depth may he taken as about one-third of the maximum depth.
If the reservoir to be treated is so deep that the lower strata are stagnant the calculation should be made to include only the water above and within the transition zone. This involves a knowledge of the temperatures at different depths which may be obtained by the method described on page 86.
Safe Limit for Treating Water to Prevent Killing Fish.— Kellerman recommends that in order to prevent killing certain fish the following limits should be set to the amount of copper sulphate applied to water.
It will be seen that some of the amounts required for algaj destruction are critically near the amounts that will
COPPER TREATMENT FOR ALG^
257
kill fish. This explains^ the need of cautious application of this remedy.
|
Pish. |
Parts per Million. |
Pounds per Million Gallons (Approximate). |
|
Trout Carp |
0.14 0.30 0.30 0.40 0.40 0.50 0-7S 1.20 2.10 |
1.2 2.5 2-5 35 35 4.0 6.0 10. 0 17.0 |
|
Suckers Catfish Pickerel Goldfish Perch Sunfish Black bass . . . |
Secondary Growths of Organisms. — It not infrequently happens that after copper sulphate has been used to destroy a certain kind of algae, this growth is followed by a second growth of some other organism. Thus, following the destruc- tion of Anabaena a growth of diatoms may occur. Usually the second growth is an organism less susceptible to the influence of copper than the first, but sometimes the same species returns.
This raises the question as to whether organisms do not become accustomed to the chemical to such an extent that larger doses are required for subsequent treatment. WTiile some observations appear to indicate that this may be so, there is no reason to believe that it goes very far, or that it is a matter to be seriously reckoned with.
In dosing a reservoir it must not be forgotten that organ- isms sometimes become concentrated within the transition zone, and that these organisms may be carried up into the circulating waters by a high wind and cooler weather. Hence, watch should be kept of such growths, so that a subsequent treatment may be given if these organisms show signs of increase^
Increase of Bacteria after Copper Treatment. — A secondary efifect of the copper treatment is to increase the number of bacteria in the water. This has been observed so often that it may be considered as a universal phenomenon. The fol-
258
THE mCROSCOPy OF DRINKING WATER
lowing figures by Jackson illustrate this bacterial increase. They refer to one of the reservoirs of the water-supply of Brookl}ii that had been treated with copper to destroy a growth of Asterionella.
EFFIXT OF COPPER SULPHATE ON WATER BACTERIA AFTER A
REDUCTION OF ASTERIONELLA.
|
Date. |
Number per Cubic Centimeter. |
||
|
Micrnacopic Organisms. |
Bacteria. |
||
|
Miirch i^^ i()05 |
Hcfore treatment |
4625 |
40s |
|
U |
After •* |
3645 |
600 |
|
IS |
332s |
6fOOO |
|
|
i() |
1925 |
11,000 |
|
|
17 |
1850 |
12,000 |
|
|
18 |
I57S |
4S.OOO |
|
|
20 |
1350 |
100,000 |
|
|
21 |
900 |
440,000 |
|
|
22 |
350 |
630,000 |
|
|
23 |
350 |
310,000 |
|
|
24 |
400 |
107,000 |
|
|
25 |
3O0 |
80,000 |
|
|
26 |
300 |
64,000 |
|
|
27 |
(< ( (( |
270 |
50,000 |
|
• 28 |
150 |
37.000 |
|
|
2Q |
100 |
20,000 |
|
|
30 |
ICXD |
8,000 |
|
|
31 |
(X> |
3i5oo |
|
|
April I |
28 |
860 |
Sometimes the numbers of bacteria are even higher than those given in the table.
The bacterial growth may be alleviated by dosing the water with hj-pochlorite after the dosage with copper.
Subsequent Odors of Decomposition. — The decay of the alga) after they have been killed sometimes causes a temporary increase in the odor of the w^ater. This is usually of short duration and sometimes it does not occur at all.
Copper Sulphate as a Disinfectant. — Copper sulphate will destroy bacteria' if a sufficient quantity is used. The amount required is considerably greater than that needed to destroy alga}. For killing bacteria copper sulphate is less efficient than hjpochlorites or liquid chlorine.
COPPER TREATMENT FOR ALGiE 259
The St Thomas Experience. — An interesting after-effect of the use of copper sulphate occurred at St. Thomas Ontario. There the destruction of the algae in the reservoir deprived of its food-supply the pipe moss which had been growing lux- uriantly in some of the main pipes. Consequently these pipe-dwelling organisms died and decayed, causing foul odors in the water as it left the service taps.
Treatment of Water Prior to Filtration. — One of the situa- tions where the use of copper sulphate has proved of much use is when the water in an algae-laden reservoir is applied to a filter. Such growths tend to clog both sand and mechanical filters, reducing the yield of the filter and increasing the loss of head and, in the case of mechanical filters, the quantity of wash water required. Interesting examples of this are the mechanical filter plants at Cincinnati and Louisville on the Ohio River, and at the sand filter at Wilmington, Del.
The Proper Function of the Copper Treatment. — The use of copper sulphate for protecting a water-supply against algae troubles should not be regarded as a permanent remedy or one that is to be continuously used. Rather it is a palliative, to be used under exceptional conditions — a very valuable adjunct to our other methods of purifying water.
The question often comes up as to whether copper sulphate may be used in a reservoir from which the water must flow to the consumers almost immediately after treatment. This is usually unwise, as the decaying organisms would be carried into the pipes. If the algae conditions are so serious as to warrant its use in such a situation the consumers should be warned not to drink the water for several days. If this is done and the copper treatment followed by disinfection with hypo- chlorites there seems to be no hygienic objection to it.
The copper treatment has been widely used in all parts of the world, and nearly all sanitarians and water-works engineers approve of its intelligent use.
Creosote Treatment for Algae Growths. — Mr. Wm. F. Wilcox, of Meridian, Miss., has stated that the application of creosote to the water in his reservoir in 1910 destroyed the algae. The
260 THE MICROSCOPY OF DRINKING WATER
quantity used was one gallon per acre of water surface, which was equivalent to about 0.5 part per million. The method has not been used elsewhere, so far as the author knows.
Hypochlorite Treatment for Algae. — ^Algae may be killed by the use of hypochlorite, but just as this substance is better than copper sulphate for bacterial disinfection so the copper treatment is generally better than hypochlorites for the destruc- tion of algae.
By-passes. — It often happens that a water-works system is so arranged that a reservoir can be cut out of service if the water in it becomes affected with growths of algae. When a reservoir is thus allowed to remain standing the organisms sometimes disappear in the course of a short time. This can- not always be depended upon. Reservoirs thus isolated some- times remain in a foul condition for many months. In case an open reservoir is used for the storage of ground-water, it should be provided with a by-pass in order that this method of isolation may be resorted to in case of need.
The by-pass around the Ridgewood reservoir in Brooklyn, was of great service, prior to the use of copper sulphate. The by-pass also gives opportunity for the reservoir to be shut off while the copper treatment is being given, thus avoiding the temporary unpleasant effects due to the decomposition of the algae.
CHAPTER XVII PURIFICATION OF WATER CONTAINING ALGJE
The keynote of success in purifying water which contains algae is aeraiion. By this is meant the exposure of water to the air in thin films, in drops or as a fine spray. The object is to provide opportunity for an interchange of gases between the water and the air, so that oxygen may be dissolved and car- bonic acid and odoriferous gases, such as sulphureted hydro- gen and the like, may be liberated. Aeration alone sometimes greatly improves the quality of water which has a bad taste and odor caused by algae, but usually it is to be regarded as an adjunct to filtration; for while aera- tion may reduce the odor it does not remove the organisms themselves.
The aeration of water has been practised for many years. At one time it was thought to improve the hygienic condition of the water, but bacteriological studies have shown that the bacteria are not destroyed to any extent by the process. One of the early instances of the application of aeration was in the reservoirs of the Hackensack Water Company in New Jersey, where air was blown in through perforated pipes placed near the bottom. It is said to have produced beneficial results, but, as applied, it was a one-sided process. Oxygen was forced in, but there was very little opportunity for carbonic acid or odoriferous gases to be liberated. The natural aeration that occurs when water flows down the rocky bed of a brook or over water-falls has been repeatedly found to be of benefit in reducing odors. The mechanical agitation tends to disinte-
261
262
THE MICROSCOPY OF DRINKING WATER
grate the organisms, the repeated exposure of the water to the air liberates the odoriferous substances, and the absorption of air pro\ides oxygen for oxidation processes. A similar disintegration of the organisms may take place in the pipes of a distribution system, but in this case there is no chance for the odoriferous substances to be lost, and the disintegration of the organisms, may only intensify the odor of the water.
Experiments on Aeration. — In 1907 some experiments were made by the author, assisted by Mr. Melville C. Whipple, at the Polytechnic Institute of Brooklyn, N. Y., for Messrs. Hazen and Fuller in connection with their report to the New York Board of Water Supply. Deaerated water was exposed to the air in various receptacles and by causing it to fall through the air as drops, and the rate of oxygen absorption deter- mined. Water containing carbonic acid was similarly tested and the rate of decarbonation ascertained. Water charged with sulphureted hydrogen, oil of peppermint and other essential oils were also used. Some of the results of these experiments were published in the Journal of the New England Water Works Association, 1913, Vol. XXVII, No. 2, p. 193.
In brief it was found that an exposure of water to the air in drops for a period of one second would increase the dissolved oxygen from o per cent up to about 75 per cent of saturation, and an exposure of two seconds would increase it to about 90 per cent.
Carbonic acid was reduced after exposure in drops, as shown by the following figures, which give the quantity left in solution after different intervals of time.
CARBONIC ACID LKFF IN SOLUTION AFTER AERATION
Al the si an
After 0.5 seeond
I
2
t <
< <
< ( it
IS
( < < (
|
c |
nr\ |
>onic Aci 10.0 |
(1 (Parts |
per Million |
). |
||
|
50 |
25.0 |
50.0 |
|||||
|
41 |
1>A) |
138 |
2.?. 4 |
||||
|
3-5 |
5-.? |
9-3 |
14.0 |
||||
|
.^ 0 |
41 |
0.2 |
ii-5 |
||||
|
'^•5 |
:^o |
.^« |
4 5 |
||||
|
2. 1 |
2. I |
2. I |
2.1 |
PURIFICATION OF WATER CONTAINING ALG^ 263^
Sulphureted hydrogen was reduced as follows:
SULPIIURETED HYDROGEN AFTER AERATION
|
Time. |
Sulphureted Hydrogen. (Parts per Million.) |
Odor. |
|
At start |
15-2 I0.2 2.6 |
Faint Very faint Very faint None J |
|
After I second. . . . After 1 . 5 seconds. . After 2 . o seconds. . |
The oil of peppermmt gave a distinct odor when diluted in water to the extent of one in one million; and could be detected when diluted to one in fifty million. On exposure to the air in drops the odors decreased as follows:
ODOR AFTER AERATION
At start
After I second. After I . s seconds. After 2.0 seconds.
Odor of Peppermint.
Distinct Distinct Distinct Faint
2
Faint Faint Very faint None
3 Very faint
Very faint
None
None
Natural Aeration by Falling over a Dam. — Forbes and Richardson in their studies of the Illinois River have shown that at the Marseilles Dam in July and August, 191 1, the dis- solved oxygen increased from OJ64 to 2.94 parts per million, or four and a half times, during the fall. In winter, when the volume of water was larger, the increase was only 18 percent, namely from 7.35 to 8.65 parts per million. The carbonic acid during the summer decreased from 8.2 to 6.48 parts per million.
Aerating Fountains. — At Rochester, N. Y., West Point and many other places that might be named, the water entering the reservoir has been allowed to flow through an upturned nozzle so as to produce a fountain. This is often productive of substantial benefit to the water. An example of an aerat- ing foimtain is shown in Fig. 62, which represents the manner in which the stagnant water at the bottom of one of the reser-
261 TlIK MICROSCOPY OF DRINKING WATER
PURIFICATION OF WATER CONTAINING ALG^ 265
voire of the Croton supply is oxygenated as it is discharged into the stream below the dam. The ferrous iron which the water contains is oxidized in this way, and the resulting ferric hydrate becomes deposited on the stones in the stream to such an extent as to color them brownish-red.
The frontispiece shows the aerating fountain at the West Parish filter of the water-supply of Springfield, Mass., which was constructed in 1909, the Consulting Engineers being Hazen and Whipple and the Chief Engineer being Mr. Elbert E. Lochridge, to whom the author is indebted for the photograph. If this fountain be compared with the jet shown in Fig. 62, the advantage of the multiple outlet will be evident.
Another example of aeration is at the filter plant at Albany, N. Y. designed by Allen Hazen in 1899. This serves to eliminate odors from the polluted water of the Hudson River and also to remove carbonic acid, thus helping to prevent growths of organisms in the settling basin into which the aerated water is discharged.
Aerating fountains are capable of artistic treatment and they always add to the attractive appearance of a reservoir. The enjoyment of watching falling water seems to be instinctive. The effect of aeration in liberating odors from water is often shown by the odors which pervade the air in the \acinity of fountains, when the water contains algae. Even the spray at Niagara Falls at times has an odor of decomposition due in part to the sewage pollution which the river receives at Buffalo and elsewhere.
Aerating Nozzles. — ^The use of aerating nozzles and other devices for oxidizing sewage in connection with percolating filtere, or sprinkling filters, seems likely to cause a decided advance in the art of aerating water. Fig. 65 shows the aeration of sewage at Baltimore, Md. Sprays of a new design have been put in operation at the Kensico supply of the New York supply. They are of interest as they involve the use of a rifled nozzle, which gives a whirling motion to the discharged spray. This aerator is shown in Figs. 67 and 68. A much larger plant of this kind is to be used for the new Catskill supply.
266 TUJi JUCKOiSUOPV OK UK1.MU.NU WATER
Fig. 63.— Spillway o{ Ihc Croton Dam, Showing Natural Aeration."
Fic. 64. — Aeralors at the Albany Flllratton Plant. Designed by Allen Hazen.
TUK UICROSCOPY OF DRINKING WATKK
Fic. 67.— Aerator at Rye Pond. Borough of the Bronx, New York City.
Fig. 68.— .Aerator at Rye Pond. Borough of the Bronx, New York City.
PURIFICATION OP WATER CONTAINING ALG^ 269
by Percolation. — ^Aeration is much used in connec- tion with the removal of iron from public water-supplies. A common method is to allow the water to trickle slowly down- ward through porous beds — such as broken stone, coke, shav- ings— or to fall through perforated plates. These methods serve to retard the flow of the divided water, so as to give a longer period of exposure of the water to the air. When these methods are used it is important to have the beds them- selves well ventilated.
Filtration of Water Containing Small Numbers of Algae. — When water contains few algae it may be filtered by either sand filtration or mechanical filtration. Usually the choice of method is determined by other considerations than the presence of organisms, except T/vhen the amount of algae is large. In both systems the presence of organisms tends to clog the filters and increase the loss of lead.
Growth of Algae on Open Sand Filters. — ^When water is- filtered through open sand filters where the sand surface is always covered with water, as in continuous filtration, algae grow upon the sand surface. That this is a growth and not a mere accmnulation was shown by some experiments made by the author many years ago at Chestnut Hill reservoir.
An experimental filter became so clogged after running for 25 days that it was necessary to scrape the surface of the sand. Microscopical examinations showed that over each square centimeter there were 2,500,000 Tabellaria and 1,000,000 Synedra, besides many other microscopic organisms. Calcula- tions from the analyses of the raw water showed that during the 25 days when the filter had been in operation only 150,000- Tabellaria and 20,000 Synedra were removed from the water by each square centimeter of the filter. The difference between the two sets of figures represents the growth of organisms upon the sand. Samples of scum taken from various filters in practical operation have shown the presence of microscopic organisms in numbers which range from a few thousand to several million per square centimeter of surface area. The presence of these organisms aids filtration in a certain sense
270 THE MICROSCOPY OF DRINKING WATER
by forming a tenacious surface scum over the sand. This schmutzdecke, however, forms even without their presence, and accumulations of organisms above the sand are, on the whole, likely to do more harm than good. They cause the filter to clog more quickly than it otherwise would, and, there- fore, increase the cost of operation. Furthermore, when open filters are used these algx growths sometimes interfere with filtration in another way. When their growth is vigorous the amount of gas liberated from them sometimes becomes so great that masses of the organisms are lifted from the sand layer and floated to the surface. Spots of sand are, therefore, left uncovered, and the water filters through them, more rapidly than it should, with the result that filtration is imperfect. It seems probable, also, that decomposition of the organisms at the surface affects the filtered water unfavorably. When filters are covered with roofs these organisms do not grow on the sand surface and those which are found there represent acciunula- tions from the raw water.
Kemna's Studies at Antwerp. — Dr. Ad. Kemna made sys- tematic studies of the algaj found in the schmutzdecke everj' time a filter bed at Hamburg was scraped. A summary of these may be found in a discussion by the author in the Transactions of the Am. Soc. C.E. Vol. XLIII, p. 318, from which the following is quoted.
The organisms which develop over the surface of a sand filter may be grouped, for practical purposes, into three classes: those which form a matting upon the sand; those which are attached to the sand but extend upward in filaments or sheets; and those which are free-floating in the water. Perhaps it would be better to say that the organisms are found in these three conditions, because the same organism is sometimes found now on the sand and now al)()ve it.
The effects of these three groups of organisms upon the operation of the filter are not the same. The most important effect is that produced by those organisms which form a matting upon the sand. The diatoms and the unicellular algae are here chiefly concerned. By their growth they form a more or less
PURIFICATION OF WATER CONTAINING ALG.E 271
gelatinous film upon the surface, and as this fibn becomes denser, the rate of filtration is retarded until finally it becomes necessary to scrape the filter. The algaj which grow erect upon the sand do not thus clog the filter. On the contrary, they prevent clogging to some extent Their waving, interlaced threads act as a sort of preliminary strainer, removing from the applied water some of the suspended matter which would otherwise collect on the sand. This action continues as long as the plants are in good condition and as long as the evolution of gas is sufficient to cause flotation. When they begin to decay or when they become overloaded with foreign matter they settle to the bottom and help to clog the filter. Kemna found that at Antwerp Hydrodictyon was the most effective organism in this process of preliminary straining. The free-floating forms have little influence on the rate of filtration as long as they remain in suspension, although, to some extent, they too play a part in the preliminary clarifying process. But ultimately most of them reach the surface of the sand and help to clog the filter.
During the course of the year the character of the flora changes. This change is often gradual, but at times is very rapid. Kemna has noticed that at the time when certain organisms are rapidly disappearing from the sand the efficiency of filtration is imparled. He attributes this to the changed condition of the surface film caused by the decomposition of the organisms, but suggests that changes in the bacterial flora may also play an important part. In a recent publica- tion he cites the following interesting experience with Anabxna:
During the hot weather of July, 1899, Anabaina became abnndant over some of the Antwerp filter beds. Knowing the character of this organism and its tendency to impart an odor to the water, he kept a careful watch of the filters, collecting samples of the filtered water twice a day and testing them as to their odor and the amount of ammonia they contained. As long as the Anabaina remained in a living condition in the water over the sand, the filtered water was satisfactory, but when the organisms disappeared, on the advent of cold weather, the
272 THE MICROSCOPY OF DRINKING WATER
filtered water acquired a bad taste and the amount of ammonia increased.
The studies made at Hamburg and at Antwerp show, with apparent conclusiveness, . that when the vegetation over a sand filter is in a living condition, it is a positive aid to the efficiency of filtration, though it increases the cost of operation. Most of the microscopic organisms have a coating which is some- what gelatinous, and in many cases the gelatinous material is very abundant. The diatoms and other organisms which grow directly on the sand aid in the formation of the surface film on which the efficiency of filtration largely, but not solely, depends. This fact has been understood for many years. The surface film forms through bacterial agency on covered filters as well as on open filters, but on the latter its formation is assisted by the microscopic organisms.
Examination of Filter Scum. — As an example of the number of organisms that may be found upon the surface of an open sand filter, the following table is taken from the records of an experimental filter at Boston, Mass. The sample was col- lected in March after the filter had been in operation two months.
Number of Orsaniimi over I Sq. Cm. of Sand. (In Standard Units.*)
Diaiamacea:
AstcrioncIIa 278,000
Cymbclla 130,000
Diatoma 150,000
Melosira 10,000
Mcridion 25,000
NaviruKi 7»700
Stcphanodiscus 6,500
Synwira 1,100,000
Tabellaria 2,390,000
Chlorophycea:
Clostcrium 1,200
Scencdcsmus 800
Protococcus 60,500 '
Conferva 12,000
Spirogyra 5,500
* One standard unit equals 400 square microns.
PURIFICATION OF WATER CONTAINING ALGiB 273
Cy<mopkycea:
Chro6coccus 5>30o
Osdllaria ' 84^000
Protozoa:
Trachelomonas 16,000
Ciliata S,ooo
Peridinium 4)Ooo
Tintinnus 14,000
Mallomonas 800
Synura 6,000
Codonella " 400
Rotifera:
Annuraea 800
Polyarthra 1,000
Synchaeta 8,000
Total organisms 4,324,500
Amorphous matter 2^00,000
Crenothriz Growths in Sand Filters. — ^Where water is filtered through sand filters and there is a deficiency of oxygen by reason of the presence of too much organic matter under- going decomposition, it often happens that iron is reduced within the filter, going into solution and appearing in the effluent. Under these conditions growths of Crenothrix often occur in the underdrains and may even produce clogging by their vigorous development.
Filtration of Water Containing Large Numbers of Algss. — Where the algae growth in water is excessive it is impossible to satisfactorily filter the water by the ordinary methods. Aeration is a necessity. Sometimes it has to be used not only before, but after filtration in order to keep the oxygen from becoming exhausted. In fact sometimes the quantity of algSB is so great that the oxygen will be exhausted before the water has had a chance to reach the bottom of the sand bed.
In this case continuous filtration becomes impracticable and intermittent filtration necessary. The latter method is that which has been used so commonly for sewage purification.
The Ludlow Filter. — Perhaps the best illustration of inter- mittent filtration applied to the purification of water contain-
274 THE MICROSCOPY OF DRINKING WATEB
ing algae was the Ludlow filter at Springfield, Mass., designed in 1905. A description of this filter may be found in the journal of the New England Water Works Association for 1907, Vol. XXI, p. 279.
This filter was built cheaply for temporary service by leveling a mound of sand, so as to obtain a flat area of four acres. This was divided into four beds enclosed by earth embankments. The water was pumped from the reservoir to an aerator in the center of the plant, from which it was intermittently applied to the different beds. Tiles 6 in. and 8 in. in diameter were laid 12I ft. apart, to scr\T as underdrains. The sand was 5 ft. deep and had an effective size of 0.30 mm. The aerator shown in Fig. 66, was a novel feature of the plant. TTie filtered water was further aerated by falling from the small drains into a large drain and thence into a wooden flume.
This filter did good ser\-ice for several years and until the supply was abandoned for the new supply from the Little River.
Double Filtration for Water Containing Algss. — Double filtration was tried experimentally at Springfield by the Massachusetts State Board of Health before the Ludlow filter was built. The results of these experiments were summed up in the chemist's report as follows:
*^ Summarizing the discussions upon this point given upon previous pages, it has been found that practically all p)ositive odors were removed by single filtration except during the period of high numbers of Anabxna and fermentation of organic mat- ter in the reservoir. During this period single filtration through sand filters at rates of 2,500,000 and 5,000,000 gallons per acre daily failed to remove the odors, but double filtration^ even with the secondary filter operating at a rate of 10,000,000 gallons per acre daily, was entirely successful in removing all odors remaining in the water that had passed through the primary filter, although this i)rimary filter was poorly operated at this time. This result was aided by the aeration of the water before passing to the surface of the secondary filter."
Double filtration with liberal aeration has also been used
PURIFICATION OF WATER CONTAINING ALG^ 276
for treating waters of this class, notably at South Norwalk, Conn., and at Mt. Desert, Me. H. W. Clark, the Chem- ist of the Massachusetts State Board of Health was the designer of both plants.
Copper Treatment Prior to FUtratioa. This subject is discussed in Chapter XVI.
House Filters.— The use of house filters at the faucet for removing microscopic organisms is quite common. Some of these filters give reason- ably satisfactory results if properly cared for, but generally their use is not to be recommended for sanitary reasons. Por- celain or stone filters, such as the Gate City filter, the Pasteur filter and the Berkefcld filter, remove the microscopic organisms completely, but they do not remove all of the odors produced by them. They also im- prove the sanitary qual- ity of the water, but they clog rapidly and yield but little water.
Fic. 69, — Ncwcomb Filter for Purifying Water for tbc Household. A filter [){ Ihis type, combining aeration and decolor Lzu Lion with charcoal, was much axd at S[>ringfie1d, Mass., in the days of the old Ludlow supply.
276 THE MICROSCOPY OF DRINKINO WATER
Charcoal filters remove the odor as well as the oiganisms, but for sanitary reasons they are more objectionable than the other types. In certain cases the use of sand and charcoal with liberal aeration of the water gives reasonably satisfactory results. The Newcomb filter has been used at Springfield with satisfactory results. A filter of this type can be made by any- one who has any ingenuity. In general, however, methods of house filtration prove expensive and disappointing.
CHAPTER XVin
GROWTH OF ORGANISMS IN WATER-PIPES
The reactions between the water and the water-pipes of a water-works system involve principally such matters as iron-rusting, tuberculation, lead-poisoning, and others of a chemic?' and physical nature, but there are also biological
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reactions. These may be considered under two heads: (i) the effect of the aqueducts and pipes upon the water, and (2) the effect of the water upon the organisms on the walls of the aqueducts and pipes.
Temperature Changes in Distribution Pipes. — The temper- ature of water changes during its passage through the pipes of a distribution system. The nature of these changes is shown by Fig. 70, where the curves represent the averages of weekly tem- perature observations for five years at Chestnut Hill reservoir and at two taps, one at Park Square, 5 miles from the reservoir and the other at Mattapan, 11 miles from the reservoir. Dur-
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Keductkoi of Organisms in P^^es. — Simples liken at the sajT.e plicte str.t i: Lz-i-j^ite i^it ch.^r.ges liuit tike place in the ori'ir.Lrr^.r of the wii^r d-e to their pissice through the ;/:y-^. \Vv'_i:!v f.Vr<;r/:i:I:r.? ::r £vt veitrs :Sc:-> showed i:,t Vjijy^'ii.g uvjri::'j r.ur-.bir :: omrisnis present:
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The ^'realcv-l rcluelion did not occur near the reser\'oirs, where tlie pijKS v,'cre large and the currents si^'ilt and constant, but at ihe exlrrrvitic- ■:' the d:>iribution svstem, where the j^ij/';- v.< re -zr.ji.xr and where during the night the velocities v.f r*- r'-'l:^ •■'!.
'Ihe- '.b-ervali'.n- showed th.it during the \i"inter, when th'.re v.ere c'jnjparalivclv few ort:ani>ms in the water, the redn^lion in llie \)\\K'Ti wa.s much less than during the summer, when or;^ani.-n")s were more abundant. During the six months of the year, fn^m Xrjvember tu April, there was a reduction of .\.\ j>er cent in organisms and 24 per cent in amorphous matter in about 6 miles of pijie; while during the sLx months from May to October the reduction was 62 per cent for the organisms anri 5 .; |>er cent for the amorphous matter. It is worth noting that the reduction in organisms was greater than the reduction in amorphous matter.
Not only are the microscopic organisms and amorphous matter reduc(;d in the pipes, but the bacteria also tend to decrease. This fact has be<"n observed in many cities. In the pipes of the Boston Water Works the decrease does not occur throughout the entire year. In the summer, when the
GROWTH OF ORGANISMS IN WATER PIPES
279
temperature of the water is high and when the organisms in the water and those growing in the pipes are passing rapidly through stages of growth and decay, there is a considerable increase. This- is shown in Fig. 71.
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In order to determine what organisms showed the greatest reduction in the pipes, a detailed study of the examinations above referred to was made for the years 1S92 and 1893. The following were the results:
PERCENTAGE REDUCTION OE .MICROSCOPIC ORGANISMS IN THE DISTRIBUTION- PIPES BETWICEN I'ARK SQUARIC AND MATTAPAN, BOSTON, M;\SS.
DiatoRuccx jS jicr tent,
Chlorophycen; 57 " "
CyarniiihyccEC 54 " "
Protozoa (u " "
Miscellaneous 5S " "
Oiganisms of all kinds 56 " "
280 THE MICROSCOPY OF DRINKING WATER
Cause of Reduction of Organisms in Pipes. — Questions
naturally arise as to the cause and efifect of this reduction of organisms in the pipes. They may be considered imder the following topics: sedimentation, disintegration, decomposi- tion, and consumption by other organisms.
Most of the microscopic organisms are heavier than water. Some always settle in quiet water, and they do so in the pipes whenever the current is reduced to a certain point. Others, which in ponds usually rise to the surface on account of the gas bubbles which they contain, will settle in the pipes when the pressure of the water has deprived them of their gas. In dead ends the organisms and particles of amorphous matter often accumulate and form deposits upon the bottom of the pipes. They also tend to deposit on up-grades. It is a matter of frequent observation that the water from the high points of a distribution system contains fewer organisms than that from the low points. The same fact has been observed in high buildings, where the difference between the water on the upper stories and that on the lower floor is often considerable.
The colors of the organisms often change in the pipes of a distribution system. For example the color of Tabellaria and other diatoms may be yellowish-brown in the reservoir but greenish-brown in the pipes.
Many of the common organisms are very fragile. Even a slight agitation of the water will break them up. This is particularly true of certain Protozoa, but it also happens to the siliceous cells of diatoms.
The organisms found in surface-waters are accustomed to live in the light. When they enter the dark pipes they are liable to die and decompose. This is particularly true of some of the organisms that are abundant in the summer. Microscopical examination of samples from the service-taps has often revealed organisms in a decomposing condition, swarming with bacteria. This decomposition tends to reduce the numbers of organisms in the pipes.
Another important consideration in the reduction of organ- isms is the fact that in many of the distribution systems where
GROWTH OF ORGANISMS IN WATER-PIPES 281
surface-waters are used the pipes are covered with growths of sponge, etc. These attached growths depend for their food- material upon the minute organisms found in the water. If the growths are abundant, the removal of organisms from the water by this means may be considerable.
Pipe Moss. — Comparatively little has been written in this coimtry upon the biology of aqueducts and pipes. Our atten- tion has been called to growths of Crenothrix and of fresh-water sponge, but no attempt has been made to give an accurate account of the organisms infesting the distribution systems of our water-supplies. In Europe, however, the subject has been considered to some extent.
In the city of Hamburg the minute animals inhabiting water-pipes were studied by Hartwig Petersen in 1876. Ten years later Karl Kraepelin made a more extended study. His observations were of much interest. He found an animal growth, often more than one centimeter thick, covering the entire surface of the pipes. The composition of this growth varied in different places. He gave a list of sixty different species observed. In many places the walls of the pipes were covered with fresh-water sponges, chiefly Spongilla fluviatilis and Spongilla lacustris. Mollusks were conspicuous, espe- cially the mussel, Dreyssena polymorpha. Snails were also numerous. Hundreds of " water-lice " (Asellus aquaticus) and " water-crabs " (Gammarus pulex) were found at every examination. The material known as " pipe-moss " was conmion, and consisted largely of Cordylophora lacustris and the Bryozoa, PlumatcUa and Paludicella.
The Rotterdam "Water Calamity." — ^At the time when Crenothrix was giving so much trouble at Rotterdam, Hugo de Vries made an extended study of the animak and plants found in the water-pipes of that city. His observations were confined chiefly to the pipes and canals which conveyed the unfiltered water of the river Maas to the filter beds. In speaking of one of the canals he said : " The walls were thickly covered with living organisms up to the water-level. They formed an almost continuous coating of varying composition.
282 THE MICROSCOPY OF DRINKING WATER
There were only one or two exceptions to this. In one place, where the water came from the pumps with great velocity, the walls were free from living organisms; and in another place, where there was almost no current, only one living form was seen. There w^as a section of one of the canals, where a gentle current was flowing, that was a magnificent aquarium. The walls were evcrj-where covered with white tufts of fresh-water sponge, Spongilla fluviatilis. Many of these tufts reached a diameter of 6 or 8 inches, but most of them were somewhat smaller. Between the sponge patches were seated coimtless numbers of the mussel, Drcyssean polj-morpha. Individuals old and young were often seen grouped together in colonies which sometimes extended completely over the sponges. But what most of all attracted attention was a luxuriant growth of the ' horn-polyp,' Cordylophora lacustris. It covered the mussel-shells and occupied all the space between the sponges. The stalks reached a length of an inch or more. On and between the Cordylophora swarmed countless niunbers of Vorticclla, Acincta, and other Protozoa and Rotifera. These organisms had no lack of food-material, and the absence of light protected them from many foes which, in the light, thin out their ranks. Over all these animals Crenothrix was found growing in abundance. The shells of the mussels and the stems of the ' horn-polyps ' were coated with a thick felt- like layer of these ' iron-bacteria.' In other localities in the pipes the place of the ' horn-pohps ' was occupied by the Bryozoa, or ' Moss-animalcules.' All of these branching forms were spoken of collectively by the workmen as ' pipe-moss.' "
Boston Experience. — In the summer of 1896, when the pipes of the Metropolitan Water Works were being laid in Beacon Street, Boston, near the Chestnut Hill reser\'oir, a 16-inch main leading from the Fisher Hill reser\'oir to the Brighton district was opened. This afforded an opportunity to examine the material on the inside of a pipe that had been laid ten years. Inspection showed that besitles the usual coating of iron-rust tubercles, etc., there were numerous patches of fresh-water sponge, both Spongilla and Meyenia, brownish or almost white
GROWTH OF ORGANISMS IN WATER-PIPES 283
in color, and about the size of the pahn of one's hand. What was most conspicuous, however, was a sort of brown matting which covered much larger areas, and which had a thickness of about i inch. It had a very rough surface and, when dried,
•
reminded one of a piece of coarse burlap. This proved to be an animal form belonging to the Bryozoa, known as Fredericella. As fragments of it had several times before been observed in the water from the service-taps, and as it had been seen growing in some small pipes connected with the filtration experiments at the Chestnut Hill reservoir, more extended observations were made in different parts of the distribution system.
These brought out the fact that sponges and the Bryozoa were well established in the pipes. Many other organisms were also observed. In some places almost pure cultures of Stentor and Zoothamnium were found. At other points hosts of different organisms were seen, such as snails, mussels. Hydra, Nais, and Anguillula, Acineta, Vorticella, Arcella, Amoeba, coimtless niunbers of ciliated infusoria, and many other forms. The growths were distinctly animal in their nature, but in many places parasitic vegetable forms, such as Achlya, Crenothrix, Leptothrix, etc., were common. The most important class of organisms found, however, was the Bryozoa, of which Fredericella and Plimiatella were the chief representatives.
Food-supply of Pipe-moss. — The fact that the organisms that dwell in water-pipes depend for their food-material upon the algae, protozoa, bacteria, etc., contained in the water may be easily demonstrated by experiment. Specimens of Frederi- cella and Plumatella were once placed in a series of jars, some of which were supplied with water rich in its microscopic con- tents, while others were supplied with the same water after filtration. All the jars were kept in semi-darkness at the same temperature, and were examined daily. The Fredericella and Plumatella that had been supplied with filtered water soon began to die, while those in the other jars lived as long as the experiment was continued. Some of the same Bryozoa were placed in jars furnished with water from the Newton supply,
284 THE MICROSCOPY OF DRINKING WATER
a ground-water almost free from microscopic organisms, and after about a week they died for want of food. Dr. G. H. Parker of Harvard University once made a similar experiment on fresh-water sponge, and obtained the same result. With these facts established, we may confidently affirm that fresh- water sponge, Bryozoa, and similar pipe-dwellers will be absent from water-pipes where ground-water or water that has been eflFectively filtered is used.
Effect of Growths of Organisms in P^s. — One naturally asks, " What is the effect of these organisms growing in the pipes?" In a certain sense they tend to improve the quality of the water, by reducing the number of floating microscopic organisms; but they themselves must in time decay, and any one whose nose has ever had an experience with decomposing sponge will appreciate the fact that better places for these organisms may be found than the distribution systems of our water-supplies. It should be stated, however, that in all probability very large quantities would be required to produce tastes or odors that would be noticed in the water. Perhaps the greatest objection to their presence is the fact that they tend to Impede the flow of water in the pipes. When one considers that a coating \ inch thick diminishes the area of the cross-section of a 24-inch pipe by 4 per cent, and of a 6-inch pipe by 15 per cent, and when one learns that these organisms often form layers even thicker than this, it will be seen that such growths are matters of no little importance. Further- more, fingers of the fresh-water sponge sometimes extend several inches into the water, and the matting of the Bryozoa is always rough on account of the stiff branches that are extended in order that the organisms may secure their food. This roughness of the surface materially increases the friction of the pipe by a considerable but indefinite amount.
Organisms growing on the inner walls of water-pipes tend to promote tuberculation. This takes place in the following man- ner: Between the organisms and the walls of the pipe there is a layer of water from which the oxygen is at times temporarily exhausted and in which carbonic acid is abundant, these condi-
GROWTH OF ORGANISMS IN WATER-PIPES 285
tions being brought about by the organisms. If the organisms are torn away the pipe-coating may be removed and a little spot of iron thus exposed to the action of the carbonic acid. Corrosion thus begins and iron oxide becomes deposited in crystalline form around this spot, forming what is known as a tubercle. These tubercles greatly increase the roughness of the pipe and consequently retard the flow of water.
Experience with Pipe Moss in Brookljrn.— An interesting experience with pipe moss is on record at the Brooklyn Water Department. In November, 1897, the water in the Mt. Pros- pect reservoir became so filled with Asterionella that it was deemed advisable to shut off the reservoir and pump directly into the pipes. This action was followed by the appearance of brown fibrous masses in the tap-water. In a number of instances this fibrous matting stopped up the taps, and even large pipes were choked. The water at the same time had a distinctly moldy and unpleasant odor. The fibrous matting proved to be Paludicella. It had been growing on the inner walls of the pipes, and the change of currents and the pulsations of the pump, due to the direct pumping into the pipes, had dis- lodged it. Systematic and thorough flushing of the pipes materially improved the conditions.
PART II
CHAPTER XIX CLASSIFICATION OF THE MICROSCOPIC ORGANISMS
The microscopic organisms found in drinking water include the lowest forms of life. Some of them belong to the vegetable kingdom, some belong to the animal kingdom, while others possess characteristics that pertain to both. There is in reality no shar^) dividing-line between the vegetal and the animal in the low forms of life. Nature's boundaries are always shaded on both sides.
Classification. — Classification of organisms into groups is necessary, but it must be borne in mind that all classifications are artificial and subject to change. The one outlined below and used throughout this volume is believed to be the most convenient for the work at hand. Several groups, not per- taining to the microscopical examination of drinking water, are omitted.
Classification of the Microscopic Organisms
Plants
DiATOMACE.E. Alg.e (in the narrower sense).
Sciiizopii YCE^. ChlorophycecB,
Schizomycctcs. Fungi.
Cyanophycccc. Various Higher Plants.
286
CLASSIFICATION OF THE MICROSCOPIC ORGANISMS 287
Animals
Protozoa. Crustacea.
Rhizopoda. Eniomostraca.
Mastigophara {FlageUata) . Bryozoa (Polyzoa). InJusdHa (in the narrower Spongid^. sense).
Various Higher Animals.
ROTIFERA.
Conflict of Terminology. — ^The word " Algae " is used so much and is so often applied to all growths of microscopic organisms, whatever their place in nature, that special mention should be made of its true limitations.
AlgsB are flowerless plants of simple cellular structure, without mycelia, roots, stems, or leaves. The fimctions of ' the plants are centered in the individual cells, and only to a limited extent is there any " division of labor " among the cells. Prof. G. S. West, in his excellent treatise on the British Fresh Water Algae describes them as follows:
Alge. — ^Algae are Thallophytes of a simple or complex structure, and are of a green, yellow-green, blue-green, red or brown color. Most of them live entirely submerged in water and the major portion of them inhabit the sea. They are foxmd floating freely at the surface, attached to stones, or as in a large number of the fresh-water forms, adhering in gelatinous masses to the submerged portions of more highly organized aquatic plants. A few prefer damp situations in which they do not become immersed at all, or only periodically become covered with water.
They are mainly distinguished from the Fungi by the presence of chlorophyll and consequently by their mode of life. Even in the red, brown, and blue-green Algae chlorophyll is present, but the green color is masked by the presence of other coloring-matters. As the coloring-matter is usually the same throughout large groups of these plants which agree in other characters, particularly in the method of reproduction, they are classified as follows:
288 THE MICROSCOPY OF DRINKING WATER
Class I. Rhodophycea (or the Red Alge), containing a
reddish coloring-matter known as phycoerythrin.
Mostly marine. Class 2. PhctophycecK (or the Brown Algae), containing a
brown coloring-matter known as phycophsein.
Mostly marine. Class 3. Chlorophycece (or the Green Algae), containing only
the green coloring-matter known as chlorophyll.
Very largely fresh-water plants. The stored product
of assimilation is in allmost all cases starch. Class 4. Heterokontce (or the Yellow-green Alga), containing
a large proportion of a yellow pigment known as
xanthophyll. The stored product of assimilation
is a fatty substance. Fresh-water. Class 5. Bacillariece (or the Diatoms), containing a brown
coloring-matter diatomin, which much resembles
the phycophaiin of the brown algae. Universal
both in fresh and salt water. Class 6. MyxophycecB (or the Blue-green Algae), containing
a blue coloring-matter known as phycocj'anin.
The stored product of assimilation is most probably
glycogen. Mostly fresh-water.
Dr. West uses the term Myxophyceae in place of the better known term Cyanophycea*. For the sake of avoiding confusion the latter term is retained in the present volume. For the same reason the term Diatomaceae is used instead of Bacillariaceae.
The same writer also includes such oij^anisms as Dinobryon and Synura in the class, Phicophyceac, or the brown algae, while Calkins, our greatest American authority on Protozoa, includes them in the Protozoa. The latter seems to be the general practice among those who have studied the organisms from the water-works standi)()int. It is well to notice however, that these are examples ()f organisms about the status of which there is doubt.
Few Organisms Described. — Of the many thousands of different si)ecies of microscopic organisms found in fresh water
CLASSIFICATION OF THE MICROSCOPIC ORGANISMS 289
only a few are described in this book. These have been chosen chiefly because of their frequent occurrence and their important influence on the quality of the water in which they are found, but in some instances they have been included as representative of a class or group in order that the attention of the student may be drawn to them. The reader is urged to extend his studies beyond the confines of the present volume.
The description of the organisms is not in many cases car- ried beyond the genus. To describe the different species belonging to the same genus would have been quite beyond the possibilities of a small work. The reader should remember, however, that xmder nearly all of the genera mentioned there are a nimiber of common species. Similarly the plates do not include illustrations of all of the species commonly seen.
Coloring. — It is difficult to reproduce the colors of the organisms. Those shown on the plates are merely suggestions. The colors often cliange in the pipes of a distribution system. Diatoms change from brown to greenish-brown. Cyanophyceae becomes more bluish.
REFERENCES
Apstein, Carl. Das Plankton des SUsswasscrs und seine quantitative Bestim-
mung. Apparate. Schriften d. naturw. Vereins f. Schleswig-Holstein,
IX, 267-273. Apstein, Casl. 1891. Ueber die quantitative Bestimmung des Plankton im
Siksswasser in Zacharias' Thier- und Pflanzenwelt des Silsswassers. Bennett and Murray. 1889. A Handbook of Cryptogamic Botany. New
York: Longmans, Green, & Co. Blochmann. 1 89 1. Die mikroskopische Thierwclt des Silsswassers. Conn, Herbert William, and Webster, Lucia Washburn (Hazen). 1908.
A preliminary report on the algae of the fresh waters of Connecticut. Bulletin
No. 10, Connecticut geological and natural history survey. Hartford. Cooke, M. C. One Thousand Objects for the Microscope. London. Cooke, M. C. 1885. Ponds and Ditches. London. Engler, a., and K. Prantl. 1896. Die natUrlichen Pflanzenfamilien. Teil I.
Leipzig. Eyferth, B. 1885. Die einfaohsten Lebensformen des Thier- und Pflanzen-
reiches. Braunschweig. Griffith and Henfrey. 1883. The Micrographic Dictionary, 4th edition.
London: J. Van Voorst.
290 THE MICROSCOPY OP DRINKING WATER
HooKE, R. 1667. Micrographia, or Some Physiological Deicriptiofis of Minute Bodies, made by Magnifying Glasses, with Observations and Inquiries There- upon. London.
HooLE, Samuel. 1798. The Select Works of Antony Van Leeuwenhoek, con- taining his Microscopical Discoveries in many of the Works of Nature. Trans- lated from the Dutch and Latin editions published by the author. In two volumes. London.
KiscHNER und Blochmann. 1891. Die mikroskopische Pflanzen- und ThierwcH des SOsswassers. I. Phwts. II. Animals. 2d edition. Hamburg.
KiJTziNG, F. G. 1849. Species Algarum.
Lampert, Kurt. Das Leben der Binnengewasser.
Mez, Carl. 1898. Mikroskopische Wasseranalyse. Berlin: Julius Springer.
MiGULA, W. 1898. S3mopsis Characeanun europcanim. Leipzig,
Rabenhorst, Ludomco. 1864. Flora Europaca Algarum Aquc Dulcis et Sub- marine. Sec. I. Algas Diatomaceas complectens. Sec 2. Algas Phjrcocfa- romaceas complectens. Sec. 3, 1-20 Algas Chloroph^laceas. Sees. 3, 21-29 Melanophyceas et Rodophyceas complectens. Lipaic, 1864.
Stokes, A. C. 1895. Aquatic Microscopy. Philadelphia: Queen & Co.
TiEMANN and GXrtner. Die chemische und mikroskopisch-bakteriologiacfae Untersuchung des Wasscrs. Braunschweig: F. Vieweg & Son.
Ward, Henry B., and Whipple, G. C. 1914. Fresh Water Biology. [In Press.) New York, John Wiley & Sons, Inc. The latest book on the general subject. Each chapter is written by a specialist.
West, G. S. 1904. A Treatise on the British Fresh Water Algae. Cambridge. At the University Press.
Zaciiarias, Dr. Otto. 1891. Die Tier- und Pflanzenwelt des SOsswassers. a vols. Leipzig. J. J. Web^r. (A valuabb description of the common micro- scopic organisms found in fresh water.)
Zacharias, Dr. Otto. Annually since 1893. Archiv fOr Hydrographie u. Plank- tonkunde. Stuttgart £. Schweizcrbart. (A continuation of the preceding. These volumes contain many important papers by Dr. 2^acharias and his associates.)
Zacuarias, Dr. Otto. 1907. Das Siisswassersplankton. Leipzig: B. G. Teub- ner.
(See also page 393.)
CHAPTER XX
DIATOMACEiE
The Diatomaceae, or Bacillaries, comprise a group of minute vegetable forms of a low order. Their exact position in the scale of life has been the subject of much controversy. The early writers considered them to belong to the animal king- dom because of the power of movement that some of them pos- sess. Later, when they had become generally recognized as plants, they were considered as a Class or Order of the Algae. Some cryptogaraists, however, prefer to class them as an inde- pendent group, thereby recognizing the fact that they are quite different from most unicellular plants. This difference lies chiefly in the possession of siliceous cell-walls upon which may be observed certain markings that are constant in size and arrangement for each species. The great beauty of these markings, together with the infinite variety in the sizes and shapes of the cells of different species, have long made them objects of special study by microscopists. There are said to be upward of ten thousand species.
Diatom Cells. — ^A diatom cell is constructed like a box. There is a top and a bottom, known as the upper and lower valve, on both of which markings are found. The valves are connected by membranes known as " sutural zones," " con- nective membranes," "l^girdles," or, when detached, as " hoops." There are two of these membrances, one attached to each valve, and they are so arranged that one slides over the other just as the rim of a box-cover fits over the sides. This arrangement may be seen in Plate I, Figs. A, B, and C, where a typical diatom, Navicula viridis, is shown in three views.
291
292 THE MICROSCOPY OF DRINKING WATER
A represents the valve * view of the diatom, that is, the view seen when looking directly at the valve or the top of the box. B represents the girdle * view, the view seen when looking at the connective membrane. C is a cross-section through the diatom.
The upper or outer valve is indicated by a, and its connec- tive membrane by c. The girdle view shows how this connec- tive membrane of the larger valve fits over a similar one, (f, attached to the lower or smaller valve, b. These girdles have the power of sliding one upon the other so that the thickness of the diatom, i.e. the distance between the valves, is variable.
The valves of the diatom shown in the figure are covered with furrows or markings, g. At the center and at each end there are slight thickenings of the cell-wall, known as nodules. The central one is called the central nodule, J, and those at the ends, terminal nodules, e, e. Between these nodules and extending along the medial line of the valve "there is a jsort of ridge, /, in which there is a furrow called a raphe, or raph6. Through this the living matter of the diatom probably com- municates with the outer world. The slit is supposed to be somewhat enlarged at the nodules. The raph6, the nodules, and the markings, taken in connection with the shape and size
* The terms used by difTerent writers to express these two views of a diatom arc very ronfusing. In the following list the terms under A represent the valve view and those under B the girdle view.
A B
Valve view. Girdle view.
Side view. Front view.
Top view. Zonal \-iew.
Primary' side. Secondary side.
Secondary- side. Primary side.
Face valvairc. Face connective.
Vue de profil. Vue de face.
The terms " side view " and " front view " are those gencndly used by English and American diatomists, but the author has avoideti them as not being in them- selves sufiiciently clear, and has preferred to use the less euphonious but more self-explanatory terms, " valve view " and " girdle view." In consulting books on diatoms the reader should be careful to note the way in which the two views are designated.
:.
DIATOMACELE 293
of the valves, are the most important external features of a
diatom and are the first to be considered in studying them. '
Shape- and Size. — There is probably no class of unicellular organisms in which the outlines vary more than in those of * the diatoms. From the straight line to the circle almost all |
the geometrical figures may be found. Some of these may be I
described as circular, oval, oblong, elliptical, saddle-shaped, |
boat-shaped, triangular, xmdulate, sigmoid, linear, etc. The '
variations in shape are most marked in the valve view. The j
girdle view, as a rule, is more or less rectangular. The valves are usually plane surfaces, with only slight curvatures or xmdulations. Occasionally the surface is warped as in Amphi- prora and Surirella. As a rule the two valves of a frustule are nearly parallel, but in such forms as Meridion, Gom- phonema, etc., the frustule is wedge-shaped when seen in girdle view. The most varied forms are found in salt or brackish water, and the common fresh-water forms are so simple and so characteristic that the reader will have little diflBculty in assigning them their proper generic names. Some genera have the cell divided more or less completely by internal plates, called septa, when fully developed as in Rhabdonema; and vittae, when incomplete as in Grammatophora. Some diatoms have external expansions on the margin of the valves. Surirella, for example, has thin expansions known as ate, or wings. When these alae are imperfectly developed they are called keels. Nitzschia for this reason is said to be carinate. These wings or keels usually extend along the border of the raph6. Certain filamentous forms, such as Melosira, have processes at the point of attachment. In others these proc- esses are elongated into horns, or bristles.
Diatoms vary in size from the minute Cyclotella, less than lo microns * in diameter, to such large forms as Surirella and Navicula, that sometimes are one millimeter long. Some filamentous forms grow to a considerable length — often several feet.
*One micro-millimetcr, or micron (m), equals .001 millimeter.
294 THE MICROSCOPY OP DRINEINa WATER
Ifaikiiigs. — ^The valves of most Hiatnmng are marfrH with lines or points. In many cases the lines may be rescdved into series of points, pearls, beads, or stris, when a higgler power of the microscope is used. The variations in the number and size of these points and their uniformity in different individuals of the same species make them convenient objects fbr testing the resolving power of microscopes. The variaticHi in the number of these striae may be seen from the following table:
Nnmber of Stri« per If ilHmeter.
Longitadinal. Tmurcne.
Epithemia ocellata, Kz 800 450
Navicula major, Kz 850 630
viridiz, Kz 2400 720
lyra 850 1000
Cymbeila navicula, Ehb 1200 1500
Pleurosigma angulatum, Sm 1580 2100
S3medra pulchella, Kz 670 2x50
Navicula rhomboides 1 700 2700
Amphipleura pelludda, Ktz 3400 370010 5200
The extreme minuteness of these points, their various appearances under different conditions, and the difficulty of studying them even with microscopes of the highest magnify- ing powers, have given rise to many different theories concern- ing the character of the valves. Some writers insist that the points are elevations; others claim that they are depressions. Recent students agree that the structure is more complex than was formerly considered to be the case. The following con- ception of M. J, Deby, while perhaps not correct for all cases, is a good illustration of the modern view (see Fig. 72).
" The valves of most diatoms are composed of two layers, between which there are circular or hexagonal cavities bounded by walls of silica. The upper layer is not uniform in thick- ness, but is thin just above the cavities, and thicker, rising in pointed or rounded prominences, above the intersection of the walls of the cavities. The upper layer in lightly silidffed, and the thin portions are easily broken, making openings into the cavities. The lower layer bears varied designs the nature of which has not been well established. What authors have
DIATOMACE^
295
described as areolae, pearls, pores, orifices, granular projections, depressions, hexagons, beads, points, etc., are really one and the same thing.**
Cell-contents. — The frustule of a diatom is somewhat analogous to the shell of a bivalve — the living matter is inside. Just inside the cell-wall there is a thin protoplasmic lining (primordial utricle). This protoplasm sends radiating streams through the cell, and it is possible that a portion of it extends through the openings in the cell-wall and conmiunicates with the outer world. It is this layer of protoplasm also that secretes the silica of the cell-wall. Between the streams of protoplasm (PI. I, Fig. C) there are what appear to be empty
>
h^Ti:
n
r ^
n'
c'
^ 6'
TRICERATIUM PLEUR08IQMA
Fig. 72. — ^Transverse Section of a Diatom Valve. After Dcby.
a. Upper (outer) layer. d. Inter-alveolar pillars.
h. Lower (inner) layer. m. Thin part of upper layer.
c. Cavities. ». Bottom of alveols.
cavities. In or on the borders of these, oil globules may be sometimes observed. There is a nucleus, and probably a nucleolus, located near the center of the cell. The most con- spicuous portion of the cell-contents, however, consists of colored lumps or plates, which are usually constant in appear- ance and position for any particular species. The brown coloring matter of these " chromatophore plates " is known as diatomin. It is a substance analogous to chlorophyll and has been considered by some writers to be a compound of chlorophyll and phycoxanthin. The spectrum of diatomin is very similar to that of chlorophyll. There are two absorption- bands — one between B and C in the orange-yellow, and one between E and F in the indigo-violet. Diatomin is soluble in dilute alcohol, giving a brownish-yellow solution that is some-
296 THE MICROSCOPY OF DRINKING WATER
times very slightly fluorescent. When dried or treated with con- centrated sulphuric acid it assumes a green color. When living diatoms are exposed to the direct rays of the sun or sub- jected to heat for a considerable time the color of the chro- matophore plates changes from brown to green. In certain species other internal features have been noted; namely, the contractile zonal membrane, the germinative dot, double nucleus, etc., but of these there is little known.
External Secretions. — Living diatoms are covered with a transparent gelatinous envelope, which is probably a secre- tion from the protoplasm. In many species it is very thin and can be discerned only by the use of staining agents. In the filamentous and chain-forming species it serves to hold the frustules together. In Tabellaria, for example, little liunps of the gelatinous substance may be seen at the comers of the frustules at the point of attachment. Some species secrete great quantities of gelatinous material and are entirely embedded in it. In a few cases it is of a firmer consistency and forms tubes, stalks, or stipes, upon the ends of which the frustules are seated. These stalks attach themselves to stones, wood, etc., immersed in the water.
Movement. — Some of the diatoms exhibit the phenome- non of spontaneous movement. This has always excited interest and has been the subject of much speculation. It was the chief argument advanced by the early writers for placing the diatoms in the animal kingdom. The most peculiar movement is that of Badllaria paradoxa, whose frus- tules slide over each other in a longitudinal direction until they are all but detached, and then stop, reverse their motion, and slide backward in the opposite direction until they are again all but detached. This alternate motion is repeated at quite regular intervals. Some of the free species show the greatest movement, and of these Navicula is one of the most interesting. Its motion has been described as " a sudden advance in a straight line, a little hesitation, then other rectilinear movements, and, after a short pause, a return upon nearly the same path by similar movements.'* The move-
DIATOMACEL^ 297
ment appears to be a mechanical one. The diatoms do not turn aside to avoid obstacles, although their direction is some- times changed by them. The rapidity of their motion has been calculated to be " 400 times their own length in three minutes/' Their motion shows the expenditure of consid- erable force. Objects 50 or 100 times their size are sometimes pushed aside.
Jackson's Theory of Diatom Movement. — Various hypo- theses have been advanced to account for the movement of diatoms. Naegeli suggested that it was due to endosmotic and exosmotic current; Ehrenberg claimed that the movement was due to cilia; another writer, that it was caused by a snail- like foot outside the frustule; another, that it was due to a layer of protoplasm covering the raphe. H. L. Smith, after much study, came to the conclusion " that the motion of Naviculae is due to injection and expulsion of water, and that these currents are caused by different tensions of the internal membranous sac in the two halves of the frustule.''
Jackson has suggested that it is due to the liberation of gases. In a very instructive paper published in the American Naturalist, he says:
" The first intimation of the true nature of this motion was suggested by the action of a lithia tablet in a glass of water. The bubbles of carbonic-acid gas given off set up the exact motions in the tablet that have been so often described for the movements of diatoms: A sudden advance in a straight line, a little hesitation, then other rectilinear movements, and, after a short pause, a return upon nearly the same path by similar movements.
" Repeated experiments with compressed pellets evolving gas have shown that this is the usual motion produced by the evolution, of gas bubbles, and when pellets were made of the same shape as Navicula the movements of these diatoms were perfectly duplicated. Boat-shaped pieces of aluminum two millimeters thick were then made and on them were cut longi- tudinal grooves to resemble those of the diatom. When placed in strong caustic soda solution the movements of the metal produced by the evolution of hydrogen gas again duplicated those of the diatom in a remarkable manner. The metal having
208 THE MlCK(.)Se'UPY OF JJltlNKlXG WATER
Clallinxysiis. Xioo. StiRcorlonlum. Xio
Platk n.
Photiiraiirojsraplis nf MiciiisfDiiii.- I)r|;iiiiismi Kounil in Water.
I |{y John \V. M. Ilmiktr.)
DIATOMACELffi 299
the grooves had a greater power of motion than that without the grooves.
" If we consider that the diatom contains chlorophyll bands which when exposed to a strong light rapidly evolve oxygen, and if we take into account the fact that the motion does not take place unless the light is fairly strong, we have then a conception of the true nature of the movements of these organisms.
" Streams of oxygen may be readily seen evolving from all parts of many of the larger aquatic plants when submerged in water and exposed to strong light, but in the diatom while the gas prodticed is large in amount compared with the size of the organism, the actual amount evolved is so small that it is taken into solution almost inunediately. That such evolution takes place, however, is shown by Professor Smith's experi- ments with indigo. If now we examine the artificial diatom made of aluminum and placed in strong caustic solution we find that the bubbles from all sides come together and rise in a line corresponding to the median line or raph6 of the organism, and that if indigo is placed in the liquid it collects and rotates near the central nodule just as described by Professor Smith to prove his theory of the presence of water currents.
** It is therefore evident that the motion of diatoms is caused by the impelling force ^of the bubbles of oxygen evolved, and that the direction of the movement is due to the relatively larger amount of oxygen set free first from the forward and then from the rear half of the organism. This accoxmts for the hesitancy and irregular movements as well as the motion forward and backward over the same course.
" The evolving gas seems to act at times as a propeller to push the organism forward and at other times to exert a pulling action to raise the growth on end. The various movements described are the resultants of varying proportions of both of these active forces.
" The fact that a longitudinal groove on the under side of the artificial diatom causes it to become more active, due to the expulsion of the gas along the line of the groove, explains the greater activity of the Raphidea^.
"The most interesting and peculiar movements among diatoms are those of Badllaria paradoxa whose frustules slide over each other in a longitudinal direction imtil they are all but detached and then stop, reverse their motion and slide back again in the opposite direction until they are again almost separated. When the. diatoms are active, these alternating movements take place with very considerable regularity. It
300 THE MICROSCOPY OF DRINKING WATER
is probable that the mdi\'iduals in a group of Badllaria are joined together much more loosely than other laterally attached genera and that when a forward movement takes place in the outer indi\'idual it is arrested by capillarity just before the diatom is completely detached.
" It can now be readily seen that the strange movements of the other microscopic plants may be explained as also due to the e\'olution of ox>'gen gas. While the movements of desmids are not as strongly marked as those of diatoms, many of them, notably Penium and Closterium, ha\'e often been described as hax-ing a power of independmf motion, and Stahl found that this motion is greatly affected by light.
'' The best account of the movements of desmids has been given by Klebs. This author speaks of four kinds of move- ments in desmids, \iz. :
'' (i) A forward motion on the surface, one end of each cell touching the bottom, while the other end is more or less elevated and oscillates backward and forward.
** (2) An elevation in a vertical direction from the sub- stratum, the free end making wide circular movements.
" (3) A similar motion, followed by an alternate anking of the free end and elevation of the other end.
** (4) An oblique elevation, so that both ends touch the bottom — lateral movements in this position; then an elevation and circular motion of one end and a sinking again to an oblique or horizontal position.
'* This obser\'er considered these movements to be due to an exudation of mucilage, and the first two to the formation, during the action, of a filament of mucilage by which the desmid is tem- I)()rarily attached to the bottom and which gradually lengthens.
" These four kinds of movements are very easily explained by the theory of the evolution of gas, and by regulating the con- ditions they can be exactly reproduced in the artificial desmids made of aluminum. In this case strips of thin aluminum foil should be used. When the gas production is very strong at one end, the desmid will be raised to a vertical position and will take up oscillating or circular movements.
** If we now pass to a consideration of like movements in the Cyanophyceic, the same explanation holds true for Oscillaria which often takes up a waving or circular motion when attached at one end. This movement is well described by Griffith and Henfrey * as follows:
* Micrographic Dictionary, p. 561.
DIATOMACEiE 301
it
The ends of the filaments emerge from their sheaths, the young extremities being apparently devoid of their coat; their ends wave backward and forward, somewhat as the fore- part of the bodies of certain caterpillars are waved when they stand on their prolegs with the head reared up. The authors attribute this motion to ' irregular contraction of the different parts of the protoplasm.'
** The free-swimming species of Nostoc all have a spontaneous power of active motion in water, and in all of the filiform orders of the Cyanophyceae, detached portions of the filament known as hormogones also have the power of spontaneous motion. All of these movements can be exactly duplicated with lithia tablets in water or with aluminum of the proper weight and shape immersed in strong caustic solution and are also undoubt- edly caused by the strong evolution of oxygen gas due to the acti\aty of the chlorophyll present in the organisms.*'
Multiplication. — Diatoms multiply by a process of halv- ing or splitting, the Greek word for which gives rise to the name diatom. The cell-division is similar to that in all plants, but in this case the process is of especial interest because of the rigid character of the cell-walls.
The process begins by a division of the nucleus and nuc- leolus. The protoplasm expands or increases in bulk, forcing the valves apart, the hoops sliding one out of the other. The two halves of the nucleus separate, the diatomin collects at either side, and a membrane forms, dividing the cell into two parts. Finally the two parts separate. The newly formed membrane becomes charged with silica, making a new valve, and soon after its hoop develops. This process is well illustrated by a drawing of M. J. Deby, shown on PI. I, Figs. D, E and F. Sometimes the frustules separate entirely; sometimes they remain attached forming filaments, as in Melosira, bands as in Fragilaria, or zigzag chains as in Tabellaria.
The above is the usually accepted theory of cell-division. It is probably correct in many, if not in most cases. It assumes that the siliceous walls are not able to expand, and the result is that after repeated division the frustules become smaller. It is claimed that in some cases the cell-wall does
302
THE MICROSCOPY OP DRINKING WATER
expand, and therefore that the size of the frustules does not decrease after division.
The generally accepted theory of cell-division assumes that a diatom frustule has two valves, one the larger and older, and the other the smaller and yoimger. After division two cells are formed, one equal in size to the larger valve and the other equal to the smaller one, the difference in size being twice the thickness of the hoop. This theory also assumes that both the mother- and the daughter-cell have the power of further division. From these assumptions certain laws of multiplication may be deduced. For example: If il is the parent cell,
After one period of time, /, A will have produced B\
a
it
|
two periods " |
" 2t,A |
||
|
and B |
|||
|
three " " |
" 3t,A |
||
|
B |
|||
|
B' |
|||
|
C |
|||
|
and so on. |
B',
C;
B'\
C",
C,
D;
From this it happens that
After /we have lA + iB; " 2/ " " 1A + 2B+C; " 3/ " " 1A+3B+SC+D; and so on.
The laws may be expressed mathematically as follo¥^:
1. As the number of periods of division increases in arith- metical progression the total number of frustules increases in geometrical progression.
2. The number of frustules equal in size after any period of division are represented by the terms of the binomial theorem {ai-bYy where a and b are unity.
These laws have been demonstrated experimentally, the first by the author and the second by Miquel.
DIATOMACEiE 303
Reproduction. — ^The continued process of multiplication results in a constant diminution in the size of the frustules. After a certain minimum limit of size has been reached or after their power of multiplication has become exhausted, a reproductive process takes place. Usually this consists of a conjugation which results in the formation of a large cell, or auxospore, capable of reproducing a frustule of large size which, by multiplication, gives rise to a new series of frustules like the first. This theory, known as " Pfitzer's Auxospore Theory," was advanced in 1871. Count Castracane has shown that its application is not universal, and that in the case of some diatoms reproduction takes place through the formation of spores, or "gonids," which become fertilized by conjugation and, after a period of repose, attain a condition for living an independent life and reproducing in every respect the adult type of mother-cell. The author has observed these spore-like bodies in the cells of Asterionella.
There are few reliable data to be found in regard to the reproduction of diatoms. True conjugation has been observed in comparatively few genera. It is believed that there are four methods of conjugation. Firsts a single frustule, self- fertilized, producing one sporange and one auxospore; second, a single frustule, self-fertilized, producing two sporanges and two auxospores; third, two conjugating frustules, with undif- ferentiated endochrome, producing one sporange and one auxospore; fourth, two conjugating frustules, with differen- tiated endochrome, producing two sporangial cells, one of which is sometimes abortive. Cjood examples of conjugation may be found in Surirella splendida, Epithemia turgida, and in various species of Melosira. The sporangial frustules of Melosira (shown in PL HI, Fig. 17) are quite common.
Classification of Diatoms. — Several methods of classifi- cation of diatoms have been proposed, but only two are worthy of attention, and even these must be considered as provisional.
The most recent is that proposed by Pfitzer and elaborated by Petit. It is based upon two assumptions — ^namely, that
304 THE MICROSCOPY OF DRINKING WATER
the internal disposition of the endochrome is constant for all individuals of the same species, and that the relation between the frustule and the endochrome is fixed and common to all species of the same genus. The family Diatomaceae is divided into two sub-families, the Placochromaticeae and the Cocco- chromaticeaj. The genera of the first sub-family have the endochrome arranged in plates or layers, and those of the second sub-family, in lumps or small granular masses. Secondary classification into tribes, etc., depends upon the symmetry of the valves with reference to the axes, the dis- similarity of the valves of a single frustule, the presence or absence of an intervalvular diaphragm, the raph6, nodules, etc. There is little to be said in favor of this system, but it is worthy of study as the authors have tried to do what has been long neglected — namely, to emphasize the study of the entire cell with its contents rather than to confine the atten- tion wholly to the cell-wall or frustu!e.
The most useful system of classification and the one generally recognized is that suggested by H. L. Smith. It is based almost entirely on the morphology of the frustule. This has the advantage of enabling one to classify both living and fossil forms, but it has tended to divert observers from the study of the diatom as a living cell to the study of the shell alone.
According to Smith's classification the Diatomaceae are divided into three tribes characterized by the presence or absence of a raph6. An outline of this classification, together with descriptions of the genera most common in drinking water, is given below. The names of the genera are printed in heavy type.
TRIBE I. RAPHIDIEiE
Always possessing a distinct raphe on one or both valves. Central nodule generally present and conspicuous. Frustules mostly bacillar in valve view; sometimes broadly oval; with- out spines or other processes. Navicula major is the tjrpical form.
DIATOMACEiE 305
Family Cymbellea. — Raph6 mostly curved. Valves alike, more or less aroiate, cymbiform.
Amphora.
Frustules single, ovoidal in girdle view, the girdle often striated or longitudinally punctate. Valves extremely imsymmetrical, with a convex and concave side, with an eccentric raph6, with medial and terminal nodules. The raph6 is sometimes near the convex side, sometimes near the concave side, and the medial nodule is often away from the center. There are transverse striae, radiating somewhat from the medial nodule. This genus is very ornate. There are a number of species, none of them very conmion in water. (PI. I, Figs, i and 2.)
Cymbella.
Frustules generally single, elongated, symmetrical with respect to the minor axis. Valves more or less arched, with one side very convex and the other side slightly or not at all convex; asymmetric- ally divided by a curved raphd; possessing terminal .and medial nodules; marked by transverse bead-like strix, which do not extend to the raph6, but have a clear space, wider at the medial nodule than elsewhere. There are a number of conmion species. (PI. I, Figs. 3 and 4.)
Encyonema.
Frustules, when young, enclosed in a hyaline mucilaginous tube, in which they multiply by division, pushing each other forward in an alternately inverse position. Valves symmetrical with respect to the minor axis, convex on one side, straight on the other, with rounded extremities that project beyond the straight side. A straight raph^ divides the valves into two unequal parts. There are medial and terminal nodules. The striae are transverse or radiating some- what from the medial nodule. There is a clear space around the medial nodule, but elsewhere the striae approach closely to the raph6. There are several species. (PI. I, Fig. 5.)
Cocconema.
Frustules, when young, borne singly or in pairs on filamentous pedicels, which may be simple or branched. They form muci- laginous layers on submerged objects. Later they become free- swimming. The valves are long, large, strongly arched, convex on one side, concave on the other side save for a little inflation in the middle. The raph6 is curved. There are medial and terminal Dodules. The striae are rather large pearls, transverse, with very alight radiation, and not approaching the raphe closely. (PL I, Fig. 6.)
306 THE MICROSCOPY OF DRINKING WATB5R
Family NAVicuLEiE. — Valves symmetrically divided by the nphL Frustules not cuneate or cymbiform.
Navicula.
Frustules, single, symmetrical with re^>ect to both axes. Valves naviculoid, or boat-shaped; of various proportions, some very long and narrow, others short and wide, others eUipsoidal; with straight or slightly cturving sides; with ends pointed or rounded. There is a straight raph6 with conspicuous medial and terminal nodules. The valves are marked with transverse furrows, that have a slight radial tendency. The frustules are rectangular in girdle view and show the nodules plainly. There is a vast number of species and varieties, many of which are very common. In some species the striae can be resolved into pearls. These are the Navi- culae proper. In other species they cannot be resolved, and the valves usually have wide rounded ends. These were formeriy set apart as a separate genus — Pinnularia. (PI. I, Figs. 7 and 8.)
Stauroneis.
Frustules similar to those of Navicula. Valves symmetrical, possessing a straight raph^, with medial and terminal nodules. The strias are pearled. There is a narrow clear space along the raph6 and a wider transverse clear space at the medial nodule extending to the sides of the valve, so that the valves have the appearance of being marked with a cross. A number of species have been described, but in some instances they arc very similar to Navicula. (PL I, Figs. 9 and 10.)
Schizonema.
Frustules quite similar to those of Navicula, and enclosed in muci- laginous tubes, as Encyonema. Raph6 straight, sometimes showing a double line. Striae generally parallel, reaching to the raph6, but not to the central nodule, around which there is a clear space. More common in salt water than in fresh water.
Pleurosigma.
Frustules like those of Navicula, but with axis turned like a letter S. Raphe sigmoidal. Striae ornate, pearled, very fine on some species. Endochrome in two layers. (PL I, Fig. 11.)
Family GoMPHONEMEiE. — Valves cuneate; central nodule uneqiially distant from the ends.
Qomphonema.
Frustules borne on pedicels more or less branched. Valves wedge- shaped, with more or less undulating margins and rounded ends. A central nodule near the large end. Raph6 straight, dividing the
DIATOMACEiE 307
valve symmetrically. Striae pearled, transverse, radiating slightly about the nodules. The frustules seen in girdle view are wedge- shaped, with straight sides and with central nodule visible. There are a number of species, some of which are common. (Pl. I, Fig. 12.)
Family CoccoNroEiE. — Frustules with valves unlike. Valves broadly oval.
Cocconeis.
Frustules somewhat arched or lens-shaped; in valve view, ellip- tical or discoidal. Striae have a general direction transverse to the axis, but the convexity of the frustules gives them the appearance of inclining toward the poles. Upper and lower valves dissimilar, possessing a medial nodule and raph^ or pseudo-raphe. (PI. I, Figs. 13 and 14.)
TRIBE n. PSEUDO-RAPHIDIEiE
Possessing a false raphe (simple line or blank space) on one or both valves; with or without nodules. Frustules generally bacillar, sometimes oval or suborbicular, without processes, spines, or awns. Synedra Gaillonii is the typical form.
Family FRACiLARiEiE. — Frustules adherent, forming a ribbon-like, fan-like, or zigzag filament, or attached by a gelatinous cushion or stipe.
Epithemia.
Frustules cymbiform, symmetrical with respect to the minor axis, with a false raphe and no nodules. Valves marked by lines and pearls approximately at right angles to the major axis, but inclined toward the end of the frustule on the convex side. The frustules in girdle view are seen to be somewhat inflated at the center. There are several species, differing considerably in the shape of the valves. (PJ. I, Figs. 15 and 16.)
Eunotia.
Frustules elongated, symmetrical with respect to the minor axis. Occurring singly, free-swunming or attached. Valves arcuate, with the convex side undulated. Transversely striated, with two false terminal nodules and no medial line. The frustules are quad- rangular in girdle view. There are but few species, the most com- mon being the E. tridentula, (PI. I, Fig. 17.)
308 THE MICROSCOPY OF DRINKING WATER
Himantidium.
Sometimes included under Eunotia. The frustules differ from Eunotia by remaining attached after division, forming a band as in Fragilaria; by having the convex side of the valve entire instead of undulate; and by being somewhat bent in girdle view. (PL II, Figs. I and 2.)
Asterionella.
Frustules long, linear, inflated at the ends. They are united by their extremities into stars or chains, as shown in the girdle view. The typical group is composed of 8 frustules synunetrically and radially arranged. Groups of 4, 6, or 7 are common. When rapidly dividing they may assume a spiral arrangement. The valves are very finely striated, with a straight pseudo-raph6. There is one * general species, the A. Jormosaj characterized by having the basal end of the frustules much larger than the free end, and by having on that end a larger surface in contact with the adjoining frustules. There are several varieties, advanced by some authors to the rank of species. The most conunon is A. fonnosa, var. graciUima, (PI. II, Figs. 3 to 7.)
Synedra.
Fnistules elongated, straight or slightly curved. Valves some- what dilated at the center and with a medial line or false raph6 and occasionally false nodules. They usually have straight and almost, but not quite, parallel-sides. They are finely transversely striated. There are several common species. S. pulchdla has lanceolate valves, with ends somewhat attenuated. In girdle view they are seen to be attached valve to valve and present the appearance of a long band or a fine-toothed comb. S. ulna has a very long rectilinear valve, with conspicuous transverse stride. There is a false raph6 with a narrow clear space. They are often free-floating. S. lanceolata has a long thin valve, swollen at the center, but tapering to sharp points at the ends. S. radians has straight needle-like valves. They are united at the base like Aster- ionella, but the frustules do not lie in the same plane. (PL II, Figs. 8 to II.)
Fragilaria.
Frustules attached side by side, forming bands as in the case of Synedra pulchella. Valves' elongated, straight, with ends lance- olate or slightly rounded. In girdle view the frustules are rectangular and are in contact with each other through their entire length. Valves transversely striated, with a false raph6 scarcely visible. There are several common species. (PL II, Figs. 12 and 13.)
DIATOMACEIfi 309
Diatoma.
Frustules attached by their angles forming zigzag chains, or rarely in bands. In girdle view they arc quadrangular. Valves elliptical- lanceolate, with transverse ribs, between which are fine stria;. There is a longitudinal pseudo-raph6. There are two common species — D. vulgare and D. knue, (PL III, Figs, i to 3.)
Meridion.
Frustules attached valve to valve, forming curved bands seen as fans, circles, or spiral bands. The frustules are wedge-shaped in girdle view, which causes the peculiar shape of the bands. Valves also wedge-shaped, with somewhat rounded ends; furnished with transverse ribs, between which are fine striae. Pseudo-raphe in- distinct. There is one principal species — M. circtdare, (PI. Ill, Figs. 4 and 5.)
Family Tabellarie^. — Frustules with internal plates, or imperfect septa, often forming a filament.
Tabellaria.
Frustules square or rectangular in girdle view, attached by their comers and forming zigzag chains. In this view they are seen to be marked with longitudinal dividing plates, which extend from the ends not quite to the middle and which terminate in rounded points. The valves are long and thin, and are dilated at the ex- tremities and in the middle. There are fine transverse stria; and an indistinct pseudo-raphe. The endochrome is usually in rounded lumps. There are two very common species — T. fcncstrata and T. flocctdosa. (PI. Ill, Figs. 6 to 9.)
Family SuRiRELLEiE. — Frustules alate or carinate; frequently cuneatc.
Nitzschia.
Frustules free, single, elongated, linear, slightly arched, or sig- moidal; with a longitudinal keel and one or more rows of longi- tudinal points. Valves finely striated, without nodules. There are many species. (PI. Ill, Figs. 10 to 12.)
Surirella.
Frustules free, single, furnished with ala; on each side. A trans- verse section of the frustule shows a double-concave outline. Valves oval or elliptical, with conspicuous transverse tubular stria;, or canaliculi, between which there are sometimes very fine pearled striae. There is a wide clear space, or pseudo-raphe. The frustules are sometimes cune?.te in girdle view. The valves sometimes have a warped surface. There are many common species, most of them of very large size. (PI. Ill, Figs. 13 and 14.)
310 THE MICROSCOPY OF DRINKING WATER
TRIBE m. CRTPTO-RAPHIDISJB
Never possessing a raph6 or a false raph£. Frustules generally circular or angular, often provided with teeth, spines, or processes. Stephanodiscus Niagara is the typical form.
Faioly MELOSiREiE. — Frustulcs cylindrical, adhering and forming a stout filament; valves circular, sometimes armed with spines.
•
Melosira.
Frustules with circular valves and very wide connective bands, attached valve to valve so as to form long cylindrical filaments. In girdle view they are usually rectangidar, though sometimes with rounded ends; at the center there are often conspicuous con- strictions. The girdles are often marked with dots. The valves arc radially striated, with a clear central space. At the edge there is often a keel or row of projecting points, seen in girdle view. There are several common species. M. granulala is the most common free-floating form, and M. varianSy the most common filamentous form. (PI. Ill, Figs. 15 to 17.)
Faauly CosciNODiscEi*:. — Valves circular, generally with radiating cellules, granules, or puncta; sometimes with marginal or intramarginal spines or distinct ribs; without distinct processes.
Cyclotella.
Frustulcs discoidal, single, occasionally attached valve to valve, but never forming long filaments. Valves circular, finely marked by radial striai. There is usually an outer ring of radial lines, inside of which there are puncta and fine dots somewhat irregularly arranged. These cannot l>e seen with low powers. In girdle view the frustules appear rectangular or somewhat sigmoidal, with warped valves, as in C. opcrciilata. They are often of very small size. (ri. Ill, Figs. 18 and 19.)
Stephanodiscus.
Frustulcs discoidal, single. Valves circular, with curved surface, with fringe of minute marginal teeth. Stria; fine radial. Frustules rectangular in girdle view, showing projection of middle of valve. Teeth most conspicuous in girdle view. Kndochrome conspicuous, in rounded lumps. The frustules are often of considerable size. (PI. Ill, Figs. 20 and 21.)
DIATOMACE^ 311
REFERENCES
Apstein, C. 1896. Das SQsswasserplankton. Kiel u. Leipzig, Lipsius & Tischer. Attwood. Diatoms from the Chicago Water Supply. Mo. Micro. Jour.,
XVII, 266. London. Bronns Klassen u. seit 1859. Ordnungen des Tierreiches (Protozoen, einige
Gruppen der Metazoen). Leipzig, C. F. Winter. Castracane, Cont Abb£ F. 1889. Reproduction and Multiplication of
Diatoms. J. R. M. S., 22. London, 1889. Deby, Juuen. 1882. A Bibliography of the Diatomaceae. " A Bibliography
of the Microscope," III. London. Also, Bibliographie Diatomologique.
Jour. Microg., XI, 217. Paris, 1887. HA.SSALL, Arthur H. 1856. The Diatomaces in the Water Supplied to the
Inhabitants of London: Microscopic Examination of the Water. London. Kjrchner, O. 1 89 1. Die mikroskopische Pflanzenwelt d. SUsswassers. 2.
Aufl. Hamburg, L. Gracfe & Sillem. KuNKHARDT, W. scit 1908. Revue, Internationale, der gesamten Hydro-
biologie und Hydrographie, Leipzig. KuETZiNG, F. 1844. Die Bacillarien, odor Diatomeen. Nordhausen. Mills, Fredk. Wm. 1893. An Introduction to the Study of the Diatomaceae.
London; also, The Microscopical Pub. Co., Washington, D. C. Contains
an extensive bibliography on the Diatomaceae by Julicn Deby. MiQUEL, P. De la culture artificielle des Diatom6es. Le Diat., I, 73, 93, 121,
123, 149, 165. Paris. Felletan, J. 1 891. Les Diatom^es. Paris. Schmidt, Adolf. 1875. Atlas der Diatomacccn-Kundc. In Vcrbindung mit
den Herren Gnmdlcr, Grunow, Janisch, Weissflog und Witt. (There is a
blue-print reproduction of these plates by C. Henry Kain, Camden, N. J.) SchDtt, F. 1892. Analytische Planktonstudicn. Kiel }i. Leipzig, Lipsius &
Tischer. ScHURiG, W. 1909. Plankton-Praktikum. Leipzig. Quelle & Meyer. Smith, H. L. 1872. Conspectus of the Families and the Genera of the Diato-
maceae Lens, I, i, 72, 154. Chicago. Notice in Amcr. Naturalist, VI, 318.
Salem, 1872. Smith, Wm. 1853-56. Synoi>sis of the British Diatomacese. 2 vols. London. Van Heurck, H. 1885. Synopses des Diatom6cs dc Bclgique. Anvers. Whipple, G. C, and Jackson, D. D. 1899. Asterionella. Journal of the
New England Water Works Assn. Vol. XIV. Wissenschaptliche Meeresuntkrsuchungen. seit 1873. Herausgcgebcn
V. d. Kommission z. Unters. d. deutsch. Meere in Kiel und der Biolog.
Anstalt auf Helgoland. Kiel, Schmidt u. Klaunig (Friiher (inter andcrcm
Titel). Wolle, Francis. 1890. Diatomaceae of North America. Bethlehem, Pa.
(See also page 393.)
CHAPTER XXI SCHIZOMYCETES
The Schizophyceac comprise those vegetable organisms in which the chief mode of propagation is that of cell-division. They are either destitute of chlorophyll or contain besides the chlorophyll a coloring substance known as phycocyan or phycochrome, which itself may be a modification of chloro- phyll. The cells have a somewhat firm cell- wall, but no nucleus.
The Schizophycea; may be divided into two classes — the Schizomycetes and the Cyanophycea. The latter contain chlorophyll, but the former do not.
Besides the bacteria, which are not described in this work, there are few genera belonging to the Schizomycetes that are of interest to. the waler-analyst. They are so imperfectly understood that no satisfactory classification has been sug- gested. Some authorities include them among the Fungi.
Leptothrix.
Simple filaments, with indistinct or no articulation, without oscil- lating; movement, and with no sulphur-granules. There are several indistinct species. They arc usually colorless. The aquatic forms (MTcur as interwoven masses of long slender filaments, the diameter of which varies from i to .^ m- The organism often called Leptothrix (n7/r(/r<7/, observed in driven wells where the water contains much iron, is now known as Chlamydothrix ochracea. Very slender forms of Oscillaria arc liable to be mistaken for Leptothrix. (PL IV, Fig. 1.)
Cladothrix.
Fine filaments resem])ling those of Leptothrix, colorless, usually indistinctly articulated, straight, undulated, or twisted. There are several stages of tlevelopment, giving rise to coed-, vibrio-,
312
SCHIZOMYCETES 313
spirochete-, and filamentous-forms. The special characteristic of the genus is that of false branching, a turning aside of single portions ot the filaments followed by subsequent terminal growth. There are several indistinct species. The most important is C. dichotomay which is found in sewage and polluted water. (PL IV, Fig. 2.)
Beggiatoa.
Threads indistinctly articulated* colorless, containing numerous dark sulphur granules. The filaments often have an active oscil- lating movement. They are usually short and from i to 3 /i in diam- eter. Sometimes abundant in sulphur springs. There are several doubtful species. The most common is B. alba, (PI. IV, Fig. 3.)
THE IRON BACTERIA
Of the organisms which deposit iron Crenothrix is the most conspicuous example and the one which is most often men- tioned by American writers. The name Crenothrix has as a matter of fact been applied to several genera which are recognized as distinct. The following description has been commonly given of Crenothrix.
Crenothrix.
Filaments unbranched, cylindrical, transversely divided into cells, surrounded by a gelatinous sheath which becomes yellow or yellowish-brown through deposits of iron or manganese. Mul- tiplication takes place by transverse fission and occasionally by longitudinal fission. Cells also escape from the sheath at the end or side and, by division, form new ^ments. Repro- duction occurs through spores formed from the cells within the sheath. It occurs in single filaments or in brownish tufts or mats, often of considerable thickness. The filaments are i^ to 4 /I thick, and the sheath is several times the thickness of the filaments. Articulation is distinct. When the iron of the sheath is dissolved by dilute hydrochloric acid the cells appear in side view as distinct rectangles, each one somewhat removed from its neighbor. This appearance is characteristic of Crenothrix. During growth the cells sometimes push themselves forward in the sheath, leaving the empty sheath behind. The older portion of the sheath is darker colored than the growing points. Creno- thrix occurs chiefly in ground- waters rich in organic matter, iron :salts and carbonic acid and deficient in oxygen. Its grov/th is favored by darkness. (PI. IV, Fig. 4.)
iu
TJiE Ul^.iy.fivyjFY 0Â¥ DRIXnXG WAICB
jhr.kifjL liiti pr»"jf*ee- &
cbflB&aiiaB of slus gams, bused
'jc :b^ cLfcTLrrjTT oc :bt *bthzh*ytpusi^. C. ATaiBuau. vfaidi deposits .Tvr.. }k r^r.:^:.-^ . L<^<^.lirix orirarM. vibch deposits ahimiiu,
r. he cjuls C. ■ftj4r{j«7>Vj.
Other Iron Bacteria.
The ocher 27X381 lorreTia difer from Crenotfarix duefly in the W^j-r^T^ € hAnneri^: ics:
Fk;. 73. Iron B.\rTi:RL\
1. ^renothrix.
2, ^"Irtdothrix.
S. Oallionclla.
3. rionothrix.
4. Chlaxnydothris.
ChUimydolhrix has a brownish sheath and is branched. The ohlrr filanunts arc deeply colored with the oxides of iron or man-
(iiilliofnUti has its filaments twisted into a helix. Often two
rilimmts are twiMed together.
Chidnthrix has I he characteristic false branching.
Clniintlirix has branched filaments, the ends of the branches bciiig poiiiti-d.
Thrsi- (lilTcrenl Reiiera are shown in Fig. 73*
More (oinplete descriptions may be found in "Die Eisenbak- trrirn" by Dr. Mans MoH>ch.
The stems of antho|)hysa, an organism very common in swampy waters are often mistaken for organisms of this group.
SCHIZOMYCETES 315
REFERENCES
CoHN, F. 1870. Ueber den Brunncnfaden, mit Bemerkungen Uber die mikro-
skopische Analyse des Brunnenwassers. Beitr&ge zur Bio1ogie« I, 11 7-1 31. Cooke, M. C. 1886. Rust, Smut, Mildew, and Mould: An Introduction to
the Study of the Microscopic Fungi, sth edition. London: W. H. Allen
&Co. DeBary, A. 1887. Comparative Morphology and Biology of the Fungi, Myceto-
zoa, and Bacteria. Oxford: Clarendon Press. De Vries, Hugo. 1890. Die Pflanzen und Thiere in den dunkein Rilumender.
Rottcrdamer Wasscrleitung. Jena. Garrett, J. H. 1896-97. Crenothrix polyspora, var. Cheltonensis. A history
of the reddening and contamination of a water-supply and of the organism
which caused it, with general remarks upon the coloration and pollution of
water by other algae. Public Health, IX, 15-21. London. GiARD, A. 1882. Sur le Crenothrix Kuhniana; la cause de Tinfe'ction des eaux
de Lille. Compt. rendu Acad. d. Sc, XCV, 247-249. Paris. MoLiscH, Dr. Hans. 1910. Die Eisenbakterien. Jena: Gustav Fischer. Jackson, Daniel D. 1901. A New Species of Crenothrix. Transactions of the
Amer. Micros. Soc. August, 1901. ZoPF, Dr. Wilhelm. 1890. Die Pilze. Breslau.
(See also page 393.)
CHAPTER XXII CYANOPHYCEi*:
The plants belonging to the Cyanophyceae, or Myxophyceie, arc characterized by the presence of chlorophyll plus certain coloring substances known as cyanophyll, phycocyanine, phy- coxan thine, etc., which are probably modifications of chloro- phyll; by the absence of a nucleus and usually of starch-grains; and by extremely simple but imperfectly understood methods of reproduction. The plants are one- or many-celled. By successive division of the cells they are very commonly associ- ated in families that take the form of filaments or of spherical or irregular masses.
The cell-wall is often distinct and sharply defined, but in some cases it is fused with a gelatinous mass in which the cells are embedded. This gelatinous matrix is more common in the terrestrial than in the aquatic species. The cell-con- tents arc usually granular and homogeneous.
The color varies considerably in different species and under different conditions. It is never a chlorophyll green, but ranges from a color approaching that to a blue-preen, orange- yellow, brown, red, or violet. The coloring matter known as phycocyanine has a bluish color when viewed by transmitted light, and a reddish color when viewed by reflected light. This phenomenon is often observed in ponds where Cyanophyceae are al)undant. Looking directly at the pond the water may have a reddish-brown color, while a bottle filled with the water and held to the light may present a decidedly bluish-green appearance. This is particularly true when the plants have begun to decay. The phycoxanthine is said to have a yellowish color. The liberation of the gas bubbles from some species
316
CYANOPHYCE*
in
■'•■r^
s3
â– .^â– ^m^
-Mil"
PWTE t".
Pholomitcographs of Microscopic Organisn
318 THE MICROSCOPY OF DRINKING WATER
seems to have an effect on the color of the organisms. Ana- bseijia, for example, may have a brownish-green color in a reservoir and a very light blue-green color after it has passed through the pipes of a distribution system, where the pressure has caused the gas to be expelled.
The Cyanophyceae are usually separated into five or six groups, which are ranked by different writers as orders, families, or sections. The groups are here considered as families belonging to two orders.
ORDER I. CYSTIPHORJB
Unicellular plants with spherical, oblong, or cylindrical cells enclosed in a tegument and associated in families, are sur- rounded by a universal tegument or imfnersed in a generally colorless, mucilaginous substance of varying consistency. Division takes place in one, two, or three directions, the cells after division usually remaining together forming an amor- phous thallus. It is probable that most of the forms belong- ing to this order are but intermediate stages in the life-histor>' of plants higher in the scale of life. There is but one family. It contains about a dozen rather imperfectly defined genera.
Family CHROococcACEiE. — Thallus mucous or gelatinous, amor- phous, enclosing cells and families irregularly disposed.
Chroococcus.
Cells spherical, or more or less angular from compression, solitary or united in small families. Cell-membrane thin or confluent in a more or less firm jelly. Cell-contents pale bluish-green, rarely yellowish. I*ropagation by division in three directions. Several species are described. Most of them are terrestrial and not aquatic. The most common aquatic species are C. tiirgidus, the cells of which arc from lo to 25 ^ in diameter, and C. coluerens, the cells of which are from 3 to 6 m in diameter. (PI. IV, Fig. 5.)
Qloeocapsa.
Cells spherical, single or in groups: each cell surrounded by a vescu- liform tegument and groups of cells surrounded by an additional tegument. Cell-membrane thick, lamellated, and sometimes colored. Division in three directions. Cell-contents bluish-green, brownish.
CYANOPHYCEJE 319
or reddish. There are many described species, based on slight distinctions and variations in size and color. Gloeocapsa found in water usually has smaller cells and a more distinct tegument than ChroQcoccus. Comparatively few species are aquatic. (PL IV, Fig. 6.)
Aphanocapsa.
Cells spherical, with a thick, soft, colorless tegument, confluent in a homogeneous mucous stratum which is sometimes of a brown- ish color. Cell-contents bluish-green, brownish, etc. The cells divide alternately in three directions. There are several species. The cells vary in size from 3 to 6 /i. (PI. IV, Fig. 7.)
Microcystis.
Cells spherical, numerous, densely aggregated, enclosed in a very thin, globose mot her- vesicle, forming solid families, singly or several surrounded by a universal tegument. Cell-contents seruginous to yellowish-brown. The cells divide alternately in three direc- tions. This genus represents a condition of frequent occurrence in the process of development of higher forms. There are several indistinct species common in water. The cells vary in size from 4 to 7 M in diameter and the colonies from 10 to 100 n. (PL IV, Fig. 8.)
Clathrocystis.
Cells very numerous, small, spherical or oval, aeruginous, embedded in a colorless matrix. Multiplication by division of the cells within the thallus. The thallus is at first solid, then becomes saccate and dathrate (perforated); broken fragments are irregularly lobed. There is but one species — C. ctruginosa. The cells are from 2 to 4 M in diameter and the thallus from 25 ^ to 5 mm. This species is widely distributed. (PL IV, Fig. 9.)
Coelosphieri u m .
Cells numerous, minute, globose or subglobose, geminate, quater- nate, or scattered, immersed in a mucous stratum. Cell-contents sruginous, granulose. The thallus is globose, vesicular, hollow, the cells being found only on the outer surface. Multiplication takes place by division of the cells on the surface and by the escape and further development of certain peripheral cells. There is one common species, C. Kueizingianum, The cells are from 2 to 5 II in diameter and the thallus from 50 to 500 /x. (PL IV, Fig. 10.)
Merismopedia.
Cells globose or oblong, a^ruginous or brownish, with confluent teguments. Division in two directions. The thaUus is tabular.
320 THE MICROSCOPY OF DRINKING WATER
quadrate, free-swimming, the cells being arranged in groiqps of 4f S, i6, 32, 64, 128, etc. There are several indistinct ^>ecies. The diameter of the cells varies from 3 to 7 m. (PI. IV, Fig. 11.)
Qloeothece.
Similar to Glcrocapsa, but with oblong or cylindrical, instead of spherical cells. Terrestrial rather than aquatic
Aphanothece.
Similar to Aphanocapsa, but with oblong instead of spherical cells.
Tetrapedia.
Cells compressed, quadrangular, equilateral, subdivided into quad- rate or cuneate segments or rounded lobes, either by deep incisions or wide angular sinuses. This genus is of doubtful value.
ORDER n. NSMATOGENJB
Multicellular plants, the cells of which dividing in one direction, form filaments, often enclosed in a tubular sheath. The filaments (trichomes) may be either simple or branched. There are five families.
Family NosTOCACE<fi. — Plants composed of rounded cells loosely united into filaments, or trichomes, and sometimes embedded in jelly. The filaments do not branch and never terminate in a hairpoint. They sometimes form large masses. There are three kinds of ceUs — ordinary vegetative cells, joints, or articles; heterocysts; and spores. The ordinary cells are spherical, elongated, or compressed. The cell-contents are bluish- green or brownish, and are usuaUy granular. The heterocysts are cells found at intervals in the filaments. They are spherical, elliptical, or elongated, and are usually somewhat larger than the vegetative cells. Their cell-contents are generally clear or very finely granular, and usually of a light bluish-green color. The cell-wall is sharply defined, and there arc two polar lumps of gelatinous material that cause them to adhere to the adjoining cells. The function of the heterocysts is unknown, but they are thought to be in some way connected with the process of reproduction. The spores are usually much larger than the vegetative cells. They are spherical, elliptical, or cylindrical. Their cell-contents are usually very granular and dark-colored. They seem to be more highly differentiated than the contents of the vegetative cells. The spores are heavy, and will sink in water when freed from the filaments. Multiplication takes place
CYANOPUYCE.*; 321
by division of the vegetative cells, by means of the spores, and by means of hoimogons, or parts of the internal trichomes which separate from the filaments and form new plants. The character and position of the hetero- C3rsts and spores form the chief basis for the division of the Nostocacea; into genera. The classification is very indefinite.
Nostoc.
Cells globose or elliptical; heterocysts usually globose and some- what larger than the vegetative cells; spores oval and but little larger than the heteroc)rsts. Spores and heterocysts are both intercalated in the filaments, rarely terminal. The filaments are enclosed in a gelatinous envelope, and are flcxuously curved and irregularly interwoven. They often form gelatinous fronds or thalli surrounded by a firm membrane. The thalli vary in diameter and are sometimes of great size. There are many species, both terres- trial and semi-aquatic. The species are not well defined, and many of them are intermediate stages in the life-history of higher forms. The true Nostoc is seldom found in drinking water. (PI. IV, Fig. 12.)
Anabiena.
Vegetative cells spherical, elliptical, or compressed in a quadrate form. Heterocysts much larger than the vegetative cells, sub- spherical, elliptical, or barrel-shai)cd, of a pale yellowish-green color, and intercalated in the filament. Spores globose or oblong- cylindrical, equal to or somewhat larger than the heterocysts, rarely smaller, never adjacent to the heterocyst. The filaments are moniliform; are without sheaths; are straight, curved, circinate, or interwined; have a bluish-grccn or brownish color; and are often free-floating. There are several important but imperfectly defined species. The most common species are A. Jios-aquce and A . circinalis. The vegetative cells of the former arc from 5 to 7 /« in diameter; those of the latter are from 8 to 12 m. (PL I^^ Figs. 13 and 14.)
Spfuerozyga.
Vegetative cells spherical, elliptical, or transversely compressed; of a bluish-green or brownish color. Heterocysts spherical or oval, intercalated, binary or solitary, only slightly larger than the veg- etative cells. Spores on each side of and adjacent to the hetero- C)rsts, c>'lindrical, with rounded ends, considerably larger than tho heterocysts. The filaments are moniliform; are sheathless or cov- ered with a mucilaginous coating, occasionally agglutinated in a gelatinous stratum. There are several species, terrestrial and aquatic. The genus is very similar to Anabsena. (PL V, Fig. i.)
324 THE MICROSCOPY OF DRINKING WATER
disposed. Spores, when present, cylindrical, generally adjacent to the basal heterocyst.
Rivularia.
Filaments radial, agglutinated by a firm mucilage, and forming well-defined hemi^herical or bladdery forms. Heterocysts basal. No spores formed. Ramifications produced by transverse division of the trichomes. Color greenish to brownish. Sheaths usually distinct. Several spedes, terrestrial and aquatic. Occasionally found free-floating. (PL V, Fig. 9.)
REFERENCES (See pages 340 and 393.)
CYANOPHYCE^ 323
Sheaths pellucid, hyaline. Propagation is said to take place by hormogons and by gonidia. There are many species, terrestrial and aquatic. (PL V, Fig. 5.)
Microcoleus.
Filaments rigid, articulate, crowded together in bundles, enclosed in a common mucous sheath, either open or closed at the apex. Sheath ample, colorless, rarely indistinct. Several species, chiefly terrestrial. (PI. V, Fig. 6.)
Family ScvroNEifEiE. — Filaments with lateral ramifications (false branching) in which some of the cells change into heterocysts; enclosed in a sheath. The cells divide transversely. The ramifications are pro- duced by the deviation of the trichome and emergence through the sheath. The branches do not have a hair-point. There are several genera.
Scytonema.
Sheath enclosing a single trichome, composed of subspherical or subcylindrical ceUs, with scattered heterocysts. Color bluish- or yellowish-green. Ramification takes place by a folding of the trichomes, followed by rupture of the sheath and the emergence of one or two portions of the folded trichome at right angles to the original filament. These branched filaments produce interwoven mats. Multiplication is said to take place by microgonidia. There are many species, terrestrial and dquatic. The plant is not found free-floating. (PL V, Fig. 7.)
« Family Sirosiphone^. — Trichomes enclosed in an ample sheath, pro- fusely branched. Branches are formed by longitudinal division of certain cells so as to form two sister ceUs, the inferior of which remains a part of the trichome, while the other, by repeated division, grows into a branch. The filaments often contain 3, 4, or more series of cells. Propagation is said to take place by means of microgonidia.
Sirosiphon.
Cells one-, two-, or many-seriate, in consequence of their lateral division or multiplication. The cells have a distinct membrane and the sheaths are large. The plant is never found free-floating. (PL V, Fig. 8.)
Family Rivularie^. — Filaments free or agglutinated into a definite thallus, terminating at the apex in a hair-like extremity. Heterocysts usually basal. Trichomes articulated like Oscillaria, parallel or radially
324 THE ]aCB06COPY OF DBDHOXG WATER
dhpoKd. Spores, wben proent, cy^uKlrial, ^aiailljr adjaoeni to the tmil heierocyit.
Rimlaria.
FOamenU ndial, agglutinated by a finn mudlace, and fonning well-defined bemupherical or bladdery forms. Heterocysts basaL No spores formed. Ramifications produced by transvose divisioD of the trichomes. Grfor greenish to brownish. Sheaths usaally distinct. Several spedes, terrestrial and aquatic Oocasiooally found free-floating. (PI. V, Fig. 9.)
REFERENXES '(Sec pages 340 and 393.)
CHAPTER XXin
CHLOROPHYCEiE
The plants belonging to the Chlorophyceae are characterized by the presence of true chlorophyll, a nucleus, starch-grains, and often by a cell-wall made of cellulose. They are " algse '' in the strictest sense of the term. They cover a great range of complexity. Some of them are minute, unicellular forms scarcely distinguishable from the Cyanophyceae; others resemble the Protozoa; while others are large, branching, multicellular forms doubtfully included among the algse, and very similar to plants much higher in the scale of life. Most of them are aquatic, but a few are terrestrial. Their color is almost always a bright chlorophyll green, but occasionally it is yellowish- brown or even a bright red. The Chlorophyceae increase by the ordinary processes of cell-division observed in the higher forms of plant life. The cells may separate after division, or they may remain associated in colonies or in simple or branch- ing filaments. Reproduction takes place either asexually, i.e., without the aid of fecimdation, or sexually. There is but one general method of asexual reproduction, namely, the formation within the cell of spores, which become scattered and give rise to new cells. There are three general types of sexual repro- duction. The simplest is the formation in the cells of zoospores, which become liberated and ultimately copulate with other zoospores. Two of these zoospores become attached by their ciliated ends, their contents become fused, and a zygospore results. After a period of rest zygospore may develop into a new plant, or may break up into other spores. The second type of sexual reproduction is known as conjugation. Two cells come in contact, and by means of openings in the cell-walls
325
326 THE MICEOSCOPT OF DRINKING WATEE
Spirogyra and Zygnema,
Bat rachospcrmum.
Plate D. Pholomicrographs of Microscopic Organisn
CHLOROPHYCE-fi 327
their contents become fused. A zygospore (sometimes two) is formed, which, after a period of rest, gives rise to new plants. The highest form of sexual reproduction takes place by the formation of a rather large female oospore, which becomes fertilized by small male cells or spermatozoids. This mode of reproduction is analogous to that observed in the higher plants. Many of the Chlorophyceae exhibit the phenomenon of " alternation of generations," by which is meant the con- tinued propagation of the plants by asexual processes with occasional intervention of the sexual processes.
ORDER I. PROTOCOCCOIDEiE
Unicellular plants. Cells single or associated in families; tegument involute or naked; no branching or terminal vege- tation. This order includes many of the free-floating green algae that are found in water.
Family Palmellace-*. — Cells solitary or in families, often embedded in a jelly and forming an amorphous stratum. Multiplication by cell- division. Reproduction asexual, by active gonidia.
Qloeocystis.
Cells globose or oblong, single or in globose families of 2-4-8 cells. Common and individual lamellose gelatinous integuments. Division in alternate directions. Reproduction by zoogonidia. There are several species. The size of the cells varies from 2 to 12 ti'm diameter and the colonies from 10 to 100 m- Color green, sometimes reddish. Gelatinous tegimient colorless or ochraceous. Usually fixed, some- times free-floating. (PI. V, Fig. 10.)
Palmella
Cells globose, oval, or oblong, surrounded by a thick confluent tegument; forming an amorphous thallus. Multiplication by alternate division of the cells in all directions. An uncertain genus. Several species, usually fixc<l. Size of cells varies from i to 15 m- Thallus often large. Color generally green. (PI. V, Fig. 11.)
Tetraspora.
Cells spherical or angular, with thick teguments confluent into a homogeneous mucous; forming a sac-like thallus, sometimes of large size. The cells divide in two directions and are seen normally in groups of four. The thalli are usually fixed, but the quartettes
328 THE MICROSCOPY OF DRINKING WATER
of cells are sometimes free-floating. Several species, all green. Cells from 3 m to 12 m in diameter. (PI. V, Fig. 12.)
Botryococcus.
Cells generally oval, with a thin confluent tegument, densely packed, forming a botryoid, irregularly lobed thallus. One species, green, free-floating, with cells 10 m in diameter. (PI. VI, Fig. i.)
Raphidium.
Cells fusiform or cylindrical, straight or curved, pointed ends, occurring singly, in pairs, or in fascicles. Cell-membrane thin, smooth. Cell-contents green, granular, with transparent vacuole. Division of cells in one direction. There are several species, with numerous varieties. Two species, R. polymorphum and R. con, voltitutHy are common free-floating forms. The latter is sometimes known by the name Selenastrum. (PI. VI, Fig. 2.)
Dictyosphaerium.
Cells elliptical or kidney-shaped, with thick mucous investment, more or less confluent, arranged in globose, hollow families. The cells arc connected by delicate threads radiating from the center of the colony and attached to the concave side of the cells. The threads branch dichotomously. Division in all directions. Two or three species. The most important species is D. renijorme. Color green, and cells 6-10 X 10-20 m- (PI. VI, Fig. 3.)
Nephrocytium.
Cells oblong, kidney-shaped, with ample tegument, arranged in free-swimming colonies of 2-4-8-16 cells. Two species. Green. Cells 5X15 to 15X45 M. (PI. VI, Fig. 4.)
•
Ditnorphococcus.
Cells in groups of four on short branches, the two intermediate contiguous cells oblique, obtuse-ovate; the two lateral, opposite and separate from each other, lunate. In colonies with ceUs con- nected by threads radially arranged and unbranched. One free- floating species. Color green. Cells 5 to 10 m in diameter. (PL VI, Fig. 5.)
Family Protococcaci:^. — Cells solitary or forming more or less perfect ccenobia. Propagation by asexual zoospores or by copulation of zoogonidia. In general there is no vegetative cell -division.
Protococcus.
Cells spherical, single or in irregular clusters. CeU-membrane thin, hyaline. Cell-contents green, sometimes reddish. There is but one species, P. viridis, with many varieties. Diameter of
CHLOROPHYCEJE 329
cells varies from 3 to 50 n. They are both aquatic and aerial. Some of the aquatic forms have a gelatinous tegument and are called Chlorococcus by some writers. The distinction is a difficult one to make. (PI. \T, Fig. 6.)
Polyedrium.
Cells single, segregate, free-swimming, compressed, 3-4-8-angled. Angles sometimes radially elongated, entire or bifid, rounded at the ends. Cell-membrane thin, even. Cell-contents green, granu- lar, sometimes with oil globules. Propagation by gonidia. There are several species. One of the most common is P. longispinum. (PI. \T, Fig. 7.)
Scenedesmus.
Cells elliptical, oblong, or cylindrical, with equal or unequal ends, often produced into a spine-like horn; usually laterally united, forming ca^nobia. Cell-contents green. Propagation by segmen- tation of cell-contents into brood families, set free by rupture of the maternal cell-membrane. There are several common species, S. caudatuSj with several varieties, S. oblusuSf and S. dimorphous. The cells are usually 2 or 3 ^ in diameter and from S to 2$ n long. (PI. VI, Fig. 8.)
Hydrodictyon.
Cells oblong-cylindrictil, united at the ends into a reticulated, saccate cocnobium. Cell-contents green. Propagation by macro- gonidia which join themselves into a ca^nobium within the mother cell, and by ciliated microgonidia which copulate and form a rest- ing-spore. One species, H. ulricidatum. Aquatic and attached. (PI. \T, Fig. 9.)
Ophiocytium.
Cells cylindrical, elongated, curv-ed, or circinatc, one end and occa- sionally both ends attenuated. Cell-contents green. Propagation by zoogonidia. There are several species. The most common is O. cochleare, the cells of which are from 5 to 8 m in diameter and of various lengths. (PI. \T, Fig. 10.)
Pediastrum.
Cells united into a plane, discoid or stellate, free-swimming cocno- bium, which is continuous, or with the cells interrupted in a per- forate or clathrate manner. The central cells are polygonal and entire; those of the periphery entire, bi-lobed, with lobes some- times pointed. Cell-contents green, granular. Propagation by macrogonidia formed within the cells, which after their escape divide, arrange themselves in a single layer, and reproduce the form
324 THE MICROSCOPY OP DRINKING WATER
disposed. Spores, when present, cylindrical, generally adjacent to the basal heterocyst.
Rivularia.
Filaments radial, agglutinated by a firm mucilage, and forming well-defined hemispherical or bladdery forms. Heterocysts basal. No spores formed. Ramifications produced by transverse division of the trichomes. Color greenish to brownish. Sheaths usually distinct. Several spedes, terrestrial and aquatic. Occadonally found free-floating. (PL V, Fig. 9.)
REFERENCES (See pages 340 and 393.)
CHAPTER XXra
CHLOROPHYCEiE
The plants belonging to the Chlorophyceae are characterized by the presence of true chlorophyll, a nucleus, starch-grains, and often by a cell-wall made of cellulose. They are " algse '* in the strictest sense of the term. They cover a great range of complexity. Some of them are minute, unicellular forms scarcely distinguishable from the Cyanophyceae; others resemble the Protozoa; while others are large, branching, multicellular forms doubtfully included among the algse, and very similar to plants much higher in the scale of life. Most of them are aquatic, but a few are terrestrial. Their color is almost always a bright chlorophyll green, but occasionally it is yellowish- brown or even a bright red. The Chlorophyceae increase by the ordinary processes of cell-division observed in the higher forms of plant life. The cells may separate after division, or they may remain associated in colonies or in simple or branch- ing filaments. Reproduction takes place either asexually, i.e., without the aid of fecundation, or sexually. There is but one general method of asexual reproduction, namely, the formation within the cell of spores, which become scattered and give rise to new cells. There are three general types of sexual repro- duction. The simplest is the formation in the cells of zoospores, which become liberated and ultimately copulate with other zoospores. Two of these zoospores become attached by their ciliated ends, their contents become fused, and a zygospore results. After a period of rest zygospore may develop into a new plant, or may break up into other spores. The second type of sexual reproduction is known as conjugation. Two cells come in contact, and by means of openings in the cell-walls
325
330 THE MICROSCOPY OF DRINKING WATER
of the mother plant. There are several species. The most common are P. Boryanum and P. simplex, (PI. VI, Fig. ii.)
Sorastrum.
Cells wedge-shaped, compressed, sinuate, emarginate, or bifid at the apex; radially disposed, forming a globose, solid, free-swinmiing ccenobium. There is but one species, S. spinulosum. The cells are spined. They vary in size from 1 2 to 20 /i. The coenobia vary in diameter from 25 to 75 m. (PI. VI, Fig. 12.)
Ccelastrum.
Cells globose, or polygonal from pressure, forming a globose, hollow ccenobium, rcticulately pierced. The cells are arranged in a single layer, sometimes joined by radial gelatinous cords. Cell-contents green. Propagation by macrospores. There are several species. The most common is C. microsporum^ which has 8-16-32 cells, and the diameter of which varies from 40 to 100 m. (PI- VII, Fig. i.)
Staurogenia.
Cells oblong-oval, subquadratc, or rhomboidal, arranged in groups of 4-8-16, forming a cubical ccenobium, hollow within. Cell- contents green. Propagation by quiescent gonidia. (PI. VII, Fig. 2.)
ORDER n. VOLVOCINIEiE
Unicellular plants occurring as mobile, globose, sub- globose, or flattened quadrangular coenobia composed of bi-ciliated green cells which are more or less spherical or com- pressed. The cccnobia as a whole are motile because of the ciliated cells, and hence are free-floating. The ccenobium sometimes has an ample hyaline tegument. Cell-contents green. Propagation sexual or asexual. Asexual propagation takes place by subdivision of the larger vegetative cells into new families, which separate from the mother cell when suflS- ciently developed. Sexual propagation takes place by means of female spore cells, or oospores, developed from the vegetative cells, which are fertilized by antheridia developed from other vegetative cells. The antheridia, after escaping from the cell in which they are formed, perforate the membrane of the oogonia, after which the oospore goes into a resting state to
CHLOROPHYCE^ 331
germinate later. This order is frequently referred by zool- ogists to the Protozoa.
Faioly Volvocacels. — Characteristics the same as for the order.
Volvox.
Large coenobium, continually rotating and moving, looking like a hollow globe comi)osed of very numerous cells (several thousand) arranged on the periphery at regular distances, connected by a matrical gelatin which has the appearance of a membrane in which the ceUs are embedded. Cells globose, bearing two cilia that extend beyond the gelatinous envelope. By the waving of these cilia the colony is kept in motion. Cell-contents green; starch-granules and often a red pigment-spot present. With a high power the cells are seen to be connected to each other in a hexagonal manner by fine threads. Propagation sexual and asexual, as described under the order. The oospores and antheridia are enclosed in flask-like cells extending inward. The spermatozoids are spindle-shaped and fur- nished with two cilia. The resting-spores usually produce eight zoo- gonidia. Asexual propagation takes place by division of the larger and darker flask-like cells. These, usually eight in number, develop yoimg volvoces in the mother cells. They are very conspicuous. The mother cell splits along well-defined lines and the young forms are set free. There is practically but one species, V. globalar. The ccenobia are often one millimeter in diameter. (PI. VII, Fig. 3.)
Eudorina.
Ccenobium oval or spherical, involved in a gelatinous mucilaginous tegument, composed of 16-32 cells arranged around the colorless sphere at equal distances. The coenobium is often seen moving with a rolling motion. Cells globose, with two protruding cilia. Cell-contents green, sometimes with a red pigment-spot. Asexual propagation takes place by the division of the cells into 16-32 parts, each of which produces a new coenobium. Sexual propagation as described for the order. Usually four of the thirty-two cells pro- duce antheridia, the others oogonia. The spermatozoids are pear- shaped and are bi-ciliated. There are but two species, E. eleganSf and E. stagnak. The cells vary from 5 to 25 ju, and the cocnobia from 25 to 150 /I, in diameter. (PI. VII, Fig. 4.)
Pandorina.
Coenobium globose, invested by a broad, colorless, gelatinous tegument, composed of 8 to 64 cells crowded together or aggregated in a botryoidal manner. (In this respect it differs from Eudorina.) Cells green, globose or polygonal from compression, bi-ciliated,
332 THE MICROSCOFY OF DRINKING WATER
occasionally with a red pigment-spot. Sexual propagation takes place by the conjugation of zoospores produced in the cells of the coenobium, which after union give rise to resting-spores. Aseinial propagation takes place by cell-division. There is but one spedes, P. morum. The coenobium is about soo m in diameter and the cells from lo to 15 M. (PI. VII, Fig. 5.)
Qonium.
Coenobium quadrangular, tabular, with rounded angles, formed from a single Hat stratum of cells, girt by a broad, hyaline, plane- convex tegument. Cells 16 (4 central and 12 peripheral), polyg- onal, connected by produced angles, and furnished with two cilia. Cell-contents green. Asexual propagation by division. Sexual propagation unknown. There is but one species, G. ptirocaU. The genus is an uncertain one. (PI. VII. Fig. 6.)
ORDER m. CONJUGATA
Unicellular or multicellular plants. The multicellular forms have no terminal vegetation and are destitute of true branches. The chlorophyll masses are arranged in plates, bands, or stellate masses. Starch-grains are abundant. Multiplication by division in one direction. Reproduction by zygospores resulting from copulation and conjugation of two cells, or by ^zygospores formed without copulation. There are two families that are very different in their general characteristics, but that agree in their mode of reproduction.
Family DESMiDiEiE. — The Desmidieaj, or Desmids, form a large, well-defined group of unicellular algaj. They are characterized by two peculiar features — by an apparent division of the cell into two symmetri- cal halves, and by the presence of projections from the surface, either inconspicuous or prolonged into spines. The cells are of various sizes and forms, often curious or ornamental, single or joined together form- ing a filament. The transverse constriction is sometimes deep, some- times slight, and occasionally absent. The cell-wall is firm, almost homy. .Some writers have imagined that it was slightly silicified. The cell is surrounded by a mucous covering and sometimes by a layer of gelatin. The cell-contents are green and granular. Starch-grains are numerous. At the ends of some of the cells there are clear spaces in which are seen granules that occasionally have a vibratory movement. Cyclosis, or a circulation of granules in the watery fluid next the cell-wall, may be observed
CHLOROPHYCKE 333
in some species. Some species of desmids exhibit voluntary movements of the entire cell. Closterium, for example, shows certain oscillations and backward and forward gliding movements, supposed to be due to the secretion of threads of mucous. Multiplication takes place by cell-division and by conjugation. In the first case the two halves of the cell stretch apart and become separated by a transverse partition; new halves ulti> mately form on each of the original halves, so that two symmetrical cells result. These afterward separate. (See PI. VIII, Fig. A.) Sexual propagation by conjugation takes place as follows: Two cells approach and each sends out a tube from its center. These tubes meet, swell hemi- spherically, and, by the disappearance of the separating wall, become united into a roimded zygospore with a thick tegument and sometimes with bristling projections. This zygospore, after a period of rest, loses its contents through a rent in the wall, and a hew cell is formed which ultimately becomes constricted and assumes the shape of the parent cell. (Sec PI. VIII, Figs. B to F.)
Some of the common genera are described below. The enormous number of species makes a detailed analysis impracticable.
Penium.
Cells straight, cylindrical or fusiform, not incised nor constricted in the middle; ends rounded. Chlorophyll lamina axillary; con- taining starch-granules. Cell-membrane smooth, finely granulated, or longitudinally striated. Individuals free-swimming or associated in gelatinous masses. (PI. VII, Fig. 7.)
Closterium.
Cells simple, elongated, lunate or crescent-shaped, entire, not con- stricted at the center. Cell-wall thin, smooth or somewhat striated. ITie chlorophyllaceous masses are generally arranged in longitudinal laminae, interrupted in the middle by a pale transverse band. At each end there is a clear, colorless, or yellowish vacuole in which minute " dancing granules " may be seen. (PI. VII, Figs. 8 to 10.)
Docidium.
Cells, straight, cylindrical or fusiform, elongated, constricted at the middle. The semi-cells are somewhat inflated at the base and are often separated by a suture. Ends rounded, truncated or divided. Transverse section circular. The chlorophyllaceous cytoplasm has a parietal or axillary arrangement. Terminal vacuoles with " dancing granules *' are observed in some species. (PI. VII, Fig. II.)
Cosmarium.
Cells oblong, cylindrical, elliptical, or orbicular, with margins smooth, dentate, or crenatc; deeply constricted; ends rounded
334 THE MICROSCOPY OP DRINKING WATER
or truncate and entire; end view oblong or oval. Chlorophyll masses parietal or concentrated in. the center of the semi-cells. Cell-walls smooth, punctate, warty, or rarely spinous. The zygo- spore is spherical, tubcrculated or spinous. (PL VII, Fig. 12, and PI. Vni, Figs. A to F.)
Tetmemorus.
Cells cylindrical or fusiform, slightly constricted in the middle, narrowly incised at each end, but otherwise entire. Cdl-wall punctate or granulate. (PI. VII, Fig. 13.)
Xanthidium.
Cells single or geminately concatenate, inflated, very deeply con- stricted; semi-cells compressed, entire, spinous, protruding in the center as a rounded, truncate, or denticulate tubercle. Cell-wall firm, armed with simple or divided spines. The zygospores are globose, smooth or spinous. (PI. VHI, Figs, i and 2.)
Arthrodesmus.
Cells simple, compressed, deeply constricted; semi-cells broader than long, with a single spine on each side, but otherwise smooth and entire. (PL VIII, Fig. 3.)
Euastnim.
Cells oblong or elliptical, deeply constricted; semi-cells emarginate and usually incised at their ends; sides symmetrically sinuate or lobcd, provided with circular inflated protuberances; viewed from the vertex, elliptical. The zygospores are spherical, tuberculose or spinous. (PL VIII, Fig. 4.)
Micrasterias.
Cells simple, lenticular, deeply constricted; viewed from front, orbicular or broadly elliptical; viewed from the vertex, fusiform, with acute ends; semi-cells three- or five-lobed; lateral lobes entire or incised; end lobes sinuate or emarginate and sometimes with angles bifid or produced. (PL VIII, Fig. 5.)
Staurastrum.
Cells somewhat similar to those of Cosmarium in front view, but angular in end view; angles obtuse, acute, or drawn out into horn- like processes. Cell-wall smooth, punctate or granular, hairy, spinulose, or extended into arms or hair-like processes. Chloro- phyll masses concentrated at the center of the semi-cells, with radi- ating margins. The zygospores are spined. (PI. VIII, Figs. 6 and 7.)
Hyalotheca.
Cells short, cylindrical, usually with a slight obtuse constriction in the middle; circular in end view. The cells are closely united
CHLOROPHYCPLE
336 THE MICROSCOPY OF DRINKING WATER
into long filaments, enclosed in an ample, colorless mucous sheath. The chlorophyll is concentrated in a mass which, in end view, has a radiate appearance. (PL IX, Fig. i.)
Desmidium.
Cells oblong-tabulate, somewhat incised; in end view, triangular or quadrangular; united into somewhat fragile filaments and sur- rounded by a colorless mucous sheath. Chlorophyll masses in each semi-cell concentrated and radiate to the angles. Zygospores smooth, globose or oblong. (PL IX, Fig. 3.)
Sphasrozosma.
Cells bi-lobed, elliptical, or compressed, deeply incised, forming filaments which are almost moniliform or pinnatifid, surrounded by a colorless or mucous sheath. Chlorophyll mass concentrated, somewhat radiate. (PI. IX, Fig. 3.)
Family ZvcNEMACEiE. — Multicellular plants, composed of cylindrical cells joined into filaments and forming an articulated simple thread. Cell-wall lamellose. Chlorophyll arranged as twin stellate nuclei, as axillary lamina?, or as spiral bands. Starch-grains, etc., conspicuous. Propagation by zygospores resulting from copulation, which takes place by the union of two filaments. The filaments come into proximity, the cells put out short processes, which unite, forming tubular passages between pairs of cells. Through these connecting tubes the cell-contents of one cell passes into and unites with the cell-contents of apother. This results in the formation of a zygospore often clothed with a triple membrane. Copulation is said to be scalariform when opposite celk of two filaments unite by ladder-like tubes, geniculate when the cells become bent and unite at the angles, and lateral when the process takes place between two adjoining cells of the same filament. The family is sometimes divided into two sections, the ZygncmifKt and Mesocarpin(P. In the second sec- tion the spore formed is not a true zygospore. It is formed by a flowing together of only a part of the cell-contents. The zygospores germinate by putting forth a single germ, which elongates by transverse division into a filament.
Spirogyra.
Cells cylindrical, sometimes replicate, or folded in at the ends. Chlorophyll arranged in one or several parietal spiral bands wind- ing to the right. Copulation scalariform, sometimes lateral. Copulating cells often shorter than sterile ones and more or less swollen. Zygospores always within the wall of one of the united cells. There are very many species, differing in size of cells, number and arrangement of spirals, replication at the end of cells, character of the zygospore, etc. (PI. IX, Figs. 4 and 5.)
CHLOROPHYCEiE 337
Zygnema.
Cells with two-axil, many-rayed chlorophyll bodies near the central cell-nucleus, containing one or more starch-granules. Copulation scalariform or lateral. Zygospore in one of the united cells. (PI. IX, Fig. 6.)
Zygogonium.
Like Zygnema, except that the zygospores are located in the con- necting tube between the united cells.
ORDER IV. SIPHONEiE.
Unicellular plants when in the vegetative state; cells tubular or utricle-shaped, often branched. Cell-contents green, granu- lar. Propagation by sexual fertilization, asexual zoospores, or by microgonidia.
Fahily VAUCHERiACEiE. — Plants consisting of elongated, robust tubular filaments, more or less branched, growing in tufts. Chlorophyll granules are evenly distributed on the inside walls of the cells, and starch- grains and oil globules are conspicuous. Sexual propagation takes place by means of oospores fertilized by sp)ermatozoids. The oogonia are lateral, sessile, or borne on a simple pedicel; the anthcridia usually develop on the same filament. Asexual propagation takes place by means of zoospores produced in a terminal sporangium. The zoospores are ciliated, but go through a resting period before germinating. Propagation also takes place by means of microgonidia produced in the vegetative cells.
Vaucheria.
The characteristics are described under the family. There are many species, aquatic and terrestrial. (PL IX, Fig. 7.)
ORDER V. CONFERVOIDEJE (NEMATOPHYCEJE)
Multicellular plants consisting of simple or branched fila- ments forming articulated threads or membranaceous thalli. Vegetation terminal, sometimes lateral. Propagation by oospores fertilized by spermatozoids, or by copulation of zoo- gonidia. In many of the genera the method of propagation is not well known. The order contains a great variety of forms, and various methods of classification have been adopted by
338 THE MICROSCOPY OF DRINKINQ WATER
diflferent writers. There are but few genera that interest the water analyst.
Family Confervacea. — Plants consisting of simple or branched filaments, with terminal vegetation, composed of elongated, cylindrical cells, rarely abbreviated or swollen. Cell-membrane sometimes lameUose. Vegetation by division in one direction.' • Propagation by zoospores.
Conferva.
Articulate threads simple; cells cylindrical, sometimes swollen; chlorophyll homogeneous. Vegetation by division. Propagation by zoogonidia. There are many common species, varying greatly in diameter of filaments. Many vegetative filaments of other plants are liable to be mistaken for Conferva. The characteristics of the genus are somewhat vague. (PI. IX, Fig. 8.)
Cladophora.
Articulate threads very much branched, the branched cells being much thinner than the primary cells. Cell-membrane thick, lamel- lose. Cells cylindrical, somewhat swollen. Cell-contents green, containing many starch-granules. Propagation by zoogonidia, which deyelop in large numbers. (PL IX, Fig. 9.)
Family (EDOGONiACEiE. — Filaments articulated, simple or branched. Cells cylindrical, terminal cells sometimes setiform. Propagation by asexual zoospores or by oospores sexually fertilized. Plants monoecious or dioecious; when dioecious the male plants are either dwarf, i.e., produced from short cells of the female plants, or elongated and independent. There are two genera, Qiklogonium and Bulbochate, each with many sp)ecies.
Family ULOTRICHE-^^. — Filaments shortly articulate, simple, free, sometimes laterally connate in bands. Cell-membrane thick and lameUose. Cell-contents at first effused, after division transmuted into gonidia. Prop- agation by ciliated macrospores which do not copulate, or by microzoo- spores which do or do not copulate.
Ulothrix.
Filaments simple, articulate. Articulations usually shorter than their diameter. Cell-membrane thin. Cell-contents green, effused or parietal, enclosing amylaceous granules. Propagation by macro- and micro-zoospores. Several common species. (PI. IX, Fig. 10.)
Family CHiETOPHORACE*. — Filaments articulate, dichotomously or fasciculately branched, accumulated in tufts in a gelatinous mucus, or constituting a filamentose or foliaceous thallus. Propagation by oospores sexually fertilized, or by zoogonidia. Monoecious or dioecious.
CHLOROPHYCEJB 339
Stigeoclonium.
Filaments articulate, with simple scattered branches. Branches similar to the stems, attenuated into a colorless bristle. Cell- membrane thin, hyaline. Cell-contents green, with chlorophyll arranged in transverse bands. Propagation by oospores or zoo- gonidia. (PI. X, Fig. 2.)
.Drapamaldia.
Filaments articulate, much branched; the main stem comparatively thick, composed of large, mostly hyaline cells, with broad, trans- verse chlorophyll bands. Many branches and sub-branches, alter- nate or opposite. The terminal cells are empty, hyaline, and often elongated into a bristle. The branch cells only are fertile. The plant is enveloped in a gelatinous covering. Propagation by rest- ing-spores or zoogonidia. There are few species. (PI. X, Fig. i.)
Chaetophora.
Filaments articulate, with primary branches radiately disposed, and secondary branches shortly articulate, and attenuated into a bristle, the whole involved in a gelatinous mass. Propagation by zoospores. (PL X, Fig. 3.)
ORDER VI. CHARACEA
The Characeae are plants which occupy an intermediate position between the algae and the higher cryptogams. Each plant consists of an assemblage of long tubular cells, having a distinct central axis, with whorls of branches projecting at regular intervals at points called " nodes." The branches are sometimes spoken of as leaves, but they are quite similar to the stem. At the lower end of the stem some of the branches (rhizoids) are root-like and serve to give attachment and stability to the plant. Reproduction takes place by a peculiar sexual process. Oospheres or archegones form at the base of the branches and are fertilized by peculiar antherozoids found near them.
There are two common genera — Nitella and Chara. In Nitella the stems and branches are simple and naked; the leaves are in whorls of 5 to 8 and without stipules; the leaflets are large and often many-celled; the sporocarps arise singly or in dusters in the forkings of the leaves, and each has a
340 THE MICROSCJOPY OF DRINKING WATER
crown of two superimposed whorls of five cells each. In Chara the stems and lower branches are usually corticated, i.e., there is a central tube surrounded by smaller tubes, sometimes spirally arranged, forming a cortex; the leaves are in whorls of 6 to 12, and usually with one or two stipules; the leaflets are always one<elled; the sporocarps arise from the upper side of the leaves, and each has a crown of one whorl of five cells. These plants exhibit beautifully the phenomenon of cyclosis, or circulation of protoplasm. Some species of Chara secrete calcium carbonate, and from this arises their popular name, " stone-worts." (PI. XIX, Fig. 8.)
REFERENCES
Cooke, M. C. i8go. Introduction to Fresh- water Mgft, with an enumeration of all the British Species. Kegan Paul, Trench, Trabner & Co., Ltd.
Cooke, M. C. 1882. British Fresh-water Algie. a vols. London: Williams & Norgate.
Cooke, M. C. 1886. British Desmids. London: Williams & Norgate.
Hassall, a. H. 1857. A History of the British Fresh-water Alge, including Desmidiesc and Diatomacee. 2 vols. London.
Oltmanns, Dr. Friedr. 1904-5. Morphologi und Biologieder Algen. Part L Special. Part II. General. Pub. by Gustav Fischer, Jena.
Ralfs, D. 1848. The British Desmidiee. London.
Stokes, A. C. Analytical Keys to the Genera and Species of the Fresh-water Algae and the Desmidiex of the U. S. Edw. F. Bigelow, Portland, Conn.
WoLLE, Francis. 1892. Desmids of the United States. 2d edition. Beth- lehem, Pa.
Wolle, Francis. 1887. Fresh-water Alge of the United States, a vols. Bethlehem, Pa.
(See also page 393.)
CHAPTER XXIV
FUNGI
Fungi are flowerless plants in which the special charac- teristic is the absence of chlorophyll and starch. Lacking these, they are unable to asshnilate inorganic matter, and consequently live a saprophytic or a parasitic existence, that is, they live upon dead organic matter or in or upon some living host. They are essentially terrestrial plants, but some of them live a sort of semi-aquatic life.
Many very different forms are included among the Fungi. On the one hand there are microscopic forms — and among them some authors include the bacteria, because they have no chlorophyll — and on the other hand there are the mush- rooms, etc., which are often of very large size. Fungi usually consists of two parts, the mycelium and the fruit. The mycelium is the vegetative portion of the plant. It is a mass of delicate, jointed, branched, colorless filaments intertwined to form a cottony or felty layer. It is the spawn of mush- rooms and the common mold or mildew seen on decaying vege- table matter. The fruit consists of certain terminal mycelium filaments erected from the general mass and bearing spore-cells of various kinds. It is by differences in the method of fruiting or reproduction that the different fungi are distinguished from each other.
The Fungi, as a class, are of little importance in water investigation. They are more often seen in sewage, and even there the niunber of important genera is small. For this reason a general classification of the Fungi is not given here, but simply a description of a few common genera.
341
342 THE MICROSCOPY OF DRINKING WATER
ORDER SACCHAROBfTCSTBS.
Saccharomyces.
Cells oval or somewhat rounded, colorless, with numerous vacuoles. They do not divide by the ordinary process of cell-division, but increase by a sort of sprouting or budding. A knob-like protuberance appears at one side of the cell; this increases in size and gradually assumes the form of the mother cell; it then separates and itself begins to bud, or it remains attached, forming a sort of irregular beading or branching. It does not develop true mycelia. It also reproduces by means of certain large cells whose protoplasm divides and forms several spores, sometimes called ascospores. There is no sexual reproduction. The Saccharomycetes are popularly called yeasts. They are well known for the alcoholic fermentation which they produce in sugar. The S. cermsia is the common beer-yeast. Its cells average about 8 m in diameter. There are other species which differ in the shape and size of the cells, in the character of the spores, in the temperature and time at which sprouting takes place, in the capacity to ferment sugars, in the time required to form ye^t-films in the fermenting liquid, etc. (PL X, Fig. 4.)
ORDER ASCOMYCETES.
Penicillium.
This is the common *' blue moid." The mycelium is composed of very many colorless, more or less branched filaments or hyphs. The fertile hyphac are erect and septate, and branch into a series of compound branches, each of which bears simple sterigmata upon which chains of oval conidia are borne. ITie most common species is P. glaucum. It has a pale bluish-green color. Its erect septate hypha; are i to 2 mm. long, bearing a minute brush-like cluster of greenish conidia 2-4 ju in diameter. (PI. X, Figs. 5 and 6.)
Aspergillus.
Mycelium as in Penicillium. Fertile hyphae unseptate, swollen at apex (columella), bearing simple flask-shaped sterigmata, with chains of elliptical or spherical conidia. Often small yellowish or reddish bodies (perithecia or sclerotia) are found upon the sterile hypha; at the base of the fertile branches. A. rcpens is a common species. ITie color is light greenish or brownish. Fertile hyphae 2-4 mm. high, 10 ti diam.; columella 10-30 n, head of conidia 100 /i, conidia 5 /x. (PI. X, Fig. 7.)
FUNGI 343
ORDER PHYCOMYCETES.
FaKILY MuCORACEiE.
Mucor.
Mycelium saprophytic or parasitic, richly branched, forming a felt-like layer. The hyphs are seldom divided by septa. Conidia formed in sporangia which are spherical and borne on erect hyphs. A common species is M. racetnostis. Its sporangia are numerous, 20-70 M in diameter, on the ends of long hyphae. The spores are smooth, spherical, 4-8 m in diameter. Secondary sporangia are sometimes seen on the main fruiting-branch. The color is whitish, and later a tawny brown. There are many other species, some of which produce alcoholic fermentation in sugar. (PL X, Fig. 8.)
Family Saprolegniace^. Ssprolegnia.
Saprophytic or parasitic on plants or animals in water, sometimes producing pathogenic conditions, as, for example, in the " salmon- disease." They are often seen on dead flies, etc. The myceHum is composed of colorless or grayish hyphae of large size attached to the subtratum by root -like processes. The hyphae are not con- stricted, as in Leptomitus. Sexual reproduction takes place by means of fertilized oospores. Asexual reproduction takes place by zoospores produced in special club-shaped zoosporanges which are borne terminally upon certain hyphae. The zoospores are numerous, sometimes in rows; they are bi-ciliatcd and motile even within the zoosporangium. After escaping from the zoosporangium they become covered with a thin membrane which they throw off before final swarming and germination. (PL XI, Fig. i.)
Achlya.
Mycelium similar to that of Saprolegnia. The zoospores are non- mctile when they escape from the zoosporangium. They arrange themselves in globular fashion outside the apex of the sporangium, assume a thin membrane, rest for a time, and ultimately escape, swim about, and germinate. (PL XI, Fig. 2.)
Leptomitus.
Hyphae long, cylindrical, deeply constricted at intervals and at the base of the branches. Near the constriction there is usually a globular body, like an oil globule. The grayish protoplasm is sometimes arranged in concentrated masses, and sometimes is uniformly distributed. The zoospores are formed in the interior of club-shaped terminal sporangia. They resemble those of Sapro- legnia. Leptomitus is often found in masses in pipes conveying sewage or on the banks of polluted streams. (PL XI, Fig. 3.)
CHAPTER XXV PROTOZOA
The Protozoa are the lowest organisms belonging to the animal kingdom. The name Protozoa was used by the early writers to describe all minute organisms, whether animal or vegetable, but of late it has come to have a more definite meaning. It is now applied to those animal forms which are unicellular or multicellular by aggregation. Structurally the Protbzoa are single cells, and where there is an aggregation of several cells each one preserves its identity. There is no differentiation, no difference in the function of the different cells. Thus, the Protozoa are definitely set off from the Metazoa or Enterozoa, which are multicellular, and which have two groups of cells, one group forming the lining to a digestive cavity and the other group forming the body-wall, which differ both in structure and in function. Most of the Protozoa are strictly unicellular.
It is extremely difficult to separate the unicellular Protozoa from the unicellular Protophyta. Theoretically there is a sharp distinction between the animal and vegetable kingdoms. Definitions may be found applicable to the higher types of life, but they overlap and become confused when applied to the lowest forms. For example, the fundamental difference between the two kingdoms is supposed to lie in the phenome- non of nutrition. Plants can take up the carbon, oxygen, hydrogen, and nitrogen from mineral matter dissolved in water — the nitrogen in the form of ammonia or nitrates, the carbon in the form of carbonic acid. Their food is in solution; hence they need no mouth or digestive apparatus. They absorb their nourishment through their entire surface.
344
PROTOZOA 345
Animals, however, cannot take up nitrogen in a lower state than is found in the albumens, nor carbon except in combina- tion with oxygen and hydrogen in the form of fat, sugar, starch, etc. The albumens and fats are not soluble in water; consequently the food of animals must consist of more or less solid particles. Animals therefore require a mouth, digestive cavity, organs for obtaining their food, etc. As albumens, fats, etc., are found in nature only as products of plant or animal life, it follows that all animal life is dependent upon vegetable or other animal life. There are, however, certain plants that live on organic matter (insectivorous plants, pitcher- plants) and even have digestive cavities, but all their relations show that they are real plants. There are other plants that are devoid of chlorophyll (Fungi), yet no one would think of calling them animals. Then there are many unicellular organ- isms that contain chlorophyll and have the vegetable, or holophytic, mode of nutrition, but that resemble the animal kingdom in other respects. Such, for example, are the Dino- flagellata and many of the green Flagellata. Because it is difficult to draw a sharp line between the vegetable and animal unicellular forms Haeckel proposed a new group, the Protista, lying between the two kingdoms. This group has been since known as the Phytozoa. The term is not used in this work but the organisms have been placed in the one or the other of the two kingdoms according to the best available authority.
The Protozoan Cell. — The protozoan cell, or the individual protozoan, is a single mass of sarcode, or protoplasm, that possesses in a general way all the properties of the proto- plasm of higher animal cells. It has a certain amount of irritability and movement, it assimilates food, it grows, and reproduces its kind. It is subject to the same chemical and physical reactions that are observed in higher forms. In size it varies from the tiniest corpuscle to a mass an inch in diameter. It is irregular in form, without a definite boundary; or it has a cell-wall and a definite symmetrical outline. Internally the cell usually contains a solid nucleus or a nuclear
346 THE MICROSCOPY OF DRINKING WATER
.MallDmona:*, ttr.
PholumitTUKraiihs of Microscopic 0
PROTOZOA 347
substance distributed through the cell and recognized by staining. It usually contains a contractile vacuole, which may be seen to expand and contract, discharging a watery or gaseous matter through the cell. There are also permanent vacuoles of watery fluid, gastric vacuoles formed by the water taken in with the food, oil globules, and solid particles of starch, chlorophyll, etc. Externally there may be a cor- tical substance — a denser layer of protoplasm giving definite shape to the cell — that is sometimes contractile. The exterior protoplasm may contain such secreted products as chitin, a nitrogenous homy matter, or cellulose, a non-nitrogenous sub- stance, forming a cell-wall, cell-cuticle, or matrix. Substances may be deposited even outside of the protoplasmic layer. If perforated they are known as shells; if closed entirely, as cysts. Cysts are usually of a homy nature and are temporary products. Extemal secretions of calcium carbonate, silicates, etc., are sometimes present.
The cell-protoplasm often exhibits certain internal flowing movements, described as the " streaming of the protoplasm.** Portions of the protoplasm often extend outward, forming processes. These are of two kinds, and the distinction between them has been used as a basis of classification. Those protozoa that have lobose, filamentous processes, known as pscudopodia, are called Myxopods; those that have motile hair-like processes, known as cilia or flagella, are called Mastigopods.
The simplest Protozoa absorb solid particles of food at any point on their surface. Digestion takes place within the cell. Protozoa higher in the scale of life have a distinct oral aper- ture through which the food enters, a sort of pharyngeal passage, and an anal aperture through which undigested por- tions of food are expelled. There is no real digestive cavity. Some Protozoa exhibit a simple kind of respiration. Experi- ment has shown that they take up oxygen and give out carbonic acid. Multiplication takes place by binary division, by encystment and spore-formation, by conjugation followed by spore-formation, or by conjugation followed by increased power of division. Strictly there is no sexual reproduction,
348 THE MICROSCOPY OF DRINKING WATER
though in certain instances there are processes corresponding to it.
Various classifications have been suggested for the Pro- tozoa. None are entirely satisfactory. Biitschli has divided the Protozoa into four classes: the Sarcoda, Sporozoa, Masti- gophora, and Infusoria. So far as fresh-water forms are con- cerned, the Sarcoda represent the Rhizopoda as described by Leidy. The Mastigophora and Infusoria are both included by the word Infusoria as used by Kent. Biitschli's classifica- tion with some modifications is given below, so far as it relates to the forms with which the water analyst is concerned. Many families and some entire orders are omitted.
CLASS RHIZOPODA.
Protozoa provided with variable, retractile root-like processes or pseudopodia; naked or enclosed in a carapace or external skeleton that is chitinous, calcareous, or siliceous; generally one and sometimes more than one nucleus; contractile vacuole present or absent.
There are five sub-classes — Lobosa, Reticularia, Heliozoa. Radiolaria, and Labyrinthulidea. The two latter are marine forms and therefore are omitted. The Lobosa and Reticularia are creeping animals; the Heliozoa are swimmers.
Sub-class Lobosa
Rhizopoda in which the '* amoeba-phase " predominates in permanence and physiological importance. Pseudopodia lobose, not filamentous, arborescent, or reticulate. A denser external layer of protoplasm usually noticed. Provided with one or more nuclei and usually with a contractile vacuole. Reproduction commonly effected by simple fission, sometimes by a kind of budding.
Amoeba.
A soft, colorless, granular mass of protoplasm; possessing extensile and contractile power; devoid of investing membrane, but having an external thickening or protoplasm; with variable, lobose, finger-
PROTOZOA 349
like processes; ingesting food by flowing around and engulfing it; the absorbed food-material (diatoms, algae, etc.) is often conspicu- ous. There are several species that vary in size and in the character of the pseudopodia. A common habitat is the superficial ooze of ponds or ditches. (PI. XI, Fig. 4.)
Arcella.
An amoeba-like organism enclosed in a chitinoid shell that is vari- able in shape, but more or less campanulate or dome-shaped, and that has a circular, somewhat concave base. When seen from above, it is disk-shaped, with a pale circular spot in the middle; when seen from the side, the upper surface is strongly convex. The shell usually has a brown color, and is sometimes smooth and sometimes hexagonally marked. The protoplasmic mass occupies the central portion of the shell, but pseudopodia project through an opening in the concave base. There are many species, differing in shape and in the marks, ridges, etc., on the shell. A. vulgaris is the most common. (PI. XI, Figs. 5 and 6.)
•
Difflugia.
Body enclosed in a spherical or pear-shaped membrane in which sand-grains, etc., are embedded. The lower part is sometimes prolonged as a neck, at the end of which is situated the mouth, through which finger-like pseudopodia may project. The surface of the shell is very rough and usually has a brownish or a gray color. Diatoms, etc., are frequently attached to the shell. The contained protoplasmic mass frequently has a green color, but the pseudopodia are colorless. There are several species, varying in shape and size. The diameter of Difflugia shells varies from 35 to 300 M. (PI. XI, Fig. 7.)
Sub-class Reticularia
Rhizopoda covered with a secreted shell-like membrane with agglutinated particles of lime or sand. The projected pseudopodia are not finger-like, as in the Lobosa, but thread- like and delicately and acutely branched. The external denser layer of protoplasm is not as well marked as in the Lobosa. The shell is sometimes perforated by apertures.
Euglypha. *
Body enclosed in a hyaline, ovoid shell, composed of regular hex- agonal plates of chitinoid membrane, arranged in alternating longi- tudinal series. At the mouth the plates form a serrated margin. The upper portion of the shell is spmetimes provided with spines.
350 THE MICROSCOPY OP DRINKING WATER
The protoplasm is almost entirely enclosed by the shell; the pseudo- podia are delicate and branched. There are several ^)ecies. (PL XI, Fig. 8.)
Trinema.
Body enclosed in a hyaline, pouch-like shell, with long axis inclined or oblique, and with mouth subterminal. Dome rounded; mouth inverted, circular, beaded at border. Pseudopodia as in Euglypha, but fewer in number. The two genera are quite similar, but Tri- nema is usually much smaller. One species. (PL XI, Fig. 9.)
Sub-class Heliozoa
Rhizopoda generally spherical in form, with niimerous radial, filamentous pseudopodia, which ordinarily exhibit little change of form, though they are elastic and contractile. Pro- toplasm richly vacuolated. One or more nuclei and contractile vacuoles. Chlorophyll grains sometimes present. Skeleton products sometimes present. The Heliozoa are generally found in fresh water. They are closely related to the marine Radiolaria.
Actinophrys.
A spherical mass of colorless protoplasm seemingly filled with small bubbles, with numerous long, fine rays springing from all parts of the surface. Contractile vesicle large and active. The organism moves with a slow gliding motion. It feeds on smaller protozoa, alga-spores, etc. The most important species is A. sol, otherwise known as the " sun-animalcule." It is very common in swamp water. (PI. XI, Fig. 10.)
Heterophrys.
Like Actinophrys in general form, but with the body enveloped with a thick stratum of protoplasm defined by a granulated or thickly villous surface and i)cnetratcd by the pseudopodal rays.
CLASS MASTIGOPHORA
Protozoa bearing one or more lash-like flagella, occasionally supplemented by cilia, pseudopodia, etc. With an indistinct, diflfuse, or definite ingestive system, and usually with one or more contractile vesicles. Multiplication takes place by fission and by sporulation of the entire body mass, the process often being preceded by conjugation of two or more zooids. The
PROTOZOA 351
term Flagellata is used by some writers to describe this class of Protozoa.
Sub-class Flagellata
Nucleated cells, with a definite, corticate, external layer of protoplasm and provided with one or more vibratile flagella. Food commonly ingested through an oral aperture in the cortical protoplasm, though some genera contain chlorophyll and are sustained by nutritional processes resembling those of plants. In some genera the cuticle is developed into stalks or collar-like outgrowths. Others produce chitinous shells or masses of jelly and are connected into arborescent or spherical colonies. Food-particles, starch-gains, chromatophore and chlorophyll corpuscles, oil globules, pigment-spots (eye-spots) are often observed in the protoplasm of the cell.
The flagella of the Flagellata offer an interesting study. They are essentially different from cilia in their movement. Cilia are simply alternately bent and straightened. Flagella exhibit lashing movements to and fro and also throw them- selves into serpentine waves. There are two kinds of flagella, distinguished by their movement — pulsella and tractella. The former serve to drive the organism forward in the manner of a tadpole's tail. These are never found on the Flagellata. The tractellum is carried in front of the body and draws the organism after it, as a man uses his arms in swimming. The flagella of the Flagellata are always tractella.
ORDER MONADINA
Small, simple Flagellata, often naked or amoeboid, usually colorless, seldom with chromatophores. With a single, large, anterior flagellum or sometimes with two additional flagella. Mouth area often wanting, never produced into a well-developed pharynx.
Family Cercomonadina.
Cercomonas.
Animalcules frec-swimming, ovate or elongate, plastic, with a single long flagellum at anterior extremity and a caudal filament
352 THE MICROSCOPY OP DRINKING WATER
at the opposite extremity; no oral aperture. There are several species. Their length varies from lo to 35 91. (PI. XII, Fig. i.)
Family Heteromonadina.
Monas.
Very minute, free-swimming animalcules, colorless, globose or ovate, plastic, with no distinct cuticle; flagellum single, terminal; no distinct mouth. Several species, commonly foimd in vegetable infusions. Their length varies from 2 to 10 m* They move with a " swarming " motion. (PI. XII, Fig. 2.)
Anthophysa.
Animalcules colorless, obliquely pyriform, attached in spherical clus- ters to the extremities of slightly flexible, granular, opaque, more or less branching pedicles; two flagella, one longer than the other; no distinct mouth. In the common species, A. vegetans, the pedicle is dark brown and longitudinally stnated. The detached stems somewhat resemble Crenothrix when observed with a low power. 2^ids about 5 m long; clusters 25 n in diameter. Common in swamp water. (PL XII, Fig. 3.)
ORDER EUGLENOIDEA
Somewhat large and highly developed monoflagellate forms, with firm, contractile, elastic cortical substance; some forms are stiff, others are capable of annular contraction and worm-like elongation. At the base of the flagellum there is a mouth leading into a pharyngeal tube, near which is a con- tractile vacuole. Rarely with two flagella.
Family CiELOMONADiNA.
Coclomonas.
Animalcules free-swimming, monoflagellate, highly contractile and variable in form, with distinct oral aperture and a spheroidal pharyn- geal chamber; nucleus and contractile vacuole conspicuous; no trichocysts; with innumerable green chlorophyll granules. Nutri- tion largely vegetal. One species. Length about 50 /«. (PL XII, Fig. 4.)
Raphidomonas (Qonyostomum).
Animalcules free-swimming; ovate-elongate, flexible body, widest anteriorly and tapering posteriorly, two to three times as long as wide; two flagella, one of them trailing; oral aperture at anterior
PROTOZOA 353
end conducts to a conspicuous triangular or lunate pharyngeal chamber; contractile vacuole conspicuous; nucleus ovate; a brownish germ-sphere posteriorly located; many large bright green chlorophyll bodies; numerous rod-like bodies called trichocysts; oil globules often present. Length 40 to 70 n. Reproduction by spores formed in the germ-sphere. One species, R. semen. The genus Trentonia, described by Dr. A. C. Stokes, is similar to Raphi- domonas except that it has no trichocysts. (PI. XII, Fig. 5.)
Family Euglenina.
Euglena.
Free-swimnung animalcides, fusiform or elongate, exceedingly flexible in form; with highly elastic cuticle terminating posteriorly in a tail-like prolongation; cndoplasm bright green or reddish; flagellum flexible, issuing from an anterior notch at the bottom of which is the oral aperture and a red pigment-spot. There are several common species. £. viridis is the most common. It is often found in immense numbers in stagnant pools, forming a char- acteristic green or reddish scum. Length varies from 40 to 150 /*. £. aciis is an elongated form with tapering ends. It is longer than £. viridis y but less broad. It is also less variable in form. £. deses is a very long cylindrical form. (PI. XII, Fig. 6.)
Trachelomonas.
Monoflagellate animalcules, changeable in form, enclosed within a free-floating, spheroidal, indurated sheath or lorica; flagellum protruded through an aperture in the lorica. The color of the animalcule is green, with a red pigment-spot; the color of the lorica is generally a reddish-brown. There are several species. Diameter of lorica generally about 25/1. (PI- XII, Fig. 7.)
Phacus.
Free-swimming animalcules; form persistent, leaf -like, with sharp- pointed, tail-like prolongation; terminal oral aperture and tubular pharynx; flagellum long, vibratile; surface indurated; cndoplasm green, with red pigment -spot; contractile vacuole large, subspheri- cal. Length about 50 m, but quite variable. (PI. XII, Fig. 8.)
ORDER ISOMASTIGODA
Small and middle-sized forms of monaxonic, rarely bilat- eral shape. Fore end with two or more flagella. Some are colored, some colorless; naked or with strong cuticle or secret- ing an envelope. Nutrition generally holophytic (i.e. like a green plant) .
354 THE MICROSCOPY OF DRINKING WATER
Family Chrysomonadina.
Synura.
Free-swimming animalcules, united in sub^>herical social dusters, each zooid contained in a separate membranous sheath or lorica, the posterior extremities of which are stalk-like and confluent; two subcqual flagella, sometimes long; pigment-spots minute or absent; two brown color-bands produced equally throughout the length of the two lateral borders; a vacuolar space at the anterior extremity and several contractile vacuoles; oil globules often observed. Length of individual 2sooids about 35 m; diameter of clusters varies from 30 to 100 m- There is one species, S. uteUa, with several varieties. The colonies move with a brisk rolling motion, caused by the combined action of the flagella. Common in swamp waters. (PI. XII, Fig. 0.)
Uvella.
An uncertain genus. Uvella differs from Synura in the non-pos- session of a separate investing membrane or lorica and by the poste- rior location of the contractile vacuole. There are usually few zooids in the cluster. (PI. XII, Fig. 10.)
Syncrypta.
Free-swimming animalcules, united into spherical clusters as in Synura, without lorica, but with the entire colony immersed within a gelatinous matrix, beyond the periphery of which the fiagella alone i)roject; two subequal flagella; brownish lateral color-bands evenly developed; one or two pigment -spots; contractile vacuole between the color-bands. Length of zooids about 10 a*. Diameter of colony about 50 /n, including gelatinous zoogloca. There is but one species, S. volvox. It resembles Synura. It is not common. (PI. XII, Fig. II.)
Uroglcna.
Animalcules forming almost colorless spheroidal colonies barely visible to the naked eye. The matrix of the colony is a trans- parent gelatinous shell filled w^ith a watery substance. The zooids are embedded on the periphery, with their flagella extending out- ward and by their vibration causing the colony to revolve. The zooids are pyriform, with anterior border rounded and truncated, tapering posteriorly and sometimes continued backward as a con- tracile thread; with two light yellowish-green pigment -bands; one eye-six)t at the base of the flagella; two unequal flagella; one or more contractile vacuoles; oil globules and a large amylaceous body often present. Length of zooids is about 6 to 12 /x. The colonies are from 200 to 500 m in diameter. There are several
PROTOZOA 355
rather indistinct species. The zooids multiply by division into twos or fours. The colonies also divide, a hollow first appearing on one side, followed by a rounding at the two poles and a sub- sequent twisting apart. The Uroglena colonies are very fragile. (PI. XII, Figs. 12 and 13.)
Dinobyron.
Animalcules with urn- or trumpet-shaped loricae attenuated pos- teriorly and set one into another so as to form a compound branch- ing polythecium. The zooids are elongate-ovate, attached to the bottom of the lories by transparent elastic threads; two unequal flagella; two brownish or greenish lateral color-bands; a conspic- uous pigment-spot; nucleus and contractile vacuole sub-central. The polythecium is constructed through the successive terminal gemmation of the zooids. Length of separate loricas 15 to 60 m* The polythecium may contain from 2 to 500 loricae. The usual number is between 25 and 50. Reproduction takes place by spore- formation. The spores sometimes remain attached to the poly- thecium, or they may become scattered. When free they are liable to be mistaken for small Cyclotella. The spores are from 8 to 20 m in diameter. There are several species. D. sertularia is the most common. (PL XIII, Fig. i.)
Cryptomonas.
Free-swimming animalcules, illoricate, but persistent in form, ovate or elongate, compressed asymmetrically; flagella two, long, equal in length, issuing from a deep groove or furrow; large oral aperture at the base of the flagella continued backward as a tubular pharynx; two lateral bright green color-bands; conspicuous nucleus and contratilc vacuole; oil-globules often present. Length from 40 to 60 M. (PL Xm, Fig. 2.)
Mallomonas.
Free-swimming animalcules, oval or elliptical, persistent in shape; surface covered with overlapping homy plates from which arise long hair-like setae; under low power the surface has a crenulated appearance. One long, slender anterior flagellum; indistinct contractile vacuole. Endoplasm vacuolar, greenish or yellowish. Length from 20 to 40 >. (PI- XIII, Fig. 3.)
Family Chlamydomonadina. — ^This family is often referred to the vegetable kingdom.
Chlamydomonas.
Animalcules ovate, with two or more flagella, one large green color- mass, a delicate membranous shell, usually with a pigment-spot
356 THE MICROSCOPY OF DRINKING WATER
and one or more contractile vacuoles. The protoplasm divides into new individuals within the envelope. Length from lo to 30 11. (PI. XIII, Fig. 4.)
Family Volvocina.— Often included imder Protozoa. See page 193-
Sub-class Choanoflagellata
Mastigophora provided with an upstanding collar sur- rounding the anterior pole of the cell, from which the single flagellum springs. (Omitted from this work.)
Sub-class Dinoflagellata
Mastigophora are characterized by the presence of a longi- tudinal groove, marking the anterior region and the ventral surface, and from which a long flagellum projects. In every genus but one there is also a transverse groove in which lies horizontally a second flagellum, at one time mistaken for a girdle of cilia. The animalcules are bilaterally asymmetrical. They are occasionally naked, but most genera are covered with a cuticular shell of cellulose, either entire or built of plates. The endoplasm contains chlorophyll, starch-granules, and a brown coloring matter similar to that of diatoms. The nucleus is large and branching. There is no contractile vacuole. Multiplication takes place by transverse binary fission.
Because of the presence of the cellulose shell, chlorophyll, starch-granules, and a holophytic (vegetal) mode of nutrition the Dinoflagellata are often classed in the vegetable kingdom. Many of the Dinoflagellata are marine forms. Some are phosphorescent.
Peridinium.
Free-swimming animalcules enclosed within a cellulose shell com- posed of polygonal facets. With a high power the facets exhibit a delicate reticulation. A transverse groove divides the body into two subequal parts. A second groove extends from the first toward the apical extremity. Two flagella, one in the trans- verse groove, the other proceeding from the junction of the two grooves. Color yellowish green or brown. There are one or more
PROTOZOA 357
pigment-spots. Length from 40 to 75 n. There are several species. P. tahulatum is the most common. (PI. XIII, Fig. 5.)
Ceratium.
Free-swimming animalcules enclosed within a shell consisting of two subequal segments, one or both of which are produced into conspicuous horn-like prolongations, often covered with tooth-like processes. There is a central transverse furrow and a second groove extending from the center of the ventral aspect toward the anterior pole. Two flagella, one of which lies in the transverse groove. The brown color is not as marked as in Peridinium. Length from 25 to 150 M. There are several species, varying considerably in the character of the horn-like projections. (PL XIII, Fig. 6.)
Qlenodinium.
Free-swinuning animalcules covered with a smooth, cellulose shell not made up of facets, consisting of two subequal parts. There is a conspicuous transverse groove and a much less conspicuous secondary groove. Two typical flagella. Body ovate. Color brownish. Pigment-spot sometimes present. Length about 40 to 55 M. Glenodinium is often surrounded by a wide, irregular mass of jeUy. (PI. XIII, Fig. 7.)
Oymnodinium.
Quite similar to Peridinium, but without a protecting shell.
Sub-class Cystoflagellata Marine forms.
CLASS INFUSORIA
In its broadest sense the word Infusoria includes all the Protozoa except the Rhizopoda and Sporozoa. As used here* following Biitschli, it includes only the Ciliata and Suctoria.
Sub-class Ciliata
Protozoa of relatively large size, furnished with cilia, but not with flagella. The cilia occur as a single band surround- ing the oral aperture or are dispersed over the entire body. Modification of the cilia into setae or styles is sometimes observed. There is generally a well-developed oral and anal aperture. The nucleus varies in different genera. Besides one larger, oblong nucleus a smaller one (paranucleus) is often
358 THE MICROSCOPY OF DRINKINa WATER
present. One or more contractile vacuoles present. They all possess a delicate but well-defined ectoderm, elastic, but constant in form. They occur naked or enclosed in homy or siliceous shells or in gelatinous envelopes. Some genera are stalked. Multiplication takes place by transverse fission. Conjugation has been observed, but the part that it plays in the life-history is not well known. Many of the Ciliata are parasites in higher animals.
The Ciliata are divided into four orders according to the character and distribution of their cilia.
ORDER HTPOTRICHA
Ciliata in which the body is flattened and the locomotive cilia are confined to the ventral surface, and are often modified and enlarged to the condition of muscular appendages. Usually an adoral band of cilia, like that of Heterotricha. Dorsal surface smooth or provided with tactile hairs only. Mouth and anus conspicuous.
Euplotes.
Animalcules frcc-swimming, cncuirassed, elliptical or orbicular, with sharp laminate marginal edges, and usually a plane ventral, and convex, sometimes furrowed, dorsal surface. Peristome-field arcuate, extending backward from the frontal border to or beyond the center of the ventral surface, sometimes with a reflected and ciliale inner border. Frontal styles six or seven in number; three or more irregularly scattered ventral styles, and five anal styles; four isolated caudal styles along the posterior margin. Endoplast linear. Single spherical contractile vesicle near anal aperture. Length about 125 fi. (PI. XIII, Fig. 8.)
ORDER PERITRICHA
Ciliata with the cilia arranged in one anterior circlet or in two, an anterior and a posterior; the general surface of the body destitute of cilia. The Peritricha are sometimes divided into two suborders, the free-swimming forms and the attached forms.
Halteria.
Animalcules free-swimming, colorless, more or less globose, ter- minating posteriorly in a rounded point. Oral aperture terminal,
PROTOZOA 359
eccentric, associated with a spiral or subcircular wreath of large cirrose cilia. A zone of long hair-like setae or springing-hairs de- veloped around the equatorial region, the sudden flexure of which appendages enables the organism to progress through the water by a series of leaping movements, in addition to their ordinary swimming motions. Length 15 to 30 m* There are several species, some of them colored green. (PI. XIII, Fig. 9.)
Vorticella.
Animalcules ovate, spheroidal, or campanulate, attached pos- teriorly by a simple undivided, elongate and contractile, thread- like pedicle; the pedicle enclosing an elastic, spirally disposed, muscular flbrilla, and assuming suddenly on contraction a much- shortened and usually corkscrew-like contour. Adoral system consisting of a spirally convolute ciliary wreath, the right limb of which descends into the oral cleft, the left one obliquely elevated and encircling the ciliary disk. The entire adoral wreath con- tained within and bounded by a more or less distinctly raised border — the peristome — between which and the elevated ciliary disk, on the ventral side, the widely excavated cleft or vestibulum is situ- ated. The vestibulum is continued further into a conspicuous cleft- like pharynx, and terminates in a narrow tubular oesophagus. Anal aperture opening into the vestibulum. Contractile vesicle single, spherical, near the vestibulum. Nucleus elongate. Multipli- cation by longitudinal fission, by gemmation, and by the develop- ment of germs. There exists a very large number of species, vary- ing considerably in size and shape. The length varies from 25 to 200 M* Vorticella are often found floating in water attached to masses of Anabxna, etc. (PL XIII, Fig. 10.)
Zoothamnium.
Animalcules structurally identical with those of Vorticella, ovate, pyriform, or globular, often dissimilar in shape and of two sizes, stationed at the extremities of a branching, highly contractile pedicle or zoodendrium. Numerous species.
Epistylis.
Animalcules campanulate, ovate, or pyriform, structurally similar to Vorticella, attached in numbers to a rigid, uncontractile, branch- ing, tree-like pedicle or zoodendrium; the zooids usually of sinular size and shape. Numerous species. (PI. XIII, Fig. 11.)
ORDER HETEROTRICHA
Ciliata possessing two distinct systems of cilia, one a band or spiral or circlet of long cilia developed in the oral region,
360 THE MICROSCOPY OF DRINKING WATER
the other composed of short, fine cilia covering the entire body. The cortical layer is usually highly differentiated.
Tintinnus.
Animalcules ovate or pyriform, attached posteriorly by a slender retractile pedicle within an indurated sheath or lorica. The shape of the lorica is generally cylindrical; it is free-floating; it is some- what mucilaginous and attracts to its outer surface foreign pMutides, such as grains of inorganic matter, diatom-shells, etc. The peris- tome-fleld of the organism occupies the entire anterior border, drciunscribed by a more or less complex circular or spiral wreath of long powerful, cirrose cilia, the left limb or extremity of which is spirally involute and forms the entrance to the oral fossa. This fossa is continued as a short, tubular pharynx. Anus posteriorly situated, subterminal. Cuticular cilia very fine, distributed evenly throughout, clothing both the body and the retractile pedicle. Length of lorica 80 to 150 m- There are many species, varying greatly in the size and shape of the lories. In the fresh-water forms the lorica is generally cylindrical. Another genus, Tintinnidium, varies from Tintinnus only in having a more mucilaginous sheath and in being permanently attached to foreign objects. (PI. XUI, Fig. 12.)
Codonella.
Animalcules conical or trumpet-shaped, solitary, free-swimming, highly contractile, inhabiting a helmet- or bell-shaped lorica, to which they are attached by their posterior extremity. The anterior region truncate or excavate, forming a circular peristome having an outer fringe of about twenty long, tentacle-like cilia, and an inner collar-like border, or frill, which bears an equal number of slender, lappet-like appendages. Entire cuticular surface clothed with fine, vibratile cilia. Lorica not perforated, of chitinous con- sistence, often of a brown color, sometimes sculptured or mixed with foreign granular substances. Length of lorica 50 to 150 /*. Several species, mostly marine. (PI. XIV, Fig. i.)
Stentor.
Animalcules sedentary or free-swimming at will; bodies highly elastic and variable in form; when swimming and contracted, clavatc, pyriform, or turbinate; when fixed and extended, trumpet- shaped, broadly expanded anteriorly, tapering ofif and attenuated toward the attached posterior extremity. Peristome describing an almost complete circuit around the expanded anterior border, its left-hand extremity or limb spirally involute, forming a small pocket-shaped fossa conducting to the oral aperture, the right-
PROTOZOA 361
hand Hmb free and usually raised considerably above the opposite or left-hand one. Peristomal cilia cirrose, very large and strong; dlia of the cuticular surface very fine, distributed in even longi- tudinal rows, occasionally supplemented by scattered hair-like setae. Nucleus band-like, moniliform, or rounded. Contractile vesicle complex. Multiplication by oblique fission and by germs separated from the band-like endoplast. There are many spedes some of hrgc size, colorless, or greenish, bluish, brownish, etc. (PI. XIV, Fig. 2.)
Buraaria.
Animalcules free-swimming, broadly ovate, somewhat flattened on one side, anteriorly truncate. Peristome-field pocket-shaped, deeply excavate, situated obliquely on the anterior half of the body, having a broad oral fossa in front, and a deft -like lateral fissure, which extends from the left corner of the contour border to the middle of the ventral side; no tremulous flap. Pharynx long, funicular, bent toward the left, and forming a continuation of the peristome excavation. Adoral dliary wreath broad, much con- cealed, lying completely within the peristome-cleft. Cuticular dlia fine, in longitudinal rows. Anus posteriorly situated, terminal. Nucleus band-like, curved, or sinuous. Contractile vesicles distinct, usually multiple. Few species. length 300 to 500 m- (Pi. XIV, Fig. 3.)
ORDER HOLOTRICHA
Ciliata with but one sort of cilia, these covering the body uniformly and almost completely. A variously modified extensile or undulating membrane sometimes present. Oral and anal orifices usually conspicuous. Trichocysts sometimes present in the cuticular layer.
ParamaM:ium.
Animalcules free-swimming, ovate or elongate, asymmetrical, more or less flexible, but persistent in shape. Finely ciliated throughout the cilia of the oral region not differing in size or character from those of the general surface of the body. An oblique groove devel- oped on the ventral surface, at the posterior extremity of which is situated the oral aperture. Cortical layer usuaUy enclosing trichocysts. Contractile vesicles and nucleus conspicuous, the former sometimes stellate. There are several species. The most important is P. aurelia^ which is often found in sewage-polluted and stagnant water. It is colorless, has a length of about 225 m, and moves with a brisk rotatory motion. (PL XIV, Fig. 4.)
362 THE MICROSCOPY OF DRINKING WATER
Nassula.
Animalcules ovate, cylindrical, flexible, but not polymorphic, usually highly colored — rose, red, blue, yellow, etc. Oral aperture lateral. Pharynx armed with a simple homy tube or with a cylin- drical fascicle of rod-like teeth. Entire surface of cuticle finely and evenly ciliate. The cortical layer sometimes containing tricho- C3rsts. There are several species, varying in color, shape, and size. ' Length 50 to 250 m- (PL XIV, Fig. 5.)
Coleps.
Animalcules ovate, cylindrical, or barrel-shaped, persistent in shape, cuticular surface divided longitudinally and transversely by furrows into quadrangular facets; these facets are smooth and indurated, the narrow furrows soft and clothed with cilia; the anterior margin mucronate or denticulate; the posterior extremity mucronate and provided with spines or cusps. Oral aperture apical, terminal, surrounded with cilia. Anal aperture at posterior extremity. Color gray or light brown. The most common species is C. hirtuSf which has a length of about 60 m- (PL XIV, Fig. 6.)
Enchelys.
Animalcules free-swimming, elastic, and changeable in shape, pyriform or globose. Oral aperture situated at the termination of the narrower and usually oblique truncate anterior extremity. Anal aperture at the posterior termination. Cuticular surface finely and entirely ciliate; the cilia are longer in the region of the mouth. Few species. Length about 25 to 50 ft. (PL XIV, Fig. 7.)
Trachelocerca.
Animalcules colorless, highly clastic, and changeable in form, the anterior portion produced as a long, flexible, narrow, necklike process, the apical termination of which is separated by an annular constriction from the preceding part, and is perforated apically by the oral aperture. Cuticular surface evenly and finely ciliate; a circle of larger cilia developed around the oral region. Length of extended body about 150 /u. Few species. (PL XIV, Fig. 8.)
Pleuroncma.
Animalcules ovate, colorless. Oral aperture situated in a depressed area near the center of the ventral surface, supplemented by an extensile, hood-shaped, transparent membrane or velum, w^hich is let down or retracted at will. Numerous longer vibratile cilia stationed at the entrance of the oral cavity. The general surface of the body clothed with long, stiff, hair-like seta?. The cortical layer usually containing trichocysts. Length 60 to 100 ft. Few species. (PL XIV, Fig. 9.)
PROTOZOA 363
Colpidium.
Animalcules free-swimming, colorless, kidney-shaped. Entirely ciliate. Oral aperture inferior, subterminal. Pharynx supported throughout its length by an undulating membrane which projects exteriorly in a tongue-like manner. Two nuclei, rounded, sub- central. Length 50 to 100 fi. One species. (PI. XV, Fig. i.)
Sub-class Suctoria (Tentaculifera or Acinetaria)
Protozoa with neither flagellate appendages nor cilia in their adult state, but seizing their food and effecting locomo- tion, when unattached, by means of tentacles. These are simply adhesive or tubular and provided at their distal extremity with a cup-like sucking-disk. Nucleus usually much branched. One or more contractile vesicles. Multiplication by longitu- dinal or transverse fission or by external or internal bud-forma- tion. The yoimg forms are ciliated. Most of the Suctoria are sedentary.
Acineta.
Animalcules solitary, ovate or elongate, secreting a protective lorica, to the sides of which they are adherent or within which they may remain freely suspended. Lorica transparent, triangular or urn- shaped, supported upon a rigid pedicle. Tentacles suctorial, capi- tate, distributed irregularly or in groups. There are many species. (PI. XV, Fig. 2.)
REFERENCES
BOtschli, O. 1880-2. Protozoa. In Bronn's Klasscn und Ordnungen des
Thier-Reichs. Leipzig und Heidelberg. 3 vols. Calkins, Gary N. 1901. The Protozoa. The Macmillan Co., New York. Calkins, Dr. Gary N. iooi. The Protozoa. New York. The Macmillan
Company. (A general biological treatise on this class of organisms.) Calkins, Dr. Gary N. 1909. Protozoology. New York. Lea & Febiger.
(An introduction to the study of modem protozoology.) The best general
description of the life history of these organisms. Little systematic
material. ClaparIide ET Lachmann. 1858-61. Etudes sur les Infusories. Geneve. Conn, H. W. 1905. A Preliminary Report on the Protozoa of the Fresh Waters
of Connecticut. Bulletin No. 2 of the State Geological and Natural History
Survey. DujAROiNf F. 1841. Histoire Naturelle des Infusoires. Ehrenberg, Chr. Fr. 1838. Die Infusionsthicrchen als vollkommene Organ-
ismcD.
364 THE MICROSCOPY OF DRINKINQ WATER
Engelmann, Th. W. 1862. Zur Naturgesduchte der InfusioDsthieie. Hestwig, R., und Lessek, E. 1874. Ueber Rhisopoden und denselben naht
steheiide Organismen. Archiv. f. Mikroskopisdie Anatomie. Bd. X. Supple-
mentheft. Kent, W. Saville. 1880-81. A Manual of the Infusoria. 3 vols. Loiidoo. Lankester, E. R. Protozoa. Encyc Brit., XIX. Leidy, J. 1879. Fresh-water Rhizopods of North America. U. S. Geol. Sur.
Washington. Prichard, Andrew. 1861. A History of Infusoria, including the Desmidiacec
and Diatomacec, British and Foreign. London: Whittaker & Co. Stein, F. 1859-78. Der Organismus der Infusionsthiere. 3 Bde. Stokes, A. C. 1888. A Preliminary Contribution toward a History of the
Freshwater Infusoria of the U. S. Jour, of the Trenton Nat. His. Soc., I,
Jan., 1888.
(See also page 393.)
CHAPTER XXVI
ROTIFERA
The Rotifera, or Rotatoria, comprise a well-defined group of minute multicellular animals. They are often included among the Vermes, but some of them possess characteristics that suggest the Arthropoda.
Though microscopic in size, the Rotifera are quite highly organized. They have a well-defined digestive system, includ- ing a mouth, or buccal orifice; a mastax, a peculiar set of jaws for mastication; salivary glands; an cesophagus; gastric glands; a stomach; an intestine; and an anus. There is a vascular system, a muscular system, and, it is claimed, a ner- vous system. There is a conspicuous reproductive system and both males and females are observed, although the males are rare. The transparency of most of the Rotifera renders these various organs subjects of easy investigation.
The organisms are protected by a firm, honogeneous, structureless cuticle, often hardened by a development of chitin, forming a carapace or lorica. Some genera are further protected by an exterior casing or sheath, called an " urceo- lus," which may be gelatinous and transparent, as in Floscu- laria, or covered with foreign particles or pellets, as in Melicerta.
The Rotifera are generally bilaterally symmetrical, with a dorsal and ventral surface, with definite head region and tail region, broadest anteriorly and tapering posteriorly. There are three features of the Rotifera that deserve special atten- tion, partly because they are unique, in the organisms of this group and partly because they are used as the basis of classi-
365
366 THE MICROSCOPY OF DRINKING WATER
fication. They are the ciliary wreath, the mastax, and the foot.
The ciliary wreath consists of one or more drdets of dlia springing from disk-like lobes surrounding the mouth at the anterior end. By their continual lashing they present the appearance of wheels, gi\ing to these organisn\s the name of '' wheel-animalcules." Their function is to assist in locomo- tion, to create currents in the water by which food-partides are carried into the mouth, and to conduct this food-material through the alimentary canal. The disk-like lobe bearing the cilia is known by the names of corona, trochal disk, or velum. It takes different shapes in different rotifers. Its simplest form is an oval or circle. In more complex forms it is intricately folded, as shown on PI. XVI, Figs. A to E. The ciliated wreath is often supplemented by certain projecting processes, ciliated or bearing setae or bristles.
The foot, pseudopodium, or posterior extremity of a rotifer presents several different types. It may be fleshy and trans- versely wrinkled, or hard and jointed; it may be non-retractile or retractile; often the jointed forms are telescopic; it may terminate in a sort of sucking-disk or in a ciliated expansion, or it may be furcate, or divided into toes, as shown on PI. XVI, Figs. F to I. In some species the foot is altogether lacking.
The mastax is a sort of muscular bulb forming a part of the pharynx and containing the trophi. It has an opening above from the mouth and below into the oesophagus. The trophi, or teeth, are peculiar calcareous structures. Their function is to grind the food before it passes into the stomach, and this grinding movement may be witnessed through the transparent walls of many rotifers. The trophi consist of two toothed, hammer-like bodies, or mallei, that pound on a sort of split anvil, or incus. The malleus consists of an upper part, the head or uncus, and a lower part, the handle or manubrium. The incus also consists of two parts, a sym- metrically divided upper part, the rami, that receives the blow of the malleus, and a lower part or fulcrum. The trophi
ROTIFERA 367
show great modifications in different genera in the shape and proportion of the various parts.* PL XVI, Fig. J, represents a typical form.
These three characteristics — the arrangement of the ciliary wreath, the structure of the foot, and the form of the trophi — serve as the basis for dividing the Rotifera into orders and families. The following classification is that adopted by Hudson and Gosse. Only the typical and very conmion genera are described.
ORDER RHIZOTA
Rotifera fixed when adult; usually inhabiting a gelatinous tube excreted from the skin. Foot transversely wrinkled, not contractile within the body, ending in an adhesive suck- ing-disk or cup, without telescopic joints, never furcate.
Faioly Flosculariad^. — Corona produced longitudinally into lobes bearing the setsc. Mouth central. Ciliary wreath a single half-circle above the mouth. Trophi uncinate.
Floscularia.
Frontal lobes short, expanded, or wholly wanting. Setae very long and radiating, or short and cilia-like. Foot terminated by a non-retractile peduncle, ending in an adhesive disk. Inhabiting a transparent gelatinous tube into which the animal contracts
• The following terms are used to describe the trophi (see PI. XVI, Figs. J to P) :
MaUeale. — Mallei stout; manubria and unci of neariy equal length; unci 5- to 7-toothed; fulcrum short.
SubmaUecUe. — Mallei slender; numubria about twice as large as the unci; unci 3- to 5- toothed.
FarcipilaU, — Mallei rod-like; numubria and fulcrum long; unci pointed or evanescent; rami much developed and used as forceps.
Incudate. — Mallei evanescent; rami highly developed into a curved forceps; fulcrum stout.
Uncinate, — Unci 2-toothed; manubria evanescent; incus slender.
Ramaie. — Rami subquadrate, each crossed by two or three teeth; manubria evanescent: fulcrum rudimentary.
MaUeo-ramaU. — Mallei fastened by unci to rami; manubria three loops soldered to the unci; unci 3-toothed; rami kurge, with many strix parallel to the teeth; fulcrum slender.
368 THE MICROSCOPY OF DRINKING WATER
when alarmed. There are several species, varying in length from 200 to 2500 M. (PI. XV, Fig. 3.)
Family MEUCERTADiE. — Corona not produced in lobes bearing sets. Mouth lateral. Ciliary wreath a marginal continuous curve bent on itself at the dorsal surface so as to encircle the corona twice, with the mouth between its upper and lower curves, and having a dorsal gap between its points of flexure. Trophi malleo-ramate.
Melicerta.
Corona of four lobes. Dorsal gap wide. Dorsal antennae minute. Ventral antennae obvious. Inhabiting tubes built up of pellets, length 800 to 1500 Ai. Few species. M. ringens is very common on water-plants. (PI. XV, Fig. 4.)
Conochilus.
Carona horseshoe-shaped, transverse; gap in ciliary wreath ventral. Mouth on the corona, and toward its dorsal side. Dorsal antenns ver>' minute or absent. Ventral antennae obvious. Forming free- swimming clusters of several individuals, inhabiting coherent gelatinous tubes. Length 500 to 1200 m- Two species. C. wlvox is very common. (PI. XV, Fig. 5.)
ORDER BDELLOIDA
Rotifera that swim with their ciliary wreath and creep like a leech. Foot wholly retractile within the body, telescopic, at the end almost invariably divided into three toes.
Family Philodinad.-e. — Corona a pair of circular lobes transversely placed. Ciliary wreath a marginal continuous curve bent on itself at the dorsal surface so as to encircle the corona twice, with mouth between its upper and lower curves, and having also two gaps, the one dorsal between its points of flexure, the other ventral in the upper curve opposite to the mouth. Trophi ramalc.
Rotifer.
Eyes two, within the frontal column. The most common species io R. vulgaris, which has a transparent body, smooth, and tapering to the foot. Spurs and dorsal antennae of moderate length. Length about 500 At. This was one of the first rotifers discovered. It gave its name to the entire class. (PI. XV, Fig. 6.)
ROTIFERA 369
ORDER PLOIMA
Rotifera that swim with their feet and (in some cases) creep with their toes. This is the largest and most important order of Rotifera.
Sub-order Illoricata
Integimient flexible, not stiffened to an enclosing shell. Foot, when present, almost invariably furcate, but not trans- versely wrinkled: rarely more than feebly telescopic, and partially retractile.
Family MiCROConm^. — Corona obliquely transverse, flat, circular. Mouth central. Ciliary wreath a marginal continuous curve encircling the corona, and two curves of larger cilia, one on each side of the mouth. Trophi forcipitate. Foot stylate.
Microcodon.
Eye single, centrally placed, just below the corona. One species. Length about 200 m, of which the foot is more than half. (PI. XV, Fig. 7.)
Family AsPLANCHNADiE. — Corona subconical, with one or two apices. Ciliary wreath single, edging the corona. Intestine and cloaca absent.
Asplanchna.
Corona with two apices. Trophi incudate, not enclosed within mastax. Stomach of moderate size, spheroidal. Viviparous. Several species. Very large and transparent. (PL XV, Fig. 8.)
Family SYNCHiETAD^. — Corona a transverse spheroidal segment, sometimes much flattened, with styh'gerous prominences. Ciliary wreath a single interrupted or continuous marginal curve encircling the corona. Mastax very large, pear-shaped. Trophi forcipitate. Foot minute, furcate.
Synchaeta.
Form usually that of a long cone whose apex is the foot; front furnished with two ciliated club-shaped prominences. Ciliary wreath of interrupted curves. Foot minute, furcate. Several species. Length 150 to 300 /!• (PI* XVI, Fig. i.)
370 THE MICROSCOPY OF DRINKING WATER
Family TRiARTHRADiE. — Body furnished with skipping appendages. Corona transverse. Ciliary wreath single, marginal. Foot absent.
Polyarthra.
Eye single, occipital. Mastax very large and pear-shaped. Trophi forcipitatc. Provided with two clusters of six spines on the shoulders, the spines being in the form of serrated blades. Length about 125 M. (PI. XVI, Fig. 2.)
Triarthra.
Eyes two, frontal. Mastax of moderate size. Trophi malleora- mate. Spines single, two lateral, one ventral. There are three species, dilTering chiefly in the length of the spines. In the most common species the spines are twice the length of the body. Length of body about 150 /«. (PL XVI, Fig. 3.)
Family HYDAXiNAD-fi. — Corona truncate, with styligerous promi- nences. Ciliary wreath two parallel curves, the one marginal fringing the corona and mouth, the other lying within the first, the styligerous prominences lying between the two. Trophi malleate. Foot furcate.
Hydatina.
Body conical, tapering toward the foot. Foot short and confluent with I he trunk. Eye absent. This is one of the largest of the Ploima. Length about 600 /u.
Family Notommatad^e. — Corona obliquely transverse. Ciliary wreath of interrupted curves and clusters, usually with a marginal wreath sur- rounding the nioulh. Trophi forcipitatc. Foot furcate. This family is the most typical, the most highly organized, of the Rotifera.
Diglena.
Body subcylindrical, but very versatile in outline, often swelling behind and tapering to the head. Eyes two, minute, situated near the edge of the front. Foot furcate. Trophi forcipitatc, generally protrusilc. Several species. Length 125 to 400 /«. (PI. XVI, Eig- 4-)
Sub-order Loricata
Integument stifTcned to a wholly or partially enclosing shell; foot various.
Family Rattulid^e. — Body cylindrical or fusiform, smooth, without plicaj or angles; contained in a lorica closed all around, but open at each end, often ridged. Trophi long, asymmetrical. Eye single, cervical.
ROTIFERA 371
Mastigocerca.
Body fusiform or irregularly thick, not lunate. Toe a single style, with accessory stylets at its base. Lorica often furnished with a thin dorsal ridge. Many species. (PI. XVI, Fig. 5.)
Family CoLURiDiE. — Body enclosed in a lorica, usually of firm consist- ence, variously compressed or depressed, open at both ends, closed dorsally, usually open or wanting ventrally. Head surrounded by a chitinous arched plate or hood. Toes two, rarely one, always exposed.
Colurus.
Body subglobose, more or less compresse<i. Lorica of two lateral plates, open in front, gaping behind. Frontal hood in form of a non-retractile hook. Foot prominently extruded, of distinct joints, terminated by two furcate toes. Many species.
Family Brachionidj£. — Lorica box-like, open at each end, generally armed with anterior and posterior spines. Foot very long, flexible, imi- formly wrinkled, without articulation; toes very small.
Brachionus.
Lorica without elevated ridges, gibbous both dorsally and ven- trally. Foot very flexible, uniformly wrinkled, without articulation; toes very small. Free-swimming. Many species. (PI. X\^I, Fig. I.)
Noteus.
Lorica facetted and covered with raised points; gibbous dorsally, flat ventrally. Foot obscurely jointed. Toes moderately long. Eyes wanting. Length 350 m-
Family ANUiL£ADi£. — ^Lorica box-like, broadly open in front, open behind only by a narrow slit. Usually armed with spines or elastic seta^. Foot wholly wanting.
Anuraea.
Lorica an oblong box, open widely in front, narrowly in rear; dorsal surface usually tessellated. I'hc occipital ridge always, the anal sometimes, furnished with spines. The egg after extrusion is carried attached to the lorica. Free-swimming. Length about 125 m> (PI. XVII, Figs. 2 and 3.)
Notholca.
Lorica ovate, truncate and six-spined in front, sometimes pro- duced behind; of two spoon-like plates united laterally. No posterior spines. Dorsal surface marked longitudinally with al-
372 THE MICROSCX)PY OF DRINKING WATER
ternate ridges and furrows. Expelled egg not usually carried. Free-swimming. Several species. (PI. XVII, Fig. 4.)
ORDER SCIRTOPODA
Rotifera swimming with their ciliary wreath and skipping with arthropodous limbs; foot absent. There is but one genus, Pedalion, and that is rare.
REFERENCES
BouKNE, A. C. 1886. Rotifera, in Encyc. Britan., XXI.
Delage, Y., et H£rouaro, E. 1897. Traits de Zoologie concrete. Paris.
Herrick, C. L. 1885. Notes on American Rotifera. Bull. Sci. Lab. Dennison
University, 43-62. Granville, Ohio. Hudson and Gosse. z886. The Rotifera, or Wheel-animalcules. 2 vols.
London. Jennings, H. S. 1894. The Rotatoria of the Great Lakes. Bulletin of the
Michigan Fish Commission, No. 3.
(See also page 393.)
CHAPTER XXVn CRUSTACEA
The Crustacea belong to the Arthropoda — that is, to that group of the Articulates that have jointed appendages. Most of the larger Crustacea are marine, but many of the smaller forms are foimd in fresh water. These vary in size from objects barely visible to the naked eye to bodies several centi- meters in length. The most common forms are somewhat less in size than the head of a pin.
The fresh-water Crustacea have been sometimes divided into two groups, the Entomostraca and the Malacostraca.
The Malacostraca are comparatively large forms. They include the Amphipoda, one of which is Ganunarus pulex, the " water-crab "; the Isopoda, with Asellus aquaticus, or the "water-louse"; and the Decapoda, or ten-footed animals.
The Entomostraca may be said to include most of the smaller, free-swinmiing Crustacea, but the word is sometimes used in a stricter and more limited sense. The bodies of the Entomostraca are more or less distinctly jointed, and are con- tained in a homy, leathery, or brittle shell formed of one or more parts. The shell is composed of chitin impregnated with a variable amoimt of carbonate of lime. It is often trans- parent, and may be striated, reticulated, notched, spinous, etc. It varies in structure in different genera. It may be a bivalve, like a mussel-shell, or folded so as to give the appear- ance of a bivalve without being really so, or segmented, like a lobster's shell. The body of the organism is segmented, and there is generally a cephalo-thorax region and an abdominal region. In some cases there are distinct head and tail regions. There are one or two pairs of antennae springing from near
373
374 THE MICROSCOPY OF DRINKING WATER
the head. The feet vary in number, position, and character. In some genera they are flattened and have branchiae, or breath- ing-plates, attached to them, enabling them to perform the fimction of respiration. There is one conspicuous eye, usually black or reddish, situated in the head region. Near the mouth are two mandibles, and near them are the maxillae, or foot- jaws, armed with spines or claws and sometimes with branchiae. There is a heart, often square, that causes the circulation of colorless blood; and well-marked digestive, muscular, nervous, and reproductive systems. The eggs of the Entomostraca may be seen in brood-cavities inside the shell or in exterior attached egg-sacs. The yoimg often hatch in the nauplius form, and undergo several changes before arriving at the adult condition. The Entomostraca are usually divided into four orders— Copepoda, Ostracoda, Cladocera, and Phyllopoda. The last three are sometimes placed as sub-orders under the order Branchiopoda.
ORDER COPEPODA
Shell jointed, forming a more or less cylindrical buckler, or carapace, enclosing the head and thorax. The anterior part of the body is composed of ten segments more or less fused. The five constituting the head bear respectively a pair of jointed antennae, a pair of branched antennules, a pair of mandibles, or masticatory organs, a pair of maxillae, and a pair of foot-jaws. The five thoracic segments bear five pairs of jointed swimming-feet, the fifth often rudimentary. There arc about five abdominal segments, nearly devoid of append- ages, and continued posteriorly by two tail-like stylets. Young hatched in the nauplius state.
The Copepoda move by vigorous leaps. They lead a roving, predatory life and well deserve the name of " scavengers."
Cyclops.
Copepoda with head hardly distinguishable from the body. The thorax and abdomen generally distinguishable, the former having four and the latter six segments. Two pairs of antenna*, the superior large and many-jointed, the inferior smaller, furnished with short
CRUSTACEA 376
setae; both superior antennae of the male have swollen joints. The antennae assist in locomotion. Two pairs of vigorous branched foot-jaws. One eye, large, single, central. Two egg-sacs. Cyclops are very prolific, as many as 30 or 40 ova being laid at a time and broods occurring at short intervals. The eggs may hatch after leaving the ovary. There are many species. (PI. XVII, Fig. 5.)
Diaptomus.
Copepoda resembling Cyclops in their general appearance. Thorax and abdomen each five-segmented. Antennae very long, many- jointed, with setae; the right antenna only swollen in the male. Antennules large, bifid, the two imequal branches arising from a conmion footstalk. Three pairs of imbranched foot-jaws. One egg-sac. The ova hatch while borne by the female. (PI. XVII, Fig. 6.)
Canthocamptus.
Copepoda somewhat resembling Cyclops. The ten segments of the thorax and abdomen not distinguishable. The segments de- crease in size as they descend. At the junction of the fourth and fifth segments the body is very movable. Antennae very short. Five pairs of swimming-feet, much longer than in cyclops. One egg-sac. (PI. XVII, Fig. 7.)
ORDER OSTRACODA
Shell consisting of two valves, entirely enclosing the body; from one to three pairs of feet; no external ovary.
Cypiis.
Body enclosed within a homy bivalve shell, oval or reniform. Supe- rior antennae seven-jointed, with long feathery filaments arising from the last three. Inferior antennsc leg-like, with claws and setae at the end. Two pairs of feet. Eye single. Color greenish, brownish, or whitish. A large number of species. The shell is seldom open wide. (PL XVII, Fig. 8.)
ORDER CLADOCERA
Shell consisting of two thin chitinous plates springing from the maxillary segment. The most important characteristic is the presence of several pairs of leaf -like feet provided with branchiae, or breathing-organs. There is a large single eye.
376 THE MICROSCOPY OF DRINKING WATER
Two pairs of antennae, large, branched, and adapted for swim- ming. This order contains a number of common genera.
Daphnia.
Head produced into a prominent beak; valves of the carapace oval, reticulated, and terminated below by a serrated spine. Superior antenme situated beneath the beak, one-jointed or as a minute tubercle with a tuft of setae. Inferior antenns large and power- ful, two-branched, one branch three-jointed, the other four-jointed. Five pairs of legs. Heart a colorless organ at the back of the head. Eye spherical, with numerous lenses. Ova carried in a cavity between the back of the animal and the shell. At certain seasons " winter eggs *' are produced. Daphnia move with a louse-like, skipping movement. They are sometimes called " arborescent water-fleas.'* There are numerous species. (PI. XVII, Fig. 9.)
Bosmina.
Head terminated in front by a sharp beak directed forward and downward, and from the end of which project the long, many- jointed, curved, and cylindrical superior antennae. Inferior antennae two-branched, one branch three-, the other four-jointed. Five pairs of legs. Shell oval, with a spine at the lower angle of the posterior border. Eye large. Eggs hatched in a brood-cavity at the back of the shell. (PI. XVII, Fig. 10.)
Sida.
Shell long and narrow. Head separated from the body by a depres- sion. Posterior margin nearly straight. No spine or tooth. An- tenna? large, one two-jointed, one three-jointed. Six pairs of legs. (PI. XVIII, Fig. I.)
Chydorus.
Shell nearly spherical; beak long and sharp, curved downward and for^\ar(l. Antenna; short. Eye single. Color greenish or dark reddish. Moves with an unsteady rolling motion. (PL XVIII, Fig. 2.)
ORDER PHYLLOPODA
Body with or without a shell. Legs 11 to 60 pairs; joints foliaccous or branchiform, chiefly adapted for respiration and not motion. Two or more eyes. One or two pairs of antennae, neither adapted for swimming.
Branchipus.
Body without a shell. Legs eleven pairs. Antennae two pairs, the inferior horn-like and with prehensile appendages in the male.
CRUSTACEA 377
Tan formed of two plates. Cephalic horns, with fan-shaped appen- dages at the base. Color reddish. Floats slowly on its back. (PI. XVIII, Fig. 3.)
REFERENCES
FoRDYCE, Charles. The Cladocera of Nebraska. Studies from the Zoological
Laboratory, the University of Nebraska, under the direction of Henry B.
Ward, No. 42. Hesrick, C. L. a Final Report on the Crustacea of Minnesota, included in the
orders Cladocera and Copepoda. From the Annual Report of Progress for
1883 of the Geol. and Nat. Hist. Survey of Minnesota. JuDAY, Chancey. 1904. The Diurnal Movement of Plankton Crustacea.
Transactions of the Wisconsin Acad, of Sciences, Arts and Letters. Vol.
XIV, Aug., 1904. Maksh, C. Dwight. On the Cydopids and Calanidae of Lake St. Clair. Bulletin
No. 5 of the Michigan Fish Commission. Massh, C. Dwight. On the Deep-water Crustacea of Green Lake. Wis. Acad.
Sd. Arts and Letters, VIII, 21 1-2 13. Baird, W. 1850. The Natural History of the British Entomostraca. London:
Ray Sodety. BncE, E. A. 1881. Notes on the Crustacea in Chicago Water Supply, with
Remarks on the Formation of the Carapace. Chic. Med. Journal and Exam- iner, XIV, 584-590. Chicago.
(See also page 393.)
CHAPTER XXVm BRYOZOA, OR POLYZOA
The Bryozoa, or Polyozoa, are minute animals forming moss-like or coral-like calcareous or chitinous aggregations. The colonies are called corms, polyzoaria, or coenoeda. They often attain an enormous size. In the adult stage they lead a sedentary life attached to some submerged object. The animals themselves are small, but easily visible to the naked eye. Some of them are covered with a secreted coating, or sheath, that takes the form of a narrow, brown-colored tube; others are embedded in a mass of jelly. The genera that live in the brown, homy tubes form tree-like growths that often attain considerable length. The branches are some- times an inch long, and each one is the home of an individual polyzoon, or polypid. The branches, or hollow twigs, are separated from the main stalk by partitions, so that, to a certain extent, each polypid lives a separate existence in its own little case, though each was formed from its next lower neighbor by a process of budding.
The body of the organism is a transparent membranous sac, immersed in the jelly or concealed in the brown opaque sheath. It contains a U-shaped alimentary canal, with a con- tractile oesophagus, a stomach, and an intestine; a muscular system that permits some motion within the case, and that enables the animal to protrude inself from the case and to extend and contract its tentacles; mesenteries in the form of fibrous bands; an ovary; and a rudimentary nervous system. There is no heart and no blood-vessels of any kind.
The most conspicuous part of the animal is the circlet of ciliated tentacles. They are mounted on a sort of platform,
378
BRYOZOA, OR POLYZOA 379
or disk, called a lophophore,. at the forward end of the body. This lophophore, with its crown of tentacles, may be protruded from the end of the protective tube at the will of the animal. The tentacles themselves may be expanded, giving a beautiful bell-shaped, flower-like appearance. They are hollow and are covered with fine hair-like dlia. They are muscular and can be bent and straightened at will. By their combined action currents in the water are set up toward the mouth, situated just beneath the lophophore. Minute organisms are thus swept in as food.
The Bryozoa increase by a process of budding which gives rise to the branched stalks. There is also a sexual reproduc- tion. Statoblasts, or winter eggs, form within the body and escape after the death of the animal. They are sometimes formed in such abundance as to form patches of scimi upon the surface of a pond. The various forms of these statoblasts assist in the classification of the Bryozoa.
The following are some of the important fresh-water genera. There are many marine forms.
Plumatella.
Zoary confervoid, brown-colored, branched, tubular, branches distinct. Lophophore crescent -shaped. Tentacles numerous, ar- ranged in a double row. Statoblasts elliptical, with a cellular dark-brown annulus, but no spines. (PL XVIII, Fig. 6.)
Fredericella.
Zoary tubular, branched, brown-colored. Lophophore circular. Tentacles about 24, arranged in a single row. Statoblasts elliptical or subspherical, smooth, no spines, without a cellular annulus. (PL XVIII, Fig. 4.)
Paludicella.
Zoary tubular, diffusely branched, having the appearance of brown club-shaped cells joined end to end ; apertures lateral, near the broad ends of the cells. Lophophore circular. Tentacles sixteen, arranged in a single row. Statoblasts elliptical, without spines, with a cel- lular bluish-purple annulus. (PL XVIII, Fig. 5.)
PM;tinatella.
2k>ary massive, gelatinous, fixed. Polypids protruding from orifices arranged irregularly upon the surface. Tentacles numerous. Sta-
380 THE MICROSCOPY OF DRINKINO WATER
toblasts circular, with a single row of double hooks, not forked at the tips, as in Cristatella. Common. (PI. XVIII, Fig. 7.)
CrUUtella.
2^oary a mass of jelly, the polypids arranged on the outside, and the tentacles extended beyond the surface. The jelly-mass is usually long and narrow and has the power of moving slowly, creeping over submerged objects. Tentacles numerous, pectinate upon two arms. Statoblasts circular, with two rows of double hooks having forked tips. Rare.
REFERENCES
Allman, G. J. 1856. The Fresh-water Polyzoa. Fol. London: Ray Society. Davenport, C. B. 1890. Cristatella: The Origin and Development of the
Individual in the Colony. Bull. Mus. Comp. Zool. Harvard College, XX. Hyatt, A. 1 866-1 868. Observations on Polyzoa. Proc. Essex Inst., IV and
V, Salem. Lankrsteb, E. R. Polyzoa, in Encyc. Brit. Weston, Robert Spurr. i8q8. The Occurrence of Cristatella in the Storage
Reservoir at Henderson, N. C. Jour. N. E. W. W. Assoc., XIII, Sept., i8g8.
«
(Sec also page 393.)
CHAPTER XXIX SPONGIDiE
The fresh-water sponges are not of sufficient importance in water-supplies to warrant an extended description in this work. They differ materially from the marine sponges, which make up by far the greater part of the Spongidse.
The fresh-water sponge is an agglomeration of animal cells into a gelatinous mass, often referred to as the " sarcode." Embedded in the sarcode and supporting it are minute siliceous needles, or spicules. These skeleton spicules interlace and give the sponge-mass a certain amount of rigidity. The sponge grows as flat patches upon the sides of water-pipes and conduits and upon submerged objects in ponds and streams; or it extends outward in large masses or in finger- like processes that sometimes branch. Its color when exposed to the light is greenish or brownish, but in the dark places of a water-supply system its color is much lighter and is some- times creamy white. The sponge feeds upon the microscopic organisms in water, which are drawn in through an elaborate system of pores and canals. If these pores become choked up with silt and amorphous matter the organism dies. For this reason sponge-patches are more abundant upon the top and sides of a conduit than upon the bottom.
At certain seasons the fresh-water sponges contain seed- like bodies known under the various names of gemmules, ovaria, statoblasts, statospheres, winter-buds, etc. They are nearly spherical and are about 0.5 mm. in diameter. They have a chitinous coat that encloses a compact mass of proto- plasmic globules. In this coat there is a circular orifice, known as the foraminal aperture, through which the protoplasmic bodies make their exit at time of germination. In most species
381
382 THE MICROSCOPY OF DRINKING WATER
the chitinous coat is surrounded by a '' crust " in which are embedded minute spicules, called the '' gemmule spicules/* to distinguish them from the " skeleton spicules," referred to above. There is a third kind of spicule known as the " dermal spicule " or the " flesh spicule." They lie upon the outer lining of the canals in the deeper portions of the sponge. They are smaller than the skeleton spicules and are not bound together. Dermal spicules are not found in all species.
The skeleton spicules differ somewhat in different species. They have a length of about ^50 fu They are usually arcuate and pointed at the ends. They may be smooth or covered with spines (PI. XVIII, Figs. 9). These skeleton spicules of sponge are commonly observed in the microscopical examina- tion of surface-waters. The gemmule spicules differ in char- acter in different genera and species. Their characteristics are used therefore in classifying the fresh-water sponges.
Potts has described a number of different genera of fresh- water Spongidse, among which are Spongilla, Meyenia, Hetero- meyenia, Tubella, Parmula, Carterius, etc. The first two are the most important. They are sometimes given the rank of sub-families.
The Spongilla is a green, branching sponge. The skele- ton spicules are smooth and fasciculated. The dermal spicules are fusiform, pointed, and entirely spined. The gemmule spicules are cylindrical, more or less curved, and sparsely ' spined — the spines often recurved. (PI. XVTII, Fig. 8.)
The Meyenia arc usually sessile and massive. The skele- ton spicules are fusiform-acerate, abruptly pointed, coarsely spined except near the extremities; spines subcorneal, acute. The dermal spicules are generally absent. The gemmule spicules arc irregular, birotulate, with rotules produced.
REFERENCES
BowERBANK, J. S. 1863. Monograph of the Spongillidae. Proc. Zool. Soc.
London. BowERBANK, J. S. 1864-1874. On the British Spongiadac. 3 vols. London:
Ray Soc.
SPONGIDiE 383
Kelucott, D. S. 1891. The Mills Collection of Fresh-water Sponges. Bull.
Buffalo Soc. Nat. Sc, V, 99-104. POTTSy E. 1880. Fresh-water Sponges of Fairmount Park. Proc. Acad. Nat.
Sci., Philadelphia, 330, 331. Potts, E. 1880. On Fresh-water Sponges. Proc. Acad. Nat. Sd., Philadelphia.
356, 357. Potts, E. 1883. Our Fresh-water Sponges. American Naturalist, 1 293-1 296. Potts, E. 1887. Contributions toward a Synopsis of the American Forms oP
Fresh-water Sponges, with Descriptions of those named by other authors
and from all parts of the world. Proc. Acad. Nat. Sci., Philadelphia, p.
158-279.
(See also page 393.)
CHAPTER XXX MISCELLANEOUS ORGANISMS
The miscellaneous higher animals and plants that one is likely to observe in a microscopical examination of drinking water are so varied, and they are of such little practical impor- tance in the interpretation of an analysis, that their description here is not warranted. It is sufficient to mention the names of a few common forms.
Of the Vermes the following may be noted: Anguillula, a small, colorless thread-worm like the vinegar-eel (PL XIX, Fig. i); Gordius, the common hair-snake; Nais, an annulate worm with bristles (PI. XIX, Fig. 2) ; Tubifex, another bristle- bearing worm; Chaetonotus, an elongated worm-like organ- ism with scales on its back (PI. XIX, Fig. 3). Of the Arachnida: Macrobiotus, the water-bear (PI. XIX, Fig. 4) ; and the Acarina, water-mites, or water-spiders (PI. XIX, Fig. 5). Of the Hydrozoa: the Hydra, a most interesting organism from a zoological standpoint (PI. XIX, Fig. 6). Insect larvae; Corethra, or the phantom larva; scales and fragments of insects; barbs of feathers; epithelium-cells; ova of the Entozoa, Crustacea, Rotifera, etc.
Of the vegetable kingdom may be mentioned Batrachos- permum (PI. XIX, Fig. 7); fragments of Sphagnum Moss; Myriophyllum, or water-milfoil; Cera tophy Hum, or homwort (PI. XIX, Fig. 10); Lemna, or duck-weed (PL XIX, Fig. 12); Potamogcton, or pond-weed (PI. XIX, Fig. 11); Hippuris, or marc's-tail; Anacharis, or American water-weed (PI. XIX, Fig- 9); Utricularia, an inscctij^orous plant; pollen-grains; plant-hairs; fragments of vegetable fibers and tissue; fibers of cotton, wool, silk, hemp, etc.; starch-grains, etc.
384
MISCELLANEOUS ORGANISMS 385
For the description of all these miscellaneous organisms and objects the reader is referred to more comprehensive books on zoology, botany, and general microscopy, and especially to " Fresh Water Biology," edited by Dr. Henry B. Ward and Geoige C. Whipple.
GLOSSARY TO PART II
Adoral, relating to the mouth.
Aeruginous, of the color of verdigris; blue-green.
Alate, winged.
Amylaceous, resembling starch.
Anal, relating to the anus.
Annulate, marked with rings.
Anthesidia, reproductive organs supposed to be analogous to anthers.
AscuATE, bent like a knee. ,
Articulate, composed of joints.
Bacillas, rod-like.
Bifid, two-cleft.
BntOTULATE, with two recurved rounded ends.
BoTRYOiD, clustered like a bunch of grapes.
Buccal, relating to the cheek.
Campanulate, bell-shaped.
Capitate, collected in a head.
Carapace, a hard shell.
Carinate, like a keel.
Caudal, relating to the tail.
Cervical, relating to the neck.
CmriNOUs, homy.
Ciliated, provided with cilia, or hair-like appendages.
CntaNATE, curled round, coiled, or spirally rolled up.
CiRROSE, curled as a tendril.
Clathrate, perforated or latticed like a window.
Coccus, a minute spherical form.
CcENOBiuii, a community of a definite number of individuals united in
one body. Concatenate, linked like a chain. Connate, united congenitally. Convolute, rolled together.
387
388 THE MICROSCOPY OF DRINKING WATER
Cortical, relating to the external layers.
Crenate, notched or scalloped.
CuNEATE, wedge-shaped.
Cymbiform, boat-shaped.
Cyst, a membranous sac without opening.
Dentate, toothed.
Denticulate, finely toothed.
DiCHOTOMOUs, dividing by pairs from top to bottom.
DiCEaous, the males and females represented in separate individuals.
Ectoderm, the external of two germinal ceUular layers.
Emarginate, with a notch cut out of the margin at the end.
Encuirassed, with an indurated dorsal shield.
Encysted, enclosed in a cryst or bladder.
Endochrome, the coloring matter of ceUs.
Endoplast, the nucleus of a protozoan cell.
Fasciculate, in bundles from a common point.
FiiiEORM, long, slender, thread-like.
Flagellate, provided with fiagella, or lash-like appendages.
FoLiACEOUs, resembling a leaf.
Forcipitate, like forceps.
Funicular, like a cord or thread.
Furcate, forked or divergently branched.
Fusiform, tapering like a spindle.
Gibbous, swollen, convex.
Gonidia, propagative bodies of small size not produced by act of fertiliza'
tion. IIeterocyst, interspersed cells of a special character differing from their
neighbors. HoLOPHYTic, like a plant. HoRMOGONS, special reproductive bodies composed of short chains of cells,
parts of internal filaments. Hyaline, transparent.
Hyphae, filaments of the vegetative portion of a fungus. Indurated, hardened.
Intercalated, interspersed, placed between others. Involute, rolled inward. Lamellated, lamellose, in layers. Lanceolate, lance-shaped, tapering at each end. Lenticular, like a lens.
Lophopiiore, an organ bearing tentacles, found on the Bryozoa. LoRiCA, a hard protective coat. Lunate, crescent-shaped. Macrogonidia, large gonidia. Macrospores, large spores.
GLOSSARY TO PART n 389
Matrix, the birth cavity.
MiCROGONiDiA, small gonidia.
MoNAXONic, with but one axis.
MoNiUFORM, like a necklace, contracted at regular intervals.
MoNGEaous, male and female represented in one individuaL
MucRONATE, having a small tip.
Mycelium, the vegetative portion of a fungus.
Naviculoid, boat-shaped.
OosPHERE, an ovarian sac.
Oospore, spore produced in an ovarian sac.
Oral, relating to the mouth.
Parietal, growing near the wall.
Peristome, the oral region.
PiNNATinD, shaped like a feather.
PoLYTHEdUM, an assemblage of many lories.
Punctate, studded with points or dots.
Pyriform, pear-shaped.
Reniform, kidney-shaped.
Replicate, folded back.
Reticulate, latticed.
Retractile, capable of being drawn back.
Saccate, like a bag.
Sarcode, the primary vital matter of animal cells (Protoplasm).
SCALARIFORM, ladder-like.
Segregate, set apart from others.
Septate, separated by partitions.
Setiform, in the form of a bristle.
SiGMOiDAL, S-shaped.
Sinuate, with notches or depressions.
SPERMATOZOms, thread-like bodies, motile, and possessing fecundative power.
Sporangium, sporange, a spore-case.
Sporocarp, the covering or capsule enclosing a spore.
Sporoderm, the covering of a spore.
Statoblasts, the winter eggs, or reproductive bodies of the Bryozoa and Spongids.
Striate, covered with striae.
Styugergus, bearing styles or prominences.
Sub- a prefix indicating " almost," or " neariy."
SuBORBicuLAR, almost spherical.
Thallus, a leaf-like expansion.
Trichocyst, a rod-like body developed in the cortical layer of some pro- tozoa.
Trichome, the thread or filament of filamentous algae.
390 THE MICROSCOPY OF DRINKING WATER
Turbinate, shaped like a top.
Utriculate, inflated.
Vacuolated, containing drops or vacuoles.
Vesicuuform, bladder-like.
ZooDENDRUM, a bill-like colony-stalk.
ZooGONiDiA, gonidia endowed with motion.
Zoospores, locomotive spores.
Zygospore, a spore resulting from conjugation.
TABLES AND FORMULAE
WEIGHTS AND MEASURES— CONVERSION TABLES
lb. Avoir. = 1.21$ lbs. Troy or Apoth. = 7ooo grains Troy =453.6 grams.
lb Troy or Apoth. — .823 lb. Avoir. = 5760 grains Troy ='373.2 grams.
oz. Avoir. = .960 fluid ounce =28.35 grams.
oz. Troy or Apoth. = 1.053 fluid ounces = 31. 10 grams.
grain Troy =.0648 gram.
kilogram -2.205 lbs. Avoir. = 2.679 lbs. Troy or Apoth.
gram = .035 oz. Avoir. = .032 oz. Troy or Apoth. = 15432 grains Troy.
milligram = .0x54 grain Troy.
Imperial gallon =1.201 U. S. fluid gallons- 277.4 cubic inches =4546 cubic centi- meters.
U. S. fluid gallon =.833 Imperial gallon = 231 cubic inches =3 785 cubic centi- meters.
U. S. fluid gallon =8.332 lbs. Avoir. = 10.127 lbs. Troy or Apoth.
fluid ounce = 1.042 oz. Avoir. = .949 oz. Troy or Apoih. = 29.57 cubic centimeters.
liter =.264 U. S. fluid gallon = .220 Imp>erial gallon = 21.028 cubic inches.
liter =33.82 fluid ounces= 2.205 lbs. Avoir. = 2.679 lbs. Troy or Apoth.
cubic centimeter =.033 fluid ounces. 03 5 oz. A voir. = .03 2 oz. Troy or Apoth.
inch =2.54 centimeters =25.4 millimeters.
£001 = 30.48 centimeters.
yard = 9 1. 44 centimeters =.9 144 meter.
meter =1.0936 yards =3.28 feet = 39 37 inches.
centimeter = .393 7 inch.
millimeter =.0394 inch = .442 Paris lino.
micron (ji) = .001 millimeter = Tji^Jo inch = .000039 inch = .0004 Paris line.
Paris line=.o89 inch = 2.26 millimeters— 2260.6 microns.
cubic yard = .764 5 cubic meter.
cubic foot = .0283 cubic meter= 7.481 U. S. ga!lons=6.232 Imperial gallons.
cubic inch = 16.39 cubic centimeters.
cubic meter =35.2 16 cubic feet = 1.308 cubic yards.
cubic centimeter =.66 1 cubic inch.
301
392
THE MICROSCOPY OF DRINKING WATER
TABLE FOR TRANSFORMING MICROMILLIMETERS (MICRONS)
TO INCHES.
|
Microns. |
Decimalf of an Inch. |
Practioni of an Inch. |
Microns. |
Decimals of an Inch. |
Fractions of an Indi. |
|
I |
.000039 |
1/25000 |
25 |
.000984 |
l/iooo |
|
2 |
.000079 |
1/12500 |
30 |
.001181 |
1/833 |
|
3 |
.000118 |
1/8333 |
35 |
.001378 |
1/714 |
|
4 |
.000157 |
1/6250 |
40 |
.001575 |
I /62s |
|
5 |
.000197 |
1/5000 |
45 |
.001772 |
1/533 |
|
6 |
.000336 |
I /4333 |
50 |
.001969 |
i/Soo |
|
7 |
.000276 |
1/3285 |
60 |
.002362 |
1/416 |
|
8 |
•00031S |
1/3125 |
70 |
.002756 |
1/357 |
|
9 |
•000354 |
1/2777 |
80 |
.003150 |
1/3" |
|
lO |
.000394 |
1/2500 |
90 |
•003543 |
1/277 |
|
IS |
.000591 |
1/1666 |
100 |
.003937 |
1/250 |
|
20 |
.000787 |
1/1250 |
« |
TABLE FOR TRANSFORMING CENTIGRADE TO FAHRENHEIT
DEGREES OF TEMPERATURE.
|
Centigrade. |
Pahrehheit. |
Centigrade. |
Fahrenheit. |
Centigrade. |
Fahrenheit. |
|
-17.7 |
0 |
4.0 |
39.2 |
23-8 |
750 |
|
-15.0 |
S-o |
4.4 |
40.0 |
25.0 |
77 0 |
|
— 12.2 |
10. 0 |
SO |
41.0 |
26.6 |
80.0 |
|
— lO.O |
14.0 |
7-2 |
45 0 |
29 4 |
85.0 |
|
- 9 4 |
ISO |
lO.O |
50.0 |
30.0 |
86.0 |
|
- 6.6 |
20.0 |
12.7 |
5S.O |
32.2 |
90.0 , |
|
- S-o |
23.0 |
IS 0 |
59 0 |
35 0 |
95 0 ; |
|
- 3-8 |
25.0 |
IS S |
60.0 |
37.7 |
100. 0 |
|
— I.I |
30.0 |
18.3 |
65.0 |
40.0 |
104.0 |
|
0 |
32.0 |
20.0 |
68.0 |
« |
|
|
1.6 |
3SO |
21. 1 |
70.0 |
1 |
• |
TABLE FOR TRANSFORMING STATEMENTS OF CHEMICAL
COMPOSITION.
I grain per U. S. gallon . . . I grain per Imperial gallon
I part per 100,000
I part per 1,000,000
Grains per U. S. Gallon.
0 . 830
0.58s 0.058
Grains per Imp. Gallon,
1.20 I.
0.70 0.07
Parts per 100.000.
I. 71
I 43 I.
O.IO
Parts per 1 .000.000.
17. 1
14.3 10. 0
I.
SCIENTIFIC LITERATURE
The scientific literature of fresh water micrology has become so voluminous in recent years, that no attempt has been made to make even an approximately complete list of references. The titles given below have been selected for the use of students who are interested in the history of the subject, and for this reason they have been arranged chronologically.
The titles for the later years refer more to the practical developments of the subject than to laboratory methods and descriptions of organisms.
Other references relating to particular classes of organisms are given at the end of the various chapters in Part II.
REFERENCES
Hassall, a. H. 1850. A Microscopic Examination of the Water Supplied to
the Inhabitants of London and the Suburban Districts. I^ndon. HoRSFORD, E. N., and Jackson, Chas. T. 1854. Report on the Disagreeable
Tastes and Odors in the Cochituate Water Supply. Ann. Rept. Coch. Water
Bd., 1854. Bell, James. 187 i. Microsi^opical Examination of Water for Domestic Use.
Mo. Micro. Jour., V, 163. London. Farlow, W. G. 1876. Reports on Peculiar Condition of the Water Supplied
to the City of Boston. Report of the Cochituate Water Board, 1876. Farlow, W. G. 1877. Reports on Matters connected with the Boston Water
Supply. Bulletin of Busscy Inst., Jan., 1877. HntT, L. 1879. Ueber den Principien und die Methodc der Mikroskopischen
Untersuchung des Wassers. Zeitschrift fiir Biologie. Farlow, W. G. 1880. On Some Impurities of Drinking Water Caused by
Vegetable Growths. Supplement to ist Ann. Rept. Mass. St. Bd. of Health.
Boston, 1880.
393
394 THE MICROSOOPT OF DBINKINO WATER
Fteley, a. 1880. Algc in a Water Supply. Settlement to ist Ann. RepC of Mass. St. Bd. of Health, Lunacy, and Charity.
NiCBOLS, Wm. Riplcy. 1880. On the Temperature of Fresh Water Lakes and Ponds. Proc. Bost. Soc Nat. Hist., XXI. (Contains a bibliognphy of the subject to date.J
Remsen, IiA. 1881. On the Impurity of the Water Supply. (Odor caused by Spongilla.) Boston.
Hyatf, J. D. 1882. Sporadic Growth of Certain Diatoms and the Relation thereof to Impurities in the Water Supply of Cities. Proc Am. Soc Micros- copy, 197-199, J*82.
Farlow, W. G. 1883. Relations of Certain Forms of Algc to Disagreeable Tastes and Odors. Science, II, 333.
MacDonald, J. D. 1883. A Guide to the Microscopical Examination of Drink- ing Water. 2d edition. London: J. ft \. Churchill.
Potts, E. 1884. Fresh- water Sponges as Improbable Causes of the Pollution of River Water. Proc. Ac. Nat. Sc., Phila., 1884, 30.
Smith, Hamilton. 1884. Temperature of Lakes. Trans. Am. Soc. Civ. £ng., March, 1884.
SoRBY, H. C. 1884. Microscopical Examination of Water for Organic Impuri- ties. Jour. Roy. Micro. Sci., Series 2, IV, 1884.
SoRBY, H. C. 1884. Report of Microscopical Investigation of Sewage in Thames Water Supply. Report of Royal Commission on Metropolitan Sewage Discharge, II.
Taylor, J. E. 18S4. The Aquarium: Its Inhabitants, Structure, and Manage- ment. London: W. II. Allen & Co.,
Raftkk, George W. 18H6. On the Use of the Microscope in Determining the Sanitary Value of Potable Water, ynth Special Reference to the Study of the Biology of the Water of Hemlock Lake. Proc. Micro. Sect. Rochester Acad, of Sciences, 1886.
IIenskn, V. 1887. Uet>cr die Restimmung des Planktons oder des im Meere, treibcndcn Materials an Pflanzcn und Thieren. V. Bericht d. Kommis- sion zur wiss. Untcrsuchung d. deutschen Meere zu Kiel, XII-XIV, 1-107.
Hitchcock, R. 18S7. The Biological Examination of Water. Am. Mo. Micr. Jour., VIII, 9.
Nichols, Wm. Ripley. 1883. Water Supply Considered Mainly from a Chem- ical and Sanitary Standpoint. New York: John Wiley & Sons, 1883.
Rafter, (J. W. 1888. On the Micro-Organisms in Hemlock Water. Rochester.
Raftkr, Gkorge W. 1888. The Microscopical Examination of Potable Water. No. 103 in Van Nostrand Science Series.
Raftkr, (i. W. 1888. Some of the Minute Animals which Assist the Self-Puri- fication of Running Streams. Discussion of a paper by Chas. G. Carrier on the Self- Purification of Flowing Water and the Influence of Polluted Water in the Causation of Disease. Trans. A. S. C. E., XXIV, Feb., 1891.
SEixiWicK, William T. 1888. Biological Examination of Water, Technology Quarterly, II, 67, 1888.
Conn, H. W. Report on Uroglena in Middletown, Conn., in 24th Ann.. Rept. of Middletown Water Commissioners for year ending Dec.- 31, 1889. Also paiKT by Prof. Williston.
SCIENTIFIC UTERATURK 395
Sbdgwick, William T. 1889. Recent Progress in Biological Water Analsrsis.
Jour. N. E. W. W. Assoc., IV, Sept., 1889. Rafter, G. W. 1889. On the Fresh-water Algae and their Relation to the Purity
of Public Water Supplies, with discussion. Trans. Am. Soc. of Civil Eng.,
Dec., 1889. Rafter, G. W., Mallory, M. L., and Lane, J. Edw. 1889. Volvox globator
as the cause of the fishy taste and odor of the Hemlock Lake Water in 1888.
Ann. Rept. of Ex. Bd. of Rochescer, N. Y., for 2 years ending April i, 1889. Forbes, F. F. 1890. A Study of Algae Growths in Reservoirs and Ponds.
Journal of the N. E. Water Works Assoc., IV, June, 1890. Reprinted in
Fire and Water, July 19, 1890. Mass. State Board of Health. 1890. Annual Reports.
The annual reports since 1890 contain reports upon the examination of water- supplies and experiments on the filtration of sewage and water, besides the following papers:
1890. Suggestion as to the Selection of Sources of Water Supply. By F. P. Steams.
1891. On the Amoimt of Dissolved Oxygen contained in Waters of Ponds and Reservoirs at Different Depths. T. M. Drown.
1891. The Efifect of Aeration of Natural Waters. T. M. Drown.
1892. On the Amount of Dissolved Oxygen iii the Water of Ponds and Reser- voirs at DifiFerent Depths in Winter, under the Ice. T. M. Drown.
1893. On the Amount and Character of Organic Matter in Soils, and its Bearing on the Storage of Water in Reservoirs. T. M. Drown.
1901. A Study of odors observed in the Drinking Waters of Massachusetts.
Gary N. Calkins. 1901. Seasonal Distribution of Microscopic Organisms in Surface Waters.
Gary N. Calkins. 1901. Elxperimental Filtration of the Water Supply of Springfield, at Ludlow.
Parker, G. H. 1890. Report on the Organisms, excepting the Bacteria, found in the Waters of the State, June, 1887 — ^July, 1889. Mass. State Board of Health. Special Rept. on Examination of Water Supplies. Boston.
Rafter, George W. 1890. The Biological Examination of Potable Water. Proc. Rochester Acad. Sciences, I, 33-44, 1890. Rochester.
Stearns, Frederick P. 1890. Temperature of Water. Special Report of Mass. St. Bd. of Health on Examination of Water Supplies, 1890, 659.
Calkins, Gary N. 1891. The Microscopal Examination of Water. 23d An. Rep. Mass. St. Bd. of Health.
Connecticut State Board of Health Reports for 1891 et scq.y contain results of monthly analyses of the water-supplies of the State.
Forbes, F. F. 1891. The Relative Taste and Odor Imparted to Water by some Algae and Infusoria. Jour, of the N. E. Water Works Assoc., VI, June, 1891.
Le Conte, L. J. 1 89 1. Some Facts and Conclusions bearing upon the Rela- tions Existing between Vegetable and Animal Growths and Offensive Tastes and Odors in Certain Water Supplies. Proc. Am. Water Works Assoc.
Boston Water Works. Annual Reports. 1892 e/ seq. Each report contains a simimary of the work of the biological laboratory, with tables of tempera- ture, color, micro-organisms, rainfall, etc.
396 THE MICROSCOPY OF DRINKINa WATER
i8g2. Temperature Curxes for Lake Cochituate. Reference to the Standard Unit. Odor caused by Synura.
1893. Reference to Standard Unit. Note on the cobr of the water. Description oi Synura and its effect on the water. Description of new colorimeter. An investigation of the cause of the color of natural water.
1894. An account of stagnation phenomena in Lake Cochituate. Note on the seasonal distribution of the Diatomacee and Infusoria. A key to the Infusoria foimd in the Boston water-supply. The bleaching effect of sunlight on the coloring matter of water.
1895. The effect of light on the growth of diatoms.
FoREL, Dr. F. a. 1892, 1895, 1904. Le Leman, Monographie Limnolog^ue.
3 vols. Lausanne, F. Rouge. (Perhaps the most comprehensive book on
the general subject of limnology. Although not recent it will always remain
of great historical value.) Rafter, G. W. 1892. Some of the Circumstances affecting the Quality of a
Water Supply. Proc. Am. Water Works Assoc., 12th Ann. Meeting, 1892. Garrett, J. H. 1893. The Spontaneous Pollution of Reservoirs. (Odor pro- duced by Chara.) Lancet, Jan. 7, 1893. Peck, James L 1893. On the Food of the Menhaden. Bull. U. S. Fish Com.,
XIIL Rafter, George W. 1893. On Some Recent Advances in Water Analysb and
the Use of the Microscope for the Detection of Sewage Contamination. Am.
Month. Micro. Jour., May, 1893. Whipple, Geo. C. 1894. A Standard Unit of Size for Micro-Organisms. Am.
Monthly Micro. Jour., XV, Dec, 1894. Whipple, Geo. C. 1894. Some Observations on the Temperature of Surface
Waters, and the Effect of Temperature on the Growth of Micro-organisms.
Jour, N. E. W, W. Assoc. IX. Birge, E. a. 1895. Plankton Studies on Lake Mendota. I. The vertical
distribution of the pelagic crustacca. Trans. Wisconsin Acad, of Sci., Arts,
and Letters, X, June, 1895. FitzGerald, Desmond. 1895. The Temperature of Lakes. Trans. Am. Soc.
Civ. Eng., XXXIV, Aug., 1895. Peck, James I. 1895. The Sources of Marine Food. Bull. U. S. Fish Com., XV. RussKLL, Israel C. 1895. Lakes of North .\mcrica. Boston: Ginn & Co. Warren, H. E., and Whipple, G. C. 1895. The Thermophone, a new instru-
Tiicnt for obtaining the temperature of a distant or inaccessible place; and
Some Observations on the Temperature of Surface Waters. Am. Meteor.
Jour., XII, June, 1895. Warren, II. E., and Whipple, G. C. 1895. The Thermophone, a new instru- ment for determining temperatures. Tech. Quart., VIII, July, 1895. DoLLEY, C. S. 1896. The Planktonokrit, a Centrifugal Apparatus for the
Volumetric Estimation of the Food Supply of Oysters and other Aquatic
Animals. Proc. Acad. Nat. Sci., Philadelphia, 276-80. Jackson, I). D. 1896. On an Improvement in the Sedgwick-Rafter Method for
the Microscopical Examination of Drinking Water. Tech. Quarterly, DC,
Dec, 1896.
SCIENTIFIC LITERATURE 397
Kemna, Ad. 1896. La Couleur des Eaux. Bull. d. 1. Soci6t£ Bdge de G6ologiey
de Paltontologie et d'Hydrologie (Bruzelles), X, 324-279, 1896. Whipple, Geo. C. 1896. Experience with the Sedc^ck-Rafter Method. Tedi-
nology Quarterly, IX, Dec., 1896. Davenpokt, Chas. B. 1897. Experimental Morphology. Part I, Effect of
Chemical and Physical Agents upon Protoplasm. Part 11. Effect of Chem- ical and Physical Agents upon Growth. New York: Macmillan Co. Field, Geo. W. 1897. Methods in Planktology. loth An. Rept. Rhode Island
Agricultural Experiment Station, 1897. Jackson, D. D., and Ellms, J. W. 1897. On Odors and Tastes of Surface
Waters, with special reference to Anabaena. Technology Quarterly, X, Dec.,
1897. RoFOiD, Chas A. 1897. On Some Important Sources of Error in the Plankton
Method. Science, N. S., VI, Dec. 3, 1897. Strohmeyer, O. 1897. Die Algenflora d. Hamburger Wasserwerkes. Leipzig,
Bot. Centralb. 1898, 406. FoRDYCE, Chas. 1898. A New Plankton Piunp. Proc. Nebraska Hist. Soc.,
2d Series, U. HoLLis, F. S. 1898. Methods for the Determination of Color of Water and
the Relation of Color to the Character of Water. Jour. N. E. W. W.
Assoc., 1898. Jackson, D. D. 1898. An Improved Filter for Microscopical Water Analysis
Tech. Quarterly, XI, Dec., 1898. Reighard, Jacob. 1899. A Plan for the Investigation of the Biology of the
Great Lakes. Transactions of the American Fisheries Society, 28th Annual
Meeting, pp. 65-71. American Pubuc Health Association. 1900. First Report of Progress of
Committee on Standard Methods of Water Analysis. Reprint from Science,
N. S. Vol. Xn, No. 311, pp. 906-915. December 14, 1900.
1901. Second Report of Progress of Committee on Standard Methods of Water Analysis. Vol. XXVH Amer. Public Health Assn., p. 377.
1902. Third Report of Progress of Committee on Standard Methods of Water Analysis. Vol. XXVIH, p. 388.
1905. Final Report, Journal of Infectious Diseases, Supplement, No. x, X905. 191 2. Second Edition of the Report of the Committee, Published by the Association, 289 4th Ave., New York.
HoLLis, Frederick S. 1900. On the Distribution of Growths in Surface Water Si^plies. Trans. Amer. Microscopical Soc., 23d Annual Meeting, June, 1900. Vol. XXH.
Parker, Horatio N. 1900. Some Advantages of Field Work on Surface- water Supplies. Transactions of the Amer. Microscopical Soc., June, 1900.
Whipple, G. C. 1900. Discussion of Filtration. Trans. Am. Soc. C. £., XLIII, p. 318.
FoREL, Dr. F. a. 1901. "Handbuch dcr Scenkunde." Stuttgart. J. Engel- hom. (An excellent short treatise on general limnology.)
Hyams, Isabel F., and Richards, Ellen H. 1901. Notes on Oscillaria Pronnca. aV) Life History. Tech. Quart., Vol. XIV, No. 4, Dec. (V) Chemical Composition. Tech. Quart., Vol. XIV, No. 4, Dec., 1901.
398 THE MICROSCOPT OF DRINEINa WATER
KzMNAy Ad. 1901. Articles Bibliographiques sur Its eauz. Bulletin de k
Sod6t6 Edge de Pa]i6oiitologie et d'Hydiologie. November^ 1901. Whzpfle, G. C. 1901. DiscusaioD of FatratioQ. Thus. Am. Soc C E^ XLVI,
p. 343.
Whipple, Geo. C, and Paiker, Hokatio N. xgox. The Amoant of (hygm and Carbonic Add Dissolved in Natural Waters and the Effect of these Gases upon the Ckxurrence of Microscopic Organisms. Tnus. Amer. Micro- scopical Soc. August, X901, Vol. XXIll.
HoLUS, Fredesick S. 1902. Two Growths of CUamydomooas In Connectinrt. Trans. Amer. Microscopical Soc., June, 1902.
BntGE, E. A. 1903. The Thermodine and its Biological Significance. Trans- actions of the Amer. Microscopical Soc., 26th Annual Meeting, July 29, 1903.
Field, George W. 1903. Certain Biological Problems Connected with the proposed Charles River Dam. Appendix No. 6. Report of the Committee, Charles River Dam.
Hazen, Allen. 1903. The Physical Properties of Water. Journal of the New England Water Works Assn., Vol. XVII, 1903.
Hazen, Allen, and Whipple, Geo. C. 1903. Measurement of Turbidity and Color. Circular No. 8, Division of Hydrography, Dept. of Interior, U. S. Geological Survey.
Moore, Geo. T. 1903. Methods for Growing Pure Cultures in Alge. Journal of Applied Microscopy and Laboratory Methods. Vol. VI, No. 5, 1903.
Imbeaux, Dr. Ed. 1904. Odeur, Couleur et Limpidite de Teau. Bulletin des seances de la Soci6t6 des Sciences de Nancy, 1904.
Moore, Geo. T., and Kellerman, Karl F. 1904. A method of destroying or preventing the growth of aigs and certain pathogenic bacteria in water supplies. Bulletin 64, Bureau of Plant Industry, U. S. Department of Agri- culture.
Richards, Ellen H., and Woodman, Alpheus G. 1904. Air, Water and Food. 2d edition. John Wiley & Sons, New York, 1904.
Springfield, Mass. Reports of Special Conmiission on Water Supply. Mardi 28, June 6, Oct. 31, 1904.
1900. Report of the Chemist of the Mass. State Board of Health upon the Exp>crimcntal Filtration of the Water Supply of Springfidd, at Ludlow, Mass. From Dec. 21, 1900, to Jan. 31, 1902. 1902. Special Reix)rt on Improvement of Present Water Supply. April
14, 1902. Bard of Water Commissioners. 1905. Report of State Board of Health, to Board of Water Coounissioners, Feb. 2, 1905.
WiNSLOW, C.-E. A., and Underwood, Wm. Lyman. 1904. Report on the Sanitary Problems relating to the Fresh Marshes and Alewife Book. In Special Report on Improvement of the Upper Mystic Valley. Metropolitan Park Commission, Boston.
Caird, J as. M. 1905. The Copper Sulphate Treatment for Algae at Middle- town, N. Y. Eng. News, Jan. 12, 1905, p. 33.
Clark, H. W. 1905. Investigations in Regard to the Use of Copper and Coppa Sulphate. Annual Report of the Mass St. Bd. of Health, 1905, p. 292.
SCIENTIFIC LITERATURE 399
GooDNOUGH, X. H. 1905. Experiments upon the Removal of Organisms from the water of Ponds and Reservoirs by the Use of Copper Sulphate. Annual Report, Mass. St. Bd. of Health, 1905, p. 209.
Moore, Geo. T., and Rellerman, Karl F. 1905. Copper as an algidde and disinfectant in water-supplies. Biilletin 76, Bureau of Plant Industry, U. S. Department of Agriculture.
Moore, Geo. T., Jackson, D. D., Goodnough, X. H., and others. 1905. A Symposium on the Use of Copper Sulphate and Metallic Copper for the Removal of Organisms and Bacteria from Dinking Water. Jour* New England Water Works Association, XIX, No. 4, p. 474.
Baldwin, H. B., and Whiffle, G. C. 1906. Observed Relations between Carbonic Add and Algs Growths in Weequahic Lake, N. J. Rept. Am. Pub. Health, 32: 167-182.
Caird, Jas. M. 1906. Copper Sulphate Results. Proc. Am. W. W. Asso., 1906, p. 249.
Kellerman, Karl F., and Beckwith, T. D. 1906. The Effect of Copper upon Water Bacteria. Bulletin 100, Part VII, Bureau of Plant Industry, U. S. Dept. of Agriculture.
Kellerican, Karl F., Pratt, R. Winthrop, and Kimberley, A. Elliott. 1907. The disinfection of sewage effluents for the protection of public water-supplies. Bulletin 115, Bureau of Plant Industry, U. S. Department of Agriculture.
LocHRiDGE, £. £. 1907. The Springfield Water Works. (Containing a de- scription of the Ludlow Filter.) Jour. N. E. W. W. Asso., XXI, p. 279.
Story, Carroll F. 1909. The Ludlow Filters. Jour. N. E. W. W. Asso. Vol. XXin, p. 229.
TiGHE, James L. 1909. Odors and Tastes ^i the Water Supply of Holyoke. Jour. N. E. W. W. Asssc. XXIII, p. 324.
LovEjoY, W. N. 1910. Filter Troubles caused by Micro-organisms at Louis- ville. Eng. Rec., Vol. 62, p. 664.
MxTRRAY, Sir John, and Pullar, Laurence. 1910. Bathymetrical Survey of the Scottish Fresh Water Lochs. Edinburgh. Challenger Office. (This is a set of six magnificent volumes containing the reports of scientific researches made by the authors and their associates during the years 1897 to 1909. Vol. I contains the principal general articles. The last five contain chiefly maps. The subject of seiches is particularly well treated. Associated with Sir John Murray, were such men as Prof. George Chrystal, E. M. Wedderbum, George West, and Dr. C. Wesenberg-Lund.
Steuer, Dr. Adolf. 1910. Planktonkunde. Leipzig. B. G. Teubner. (Con- siders the fresh water plankton, but is devoted chiefly to marine plankton.)
Wilcox, Wm. F. 1910. Creosote Treatment for Algae Growth. Proc. Am. W. W. Asso., 1910, p. 166.
BiRGE, E. A., and Juday, C. 1911. The Inland Lakes of Wisconsin; Dissolved Gases and their Biological Significance. Wisconsin Survey. Bull. 22. (Sci. Series 7.)
DoWNES, John R. 1911. A Study 9f the Water Supplies of the Isthmus of Panama. Proc. Med. Asso. of Isthmus of Panama, Sept., 191 1.
Ellms, Jos. W. 191 i. H3rpochlorite for Destro)dng Growths of Algae and Diatoms at Cincinnati. Eng. Record, Vol. 63, p. 388.
400 THE MICROSCOPY OF DRINKING WATER
Marsson, Dr. Maximiuan. 191 i. The Significance of Flora and Fauna in
Maintaining the Purity of Natural Waters. Translated by Emil Kuichling,
Eng. News, Aug. 31, 191 1, Vol. I^VI, p. 246. Mast, S. O. 191 i. Light and the Bchavoir of Organisms. New York.
John Wiley ft Sons. Steuer, Dr. Adolf. 191 i. Ldtfaden der Planktonkunde Leipsig. G. B.
Teubner. (A shorter treatise than the preceding and on the whole better
adapted to those interested in fresh water.) Kellerman, Karl F. 191 2. The Rational Use of Disinfectants and Algicides
in Municipal Water Supplies. Eighth International Congress of AppUed
Chemistry. Vol. 26, p. 241. Abstract in Wasser und Abwasser, Vol. VI,
Murray, Sir John. 191 2. The Depths of the Ocean. London: Macmillan
Co. (While devoted to marine studies this is one of the most inspiring books
for any one who is interested in limnology.) BiRGE, E. A. 1913. Absorption of Light by Water. Science, Nov. 14, p.
702. Forbes, Stephen A., and Richardson, R. E. 1913. Studies on the^Biology
of the Upper Illinois River. Bulletin of the Illinois State Laboratory of
Natural History, Vol. IX, Article X. Gelston, W. R. 191 3. Algx in the Water- works Reservoir at Quincy, 111.
Eng. News, Vol. 69. p. 835. Thresh, Dr. John C. 1913. The Examination of Waters and Water Supplies.
2d Kdilion, Philadelphia, P. Blakiston's Son & Co. (A general treatise on
water analysis, with a chapter on microscopical examination, with numerous
plates. A fair representation .of present English practice.) Whipple, G. C. 1913. Decarbonation as a Means of Removing the Corrosive
ProfKirties of Public Water Supplies. Journal N. E. W. W. Asso. Vol.
XXVII, No. 2, p. 193.
GENERAL INDEX
Absorption of light by water, ii6 Aerating fountains, 263 Aeration, 236, 261
by percolation, 269 Aeration experiments, 262 Aeratory nozzles, 265 Albany, N. Y., filters, 265 Algae as local nuisances, 205
hygienic cfifect of, 215
injurious character, 200
relation to gases, 128
use of term, 287 American Public Health Association, 8 Anabcna, occurrence of, 154 Antwerp studies on filtration, 270 Area of hikes, 151 Aromatic odors, 196 Asellus aquaticus, 281 Ashokan reservoir, treatment of, 233,
Asterionella in Ridgewood reservoir,
247 Attractiveness of water, 201
B
Bacillarieae, 288
Bacteria, effect of copp)er sulphate on,
257. 258 Bacteriological examination of water, 8 Barnes' electrical thermometer, 87 Beriin water supply, 250 Biological balance of streams, 82 Birge, Dr. A. E., 6, 7, 126 Birge's phinktonnet, 22 Bleaching of walcr during storage, 109 Boston, organisms in pipes, 282 Boston Water Works Laboratory, 2 Bottoms of reservoirs, 214
Brisbane, Australia, filters at, 237 Brooklyn, pipe moss in, 285 Bryozoa, 378
in pipes 283 Bunker, John W. M., 49, 158 Bunker's stand for Sedgwick-Rafter
method, 31 By-pa§ses, 260
Camera lucida, 65
Canal waters, 79
Carbonic acid, determination of, 122
dififusion of, 125
removal from water by algx, 216
seasonal changes, 1 28
solubility of, 124
sources of, 125 Care of the microscope, 59, 60, 61, 62 Cedar Swamp, 207 Celiata, 357 Cell, Bunker's, 35
Sedgwick-Rafter, 34 Chambers, Dr. Charles O., 128 Charleston, S. C, water supply of, 239 Chemical analysis of water, 8,12
relation to microscopic organisms, 142 Chestnut Hill Reservoir, 166 Chicago Drainage Canal, 161 Chlamydothrix, 249 Chlorine, excess of, 143 Chlorophyceai, 288
seasonal distribution, 1 70 Circulation p>eriods in lakes-, 102 Cladocera, 375 Classification of lakes, 99
of organisms, 286 Clonothrix, 249
401
402
GENERAL INDEX
Closed community, 126 Cochituate, Lake, 91, 95 seasonal distribution of organisms,
173 carbonic acid in, 213
dissolved oxygen in, 313 Cochituate, stagnation of, 211 Color of water, 107
photography, 70
relation to organisms, 153 Compressibility of water, 83 Concentration of sample, 32 Connecticut, algx in, 158 Copepoda, 374 Copper sulphate, efifect on fish, 256
method of using, 252
nature of reaction, 252
quantity required, 253, 254
treatment for algae, 251
used before filtration, 259 Cordylophora, 281 Cotton filter, 47 Crenothrix, 75, 249
in sand filters, 273 Creosote treatment for algae, 259 Croton water supply, algse in, 154 Crustacea, 373
seasonal distribution of, 173 Cucumber taste, igi Currents in lakes, 103 Cyanophyceac, 316
seasonal distribution of, 170
D
Decomposition, 118
Demonstration eye-piece, 68, 71
Density of water, 83
Depth, efifect of, on organisms, 141, 152
relation to organisms, 184 Dcsmidies, 332 Diathermancy of water, 85 Diatomacca;, 291
seasonal distribution, 165 Diatom cells, 291
cell contents 295,
classification, 303
external secretions, 296
markings 294
movement, 296
multiplication, 301
reproduction, 303 Disk for measuring transparency, 115
Dissolved oxygen, coUectioii of samples for, 26
determination of, 119
dififusion of, 125
seasonal changes, 126
solubility of, 121
sources of, 1 25 Dodge, Prof. Chas. Wright, 159 Double filtration, 274 Downes, John R., 2x4 Dreyssena, 281 Drown, Dr. T. M., 146, 223
Ecology, 13 Edinger camera, 67 Entomostraca, 373 Enumeration of organisms, 37 Errors in Sedgwick-Rafter method, 38 Eurich's collecting apparatus, 17 European plankton studies, 5 Eye-piece of microscope, 52
Farm Pond, 191
Field work, 71
Filter scums, 272
Filtered water, organisms in, 81
storage of, 248 Filtration, 236
of algae laden water, 269, 273
of samples, 28 Find objects under microscope, 52 Fish, death of, 132
killed by copper sulphate, 256
life, food supply of, 13 Fishy odors, 197 FitzGerald, Desmond, 224 Floating roofs, 250 Flotation of plankton, 176 Focusing, 55 Forbes, 161
Forel, F. A., limnological studies, 5 Fowler, Prof. W. G., 220 Frequency, index of, 149 Fresii Pond, 127 Fteley, Alphonse, 220 Fuller, Geo. W., 218 Fungi, 171, 341 Funnel for Sedgwick-Rafter method, 29
GENERAL INDEX
403
GaUkmella, 249 Gammanis pulez, 281 Gases dissolved in water, X17 Genessee River, 159 Goodnough, X. H., 224 Grassy odors, 197 Ground water, 74
mixed with surface water, 247
storage of, 246 Growths, irregularity of, 227
temporary, 229
H
Hardness of water, 143
Hassell's method of microscopical exam- ination, I
Hazen, Allen, 218, 265
Hensen, Victor, plankton studies, 5
Heterokontae, 288
Hoover, C. P., 216
Horizontal currents, 103, 104
Horizontal distribution of organisms, 175
House filters, 275
Human system, effect of copper sul- phate on, 251
Hypochlorite treatment for algae, 260
Ice, algae in, 163 Illinois River, 161
aeration in, 263 lUumination of microscopes, 53, 59 Index of frequency, 149 Infiltration galleries, 75 Internationale Revue der Gesammten
Hydrobiologie, 6 Iron bacteria, 313
Kensico aeraters, 265 Kensico reservoir, treatment of, 235, 240, 243, 245
Jackson's theory of diatom movement,
297 Juday, Dr. Chauncey, 128
Kean, A. L., method of water examina- tion, 3 Kellerman, Karl F., 251 Xemna, Ad., 270
Lake Winnepesaukee, 93
Lakes, organisms in. 81
Leitz' demonstration eye-piece, 68
step micrometer, 64 Light, effect on diatom growth, 167 Limnetec organisms, 175 Limonological Commission, 6 Limnology, 83 Littoral organisms, 175 Lochridge, £. £., 239, 265 * Lynn, water supply of, 79 Ludlow filter, 273 Ludlow reservoir, filter experiments, 238
M
Macdonald, J. D., method of micro- scopical examination, 2 Magnification, 64 Malacostraca, 373 Marsson's investigations, 81 Massachusetts, algae in, 155
microscopic organisms of, 137
soil stripping in, 225
State Board of Health, 7 McGregor Lake, 183 Measurement of objects, 62 Mendota, Lake, 116
dissolved oxygen, 130 Metropolitan water supply, algae in, 155
Water Works laboratory, 2 Micrometer, 64
Sedgwick-Rafter method, 36 Microscope, construction of, 49
for Sedgwick-Rafter method, 35
use of, 49, 51 Microscopic organisms, occurrence of,
133 Microscopical examination of water,
various aspects, 10 Molisch, Dr. Hans, 250, 314 Moore, Dr. Ceo. T., 251 Mt. Prospect Laboratory, 2 Murray, Sir John, studies in the
Scottish lakes, 6 Myxophyceae, 288
404
GENERAL INDEX
N
Newcomb filter, 275 New England data regarding organ- isms, 148 New York Water Works Laboratory, 3 Nichols, Wm. Ripley, 219, 220 Nitrates, 146 Nitrogenous food of organisms, 230
Objective, method of using, 52 Odor, relation to organisms, 151 Odors, cause of, 1 2
caused by decomposition, 188, 198
caused by littoral plants, 191
caused by organic matter, 187
caused by organisms, 189
caused by plankton, 194
classification of, 187
in Massachusetts water supply, 199
in water supplies, 186
of decomposition, 258 Oils, odors caused by, 195 Ontario, Lake, algae in, 158 Optics of the microscope, 57 Organisms as sources of food, 230 Origin of waters, 12 Owasco Lake, 103 Oysters, food of, 13
Panama, water supplies, 214
Parker, G. H., method of water
examination, 3 Peck, James L, 7 Phax)phyceaj, 288 Photosynthesis, 117 Photomicrographic camera, 66 Physical examination of water, 8
pro[)erties of water, 83 Pipe moss, 281, 283, 284 Pil)es, organisms in, 277, 278, 279 Plankton, distribution of, 136
estimation of, 22
flotation of, 176
net, 17
odors of, 193
pump, 24
studies in KurofHi, 5
studies in United States, 6
Phinktonokrit, 45
Pockets, efifect of, 308
Population, relation to organisms, 153
Portable microscope, 70
Polyzoa, 378
Potomology, 82
Practice exercises with the microscope,
56 Precision of Sedgwick-Raf ter method, 41
Preservation of specimens, 25 Projection of photomicrographs, 69 Protozoa, 288, 344
seasonal distribution of, 171 Protozoan cell, 345 Pure water, value of, 200
Rafter, George W., 220
method of microscopical examina- tion, 4 Rain water, 73 Raphidomonas, 79 Reading, Pa., filters at, 237 Records of examination, 45 References, microscope, 72 Reighard's net, 21 Reservoir stripping, 218 Reservoirs, organisms in, 81 Respiration, 117
Results of microscopical examination, 42 Rhodophyceae, 288 Ridge wood reservoir, 247 River waters, 77 Rotifera, 365
seasonal distribution of, 172 Rotterdam water calamity, 281
Schizomycetcs, 171, 312
Samples, collection of, 14
Sanitary examination of water, 9
Seasonal distribution of algae, 164
Secondary growths of organisms after copper treatment, 257
Sedgwick-Rafter method. 28
Sedgwick, Wm. T., method of micro- scopical examination, 4
Seeding reservoirs with organisms, 228
Seiches, 106
Self-purification in Genessee River, 159 of streams, 1 1
GENERAL INDEX
405
Sewage pollution, lo
as source of food, 231 Shearing plane, 104 Sling filter, 32 Smith, J. Waldo, 218 Soil stripping, 2i3, 224
advantages of, 232
comparative cost, 233
effect on cost of filtration, 240 Sorby, H. C, method of microscopical
examination, 2 Sponge, fresh water, 192 Spongilla, 281 Spongids, 381 Springfield filter, 265 Sprttngschicht, 96 Squam Lake, 95 Stagnation, effect on quality of water,
226 in reservoirs, 209 of water, 92 SUndard Methods of Water Analysis, 8
Sundard unit, 42 Steams, Frederick P., 146, 223 Steuer*s collecting apparatus, 1 5 Strainer jars, 17 St. Thomas, Ont., 259 Storage period, 153 of filtered water, 248
ground-water, 246
surface-water, 206 Stripping reservoir sites, 218 Strohmeyer's experiments, 217 . Sub-stage diaphragm, 56 Summer temperature conditions, 94. Surface waters, 77 Swamp land, effect of, 206
Temperature changes in pipes, 277
of lakes, 89
of surface water, 231 Thermal conductivity of water, 84
Thermocline, 96 Thermometry, 85 Thcrmophone, 87 Transition zone, 95
organisms at, 179 Transmission of light by water, 107 Transparency of water, 113 Turbidity of water, ixi
Undertow currents, 103 U. S. Geological Survey, apparatus, 180 turbidity rod, 1x2
Value of pure water, 200
Vertical distribution of organisms, 177
Vistos<.ily oL water, 84
effect on organisms, 181 Volume of water in reservoirs, 256
W
Ward, Henry B., 6, 7 Weeds as source food, 230 Wecquahic Lake, 132 Wcsenberg-Lund, 182 West, Prof. G. S., 287 WTiipplc, Melville C, 158, 262 W- hippie's collecting apparatus, 15 W^ilcox, Wm. F., 259 Wilhelmis plankton pump, 25 Wind and agitation, 231 Winter temperature conditions, 93 Wizard sediment tester, 47
Zacharias, Otto, plankton studies, s Zodglcca, 42
INDEX TO PLATES
DESCRIPTIONS OF ORGANISMS
PLATB PAGB
Achlya XI 343
Adneta XV 346, 363
Actinophrys XI 350
AmoelMi XI 348
Amphora I 305
Anabaena IV 317, 321
Aoacharis XIX 384
Anguillula XIX 384
Anthophysa XII 352
Anunea XVII 371
Arcella XI 349
Arthrodesmus. VIII 334
Aphanizomenon V 317, 322
Aphanocapsa IV 319
Aphanothece 320
Asellus aquaticus 373
Aspergillus X 342
Asplanchna XV 369
Asterionella II 308
B
Batrachospermum . . . XIX 326, 384
Beggiatoa IV 313
Bosmina XVII 376
Botryococois VI 328
Brachionus XVII 371
Branchipus XVIII 376
Bursaria XIV 361
Canthocamptus XVII 375
Carterius 3^^
Ceratium Xm 357
Ceratophyllum XIX 384
CercoxDODas ^ XII 351 I
Chtetonotus
Chxtophora
Chara
Chlamydomonas
Chlamydothrix
ChroOcoccus
Chydorus
Cladophora
Cladothrix IV
Clathrocystis
Clonothrix
Closterium
Cocconeis
Cocconema
Codonella
Coelastrum
Coelomonas
C(£lospha:rium IV,
Coleps
Colpidium
Colurus
Conferva
Conochilus
Corethra
Cosmarium
Crenothrix
Cristatella
Cylindrospermum
Cyclops
Cydotella
Cymbella
Cypris
Cryptomonas
PLATE PAGl
XIX 384
X 339
XIX 339
xm 355
314
IV 318
xvni 376 IX 338
298, 3", 314 IV 319
314 vn 333
I 307 I 305
XIV 361 VI 330
xn 352
298, 3i7i 319 XIV 362
XV 363
371
IX 338
XV 368
384
VII 333. 335
IV 313
380
V 322, 346
XVII 374
HI 310
I 305. 335
XVII 375
XII 355
Daphina XVII 376
Desmidium IX 335
407
INDEX TO PLATES
Ditptomut XVII 37S
DUtomk in 309
IXctyofplueTiutn VI 318
DifflugU XI 349
Diglena XVI 370
Dimorphococnu VI 338
Dinobryon XII 335
Doddiutn VII 333
Dnpuuldia X 3*6, 339
E
Enchely* XIV 363
Encyonema I 3*S
Epistylis XIII 359
EpithemiB I 307
Euaslrum VIII 334
Eudorina VII 331
Euglena XII 3S3
EuglyphA XI 349
Eunotia I 3^7
Euplotes XIII 358
F
floscularia XV
Fra(;iUria II
Fredcricelltt XVIIl
Gallionella
Gammarus pulcx
Glenodinium XUI
Glcccapsa IV
Gleeocystis V
(ilccothece
Gomphonema I
Gonium VII
Gordius. 384
Gymnodinium
H
Halteria XIH 359
Heleromcycnia 381
Ilcterophrys '5°
H ima n till i urn 11 308
Hippuris
Hyalolhcca IX 3,14
Hydalina
Hydra XIX 384
Hydrodidyon VI 3^9
L
I^mna XIX 384
Lcplomilus XI m
LtptoOui* IV 31]
Lyv^by*. V 3"
U
MMnUotus XDC 384
MalloDUMMS XII 346, 3$s
Mutigoccrca XVI 371
MdicefU XV 368
Mdodra in 310, 346
MeridioQ Ill 309
MetumopedU IV 319
MeycDU 38J
Mknstereaa VIII 334
MicTDCodon XV 369
Midocoleus V 3*3
MicrocyitiB IV 19S, 319
MoDU XII 3SJ
MucoT X 343
Uyriophyllum 384
N
Nah XDC 384
Naasula XIV 36a
NavicuU I 306
Ncphrocyiium VI 318
NilelU XIX 339
Nitischia Ill 309
Nostoc IV 321
Noiholca XVII 371
Noteus 371
0
Ophlocytium VI 329
Oscillaiia V 313
P
Palmdia V 327
PaludiccUa XVIII 379
J'andorina VII 298, 331
Paramaciium XIV 361
Pctlinalclla XVIII 379
Pediastrum VI 329, 335
I'cnicillium X 341
I'CTto" VII jjj
I'cridinium XIII 356
Pha<L.s XII 355
rieurorcma XIV 362
Pluurosigma I 30&
INDEX TO PLATES
409
FLATS PAGB
Plumatella XVIII 379
Polyarthra XVI 370
Pdyedrium VI 329
Potamogeton XIX 384
Protococcus VI 328
Raphidium VI 328
Raphidomonas XII 352
Rivularia V 317, 324
Rotifer XV 368
S
Saccharomyces X 343
Saprolegnia XI 343
Scenedesmus VI 329
Schi2X)nema I 306
Sc3rtonema V 323
Sida XVni 376
Sirosiphon V 323
5>orastrum VI 330
Sphaerozosma IX 336
Sphaeiozyga V 321
Spirogyra IX 326, 336
Spcmgclla XVIII 382
Staurastrum VIII 298, 334
Staurogenia VI 330
Stauroneis I 306
Stentor XIV 360
Stq>hanodiscus Ill 310
Stigeoclonium X 2q8, 339
Surirella Ill 38^
Synchaeta XVI 369
Syncrypta XII 354
Synedra II 308
Synura XII 354
T
PLATS PAOS
Tabellaria HI 309
Tetmemonis VII 334
Tetrapedia 320
Tetraspora V 327, 335
Tintinnus XIII 360
Trachcloccrca XIV 362
Trachelomonas XII 353
Triarthra XVI 370
Trinema XI 350
Tubella 38a
Tubifex 384
U
Ulothrix IX 338
Uroglena XII 354
Utricularia 384
Uvella XII 354
V
Vaucheria IX 337
Volvox VII 331
Vorticella XHI 346, 359
X
Xanthidium VIII 334
Z
2^thamnium 359
Zygnema IX 326, 337
Zygogonium IX 337
PLATE I.
DIA TOM A CE^E.
PLATE I
DlATOMACEiE
Magnification 500 diameters
Fie. A. Navicula viridis, valve view. '* B. Navicula viridis, girdle view. *' C. Navicula viridis, transverse section.
J, Outer, or older valve. A, Inner, or younger valve, f, c\ Connective bands, or girdles, d, Central nodule, rr, Terminal nodules. /, Kai)h6. i:. Furrows, w, Chromatophore plates. », Nucleus. 0, Oil globuk^s. p, Cavities. i<, Protoplasm. Figs. D, E, F. Navicula viridis, sectional views showing multiplication by divi- sion. After Deby. a. Valve. /;, Ciirdle. c, Protoplasm. </, Chromatophore plates. <•, Central cavities. /, Nucleus and nucleolus, f , Oil globules.
PACE
ig. I . Am|>hora , valve view 305
2. Amphoni, girdle view 305
3. Cymbdlu, valve view 305
4. CymbcUa, valve view 305
5. Kncyonema. .1 , valve view. B^ girdle view 305
(). Cocconema. ,1 , valve view. B, girdle view 305
7. Navicula grarijis, valve view 306
S. Navicula Rhyncocephara, valve view 306
g, Siauroneis, valve view 306
10. Stauroneis, girdle view 30ft
1 1 . Pleurosigma, valve view 30^)
1 2. (i()m|)h()nema. .1 , valve view. B^ girdle view 3Cf>
13. C'occoneis, valve view 307
14. CoK oiK'is. girdle view 307
1 5. Mpitheinia, valve view 307
lO. ICpitlu'inia. girdle view 307
1 7. KuiU)tia, valve vicv 307
PLATE I .
g
m\\\m\mm\m\miwmff/m/^^.
''"iii'wfniwnuihwiiimxixiiimmxm^
B
m p n 0
1 1 1 "l 1 1
10
"zSZZZ}
f â– -,
m— O t ■»» !»■»■■■"r^
8
I
ccw.*/
17 rw^:'- ''!• ■i'^»wittP.^'':Hijwfcii«>--^
\
PLATE II.
DIATOMACEyE,
PLATE II
DIATOMACE.^ Maf^nification 500 diameters
PAGB
FiR. I. Ilimantidium, vaivv view 308
2. Himantidium, girdle view 308
3. Astcrionella, valve view 308
4. Astcrionella, girdle view (typical form) 308
5. Astcrionella, girdle view, showing division of the cells 30S
6. Astcrionella, girdle view, showing rapid multiplication 308
7. Astcrionella. A , valve view. B, girdle view 308
8. Syncdra i)ulchclla, valve view 30S
g. Syncdra pulchclla. girdle view 30S
ID. Syncdra ulna, viUve view 308
11. Syncdra ulna, girdle view 308
1 2. Fragilaria, girdle view 308
13. Fragilaria, valve view 308
PLATE 111.
VIATOMACEjE.
PLATE III
DIATOMACE^E
Magnification 500 diameters
PAGB
Fig. I. Diatoma vulgarc, valve view 309
2. Diatoma vulgare, girdle view 309
3. Diatoma tenue, girdle view 309
4. Meridion circulare, valve view 309
5. Meridion circulare, girdle view 309
6. Tabcllaria fenestrata, valve view 309
7. Tabcllaria fenestrata, girdle view 309
8. Tabcllaria flocculosa, valve view 309
9. Tabcllaria flocculosa, girdle view 309
10. Nitzschia sigmoida, valve view 309
11. Nitzschia sigmoida, girdle view 309
1 2. Nitzschia longissima, girdle view 309
13. Surirella, valve view 300
14. Surirella, girdle view 309
15. Melosira, valve view 310
16. Mclosira. girdle view 310
17. Mclosira auxospore 310
18. Cyclolclla, valve view 310
19. Cyclotclla, girdle view 310
20. Slcphanodiscus, valve view 310
21. Slcphanodiscus, girdle view 310
PLATE I
:.{ "•}, 3
\ 10 1
I3^«». 14
6 __,,.--
19 _
18 : - O 18
20 , . - . 21
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PLATE IV.
SCHIZOMYCETES. CYANOPHYCE^.
1 1 it
PLATE IV
SCHIZOMVCKTES Magnification 500 diameters
PAGE
Fig. I. Leptothrix 312
2. Cladothrix, showing false branching 312
3. Bcggiatoa 313
4. Crenothrix. A , filament enclosed in sheath. B^ filament with sheath
removed, showing liberation of spores 313
CYANOPIIYCi:.4!:
Magnification 500 diameters
Fig. 5. Chro()r<x\us 318
6. (il(e<H'aps:i 31S
7. Aphancxapsji 310
8. Microcystis 310
9. Clathrocystis 31Q
10. C(rl<)spha;rium 310
11. Mcrismoiwdia 31Q
12. Nosloc 321
13. Anaha'iia llos-acjua* 321
14. Anabxna circinalis 321
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PLATE IV.
PLATE V.
C YANOPHYCE^. CHLOROPHYCEyE.
PLATE V
CYANOPHYCKiE Magnification 500 diameters
PACt
Fig. I. Sphxrozyga 321
2. Cylindrospcmium 322
3. Aphanizomenon 322
4. Oscillaria 32a
5. Lyngbya 322
6. Microcoleus 325
7. Srytonema 323
8. Sirosiphon 323
9. Rivularia, a single filament 324
CHLOROPHYCE.^!:
Magnification 500 diameters
Fig. 10. GIncocystis 327
11. Palmella 327
12. Tclruspora 327
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PLATE V.
U^
PLATE VI.
CHLOROPH YCE^.
PLATE VI
CHLOROPHYCE.«
*
Magnification 500 diameters (except Fig. 9)
PACK
Fig. I . Botryococcus 328
2. Ruphidium 328
3. Dictyosphairium 3 28
4. Ncphrocytium 328
5. I)imon)hocxKxus 328
6. ProtOLX)tTUs 328
7. Polycdriiim 32Q
8. Sccncdcsmus 329
9. Hydrodictyon. X 250 329
10. Ophiocytium 329
1 1 . Pcdiaslrum 329
1 2. Sorastrum 330
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PLATE VII.
CHLOROPH YCEyE.
PLATE V.
C YANOPHYCE^. CHLOROPHYCEyE.
PLATE V
CYAXOPHYCK.E
Magnification 500 diameters
rAGB
Fig. I. Sphaerozyga 321
2. Cyfindrospcrmum 322
3. Aphanizomenon 322
4. Oscillaria 322
5. Lyngbya 322
6. Microcoleus 325
7. Scytoncma 323
8. Sirosi|)h()n 323
9. Rivularia, a single filament 324
CIlLOROPHYCE.t
Magnification 500 diameters
Fig. 10. Olococystis 327
" II. Palmella 327
' * 12. Tctras|M)ra 327
PLATE V.
0-4^^
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PLATE VI
CHLOROPHYCE^
«
Magnification 500 diameters (except Fig. 9)
PAGR
Fig. I. Botryococcus 328
2. Rai)hidium 328
3. Dictyosphairium 328
4. Nephrocytium 328
5. Dimorphococcus 328
6. ProtoaxTUs 328
7. Polyedrium 32Q
8. Sccnedcsmus 3 2q
Q. Ilydrodictyon. X 250 329
10. Ophiotylium 329
11. Pcdiastrum 329
1 2. Sorastrum 330
PLATE VI.
CHLOROPH YCE^.
PLATE VII.
CHLOROPHYCEM.
PLATE VII
CHLOROPHYCEi€
TACB
Fi«. I . (!cclaslrum. X 500 330
2. SliiuroRcnia. X 500 330
3. Volvox. X 100 331
4. Kudorina. X 250 ^ 331
5. Pandorina. X 250 331
6. (Jonium. <j, lop view, h, side view. Xsoo ji^^
7. Penium. X 250 333
8. Closlerium T)iana*. X250 . . ,-^^^^^
Q. (MosttTium Khrcnberj^ii. X 250 ^^^^\
10. Clostcrium suf jlile. X -?50 ^^^^
11. Docidium. X250 ^^j^^^
1 2. Cosniarium. X .'50 ^33
13. Tctnu-morus. X 250 334
PLATE V.
C YA NOPH 1 'CE^. CHLOROPH YCE^.
PLATE VIII.
CHLOROPHYCE^.
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PLATF !X.
CHLOROPHYCE^.
PLATE IX
CHLOROPHYCE.E
PAGE
Fig. I. Hyalotheca. a, filament. 6, end view. Xsoo 334
2. Desmidium. a, filament. 6, end view. Xsoo 336
3. Spha;rozosma. <i, filament. 6, end view. Xsoo 336
A. Spirogyra. Xi2S 336
5. Spiropyra, conjugated form, showing spores. Xi2S 336
6. ZvKnema. X 1 25 337
7. Vaucheria. X 100 337
8. Conferva. X 1 25 338
g. Cladophora. X 75 338
10. Ulothrix. X 1 25 338
PLATE X.
CHLOROPHYCE^E. FUNGI.
PLATE X
CHLOROPHYCE/E
PAGE
Fig. I. Drapamaldia. X 1 25 339
2. Stigeorlonium. X 1 25 339
3. Chaetophora. X 1 25 339
FUNGI
it
Fig. 4. Saccharomyccs. X500 342
' * 5. Mold hyphai. X 25c 34 2
'* 6. Peniclllium. X250 342
7. Aspergillus. X250 342
8. Mucor. X 250 343
I
PLA1 E XI.
FUXGJ. PROTOZOA.
PLATE XI
FUNGI
PAGB
Fig. I. Saprolegnia. X 250 343
" 2. Achlya. X2S0 343
* * 3. Leptomitus. Xsoo 343
PROTOZOA
Fig. 4. Amoeba. X 250 *. 348
* * 5. Arcclla, lateral view. X 250 349
* * 6. Arrella, interior view. X 250 349
'* 7. Dilllugia. X250 349
' * 8. EuKly|)ha. X 250 349
** 9. Trinema. X250 350
** 10. Actinophrys. X250 350
PLATE XI
I
PLATE XII.
PROTOZOA.
PLATE XII
PROTOZOA
PAGE
Fig. I. Cercomonas. X500 351
** 2. Monas. X500 352
** 3. Anthophysa. X500 352
' * 4. Coelomonas. X 500 352
* * 5. Raphidomonas. X 500 352
** 6. Euglena. X500 353
* ' 7. Trachelomonas. X 500 353
' * 8. Phacus. X 500 353
' * 9. Synura. X 500 354
* * 10. Uvella. X 500 354
** II. Syncr>i)ta. X500 354
' * 12. Uroglcna. X 250 354
" 13. Uroglcna; showing division of the monads. Xiooo 354
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PLATE XIU.
PROTOZOA.
f I
PLATE XI
FUNGI
PAGE
Fig. I. Saprolcgnia. X 250 343
2. Achlya. X 250 343
3. Lcptomitus. Xsoo 343
PROTOZOA
Fig. 4. Amoeba. X 250 *. 348
5. Arcclla, lateral view. X 250 349
6. Arcellii, interior view. X 250 349
7. DitlluKia. X250 34Q
8. Eu^lypha. X 250 349
g. Trinema. X 250 350
10. .\rtinophrys. X 250 350
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PLATE XI
(
PLATE XU.
PROTOZOA.
PLATE XIV
PROTOZOA
PACE
Fig. I. Codonclla. X500 360
** 2. Stentor. Xso 3C0
*' 3. Bursaria. Xioo 361
** 4. Paramecium. Xas© 301
'* 5. Nassula. X2S0 362
** 6. Colcps. X500 362
* * 7. Knchclys. X 500 362
' * 8. TracheloccTca. X 500 362
*' 9. Pleuroncma. X500 362
PLATE XIV.
â„¢ ^
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PLATE XV.
PROTOZOA. ROTIFERA.
PLATE XV
PROTOZOA
PAGE
Fig. I. Colpidium. Xsoo 363
** 2. Acineta. X500 363
ROTIFERA
Fig. 3. Floscularia. X 25 367
4. Melicerta, X 25 368
5. Conochilus. X 100 368
6. Rotifer. X 100 368
7. MicTocodon. X 150 369
8. Asplanchna. X 150 369
PLATE XV
/
PLATE XVI.
ROTIFERA.
PLATE XVI
Figs. A to E. Diagrams of Trochal Disc. (After Bourne.)
A, Microcodon. B, Stephanoceros. C, Hypothetical form inter- mediate between Microcodon and Philodina. D, Philodina. E, Brachionus. Figs. F to I. Diagrams showing Structure of the Foot. (After Hudson and
Gosse.) F, Rhizotic foot (Floscularia). G, Rhizotic foot (Melicerta). H, Bdelloidic foot (Rotifer). I, Scirtopodic foot (Pedalion). Figs. J to P. Diagrams showing Forms of Trophi. (After Hudson and Gosse.) J, Malleate. K, Sut>mallcate. L, Forcipitate. M, Incudate. N, Uncinate. O, Ramate. P, Malleoramate.
ROTIKKRA
PAGB
Fig. I. Synchaita. Xioo 3OQ
2. Polyarthra. X 200 370
3. Triarthra. X150 370
4. Diglena. Xiso 370
5. Mastigocerca. Xiso 371
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PLATE XVII.
ROTIFERA. CRUSTACEA.
PLATE XVII
ROTIFKRA
PAGE
Fig. I. Brachionus. X200 371
2. Anura*a aKhlcaris. /I, dorsal view, i5, side view. X150 371
3. Anunea aculeata. X150 371
4. Notholca. X200 371
1
CRUSTACKA
ig. 5- Cyclop-i. X 25 374
(). Diaptomus. X25 375
7. CanthcK'amptus. X-\S 375
8. Cypris. X25 375
(). Daphnia. X 25 370
10. Bosmina. X25 376
PLATE XVII.
PLATE XVIII.
CRUSTACEA. JiRYOZOA. SPONGIDyE.
PLATE XVIII
CRUSTACEA
PAGE
Fic. I. Sida. Xas 376
** 2. Chydorus. X 25 376
** 3. Branchipus. X 2 376
BRYOZOA
Fig. 4- Frcdcricclla. X 5 379
* * 5. Paludicclla. X5 379
* * 6. Statoblast of Plumatella. X 25 379
** 7. Statoblast of Pcctinalclla. X 25 379
SPOXC;iI)/K
Fii;. S. S|X)nRilla. X i 381
** 9. Sjwngc spicules (skeleton spicules). X 150 38 1
PLATE XVIII.
PLATE XIX.
MISCELLANEOUS.
PLATE XIX
MISCELLANEOUS
PACB
Fig. X. Anguillula. Xioo 384
2. Nais. X 10 384
3. Chaetonotus. X250 384
4. Macrobiotus. X250 384
5. Acarina. X25 384
6. Hydra. X 25 384
7. Batrachospcrmum. X 100 384
8. Cham. X 75 384
9. Anacharis. X i 384
10. Ceratophyllum. X i 384
11. Potamogcton. Xi 384
1 2. Lcmna. X i 384
1
LANE MEDICAL LIBRARY
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JAN 22 '25
OCT 12'25