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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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• •
• •
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• • •
• • •
miss or
•RAuNwoiiTH a 00.
•OOK M/MUrACTUNtna
SnOOKLVN, N. V.
DEDICATED
TO
MY FATHER AND MOTHER
44236
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
■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
•>■ >•>. >
■'^^^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
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00
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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
■
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
?— ..V-i - — w- rr5^*- . .».^,j.-»"- - • ± ■* '^ - — .« IZ OI\Xr lO
'. - . . — ■.*;» ■ .." , '^^ *■ :r .•« . .-^i.t r .*:«•
■A.:::: :nr re::.; r-i> :
o
I^ nlkd
• w
-'; ■-
>
> . . V ..
— . . ^. « ^
-I.-OLIIOD of
^i Pate A
.v::oQ after
.1 <»
'- '• . K> >...»,
>. ibcT pnctical
.i S: \"Yr]k' gen-
: .V :cli fonn a
,c '.vi:er. It is
t-
'COO
00 cc
: o ^ G
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
.■vv*.v" :".:: :>.'^ cva*^'*^
-— r^ ^ • — ^ .^.:^- -. > — .V. X. ■ .^>. .c sJL.ct* acofpteu
■ 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-¥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
N-
IB-
/
-
\
.0
00"
\
^
f
\
/
^
\
7
I
;o
h"
';,
°i
;
V
».
n..
».
"
■^
.,.
..,
„.
FiO.37-
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-
r ^
TEH
..«T
7]
fr
fi I
A
=^
^
1
(
\%\
^
V.
«Jt
^
L.K,,
i
p
1 ^
'
:
L
;
S-SIi TEM^PERATURE
1 Of THE WATER
i
™«..0.,„„H
V
V
1
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.
,.
j-tL-i' •■
I?""*
:^
|..,-
^
^.
0"'
«^
J
/
TE
MPE
ATU
E3
j
LAK
H.TU
kTE
1
'
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
TEMPERATE TYPE
/ ^\
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%
■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
IPR*-
1 ::;;
»
/ ■ ■ :::■:,::...:
-■
«
^ I-: " (' :
J2 " "; j ;
1.:. ■ ■; 1
i-' ■
«0
j'^y^jaiL
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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tf)
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be
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o°.r§
1
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(
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. . • a
0 t
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bove
•
0 o<
w
Deep.
Shallow.
2
o
s
u
+0
•
s
O
Si
1
i-«
U
M
0.
H
u
s
Q
M
PL,
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
sssHssssH
■1 Aiunnhj Mmjoi
■p«[ii»l»M JO
1^
mL
Pllti :
SSn?5"^SSSX5
3i3SSS3srs:;
%r:5%'RSi%s5,nt
f^siSllSsJS*
iilgiliiiil
HICBOSCOPICOROAmSHS In LAKES AND BESERV0QI8 157
gS
i
■Wngnl ,o iO|..J
& s a a 5
s
s
s
nwM (o "a"?M
. . « 0 , . , -
o»»HV(iun.«si''on-a
■ft =£, s s r ^ ^
2
J'jS,"/J^"&iims
"
«)
".
■»I(M M»nbg
s
s
-l»j U! itltUa "B"Ji»AV
"
■s
■Wj Bi i,iiHa Bjnml-H
- " " " " ^ ' -
.,™,.TJiv.rA
? 1 ^ S 5 ■& -S S
■»I!H
^ ^ S =8 S? ? 5 8
JO jnnfl "<"i* "»A
till
III
i
is
s f s 1 = t ^ ^
€ S 3 i 1 S ? ^
8nilia^J"»n'»J<I
S, ■S !? S S 8
- "
1
1^
1 1
J
J
1
!
1
1
d
Z
f
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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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
■urloce, wbeie the direct sunligbt naa tcN> strong.
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Fig. s4-
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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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
■
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
'■ 6
9
;;
il
"
&
ifl;
i
S
i!
1?
511
47
Sadbury Reacrvolr
SurfK
jofi
*1
4
;;
61
46
^B■.
■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
■■
*
"
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''"™. P""™"' 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
Efe
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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
■
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
u^.
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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-
:-^r t:^^ r:'r'_-.r Liji ^-. — .^ -j^j. -K-^ie:- crows kojct 2s ii posses
tL-",-:v- ut :.;:^r. uji c-r^ iLe t'jt:zix ind waiier ii crows
ir. i*^.-t :ht -ri-T. t i: biih places- ib:»uds il ocrzrs Is^ier in the
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:
Cr.'.-- *. r - *. H ■ : ! K v^.'r.- ! r . : - * 1 1 r
J;.' r »: .:• K- '. !r . ::f nr
'II:. • I'-r.- >,-Lrv. :Sj loo
7 1> : '. y. _•::.; -1- . i i x 05
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.
IKTHE BUTON WtTED PIK •. TH£ CUKVEI RHEeEITTHE
MEIUHEt OF W(«n tHALYlEl FOH THt Yt..s »>1-g.
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I'lc. 71.
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 0¥ 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
■.^■^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
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HntT, L. 1879. Ueber den Principien und die Methodc der Mikroskopischen
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Farlow, W. G. 1880. On Some Impurities of Drinking Water Caused by
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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-
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Farlow, W. G. 1883. Relations of Certain Forms of Algc to Disagreeable
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MacDonald, J. D. 1883. A Guide to the Microscopical Examination of Drink-
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Potts, E. 1884. Fresh- water Sponges as Improbable Causes of the Pollution
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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
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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
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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-
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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-
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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
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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.
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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 ■ -,
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
u
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
< <
< (
< (
I (
( <
< t
< i
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
It
n
ti
n
I i
It
tt
I I
1 1
t <
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
m
'U
^^^
>
- ,,9 ^ U -
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^^
#
*
»»«%
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^.
Z7- , — : - -TT
•X .'-'H'- TL-T
,.■-•■• •«
.=..=L'
/ •■ *
■- J- • .*
;• »
■::.i 'irv
E F
v'/,.
Z
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
« ^ f) A
iKiii^
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
< t
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.
™ ^
W I
fll\W''\^^
i
'
I
/
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
n
/
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
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