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The life of
1& The life of inland waters
6205 FRANKTOWN ROAD
CARSON CITY, NEVADA 19701
THE LIFE OF INLAND WATERS
SEASONAL CHANGES ON
The view is from West Hill, looking across the head
Field Station towards the
THE RENWICK MARSH AT ITHACA
of Cayuga Lake and the grounds of the Biological
Campus of Cornell University.
An elementary text book of fresh-water
biology for students
JAMES G. NEEDHAM
Professor of Limnology in Cornell University
J. T. LLOYD
Formerly, Instructor in Limnology in Cornell University
c205 FRANKTOWN ROAD
CARSON CITY, I^VADA 897W
ITHACA ^SOKS^ NEW YORK
COMSTOCK PUBLISHING COMPANY, INC.
COPYRIGHT, 1937, BY
COMSTOCK PUBLISHING CO., INC.
PRINTED IN THE UNITED STATES OF AMERICA
THE COLLEGIATE PRESS ' MENASHA ' WISCONSIN
IN THE following pages we have endeavored to present a
brief and untechnical account of fresh-water life, its forms,
its conditions, its fitnesses, its associations and its economic pos-
sibilities. This is a vast subject. No one can have detailed
first hand knowledge in any considerable part of it. Hence,
even for the elementary treatment here given, we have borrowed
freely the results of researches of others. We have selected out
of the vast array of material that modern limnological studies
have made available that which we deem most significant.
Our interests in water life are manifold. They are in part
economic interests, for the water furnishes us food. They are
in part aesthetic interests, for aquatic creatures are wonderful to
see, and graceful and often very beautiful. They are in part
educational interests, for in the water live the more primitive
forms of life, the ones that best reveal the course of organic evolu-
tion. They are in part sanitary interests; interests in pure
water to drink, and in control of water-borne diseases, and of
the aquatic organisms that disseminate diseases. They are
in part social interests, for clean shores are the chosen places for
water sports and for public and private recreation. They are
in part civic interests, for the cultivation of water products for
human food tends to increase our sustenance, and to diversify
our industries. Surely these things justify an earnest effort to
make some knowledge of water life available to any one who may
The present text is mainly made up of the lectures of the senior
author. The illustrations, where not otherwise credited, are
mainly the work of the junior author. Yet we have worked
jointly on every page of the book. We are indebted for helpful
suggestions regarding the text to Professors E. M. Chamot, G. C.
Embody, A. H. Wright, and to Dr. W. A. Clemens. Miss Olive
Tuttle has given much help with the copied figures.
Since 1906, when a course in general limnology was first estab-
lished at Cornell University, we have been associated in develop-
ing an outline of study for general students and a program of
practical exercises. The text-book is presented herewith : the prac-
tical exercises are incorporated in a small brochure by J. G. and
P. R. Needham entitled Guide to the Study of Fresh-Water Biology.
The limitations of space have been keenly felt in every chapter;
especially in the chapter on aquatic organisms. These are so
numerous and so varied that we have had to limit our discussion
of them to groups of considerable size. These we have illustrated
in the main with photographs of those representatives most
commonly met with in the course of our own work. Important
groups are, in some cases, hardly more than mentioned; the stu-
dent will have to go to the reference books cited for further infor-
mation concerning them. The best single work to be consulted
in this connection is the American Fresh-Water Biology edited by
Ward and Whipple and published by John Wiley and Sons.
Our bibliography, necessarily brief, includes chiefly American
papers. We have cited but a few comprehensive foreign works;
the reference lists in these will give the clue to all the others.
It is the ecologic side of the subject rather than the sys-
tematic or morphologic, that we have emphasized. Nowadays
there is being put forward a deal of new ecologic terminology
for which we have not discovered any good use; hence we have
Limnology in America today is in its infancy. The value of
its past achievements is just beginning to be appreciated. The
benefits to come from a more intensive study of water life are
just beginning to be disclosed. That there is widespread interest
is already manifest in the large number of biological stations at
which limnological work is being done. From these and other
kindred laboratories much good will come; much new knowledge
of water life, and better application of that knowledge to human
JAMES G. NEEDHAM
J. T. LLOYD.
The study of water life, p. 14. Epoch-making events: the invention of the
microscope, p. 15. The publication of the Origin of Species, p. 17. The
discovery of plancton, p. 18. Agencies for the promotion of the study
of limnology, p. 20. Biological field-stations, p. 23.
The Nature of Aquatic Environment
I. Properties and uses of water: p. 25. Transparency, p. 26. Stratification,
p. 31. The yearly cycle, p. 35. The thermocline, p. 37. The contents
of natural waters, p. 40.
//. Water and land, p. 55.
Types of Aquatic Environment
I. Lakes and ponds: p. 59. Lakes as temporary phenomena, p. 60. The
Great Lakes, p. 63. The Finger Lakes, p. 64. The lakes of the Yahara
valley, p. 66. Flood plain lakes, p. 67. Solution lakes and ponds, p. 68.
Depth and breadth, p. 71. High and low water, p. 74.
//. Streams: p. 77. Gradient of stream beds, p. 77. Ice, p. 81. Silt, p. 84.
Current, p. 85. High and low water, p. 87.
///. Marshes, swamps and bogs: p. 89. Cat-tail marshes, p. 91. The
Okefenokee Swamp, p. 93. Climbing bogs, p. 94. Muck and peat,
p. 95. High and low water, p. 96.
I. Plants: p. 99. i. Water plants, p. 100. The Algae, p. 101. Chloro-
phylless water plants, bacteria and fungi, p. 139.
2. The higher plants, p. 145. The mossworts, p. 146. The fernworts,
p. 149. Aquatic seed plants, p. 151.
II. Animals: p. 158. Protozoans, p. 159. The lower invertebrates, p. 163.
Arthropods, p. 183. Insects, p. 195. Vertebrates, p. 231.
Adjustment to Conditions of Aquatic Life
I. Individual adjustment: p. 242. i. Life in the open water, p. 243.
Flotation, p. 243. Swimming, p. 249.
2. Life on the bottom, p. 251. Adjustment to shore life, p. 251. Avoid-
ance of silt, p. 252. Burrowing, p. 254. Shelter building, p. 257. With-
standing current, p. 258.
3. Adjustment of the life cycle, p. 261. Encystment, p. 262. Winter
eggs, p. 265. Readaptations to aquatic life, p. 269. Plants, p. 269.
Animals, p. 273.
//. Mutual adjustment: p. 282. Insectivorous plants, p. 283. The larval
habits of fresh- water mussels, p. 287.
I. Limnetic societies: p. 293. i. Plancton, p. 295. Seasonal range, p. 302.
Plancton pulses, p. 305. Distribution in depth, p. 307.
2. Necton, p. 313.
//. Littoral societies: p. 314. i. Lenitic societies, p. 315. Plants, p. 318.
Animals, p. 324. Spatial relations of lenitic animals, p. 326. Life in
some typical lenitic situations, p. 333. Pond societies, p. 334. Marsh
societies, p. 341. Bog societies, p. 348. Stream beds, p. 356.
2. Lotic societies, p. 363. Plancton gatherers, p. 364. Ordinary foragers,
Inland Water Culture
I. Aboriginal water culture, p. 377.
II. Water crops: p. 379. Plants, p. 379. Animal products, p. 382. Fish
culture, p. 384. The forage problem, p. 387. Staple foods, p. 389. The
way of economic progress, p. 399.
Contents 1 1
III. Water culture and civic improvement: p. 401. Reclamation enterprises,
p. 401. Waste wet lands, p. 402. Reservoir sites, p. 403. Scenic Im-
provements, p. 404. Private water culture, p. 406. Swamp reserva-
tions, p. 408.
Bibliography p. 413
List of initials and tail-pieces p. 420
Index p. 42 1
INDIANS GATHERING WILD RICE, N. MINNESOTA
I HE home of primeval man was
by the waterside. The springs
quenched his thirst. The bays
afforded his most dependable
supply of animal food. Stream-
haunting, furbearing animals
furnished his clothing. The
rivers were his highways. Water
sports were a large part of his recreation; and the
glorious beauty of mirroring surfaces and green flower-
decked shores were the manna of his simple soul.
The circumstances of modern life have largely
removed mankind from the waterside, and common
needs have found other sources of supply; but the
primeval instincts remain. And where the waters are
clean, and shores unspoiled, thither we still go for rest,
and refreshment. Where fishes leap and sweet water
lilies glisten, \yhere bull frogs boom and swarms of
May-flies hover, there we find a life so different from
that of our usual surroundings that its contemplation
is full of interest. The school boy lies on the brink of a
pool, watching the caddis worms haul their lumbering
cases about on the bottom, and the planctologist plies
his nets, recording each season the wax and wane of
generations of aquatic organisms, and both are satisfied
The study of water life, which is today the special
province of the science of limnology*, had its beginning
in the remote unchronicled past. Limnology is a
modern name ; but many limnological phenomena were
known of old. The congregating of fishes upon their
spawning beds, the emergence of swarms of May-flies
from the rivers, the cloudlike flight of midges over the
marshes, and even the "water bloom" spreading as a
filmy mantle of green over the still surface of the lake- -
such things could not escape the notice of the most
casual observer. Two of the plagues of Egypt were
limnological phenomena; the plague of frogs, and the
plague of the rivers that were turned to blood.
Such phenomena have always excited great wonder-
ment. And, being little understood, they have given
rise to most remarkable superstitions, f Little real
*Limnos = shore, waterside, and logos = a treatise: hydrobiology.
f The folk lore of all races abounds in strange interpretations of the simplest
limnological phenomena; bloody water, magic shrouds (stranded "blanket-
, algae"), spirits dancing in waterfalls, the "willo' the wisp" (spontaneous com-
bustion of marsh gas), etc. Dr. Thistleton Dyer has summarized the folk lore
concerning the last mentioned in Pop. Sci. Monthly 1 9 : 67, 1 88 1 . In Keightly 's
Fairy Mythology, p. 491 will be found a reference to the water and wood maids
called Rusalki. "They are of a beautiful form with long green hair: They
swing and balance themselves on the branches of trees, bathe in lakes and
rivers, play on the surface of the water, and wring their locks on the green
mead at the water's edge." On fairies and carp rings see Theodore Gill in
Smithsonian Miscellaneous Collections 48:203, 1905.
knowledge of many of them was possible so long as the
most important things involved in them often even
the causative organisms could not be seen. Progress
awaited the discovery of the microscope.
The microscope opened a new world of life to human
eyes "the world of the infinitely small things." It
revealed new marvels of beauty everywhere. It dis-
FIG. i. Waterbloom (Euglena) on the surface film of the Ren wick
lagoon at Ithaca. The clear streak is the wake of a boat just passed.
covered myriads of living things where none had been
suspected to exist, and it brought the elements of
organic structure and the beginning processes of
organic development first within the range of our
vision. And this is not all. Much that might have
been seen with the unaided eye was overlooked until
the use of the microscope taught the need of closer
looking. It would be hard to overestimate the stimu-
lating effect of the invention of this precious instrument
on all biological sciences.
1 6 Introduction
With such crude instruments as the early micro-
scopists could command they began to explore the world
over again. They looked into the minute structure of
everything forms of crystals, structure of tissues,
scales of insects, hairs and fibers, and, above all else,
the micro-organisms of the water. These, living in a
transparent medium, needed only to be lifted in a drop
of water to be ready for observation. At once the early
microscopists became most ardent explorers of the
water. They found every ditch and stagnant pool
teeming with forms, new and wonderful and strange.
They often found each drop of water inhabited. They
gained a new conception of the world's fulness of life
and one of the greatest of them Roesel von Rosenhof ,
expressed in the title of his book, "Insekten Belusti-
gung"* the pleasure they all felt in their work. It was
the joy of pioneering. Little wonder that during a
long period of exploration microscopy became an end
in itself. Who that has used a microscope has not been
fascinated on first acquaintance with the dainty ele-
gance and beauty of the desmids, the exquisite sculptur-
ing of diatom shells, the all-revealing transparency of
the daphnias, etc., and who has not thereby gained a
new appreciation of the ancient saying, Natura maxime
miranda in minimis.\
Among these pioneers there were great naturalists
Swammerdam and Leeuwenhoek in Holland, the latter,
the maker of his own lenses; Malpighi and Redi in
Italy; Reaumer and Trembly in France; the above
mentioned, Roesel, a German, who was a painter of
miniatures; and many others. These have left us
faithful records of what they saw, in descriptions and
figures that in many biological fields are of more than
historical importance. These laid the foundations of
*Belustigung = delight.
fNature is most wonderful in little things.
Important Events 17
our knowledge of water life. Chiefly as a result of their
labor there emerged out of this ancient "natural
philosophy" the segregated sciences of zoology and
botany. Our modern conceptions of biology came
later, being based on knowledge which only the per-
fected microscope could reveal.
A long period of pioneer exploration resulted in the
discovery of new forms of aquatic life in amazing
richness and variety. These had to be studied and
classified, segregated into groups and monographed,
and this great survey work occupied the talents of
many gifted botanists and zoologists through two
succeeding centuries indeed it is not yet completed.
But about two centuries after the construction of the
first microscope, occurred an event of a very different
kind, that was destined to exert a profound influence
throughout the whole range of biology. This was the
publication of Darwin's Origin of Species. This book
furnished also a tool, but of another sort a tool of the
mind. It set forth a theory of evolution, and offered
an explanation of a possible method by which evolution
might come to pass, and backed the explanation with
such abundant and convincing evidence that the
theory could no longer be ignored or scoffed out of
court. It had to be studied. The idea of evolution
carried with it a new conception of the life of the world.
If true it was vastly important. Where should the
evidence for proof or refutation be found? Naturally,
the simpler organisms, of possible ancestral character-
istics, were sought out and studied, and these live in the
water. Also the simpler developmental processes, with
all they offer of evidence; and these are found in the
water. Hence the study of water life, especially with
regard to structure and development, received a mighty
impetus from the publication of this epoch-making book.
The half century that has since elapsed has been one of
unparalleled activity in these fields.
1 8 Introduction
Almost simultaneously with the appearance of
Darwin's great work, there occurred another event
which did more perhaps than any other single thing to
bring about the recognition of the limnological part of
the field of biology as one worthy of a separate recogni-
tion and a name. This was the discovery of planet on
that free-floating assemblage of organisms in great
water masses, that is self -sustaining and self -maintaining
and that is independent of the life of the land. Lilje-
borg and Sars found it, by drawing fine nets through
the waters of the Baltic. They found a whole fauna
and flora, mostly microscopic a well adjusted society
of organisms, with its producing class of synthetic
plant forms and its consuming class of animals; and
among the animals, all the usual social groups, herbi-
vores and carnivores, parasites and scavengers. Later,
this assemblage of minute free-swimming organisms
was named plancton.* After its discovery the seas
could no longer be regarded as "barren wastes of
waters"; for they had been found teeming with life.
This discovery initiated a new line of biological explora-
tion, the survey of the life of the seas. It was simple
matter to draw a fine silk net through the open water
and collect everything contained therein. There are
no obstructions or hiding places, as there are every-
where on land; and the fine opportunity for quantita-
tive as well as qualitative determination of the life of
water areas was quickly grasped. The many expedi-
tions that have been sent out on the seas and lakes of
the world have resulted in our having more accurate
and detailed knowledge of the total life of certain of
these waters than we have, or are likely to be able soon
to acquire, of life on land.
Prominent among the investigators of fresh water life
in America during the nineteenth century were Louis
*Planktos = drifting, free floating.
Aquatic Life 19
Agassiz, an inspiring teacher, and founder of the first
of our biological field stations; Dr. Joseph Leidy, an
excellent zoologist of Philadelphia, and Alfred C. Stokes
of New Jersey, whose Aquatic Microscopy is still a use-
ful handbook for beginners.
Our knowledge of aquatic life has been long accumu-
lating. Those who have contributed have been of very
diverse training and equipment and have employed
very different methods. Fishermen and whalers; col-
lectors and naturalists; zoologists and botanists, with
specialists in many groups; water analysts and sani-
tarians; navigators and surveyors; planktologists and
bacteriologists, and biologists of many names and sorts
and degrees; all have had a share. For the water has
held something of interest for everyone.
Fishing is one of the most ancient of human occupa-
tions; and doubtless the beginning of this science was
made by simple fisher-folk. Not all fishing is, or ever
has been, the catching of fish. The observant fisherman
has ever wished to know more of the ways of nature, and
science takes its origin in the fulfillment of this desire.
The largest and the smallest of organisms live in the
water, and no one was ever equipped, or will ever be
equipped to study any considerable part of them.
Practical difficulties stand in the way. One may not
catch whales and water-fleas with the same tackle, nor
weigh them upon the same balance. Consider the dif-
ference in equipment, methods, area covered and num-
bers caught in a few typical kinds of aquatic collecting:
(i). Whaling involves the cooperative efforts of
many men possessed of a specially equipped vessel. A
single specimen is a good catch and leagues of ocean
may have to be traversed in making it.
(2). Fishing may be done by one person alone,
equipped with a hook and line. An acre of water affords
area enough and ten fishes may be called a good catch.
(3). Collecting the commoner invertebrates, such as
water insects, crustaceans and snails involves ordinarily
the use of a hand net. A square rod of water is suffi-
cient area to ply it in; a satisfactory catch may be a
(4). For collecting entomostracans and the larger
plancton organisms towing nets of fine silk bolting-cloth
are commonly employed. Possibly a cubic meter of
water is strained and a good catch of a thousand speci-
mens may result.
(5). The microplancton organisms that slip through
the meshes of the finest nets are collected by means of
centrifuge and filter. A liter of water is often an ample
field for finding ten thousand specimens.
(6). Last and least are the water bacteria, which are
gathered by means of cultures. A single drop of water
will often furnish a good seeding for a culture plate
yielding hundreds of thousands of specimens.
Thus the field of operation varies from a wide sea to
a single drop of water and the weapons of chase from
a harpoon gun to a sterilized needle. Such divergencies
have from the beginning enforced specialization among
limnological workers, and different methods of studying
the problems of water life have grown up wide apart,
and, often, unfortunately, without mutual recognition.
The educational, the economic and the sanitary inter-
ests of the people in the water have been too often dealt
with as though they are wholly unrelated.
The agencies that in America furnish aid and support
to investigations in fresh water biology are in the main :
i. Universities which give courses of instruction
in limnology and other biological subjects, and some of
which maintain field stations or laboratories for investi-
gation of water problems. 2. National, state and
municipal boards and surveys, which more or less
constantly maintain researches that bear directly upon
their own economic or sanitary problems. 3. Socie-
ties, academies, institutes, museums, etc., which
variously provide laboratory facilities or equip expedi-
tions or publish the results of investigations. 4.
Private individuals, who see the need of some special
investigation and devote their means to furthering it.
The "Universities and private benefactors do most to
care for the researches in fundamental science. Fish
commissions and sanitary commissions support the
applied science. Governmental and incorporated insti-
tutions assist in various ways and divide the main work
of publishing the results of investigations.
It is pioneer limnological work that these various
agencies are doing; as yet it is all new and uncorre-
lated. It is all done at the instance of some newly
discovered and pressing need. America has quickly
passed from being a wilderness into a state of highly
artificial culture. In its centers of population great
changes of circumstances have come about and new
needs have suddenly arisen. First was felt the failure
of the food supply which natural waters furnished;
and this lack led to the beginning of those limnological
enterprises that are related to scientific fish culture.
Next the supply of pure water for drinking failed in our
great cities; knowledge of water-borne diseases came
to the fore: knowledge of the agency of certain
aquatic insects as carriers of dread diseases came in;
and suddenly there began all those limnological enter-
prises that are connected with sanitation. Lastly, the
failure of clean pleasure grounds by the water-side,
and of wholesome places of recreation for the whole
people through the wastefulness of our past methods of
exploitation, through stream and lake despoiling, has
led to those broader limnological studies that have to
do with the conservation of our natural resources.
ALL inorganic substances,
acting in their own proper
nature, and without assist-
ance or combination, water
is the most wonderful. If
we think of it as the source
of all the changefulness and
beauty which we have seen
in the clouds; then as the instrument by which the earth we have
contemplated was modelled into symmetry, and its crags chiseled into
grace; then as, in the form of snow, it robes the mountains it has
made, with that transcendent light which we could not have conceived
if we had not seen ; then as it exists in the foam of the torrent, in the