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THE

SCIENCE- HISTORY
OF THE UNIVERSE

FRANCIS ROLT - WHEELER

Managing Editor

IN TEN VOLUMES

THE CURRENT LITERATURE PUBLISHING COMPANY
NEW YORK

1909

INTRODUCTIONS BY

Professor E. E. Barnard, A.M., Sc.D.,
Yerkes Astronomical Observatory.

Professor Charles Baskerville, Ph.D., F.C.S.
Professor of Chemistry, College of the City of New York.

Director William T. Hornaday, Sc.D.,
President of New York Zoological Society.

Professor Frederick Starr, S.B., S.M., Ph.D.,
Professor of Anthropology, Chicago University.

Professor Cassius J. Keyser, B.S., A.M., Ph.D.,
Adrain Professor of Mathematics, Columbia University

Edward J. Wheeler, A.M., Litt.D.,
Editor of 'Current Literature.'

Professor Hugo Munsterberg, A.B., M.D., Ph.D., LL.D.,
Professor of Psychology, Harvard University.

EDITORIAL BOARD

Vol. I — Waldemar Kaempffert,
'Scientific American/

Vol. II — Harold E. Slade, C.E.

Vol. Ill — George Matthew, A.M.,

Vol. Ill — Professor William J. Moore, M.E.,

Assistant Professor of Mechanical Engineering, Brooklyn

Polytechnic Institute.

Vol. IV — William Allen Hamor,

Research Chemist, Chemistry Department, College of the

City of New York.

Vol. V — Caroline E. Stackpole, A.M.,
Tutor in Biology, Teachers' College, Columbia University.

Vol. VI— Wm. D. Matthew, A.B., Ph.B., A.M., Ph.D.,

Assistant Curator, Vertebrate Paleontology, American

Museum of Natural History.

Vol. VI — Marion E. Latham, A.M.,
Tutor in Botany, Barnard College, Columbia University.

Vol. VII — Francis Rolt-Wheeler, S.T.D.

Vol. VII— Theodore H. Allen, A.M., M.D.

Vol. VIII— L. Leland Locke, A.B., A.M.,
Brooklyn Training School for Teachers.

Vol. VIII— Franz Bellinger, A.M., Ph.D.

Vol. IX— S. J. Woolf.

Vol. IX— Francis Rolt-Wheeler, S.T.D.

Vol. X — Professor Charles Gray Shaw, Ph.D.,
Professor of Ethics and Philosophy, New York University.

Leonard Abbott,
Associate Editor 'Current Literature/

Digitized by the Internet Archive

in 2012 with funding from

The Institute of Museum and Library Services through an Indiana State Library LSTA Grant

http://archive.org/details/sciencehistoryofv6rolt

THE

SCIENCE- HISTORY
OF THE UNIVERSE

VOLUME VI

ZOOLOGY

By DR. WM. D. MATTHEW

BOTANY
By MARION E. LATHAM

INTRODUCTION

By DIRECTOR WM. T. HORNADAY

Copyright, 1909, by
CURRENT LITERATURE PUBLISHING COMPANY

CONTENTS

PART I— ZOOLOGY
Introduction by Director Wm. T. Hornaday

CHAPTER PAGE

I Fabulous Zoology „ i

II Development and Distribution 7

III The Lower Invertebrates 17

IV The Higher Invertebrates 40

V Insect Social Communities 65

VI The Vertebrates — I. Fish 87

VII The Vertebrates — II. Reptiles 102

VIII The Vertebrates — III. Birds 125

IX The Vertebrates — IV. Mammals 135

PART II— BOTANY

I Early Developments of Botany 196

II Plant Structures 219

III Reproduction Structures 233

IV Taxonomic Botany 242

V Development of Morphology 263

VI Organogeny and Adaptation 280

VII Physiology of Plants 293

VIII Growth and Variation 304

vii

INTRODUCTION

Under favorable conditions, the study of animal life
becomes not only profitable to mankind, but also as musi-
cal as Apollo's lute. To know the animal life of the world
is to know the world. It is impossible for an intelligent
mind to grasp the principal animal forms of a given
country without at the same time acquiring a great store
of knowledge of that country's topography, soil, climate
and people.

The love of wild life springs eternal in the human
breast. It is as natural for every child to be interested
in animals as it is for every child to love the sound of
music. Sad to say, however, that natural love for zoology
often is completely stifled, or warped out of shape, by lack
of opportunity. Those who by force of circumstances are
compelled to grow up and live out their lives without
knowing the satisfaction that is derived from an intimate
acquaintance with at least one section of animal life,
lose much pleasure to which they legitimately are enti-
tled.

At no time in the history of the world has zoological

knowledge been so vitally important to mankind as it is

to-day. As animal life rapidly diminishes, its economic

value to man becomes more apparent. Fifty years ago

ix

x ZOOLOGY

the edible fishes, lobsters, oysters and clams were so abun-
dant that no one found it necessary to delve deeply into
the life history of any one of those groups. To-day, and
for the future, only the most careful conservation and
cultivation, based on precise zoological knowledge, can
preserve to man a continuous supply of those valuable
and delicious foods.

For twenty-five years the nation and the States have
been studying ichthyology earnestly and diligently, in
pursuance of their costly and toilsome efforts to kefep
up the great food supply of the poor — the edible fishes.
The demand in the United States for a flesh-food supply
that is cheaper than mammalian meat now engages the
efforts of more than 200,000 men, backed by $60,000,000
of capital; and the animal fish product has a value of
about $50,000,000. Each year about 1,400 million fish
eggs and live fishes are distributed by the United States
Bureau of Fisheries. Verily, ichthyology is something
more than a mere pastime for the angler or the student.
To-day it is on the same basis of human necessity as
is the growing of wheat and corn.

Fifty years ago few persons in America gave thought
to the study of insects, save as a pastime. During recent
years the ravages of insects have called forth a grand
army of entomologists, first to study the destroyers, and
then to fight them. To-day every farmer and fruit
grower, every forester and every park superintendent is
engaged in the great irrepressible conflict that is being
waged between Man and the Insect World for the pos-
session of the fruits, the vegetables, and the trees that
are as necessary to this earth as is the air we breathe.

INTRODUCTION xi

The monthly bulletins of the State Economic Zoologist
of Pennsylvania painfully bring home to us the appalling
extent and the fierceness of the battle for the trees.
Verily, the study of entomology has come to us to stay.

For twenty years the United States Government has
been engaged in a continuous effort to inform all the
people of the United States that the wild birds are man's
most valuable friends and allies in his warfare against
insect and mammalian pests.

Some communities hearkened gladly to the message,
and responded with reasonable promptness to the efforts
of the bird lovers in behalf of protective bird laws. A
few States remained hostile to bird laws until the cotton-
boll weevil and other pests sharply brought home to their
people the fact that they needed the assistance of the
birds.

Now that man's heedless and ignorant destructiveness
has accomplished the extinction during our own times of
a score of important animal species, and to-day is threat-
ening to annihilate many others, zoological knowledge
has suddenly become a practical necessity. Both to the
statesman and the citizen the protection of wild life has
become a solemn duty. Ignorance is dangerous alike
to our forests and streams and to our wild life.

The time has long passed wherein it was necessary to
justify by argument the existence of museums and the
study of zoology. The nature-study courses in our sec-
ondary schools testify abundantly to the public recogni-
tion of the need for the dissemination of zoological knowl-
edge.

Unfortunately, however, the workers in that field are

xii ZOOLOGY

as yet blindly groping for the methods by which they
may impart to the school pupils of America the precise
and practical animal lore that they need and desire.
To-day the nature-study teachers elect to relegate to the
background the great System of Nature in favor of a few-
actual objects in the classroom which the pupil can handle
and dissect, and use as a foundation of original pupil
philosophy. But the case is not wholly hopeless, for the
present situation is so bad that it cannot long endure.

After long and unsatisfactory contemplation of study
courses that mix together all sorts of living creatures
in one chaotic mass, it is a pleasure to take up a scholarly
work in which the methods of Nature are fully recog-
nised and clearly set forth. Herein the foundation stones
of Nature are assembled, and well and truly laid.

Fortunate is the young naturalist, and likewise the gen-
eral reader of animal lore, who early acquires the habit
of broad generalization. I am tempted to call it the
bird's-eye-view habit. Had I but one chance to send a
message to the young naturalists of the world, that mes-
sage would be this : Lay out for yourselves a broad foun-
dation of systematic knowledge, and after that each stone
of the structure will find its own permanent place as
joyously as running water seeks the lowest level.

It is impossible to insist too strongly upon the absolute,
vital necessity of conforming all zoological studies with
the great system of Nature. He who attempts to study
any small group of animal forms without first gaining
a bird's-eye view of the surrounding territory, and becom-
ing familiar with the zoological grand divisions that lie
around him, loses much. It is a mastery of the grand

INTRODUCTION xiii

divisions — the orders, families and genera, in particular —
that lends the greatest charm to the study of zoology.
The librarian who expects to store ten thousand books
in such a manner that each one may be instantly available,
wisely provides twenty-five alcoves and two hundred and
fifty shelves; and thereafter each new accession of books
is a source of joy, because the place for each volume is
ready. The young naturalist without a zoological founda-
tion is like a librarian who has no shelves and must create
a place for each new book.

But, after all, systematic zoological arrangement, or
"classification," is only to be regarded as a ready means
to the accomplishment of more important ends. To-day
the world is keenly concerned in the philosophy of ani-
mal life, its whys and its wherefores. A well-thought-
out exposition of the origin and relationships of animals
offers an excellent foundation for studies of species, and
of the habits and mental processes of individuals, that
shall continue and furnish human interest as long as any
wild life remains upon the earth.

The old question, "Where does the animal belong ?"
has now as a running mate the ever-present query, "What
does it think and do?" The latter offers to every intel-
ligent human being a delightful field of study and re-
search. The new question, "Do animals reason?" is no
longer a question, save with a very few persons to whom
the animal kingdom is mostly unknown territory. All
the men who are best acquainted with the living wild
animals of the world assert, as one man, that all animals
think and reason; that some think very little, others much;

xiv ZOOLOGY

and that some animals have reasoning faculties that are
superior to those of some men.

During recent years the work of our paleontologists
has been profoundly fruitful. In America the rocks of
the Western bad lands have yielded an extinct fauna of
a character so marvelous as to be almost incredible until
the actual remains are seen. It is quite beyond the power
of words to convey adequate conceptions of the reptilian
giants that formed the group of dinosaurs. The Bronto-
saurus, the Diplodocus, the Triceratops, the Stegosaurus
and the Tyrannosaurus all must be seen in order that
the wonders of them may be appreciated.

The story of the Jurassic Age in North America, as
told by those gigantic remains, is sufficient to awe the
most frivolous mind.

In the presence of those vast skeletons, some of them
so colossal that even the largest elephants of the present
^day seem small, the thoughtful observer finds a new realm
of knowledge opening before him like a panorama. The
animal kingdom takes on a solemn dignity and vastness
never known before. Naturally, the mind reaches out,
octopus-like, to fasten tentacles upon the Past and link
it to the Present.

There is one result of zoological knowledge that no man
can adequately set forth in words. It is the unending
satisfaction, and at times the delight, that comes through-
out the journey of life to every person who is able to
recognise the most important animals that are met by the
way. Except in mid-air, it is well-nigh impossible for
man to travel so far that he leaves behind him all visible
forms of animal life. I believe this has been accomplished

INTRODUCTION xv

only by the men who have pressed nearest to the poles,
through the utmost cold. He who knows the wild ani-
mals of the world always travels among friends, and in
every land he finds a welcome. To him the whole world
is interesting. To his pleasure in life thousands of beasts,
birds, and creeping things contribute. Nature's multi-
tude of interesting forms stimulate his efforts to acquire
knowledge, and her fields of research come the nearest to
revealing the fountains of perpetual youth.

To-day, the life of the_ ardent nature lover is filled
with activities. On the one hand there is the balance of
Nature to preserve, and on the other that lost balance is
to be restored. Those who are not engaged in fighting
the noxious forms of animal life are commonly found
on the firing-line of the army that is fighting the per-
petual war with those who would, if let alone, exterminate
all wild creatures from the whole earth. Let us hope that
millions of intelligent Americans will learn to appreciate
more fully the splendid fauna of this continent in time
to save it from the forces that now threaten it with anni-
hilation. William T. Hornaday.

ZOOLOGY

CHAPTER I

FABULOUS ZOOLOGY

The beginnings of Zoology lie in the region of fable.
In the earliest traditions and myths of primitive races the
world is peopled with men and animals, some real, some
half-real, some entirely fabulous. Natural and super-
natural are mingled together and a religious or supersti-
tious significance attaches to both real and unreal beings
seen or imagined by primitive man. His ready imagina-
tion and uncritical belief made the creations of his fancy
seem as real as those of his observation and experience.
With the increase of knowledge of the real, the unreal
became more and more relegated to the domain of folk-
lore and fable. Some of it has been preserved in the tradi-
tions and myths of different races, some crystallized in the
fanciful animals of decorative sculptures, paintings and
heraldry. Most of it has been forgotten.

It has been well observed that the imagination of man
does not really enable him to create anything new, but
only to recombine or rearrange what he has seen. He
may combine the body of a reptile with the wings of an
eagle; he may combine the head and shoulders of a man
with the body and legs of a horse or attach to a human
form the white wings of a swan. He may in fancy enlarge
a mouse to the size of an elephant or conceive of a serpent
large enough to encircle the whole world; he may support
the universe upon the back of an elephant of appropriate
i

2 ZOOLOGY

size. But all these are not new creations; they are objects
known to his experience, but recombined or altered in pro-
portions. It is only as he comes to realize with wider
knowledge that certain combinations of parts, certain
relations of size do not occur in nature, that these imagi-
nary beings become improbable or impossible. He is ac-
customed to supply the missing parts of half-seen animals
from his previous observations. He sees the head of a
deer projecting from the leafy wall of the forest and all
unconsciously pictures the rest of the quadruped from
what he has seen before; he sees a distant eagle perched
upon a crag and knows well enough that when it starts
to fly it will stretch out a pair of broad wings now closely
folded against the body and invisible in the distance. If
then he sees dimly outlined in the clouds a human form,
what more natural than to supply it with the long feath-
ered wings that belong to the birds of the air, or if at
night with the wings of the bats that infest his cave
dwelling? Nearly all of the fabulous monsters of zoology
belong to this early period. They have been handed down
conventionalized in form and degenerated into fable,
but originally they were just as real as the rest of the half-
seen, half-imagined world in which primitive man existed.
Perhaps the most familiar and universally known of
these fabulous animals is the dragon. It appears in all the
older myths of the Western nations in serpent form, usu-
ally winged, often with fiery or pestilential breath, the
deadly enemy and scourge of man. It is equally prominent
among the Eastern peoples, and probably received from
them its conventional form, the long hind legs, the great
eagle claws, the body covered with glittering armor scales,
the writhing tail and bat-like wings. Among the Medi-
terranean nations it appears first as a sea monster and
comes up out of the sea; wings were a later addition. In
the Northern myths it is at first a "worm" — i.e., a serpent
of gigantic size — and the conventional form is borrowed
later from the East.

FABULOUS ZOOLOGY 3

The fabulous Dragon had a real counterpart, singularly
close in some respects, in the extinct carnivorous Dino-
saurs of the Age of Reptiles. These gigantic reptiles were
not winged, indeed, but in the proportions of body, limbs
and tail, in the huge head and sharp teeth, the enormous,
sharp, eagle-like claws, possibly even in the glittering scaly
armor, some of them at all events might have sat for
a very tolerable portrait of the dragon of mythology. It
is a tempting explanation to suppose that some tradition of
these real monsters, handed down from primitive ances-
tors, was the basis of the dragon legends so widely scat-
tered among all races of men. But this theory must be
regretfully abandoned when the perspective of the geo-
logic record is examined. The last of the Dinosaurs be-
came extinct at the end of the Cretaceous Period, some
three million years ago at a moderate estimate, before the
evolution of the various races of modern quadrupeds had
begun, long before monkeys and apes had evolved out of
the primitive lemur-like animals from which they are
derived and long, long before the evolution of man. The
remote ancestors of the human race in the days of the
Dinosaurs were tiny shrew-like animals, inferior in intel-
ligence to almost any living quadrupeds, and millions of
years were to elapse before they slowly evolved a higher
intelligence and finally became capable of articulate
speech. So it is utterly impossible that a tradition could
have been handed down from the time when Dinosaurs
really existed.

Nor is it to be supposed that the dragon myths are based
upon discovery of their fossil remains, for in the millions
of years that have elapsed since their time the sand and
mud in which their remains were buried have been con-
verted into hard sandstone and shale and the bones so
thoroly petrified that they appear much like the rock itself.
They would not easily be recognised as bones at all, and
it would be quite out of the question for primitive man to
get any correct notion of the kind of animals they repre-

4 ZOOLOGY

sented if they happened to come across a few fragments
unearthed out of the rock. Dinosaur bones might con-
ceivably pass for bones of giants, but the concept of the
dragon could not possibly be founded upon them. There
remains a third explanation, that in some region of the
world Dinosaurs might have survived until more recent
times and have been seen by primitive men. But from
what is known of the geological history of life, this sup-
position is so exceedingly improbable as to amount to an
utter impossibility. One is obliged to conclude that the
dragon is wholly a creation of the imagination of man, its
source being probably among the races of Eastern Asia.
How and why it came to assume its present conventional
form would require a broad knowledge of the early his-
tory and mythology of these races to discern.

In the traditions of the Northern races the dragon
legends are engrafted upon the myth of the giant serpent,
the "Worm," which in the old Norse story encircles the
earth, lying at the bottom of the surrounding ocean. This
same myth, in another form, is handed down as the Sea
Serpent. Sea serpents, however, are easier to credit than
dragons, partly because less is known about the inhabi-
tants of the sea than those of the land, partly because
among the multitudinous forms of ocean life there are
many that correspond more or less with the preconceived
idea of what a sea serpent ought to be like. So that while
the dragon is confined to legend and no one professes to
have really seen one, there be many, down to the passen-
gers on modern ocean liners, who have testified to seeing
a sea serpent of approved type. Sometimes it may be one
of the large sea snakes, sometimes a ribbon fish or a school
of porpoises following one another as they leap out of the
water so as to give the impression of the rolling coils of a
great serpent. Sometimes a long streamer or tangle of
seaweed may look like the giant serpent with its maned
neck which all expect to see. Possibly among the un-
known inhabitants of the great deep some such animal

FABULOUS ZOOLOGY 5

may really exist. But until it is captured and its remains
deposited in some museum of natural history it must be
ranked among fabulous monsters.

The Unicorn of classical writers was a real animal ; the
great one-horned Rhinoceros of India, well known to
Eastern writers and not unfamiliar to the patrons of the
Greek or Roman circuses. In medieval Europe it suffered
a curious transformation. The Northern artist had never

Fig. i — Supposed 'Merman/
Long exhibited in Agassiz Museum, Boston, as an authentic
specimen.

seen a rhinoceros nor talked with any one who had. He
knew that it was a great four-legged beast with a long
horn on its forehead and the traditional foe of the lion.
So he grafted the twisted tusk of a narwhal on the fore-
head of a horse and in this form it was conventionalized in
heraldry, its source not recognised when, centuries later,
the rhinoceros was reintroduced to the knowledge of
Western nations.

6 ZOOLOGY

The various composite monsters of the mythology of
different races — the Centaurs and Sirens of the Greeks,
the Mermaids and Swan-maidens of Western Europe, the
winged bulls of Assyria or the eagle-headed gods of Egypt
— have all a more or less definite religious significance
and are theological rather than zoological myths. Some of
them have survived in zoological lore, supported, like the
sea-serpent, by the occasional sight of animals more or
less resembling what the observer expected to see and
their described appearance colored by the traditional de-
scription. Mermaids appear every now and then in the
accounts of medieval writers; some of the stories may
well have been based on the manatee or dugong, while in
more recent years actual specimens of stuffed mermaids,
manufactured by the ingenious Japanese from the fore
part of a monkey and the tail of a fish, have often been
exhibited.

To another class of zoological myths belong the in-
numerable fanciful stories told of the characters and
habits of real animals; of the transmutation of men into
animals and vice versa, and of the transformation of one
species of animal into another. Real metamorphosis of
form, as of the tadpole into the frog or of the larva into
the perfect insect, is well known to modern natural his-
tory, but however much or little a primitive ancestry may
have known about it, there seems to be no good reason to
believe that the enchantment-transformations of myth-
ology originated in any real observations of metamor-
phosis in nature. Dream experiences imperfectly sep-
arated from the recollections of waking hours had prob-
ably much to do with their conception. Hence it would
seem that while Natural History possesses relations which
may throw its beginnings to the fabulous monsters of
ancient times, the same cannot be said for the Science of
Zoology, which as a science requires evidence, and having
classified that evidence is loth to admit therein such mythi-
cal creatures who are undoubted aliens.

CHAPTER II

DEVELOPMENT AND DISTRIBUTION

The animal kingdom includes a vast variety of organ-
isms whose common basis of life is the cell. They are,
like plants, an organized community of cells. The va-
rious members of this community are adapted to per-
form different services, and many groups have specialized,
each for its particular function, so that the individual cells
are no longer capable of a separate life. The animal or
plant is thus not a mere aggregate of living cells, but an
organism. In the successive classes and orders of animals,,
from lowest to highest, there is a progressive complexity in
the organism, a more and more absolute and exact limita-
tion of the cells or groups of cells to special functions. This
progressive specialization is the key to the life history of
the individual organism, the development or 'ontogeny'
of the animal; and to the life history or 'phytogeny' of
the race.

All animals are to be regarded, then, as organized com-
munities, the units of these communities being protoplasm
cells, originally identical in structure and capable of all the
necessary activities of life, but specialized to perform par-
ticular functions. The first steps in the plan of organiza-
tion as they appear in the development of the individual
are identical in all animals.

The cell divides and re-divides until it forms an aggre-
gate of numerous small cells, the 'blastula.' This aggre-
gate, continuing to subdivide, then takes on a thimole-
7

8 ZOOLOGY

like form, the 'gastrula,' one layer of cells lining the cav-
ity, the other being external. This cavity is primarily to
contain and digest food, and the cells lining it naturally
take on the functions of nutrition, while the outer cells,
in contact with the outside world, take on the functions
of sensation, of offense and defense, and procuring food.
The living sponges and hydroids illustrate this stage of
development, more or less modified.

The next important stage in development is the forma-
tion of a third intermediate layer of cells between the
inner layer or endoderm and the outer layer or ectoderm.
From this intermediate layer are developed in the higher
animals the muscles, circulatory system and various glands
and organs, the alimentary system with its glands being
developed from the endoderm, the skin, the nervous sys-
tem and the organs of sensation from the ectoderm.
From this point onward, fundamental differences are to
be found in the plan of organization of the principal types
of animals, and the organs, adapted to serve the same
purposes, are often developed from different parts and in
a different manner. It is upon these fundamental differ-
ences in organization that the classification of the animal
kingdom is based.

These lower animals are derived from the same stock
as the higher ones. They persist to-day because they are
perfectly adapted to their habitat and mode of life, or
because they had gotten into a groove of evolutionary
progress which did not allow them to advance so fast or
so far as the higher types, or because of arrested develop-
ment from obscure causes. Some of the factors which
have limited their evolution are clearly seen, others are
and perhaps always will be difficult to trace.

Life originated in the ocean, or at all events in water;
but the dry land environment has stimulated a higher evo-
lution, the obvious cause being the more abundant supply
of oxygen, admitting of more active life. In order to
preserve the form and relations of their parts, all animals

DEVELOPMENT AND DISTRIBUTION 9

of any considerable size have been compelled to develop
a rigid framework or skeleton of some kind; the material
and position of this skeleton, and its further use for pur-
poses of offense and defense, have profoundly influenced
the further development of the race. In the lower ani-
mals the skeleton is generally external; and the insects
may be considered as representing the highest possibil-
ities of a development based upon an external skeleton.
In the vertebrates the skeleton at first was mainly external,
but this became gradually replaced by an internal struc-
ture; and the higher possibilities of development with the
internal skeleton form one leading cause for the higher
development and greater size attained by vertebrated
animals.

The third and perhaps the most important factor in
causing or arresting evolution is in the nature of the en-
vironment, whether constant from age to age, or subject
to slow secular or periodic change during geological time.
If an animal is fitted to its mode of life and the condi-
tions of its immediate surroundings remain unchanged,
the organism has no occasion to vary, and tends to become
fixed and unprogressive. But if the conditions are slowly
changing, the race must become adapted to fit its new
environment, and will retain or acquire a variability
which through the influence of selection will lead to
greater progressiveness.

The uniform and unchanging conditions of the deep sea
have not been favorable to progress; the theater of evolu-
tion of marine organisms has been the ever-changing lit-
toral region, the shores of the ocean, advancing and re-
treating through successive geological periods, widely
varied in character, ranging from rocky coasts to sandy
shoals, or from muddy flats to the still, clear water of
protected inlets. Some of the deep-sea organisms, such
as protozoans and sponges, have remained unchanged, so
far as is known, from the earliest geological periods
down to the present day. Others, like the crinoids, or

io ZOOLOGY

sea-lilies, long since extinct in the littoral region, have
found in the ocean depths a refuge where they still sur-
vive. Others again, like the deep-sea fishes, originally-
adapted to the life of the shore, have become curiously
modified to suit the conditions of the ocean's depths.

Easily evident, likewise, is a corresponding difference
between fresh-water and land animals. There can be no
doubt that all terrestrial life was ultimately derived from
an aquatic ancestry; those animals which have solved
the problem of the utilization of the more abundant oxy-
gen supply of the air instead of the limited amount avail-
able in the water having been able to assume a higher de-
velopment and greater progressiveness, and the snails
among mollusks, the insects among arthropods, and the
reptiles, birds and mammals among vertebrates are the
highest types in their respective classes. The fresh-water
animals, more limited in possibilities of development, and
subject to less change and variation in their conditions of
life, are of inferior type, and as in the deep sea, among
them may be noted survivals of very ancient and primitive
organisms and higher types developed upon the land, but
readapted to aquatic life. Having once acquired the
capacity to use the oxygen of the air, however, they are
careful not to lose it again, and remain air-breathers,
however far their adaptation to aquatic or marine life
may be carried in other respects.

It will have been noted that reference has been made
to the ancient forms of life, thousands of varieties of
which passed out of existence long before the existence
of Man, and it is natural to ask by what means their na-
ture is learned. To reply "By fossils" without determin-
ing what a fossil is would be to beg the question. The
term fossil, which originally meant merely things dug out
of the ground, has come to have a much more definite and
restricted meaning in the language of modern science.
Fossils are the remains of animals or plants or indications.

DEVELOPMENT AND DISTRIBUTION n

of their former existence, found buried in the soil or
enclosed in the rock.

In general, only the hard parts of animals are preserved,
the shells of mollusks and crustaceans and the bones of
the vertebrate animals, while the fact that they are pre-
served at all is due to a combination of favorable circum-
stances. Usually when an animal dies, the flesh or soft
parts decay or are devoured; the hard parts last longer,
but gradually disintegrate into formless dust or mud
under the influence of the atmosphere or the air-bearing
waters of the surface. But if the animal is buried in a
swamp, a river bottom, lake or estuary, where sediment is
being piled up by the action of the rivers or of the sea, its
hard parts may be covered up in time to escape destruction
and get below the zone of atmospheric influence. In this
case the remains will be subject only to the influence of the
mineralized waters that permeate the soil and rocks be-
neath the surface.

The action of these waters is to dissolve particle by
particle the organic matter of the fossil, and to replace it
with mineral matter. In this process, known as petri-
faction, usually the structure is preserved, as well as the
external form. The bone or shell is thus converted wholly
into stone, solid and permanent like the sediment in which
it was buried, now converted by the same agencies into
rock. This is the ordinary process by which fossils are
made. There is nothing mysterious about it — it is merely
the natural result that water seeping upward toward
the surface, loaded with mineral matter and destitute of
organic matter, tends to dissolve any organic matter it
finds on its way and deposit mineral matter in all the
minute cavities left, until they are filled and the porous
mud or sand becomes solid impermeable rock.

Fossils, then, preserved in this manner, constitute the
record of the history of life on the earth. It is an in-
complete record. Long periods of time are unrepresented,
because the sediments then deposited have been washed

12 ZOOLOGY

away or deeply buried, or the fossils in them destroyed by
crystallization. A large proportion of the past life of this
planet is imperfectly recorded or altogether lost because
the animals had no hard parts to be preserved. The vast
majority of the records are undiscovered or inaccessible
because they are still buried far beneath the surface,
and, moreover, the interpretation of the records is often
doubtful.

Yet the importance of paleontology, or the study of
fossil remains, is great, and its teaching positive because
the evidence is direct. No one to-day would venture to
question that the fossils of the rocks are the actual re-
mains of animals which lived and died in former ages;
and the scientist's knowledge of existing animals and
plants is now complete enough for him to be able to de-
clare positively that the animals which formerly inhabited
the world were different from those of to-day, and that
in proportion as research is pushed backward in time, the
earlier forms were more and more diverse from their
modern successors. Furthermore, it is seen that the low-
est and simplest groups of animals were of the earliest
introduction to the past life of the world, and that the
higher groups have successively appeared in order of
their complication and specialization in physical and men-
tal structure.

Throughout the geological record there is evidence of
'annectant' or intermediate types, linking together groups
of animals now widely separated; and the earliest ap-
pearing members of each group are more or less 'gener-
alized,' that is to say, their bodily structure conforms to
the general type of the whole group, but shows a combi-
nation of characters which are now found scattered among
the various modern members of the group, but seldom or
never all combined in one animal. These generalized char-
acters also are apt to be annectant, and link the group to
other groups.

For example, the birds and reptiles are now wide aparr,

DEVELOPMENT AND DISTRIBUTION 13

the birds being toothless, feathered, adapted to flight,
walking or hopping when on the ground, and with the
tail (exclusive of feathers) reduced to a little rudimen-
tary stub, while the reptiles possess teeth and scales, and
are crawling or swimming, with long vertebrated tails.
But all the earliest birds had true teeth like reptiles, and
the oldest of them, the Archseopteryx, a long verte-
brated tail feathered on the sides like the head of an ar-
row. And on the reptilian side are found the Dinosaurs
among the more ancient reptiles resembling birds in many
details of their bony structure, and especially in their
long legs, adapted to walking instead of crawling; and the
Pterodactyls, a group of flying reptiles, the latest of them
tailless and toothless, with horny beaks like the birds.

Again, there is a great gap among modern animals be-
tween fishes and four-footed animals of the land. But
the most ancient fishes are precisely those which come
nearest in structure to the higher vertebrates, and from
which these might most readily have been derived.
Through all the invertebrate groups the same conditions
appear.

Thus in a broad way the discoveries of paleontology
tend continually to break down the sharp lines of distinc-
tion between the great modern groups and classes of ani-
mals, and do so in just such a way as must follow if the
doctrine of evolution be true.

If the various species, genera, orders and classes of
animals are derived from a common ancestry through the
evolutionary process it should be possible to trace the
successive steps in the evolution and differentiation of
each race by the fossil remains of its ancestral stages in
the successive geological epochs. This has been done,
precisely and in detail, in many instances ; that it has
not been done in all, is due to the imperfection of the
geological record, to a peccable knowledge of it, and espe-
cially to the vastness of the problem and the limitations,
in means, facilities or insight, of those who are laboring

14 ZOOLOGY

to solve it. Broadly and approximately, the course of the
evolution of animal life has been traced out- from the
indirect evidence of structure and individual development,
and the more direct but less complete evidence of paleon-
tology. The task of working out and proving it in detail
is as yet far from complete. But among the thousands
of workers who are devoting their lives to the study of
fossils and their meaning, not one has been led to deny
the truth of evolution or to doubt the theory of descent.
Difference of opinion among scientific men is as to the
method, not as to the fact.

Closely allied to the nature of the animals of the past
is the question of their habitat in early times, involving
the problem evoked by their present geographical distri-
bution.

There are very few species of animals which inhabit
more than a portion of the world; most of them are lim-
ited to quite a small part of the land or water areas. Man
is perhaps the most cosmopolitan of all land animals. He
inhabits every considerable land area of the globe, ex-
cept the antarctic continent and a much smaller area
around the North Pole. Most animals, however, are
limited in their distribution by uncongenial climate or by
barriers which the species has not found means of cross-
ing. With land animals these barriers may be broad
stretches of ocean, extensive deserts, high mountain
ranges, or great rivers. With sea animals they may be
continental barriers, uncongenial stretches of coast, and
sometimes the volumes of fresh water poured out by great
rivers. But the limitations imposed by climate and tem-
perature are the most efficient barriers to the worldwide
distribution of either land or sea animals.

Animals are dependent directly or indirectly upon plants
for their food, and the abundance and rapid growth of
vegetation in the tropics affords opportunity for a cor-
responding development of animal life. The profusion
and variety of life in the tropics cannot fail to impress

DEVELOPMENT AND DISTRIBUTION 15

an observer from the temperate zone. The struggle for
existence everywhere going on is perhaps somewhat dif-
ferent in character. It is an internecine war, a strife for
survival among the animals themselves rather than a
combat against an unpropitious climatic environment. In
the temperate and especially in the arctic regions the ele-
ment of struggle against the untoward conditions of out-
side nature is superadded to the ever-present war against
other animals, which, scattered over a wider space, is less
apt to impress the observer, altho its influence on the de-
velopment of the race may* be no less powerful. Here,
perhaps, in the double struggle — against animals and
against nature itself — lies the reason for the dominance
of temperate and northern types when brought into com-
petition with the more abundant but less severely se-
lected races of the tropics. This fact is familiar in the
case of man, but it is equally true among animals. The
tropic regions, with their abundant food and easy life,
are the refuge of inferior races, succumbing and driven
forth before the sterner competition of the north.

The zoological realms and provinces of the world cor-
respond broadly with the geographic divisions, and even
to some extent with the political divisions, since geo-
graphic and climatic barriers have conditioned the dis-
tribution of the races of men and thus largely influenced
their governments. In the land fauna it is observed that
the great land mass of the northern continents forms one
great zoological realm, the Holarctic ; South America a
second, the Neotropical; Africa south of the Sahara a
third, the Ethiopian; and Australia a fourth, the most
isolated of all. The various islands partake more or less
of the character of the mainland adjoining, but there are
marked differences which point to a different distribu-
tion of land and water in former times than now.

Thus the animals of the British Islands are almost iden-
tical with those of Continental Europe, while the animals
of Madagascar are widely different from those of Africa.

16 ZOOLOGY

The simplest explanation, obviously, is that the former
have been connected with the mainland of Europe since
the present species of animals came into existence, the
latter has been separated from the mainland since remote
ages. Geological considerations support this view.

The marine provinces correspond in part with the great
oceans, but are more influenced by zones of temperature
than those of the land. So far as shore animals are con-
cerned, their lines of distribution will be along the coast
lines, and a broad area of deep sea is as much a barrier
to most of them as is a land barrier. Like the land ani-
mals, however, they give convincing evidence of former
differences in the distribution of land and water. There
is a considerable proportion, for instance, of identical
species on the two sides of the Isthmus of Panama not
found on the Asiatic or European coasts. Hence there
must have been communication between Atlantic and
Pacific oceans, either at the Isthmus of Panama or else-
where, since these species came into existence. They
could not have gone around the Horn, because they are
tropical species and are not found on the shores of tem-
perate South America.

The geographic distribution of animals, present and
past, together with the geological record of the evolution
of each race, furnishes a most important line of evidence
on the past history and geography of the globe, and under
the name 'paleogeography' a branch of study is being
built up which is of great scientific importance as well as
of transcendent interest. Its scope and vastness of pur-
view are readily recognised when it is remembered that
an intimate knowledge of Zoology and of Geology (each
of them vast and comprehensive) is a prerequisite. Es-
pecially is this true of the lower orders of life, which, de-
spite their simplicity, afford the most fascinating realms
of investigation.

A Horny Sponge, from the American Coast. (A. M. N. H.)

CHAPTER III

THE LOWER INVERTEBRATES

From the earliest times, when Sponges were believed
to be but solidifications of the foam of the sea, they have
been an element of curiosity to Man. They have been
declared to be animal, to be vegetable and to be mineral;
ancient naturalists quarreled over the question whether
they could move or no, and Aristotle's decision that they
were animal because they shrank when moved from their
rock bases provoked a storm of dissent. Even so keen
an observer as Lamarck believed the apertures on the
surface of a sponge to be the mouths of small cells in-
habited by polyps, and he expended no little wonder over
the question why a polyp never was to be found in his
cell. Peysonnel, on the other hand, declared that sponges
were created by a giant sea-worm, and held that the
sponge itself was "mere nidus and excretion."

It is now known, however, that the ordinary sponge of
bathtub importance is the horny skeleton of one of the
simplest kinds of animals. In life this horny framework
is lined with an inner and an outer layer or cells. It is
fast to a rock or coral block; its movements consist only
in inducing a current of water through the pores by
means of tiny whip-lashes attached to the inner cells, and
by a certain amount of contraction and expansion of the
entrances to the pores. The cells absorb and digest any
food matter that is brought by the currents of water pass-
ing through the pores. Most of the growth is by bud-
17

18 ZOOLOGY

ding; bisexual reproduction does occur, however, alter-
nately with the giving off of gemmules, or independent
buds; these gemmules, produced in the autumn, develop
into male and female forms, and the ova from the one,
fertilized by spermatozoa from the other, give rise to a
summer generation of sponges, which in turn produce
gemmules. This alternation of generations is not un-
common among lower animals.

There is a great variety of sponges, some with a cal-
careous skeleton, others with horny or siliceous skeletons.
They are nearly all marine, and the best known kinds are
tropical. The commercial sponges, of which the best
come from the Mediterranean and Indian seas, are found
in clear water at moderate depths. The fishermen locate
them by looking through a glass-bottomed bucket, and
pull them up with a pair of hooks on the end of a long
pole. They are left upon the shore to die and decompose
and then washed and bleached. Among the siliceous
sponges some, like the Venus' Flower Basket, are ex-
quisitely beautiful in the form and structure of the skele-
ton. These live at great depths and are obtained by
dredging.

Fossil sponges are found in the most ancient rocks.
Professor Cayeux has discovered the spicules of siliceous
sponges in the Archaean rocks of Brittany, which would
make them the oldest fossils known; and they are com-
mon in the oldest fossiliferous formations of other parts
of the world. So that the testimony of the rocks appears
to confirm what would be expected, that the sponges are
the most ancient, as they are the simplest of the Metazoa,
or many-celled organisms.

The Corals and Sea-anemones, Hydroids and Jelly-
fish, grouped under an order 'Ccelenterata,' are but little
less simple in form. In all these animals the structure
consists simply of a body cavity with a fringe of tentacles
around the edge. The tentacles are stinging and sensitive
cells which serve to capture the food; the body cavity is

THE LOWER INVERTEBRATES

19

lined with digestive cells which serve to digest it, and is
sometimes partially divided up by partitions extending
inward from the outer wall; and the outer layer of cells
may secrete a calcareous shell which serves as a protec-
tion. The jelly-fish are free-swimming organisms; the
hydroids and sea-anemones are fixed to the bottom; and

Fig. 2, — Speckled Jellyfish. (Drawn from a photograph.)

the corals are great colonies of individuals which secrete
a calcareous shell.

The translucent milky umbrella-like disk of the jelly-
fish, lazily opening and closing as it floats along the tide,
is familiar to every one. Beneath the disk hangs a circle
of long tentacles, stinging cells which serve to kill or
paralyze small fishes or other minute animals that may

20 ZOOLOGY

come in contact with them, and are floated into the body
cavity by a current of water produced by the lashing of
cilia, or whip-cells, in the same way as in sponges. Many
jelly-fish can inflict a sting sufficient to cause severe pain
to the incautious hand which touches them. The struc-
ture of the stinging tentacles is very curious. A. G.
Mayer, in his 'Sea-shore Life/ describes them as follows:
"The long flexible tentacles arise from the side of the bell
near the rim. The tentacles are covered with wart-like
clusters of minute thread-cells, each containing a coiled
tube which can be turned inside out as we might do with
the finger of a glove. If the tentacles come in contact with
a small fish or crustacean these little stinging threads are
instantly discharged, and on account of their minute size
they penetrate the skin of the prey, carrying with them
a poison, believed to be formic acid, which quickly para-
lyzes the victim."

The jelly-fish produces eggs, which, however, do not
develop directly into free-swimming jelly-fish, but into
fixed hydroids, and these in turn bud off jelly-fish. This
is another example of alternate generations. Hydroids
differ from jelly-fish in being fixed to the bottom; they
are like little vases, the lip lined with stinging tentacles,
and many of them develop by budding into compound
colonies. Many of the jelly-fish are strongly phosphor-
escent at night, and swarms of them floating in the water
make a very brilliant display when stirred up by a boat
passing through or by the breaking of waves upon the
shore.

It may seem strange that such an animal as the jelly-
fish should leave any traces of its presence in the rocks.
Nevertheless, under certain favorable circumstances they
may be buried in the sand and converted into siliceous
casts without much loss of shape, and these fossil casts,
known as 'star-cobbles,' are found in the most ancient
rocks of the Cambrian period in Alabama and else-
where. So it appears that jelly-fish were among the in-

THE LOWER INVERTEBRATES 2r

habitants of the seas at the dawn of recorded geological
history.

"A sea-anemone," says Mayer, "is a barrel-shaped ani-
mal. The bottom of the barrel is fastened to some rock
or other firm anchorage, while the upper end bears a slit-
like mouth which is encircled by a fringe of tentacles.
The mouth leads into a simple tube-like throat, which.

Fig. 3 — White-armed Anemone ; Expanded and Contracted.
(Drawn from a photograph.)

is bound to the inner sides of the barrel by means of
radiating partitions.

"The throat-tube is, however, only about one-half as
long as the height of the barrel, so that the radial par-
titions in the lower half of the barrel cavity do not meet

22 ZOOLOGY

at the center, but leave an open space which is the
'stomach' of the anemone. Sea-anemones are anions the
most attractive of marine animals, beautiful both in form
and color. They vary in size from that of a pin's head
to several feet across, and they live at all depths and in
a great variety of situations.

"A Coral Polyp is only a sea-anemone which deposits a
plate of lime salts at the base of its barrel-like body and
between the radial partitions of the stomach cavity. These
lime salts form a stony skeleton or substance which we
commonly call 'coral.' It is well to remember that the
coral animals are not 'insects,' but are merely sea-anem-
ones which form stony skeletons. Altho sea-anemones
and Coral Polyps resemble beautiful flowers when fully
expanded, they quickly contract into a mere dome-shaped
mass when disturbed. In this way the coral polyps are
protected by withdrawing into their stony cup-shaped
bases.

"The Coral Polyps are glassy white and translucent,
and have each from eighteen to twenty-four long taper-
ing tentacles which end in a white knob and are speckled
over with white warts. These are the stinging organs
which enable the coral to capture its prey of small marine
animals. When fully expanded the polyps are about one-
eighth of an inch wide and three-eighths high, but when
disturbed they suddenly contract so as to become prac-
tically invisible. The colony starts with a single polyp,
but soon others bud out from its base, and the cluster
increases by further budding from the bases of the older
polyps until it may be several inches in diameter.

"The Fleshy Coral is found from the eastern end of
Long Island to the Gulf of St. Lawrence. It is rarely
seen in shallow water, but is common upon rocks at
depths greater than twenty feet. When first brought up
from the bottom it appears as an ugly, tough gelatinous
mass covered with dull yellowish-pink finger-shaped
processes. If placed in water, however, the whole mass

THE LOWER INVERTEBRATES

23

soon appears studded with beautiful star-shaped polyps,
which expand so as to give the appearance of a stump
covered with delicate pink flowers. Each of these polyps
has a terminal mouth surrounded by eight tentacles, the
sides of which are bordered with rays giving a feathery
appearance. The whole colony of polyps develops
through constant budding from the sides and bases of the
older parts of the colony.

Fig. 4 — The Brown Anemone, the Common Species of the
North Atlantic Coasts. ( Redrawn from a photograph.)

"Nothing is more strangely beautiful than these coral
reefs where the rich purple sea fans and the chocolate
sea whips wave gracefully to the surges in the crystal
depths, while brilliant fishes glistening in green, blue,
purple and yellow glide in and out among the shadows
of the coral caverns. The precious coral of the Mediter-
ranean is allied to the Sea Whips. Its polyps are brilliant
white, and have each eight feathered tentacles; while the
internal axis of the colony is red and stony."

24 ZOOLOGY

The Stony Corals, especially the reef-building kinds,
have played an important part in the building up of the
continents. They flourish in a warm temperature and
clear water. In the West Indies, the Red Sea and Indian
Ocean, the northeast coast of Australia, and especially in
the islands of the Pacific, coral reefs to-day are building
out the land on a gigantic scale; and their influence has
been even more important at times in the past history of
the earth. The lower part of the peninsula of Florida
consists of a succession of reefs built out one after an-
other, the latest being the Florida Keys. The outer border
of the reef is alive and growing, the fragments broken off
by the waves from above filling up the interstices between
the growing corals and slowly extending the bank sea-
ward.

The lime extracted by the little coral polyps from the
sea-water and built up into solid limestone reefs would
in the course of time exhaust the entire supply of lime
salts in the ocean, were it not continually recruited by the
lime dissolved from limestones on land by the rain or
liberated in the decay of other rocks. This lime is brought
down by the rivers in the form of a soluble bicarbonate,
and in extracting it from the sea-water the corals and
other lime-secreting organisms set free a certain amount
of carbonic acid gas, which again is not without effect
upon the climate.

"Starfish, Sea-urchins, Sea-lilies and Sea Cucumbers,
forming the order Echinodermata," says Mayer, "are also
called 'radiates' because in the form of their bodies and
arrangement of their organs they usually display five rays.
For example, most starfishes have five equally developed
arms, J2° apart, recalling the rays of a conventional star.
In the Echinoderms the skin usually contains a skeleton
composed of calcareous plates of definite shapes, all
hinged together in an orderly manner, so as to make a
veritable armor which gives rigidity to the body and
protects the soft organs of the interior. In the living

THE LOWER INVERTEBRATES 25

starfish one will see hundreds of little tubular feet which
arise from the grooves on the lower side of the arms.
When the starfish is turned over upon its back these feet
stretch out to a remarkable length and wave about, seek-
ing to fasten upon something in order to right the animal.
It is then we may see that each of these feet is a hollow
tube ending in a cup-shaped sucker.

"Similar tube-feet will be seen in five double lines along
the sides of the sea urchins. The mouth of the star-
fish is at the center of the lower surface. On the upper
side, and a little away from the center between two arms,
one will see a spongy-looking area. This is called the
madreporic plate, and is the sieve-like entrance to the
water-tubes of the starfish, which extend down the arms
and give rise to little bladder-like vessels one above each
tube-foot. The contractions of these little bladders cause
the tube-feet to elongate by pressing water out into their
cavities. The upper surfaces of most of the starfishes are
covered with spines, but these are much better developed
in the sea urchins, where, in addition to spines, are found
calcareous pincers mounted upon rods, which are used to
remove any injurious foreign substance that may fall
upon the body of the urchins.

"The sea cucumbers, or Holothuria, are worm-like in
appearance, but are nevertheless closely related to star-
fishes and sea urchins. They have no spines and their
skeleton is often reduced to minute anchor-shaped spicules
within the skin. The mouth is at one end of the worm-
shaped body, and is surrounded by feathered or branching
tentacles. In some species there are five double rows of
tube-feet down the sides of the body, but in others these
are absent. When disturbed sea cucumbers have the
curious habit of casting out their viscera and afterward
regenerating them. They are sluggish creatures, and
either live within the sand or under rocks or crawl slowly
over the bottom, feeding upon minute organisms that are
contained in the sand or mud which they swallow.

26 ZOOLOGY

"Sea urchins, or Echini, may be compared to starfishes
without arms. They are usually provided with a skeleton
made for the most part of six-sided plates fused or rigidly
joined together. They have five sharp-edged teeth with
which they gnaw off minute seaweeds from the rocks.
Some species can even gnaw away the rock itself, and
in many parts of the world the sea urchins have literally
honeycombed the rocks; indeed, a sea urchin is often

Fig. s — Basket Star (left) and Sea-urchin (right). (Drawn
from photographs.)

found living in a cavity whose opening is too small to
allow of the animal's escape. The common sea urchin
of Europe is sold in the markets during the season when
it is full of eggs.

"The Sea Lilies, or Crinoidea, may be compared to a
starfish mounted upon a long stem which arises from the
middle of its back and anchors it to the bottom of the sea.
The mouth is turned upward, and is surrounded by
branching arms which sweep gracefully to and fro in
search of prey.

"The Echinoderms live only in salt water, but they are
found at all depths and in all oceans, from the tropics to
the poles. The vast majority crawl over the bottom, but
at least one holothurian swims through the water, and
was at first mistaken for a jelly-fish. Most of them cast

THE LOWER INVERTEBRATES 27

their eggs out into the water, and the larvae develop bands
of waving cilia, which enable them to swim about for a
considerable time. Suddenly the body of the Echino-
derm begins to develop with the larva, and most of the
old larval body is absorbed or cast off.

"Starfishes feed upon almost any kind of mollusk, but
will also devour barnacles, worms, and occasionally sea
urchins or even the young of their own species. It is
estimated that in one year starfishes destroyed $631,500
worth of oysters on the beds of Connecticut alone. In
the mode of feeding the stariish folds its arms over the
clam or oyster, and hundreds of the sucker-like tube-feet
fasten themselves to the valves of the shell, so that finally
the mollusk yields to the constant pull of the starfish and
the shell gapes open. Then the starfish turns its stomach
inside out and engulfs the mollusk. It has been found by
experiment that a large starfish can exert a steady pull
of over two and one-half pounds, and that this is suffi-
cient in time to open the valves of a clam or mussel.

'The eggs of the starfish are discharged into the water
in greatest abundance during the last three weeks of
June, altho they are also to be found throughout the sum-
mer, and occasionally even in winter. These eggs soon
develop into little transparent larvae covered with tor-
tuous lines of waving cilia, and provided with long, flex-
ible tubercles. They swim slowly about near the sur-
face, and feed upon minute organisms until they grow
to be about one-eighth of an inch long. Then the upper
and lower halves of the star begin to develop upon both
sides of the stomach, and in a few hours all of the an-
terior part of the larva and the tubercles are absorbed,
and only a minute star about as large as a pin's head is
seen upon the bottom of the ocean.

"Myriads of these little stars settle upon sea weeds and
eel grass, and begin at once to devour the young clams
which also begin life in the same places. Professor Mead
found that one of these little stars devoured over 50 young

28 ZOOLOGY

clams in 6 days. The starfishes grow rapidly, and in one
year they may have arms 2^4 inches long and be ready
to spawn."

Besides the common five-pointed starfish there are
many others more or less familiar. The Serpent-stars
have long, slender, flexible arms and are much more
active; in the Basket-stars the arms are branched and
forked into a multitude of slender interlaced tips upon
which the animal moves about with the body lifted above
the ground.

The prickly sea urchins abound along rocky coasts;
along the sandy shores they are replaced by the sand-
dollar, flattened out into a thin plate covered with minute
brown spines. Sea cucumbers are familiar to every one
who has explored the tide-pools of rocky coasts at low
water, but other kinds are common on sandy, muddy or
gravelly beaches, living just below low-water mark. In
China a species of sea cucumber is prepared and eaten as
a delicacy. Sea lilies, or Crinoids, are now rare and con-
fined to deep water, but in the early periods of geologic
time they were very abundant and varied, shore forms
as well as deep-water species. The oldest of them, dating
back to the Cambrian Period, suggest a sea urchin which
has lost its spines and is mounted upon a jointed stalk; in
the Crinoids proper the body has developed branching arms
which wave in a feathery plume above it. The fossil
crinoids, or 'stone-lilies/ are sometimes preserved in won-
derful perfection in the Paleozoic limestones, and are
one of the most attractive of fossils. Great numbers of
them have been obtained in the limestones of Crawfords-
ville, Indiana, and elsewhere in the United States.

"The title 'Worms,' " says Professor Thomson, "is
hardly justifiable except as a convenient name for a shape.
The animals to which the name is applied form a hetero-
geneous mob, including about a dozen classes whose rela-
tionships are imperfectly known. But the zoological in-

THE LOWER INVERTEBRATES 29

terest of the diverse types of worms is great. For amid
the diversity we discern affinities with Coelenterata, Echi-
noderms, Arthropods, Mollusks and Vertebrates.

"Moreover, it is likely that certain worms were the
first to abandon the more primitive radial symmetry, to
begin moving with one part of the body always in front,
to acquire head and sides. And if one end of the body
constantly experienced the first impressions of external
objects, it seems plausible that sensitive and nervous
cells would be most developed in that much-stimulated,
over-educated head region. But a brain arises from the
insinking of ectodermic (skin) cells, and its beginning
in the cerebral ganglion of the simplest 'worms' is thus in
part explained."

Most of the creatures which fall into this group are of
little interest to the general reader. Many of them are
parasitic ; some, like the Tape-worms, Thread-worms,
Flukes and Trichinae, are unpleasantly familiar in this
connection. The simpler Unsegmented Worms are those
which most nearly represent the remote ancestors of mol-
lusks and of vertebrates; the higher Segmented Worms,
or 'Annelids/ follow more definitely along the line of
crustacean and insect evolution. In them may be found
an arrangement of organs and plan of bodily construction
which serves to explain how the organization of the
crustaceans and insects has been developed.

The Common Earthworm is the most familiar of the
annelids, and its anatomy is much more interesting and
complicated than might at first be supposed. The sur-
prise is great that awaits the man who first dissects an
Earthworm. With proper cleaning and dissection he will
be able to see a complex and wonderful structure, a plan
of organization wholly different from that of the higher
animals (vertebrates), yet subserving to a large extent
the same purposes, and beautifully adapted to the needs
of the Earthworm's life and habitation. To tear up that
delicate mechanism on the prongs of a fishhook is likely

30

ZOOLOGY

afterward to appear to him a sort of disregard of propor-
tions, much like throwing a gold watch at a stray cat.
Of the anatomy a detailed account cannot be given here.

Fig. 6 — Nervous System in Various Phyla,
i., sea anemone; 2., starfish; 3., worm; 4., centipede; 5., clam;
6., honey-bee ; 7., salamander.

It must suffice to say that it has a straight alimentary^
canal stretching from the mouth at the front end to near
the hinder end of the body, the front end of the canal be-

THE LOWER INVERTEBRATES 31

ing provided with a muscular ring and with glands which
aid it in swallowing and digesting the earth which forms
its food. There is a circulatory system, consisting of a
slender tube along the mid line of the back and others
along the under side, joined by several cross veins encir-
cling the throat, which by expanding and contracting
enable the colorless blood to circulate through the body.
It possesses also a nervous system consisting of a cord
corresponding to the spinal cord of higher animals, but
situated on the under side of the body along the middle
line, and double instead of single, with little knot-like
expansions or ganglia at every segment, which corre-
spond to the brain of the higher animals, and with a
separate pair of ganglia on the dorsal (upper) side of
the head united with the front pair of ganglia of the
under side by a pair of cords encircling the gullet.
There are no eyes or other specialized sense organs, no
special organs of respiration; yet the worm is aware
of the approach of enemies or of light and darkness
through a general sensitiveness of the skin, and the blood
is aerated through the skin. There are, however, the
beginnings of organs of excretion, to remove waste mat-
ter from the circulation, and the reproductive system is
quite elaborate, the animal being hermaphrodite — that is,
combining both sexes in one individual, but so arranged
that the eggs of one Earthworm must be fertilized by
another.

The chief economic importance of Earthworms is
as principal agents in forming the mantle of humus, or
soil, which covers the dry land in all parts of the world,
and buries the hard rocks and sterile soil beneath it.
Earthworms abound in all parts of the world; they eat
their way through the soil and come out at night to the
surface, where they forage around for leaves and stray bits
of vegetable matter, which they drag to their burrows to
be nibbled and swallowed at leisure. Their castings, com-
posed of the earth and comminuted vegetable matter

32 ZOOLOGY

which they have swallowed and digested, are deposited
on the surface, and in the course of their lives they
bring up a good deal of the sterile under soil, mix it thor-
oly with particles of vegetation from the surface, and
deposit it in their castings. These, accumulating year
after year and century after century, form the layer of
humus, or top-soil, in which vegetation chiefly thrives and
on which the gardener and farmer depend for the suc-
cessful growth of their crops.

Not all the humus is due to Earthworms — insect larvae
play some part, and to a large extent it is merely due to
natural decay of surface vegetation and its mixture with
soil by rain and the dust brought by the winds. But the
investigations of Darwin showed that the Earthworm
plays an important part in its formation. Thus as the
tiny Coral Polyp is ever helping to form the continents
on which man can live, and perhaps also to control the
climate and moderate the extremes of temperature, so
also the Earthworm is rendering efficient aid in covering
the land with rich and fertile soil, enabling vegetation to
flourish and making the earth habitable for the human
species.

The name 'mollusks/ or soft-bodied animals, covers an
immense number and variety of invertebrates, the Clams,
Oysters and other shellfish, the Snails and Slugs, the
Octopus and Squid, and many less familiar types. All
of them have soft bodies, usually with an external cal-
careous shell, but with no internal skeleton except in the
Squids and their relatives. They are much more highly
organized than the Coral or Starfish groups. The ar-
rangement of the organs shows a bilateral symmetry, un-
like the radial symmetry of Coral or Starfish. That is to
say, the organs and parts of the body are arranged in
pairs on each side of the middle line, so that there is a
front and a hinder end to the body. On the other hand,
the body is not divided into successive segments as in the

THE LOWER INVERTEBRATES 33

worms, crustaceans and insects. Most of the mollusks
are sluggish animals, many of them attached to stones or
other objects on the bottom, but the Squid and Cuttlefish
are swift and active.

"The lower surface of the body," says Mayer, "consists
of a thick muscular 'foot' used in creeping. In front of
the foot is the head, which may have a pair of eyes and
tentacles; while the mouth lies on its lower surface and
is often provided with numerous horny, rasping teeth.
A flap-like fold of the body extends outward from the
sides. This fold is called the 'mantle/ and its free edge
and upper part secretes the shell which usually covers
the back of the mollusk. The feathery gills arise from
the sides and lie in the space between the lower side of the
mantle and the side of the body. The intestine is coiled
and opens typically at the posterior end of the body,
behind the foot. There is a paired digestive gland or
'liver' which pours its secretion into the mid-gut. The
three-chambered heart lies above the hind gut and pumps
blood from the gills to other parts of the body." In ad-
dition, it may be noted that the mollusks show well-de-
fined muscles and nervous system.

The latter consists of a number of ganglia, knots or
nodes of 'gray matter,' corresponding in function more
or less to the brain of higher animals, connected by cords
of nerve fibers which may be said to correspond roughly
to the spinal cord in higher animals. From these gan-
glia nerves are given off to the various parts of the
body. This concentration of the nervous system into a
few defined ganglia connected by cords is a great advance
upon the condition in the lower invertebrates, where the
nerve cells are diffused and scattered over the surface of
the body. It makes possible a much more exact and
definite correlation of the movements and actions of dif-
ferent parts of the body. It is like the establishment of
a central executive bureau to control and order the ac-
tivities of some great and complex organization.

34 ZOOLOGY

The great majority of mollusks are marine, chiefly
shore-living, altho some are adapted to a deep-sea life.
But many inhabit fresh-water lakes, rivers and streams,
and one group, the Land-snails, has become adapted for
terrestrial life, breathing air instead of water.

The principal groups of mollusks are: (i) The Bivalves,
or Lamellibranchs, comprising clams, oysters, mussels
and other shell-fish in which the shell consists of two
valves, right and left; (2) Snail-shells, or Gasteropods, in-
cluding snails, whelks, periwinkles, limpets and others
in which there is a single valve, mostly spirally coiled;
the symmetry of the animal is obscured in this group by
development of one side ; in the Slugs the shell has degen-
erated to a small, horny scale buried in the body; (3)
Squids and Cuttlefish, or Cephalopods, including also the
octopus, nautilus and a host of extinct forms; they are
free-swimming, active animals with a ring of muscular
tentacles around the mouth and part of the 'foot' modified
into a funnel, the 'siphon,' through which water can be
forcibly expelled from the mantle cavity, driving the ani-
mal backward; these are considered the highest develop-
ment of molluskan life, on account of their active habits
and more concentrated nervous system.

The Lamellibranchs feed upon minute organisms, both
animal and vegetable, which they sift out from the sea
water by the aid of gills. The gasteropods are more gen-
erally carnivorous, feeding upon other mollusks, which
they attack by boring a hole in the shell by means of a
ribbon-like tongue, the 'radula,' armed with many small,
sharp, horny, rasping teeth, and then sucking out the
juices of their victims. This unique little implement ap-
pears to be very efficient for its purpose, and is said to
be aided by a secretion of sulphuric acid. Other gastero-
pods, such as the periwinkles and the fresh-water and land
snails, feed upon plants, but all of them possess the radula.
The cephalopods also are carnivorous, the Octopus lying
in wait for unwary fish or crustaceans which may come

THE LOWER INVERTEBRATES 35

within reach of the long tentacles, the Squids captur-
ing their prey by darting rapidly backward, swinging
quickly to one side and seizing the victim in their sucker-
bearing arms.

The mollusca include an immense number and diversity
of animals. In the Gasteropoda alone there are over fif-
teen thousand living species ; the Lamellibranchs are hard-
ly less numerous. Many of them are edible, a few are im-
portant articles of food. The oyster fisheries in the
United States alone are estimated to yield $16,600,000 an-
nually. The soft-shell clam of the North Atlantic, the
scallop and the round clam or quahaug of the Middle At-
lantic States, are important articles of commerce, while
mussels, whelks, periwinkles and land snails also are
largely eaten in Europe. The pearl oysters of the Indian
and Pacific oceans and the fresh-water pearl-clams of the
United States are likewise of importance, not only for the
pearls, but for the much larger industry in mother-of-
pearl obtained from the shells and manufactured into but-
tons and pearl ornaments. The pearl fisheries in the Per-
sian Gulf alone are said to be worth $2,000,000 annually.

The noxious activities of mollusks are slight. A few
species commit depredations upon oyster-beds ; the damage
done by the teredos to timber under water is more serious.
The gruesome tales of attacks upon man by the devil-fish
or octopus are mostly fanciful. An octopus, if large
enough, no doubt could and would attack a man if he
came within reach. And once in a while he might catch
him at a sufficient disadvantage to overcome and destroy
him. But the chances for such an encounter with such a
result are exceedingly small. Members of this group of
mollusks do attain a gigantic size, however. These huge
forms are deep-water organisms, and are very rarely seen
by man, altho they form an important part of the food
of marine mammals such as the seals and sperm-whales.

During the whole of recorded geologic time mollusca
have been an important element in the marine fauna;

36 ZOOLOGY

iresh-water mollusks are probably equally ancient, and
land mollusks are known to have appeared as far back as
the Coal Era. Their hard, indestructible shells are the
most abundant of fossils, often making up the entire mass
of limestone strata. Lamellibranchs, gasteropods and ceph-
alopods were all distinct as early as the Cambrian Period ;
their evolution from a common stock must date far back
into the unrecorded beginnings of geologic time. The
shelled cephalopods, related to the modern nautilus, at-
tained great size and abundance early in geologic time,
and were then the dominant type of marine life. In
Orthoceras the shell is sometimes seven feet long, straight
instead of coiled as in the nautilus. During the Age of
Reptiles the cephalopods were again very abundant marine
forms, the Ammonites, Baculites, etc., coiled, partly coiled
or uncoiled, being probably more nearly related to the
squid and octopus than to the nautilus.

But the majority of fossil shells are related to the mod-
ern lamp-shells and their allies, the Brachiopoda, which,
altho mollusk-like, are not true mollusks, the plan of or-
ganization of the animal being wholly different. The
shell may be distinguished by the fact that its valves are
dorsal and ventral, instead of right and left, with respect
to the symmetry of the animal. These Brachiopoda are
considered a class apart, or grouped with Bryozoans into
the 'Molluscoidea/ Their relations are about as close
with worms as with mollusks, but not very near to either.
The living brachiopods are rare deep-water organisms,
crowded out from shallow water by competition of the
more highly organized mollusks; but in early geologic
times they were the common shells of the sea-shore.

With the Crustaceans begins the Arthropod series of in-
vertebrates, characterized by a segmented body, jointed
limbs and an outside skeleton. The name (arthro-poda,
jointed feet) points to the distinction that separates them
from the worms; but their plan of organization is evi-
dently derived from that of the segmented worms or An-

THE LOWER INVERTEBRATES 37

nelids. The crustaceans are adapted to aquatic life and
breathe by gills; the insects are adapted to terrestrial life
and breathe by tracheae; the spiders and their allies in-
clude both land and aquatic types, differing from either
insect or crustacean in their plan of organization.

The lobster and crayfish are the most typical crusta-
ceans, the first marine, the second living in fresh water.
In comparison with the worm, it is observable that while
the body is segmented, the segments are not all alike, but
are divided into two regions, the head-and-thorax and
the abdomen. Likewise tKe appendages are not mere
bristles as in the worms, but jointed, and specialized to
serve different purposes. The most anterior ones, an-
tennae and antennules, are organs of touch and smelly
enabling the lobster to feel his way about; next come six
pairs which serve chiefly to aid in biting and chewing the
food; then the large forceps to seize the prey; then four
pair which are used in walking; and six posterior pairs
used mainly for swimming purposes. Altogether there are
nineteen pairs of appendages. The stalked eyes are not
classed as appendages, being of different origin. The seg-
ments and appendages are enveloped in a tough, horny
covering, flexible at the joints, hardened elsewhere by lime
salts into a rigid armor.

The internal organs of the lobster are much more elab-
orate than in the wdrm, but their general plan is much the
same. The nervous system is more concentrated; the
muscles are distinct and well developed; the alimentary
system consists of, first, a gizzard with a complex mill
for grinding up the food, then a mid-gut stomach with
a large digestive gland which takes the place of liver, pan-
creas, and in part the stomach glands of higher animals;
and finally a long straight hind-gut, which takes but small
part in the digestive process. The colorless blood enters
the heart from the gills through valves which admit of
entrance but not of exit. Thence it is pumped through
well-defined arteries to the tissues of the body, from which

38 ZOOLOGY

it returns through ill-defined channels to the gills. The gills
are feathery structures of a rather complex nature, pre-
senting a large surface to the current of water which the
animal keeps going through them by paddling with part
of the fifth pair of appendages. There is also a distinct
excretory system (kidney), and the reproductive organs
•are more elaborated than in the worm, the sexes being
separate. It is thus a much higher type of animal than
the earthworm, but the plan of organization is the same,
as it is also in the insect. The mollusk and the vertebrate
are organized upon entirely different plans.

The lobster occasionally attains great size, and one
specimen, three feet and six inches long and 30 pounds
in weight, was captured off the New Jersey coast in
March, 1897.

The Snapping Prawns are little lobster-like crustaceans
of the American coast. The largest are not more than one
and three-quarters inches long. One claw is much larger
than the other, and is provided with a sharp-edged blade
which is normally held out at right angles to the claw. At
the least alarm this blade is closed with a sharp snap, re-
minding one of the explosion of a small torpedo. These
little creatures live in crevices of coral reefs, under shells
and stones and fairly swarm in sponges; so that when a
sponge is lifted from the water it crackles as if filled with
minute firecrackers. The Shrimps are similar in many
ways, but are free swimmers.

A Crab is essentially a lobster with its tail turned in
under its body. It is the highest of the Crustacea, and
the species is widely distributed and varied, extending
from the combative edible or blue crab to the parasitic
hermit crab; ranging in size from the tiny oyster crabs
which live with the gill cavity of the oyster to* the giant
spider crab of Japan, which attains a span of twelve feet;
including deep sea crabs which never come to the surface
and the land crabs of the tropics which rarely enter the

THE LOWER INVERTEBRATES 39

water, and which, like the robber crabs, climb trees and
live on cocoanuts.

Barnacles, while mollusk-like in appearance, are really
crustaceans which have affixed themselves to rocks or
floating objects and are enclosed in a hinged calcareous
shell. As Huxley put it, "They are fast to a rock by
their heads and kick the food into their mouths." The
stalked barnacle, or 'goose-barnacle,' was believed by
writers of the Middle Ages to undergo a metamorphosis
into a species of goose — the 'barnacle-goose' — and this
transformation was repeatedly asserted in the most posi-
tive terms down to the time of Linnaeus or even later.

"Being encased in a natural armor," says Mayer m
'Seashore Life,' "crustaceans cannot grow at a uniform
rate, but enlarge suddenly at the periods when the shell is
shed. This occurs at fairly regular intervals, and the
entire shell is shed, even the coverings of the eyes and
part of the lining of the stomach being cast off. The
creature is then soft and helpless, and usually remains
hidden in some safe retreat until the body has expanded
and the new shell hardened."

Owing to their hard outer armor and their aquatic life,
remains of crustaceans are very common as fossils, and
there is a fairly complete record of their evolution. The
higher types, such as crabs and lobsters, did not appear
until after the Coal Period. But the more primitive,
mostly minute crustaceans known as Ostracods and Phyl-
lopods have been traced as far back as the Cambrian,
nearly to the beginning of recorded geological history.

The Trilobites, familiar to every geologist, were a
primitive group of crustaceans which flourished during the
older geologic periods, becoming extinct in the Coal
Period. They are very abundant and characteristic fossils
in Paleozoic strata. Many of them attained considerable
size, the largest up to two feet in length.

CHAPTER IV

THE HIGHER INVERTEBRATES

It seems natural to think of a spider or scorpion as an
insect. But in fact they are not true insects, altho they
belong to the Arthropod series of invertebrates. All in-
sects have three pairs of legs and breathe by tracheae.,
Spiders and scorpions have four pairs of legs and breathe
by "lung-books," an apparatus like modified gills. And in
all the details of their anatomy spiders and scorpions)
are as different from insects as they are from crustaceans.
All insects (excepting, perhaps, a few unimportant primi-
tive kinds) have wings or have had them at a formers
period in the development of the race; altho in many
groups the wings are degenerate or lost. Scorpions and
spiders appear never to have developed wings at all.

In short, the insect class may be regarded as an adap-
tation of the Arthropod invertebrates to aerial life; the
spider class to terrestrial life; the crustaceans to marine
life. Each, in its own element, has had a long and more
or less successful career; each has made attempts to in-
vade the territory of the others. For in the West Indies
and other oceanic islands are crabs which pass their life
mostly on dry land; and the spider swinging in air from
a slender thread, and even in some cases traveling
through the air on a long film of unattached gossamer, is
emulating the habits of the flying insect. But the insects
alone have invaded the alien habitats with any great suc-
cess, and so far as terrestrial life is concerned they have
crowded the spiders and scorpions to the wall.
40

THE HIGHER INVERTEBRATES

4i

Scorpions are found only in tropical countries, and are
distinguished by the elongate tail with venomous tip and
the large-clawed grasping legs in front. They have four
pairs of walking legs like spiders. In the old natural his-
tory books they are credited with committing suicide when
unable to escape by stinging themselves to death Unfor-
tunately for the story, aside from the argument that the
mental processes of the lower animals are not very likely

-A Scorpion.

to lead them to deliberate suicide, the feat is anatomically
impossible, and if it were possible the poison would have
no effect.

Spiders are common everywhere, and, like scorpions,
they are all carnivorous, sucking the juices of insects
which they capture. Many of them, but not all, form
webs, and the construction of the web is a remarkable*

42 ZOOLOGY

piece of engineering, which must involve highly elaborated
instincts comparable only to those of the higher insects.

The material of the web is a liquid silk secreted by the
spinning glands and forced through the fine tubes of the
"spinnerets," hardening immediately on exposure to the
air. The spun threads are used also to line the nest, to
envelop the cocoon, and to assist the spider in his aerial
gymnastics.

The Spiders are by no means confined to webs, but cer-
tain of them construct more permanent dwellings. Thus
the Mason Spiders dig a hole in the ground, and then spin
across and across the mouth of it a woven door with a
hinge at one side. Even less known and more curious is
the work of a little water-spider, who, not desiring to
forego the power of air breathing, spins a silken diving
bell, wherein is imprisoned a globule of air.

Male spiders are very much smaller than the females,
the difference in bulk being sometimes as 1,300 to 1, and
more brightly colored.

With spiders and scorpions are classed various parasitic
insects, such as mites and ticks, and other minute and
degenerate forms. The King Crab or Horseshoe Crab
has also been discovered to be more nearly related to the
Arachnoids than to the Crustaceans, which it resembles
in appearance and habitat. And another group of aquatic
animals, the Eurypterids, now extinct, is regarded as most
nearly related to the scorpions among living animals. The
Eurypterids inhabited brackish or fresh water during the
Paleozoic era, and some of them attained a length of six
or seven feet, a truly formidable size for that ancient
period.

The numbers and variety of insect life are far beyond
those of any other animals, at least upon the land. More
than half the described species of zoology are insects —
more than three-fourths of the land animals belong to
this class. And the innumerable hosts of some sorts
make them, despite their small size, the most dreaded and

THE HIGHER INVERTEBRATES 43

dangerous enemies with which man has to contend. The
seriously noxious insects are indeed a small minority — (
most are indifferent so far as man's welfare is concerned
— a few are actively beneficial. But as a class, it must be
affirmed that the harmful activities of insects outweigh!
their beneficial action. They are rivals with man for the
possession of the fruits of the earth, and if to the damage
on this score be added their activities as carriers of in-
fectious diseases, they may well be regarded as the most
formidable enemies of man in the animal kingdom.

The insect is an evolution from the primitive worm or
annelid type, adapted to terrestrial life as the crustacean
is to marine life, and the structure and plan of organiza-
tion is much the same in both. There are two most im-
portant differences. The first of these is that the crus-
tacean breathes by gills, the insect by tracheae, branching
tubes which ramify into every part of the body, and by
expanding and contracting take in fresh and expel viti-
ated air, as do our lungs. The second difference is that
the insect has wings, generally four of them. The ar-
rangement of the nervous system, the circulation, the ap-
pendages and mouth parts, the sense organs and the ali-
mentary system are much as in crustaceans.

In comparison with higher vertebrates of the land, the
insect shows a fundamentally different plan of organiza-
tion. Thus, in a vertebrate the principal nervous system is
along the dorsal, in an insect along the ventral side of the
animal. In a vertebrate the jaws open up and down, and
the teeth are originally modified scales; in an insect the
jaws open sideways and the teeth are modified legs. In
a vertebrate the skeleton is internal, in an insect it is ex-
ternal. The heart of a vertebrate is in its thorax, the
stomach in its abdomen; in an insect the position is re-
versed. The vertebrate pumps vitiated blood from the
tissues to the lungs to be aerated ; the insect pumps fresh
air to freshen the vitiated tissues directly. The wings of
a bird or a bat are modified legs ; the wings of an insect

44 ZOOLOGY

are outgrowths from the skin of the back. And so on
throughout. The resemblances between insects and land
vertebrates are mostly superficial ; their plan of organiza-
tion is wholly different, and the similarity is due to both
being adapted to live on land. The resemblances between
insects and crustaceans indicate relationship; their plan
of organization is fundamentally the same, the differences
being due to adaptation to terrestrial life in the one, to
aquatic life in the other.

Note that there are water insects and likewise land
crustaceans. But the land crustaceans still breathe by
gills, a method evidently adapted for water-breathing.
And the water insects are dependent upon air for breath-
ing, so that they have to come to the surface from time to
time at least.

The most important feature of the development of the
higher orders of insects is the metamorphosis or change
of form from larval to adult. The egg hatches into a
larva wholly different from the adult in form, internal or-
gans, and manner of life, and the larva in changing to
the adult form undergoes a metamorphosis which involves
the almost complete breaking down of all the structures of
the body into a mass of formless tissue, and the rebuilding
out of this formless tissue the organs and parts proper to
the adult.

This extraordinary change takes place in from two or
three days to several weeks, and the insect undergoing
it is called a pupa. In the lower orders of insects there is
no metamorphosis or a very incomplete one. The mean-
ing of this change and the object of it in furthering the
interests of the insect is not very clear. Obviously the
wingless crawling larva may be regarded as having once
represented the ancestral type from which the insect is
descended, but as now greatly altered to fit the require-
ments of its own (juvenile) habits and environment And
it is possible to explain- the breaking down of the old tis-
sues into a formless mass of cells by supposing that larva

THE HIGHER INVERTEBRATES 45

and adult have each proceeded so far on their divergent
specializations of structure and form in adaptation to the
needs of each, that it has become cheaper, so to speak, to
break down the old tissues and build anew, rather than to
modify the old into the new tissues along the lines of
natural development.

Setting aside certain primitive wingless insects, the
three orders Ephemerida, Plecoptera and Odonata (May-
flies, Stone-flies and Dragon-flies) are given lowest rank
among insects because of their incomplete metamorphosis.
All of them haunt the fresh-water ponds, rivers or streams
wherein their larvae dwell, and are not seen far away from
water. The larvae are at first wingless, provided with gills
instead of spiracles, so that they are not obliged to come
to the surface. They develop rudimentary wings during
their larval life, and change to the adult form by a suc-
cession of molts like crustaceans, without any breaking
tip of the internal structures.

The dragon-flies "are unexcelled among insects," says
Kellogg, "for swiftness, straightness and quick angular
changes in direction of flight. The successful mainte-
nance of their predatory life depends upon this finely devel-
oped flight function, together with certain structural and
functional body conditions which might be said to be
accessory or auxiliary to it. All have four well-developed
wings. The body is long, smooth and subcylindrical or
gently tapering. This clean, slender body offers little re-
sistance to the air in flight and serves as an effective steer-
ing oar. The wings are long and comparatively narrow,
fore and hind wings being much alike. . . . The head
is unusually large, and more than two-thirds composed
of the pair of great compound eyes. More than 30,000
facets have been counted in the cornea of certain dragon-
fly species. For accurate flight and successful pursuit of
flying prey, the dragon-fly has full need of good eyes. The
jaws are strong and toothed, and obviously well adapted
for tearing and crushing the captured prey.

46

ZOOLOGY

"When the prey is come up with, however, it is caught,
not by the mouth but by the 'leg-basket/ and then held in
the fore legs while being bitten and devoured. The in-
ternal anatomy is specially characterized, as might well
be imagined, by a finely developed system of thoracicr
muscles for the rapid and powerful motion of the wings
and the delicate and accurate movements of the legs. The
respiratory system is also unusually well developed.

"The prey of the dragon-fly may be almost any flying

Fig. 8 — Young of Giant Dragon-fly in Different Stages of
Development, Slightly Enlarged. (Needham.)

insect smaller than itself, altho midges, mosquitoes and
larger flies constitute the majority of the victims. The
good that is done by dragon-flies through their insatiable
appetite for mosquitoes is very great. Now that we recog-
nise in mosquitoes not only irritating tormentors and
destroyers of our peace of mind, but alarmingly dangerous
disseminators of serious diseases (malaria, yellow fever,
filariasis), any enemy of them must be called a friend of
ours."

THE HIGHER INVERTEBRATES

47

Dragon-flies are a very ancient race of insects. They
tenanted the strange antique forests of the Coal Period,
and some were, for an insect, of gigantic size, one having
a spread of wing of nearly two feet. Others are found in
the still older forests of the Devonian. And indeed it is
to the ancient life and ancient land that dragon-flies seem
peculiarly appropriate. The dark, somber tropical swamp-
forests of those early days, their trees gigantic club-

Fig. 9 — The Giant Dragon-fly. About Five-sevenths Natural
Size. (Kellogg.)

mosses, ferns and horse-tail rushes, before the appearance
of flowers, of broad-leaved trees, of land vertebrates, seem
peculiarly fit to be tenanted by insects which to-day are as-
sociated with similar life-conditions, and which have no
relations with flowering plants or with the higher develop-
ments of insect life.

The various kinds of bugs, scale-insects and plant-lice
which make up the order of the 'Hemiptera,' or Bugs,
have the mouth parts modified into a sucking beak. They

48 ZOOLOGY

feed upon the juices of living plants or the blood of living
animals, and include the worst of insect scourges. Owing
to their sucking habits, they are more difficult to combat
than the biting insects, and their fecundity is enormous.

"The order Hemiptera," says Kellogg, "includes over
5,000 known species of North American insects, repre-
senting a large variety and a great economic importance.
Some of the most destructive crop pests and most discom-
forting insect scourges of man and the domestic animals
belong to this order. The chinch-bug's ravages in the
corn and wheat fields of the Mississippi Valley offer ef-
fective evidence to the dismayed farmers of the workings
of a displeased Providence; the tiny sap-sucking aphids
and phylloxera and insignificant-looking scale-insects make
the orchardist and vine-grower similar believers in super-
natural moral correction by means of insect scourges;
and the piercing and sucking lice and 'bugs' — in the Eng-
lish meaning — make personal and domestic cleanliness a
virtue that brings its own immediate reward. . . . The
name Hemiptera is derived from the character of the fore-
wings shown by most, tho by no means all of the members
of the order ; this is the thickening of the basal half of the
otherwise thin membranous wing, so that each fore-wing
is made up of two about equal parts of obviously different
texture and appearance ; hence 'half-winged.' All Hemip-
tera (except the male scale-insects) have an incomplete
metamorphosis, the young at birth resembling the parents
in most essential characteristics except size and the pres-
ence of wings. By steady growth, with repeated molt-
ings and the gradual development of external wing pads,
the adult form is reached, without any of the marked
changes apparent in the insects of complete metamor-
phosis. With similar mouth parts the young have, in most
cases, similar feeding habits, preying upon the same kinds
of plants or animals that give nourishment to the parents.

"The extent of the injuries done by various members
of this order to farm and orchard crops, to meadows and

THE HIGHER INVERTEBRATES 49

forests, and to our domestic animals is enormous. Of the
other insects the order of beetles includes numerous crop
pests, and the caterpillars of many moths and a few but-
terflies do much damage; locusts have a healthy appetite
for green things, and many kinds of flies could be lost
to the world to our advantage, but perhaps no other order
of insects has so large a proportion of its members in the
category of insect pests. The single Hemipterous species
Blissus leucopterus, better known by its vernacular name
of chinch-bug, causes an annual loss to grain of twenty
millions of dollars; the grape phylloxera destroyed the
vines on 3,000,000 acres of France's choicest vineyards;
the San Jose scale has in the last ten years spread from
California to every other State and Territory in the United
States and become a menace to the whole fruit-growing
industry. So despite their small size and their general
unfamiliarity to laymen, the Hemiptera are found by eco-
nomic entomologists, in their warfare against the insect
scourges of the country, to be one of the most formidable
of all the insect orders."

Remedies for sucking insects are not readily found.
Kerosene emulsion is the one chiefly employed. Fumiga-
tion or spraying with tobacco is effective on a small scale,
and for scale insects when the leaves are off the trees,
hydrocyanic acid fumigation or lime-sulphur-salt spraying
are used. The orange-scale has been successfully held in
check by importing and fostering a lady-bird beetle which
feeds upon it; and the chinch-bug by introducing a para-
sitic fungus which kills the bugs by wholesale when the
weather conditions favor its spread.

The order 'Orthoptera' includes the cockroaches, lo-
custs, grasshoppers and crickets, all familiar types of in-
sects, many of them of large size, and several ranking
among the important noxious insects. On the other hand,
their active leaping and noisy flight, their cheerful trilling
and chirping lend a variety and interest to outdoor life
which one might sadly miss if deprived of their compan-

50

ZOOLOGY

ionship. Their music is rather instrumental than vocal,
since it is made by rasping the wings against each other or
against the roughened inner surface of the thighs.

Fig. io

-Development of the Grasshopper. The Younger
Staces Much Enlarged. (Kellogg.)

In all this order the mouth parts are modified for biting,
and they mostly live on vegetable food, especially upon
green leaves. In the grasshoppers, locusts and crickets the
hind limbs are modified for leaping; the cockroaches,
praying insects and walking-sticks are walking or running
types. The roaches are one of the most ancient and per-
sistent groups of insects. They shared with the dragon-

THE HIGHER INVERTEBRATES 51

flies the dominance of the ancient forests of the Coal
Period, and are to-day a familiar household pest, especially
in tropical countries and aboard ships. The mantis or
praying-insect is a carnivorous type, feeding upon flies or
other insects which may come within reach, and its curious-
attitudes have caused a variety of fanciful or supersti-
tious legends to gather around it. To kill a mantis is very
generally considered sinful or unlucky, and among the
quaint monkish legends is one of St. Francis Xavier, who„
"seeing a mantis moving along in its solemn way, hold-
ing up its two fore legs as in the act of devotion, desired
it to sing the praise of God, whereupon the insect caroled
forth a fine canticle."

The most singular of the Orthopterous insects are the
walking-sticks, which mimic the green twigs and stalks of
grass among which they live, in form, color and character-
istic attitudes, so closely that they are one of the best ex-
amples of "protective mimicry."

The swarms of locusts which from time to time descend
upon cultivated agricultural regions, devouring every
green thing in their path, and bringing ruin and desola-
tion to the farmer, are now known to be normally inhabi-
tants of the high-lying grassy plains, driven from their
accustomed feeding grounds by exceptionally dry seasons-
which have withered and destroyed the grass of the high
plains. They cannot maintain themselves permanently in
the moist climate of the low-lying valleys; and for their
periodical incursions there is little remedy except to fight
them in the high dry plains which are their natural home.

The Termites, or White Ants, are quite unrelated to
the true ants, and quite unlike them in appearance. They
belong to the lower orders of insects; the young are like
the adult from the time they emerge from the egg, and do
not undergo any metamorphosis. But, like the ants, they
have an elaborate social organization and live in great
colonies, mainly composed of sterile workers of several
castes. Among the ants, bees and wasps these sterile

52 ZOOLOGY

-workers are always females ; with the termites they are of
both sexes. The colony is presided over by a "royal pair"
whose functions are confined to egg-laying. As with the
ants, the workers are wingless, and the fertile males and
females are winged only during the swarming season,
when they leave the nest to found new colonies.

Termites live upon dead wood and are abundant mainly
in tropical or sub-tropical regions, where they are fear-
fully destructive to all wooden buildings, furniture, etc.,
except they be constructed from some of the few kinds
of wood that are immune to their attacks. The great hil-
lock nests which they construct are a prominent feature
of the landscape in some parts of tropical Africa. Their
habits and complex social organization are almost as re-
markable as those of the ants, but the communal instinct
is not quite so strongly developed.

With the Beetles, or 'Coleoptera/ begins the series of
higher insects with complete metamorphosis. That is to
say, the young develop from the egg into a larva, quite
unlike the adult in form, structure and habits, wingless
and more or less worm-like in appearance and habits.
After a period of active growth the larva becomes quies-
cent, wrapping itself up usually in a cocoon or protective
case, and undergoes a remarkable change, the organs and
tissues of the body being largely broken down and re-
formed, and finally the completed insect, or imago, issues
from the cocoon or cell, perfect in form and widely differ-
ent from the larva not merely in its external form, but in
the whole internal structure as well. This extraordinary
change, which has often been used as an apt natural illus-
tration of ethical regeneration, is one of the most strik-
ing and wonderful features of insect life. It is completely
carried out in the beetles, moths and butterflies, the lace-
winged flies, the two-winged flies, and in the ants, bees
and wasps. The lower orders of insects exhibit various
degrees of approximation toward it, but in none of them
is it complete.

THE HIGHER INVERTEBRATES 53

The beetles include a vast multitude of different species
and genera — 12,000 species are known from the United
States and Canada alone. All of them are distinguished
by the hard, horny fore-wings which serve as a sheath for
the membranous hind wings, these alone being used for
flight. The body is compact in form, covered by hard,
horny skin, and the mouth parts are adapted for biting,
, the jaws often strong and large. Some beetles are pre-
daceous, others, and these the great majority, are plant
eaters, and some of them are notorious pests. Among the
noxious beetles may be especially noted the "potato-bug,"
wire-worms, white grubs and other beetle larvae, fruit and
grain weevils, apple-tree borers', and a host of less im-
portant ones. The predaceous beetles, on the other hand,
are actively beneficial by destroying quantities of noxious
insects.

Among the handsomest members of the order are the
tiger-beetles and the various predaceous ground-beetles,
active, alert, many of them of bright metallic color pat-
terns. Many beetles, like the fireflies and glow-worms, are
luminous at night; some of the tropical fireflies emit light
enough to read by when a few of them are placed under a
glass. The stag-beetles and rhinoceros-beetles are among
the largest of a group (Lamellicornia) notable for the
huge mandibles and various peculiar horn-like processes
developed in the males of many of the species. The
numerous kinds of wood-boring species, some of them of
giant size, do serious damage to orchards and forests.
The little round ladybird beetles or ladybugs, with their
"polka-dot" pattern of red and black, on the other hand,
are a great help to the gardener and fruit-raiser, as they
feed upon plant-lice and scale-insects. In the large group
which includes the curculios, weevils and snout-beetles,
the front of the head is prolonged into a long beak, at the
tip of which are the small, sharp jaws; many of these
also are serious insect pests.

The 'Diptera,' or Two-winged Flies, includes gnats, mos-

54 ZOOLOGY

<mitoes and the innumerable kinds of true flies, an im-
mense group, including some fifty thousand species, many
of them familiar from the annoyance they inflict on men
and animals, and in recent years more seriously considered
as carriers of disease. The mouth parts in all are adapted
for sucking and piercing, and they have but two wings,
the hinder pair being converted to little structures which
are used to balance or direct the fly in his flight.

The mosquitoes are familiar from the tropics to the
poles, but it is only in recent years that their relations to
three serious diseases of man have been suspected and
proved. It has been shown beyond question that the
germs of malaria, yellow fever and filariasis are trans-
mitted from man to man through the agency of mosqui-
toes. The life history of the malaria germ has been quite
thoroly investigated. Malarial fever, which is the most
•deadly disease of the tropics, is caused by a minute amceba-
like one-celled organism, parasitic in the blood-corpuscles.
These grow and multiply asexually in the human blood,
but their sexual multiplication occurs within the stomach-
cavity of the mosquito 'Anopheles.' Thence they make
their way to the poison-gland of the insect, and are so in-
troduced into the body of the next person bitten by this
species. The 'Anopheles' is the mosquito with spotted
wings, fortunately less common than the gray-winged or
brindled-winged mosquitoes of the genus 'Culex.' An-
other mosquito, 'Stegomyia,' is responsible for the dissem-
ination of yellow fever and of filariasis, the life history
of the germ proceeding along much the same lines as with
the malaria germ, so far as it has been investigated. The
destruction of mosquitoes, especially of the 'Anopheles'
and 'Stegomyia,' and protection from their attacks, have
consequently been recognised as a most important safe-
guard to health, especially in tropical countries. Protec-
tion is chiefly to be had by extensive and thoro screening
of houses and porches; destruction of the mosquito larvae
can be effectively accomplished by draining swamps and

THE HIGHER INVERTEBRATES

55

stagnant pools in which they chiefly breed, and where
draining is impossible by periodically covering the surface
of the water with a thin film of kerosene. Standing water
in cisterns or rain-barrels should be carefully screened.
By these methods of prevention the mortality from ma-
larial fever and yellow fever in tropical regions has been
greatly reduced when, as in the construction of the Panama
Canal, they have been systematically and thoroly applied*

Fig. ii — A Blow-fly; Larva, Pupa and Adult.
This fly lays its eggs on fresh or decaying meat. (Kellogg.)

The smaller gnats and midges are nearly related to the
mosquitoes, and are equally a pest throughout the world
from their bloodthirsty habits.

The compact heavy-bodied flies, with short antennae, are
a much larger group than the mosquitoes, and many of
them attain large size. The great majority are harmless
to man, a few beneficial as they prey upon noxious insects ;
but some do serious injury to growing crops, the larvae
or maggots feeding upon the leaves or roots of the plants ;

56 ZOOLOGY

a few, such as the bot-flies, are parasitic upon animals or
man ; and others, like the house-flies, blow-flies and their
allies, are annoying and disgusting pests and dangerous
spreaders of disease. The agency of the house-fly in
disseminating typhoid fever in cities and camps has been
properly appreciated only in recent years. Doctor L. O.
Howard has recently suggested that in view of its activi-
ties in this direction it might most appropriately be called
the "typhoid fly." This fly breeds in stable-manure and
other decaying matter, and thoro cleanliness and sanita-
tion has already accomplished wonderful results in reduc-
ing the death-rate from diseases which are largely spread
through its agency.

Related to the flies, altho given a separate ordinal rank,
are the fleas, degenerate blood-sucking parasites of mam-
mals and birds which likewise take part in the dissemina-
tion of certain diseases. They are wingless, with pecu-
liarly compressed bodies and mouth parts adapted for
piercing and sucking.

"The Moths and Butterflies (order Lepidoptera) are
the insects," says Kellogg, "most favored of collectors and
nature lovers; a German amateur would call them the
'Lieblings-insekten.' The beautiful color patterns, the
graceful flight and dainty flower-haunting habits, and the
interesting metamorphosis in their life history make them
very attractive, while the comparative ease with which the
various species may be determined, and the large number
of popular as well as more technical accounts of their life
which are accessible for information, render the moths
and butterflies most available, among all the insects, for
systematic collecting and study by amateurs."

This great group of insects ranks with the beetles and
flies in abundance and variety. Between six and seven
thousand species are found in North America alone, but
they are even more numerous and varied in tropical re-
gions. They attain their greatest size and beauty of color

THE HIGHER INVERTEBRATES

57

and pattern in the equatorial forest regions, especially in
South America.

The exquisite color patterns are due to the covering of
minute scales over wings and body. The scales, which are

j — Development of a Butterfly, Illustrating Complete
Metamorphosis.
A., egg (greatly magnified) ; B., larva or caterpillar ; C, pupa or
chrysalis; D., imago or adult butterfly. (Jordan and Kellogg.)

to be regarded as modified hairs, vary in shape and size
(from Ysso to '/so inch) and their brilliant metallic col-
ors are mainly due to diffraction of light from their finely
striated surfaces, while the black, brown, yellow and dull

58 ZOOLOGY

red colors are due to pigment-color in the scale itself. In
this group are to be found the most striking examples of
protective coloration, of warning colors, of mimicry, and
other more obscure phases of adaptive coloration.

The Lepidoptera all undergo a complete metamorphosis,
and their caterpillars are more familiar objects than the
larvae of any other group of insects, as they live mostly
on green leaves and are active and voracious feeders.
Owing to their habits and numbers, many of the larvae
rank among the plagues of farmer, gardener or tree-
grower. The adults, mostly nectar-sipping, are harmless
as they are often beautiful. The silk-moth, from whose
cocoons the world's supply of silk is obtained, is also of
high economic importance. The annual production of
raw silk is estimated at over $100,000,000. Yet this is but
small, probably, compared with the total amount of dam-
age done to gardens, orchards and fields by the depreda-
tions of the various caterpillars of one kind or another.

Among butterflies the palm is generally given to the
giant Morphos and their relatives, whose brilliant metallic
colors brighten the gloomy recesses of the Brazilian for-
ests. These, like many other inhabitants of the deep for-
est, habitually fly far above the ground, among the tree-
tops, and are consequently more difficult to secure. In
temperate climates the swallow-tailed butterflies, 'Papilio*
and its relatives, are the most widely admired. One of
the most familiar of the larger butterflies is the "mon-
arch/' which owes its success in life partly to its secret-
ing an acrid, ill-tasting fluid that causes birds to let it
severely alone. This butterfly is closely mimicked by an-
other, the "viceroy," which is not ill-tasting, but doubtless
profits by this resemblance in escaping the attacks of birds.

The order Hymenoptera, in which are included Ants,
Bees and Wasps, is the most interesting group among all
the lower animals, because many of its members have a
highly complicated and elaborated communal life. The
study of these great insect societies, of their social life,

THE HIGHER INVERTEBRATES

59

habits and instincts, is one of the most interesting subjects
in the whole range of natural history. From the days of
Solomon the tireless industry and frugality of the ant

Fig. 13 — Swallow- tailed Butterfly (Papilkj), One-half Nat-
ural Size. (Kellogg.)

have been proverbial. The busy ways, the complicated
and orderly activities of the bee, are familiar to every one,
and Maeterlinck's brilliant and sympathetic description

60 ZOOLOGY

of the life of the great bee communities in his The Life of
the Bee/ altho perhaps too much tinged with the natural
tendency to interpret it in terms of human reason and
sensations to be wholly reliable, is one of the most fas-
cinating chapters of natural history ever written.

Besides these better known social insects the Hymenop-
tera include a variety of solitary forms, saw-flies, gall-
flies and ichneumons,' and among the bees and wasps there
are all degrees of social organization, from solitary to
highly elaborated social types. It is especially through the
study of these various grades of organization that an
understanding can be obtained of the true meaning of
many features of the social life of ants and bees, and of
how they were developed.

In order to appreciate the character and limitations of
their social life, it is necessary first to get some insight^
into the nature of this intelligence. The nervous system
in insects and crustaceans consists of a double cord on
the ventral side of the body with paired nodes or ganglia
at each segment from which the nerves are distributed,,
and a pair of principal ganglia on the dorsal side of the
head connected with the ventral system by a ring of nerve
fibers encircling the gullet. In the higher insects the dor-
sal ganglia of the head are expanded into a small mas*
which corresponds in the main with the brain of the higher
animals. But the ventral ganglia also perform part of the
functions which in the vertebrates are concentrated in the
brain, and the relative size and complexity of the brain
mass in insects is by no means to be compared with any
of the higher vertebrates. The deficiency is especially
in the parts corresponding to the cerebrum lodging the
higher intelligent and reasoning powers, the automatic
and instinctive acts being governed mainly by the enlarged
ventral ganglia.

So far as can be judged, the nervous system of an insect
is that of a very elaborate and perfect animal automaton,
but not much more. It is natural to suppose, on seeing the

THE HIGHER INVERTEBRATES 61

complex and varied activities of an ant or bee community,
that these insects must possess an intelligence comparable
with that of man rather than of the lower animals; and
ideas of their life are apt to be colored by this view. But
the most eminent modern authorities on their psychology,
among whom Professor Forel may be especially men-
tioned, believe that, while not devoid of intelligence, their
actions are in the main instinctive and automatic, and that .
even their intelligent action degenerates into habit — that
is, tends to become automatic — much more rapidly than in
higher animals.

The extreme complexity of these instincts can be better
understood if it is remembered thai the insects are a very
ancient group. Little of their early history has been defi-
nitely ascertained, but the lower orders of insects, at least
such as cockroaches and dragon-flies, appeared far back
in the age of invertebrates, almost as early as the begin-
ning of the geologic record; and the higher orders are
known to have existed at a time when highest vertebrates
had not advanced beyond the modern salamanders and
newts. During the millions of years since that time, while
the vertebrates were slowly developing an intelligent
brain, the higher insects were elaborating an instinct
brain.

The most serious difficulty in understanding the actions
of insects is that their senses are so different from those
of Man. Broadly speaking, indeed, they make use of the
same media of communication with the outer world. All
of them have organs sensitive to ether rays of light and
heat, corresponding to human eyesight and to the sense
of heat and cold. Most of them have apparatus to sense
the waves of sound, altho less developed than the ears
of vertebrates, and different in mechanism. All of them
have organs for perception of solid bodies and of the
minute particles given out from them, corresponding to
the senses of touch, taste and smell, but differently sit-
uated and combined, and generally much more elab-

62 ZOOLOGY

orated. The antennae of insects are sensitive to touch and
odor, and in most of the higher insects are highly special-
ized organs. In the ants especially they usurp the place
which in most animals is taken by the eyes.

"Picture to yourself," says Forel, "an olfactory sense —
i.e., a chemical sense effective at a distance and, like our
sense of smell, capable of receiving impressions from par-
ticles of the most diverse substances diffused through the
atmosphere — located not on your nostrils but on your
hands. For of such a nature is the position of the olfac-
tory sense on the antennal club of the ant.

"Now imagine your olfactory hands in continual vibra-
tion, touching all objects to the right and to the left as
you walk along, thereby rapidly locating the position of all
odoriferous objects as you approach or recede from them,
and perceiving the surfaces both simultaneously and suc-
cessively as parts of objects differing in odor and position.
It is clear from the very outset that such sense organs
would enable you to construct a veritable odor-chart of the
path you had traversed and one of double significance:
(i) A clear contact-odor chart, restricted, to be sure, to
the immediate environment, and giving the accurate odor-
form of the objects touched (round odors, rectangular
odors, elongate odors, etc.), and, further, hard and soft
odors in combination with the tactile sensations; (2) a
less definite chart which, however, has orienting value for
a certain distance, and produces emanations which we may
picture to ourselves like the red gas of bromine which we
can actually see.

"If we have demonstrated that ants perceive chemical
qualities through their antennae both from contact and
from a distance, then the antenna? must give them knowl-
edge of space, if the above formulated law is true, and
concerning this there is little doubt. This must be true
even from the fact that the two antennae simultaneously
perceive different and differently odoriferous portions of
space. They must therefore also transmit perceptions and

THE HIGHER INVERTEBRATES 6$

topographically associated memories concerning a path
thus touched and smelled. Both the trail of the ants them-
selves and the surrounding objects must leave in their
brains an odor-image of immediate space, and this must
render associated memories possible. Thus an ant must
' perceive the forms of its trail by means of smell. This is
impossible, at least for the majority of the species, by
means of the eyes."

It will appear therefore that this antennal sense, which
Forel designates as topographical, is the principal means
by which the brain of the ant is placed in communication
with the outside world, supplying the space and form per-
ceptions in the same way that ,a vertebrate's eyes do.
Light and darkness are indifferent to an ant, so far as
getting about is concerned. Many of the species use their
eyes, but do not depend primarily on them ; others are
blind or nearly so. This topochemical sense is present in
other insects to a varying extent. In Bees and Wasps it
is well developed, altho not to the exclusion of sight as in
Ants. In Flies and Dragon-flies and in most of the lower
insects it is more or less rudimentary; they depend chiefly
upon the eyes.

There are other wide differences in the external sense
organs of the various insects from man and from each
other. Insects see colors differently; they hear sounds
to which the human ear is not sensitive, while they are
deaf to tones that it perceives. Their world of percep-
tions is so different in its nature and its limitations that
it is difficult to enter very far into the psychology even
of their simplest sensations. For the most part the facts
can only be related as they appear ; the ever-present temp-
tation to interpret the actions of an insect in the terms of
the observer's sensations is almost sure to lead him astray.

In most of the lower animals the young are well able to
take care of themselves. In general they develop from
the egg with little or no help from their parents. But in
the Hymenoptera, as in birds and mammals, the young

64 ZOOLOGY

are helpless larvae, unable to forage for themselves, and
requiring to be supplied with food, or fed directly, by the
adults. This is the most important fact in the life history
of these insects. It differentiates them as of distinctly
higher type than any other invertebrates, and it is around
the care of the young that their social life chiefly centers.
It has been well observed that in man the duration and
helplessness of infancy is in direct proportion to the
progress of civilization. It is equally true of the lower
animals, that those in which the young require and obtain
the help of their parents in their early life are thereby
enabled to reach a higher stage in development than those
in which the young can and do shift for themselves from
the time they emerge from the egg.

All of the Hymenoptera make provision in one way
or another for their young, and the extent to which this
care is carried is the index of development in the different
groups.

The Saw-flies, the lowest member of the group, merely
place the eggs in favorable spots on the stems of plants,
where the larvae can feed readily upon the juices of the
plant. These larvae are little more helpless than true
caterpillars and feed in much the same way.

The Gall-flies show the next stage in progress ; the eggs
are laid in the leaves or stems of various plants in such a
position that the irritation of their presence stimulates the
plant to develop abnormal growths or galls, which are
utilized as food by the larvae.

The Ichneumon-flies lay their eggs in the bodies of
caterpillars, and the larva develops at the expense of its
unfortunate host. A great variety of the lower Hymenop-
tera are parasitic in this way upon other insects of various
orders, and the parasitism has entailed more or less de-
generacy. The life histories of these various parasitic
forms form a very curious and interesting chapter in natu-
ral history.

CHAPTER V

INSECT SOCIAL COMMUNITIES

The study of the habits of Solidary Wasps and Bees and
the transitional forms between these and the social kinds
gives the clue to the method of development of these great
insect societies and helps to explain many features of their
life otherwise incomprehensible. In the first place, it is
evident that their activities center largely around the care
for the young. The larva develops from the egg as a
helpless footless maggot, unable to forage for itself,
unable to protect itself from enemies. It is dependent
among Bees and Wasps upon the food supply stored up in
the cell with the egg ; among Ants it is fed directly by the
workers by regurgitation from their crops.

Solitary Wasps form a group to be considered by them-
selves. Thus the Digger-wasp ('Sphex') does not live in
communities, but the females make separate nests, one
for each egg, provisioning them with insect prey which
they sometimes kill, but more generally merely paralyze
beforehand by stinging them. J. H. Fabre describes their
habits in his Tnsect Life' as follows :

"The nests may be of mud and attached, for shelter,
under leaves, rocks or eaves of buildings, or may be bur-
rows hollowed out in the ground, in trees or in the stems
of plants. The adult wasp lives upon fruit or nectar, but
the young grub or larva must have animal food, and here
the parent wasp shows a rigid conservatism, each species
providing the sort of food that has been approved by its
65

66 ZOOLOGY

family for generations, one taking flies, another bugs,
and another beetles, caterpillars, grasshoppers, crickets,
locusts, spiders, cockroaches, aphids or other creatures, as
the case may be.

"The Solitary Wasps mate soon after leaving the nest
in the spring or summer. The males are irresponsible
creatures, aiding little, if at all, in the care of the family.
When the egg-laying time arrives the female secures her
prey, which she either kills or paralyzes, places it in the
nest, lays the egg upon it, and then in most cases closes
the hole and takes no further interest in it, going on to
make new nests from day to day. In some genera the
female maintains a longer connection with her offspring,
not bringing all the provisions at once, but returning to
feed the larva as it grows and only leaving the nest per-
manently when the grub has spun its cocoon and become
a pupa.

"The egg develops in from one to three days into a foot-
less maggot-like creature which feeds upon the store pro-
vided for it, increasing rapidly in size and entering the
pupal stage in from three days to two weeks. In the
cocoon it passes through its final metamorphosis, emerging
as a perfect insect perhaps in two or three weeks, or, in
many cases, after the winter months have passed and
summer has come again. Probably no Solitary Wasp
lives through the winter, those that have come out in the
spring or summer perishing in the autumn."

"The habit common to almost all of the Solitary
Wasps," says Kellogg, "of so stinging the prey, cater-
pillars, spiders, beetles, flies, bugs, or whatever other in-
sects are used to provision the nests, as not to kill but only
to paralyze it, is perhaps the most amazing part of all the
interesting behavior of all these wasps. The advantage is
obvious : killed, the prey would quickly decompose, and
the hatching carnivorous wasp larva would have only a
mass of, to it, inedible decaying flesh, instead of the fresh
live animal substance it demands. But if stored unhurt,

INSECT SOCIAL COMMUNITIES

67

the prey would, if a cricket or spider or similarly active
animal, quickly escape from the burrow, or if a caterpillar
or weak bug, at least succeed, albeit unwittingly, in crush-
ing the tender wasp Qgg by wriggling about in the under-
ground prison cell.

"More than that, unhurt, some insects could not live
without food the many days that are necessary for the
development of the wasp larva, especially in the face of
the frantic and exhausting efforts they would be impelled
to in their attempts to escape. But paralyzed, there is no

Fig. 14 — Ammophila.
Solitary wasps, stocking their burrows with paralyzed insects as
food for their young. (Kellogg.)

exertion; metabolism is slight, and life without food is
capable of being prolonged many days. The paralysis is
due to the stinging by the Wasp of one or more of the
ganglia (nerve centers) of the ventral nerve cord. The
amazing expertness and accuracy displayed in plunging
the sting into exactly those spots where injury will give
rise to exactly that physiological phenonenon in the prey
that will make it available for the special conditions at-
tending the wasp larva's sustenance — this adroitness and
this seeming knowledge of the structure and the physi-
ology of the prey have led some entomologists to credit
the Solitary Wasp with anthropomorphic qualities that are
quite unwarranted. The whole behavior is probably ex-

68 ZOOLOGY

plicable as a complex and advantageous reflex or instinct,
developed by selection.

"Similarly, the whole course of the nest building and
provisioning is an elaborate performance wholly for the
sake of the young, which the mother will likely never see;
and these young in turn will, if females, do the same thing,
perfectly, and in essentially, if not exactly, the same man-
ner, without ever previously seeing such remarkable proc-
esses performed. All these complex and altruistic habits
have naturally led to much speculation concerning their
origin and their relation to psychical conditions. Whether
a consciousness of what is being done and an intelligence
is brought to bear upon its doing; whether we may at-
tribute to the wasp a psychical state, with its attributes of
cognizance, reason and emotion — these are questions
which are debated warmly. The consensus of opinion,
however, is distinctly adverse to reading into the behavior
of 'Ammophila' or any of its allies anthropomorphic at-
tributes of reason, consciousness or emotion. The fixity
and inevitableness which is preeminently characteristic of
the behavior of the wasps, and the fact that each female
is 'ab ovo' adequate to carry through the complex train of
actions without teaching, experience or opportunity for
imitation, practically prove all this seeming marvel of
reasoned care for the future young to be an inherited in-
stinct incapable of essential modification except by the
slow process of selection through successive generations."

The Social Wasps — Hornets, Yellow-jackets and such
— live in great communities of males, females and a third
caste, the neuters or workers. These last are in reality
sterile females, taking no part in the reproduction of the
race, but take charge of the building and caring for the
nest of the community, bringing food and rearing the
young.

The life-history of a community in general outline is
given by Kellogg as follows: "In the early spring, fertil-
ized females (queens) which have hibernated (as adults)

INSECT SOCIAL COMMUNITIES 69

in sheltered places, as crevices in stone walls, under logs,
stones, etc., come out from their winter hiding places and
each makes a small nest, containing a few brood cells. In
each cell an egg is laid, and food, consisting of insects,
killed and somewhat masticated, is hunted for and brought
to the larvae throughout their brief life by the queen. The
larvae soon pupate in the cells and in a few days issue as
winged wasps. They are exclusively workers. These
workers now enlarge the nest, adding more brood cells in
which the queen deposits eggs. The bringing of food and
the care of the young now devolve on the workers.

"The new, or second, brood also is composed of workers
only, and these immediately reinforce the first brood in the
work of enlarging the nest and building new brood cells.
Thus, through the summer, several broods of workers are
reared until in the late summer or early fall a brood con-
taining males and females as well as workers appears.
The community is now at its maximum, both as regards
population and size of nest. In the species 'Vespa,' which
make the great ball-like aerial nests, the community may
grow to number several thousand individuals. The males
and females mate (presumably with members of other
communities), but no more eggs are laid, and with the
gradual coming on of winter the males and workers and
many of the females die. There persist only as survivors
of each community a few fertilized females. These craw!
into safe places to pass the winter. Any Social Wasp
found in winter time is thus almost certainly a queen.
Those of the queens which come safely through the long
winter found the communities which live through the fol-
lowing season.

"The Social Wasps of the genus Vespa, the familiar
Yellow-jackets and Hornets, are the ones which build the
large subspherical nests familiar to all outdoor observers
and related to much boyish adventure. Inside the great
globe are several horizontal combs of brood cells in tiers,
all enclosed by several layers of wasp-paper. The large

70 ZOOLOGY

bald-faced Hornet, 'Vespa maculata,' is the best known
builder of the globe nests. The smaller Yellow-jackets
('Vespa germanica,' 'Vespa cuneata') build in hollows in
stumps or stone fences or underground. Such protected
or underground nests are not as thoroly or thickly en-
veloped in paper as are the exposed arboreal globe nests.
The miniature queen nests of the 'Vespa,' with the single
little brood comb inside, may often be found by careful
searching in the spring.

"The long-bodied, blackish Wasps of the genus 'Polistes'
build single exposed horizontal combs out of wasp-paper
(chewed wood), which are attached to the under side of
porch roofs, eaves, ceilings of outbuildings, etc., by a short
central stem. The little comb made by the queen may
contain but half a dozen cells, but after the workers hatch
many other cells are added around the margin. But the
nest and workers never compare in size and numbers with
the large communities of 'Vespa.' "

Among all the Wasps the adult feeds upon nectar of
flowers, but the larva is fed on insects, paralyzed or
freshly killed. The Solitary kinds store up food and place
it in the cell with the egg; the Social Wasps do not, but
the queen at first and afterward the workers forage for
insects, which they bring in constantly and feed to the
larvae in a killed and partially masticated condition.

Bees differ from Wasps in that the young larva, as wTell
as the adult, is fed upon the nectar and pollen of flowers,
converted into honey and bee-bread, instead of upon insect
food as in the Wasps. The structure of the mouth parts
and the instincts of the Bee differ accordingly. There are
a great many kinds of Solitary Bees, but the Social Bees,
the wild Bumblebee and the Hive-bee are by far the most
familiar. In the Solitary Bees there are only males and
females; in the Social Bees, as in Social Wasps, there are
males, females and workers. The Bumblebees nest under-
ground, occupying and enlarging a mouse-hole or small
burrow, and the life-history of the community is much

INSECT SOCIAL COMMUNITIES 71

like that of the Wasps. They do not make honey cells,
but mix pollen and honey to a pasty mass, deposit a few
eggs upon the mass, and in the later stages of the nest
build waxen cells for the larva? to pupate in.

The Honey Bees ('Melipona' and 'Apis') have a much
more elaborated community life, and unlike the Wasps
and Bumblebees, this does not terminate with the sum-
mer, but is continuous from season to season. The Meli-
ponas are tropical bees, stingless or nearly so, living in
immense communities whose life-history is not completely
known. The better known Hive-bees ('Apis') are native
to the Old World, but domesticated and introduced every-
where. The habits and life-history of the great Hive-bee
communities have been more carefully studied than any
other phase of insect life. Yet there are many unsolved
problems, especially in regard to the interpretation and
meaning of their behavior.

A well-written and reliable account of the life of the
Hive-bees is given in Jordan and Kellogg's 'Evolution
and Animal Life,' from which the following may be
quoted :

"An interesting series of gradations from a strictly
solitary through a gregarious to an elaborately special-
ized communal life is shown by the bees. Altho the
Bumblebee and the Honey Bee are so much more fa-
miliar to us than other bee kinds that the communal life
exemplified by them may have come to seem the usual
kind of bee life, yet, as a matter of fact, there are many
more solitary bees than social ones. The general char-
acter of the domestic economy of the solitary bees is
well shown by the interesting little Green Carpenter Bee,
'Ceratina dupla.' Each female of this species bores out
the pith from five or six inches of an elder branch or
raspberry cane, and divides this space into a few cells
by means of transverse partitions. In each cell she lays
an egg, and puts with it enough food — flower pollen — to
last the grub or larva through its life. She then waits

7*

ZOOLOGY

in an upper cell of the nest until the young bees issue
from their cells, when she leads them off, and each begins
active life on its own account.

"The Mining Bees, 'Andrena/ which make little burrows
in a clay bank, live in large colonies — that is, they make
their nest burrows close together in the same clay bank,

Nests of Carpenter and Mining Bee.

but each female makes her own burrow, lays her own
eggs in it, furnishes it with food — a kind of paste of nec-
tar and pollen — and takes no further care of her young.
Nor has she at any time any special interest in her neigh-
bors. But with the smaller Mining Bees, belonging to
the genus 'Halictus,' several females unite in making a
common burrow, after which each female makes side pas-

INSECT SOCIAL COMMUNITIES 73

sages of her own, extending from the main or public en-
hance burrow. As a well-known entomologist has said,
" 'Andrena' builds villages composed of individual homes,
while 'Halictus' makes cities composed of apartment
houses."

"The Bumblebee, however, establishes a real commu-
nity with a truly communal life, altho a very simple one.
The few Bumblebees which we see in winter time are
queens; all others die in the autumn. In the spring a
queen selects some deserted nest of a field mouse, or a
hole in the ground, gathers pollen which she molds into
a rather large irregular mass and puts into the hole, and
lays a few eggs on the pollen mass. The young grubs or
larvae which soon hatch feed on the pollen, grow, pupate,
and issue as workers — winged bees a little smaller than
the queen. These workers bring more pollen, enlarge
the nest, and make irregular cells in the pollen mass, in
each of which the queen lays an egg. She gathers no
more pollen, does no more work except that of egg-lay-
ing. From these new eggs are produced more workers,
and so on until the community may come to be large.
Later in the summer males and females are produced and
mate. With the approach of winter all the workers and
males die, leaving only the fertilized females, the queens,
to live through the winter and found new communities
in the spring.

"The Social Wasps — as with the bees, there are many
more kinds of solitary wasps than social ones — show a
communal life like that of the Bumblebees. The only
Yellow-jackets and Hornets that live through the win-
ter are fertilized females or queens. When spring comes
each queen builds a small nest suspended from a tree
branch, or in a hole in the ground, which consists of a
small comb enclosed in a covering or envelope open at
the lower end. The nest is composed of 'wasp-paper/
made by chewing bits of weather-beaten wood taken from
all fences or outbuildings. In each of the cells the queen

74

ZOOLOGY

lays an egg. She deposits in the cell a small mass of
food, consisting of some chewed insects or spiders. From
these eggs hatch grubs which eat the food prepared for
them, grow, pupate, and issue as worker wasps, winged
and slightly smaller than the queen. The workers en-
large the nest, adding more combs and making many
cells, in each of which the queen lays an egg. The

Fig. 1 6 — Bumblebee and Hornet.
Upper figures, workers ; lower figures, queens.

workers provision the cell with chewed insects, and other
broods of workers are rapidly hatched. The community^
grows in numbers and the nest grows in size until it comes
to be the great ball-like oval mass which we know so
well as a hornets' nest, a thing to be left untouched.
When disturbed, the wasps swarm out of the nest and
fiercely attack any invading foe in sight. After a number
of broods of workers has been produced, broods of males

INSECT SOCIAL COMMUNITIES 75

and females appear and mating takes place. In the late
fall the males and all of the many workers die, leaving
only the new queens to live through the winter.

"Honey Bees live together, as we know, in large com-
munities. We are accustomed to think of Honey Bees as
the inhabitants of beehives, but there were bees before
there were hives. The 'bee tree' is famili-ar to many of us.
The bees, in nature, make their home in the hollow of
some dead or decaying tree-trunk, and carry on there all
the industries which characterize the busy communities
in the hives. A Honey Bee community comprizes three
kinds of individuals — namely, a fertile female or queen,
numerous males or drones, and many infertile females or
workers. These three kinds of individuals differ in ex-
ternal appearance sufficiently to be readily recognisable.
The workers are smaller than the queens and drones, and
the last two differ in the shape of the abdomen, or hind
body, the abdomen of the queen being longer and more
slender than that of the male or drone. In a single com-
munity there is one queen, a few hundred drones, and ten
to thirty thousand workers.

"The number of drones and workers varies at different
times of the year, being smallest in winter. Each kind
of individual has certain work or business to do for the
whole community. The queen lays all the eggs from
which new bees are born ; that is, she is the mother of the
entire community. The drones or males have simply to
act as royal consorts; upon them depends the fertilization
of the eggs. The workers undertake all the food-getting,
the care of the young bees, the comb-building, the honey-
making — all the industries with which we are more or less
familiar that are carried on in the hive. And all the
work done by the workers is strictly work for the whole
community; in no case does the worker bee work for
itself alone; it works for itself only in so far as it is a
member of the community.

"How varied and elaborately perfected these industries

76 ZOOLOGY

are may be perceived from a brief account of the life
history of a bee community. The interior of the hollow
in the bee tree or of the hive is filled with 'comb' — that
is, with wax molded into hexagonal cells and supports
for these cells. The molding of these thousands of sym-
metrical cells is accomplished by the workers by means
of their specially modified trowel-like mandibles or jaws.
The wax itself, of which the cells are made, comes from
the bodies of the workers in the form of small liquid
drops which exude from the skin on the under side of the
abdomen or hinder body rings. These droplets run to-
gether, harden and become flattened, and are removed
from the wax plates, as the peculiarly modified parts of
the skin which produce the wax are called, by means of
the hind legs, which are furnished with scissor-like con-
trivances for cutting off the wax.

"In certain of the cells are stored the pollen and honey,
which serve as food for the community. The pollen is
gathered by the workers from certain favorite flowers
and is carried by them from the flowers to the hive in the
'pollen baskets/ the slightly concave outer surface of one
of the segments of the broadened and flattened hind legs.
This concave surface is lined on each margin with a row
of incurved stiff hairs, which hold the pollen mass se-
curely in place.

"The 'honey' is the nectar of flowers which has been
sucked up by the workers by means of their elaborate
lapping and sucking mouth parts and swallowed into a
sort of honey-sac or stomach, then brought to the hives
and regurgitated into the cells. This nectar is at first
too watery to be good honey, so the bees have to evaporate
some of this water. Many of the workers gather above
the cells containing the nectar and buzz — that is, vibrate
their wings violently. This creates currents of air which
pass over the exposed nectar and increase the evapora-
tion of the water. The violent buzzing raises the tem-
perature of the bees' bodies, and this warmth given off to

INSECT SOCIAL COMMUNITIES 77

the air also helps make evaporation more rapid. In ad-
dition to bringing in food, the workers also bring in,
when necessary, 'propolis/ or the resinous gum of cer-
tain trees, which they use in repairing the hive, as closing
up cracks and crevices in it.

"In many of the cells there will be found, not pollen or
honey, but the eggs or the young bees in larval or pupal
condition. The queen moves about through the hive,
laying eggs. She deposits only one egg in a cell. In
three days the egg hatches, and the young bee appears
as a helpless soft, white, footless grub or larva. It is
cared for by certain of the workers, that may be called
nurses. These nurses do not differ structurally from the
other workers, but they have the special duty of caring
for the helpless young bees. They do not go out for
pollen or honey, but stay in the hive. They are usually
the new bees — i.e., the youngest or most recently added
workers. After they act as nurses for a week or so they
take their places with the food-gathering workers, and
other new bees act as nurses. The nurses feed the young
or larval bees at first with a highly nutritous food called
bee jelly, which the nurses make in their stomach and
regurgitate for the larvas. After the larvae are two or
three days old they are fed with pollen and honey. Fi-
nally, a small mass of food is put into the cell, and the cell
is 'capped' or covered with wax. Each larva, after eat-
ing all its food, in two or three days more changes into
a pupa, which lies quiescent without eating for thirteen
days, when it changes into a full-grown bee. The new
bee breaks open the cap of the cell with its jaws and comes
out into the hive, ready to take up its share of the work
for the community.

"In a few cases, however, the life history is different.
The nurses will tear down several cells around some sin-
gle one, and enlarge this inner one into a great irregular
vase-shaped cell. When the egg hatches, the grub or
larva is fed bee jelly as long as it remains a larva, never

78 ZOOLOGY

being given ordinary pollen and honey at all. This larva
finally pupates, and there iss»ues from the pupa not &
worker or drone bee, but a new queen bee. The egg from
which the queen is produced is the same as the other
eggs, but the worker nurses by feeding the larva only the
highly nutritious bee jelly make it certain that the new
bee shall become a queen instead of a worker. It is also
to be noted that the male bees or drones are hatched from
eggs that are not fertilized, the queen having it in her
power to lay either fertilized or unfertilized eggs. From
the fertilized eggs hatch larvae which develop into queens
or workers, depending on the manner of their nourish-
ment; from the unfertilized eggs hatch the males.

"When several queens appear there is much excite-
ment in the community. Each community has normally
a single one, so that when additional queens appear some
rearrangement is necessary. The rearrangement comes
about first by fighting among the queens until only one
of the new queens is left alive. Then the old or mother
queen issues from the hive or tree followed by many
of the workers. She and her followers fly away to-
gether, finally alighting on some tree branch and massing
there in a dense swarm. This is the familiar phenomenon
of 'swarming.' The swarm finally finds a new hollow
tree, or in the case of the Hive-bee the swarm is put into
a new hive, where the bees build cells, gather food, pro-
duce young, and thus found a new community. This
swarming is simply an emigration, which results in the
wider distribution and in the increase of the number of
the species. It is a peculiar but effective mode of dis-
tributing and perpetuating the species. The community, it
is important to note, is a persistent or continuous one. The
workers do not live long, the spring broods usually not
over two or three months, and the fall broods not more
than six or eight months; but new ones are hatching
while the old ones are dying, and the community as a
whole always persists. The queen may live several years,

INSECT SOCIAL COMMUNITIES 79

perhaps as many as five. She lays about one million
eggs a year,"

The Ants may fairly be regarded as the highest group
of invertebrate animals. They excel in tlje variety and
complexity of their instincts and the elaborateness of their
social organization, and their abundance and wide dis-
tribution marks them as one of the most successful and
dominant types produced by evolution.

There are no solitary ants. All of them have a highly
complex social life, live in large communities composed
of males, females and workers. The workers (sterile
females) are the principal part of an ant colony; only at
the mating season do males and females appear in any
considerable numbers. The workers are wingless and
much smaller than the males and females; the latter are
winged only for the mating or swarming season, when
they leave the nest. After mating the males die and
the females or queens, throwing off their wings, proceed
each to found a new colony.

Aside from their mating flights, Ants are all strictly ter-
restrial. Their nests are a maze of underground galleries
and chambers tunneled out by the workers and serving as a
retreat for the adults, a nursery for the young, a granary
for stored-up food, and in one group of Ants as a vege-
table garden as well. The colony consists usually of a
queen-ant, or in some instances several queens, whose
duties are confined to egg laying, of a great number of
workers of two or more castes, worker-minors, worker-
majors and sometimes soldiers, and at certain seasons of
the winged males and females ready to issue from the
nest, mate and form new colonies. The duties of the differ-
ent castes of workers vary; to the youngest and smallest
ones are assigned the care of the eggs and feeding of the
larvae; the larger workers forage for food; while the sol-
diers, large-headed and with powerful jaws, apparently do
little besides protecting the nest in case of attack.

80 ZOOLOGY

Ants are primarily carnivorous; they subsist on other
insects or upon sweet juices exuding from flowers, leaves
or stems or secreted by insects. They are extremely fond
of the 'honey-dew' secreted by the plant-lice, or Aphids,
which with many of the common species forms an impor-
tant part of their food. On every plant infested by Aphids
one is pretty certain to see a number of Ants in attend-
ance,, stimulating the excretion of the honey-dew by deft
stroking. Many are the stories that have been told of the
curious relations between Ant and Aphis, but many of
them need to be verified by more careful investigation.
Nevertheless it is certain that the Ants do take care of
their 'cows,' as Linnaeus called them, in a way that is at
least suggestive of domestication. If the various Ants
attending Aphids on one plant are observed, they will be
found to be all of one species and apparently all from one
nest. One might assume from this, but probably quite
incorrectly, that Aphids were considered as personal (or
rather municipal) property among the Ants. Again, cer-
tain Ants build a sort of tent of mud or vegetable fiber
over parts of branches or stems infested with Aphids or
scale insects, and this tent serving to protect and shelter
both the Ants and their 'cows' from rain or from incur-
sions of enemies or other ants, may fairly be regarded as a
stable. Furthermore, in at least one common species of
Ant, the workers have been seen to take the newly hatched
Corn-root Aphids and carefully place them upon the roots
of certain species of knotweed, guard and protect them
there until the corn-roots were sufficiently advanced and
then to remove the Aphids to feed upon the corn. There
can be no question that the mere presence of such bold,
active and efficient fighters as the Ants must serve to keep
away enemies from the slow and helpless Aphids; but to
what further extent the Ants actively protect their charges
is not so clear.

The most familiar traditional aspect of ant life, the
storing up of grain for a winter supply, is illustrated in

INSECT SOCIAL COMMUNITIES 81

the Harvester or Agricultural Ants, whose nests are con-
spicuous in open grassy places and especially in arid or
nearly desert regions. They bring into their nests great
quantities of grain and grass seeds, and have been even
credited with deliberate planting for harvest of certain
kinds of grass seed, of which they are very fond; this
last, however, is discredited by Wheeler.

The Ecitons, or Foraging Ants, are fierce predatory
insects, well known in West Africa and tropical America.
They are nomadic, having no fixed habitations, but travel
mostly by night in enormous armies which seek out and
destroy every living animal in their path. The approach
of these great columns strikes terror and confusion into
all the varied life of the tropical forests. Beast, bird and
man hasten to get out of their path. Dwellings are
promptly vacated on notice of their appearance, and they
swarm through the house, seek out every cranny and
crevice, attack and tear to pieces insects, mice, rats and
vermin of every kind, and retire, loaded with booty, to
their nests, which are mere temporary camps excavated
beneath stones or other convenient shelter.

They are blind or nearly so, and traveling chiefly by
night, are guided by their antennal sense, which, as in most
other ants, practically takes the place of sight in higher
animals. Travelers in the forest whose camps are in the
line of march of an army of Driver Ants find themselves
suddenly covered by swarms of big black insects, biting
fiercely at every unprotected spot, and have to run for
their lives, abandoning camp baggage and clothing for a
time to the mercies of their savage assailants. Their
household visitations are regarded as a blessing, for the
dwelling is clear of vermin, dead or alive, when they get
through with it, and a temporary eviction is a small price
for the owners to pay where vermin swarm as they do in
the tropics.

The Saiibas, or Leaf-cutting Ants, are among the most
remarkable of all the social insects. They are abundant

82 ZOOLOGY

in tropical America and species of this group are found as
far north as New Jersey. In South and Central America
they build enormous nests with vast ramifications of gal-
leries and passages which extend for many yards and are
even said to tunnel under considerable rivers. Their curi-
ous habit of cutting out little pieces of leaves and carrying
them to their nests was noticed by early explorers and is
referred to even in some of the Indian legends. But it
was long a mystery what they did with the leaves. Ants
generally are dependent for food upon other insects, ani-
mal matter or upon sweet juices which they obtain in
various ways. They do not usually eat ordinary vege-
tation, and while the Saiibas might be supposed an excep-
tion to the rule, there was no evidence that they ate the
leaf fragments which they so carefully conveyed to their
homes. Professor Bates, who saw their work in the Ama-
zon Valley, was of the opinion that they used the leaves
to thatch their galleries and protect them from the heavy
tropic rains. The true explanation was suggested in 1874
by Thomas Belt.

The leaves are used as manure in which they grow and
cultivate a peculiar species of fungus on which they feed.
Within the nests, several feet below the ground, they
excavate large cavities, often a foot in diameter, which are
veritable underground gardens, tended, weeded and
manned by different grades of workers. The little leaf
fragments are brought to these cavities, cut, crushed and
manipulated into small round pellets, and planted in the
surface of the garden, to serve as nutriment for the fungus
to grow upon. Under the care of the ants the fungus is
not allowed to produce spores, but only to grow in thread-
like filaments, from which clusters of transparent globules
bud off, these latter forming the food of the ants. All
other kinds of fungus growth are carfully kept down, and
the temperature and moisture of the fungus garden is
regulated by opening or closing the openings at the top
of the nest, which seem to be chiefly ventilation holes, the

INSECT SOCIAL COMMUNITIES 83

Ants issuing and returning by other openings more or less
distant.

"These insects," observes Wheeler, "in the fierce strug-
gle for existence everywhere apparent in the tropics, have
developed a complex group of instinctive activities which
enables them to draw upon an ever-present, inexhaustible
food supply through utilizing the foliage of plants as a
substratum for the cultivation of edible fungi. No won-
der, therefore, that, having emancipated themselves from
the precarious diet of other ants, which subsist on insects,
the sweet exudations of plants and excrement, the Attii
have become the dominant invertebrates of tropical
America."

The nests are guarded by large soldier-workers, with
massive heads and powerful jaws. Smaller workers of
several different sizes have assigned to them the various
tasks of collecting leaves, of excavating the tunnels and
galleries, of cultivating, manuring and weeding the fungus
and of feeding the young, helpless larvae, the nurse-girls
of the colony being the smallest and youngest of the work-
ers. Upon leaving the nest for the foundation of a new
colony, the female carries with her a small pellet of the
fungus, which is carefully tended and manured until the
new colony has become established.

The Saiiba Ants are not the only fungus-growing in-
sects. Among the Termites, which, altho not true Ants,
resemble them in appearance and social habits, there are
certain kinds that also cultivate a species of fungus which
they use for food. The worker sex, however, is said to
feed upon dead wood and to receive no share of the fungus
which it spends so much time in cultivating. Among the
wood-boring beetles the Ambrosia Beetles also cultivate
and feed upon certain kinds of fungus, growing it on the
walls of the galleries which they excavate.

The Honey Ants ('Myrmecocystus') are a unique group.
These curious little Ants store up honey like the Bees, but
in a very different way. Instead of building cells of wax,

84 ZOOLOGY

they store it up in the bodies of certain of the workers,
in which the abdomen becomes enormously distended, so
that they are veritable living casks. These individuals do
not leave the nests, but are fed by the active workers, and
when replete, hang from the roof of enlarged chambers
in the runways. In seasons of scarcity they are able in
turn to feed the rest of the community by the same method
of regurgitation. They inhabit the arid southwestern
Uhited States and were studied and described by Professor
McCook from the Garden of the Gods in Colorado. Lead-
ing a rather precarious existence in a region where food
is abundant only for a short season in the year, the advan-
tage of this habit can readily be seen, and there are certain
advantages about living casks in being more readily re-
moved from danger than the fixed storehouses of the Bees.

A curious development of the social life of Ants is seen
in the so-called Slave-making Ants. Two of these, the
Sanguinary Ant, or Red Slave-maker, 'Formica sanguinea,'
and the Amazon Ant, 'Polyergus,' are well known, and
their habits have been carefully studied, the most recent
studies and interpretation being by Wheeler. The San-
guinary Ant makes raids upon the nests of other ants, but
in particular upon the smaller brown species, 'Formica
fusca/ killing the workers, carrying off eggs and larvae to
its own nest. Most of the larvae are used for food, but a
part of them are reared and brought up in the nest of their
captors. They become loyal members of the new com-
munity and take part in the multifarious activities of the
nest, going out in search of food, caring for the eggs, feed-
ing the larvae, excavating or extending the nest and so on.
It does not appear that they take part in the raids on other
ant nests, but probably this is merely because such raids
are conducted by the larger and more powerful workers
only in any ant community.

The resemblance here to slave-making in the human
race is more superficial than real. Worker-ants are never
captured in these raids, and the larvae reared in the nest

INSECT SOCIAL COMMUNITIES 85

of the captors are not an unwilling and inferior race for-
cibly held in subjection and treated as an inferior caste.
The nest is rather to be considered as a mixed community,
in which the division of labor is based on the capabilities
of the individual, but not on his race. Nevertheless, if it
is considered that it is only the worker larvae of the
smaller species that are reared, and that they help to rear
and care for the young of an alien race instead of their
own, this slave-making does involve the exploiting of the
weaker for the benefit of the more powerful race.

In the Amazon Ant a further development of the slave-
making instinct appears, which may serve to show where
the weak point lies in this method of exploitation. In this
species the workers have become largely dependent upon
the captured race, not only for the care of the nest and
rearing of the young, but for food as well, so that they are
unable to feed or groom themselves. Under these condi-
tions the continuance of the Amazon Ant communities
obviously becomes dependent upon the prosperity and
abundance of colonies of the smaller species. The slave-
making race cannot prosper at the expense of the other
beyond a certain limit, and its relations tend to become
analogous to those of parasitic animals.

In several kinds of ants the female, instead of depending
upon her own progeny to start a new colony, may seek
out a small existing colony of her own or some other spe-
cies and persuade or compel the workers to adopt her.
This process has been carefully observed by Wheeler and
distinguished from the slave-making habits with which it
might readily be confused. Both result in mixed com-
munities in which the larger species is more or less de-
pendent upon the smaller in its household and personal
activities. But the slave-making results from the carrying
off of larvae from raided nests; the social parasitism from
the adoption by an ant community of a queen of alien race.
It is not wholly clear, in spite of the careful observations
of Wheeler and others, how the invading queen manages

86 ZOOLOGY

to overcome the strong instinct of antagonism in the work-
ers to an ant of another community or race. But this
parasitism is carried in some species so far that the invad-
ing race has no workers, only males and females, and is
wholly dependent upon its host for sustenance.

There is a great variety of parasitism, social and indi-
vidual, to be seen in ant communities, and the careful study
of its nature has thrown much light on the nature and
limits of the intelligence of these insects. There are sev-
eral kinds of smaller ants that live in mixed communities
with larger forms, but construct separate galleries opening
into the larger galleries of their hosts, but too small for
the larger ants to traverse. Among these some, like the
Thief Ant, 'Solenopsis,' prey upon the larvae and pupae of
the larger form, while others merely levy toll upon the
supplies brought in by the larger workers.

Again there are various insects of other orders, flies,
bugs and spiders, which make their homes in ant nests.
Some are harmless, or even beneficial in the life of the
community, but others are ravenous and destructive ene-
mies of the ants, preying upon the eggs or larvae, laying
their own eggs within the ant-larvae to develop at their
expense, and in various ways seriously interfering with the
prosperity of the nest. Yet the eggs and larvae of these
parasites are as carefully tended and reared by the ants
as their own, and the adults are evidently tolerated by the
workers, either because they are unobserved, or because
they are regarded as nest-mates, or for some other reason
still obscure.

CHAPTER VI

THE VERTEBRATES — I. FISH

The vertebrates, or backboned animals, including fish,
amphibia, reptiles, birds and mammals (with man), are
markedly differentiated in their plan of organization from
the radiates, mollusks or arthropods. This new plan of
organization, leading to a higher plane of development, has
made the vertebrate the dominant type of animal life, not
indeed in numbers of individuals or species, as some nat-
uralists would interpret dominance, but as individually
higher types, better fitted for success in the struggle for
existence. They have further opened the way, in the de-
velopment of man, for the inception of a new era, the
Psychozoic Era as it has been aptly called by Leconte, in
which intellect becomes the principal factor in the evolu-
tion of life, controlling its environment, guiding its devel-
opment, and leading to results which we can but dimly
foresee, even as to those immediately before us.

In a brief review of the plan of organization of the
vertebrates it will appear wherein these advantages lie.
In all vertebrates there is an internal skeleton, of which
the central feature is the backbone, originally developed
from the 'notochord/ a segmented strip of cartilage later
converted into bone, forming the nucleus of the spine.
This internal skeleton, as against the external skeleton of
most invertebrates, affords certain marked mechanical ad-
vantages in giving the muscles a better purchase and en-
abling them to control the action and movements of body
8?

88 ZOOLOGY

and limbs more powerfully. Now it is a fundamental fact
of mechanics that with every doubling of the dimensions
of a structure the relative strength of its materials is re-
duced by one-half. So that larger constructions, to per-
form what is relatively the same work, must be more mas-
sively proportioned, or made of stronger material than
smaller ones. This is equally true of animals. The larger
an animal is the more powerful and strongly constructed
rnust it be, in order to have the same amount of activity
and obtain its proportional amount of food. It is a com-
mon saying that if a flea were the size of an elephant he
could jump over the spire of the highest cathedral in
Europe. But any engineer can see the absurdity of this
statement. If a flea were the size of an elephant, he
would in fact be unable to lift his body off the ground.
His proportionate strength would be V4320 of what it is,
and in all probability would not hold his body together.
His apparent strength is merely due to his minute size.
If vertebrates and invertebrates of equal size be com-
pared the greater strength and activity of the vertebrate
is immediately perceived.

Now size is a very important factor in the dominance
of an animal, and the superior organization of the verte-
brates which has enabled them to attain much larger size
is in no small degree due to their having an internal skele-
ton. Many vertebrates have also developed for protection
an external skeleton of scales or plates, and the most
ancient of fossil vertebrates were well armored externally,
while the internal skeleton was still composed of cartilage
not yet hardened into bone.

The nervous system of vertebrates consists of a spinal
cord along the back just above the notochord, and a brain
developing at the front end of the notochord. The brain
is more concentrated into a single mass than in inverte-
brates, where its functions are partly distributed among
ganglia in different parts of the nervous cords. This nat-
urally makes for more centralized and better coi related

THE VERTEBRATES— I. FISH 89

control of the different parts and organs of the body, and
facilitates the development of intelligence and reasoning
powers. In the highest invertebrates there is a marvelous
development of accurately coordinated automatic action
and complexity of instinct, but they seem to be unable to
attain high intelligent or reasoning powers. In verte-
brates, while the instincts are less elaborate and complex,
the observer is impressed with the relatively intelligent
character of their activities, with their ability to respond
to new sensations, and accommodate themselves to new
conditions of life. This is to be connected with their more
concentrated brain, and from the first the nervous system
appears to have been more concentrated in vertebrates
than in any of the invertebrate groups.

All vertebrates breathed primarily by gills, the water
which aerated the gills entering through the mouth and
making its exit through gill-slits on each side of the throat.
Fishes and tadpoles still breathe this way, but land ani-
mals, have become adapted to breathing air by means of
the lungs. Rudimentary lungs are present in many primi-
tive fishes, serving to assist the gills in aerating the blood
when, as in stagnant ponds, the supply of oxygen in the
water was not sufficient for the needs of the fish. In the
more typical modern fish this rudimentary lung has been
converted into the so-called swim-bladder, serving to ad-
just the weight of the body to the water around by com-
pressing or expanding the air contained in it, and perhaps
for adjusting the amount and quality of air in the blood.
It is interesting to observe that the embryos of all land
mammals, including man, pass through a stage in which
they possess gill-slits, altho these serve no purpose in the
life of the young animal.

All vertebrates except certain very lowly types possess
paired appendages — fins, limbs or wings. These consist
always of two pairs, never more, and originate in an en-
tirely different way from those of arthropods, as folds of
skin along the side of the body, becoming concentrated into

9o ZOOLOGY

fins or paddles and thence converted into limbs. In birds,
bats and pterodactyls the fore limbs are converted into
wings.

The alimentary or digestive system consists at first of
a long straight canal near the under side of the body and
is elaborated into a very complex affair by the develop-
ment of various glands to assist in digestion, and by the
lengthening and coiling of the alimentary canal. The cir-
culatory system is much more elaborated than in the lower
animals and progressively so in the higher vertebrates.
A marked difference from insects lies in the fact that air
is conveyed from the lungs or gills to the tissues by me-
dium of the blood corpuscles, whereas in insects the air
reaches the tissues of all parts of the body directly through
the tracheae. The circulation of the blood is thus a much
more important function of the life of vertebrates than of
insects.

In the development of the skeleton it is to be noted. that
the spinal cord soon becomes arched over by segments of
bone and the brain enclosed in a bony capsule; that the
under side of the body is supported by arches of carti-
lage from each segment of the notochord, which are con-
verted into bony ribs ; that the gill-arches are also sup-
ported by bony arches, of which the front pair is later
converted into a part of the lower jaw; that the teeth de-
velop originally as scales on the skin of the mouth ; that
the segmented limb-bones retain even among mammals
many suggestions of their former fin-ray construction.
Various additional bones are formed in the skin of the
head which coalesce with the more internal bones of brain
capsule and jaw to form the solid skull of the higher ver-
tebrates. In fishes the various bones of the head are more
or less separate, as also in the young of higher animals.

The eyes are in general highly developed and are the
most important of the sense organs ; the hearing organs
are also very elaborate and complicated. The sense of

«-2*

92 ZOOLOGY

smell, altho usually well developed, has by no means the
importance that it reaches among the higher insects.

The vertebrates were, at first and for a long time,
adapted to live in water. In reviewing the geological his-
tory of the different groups, the successive stages of their
invasion of the land and adaptation to terrestrial life will
appear. Having once become well adapted to air-breath-
ing and the more active and varied life of' the dry land,
tfie vertebrates were enabled, through their better plan of
organization, to attain larger size and higher intelligence
than the insects, spiders and land snails which were their
predecessors as land animals. Their internal instead of
external skeleton, their more concentrated nervous system,
and it might be added, their more concentrated breathing
system (for the tracheae of insects may be regarded as
lungs distributed throughout the whole body) were prob-
ably the principal points of advantage.

Vertebrates are much less ancient than the invertebrate
groups. At the beginning of recorded geological history
the several groups of invertebrates already were well
specialized. They must have had a long previous era of
evolution of which there is no record, partly because the
most ancient rocks containing it are so altered by crystal-
lization that their fossils have been destroyed, partly be-
cause many or all of these most ancient animals possessed
no hard points which could be preserved as fossils. But
the earliest vertebrates, appearing about the middle of the
Paleozoic era, are only beginning to assume the distinc-
tive characters of vertebrata, so far as can be judged from
the fossil remains. They were in the dawn of their de-
velopment; and as they are followed upward in the geo-
logic column, they are found putting on more and more of
the characteristic features of vertebrata, and finally, at
the end of the long Paleozoic era, becoming adapted, at
first very imperfectly, for active land life.

The earliest vertebrates had a notochord but no bony
internal skeleton; but some of them had a very complete

THE VERTEBRATES— I. FISH 93

bony armor. The notochord was gradually replaced by a
true backbone in the land vertebrates, but more or less of
it still remains in modern fishes, and it was not until the
beginning of the Age of Reptiles that it disappeared among
the land vertebrates.

Among these most ancient of vertebrates may be men-
tioned two groups, the Ostracoderms, covered with bony
armor (or sometimes with only the head armored), first
found in the Old Red Sandstones of Scotland, of whose
"griesly fisch in the laithly flood" Hugh Miller has given
such lively and fascinating descriptions. These animals
at first glance resemble crustaceans or scorpions, but they
are considered as vertebrata, altho not true fishes. True
fishes appear a little later, in the primitive sharks and re-
lated types which are preserved, sometimes in great per-
fection, in the Devonian shales of Ohio and elsewhere.

In the sharks and rays the internal skeleton is still com-
posed of cartilage, as it was in the primitive ancestral ver-
tebrates. The gill-slits are also of a very ancient type.
They consist of a number of separate slots along the outer
surface of the side just behind the head. In all the higher
fishes they are covered by a flap of bone and skin called
the operculum, or gill-cover.

To the bather in tropical waters, to the shipwrecked sea-
man clinging to a raft or afloat in a leaky overloaded boat,
the appearance of sharks is the danger most to be dreaded.
Swift, powerful and voracious, many of them huge in size,
they are the terror of the warmer seas. Indiscriminate in
their appetite, they are fortunately less dexterous than
many other fish in seizing their prey at the surface, and
may often be frightened away by splashing and disturb-
ance of the water, which their low intelligence does not
allow them to understand. It is probable indeed that the
number of swimmers actually devoured by sharks is by no
means in proportion to their reputation.

The largest and most voracious of the man-eating sharks
is the great white shark, found in all tropical seas, but for-

94 ZOOLOGY

tunately not very common. This species reaches a length
of 30 feet, and is quite capable of swallowing a man whole.
It is, according to Linnaeus, the 'great fish' which swal-
lowed Jonah. "Jonam Prophetum ut veteris Herculem
trinoctem, in hujus ventriculo tridui spateo bassisse, vero-
simile est." Gesner relates that the bodies of men
have been found entire in sharks, on one occasion, at Mar-
seilles, a man in complete armor ; and over a hundred simi-
lar cases "have since been recorded."

Huge as is the living white shark, it was far surpassed
by some of its extinct relatives. The fossil shark teeth
common in the phosphate beds of South Carolina and in
other Tertiary and Pleistocene formations are sometimes
six inches long and five wide, three times as large as in
the largest white sharks, and the animal, if of proportion-
ate size, must have attained a length of ninety feet, equal-
ing or exceeding the largest whales. It is possible that
sharks of this size still exist, altho they have never been
reported on good authority, for teeth of similar dimensions
have been obtained in deep-sea dredging. A restoration
of the jaws of this gigantic extinct shark with the (origi-
nal) teeth all in position has recently been placed on exhi-
bition in the Natural History Museum in New York.
The gape of the jaws is nearly seven feet, so that this
monster could almost have swallowed a small vessel, crew
and all, and the traditional Jonah could easily have walked
down his throat if opened for the purpose.

Closely related to the white shark are the mackerel
sharks, porbeagles and salmon-sharks, not attaining such
giant size, but equally swift and voracious. The high tri-
angular back-fin and the mackerel-like tail are charac-
teristic features of this group. The basking shark is the
largest of the family and the largest of all true fishes,
attaining a length of thirty-six feet and an enormous bulk.
Unlike its relatives, it is a dull, sluggish animal, and does
not pursue large prey.

The blue sharks, tiger-sharks and cub or harbor sharks

THE VERTEBRATES— I. FISH 95

are much more common and familiar, than the white shark
and its allies, and almost equal it in swiftness and feroc-
ity, and sometimes in gigantic size. The dorsal fin is
not so high and triangular, and the lobes of the tail are
very unequal, the upper lobe projecting far backward,
while the lower lobe is small. The blue shark, so com-
monly seen following ships, and the cub-shark, common
around the waters of tropical harbors, are usually credited
with the dangerous ferocity of the white shark, which they
hardly deserve.

The rays and skates are related to the true sharks, but
have the body flattened out and the pectoral fins extended
in a thin, continuous flap along the sides, so that the ani-
mal has the shape of a flounder or halibut. They are bot-
tom feeders, living on shells and crustaceans, and harm-
less, except for the sting rays, which can deliver a severe
wound by a slash of the spiny tail, and the torpedoes,
which have an electric organ capable of giving a severe be-
numbing shock to an enemy. The sea-devils are gigantic
rays, the great wing-like fins expanding twenty feet.

Most modern fishes have a bony internal skeleton, and
in various respects are higher types than the sharks. There
are various partly intermediate forms between sharks and
true bony fishes, but their relationships need not be con-
sidered here.

The perch and bass are usually considered the most typ-
ical of this group, and from this type as a center they
vary into an endless diversity of form structure and habit.
Most of them are marine, but many inhabit fresh-water
lakes, rivers and brooks. In the ocean they are abundant
everywhere, from shore to far out at sea, from the surface
to great depths. Nowhere are they so varied or brightly
colored as around the coral reefs of tropical seas ; but they
are equally abundant in the colder waters of the northern
oceans. They form an important part of the food of all
maritime peoples; the value of the herring fishery alone
is over thirty-seven million dollars annually.

96 ZOOLOGY

The most ancient type of true bony fish are the soft-
finned fishes, allies of the herring and the trout. The her-
ring, running in immense "schools" in all the northern
seas, is more used for food than any other fish, and "its
spawning and feeding grounds have determined the loca-
tion of cities." Closely allied to the herring is the shad,
highly prized as a food fish in the United States, and the
menhaden, caught chiefly for its oil and as a manure for
fields. The much larger tarpon of the South Atlantic is
a favorite game-fish, reaching a length of six feet or more
and affording exciting sport to the angler. Extinct allies
of the tarpon in the Cretaceous seas (Portheus) reached
a length of twelve feet.

The trout and salmon live partly or wholly in fresh wa-
ter, the salmon ascending rivers from the sea to spawn,
while the trout live entirely in fresh water, running
streams or lakes, and the whitefish inhabit the great fresh-
water lakes of North America. The Pacific salmon en-
ters the rivers only for spawning, takes no food during
its desperate struggle up to the headwaters of the stream,
and dies when the spawning is completed, the young re-
turning to the sea at the next high water. The Atlantic
and European salmon, much more closely related to the
trout, spend a much larger part of their lives in fresh
water, while on the other hand several species of trout de-
scend for a time to the sea, and others live partly or wholly
in fresh-water lakes and ponds. Salmon and trout are
the chief of game fish. In beauty and variety of color,
in delicacy of flavor, in fighting qualities and in wariness,
they rank with any fish.

If the trout and salmon are the favorites of the fresh-
water fisherman, eels are perhaps the most heartily dis-
liked. Their long, snaky form, ugly color, slimy skin, and
their unpleasant addiction to "swallowing the bait" would
be causes enough, but in addition they are one of the worst
enemies of the game fishes. The spawning of the fresh-
water eel was long a mystery, only very recently solved.

THE VERTEBRATES— I. FISH

97

The truth is that they descend to the sea to spawn, revers-
ing the habits of the salmon.

The carp family includes a great many fresh-water fish,
mostly small and less active than the salmon group. Both
carp and salmon families are found only in the northern
temperate regions. The carp and chub, dace and roach,
minnow and shiner, are familiar in our brooks and streams,
none of them gamy, none very good eating, but passable

Fig. 18 — Herring and Cod.
The two greatest food fishes of the world. (Jordan.)

in absence of better fish. The carp and the nearly related
goldfish are natives of China, domesticated there for cen-
turies and introduced into Europe about 300 years ago.

Another familiar group of fresh-water fishes is the cat-
fish family. They derive their name from the barbels or
feelers around the mouth, which suggest the "smellers" of
a cat. They are not scaly, but often head and parts of
body are armored with bony plates. Their especial home
is in South America, but they are common also in the

98 ZOOLOGY

northern continents and a few in Africa. They are all
carnivorous gamy fish, fair to good eating, and most of
them are found in river channels or muddy streams. Simi-
lar in habits but more graceful in form are the pike and

Fig. 19 — Speckled Trout and Yellow Perch.
These two are the most familiar of fresh-water fish. (Jordan.)

muskallonge, the first living in fresh-water streams of all
the northern continents, the second in the Great Lakes.

In the south temperate zone, where there are no true
trout, their place is taken by a distinct group of fishes
of the same habits. They are the "trout" of New Zealand,
Australia, Tasmania, Patagonia and the Falkland Islands,

THE VERTEBRATES— I. FISH 99

and of South Africa. It has been supposed that these
fresh-water fish, living in the isolated continents of the
south, and unknown in equatorial or northern regions,
must have spread from one to another region by way of
an antarctic continent now submerged. It has recently
been found, however, that these fish are able to live in salt
water as well as fresh, so that they may have been dis-
tributed by sea.

The largest and most typical of the great groups of
bony fishes are the spiny-rayed fish, typified by the perch
and mackerel. Numerous fresh-water and more abun-
dant marine fish are included in this order ; only a few of
the best-known kinds can be mentioned here.

The mackerel of the North Atlantic runs in great
schools, estimated to contain many millions of fish, vary-
ing a great deal from year to year in their course. It
furnishes one of the principal fisheries of New England.
Larger relatives of the mackerel are the tunny, albacore
and bonito of the warmer seas, and the Spanish mackerel
of the West Indies. All these are swift, graceful, hand-
some fishes. The mackerel are preyed upon by their
larger relative, the swordfish, which follows the schools to
the New England coasts. Its presence is a sign that there
are mackerel about. It is one of the swiftest of fishes; the
graceful, compact body, forked tail and pointed head with
long, sword-like upper jaw are all peculiarly fitted for
speed. The swordfish frequently attacks ships or boats,
driving its sword through a heavy plank without difficulty.

The bluefish is another well-known predaceous fish of
the North Atlantic. It is said to be the most destructive
of all fishes in the waters it inhabits, pursuing the schools
of smaller fish and killing far more than it requires for
food. Professor Baird has estimated that during their
stay on the New England coast the bluefish destroy up-
ward of twelve hundred million million of smaller fish.

The order of perch-like fish includes a great variety
of familiar fishes, fresh-water and marine — the perch8

100

ZOOLOGY

bass, darters and sunfish of the still streams and lakes of
the north temperate zone; the sea bass and their relatives
which in Australia, South America and South Africa have
invaded the rivers and take the place and name of perch;
the bright-colored groups of tropical seas. The parrot-
fish, damsel-fish and angel-fish of the coral reefs, the

Fig. 20 — Mackerel and Flounder.
Illustrating swift-swimming and bottom-feeding types of adapta-
tion among sea-fish. (Jordan.)

sculpins and gurnards are more or less nearly related. The
flat fishes are a curious offshoot of the spring-rayed fishes.
The body is very deep and narrow, but the fish swims on
its side, one eye being twisted around from its normal
position so that both of the eyes are on the side which
lies uppermost. This side is also darker colored than the

THE VERTEBRATES— I. FISH 101

under side. In some flatfish it is the right, in others the
left side which lies uppermost and shows the eyes and
darker coloration. The flounders, soles, halibut, turbot
and plaice are the best known of the flatfish. All are
excellent food fishes.
The codfish family — codfish, pollock, haddock and va-

Fig. 21 — The Butterfly-fish.
One of the gorgeously colored fishes which live among the coral
reefs. (Jordan.)

rious smaller species — are more remotely related to the
spiny finned fishes, and are of great importance as a food
fish. For four centuries the Banks of Newfoundland
have been the chief center of the cod fishery. Among the
fishing vessels all nations are represented, and in succes-
sion have come the Basque, Dutch, English, American and
Scandinavian fishermen.

CHAPTER VII

THE VERTEBRATES — II. AMPHIBIA AND REPTILES

The Frogs, Toads, Efts and Salamanders are interme-
diate between aquatic and terrestrial vertebrates, between
fishes and reptiles. In early life they are tadpoles, living
in water, breathing by gills, having no true limbs, but a
fringe of fin like the median fins of many fishes. Later
they undergo a metamorphosis, bud out true limbs with
feet, lose their gills and develop lungs, and become
adapted to live on land. They are to some extent inter-
mediate between fishes and reptiles, but are in fact much
closer to reptiles if we compare the adult animals. Altho
fish-like in their early development, there is a wide gap
between them and any true fishes, living or extinct.

There are two living groups of amphibians, the frogs
and toads, tailless ; and the efts and salamanders with long,
heavy tails. The efts or newts and salamanders look very
like lizards, but may be distinguished by their broad,
flat heads. They frequent damp woods and borders of
ponds, and may often be found by overturning stones or
logs in such places. Most of them are quite small, but the
giant salamander of Japan ('Cryptobranchus') reaches a
length of five feet, and the closely related hellbender is
sometimes eighteen inches long. The smaller efts are
common in all the northern continents, and a few are
found in North Africa and along the Andes Mountains
as far south as Argentina. Some of the tailed amphib-
ians retain their gills throughout their life, especially
if the conditions favor their continued aquatic life.

ill 111

.11;:,.

Ill !*

104 ZOOLOGY

The toads and frogs are familiar to every one and are
found in all parts of world, except in some of the oceanic
islands. Toads are harmless creatures, helpful to the
gardener from the quantities of insects they consume,
many of them curiously interesting in their mating and .
egg-laying habits, and it is hard to see why they should
be regarded with such general aversion. Like most Am-
phibians, there is a poisonous secretion in the skin which
protects them from the attacks of more active animals,
but this is not exuded from the surface save in extremity,
and they can be handled with perfect safety, the poi-
son acting only internally. There is no ground for the
notion that warts on the skin are the result of handling
toads. A curious myth found in early books on natural
history and embalmed by Shakespeare in a quotation
familiar to all, credits the toad with bearing a "precious
jewel in his head."

The frogs, less poisonous than toads, are protected by
their greater activity and more amphibious habits. The
tree-toads are protected by their genius at concealment,
and altho every one has heard their loud trilling, it
is surprising how few persons have seen the little green
chap with sucker-like disks on the tips of the toes who
is responsible for it.

The modern amphibians are diminutive and specialized
descendants of what was once a numerous and important
race. The Primitive Amphibians or Armored Amphib-
ians of the Coal Period were the first of land vertebrates,
and were the dominant type of land animals until the ap-
pearance of the reptiles. These Armored Amphibians
were much like salamanders in appearance, but the top
of the head was solidly roofed over by bone and the under
side of the body covered with scaly armor. Some of them
were gigantic as compared with their modern descend-
ants, ten or twelve feet in length, with skulls two feet
long and a foot and a half wide. From some of these

Wind-riven Foliage of Pike's Peak. Tropical Forest Showing
Lianas.

THE VERTEBRATES— II. REPTILES 105

ancient amphibians were probably descended the reptiles,
birds and mammals of later geologic ages.

The class of reptiles includes several very diverse kinds
of animals — the snakes, lizards, crocodiles and turtles.
Superficially they have not much in common except for
the scaly skin, and that they (mostly) lay eggs and (all)

ear

Fig. 23 — An Australian Tree Frog.
Note the adhesive discs of the toes and the inflated vocal sac.

breathe by lungs throughout their lives. The construction
of the skeleton and the various details of internal organi-
zation show that they are in fact related to each other,
tho not very closely, and geological history shows that they
art the scattered and specialized survivors of a class of
vertebrates which for countless centuries was the domi-
nant type of land animal. The Age of Reptiles is esti-
mated to have endured for some nine millions of years;

io6 ZOOLOGY

the Age of Mammals, which followed it and culminated
in the appearance of man, for three millions of years.
Compared with these vast periods the duration of historic
time shrinks into insignificance.

The reptiles evolved from the Primitive Amphibians of
the Coal Period, and the earliest reptiles are with diffi-
culty distinguished from them. But they were more pro-
gressive in adapting themselves to the active and varied
life of the land, and developed a higher and more active
organization. The most important and interesting of
these ancient reptiles were the Dinosaurs, adapted to live
on dry land, and taking the place in nature that v/as sub-
sequently to be taken by land mammals, the ordinary
quadrupeds of the present day. But in addition to these,
there were reptiles adapted to flying and others which re-
invaded the ocean and became adapted to swimming, altho
still keeping their air-breathing habit.

The oldest reptiles, appearing at the latter end of the
Coal Period, were clumsy, heavy-bodied beasts, with short,
crooked legs like crocodiles or turtles, some of them car-
nivorous, others herbivorous. The most singular of these
ancient reptiles were the Pelycosaurians, or Fin-backed
Reptiles, with an enormous rigid bony fin on the back, the
purpose of which, unless for ornament, is a standing puz-
zle to zoologists.

The Dinosaurs are perhaps most obviously distin-
guished as long-legged reptiles, for in all of them the legs
are long and straight as in modern land quadrupeds, in-
stead of short and crooked as in modern reptiles. They
were the characteristic land animals during the whole of
the Age of Reptiles, comprising the Triassic, Jurassic and
Cretaceous Periods, and many of them reached a gigantic
size, rivaling the largest of living animals. Besides these
gigantic forms, there were numerous smaller, lighter,
more agile kinds, many of them known only by their foot-
prints preserved in the ancient tidal flats of the Connecti-
cut Valley and elsewhere. And there is reason to believe

P-i 03

108 ZOOLOGY

that there were multitudes of small upland dinosaurs of
which nothing is known, because they never frequented
the river-bottoms, swamps and seashores where sediments
were being deposited that might preserve their remains
to the present day. Only in their modified descendants,
readapted to swamp or riverside life, can be perceived the
traces remaining of what must have originally been an
adaptation to upland life.

The hugest of the Dinosaurs were the Brontosaurus and
Diplodocus, reaching a length of sixty to eighty feet and
a mass of over thirty tons in weight. These were probably
amphibious animals, adapted to wade in water from twenty
to fifty feet in depth. They had a massive elephantine
body, supported on four straight, rather long legs, with
feet very like those of elephants, except for large, blunt
claws, one on the fore-foot, three on the hind-foot, which
may have served to anchor the foot in slippery mud. The
neck was long and flexible, enabling the animal to wade
to considerable depth while keeping his head above water ;
the tail long, heavy and massive as in most reptiles. The
skin was not scaly, but naked, thick and heavy like that
of a whale. The head is very small in proportion, the
teeth adapted to tearing off soft water plants or other
such material, but not to chew the food nor to attack
other animals. The brain is extremely small, and was
of low organization even for a reptile, the great mass of
the nervous system being the nerves and ganglia of the
spinal cord. From this it is seen that the animal was slow
and unintelligent, the actions chiefly reflex, and the Bron-
tosaurus may be regarded as little more than a huge autom-
aton, a vast storehouse of animal matter, with but little
intelligence, and its movements mostly directed by reflex
action. Through its aquatic life, the water buoying up
most of its enormous weight, it was able to attain a size
comparable only with the modern whales and sharks. But
its movements must have been slow and clumsy, and on
land it would be utterly helpless ; it was protected from its

THE VERTEBRATES— II. REPTILES 109

chief enemies, the carnivorous dinosaurs, by being able to
wade to a depth beyond their reach.

Skeletons or casts of skeletons of some of these gigantic
amphibious dinosaurs have recently been mounted in sev-
eral of the larger museums in America and Europe and
are among the most impressive records of the past history
of the world.

The carnivorous dinosaurs were very different in ap-
pearance and habits. They were biped reptiles, with long
hind limbs and bird-like feet, small fore limbs, large, sharp
claws, short neck and large head with sharp-pointed, saw-
edged teeth, and a long, lizard-like tail. Tracks of this type
of dinosaur are abundant on the Connecticut sandstones
and show that they usually walked or ran on the hind-
limbs, seldom touching either fore-limbs or tail. These
dinosaurs lived throughout the Age of Reptiles, both small,
agile species and large, powerful ones. The most gigantic
was the Tyrannosaurus of the late Cretaceous, forty feet
in length, with a skull five feet long and teeth projecting
four to six inches from their sockets. This animal must
have nearly equaled an elephant in bulk and was adapted
to prey upon the huge armored dinosaurs.

Other types of huge dinosaurs discovered in recent years
are the armored Stegosaurs, covered with bony plates and
spines, the great horned Ceratopsians with enormous
skulls defended by long, sharp horns, and the duck-billed
Trachodon and Iguanodon, unarmored, and with broad,
horny, duck-like bill. These animals were all herbivorous,
and except the Stegosaurs, had a fairly effective battery
of grinding teeth. They reached a length of twenty to
thirty feet and a bulk comparable to a hippopotamus or an
elephant. They also had numerous smaller relatives, more
agile and apparently more upland in their habitat, since
their skeletons are rarely found complete in the ancient
sediments of the river valleys and marshes of the Age of
Reptiles. Mostly they are known to science only by the

no ZOOLOGY

scattered bones and fragments brought down by the rivers
from higher levels.

The Flying Reptiles, or 'Pterodactyls,' were contem-
poraries of the Dinosaurs and equally remarkable, altho
less gigantic in size. These "dragons of the prime" had the
fore limbs converted into bat-like wings by the extension
of the little finger into a long, slender-jointed rod support-
ing a membrane wing like that of bats. The tail is rudi-

Fig. 25 — Pterodactyl or Flying Reptile.
Jurassic Period, Age of Reptiles. Note the greatly elongated fifth
digit of the fore foot, from which the wing membrane
stretches back to the hind foot and body. (Zittel.)

mentary or converted into a long steering blade, and the
skeleton throughout is very light and fragile, the bones
being hollow and pneumatic (filled with air) as they are
in birds. Most of the Pterodactyls were small, from six
inches to three feet expanse of wing, but in the late Cre-
taceous appeared large forms (Pteranodon), some twenty
feet from tip to tip of the wings, with large, straight, tooth-
less beaks, adapted apparently to spearing fish. The Pter-

THE VERTEBRATES— II. REPTILES in

anodon skeletons are found in marine formations deposited
far out at sea, while the small Pterodactyls, with shorter
wings, lived near the land. All of them were apparently
adapted for soaring rather than fluttering, and they may
be regarded as nature's nearest approach to a modern
aeroplane.

In the rivers and swamps of the Age of Reptiles might
be found crocodiles and turtles not very unlike those of
the present day, and a variety of extinct reptiles more or
less resembling them. In the seas lived several kinds of
marine reptiles, some of gigantic size. These, like the
cetaceans, seals and sirenians of the present day, were de-
rived from terrestrial ancestors, but had re-invaded the
sea, where they competed to advantage with the finny au-
tochthones by reason of their superior organization and
air-breathing habit.

The Plesiosaurs were long-necked, with compact bodies
and long, turtle-like flippers. The Ichthyosaurs were very
fish-like in outward appearance, with short necks, long,
slender jaws and shark-like tail, and were evidently
adapted to swift swimming like the mackerel-shark or the
dolphin. The Mosasaurs were more nearly related to the
lizards, but with flipper-like feet, large heads, with power-
ful jaws and sharp, stout teeth and long, compressed tails.
Some of the Mosasaurs and Plesiosaurs reached a length
of forty feet; the Ichthyosaurs were somewhat smaller.
All these great marine reptiles had become extinct by the
end of the Cretaceous Period, and their place in the world
was taken by marine mammals, ancestors of the Cetaceans
of our modern seas.

The world must have appeared strange from a modern
viewpoint during the Age of Reptiles. The imagination
must picture dry land and swamps populated by long-
legged reptiles, many of them fantastic and bizarre in ap-
pearance and all utterly unlike any living animals. The
vegetation would be less strange, but its tropical aspect

ii2 ZOOLOGY

and the absence of many of the more abundant higher
types of plants could hardly fail to impress the observer.

In place of birds were the Pterodactyls, soaring through
the air or hanging bat-like from trees or projecting
rocks. Along the seashore we might find many familiar
invertebrates, corals, starfish, sea urchins, crustaceans
and mollusks, and with them swarms of nautilus-like
ammonites and squid-like belemnites. Along the shores
and far out at sea, besides the numerous types of
fishes more or less like those of the present day, would be
found numbers of the huge voracious marine reptiles,
Plesiosaurs and Ichthyosaurs and (in the Cretaceous Pe-
riod) Mosasaurs, rulers of the deep, as the Cetaceans are
to-day.

The keynote of the Age of Reptiles, as compared with
the world of to-day, was the dominance of brute force.
The varied types of reptilia which ruled land and swamp,
sea and air were but little inferior in size and not greatly
inferior in mechanical organization, in strength and speed
to the higher animals which have taken their place. But
they were notably inferior in type of brain, with the intel-
ligence, adaptability and agility which it entails. Their
disappearance at the end of the Cretaceous Period is to be
ascribed partly to their being unable to adapt themselves
to changed conditions of life brought about by changes in
climate and geography of the world which they inhabited,
partly to the competition of the more intelligent and adapt-
able mammals and birds that were being evolved to com-
pete with them. There may have been other important
factors in causing their extinction ; several have been sug-
gested, many more might be suggested. But these are
known causes and must have played an important part in
the process; the others are mostly guesswork.

At the end of the Age of Reptiles there were a few sur-
viving groups which have persisted to the present day with
but little change. They were the turtles, crocodiles, liz-
ards and snakes, which on account of their habits and

THE VERTEBRATES— II. REPTILES 113

environment came less directly into competition with the
higher quadrupeds and birds or whose surroundings were
not altered by changes jin geography and climate. These
are the reptiles of to-day, a small and despised remnant
of a class which ruled the world for millions of years, and
for gigantic and formidable beasts has hardly since been
equaled.

The Turtles and Tortoises, 'Chelonia,' form a well-
armored group. The slow-moving tortoise is one of the
most thoroly protected of four-footed animals. Give him
a chance to withdraw his head, legs and tail within his
shell and close the lids, and no enemy can molest him
unless it be large and powerful enough to crush his whole
shell between its jaws. He lives upon snails, slugs, cater-
pillars, earthworms, etc., with a considerable addition of
vegetable food, usually hibernates in winter, and continues
his leisurely, untroubled existence for a long period of
years, perhaps even for centuries. It is only in his younger
days that he has much to fear from enemies. But the eggs
and young are toothsome morsels for carnivorous animals,
and in spite of the care with which the mother conceals
her eggs in the sand, burying them and effacing all marks
which might serve as guide to their location, probably very
few survive to be adult.

Land tortoises are found everywhere except in the Aus-
tralian region and are found on several isolated oceanic
islands, where, unmolested by higher quadrupeds, they are
very abundant and reach large size. Their aquatic rela-
tives, to which the name "turtle" is usually restricted, are
of several different groups similar in general appearance,
but not very closely related. They are generally more
active, less completely protected by shell, and with the feet
more or less completely converted into flippers for swim-
ming.

The pond-tortoises, or marsh-turtles. ^Terrapins), are
nearest to the true land tortoises, but have a flatter shell.
One of the prettiest among them is the Painted Terrapin

ii4 ZOOLOGY

(Chrysemys), with its handsome pattern of red and yellow
on a background of dull greenish black, but most of them
are dull colored. The Diamond-back Terrapin, noted as
the finest of all edible turtles, frequents the salt marshes
of the Atlantic coast, especially in the Southern States,
but is rapidly becoming scarce except where artificially
protected. The snapping turtles and mud turtles are
more aquatic and less completely protected by bony shell.
The sea turtles are wholly marine, mostly confined to
tropical seas and valued not only as food but for the tor-
toise shell manufactured from the outer layer of the cara-
pace. The largest of these marine turtles is the green
turtle (Chelone), inevitably connected, in song and story,
with aldermanic banquets and other such civic functions.
A near relative is the hawksbill turtle, the chief source of
the tortoise shell of commerce.

The Side-necked Turtles, abundant in the rivers of all
the southern continents, are rather distantly related to
those we have mentioned. Altho much alike superficially,
the construction of the carapace is different, and in with-
drawing the head into the shell they bend the neck side-
ways, while the others bend it vertically in an S-shaped
curve. Vast numbers of these turtles live in the South
American rivers.

The soft-shelled river turtles (Trionyx) of the northern
continents on the one hand, and the marine leathery turtles
on the other, are ancient offshoots of the main chelonian
stock which have endured with little change since the Rep-
tilian Age.

Like the turtles, the crocodiles are a race of ancient
lineage. During the Age of Reptiles they infested both
seas and rivers in all parts of the world. Since then their
range has been gradually restricted. The marine forms
long ago became extinct; the river crocodiles have disap-
peared from most temperate regions and are common only
in tropical or subtropical rivers. The living species are
grouped as alligators, crocodiles and gavials, differing in

THE VERTEBRATES— II. REPTILES 115

the width of the skull and to some extent in their food
habits. The narrow-snouted gavials of the East Indies
feed chiefly upon fish; the broad-headed alligators (chiefly
new-world) and the crocodiles (chiefly old-world), with
heads of medium width and muzzles notched at the sides
near the front to receive a large tooth in the lower jaw, lie
in wait for land animals which come down to the rivers to

Fig. 26 — The Hawksbill Turtle. (Gadow.)

drink or attempt to cross. These also live partly on fish.
They are said to dig burrows in the banks of the rivers
where they dwell, and like turtles they lay their eggs in a
nest in the dry sand or earth of the river bank, usually
covering them up and leaving them to hatch by the heat
of the sun.

The crocodile, with its covering of armor scales, its
powerful jaws and tail, is still formidable in modern tropi-

n6 ZOOLOGY

cal rivers, and to primitive man, armed only with spears
and arrows, it must have been almost unassailable. One
cannot wonder at the superstitious respect in which it was
held in ancient Egypt. The caimans of South America
are closely related to the alligators.

In contrast with the slow-moving armored turtles and
crocodiles the lizards are mostly quick, active, small in
size and unprotected by armor, the skin covered with
small horny scales. They are wholly terrestrial, most
abundant in arid or desert regions, but they live almost
everywhere except in the cold temperate and arctic zones.
Their small size, quick movements, dexterity in hiding, and
ability to live in rocky and desert places, enable them to
compete very well with small mammals, and they are a
numerous and varied race. For the most part they live
upon insects and are very adept in catching them. A few
lizards attain a considerable size. The monitors of Africa,
the East Indies and Australia reach a length of six or
seven feet; in the tropical parts of the New World the
Iguanas attain an equal size.

Among the smaller kinds, the geckos, skinks and true
lizards are most familiar. Professor Gadow describes the
habits of the Gecko as follows : "In their native haunts
they are very regular in their habits. Favorite resorts of
theirs are old olive trees or oak trees, the rough and
cracked bark of which affords excellent places for hiding
in. Hollow trees are of course preferred. Not a single
specimen is seen during the early hours of the morning or
in the forenoon, but when the sun has become broiling hot
and our own shadow passes over the stem of a tree we be-
come aware of flitting little shadows which jerk over its
surface. These are Geckos which had been basking, mo-
tionless, very dark gray, almost blackish, just like the
color of the gray bark upon which the last season's wet
moss has been scorched to a black cinder. It is difficult
to espy a Gecko while it is glued on to such a tree. Only
the little beady eyes betray it, watching you carefully.

THE VERTEBRATES— II. REPTILES 117

Nothing appears more easy than to catch that motionless
thing. You put out your hand and it is gone ; like a flash
it has moved a foot higher up or down, to the right or to
the left, just where you least expected it to go, and there
it clings motionless as before. It does not seem to run ; it
glides along, dodging over to the other side of the stem
and back again. There is system in its motions, since, tak-
ing a last leisurely look around, it gently disappears in a
rent or hole. Toward the evening, or when the shadows
become longer, the Geckos become lively. One after an-
other appears on the surface, upon the tree or at the en-
trance of the cave, and they all move about in their peculiar
rushing jerks. Spiders, flies, mosquitoes, moths form the
principal diet, and the hunting goes on well into the night.
Where a gecko has been seen once it is sure to reappear
the next day at the same hour. Those which take up their
abode inside a house become almost domesticated. They
are strange sights when hunting for flies, running up and
down the papered walls; but we fairly gasp when they
come to the upper corner, calmly bend over and with the
next jerk slide along the whitewashed ceiling. We are
accustomed to flies performing such feats, but at animals
five inches long, supple and fat, we are inclined to draw
the line. However, that is the way of Geckos, and — be it
confessed — the more we ponder over the mechanism of
their fingers and toes, the less we comprehend how such
little vacua can support or suspend such heavy creatures
from a dry and often porous surface."

Among the fifteen hundred species of true lizards many
are of very odd appearance and interesting habits. The
"flying dragons" of the East Indies have wing-like mem-
branes shaped very like the wings of a butterfly when ex-
tended, supported by long extensions of the ribs, and used
as parachutes in long leaps from tree to tree. They are
not much larger than a large butterfly, so that the name
"dragon" is rather a misfit as to size. Another remarkable
type is the Chlamydosaurus, or Frilled Lizard, of Aus-

nS

ZOOLOGY

tralia, with very long, slender legs and tail and a large frill
around the neck, which it erects when brought to bay. It
runs ordinarily on its hind legs, the fore legs hanging
down, the long tail balancing the body. In shape the frill
has an absurd resemblance to the great bony neck frills of
the Horned Dinosaurs, and the long legs and biped gait
are also singularly like certain Dinosaurs. It is said to

Fig. 27

-The Frilled Lizard of Australia. (Gadow.)

reach a length of two or three feet. The quaint little
"Horned Toads" (Phrynosoma) of the Western United
States, too, suggest some of the extinct Armored Dino-
saurs. The ugly, poisonous Gila Monsters of the same
region, brightly colored in orange and black, are a well-
known example of warning coloration, the colors enabling
the hungry bird or coyote to recognise and avoid them.

The Chameleons are found chiefly in Africa, altho they
range into Spain and India as well. They are very odd

THE VERTEBRATES— L. REPTILES 119

and interesting little lizards in their habits, and their color
changes have been carefully watched and studied. The
head is high and narrow, the body compressed sideways,
unlike most lizards, and the feet are very peculiar, two
toes in each foot being opposed to the other three. The
tongue is very peculiarly constructed and the club-shaped
sticky tip can be shot out suddenly to a distance of seven
or eight inches, annexing the insect which the chameleon
is stalking. They are extremely slow and cautious in their
movements. The changes in color are only partly pro-
tective, chiefly related to the excitement or quiescence of
the animal, or to heat and cold, as was long ago stated by
Linnaeus. Some of the Madagascar chameleons reach a
length of two feet, but they are mostly only a few inches
long.

No reptiles are so familiar, and yet so much maligned,
as snakes. Most people regard a snake with horror, or at
least with strong aversion. It is nasty, slimy, venomous;
it kills chickens, it "fascinates" and devours little song-
birds, and its bite is deadly poison to man. It is a thing to
be killed on sight, but from a good distance and with
stones or sticks, lest it attack you. Almost every small
boy and the great majority of grown folk will kill any
snake they see, feeling that it is the natural and proper
thing to do.

As a matter of fact, snakes are not at all slimy. Their
skin is perfectly dry and scaly; they are quite as clean to
handle as any dog or cat. There are a few poisonous
snakes, but one may readily learn to recognise and avoid
them. Most snakes (except in Australia) are perfectly
harmless, and are a great help to the farmer, as they de-
vour quantities of mice and insects. Snakes do not fas-
cinate birds — the fluttering, apparently helpless bird is
simply trying its best to entice the snake away from its
nest.

No snake, poisonous or non-poisonous, will pursue a
human being; their chief anxiety, if they see one, is to

Fig. 28 — Chameleons, Showing the Color Changes.
Note also the slender extensile tongue, with sticky, club-like tip.
(Gadow.)

THE VERTEBRATES— II. REPTILES 121

get away as quickly as they can to a place of safety.
When cornered or suddenly disturbed without a chance to
escape they will hiss and strike with the fore part of the
body — a snake's striking distance is from a third to a half
its length — but all this demonstration is entirely harmless
unless the snake is a poisonous one and strikes some part
of the body where its fangs can get through the clothing
to the skin. For all the popular fear of snakes, actual
recorded cases of death from the bite of a poisonous snake
in the United States are extremely rare. In India and in
other tropical countries the case is different. The mor-
tality from snake-bite is large, partly 'because venomous
serpents are more common, chiefly because the natives
habitually travel barefoot through the jungle. The deaths
from snake-bite in India are officially estimated at 22,000
a year — about one in fifteen thousand of the population.
It is probably less in other tropical regions.

It 13 commonly said that poisonous snakes may be dis-
tinguished by their broad flat heads from the non-poison-
ous kinds. This is only partly true. The poisonous snakes
of the viper family, including the viper, puff-adder, cop-
perhead, water moccasin, fer-de-lance and rattlesnake, do
have wide short heads ; so do several kinds of non-poison-
ous snakes. But in the coral snakes and cobras, the dead-
liest of all venomous serpents, the head is of the same
shape as the common harmless garter-snake or blacksnake.

Snakes are the most highly specialized of the reptilia.
Altho undoubtedly descended from four-legged walking
reptiles, no traces of the limbs remain except for some
vestiges in the boa and python; the body is much elon-
gated and adapted to crawling. The peculiar loosely hung
double-jointed jaws and the very elastic throat and neck
admit of extraordinary stretching so as to swallow the
prey whole, so that the snake literally gets outside of his
victim by alternately setting forward the upper and lower
jaws with their sharp little recurved teeth. The poisonous
snakes have one pair of teeth in the front of the jaw

ZOOLOGY

enlarged, and provided with a groove or canal through
which the poison is injected into the wound. In the cobras
and coral snakes the poison fangs are fixed ; in the vipers
they lie back against the roof of the mouth in repose, and
are erected only when the snake opens its mouth to strike.
The great majority of the species live on dry land, hiding
at night, and in cold countries hibernating through the

PyTHOtvl.

Fig. 29

... i/r/ifr,
B. hop./ly TEKMWTio/l or

-Tee Legs of a Snake.

winter in crevices among rocks, in burrows made by ro-
dents, or any other convenient shelter. Many snakes live
partly or wholly in fresh-water streams or ponds ; a few
are marine. Some species lay eggs; others bring forth
their young alive.

The largest snakes are the boas and pythons of tropical
countries, which are said to reach a length sometimes of
thirty feet, and kill their prey by crushing it between their
coils — whence the name constrictor. Nine-tenths of the
living species of snakes belong to the harmless colubrine

THE VERTEBRATES— II. REPTILES

123

group, of which the pretty striped garter-snakes are the
most familiar kind. The blacksnakes, bullsnakes and hog-
nosed snakes are well known in North America; many

Fig. 30 — Skull of Rattlesnake, Showing the Poison Fang.
A., when the mouth is partly closed ; C, when it is open.

others, under various names, take their place in other
continents. Some of these colubrine snakes constrict their
prey, others swallow it without the formality of previously
killing it

I24 ZOOLOGY

Related to the colubrine snakes are the cobras of the
Old World and coral-snakes of the New, all tropical or
sub-tropical, and the most deadly of poisonous serpents.
The majority of Australian snakes belong to this venom-
ous group, so that in Australia the popular fear and hatred
of snakes is justified more than in other continents. The
peculiar habit of cobras, when angered and ready to strike,
of expanding the skin of the neck into a broad, brightly
marked "hood," may be compared with the rattle of a
rattlesnake, and is usually supposed to serve as a warning
signal, serving notice upon approaching large animals that
a poisonous snake is at hand, to be carefully avoided and
not carelessly stepped upon or eaten. Some perfectly
harmless snakes have the custom, when one comes close
to them, of rattling the tip of the tail among the dry leaves
in a way that makes a fair imitation of a "singing" rattle-
snake. This quivering of the tail may be — probably is —
simply from excitement; nevertheless, it may serve to
scare off large animals of inquisitive disposition, and so
be useful to the snake.

The snakes of the viper family are all poisonous, and
inhabit both temperate and tropical regions. They in-
clude the vipers and puff-adders of Europe, Asia and
Africa, the moccasin, copperhead and rattlesnake of North
America, and the palm-vipers and fer-de-lance of Tropical
America and the West Indies. All are very poisonous,
altho not quite so deadly as the cobra group. The viru-
lence of the poison differs with the size and condition
of the snake, as well as with the species, and with the size
and stamina of the animal or person bitten. The bite of
the fer-de-lance has the reputation of being most generally
fatal to man.

CHAPTER VIII

THE VERTEBRATES — III. BIRDS

Birds as a class are the most attractive of animals. In
intelligence, in restless activity, in compact graceful form,
in handsome colors and markings, in musical voices they
equal or surpass any others. Altho egg-laying like the
lower vertebrates, they give far more care and attention
to the incubating of the eggs and the rearing of the young.
Family life is well developed among them, whereas among
the lower vertebrates can be found only some scarcely
recognisable beginnings of it. It is easy to understand
and appreciate the actions and sensations of a bird where
those of an ant are strange and foreign to the mental at-
titude of the human. Birds, too, are peculiarly the friends
of man in his relations to the world of nature. They are
the great natural check upon the multiplication of his in-
sect enemies. It has been said that if it were not for
birds the world would be so overrun with insects that all
crops would be destroyed, successful farming would be im-
possible, and in consequence civilized man could no longer
maintain his existence. This assertion greatly overrates
their importance to civilization, in regarding them as in-
dispensable to its continued existence. For, besides the
birds, there are other important natural checks upon the
indefinite multiplication of noxious insects, aside from
the artificial checks devised by man, or which would be
devised if the need for them were sufficiently urgent. Yet
the services rendered by birds to the farmer are truly of
125

126 ZOOLOGY

immense value, far outbalancing the occasional toll taken
from his seed-corn or his chicken-yard, even by those
birds which are most generally counted as his enemies.

"A bird," says Gadow, "may be known by its feathers"
— for all birds have feathers and no other animal possesses
them. In other ways they form the most compact and
readily distinguishable of the four groups of land verte-
brates. They are all surprisingly alike in construction of
skeleton and in the anatomy of the soft parts. With all
their wide diversity in size and form and habits of life, it
is singularly difficult to distinguish the bones of the dif-
ferent groups. The reason for this would seem to be that
successful flight, in an animal as large as a bird, involves
a high degree of specialization and mechanical perfection
of skeleton and muscles, and limits the variations that may
occur within rather narrow lines. The wide diversity of
form and structure that exists among the mammals is not
here found. Yet birds are an equally ancient group and
have 1 ad ample time to assume diversity of form in re-
lation to their diversity of habits hardly less than that of
terrestrial quadrupeds. On the other hand, they show
much more variety and brilliancy of color.

The high degree of specialization of birds appears
throughout their organization. The fore-limbs are modi-
fied to serve as wings, the neck is long, the tail short and
rudimentary so far as the skeleton is concerned. The
heart is four-chambered and the circulation rapid and
strong. The body is kept constantly at a temperature of
ioo°, instead of being only slightly higher than the tem-
perature of the surrounding medium, as it is in the "cold-
blooded" vertebrates. The lungs are large, and respira-
tion is further aided by air-sacs which expand from the
bronchial tubes into parts of the body, cavity and the hol-
low bones. The muscles, as in mammals, are more dis-
tinct and sharply defined than in the lower vertebrates.
The brain is of much higher type than in reptiles, and is
comparable to the mammalian brain. All in all, the birds

THE VERTEBRATES— III. BIRDS

127

represent a development of the vertebrate stock ranking
with the mammals as the highest type of animals, inferior
in certain phases of intelligence but superior perhaps in
activity and perfection of mechanism.

JEW, "t>IK,U- R-tst.

Fig. 31 — Specialized Adaptations for Flight.

The feathers of a bird serve two essential purposes. In
the first place they are bad conductors of heat, and pre-
vent the body-heat from escaping, just as does the hair of
.mammals. Thus the bird and mammal are enabled to

128 ZOOLOGY

maintain a high bodily temperature, impossible to the scaly
or naked-skinned reptiles, amphibians and fish. The high
bodily temperature and rapid circulation are essential to
the higher development and more active life of bird and
mammal. The second essential purpose of the feathers is
to aid in flight. While flight can be accomplished, as it
is in bats or insects and was in pterodactyls, without the
aid of feathers, yet they furnish the most effective mech-
anism that nature has devised for perfect control of move-
ment in the air with animals as large as birds.

The classification of birds is a most difficult problem.
The older arrangements, according to habits and external
characters, do not altogether agree- with the natural rela-
tionships of different groups. It is nevertheless very con-
venient, and the division into perchers, waders, birds of
prey, marine birds, ostriches, etc., altho known to be
unnatural, is largely used in default of general agreement
as to the natural relationships of the different groups.

It may be assumed that birds are derived from some
early type of primitive reptile, nearly related to the Dino-
saurs, in the early part of the Age of Reptiles. This hypo-
thetical ancestor of the bird would be distinguished from
the small upland Dinosaurs mainly by the fact that its
scales had evolved into feathers, thereby enabling it to
maintain a higher body-temperature and more active life.
Its habits would be much like those of the Ostriches, but
the tail long, vertebrated, lizard-like, with feathers on each
side, and the jaws provided with teeth instead of a horny
beak. The transformation of the fore-limbs into wings
might result either from their being used as an aid to
running on the ground or in making soaring leaps from
tree to tree. The second explanation is generally regarded
as most probable.

The oldest known fossil bird, the 'Archseopteryx' of the
Jurassic Period (middle part of the Age of Reptiles),
appears to be in this transitional stage. It was about the
size of a crow and had the toothed jaws and long verte-

THE VERTEBRATES— III. BIRDS 129

brated tail of a reptile, feathered like the shaft of an ar-
row. Its wings were short and small, and in the opinion
of some authors at least could hardly have served for true
flight, but might enable it to flutter from bough to bough.

The remains of a few birds of the Cretaceous Period
have been found. The two best known are the 'Hesperor-
nis' and Tchthyornis,' both provided with teeth, but the
tail is of the usual Bird type. 'Hesperornis' was a marine
diver, allied to the Loons and Grebes and fully as large^
but more primitive in various details of the skeleton.
Tchthyornis' was a flying bird, allied to the gulls. These
three genera, 'Archaeopteryx,' 'Hesperornis' and 'Ichthy-
ornis,' are the most important fossil birds as regards the
evidence they offer toward the problem of the course of
evolution of the birds and the relations of the various
modern orders. They are a long way, however, from
clearing up the problem. Most of the remaining fossil
birds are very imperfectly known, and a remarkably large
proportion of the more familiar kinds are large, flightless
ground birds. This does not mean, as might be thought,
that ground birds were formerly more abundant than now,
but rather that on account of their size and habits their
bones are more likely to be preserved and noticed by col-
lectors than those of the smaller fragile-boned flying
birds.

All that can be concluded as to the early evolution of trie-
class is that they were derived from long-legged bipedal
reptiles probably inhabiting the upland regions of the-:
great land mass of the northern continents; that they de-
veloped feathers from scales primarily for warmth, sec--
ondarily for flight; that they subsequently lost their tails,,
and later on their teeth ; but that at a very early period .
in their evolution they had become differentiated into va- •
rious habits — perching, running, diving, soaring. Since:
the center of dispersal of their early evolution was the:
upland regions of the north, it is reasonable to expect to>
find the highest and most typical birds in that general

130 ZOOLOGY

habitat. Remnants of primitive bird-races, archaic sur-
vivals, we should expect to find in the most remote south-
ern regions, or among marines or diving birds, or espe-
cially among the flightless ground birds. To a certain ex-
tent these expectations are carried out. But the birds are
a race of ancient development and their strong and sus-
tained flight gives them great powers of distribution over
distances and across barriers that impede or baffle the mi-
gration of terrestrial animals. The bird life, therefore, of
southern continents and tropical islands is much less pe-
culiar and archaic than the mammalian life. The very-
primitive races have long ago been swept out of existence
by competition with more progressive invaders. The ap-
parently primitive survivals, such as the ground birds
which to-day inhabit Australia, South Africa and South
America, and others which have become extinct; such
as the Penguins of the Antarctic region, the Loons and
Grebes of northern lakes, the Auks and other apparently
primitive types — all these must be regarded not as true
primitive survivals, but as cases of at least partial rever-
sion, of readaptation to ancestral habits from various
stocks of more progressive and typical flying birds, where
the conditions of their environment favored the develop-
ment of types of birds similar in habits to early ancestors
of the bird class.

The Ostrich is distinguished from all other ground
birds by having only two toes. It is native to the African
continent, but has been introduced in other arid regions
with success and is the largest of living birds. A full-
grown male stands over eight feet high and can outrun
a horse. The handsome tail feathers have long been used
for ornament, and the value of the annual output in South
Africa is estimated at five million dollars, mostly derived
from the large ostrich farms where the birds are semi-
domesticated. The Rhea of southern South America,
the Emus and Cassowaries of Australasia and the Kiwi of

THE VERTEBRATES— III. BIRDS 131

New Zealand are similar in habits to the Ostrich, but of
smaller size and with toes of the normal bird type.

Among the extinct flightless birds the Moas, which in-
habited New Zealand in quite recent geologic times, were
related to the Kiwi, but reached a much larger size than
the Ostrich, the largest being estimated at twelve feet in
height. The extermination of these birds by the Maori
natives dates not more than four centuries ago. Equally
recent is the disappearance of the great yEpyornis" of Mada-
gascar, upon which, it is said, the Eastern legends of the
'Roc' are founded. The Roc, as it is described in the
Arabian Nights, is exaggerated and distorted into a flying
bird of impossibly gigantic size; but it may have been
founded upon the eggs of these great ground birds, some
of which are still in existence and large enough to hold
two gallons of liquid.

These great flightless birds are usually grouped into a
sub-class, Ratitse, altho they are very probably degenerate
descendants of several stocks of flying birds. There are
other large extinct flightless birds in which the relation-
ship to different groups of flying birds is more clearly
seen. Such are the 'Dodo' and 'Solitaire' of Mauritius,
related to the Pigeon, and exterminated only two centuries
ago; the 'Phororhachos' of the Miocene epoch in Pata-
gonia, related to the modern Seriema or Crested
Screamer; the 'Gastornis' of the European Eocene, re-
lated to the Ducks.

The most primitive — or degenerate — of marine birds
are the Penguins of the Antarctic regions, flightless, active
swimmers and divers, with the wings modified into pad-
dles. In Penguins the three metatarsal bones of the hind
foot are partially separate, more primitive than in any
other bird. They are known to have inhabited the Ant-
arctic seas at least as far back as the early Tertiary, and
are probably a very ancient group. If future explorations
should succeed in discovering fossil remains of the fauna
which inhabited the old Antarctic continent during the

132 ZOOLOGY

Age of Mammals, it is very probable, in the present
-writer's opinion, that its higher land vertebrates will prove
to have been, not mammals, but great ground birds of
which the modern Penguins are a solitary marine survival.

The Divers and Grebes are the most primitive of the
•modern flying birds. Aquatic or marine in their habits,
they are mostly heavy and awkward in flight or on land,
but excellent swimmers and divers, using the webbed or
lobed feet very effectively in swimming. The Divers are
Arctic, the Grebes cosmopolitan in distribution.

The Petrels and Albatrosses and their allies are strong-
flying ocean-birds, worldwide in distribution, but most
abundant in the desolate wastes of the Southern oceans.
Eeyond all other birds they are at home on the ocean,
resting and sleeping on the surface of the waves, resorting
to land only for breeding purposes, and nesting on the
rocky ledges of wild, inaccessible sea-cliffs.

A much larger group of water birds is represented by
the Storks and their allies, mostly wading birds inhabit-
ing fresh water, but some marine, like the tropic-birds,
Gannets, Cormorants and Frigate-birds. The Storks,
Ibises, Herons and Bitterns, the Flamingoes and Pelicans
are ,the most familiar wading types, various in size and
proportions, in habitat and nesting habits, feeding upon fish,
frogs and other -denizens of the marshes and rivers. Many
of the birds of this group are distinguished by their large
size, handsome colors and decorative plumes.

The Ducks and Geese are a still more familiar group
of birds, aquatic in their habits, and mostly fresh-water
dwellers, but swimming and diving rather than wading,
more omnivorous in their feeding habits than the wading
birds. They are cosmopolitan, but most abundant in the
northern continents. The domesticated species are of
large economic importance, and the wild species form a
considerable proportion of the common game birds.

The Eagles, Hawks and Vultures are widely different
in appearance and habits from the preceding groups. They

THE VERTEBRATES— III. BIRDS 133

constitute the "Birds of Prey," excluding the Owls, and
are all carnivorous, mostly predaceous, living on land,
and preying upon smaller birds and mammals, or upon car-
rion, sometimes upon fish, occasionally upon insects. In
accordance with their habits they are swift and powerful
in their flight, the bill is adapted to seize and tear their
prey, the claws are sharp, strong and curved. The Condor
of the Andes is one of the largest of flying birds. While
to some extent Eagles and Hawks merit the hostility of
man by their slaughter of smaller birds, their depredations
upon the poultry-yard and their occasional attacks upon
larger domestic animals, yet most of the hawks, at least,
prey largely or chiefly upon rodents and, with the owlsT
are an important natural check upon their increase. As
a class they undoubtedly do far more good than harm to
the farmer, and their persecution is often followed by a
terrifying increase in the numbers of noxious rodents.

The Domestic Fowl and their allies are the most fa-
miliar of birds and the most important economically. To
this order belong, besides the domestic fowl, peacock, tur-
keys and guinea-fowl, the pheasants, partridges, grouse
and quail, the curassows and hoatzin of South America
and many less known birds. In the pheasant group are
included the greater number of game-birds. The birds of
this order are generally polygamous and the majority
handsomely colored, especially the males.

The Rails, Cranes and Bustards are a second wading
group, similar in habits to the storks and their allies, but
not closely related. Another order of very varied habits
is formed by the plovers, sandpipers and curlews, the
gulls and auks and the pigeons, very diverse in outward
form, but connected by common characters in the skeleton-

The Cuckoos and the Parrot family, comprising the
Parrots, Parrakeets, Macaws and Cockatoos, are distin-
guished by having two of the toes reversed, instead of
one as in most other birds, an especial adaptation for
climbing and grasping branches.

134 ZOOLOGY

A much larger order includes the Night-jars, swifts and
humming-birds, the Owls, Kingfishers and woodpeckers,
the trogons, toucans, hornbills and various other more or
less familiar birds. They are all land-birds, of arboreal
habits, with short legs, the majority nesting in holes in
trees or similar places, and the young are born blind and
peculiarly helpless. Their feeding habits are various,
the owls being predaceous, pursuing small mammals and
birds and mostly nocturnal ; the kingfishers feed upon fish,
the woodpeckers especially upon boring beetles, the swifts
and night-jars upon insects, the humming-birds upon the
nectar of flowers, while the large toucans and hornbills
are mainly fruit-eaters. The owls by their destruction of
noxious rodents render aid to the farmer that far more
than counterbalances the toll they levy on his chickens.

By far the largest order of birds is the Passeriformes,
including the song-birds and their allies. It contains
some 5,500 species, more than half the whole class. To
this great order belong all the true singing birds, besides
many which do not sing. They are mostly of small size,
o" high intelligence, as shown in their habits, their nest-
building and in the care of their young. They are all
land birds, terrestrial or arboreal in their nest-building,
the feet adapted for perching, with one reversed digit and
three in normal position ; their powers of flight moderate
or highly developed. A large proportion of them are
seasonal migrants, traveling thousands of miles in their
annual flights. They inhabit every region of the world,
continents and islands; they range from seacoast swamps
to above the snow-line in the mountains — forest, plain and
desert, all have their special types of song-birds, adapted
in habits and plumage to the requirements of their sur-
roundings. Their numbers and variety are immense, and
even in large ornithological books their mere enumeration
is lengthy and cumbersome.

CHAPTER IX

THE VERTEBRATES — IV. MAMMALS

The mammals form the highest and most important
group of the vertebrata. Broadly speaking, they corre-
spond to the popular terms of 'quadruped/ but also include
man himself, and the whales, seals, and manatees. As rep-
tiles have scales, and birds feathers, mammals have hair
as their most obvious character. But the skin is often
partly, rarely wholly, naked; and in a few mammals scales
or bony plates are also present, covering the surface more
or less completely. The young are born alive and suckled
by the mother; this is the primary distinguishing charac-
ter. They are warm-blooded, air-breathing, the heart
with four chambers, and lungs and heart are separated
from the abdominal organs by a muscular diaphragm.

The sense organs are more highly developed than in
other vertebrates, the brain larger and more complex,
the skull more consolidated. Teeth are nearly always
present, and usually elaborated into various and often
complex structures adapted to the various food require-
ments of the animal. The limbs and feet show an equally
wide diversity in adaptation to various habits and modes
of life.

The Tertiary Period is often called the Age of Mam-
mals. During that time the mammals assumed the domi-
nant position among animals, previously held by reptiles,
and evolved, mostly from small ancestors of uniform type,
into the diverse and often gigantic species of the present
135

136 ZOOLOGY

day. Ancestral mammals had first evolved from primi-
tive reptiles long before, probably before the close of
the Age of Amphibians, and these small primitive ances-
tors had been living side by side with the gigantic Dino-
saurs during all the Age of Reptiles. They were rare
and of minute size, probably tree-living animals, and it
Is not unlikely that their arboreal life, with its continual
demands on intelligent action and readiness to grasp op-
portunities, stimulated the much higher grade of intelli-
gence to which the mammals had attained when they first
appear in numbers at the opening of the Tertiary Period.

These primitive ancestral mammals were small, long-
tailed animals which might be compared to the modern
tree-shrews. They had flexible limbs and feet, slender
body, moderately long neck, slender skull, and long jaws
with teeth adapted to insect-eating. The number of teeth
was upward of forty-four. The toes were five on each
foot, the digits flexible, clawed, the inner digit to some
^extent opposable, and with one less joint than the others.

Fossil mammals have been found in great numbers and
variety in the formations of successive epochs of the Ter-
tiary Period, and it is possible to trace the successive
stages through which they evolved from these small primi-
tive types into the various kinds of modern quadrupeds.
Conversely, when the ancestral series of any modern quad-
ruped is traced back it is found leading down in every
case toward this identical small primitive type; and when
one examines and compares the structure and anatomy
of any modern animal it is seen that it is most easily
explained as a modification from this common primitive
type in adaptation to one or another habit of life.

Some races have become herbivorous, others carnivo-
rous, others fruit-eating, and the teeth have been modi-
fied in accordance. Some have remained arboreal, oth-
ers have become terrestrial, aquatic, or fossorial; some
have remained small, others have become large, or even

THE VERTEBRATES— IV. MAMMALS 137

gigantic in size; and the limbs and feet have been modified
to suit their various habits and size.

In herbivorous mammals the cheek teeth are used for
crushing and grinding vegetable food, the front teeth for
cropping. The true molars are enlarged, and complicated
into a more or less elaborate pattern of crests or crescen-
tic ridges which serve to chop or grind the food. The
premolars either degenerate or become like the molars.
The canines are sometimes enlarged into tusks for fight-
ing, sometimes degenerate and disappear. The incisors
are converted into spadelike teeth for nipping off food,
into large gnawing teeth, or degenerate and disappear.
In carnivorous animals, on the other hand, the pointed
canines, used for seizing and holding the prey, are large,
sharp and strong; the premolars, used for cutting the
food, are well developed; while the molars, used for grind-
ing, tend to degenerate or disappear, or to become more
like the premolars, and to be used chiefly for cutting up
the food. In frugivorous animals the cheek teeth are
used for crushing fruit or nuts, and become flat-topped;
the premolars often degenerate; the front teeth, used for
biting off the food, are converted into a row of little
spade-shaped teeth. Animals of more mixed diet show
various combinations of these characters in the denti-
tion.

The animals which have remained arboreal have re-
tained and perfected the adaptation of limbs and feet
to this purpose, but have departed less than any others
from the primitive type. Among terrestrial mammals are
found a variety of adaptations. Some have developed
speed, to escape from their enemies or pursue their prey.
For this purpose they have taken to walking or running
upon the fingers, or even upon the tips of the claws, instead
of, as at first, upon the flat of the foot. In consequence,
the lower limbs and feet are lengthened, the joints of
the feet made stronger and more compact, the side toes
tend to degenerate and the middle toes bear the weight

138 ZOOLOGY

of the body, and the claws are converted into broad,
strong hoofs which finally support the whole weight
Other terrestrial races have depended upon their fighting
capacity rather than upon speed; they have increased
rapidly in size, developed horns, tusks, armor plates or
spines, for attack or defense, and the limbs have become
adapted to bearing enormous weights, with heavy bones,
massive muscles, short, heavily padded feet. Fossorial
mammals have developed short and exceedingly powerful
limbs and great digging claws upon the feet. In aquatic
mammals the feet become webbed, and are finally con-
verted into paddles; or in such as developed a powerful
swimming tail the hind limbs have degenerated and dis-
appeared. Finally one group of aerial mammals appears,
the bats, in which the fore limbs are converted into wings,
by lengthening the fingers and developing a web between
them and the sides of body and tail. Various arboreal
mammals also have weblike expansions of the skin, which
they stretch as parachutes in leaping from bough to
bough.

The quadrupeds are less dependent upon temperature
and climate than most of the lower animals, while they
are more strictly limited in their migrations by the boun-
daries of the continents and islands which they inhabit.
Moreover, they are not so ancient as the invertebrates
and lower vertebrates; their evolution and dispersal over
the world has mostly occurred during the Tertiary Pe-
riod, when the distribution of land and water was not
so very different from what it is at present. We find that
the present general arrangement of the land areas, with
a great central northern land mass and isolated peninsu-
lar continents stretching down into the southern hemis-
phere, is the key to the geographical distribution of mam-
mals. They have spread out in successive waves of mi-
gration from one part or another of the Holarctic region,
and each new wave of higher stages of evolution in the
different races has driven its more primitive predecessors

THE VERTEBRATES— IV. MAMMALS 139

"before it toward the remotest confines of the southern
continents and islands. This general tendency has been
limited by the land connections with the southern conti-
nents and islands.

The connection with South America was interrupted
during a part of the Tertiary, and during that interruption
the South American animals evolved independently into
races which were quite different from those of the north-
ern world. When connection was resumed, the northern
animals invaded South America, while some of the south-
ern races invaded North America ; but the superior quality
of the animals evolved on the great northern land mass
enabled them to overcome and displace those of South
American origin, which have nearly all become extinct.
In Africa and in peninsular India the connection was
also interrupted for a time and then restored, with the
same results; but the interruption did not last so long.
Australia and the adjoining islands have been separated
since before the Tertiary Period, and the higher mammals
have never been able to reach those regions. In conse-
quence, the more primitive mammals which reached there
at an earlier period have evolved and specialized into a
large and varied mammal fauna paralleling the higher
mammals of the northern world.

Some of the East Indian islands, now separated from
the mainland only by shallow seas, have been united with
it during the Tertiary Period, so that the great land ani-
mals could invade and occupy them. Other oceanic islands,
like Celebes, Madagascar, the West Indies, New Zealand,
and many smaller islands, are separated by deep oceans
from the mainland. In these it is noted that land mam-
mals are generally absent, or are peculiar types different
from those of other regions, and probably developed on
the islands themselves from such small mammals as might
once in a long while reach their shores on floating rafts
drifted out from the mouths of rivers on the mainland.
Small mammals, such as rodents, insectivores, or small

140 ZOOLOGY

lemurs, might once in a while gain a footing on the iso-
lated island in this way, and once established, in the ab-
sence of competition would evolve into a variety of larger
races, as the Marsupials did in Australia. In this way
can be explained why Madagascar possesses none of the
elephants, rhinoceroses, zebras, antelopes, dogs, cats, etc.,
of the adjoining coast of Africa, but does have a great
number of lemurs not found elsewhere, a number of in-
sectivores of a family (Centetidse) peculiar to the island,
two or three carnivores, related to the civets but of very
exceptional character. The bush-pigs may have been
brought there by man ; the pigmy hippopotami found fos-
sil on the island may have reached it by swimming. But
the absence of practically all the mainland animals, to-
gether with the presence of peculiar types which seem
adapted to take their place, can scarcely be explained ex-
cept by supposing that the island has been separated from
the African mainland for a very long period. The prob-
lems of geographical distribution are a most fascinating
branch of zoology and have attracted a large share of the
attention of scientific men, especially in recent years.

In the arrangement of this class of vertebrates first
must be set aside the Egg-laying mammals of Australia
as an exceedingly archaic type, to a great extent a con-
necting link between mammals and the primitive reptiles
from which they are descended. As might be expected,
these most ancient of mammals are found on the very
outskirts of the mammalian domain, Southern Australia
and Tasmania, most remote from the main center of
Mammalian evolution in the north. These form the sub-
class Prototheria.

The rest of the mammals may be divided again into
a small and a large group, the Marsupials, or Pouched
Mammals (Metatheria), in which the young are born
alive, but very immature, and are carried for some time
in a pouch on the under side of the mother's body until
they are able to shift for themselves; and the Placental

THE VERTEBRATES— IV. MAMMALS 141

Mammals, 'Eutheria,' including all the rest. In the pla-
cental the young are more mature when born, and are
never carried about in a pouch. Either they are able to
follow the mother about, or she remains with them, in
some suitably protected spot, until they are well grown.

There are, of course, numerous distinctions in the skele-
ton and soft anatomy to support this division of the mam-
mals into Prototherians, Metatherians and Eutherians;
but from a modern point of view it is well to lay weight
on these differences in the care of the young. For, as
has been seen among invertebrates, the progressively
greater care of the young, the prolongation of infancy,
appears to be, more than anything else, the key to the
possibilities of higher development. Among insects it is
patent that the higher life of the social wasps and bees
centers mainly about the care of the young. It is no less
true among vertebrates. The most prominent feature in
the life of birds and mammals is the care that they take
of their young; and in the higher orders of mammals the
period of infancy becomes progressively longer until it
reaches its maximum in man.

The Mammalia are further divisible into twenty-three
orders as generally accepted in recent years. Their ar-
rangement is as follows :

I. Sub-Class Prototheria. Egg-laying Mammals.

1. Order Monotremata, Ornithorhynchus and Echid-

na.
II. Sub-Class Metatheria. Pouched Mammals.

2. Order Marsupialia. Opossums, Kangaroos, etc.
III. Sub-Class Eutheria. Placental Mammals.

3. Order Insectivora. Hedgehogs, Moles, etc.

4. Order Edentata. Sloths, Armadillos, etc.

5. Order Cetacea. Whales, Dolphins, etc.

6. Order Sirenia. Manatee and Dugong.

7. Order Perissodactyla. Horses, Rhinoceroses, Ta-

pirs.
& Order Artiodactyla. Pigs and Ruminants.

142 ZOOLOGY

9. Order Proboscidea. Elephants.
10-16. Orders Condylarthra, Amblypoda, Toxodontia, Li-
toptema, Arsinoitheria, Embrithopoda, Astrapo-
theria. Extinct Hoofed Mammals.

17. Order Hyracoidea. Conies.

18. Order Rodentia. Rats, Mice, Rabbits, etc.
19-20. Orders Tillodonta and Taeniodonta. Extinct

Clawed Mammals.

21. Order Carnivora. Dogs, Cats, Weasels, Civets,

etc.

22. Order Chiroptera. Bats.

23. Order Primates. Lemurs, Monkeys, Apes, Man.
The Egg-laying Mammals, therefore, must be treated

first. These two little animals, the 'Ornithorhynchus/
or Duck-bill, and the 'Echidna/ or Spiny Anteater, inhabit
Southern Australia and Tasmania. They are the most
archaic of all mammals, and from their geographic loca-
tion may be regarded as the vanguard of the great mam-
malian dispersion which has spread out in successive
waves from the northern continental land mass. They
are classed with mammals because of their hair-covered
skin, solid skull, jaws all of one piece, and various features
of their anatomy, but they retain numerous characters
in the skeleton approaching those of the primitive rep-
tiles of the Coal Period from which the mammals are
believed to be descended. Like the Marsupials, these ani-
mals are provided with a pouch, to which the eggs are
transferred after they are laid. The eggs are hatched
in the pouch, and the young animal remains there for
some time, nourished by a secretion from the skin of the
mother.

The Ornithorhynchus lives in burrows along the mar-
gin of ponds and streams, feeding upon fresh-water clams,
crustaceans, etc "During the Australian winter," says
Doctor Semon, "from June till the end of August, when
the nights are cold, you may be sure to find the animals
in the river at sunrise and sunset. If you are near the

THE VERTEBRATES— IV. MAMMALS 143

river early enough to watch the rising of the sun, you will
see something flat, one or two feet in length, floating on
the water, like a plank, as soon as the first sunbeams
strike the river surface and allow you to discern single
objects. Sometimes it lies motionless for a while, then
it disappears, to reappear again after a few moments in
quite a different place. This is an Ornithorhynchus seek-
ing its breakfast in the mire of the river."

The Echidna, or Spiny Anteater, is a shy, nocturnal,
burrowing animal, living in the dense, impenetrable scrub
and wild, rocky parts of the country. "On its nightly
expeditions," says Semon again, "the anteater seeks worms
and insects of all kinds, which it extracts from their hid-
ing places in earth holes, between stones, and in rotting
bark, by means of its long, wormlike tongue. Its princi-
pal food, however, consists of ants, which it captures like
other anteaters, by thrusting its tongue into the anthill,
waiting till it is covered with ants, and then drawing it in
quickly.

It is interesting to note that the Pouched Mammals
have a lower and less constant body temperature than
any of the higher mammals. In this respect also they
approach the reptiles and other "cold-blooded" verte-
brates.

The Marsupials are more or less intermediate between
the Monotremes and the placental mammals, but decid-
edly nearer in all respects to the latter. They lack a pla-
centa, that particular internal organ which enables the
young to be brought to a maturer, more perfected state
before birth. In consequence they are born in a very rudi-
mentary condition, and are usually transferred to a pouch
on the under side of the mother to complete their devel-
opment. Teats are present, as in the higher mammals,
and the little animal is suckled within the pouch.

Marsupials are to-day chiefly found in Australia and
the adjacent islands. The opossums of South and Central
America, of which one species ranges northward into the

144 ZOOLOGY

United States, and a rare little animal (Caenolestes) re-
cently discovered in the Andean highlands, are the only-
living representatives of the order outside of Australasia
(except that a few of the Australian marsupials also range
northward into the East Indies). Formerly the Marsu-
pials were worldwide in their distribution. It is probable
that most, if not all, of the tiny, shrew-like mammals
which have been referred to as contemporaries of the
gigantic Dinosaurs during the Age of Reptiles were
Marsupials, or at least equivalent to them in their stage
of evolution. But with the advent of the higher placental
mammals at the beginning of the Tertiary Period, the
Marsupials gradually disappeared from the northern
world. A few survivors have been found among the
early Tertiary mammals of Europe and North America,
and they were abundant in South America until the lat-
ter part of the Tertiary Period, when a great invasion of
the northern mammals swept them out of existence save
for the opossums and 'Caenolestes.'

In Australia, however, they were undisturbed by north-
ern competitors, as this continent remained isolated
throughout the Tertiary Period. "They were allowed,"
says Semon, "to thrive unhindered, to regard the bush
forests, the river banks, the rocks and mountains, the
grassy pastures, as their undisputed domain, adapting
themselves more and more to the characters of their sur-
roundings. Some feed on the grass of the bush, like kan-
garoos and wallabies ; others dig for roots and bulbs, like
the kangaroo-rats; still others seek their food on euca-
lyptus trees, like Phascolarctus, the Australian opossum,
and the flying Marsupials. Bandicoots (Peramelidae) and
the shrewlike bush rats and bush mice (Phascologale,
Antechinomys) are mostly insectivorous; the native cat,
the Tasmanian devil, and the pouched wolf carnivorous,
with teeth strongly reminding us of those of Placentalia.
As different as their food are the dwellings, the habits,
and the modes of locomotion in all these animals. Like

■:':;.jliBF> -^^

5 1

*

-

rM%^^ '

An Eighty-foot Sulphur-bottom Whale. (A. M. N. H.)

THE VERTEBRATES— IV. MAMMALS 145

jumping mice, the kangaroos hop over the level country,
some of them — for instance, the rock-wallabies — being
able to execute their leaps also in mountainous country
with the cleverness of a chamois, while the tree-kangaroo
(Dendrolagus) performs real climbing antics in the
crowns of the highest trees. We see the Australian opos-
sum and the Cuscus climb with the agility of squirrels;
Petaurus flits from tree to tree, and is therefore erro-
neously called by the Australians 'flying squirrel'; Phas-
colarctos, however, climbs along as lazily as any sloth.
Slinking is the gait of the native cat, and trotting that
of the pouched wolf.

"In the grass, in rocky caves, on the ground, or on
trees, we find the hiding places and lairs of the marsu-
pials. Like rabbits, the wombats dig long and deep bur-
rows in the ground, and quite subterranean are the life
and habits of the blind Notoryctes typhlops, which latter
has but recently been discovered in the deepest interior
of Australia, and the mien and habits of which strongly
remind us of our mole; and still all these animals have
nothing to do with moles, squirrels, flying-squirrels, rats,
jumping-mice, shrew-mice, cats and wolves. All of them
are marsupials, and related much more closely to each
other than to any of the placental mammals which they
resemble as to looks, movements or habits, and from which
they derive their popular names. Further, we must not
imagine that the placental beasts of prey have sprung
from similar marsupial beasts of prey — the genuine jump-
ing-mice from kangaroos, moles from Notoryctes, and so
on. It is more probable that the transition from marsu-
pials to placentals took place only once, and from a less
specialized group of marsupials than now exists. The
original group of placentals that arose thence has differ-
entiated into distinct series, like insectivora, rodents,
hoofed animals, beasts of prey, lemurs, apes and men.
The outer resemblance between certain groups of marsu-
pials and placentals is a phenomenon of convergence, and

i46 ZOOLOGY

is produced by adaptation to similar conditions of life.
It ought to be judged like the resemblance between wood
lice and centipedes, fishes and whales, birds and bats.
Outer resemblance is not always a proof of blood rela-
tionship. Echidna, porcupine and hedgehog are no wise
related, much as they resemble each other, since the for-
mer is related to Ornithorhynchus, the second to the chin-
chilla, and the last to the mole."

The Marsupials are divided into two main groups. In
the Polyprotodonts, mostly carnivorous or insectivorous,
the canine teeth are sharp and strong, the incisor teeth
small and set in a transverse row, and the cheek teeth
adapted to cutting flesh or insect food. In the Diproto-
donts, mostly herbivorous or frugivorous, the canine teeth
are minute or absent, and one or two pair of the incisor
teeth are enlarged somewhat as in rodents, while the cheek
teeth are fitted for crushing or chopping vegetation, fruit
or nuts. In the first group the feet have usually five
separate well-developed toes; in the second the toes are
usually reduced in number, the fourth digit enlarged, the
others enclosed in a common integument.

Of the Carnivorous Marsupials, or Polyprotodonts, the
American opossums and the Thylacine, or Tasmanian
"Wolf," the Tasmanian Devil (Sarcophilus) and Dasyure,
or "Native Cat" of Australia, are the best known living
types. In the Australian regions these take the place
of true placental Carnivora of other continents, which
are unknown there, except for the Dingo, or Wild Dog,
probably introduced by man. But even in the short time
that the dingo has been present on the main continent
of Australia, his superiority as a hunter over his marsu-
pial competitors is shown by the fact that the Thylacine
and "Devil," abundant in Australia in prehistoric times,
have disappeared from the mainland and survive only in
Tasmania, where dingos have not been introduced. In
South America during the Tertiary Period, while it was
an island continent, there were, likewise, no true Car-

THE VERTEBRATES— IV. MAMMALS 147

nivora, and there, too, the carnivorous marsupials devel-
oped into large wolf-like, lion-like and smaller cat-like or
civetlike forms, to prey upon the various herbivora. When,,
toward the end of the Tertiary, the continent was united
with North America, true carnivores invaded it from
the north, and soon caused the extinction of all the car-
nivorous marsupials, except the opossums, whose arboreal
habits and more omnivorous or insectivorous diet enabled
them to survive to the present day. The fossil remains of
these extinct South American marsupial carnivores dis-
covered in recent years show so much resemblance to the
Thylacines that they have been referred to the same fam-
ily, and supposed to have migrated from Australia to-
South America by means of land connections with the
Antarctic continent. In the present writer's opinion the
resemblance is better explained as due to similar adapta-
tion from primitive opossumlike marsupials, originally de-
rived, with the rest of the South American and Australian
mammals, from those primitive mammals which lived dur-
ing the Age of Reptiles in the Northern continents.

These primitive marsupials, ancestors of the various
living marsupials, and from which, at a somewhat earlier
period, the remote ancestors of the higher, or placental,
mammals had branched off, are pretty closely represented
in the living opossums. So that one may, without very
great straining of facts, place the 'possum in the gallery
of ancestral portraits, and picture from him the sort of
animal from which Man, in common with all the quadru-
peds, is remotely descended. Little ratlike or shrewlike
animals, with long, prehensile tail, with opposable thumb
and great toe, insectivorous, living in trees, and venturing
out from their hiding places mainly by night, alert and
intelligent above their fellows of the Reptilian Era, but
not by the higher standards of modern quadrupeds — such,,
as far as can be judged, were the remote ancestors of
the mammals; and such are the opossums to-day.

The Thylacine is a much larger animal, with teeth

148 ZOOLOGY

specialized for flesh-eating and feet for running. Its su-
perficial resemblance to a wolf is well shown in the illus-
tration; the striped rump suggests the tiger, also, while
the long, stiff tail is an opossum character. It is now
limited to the mountains of Tasmania, as is also the re-
lated "Tasmanian Devil," but both are found fossil in
Australia. The Dasyures are smaller, civetlike animals
of Australia and Tasmania which take the place of the
smaller predaceous carnivora of other parts of the world.
The Bandicoots are small omnivorous or insectivorous
marsupials, with teeth like those of the carnivorous group,
but feet more like those of the herbivorous group. In
the Wombats the reverse is the case, the teeth being of
the "diprotodont" type, while the feet have five well-de-
veloped toes with strong claws. These animals, in their
heavy, clumsy build, short, stubby tail and shuffling walk,
very much resemble small bears, and are commonly known
.as "native bears." The Phalangers are small squirrellike
marsupials, arboreal in their habits, and found throughout
Australasia, ranging as far north and west as Amboyna
and Celebes among the East Indian islands.

The largest living Marsupials are the Kangaroos, which
in Australia take the place of the hoofed quadrupeds of
other continents. "These animals," says Semon, "will al-
ways hold their own as the most characteristic feature
of Australia. Every one who has observed them in zoolog-
ical gardens and menageries will have remarked that
there exist larger and smaller kinds of this animal, but
we are apt to lose sight of the many and considerable
differences between the various species and genera in the
simple fact that the general quaintness of their aspect,
the peculiar structure of their extremities and tail, and
the queer manner of their locomotion, lead us to over-
look everything else. Nevertheless, these animals, ap-
parently so uniform in structure, show an astonishing
variety in their more minute features, their habits and
their distribution. If we reckon only the genuine Macro-

THE VERTEBRATES— IV. MAMMALS 149

podidae without the kangaroo-rats, we have to admit
seven genera, comprizing forty-three species ; and of these,
twenty-three belong to the genus Macro-pus, the real kan-
garoo. The Australian colonists call all the larger kinds
'kangaroos' . . . the smaller kinds they call 'wallabies/"
The kangaroos "for the most part prefer the open bush,
the level or undulating ground of which gives them occa-
sion to exercise their splendid leaping powers, besides of-

Fig. 32 — The Tasmanian Wolf or Thylacine. (Flower and
Lydekker.)

fering them a rich pasture. The leaps of the bigger kinds
have generally a length of several yards. When chased they
heighten the extent of a single leap to ten yards or more.
The jerk is produced by the hind legs without assistance
from the tail, as some think. This is easily proved by,
observing the track the animals' leaps imprint upon the
ground. The tail is flourished at every leap, but hardly
touches the earth. It seems to help the leaping animals
to steer, and to support its weight when resting."

150 ZOOLOGY

While the Kangaroos are the largest of living Marsu-
pials, the extinct Diprotodon and Nototherium, which in-
habited Australia during the Pleistocene Epoch, were gi-
gantic animals, equaling the Indian Rhinoceros in bulk,
and curiously resembling the modern elephant in the long,
straight, massive postlike limbs and short, rounded, stubby
feet. They were related to the Wombats, and may, in fact,
be regarded as a sort of gigantic development of this
race, adapted probably to a less arid climate and more
abundant vegetation than now prevails in Australia. Nu-
merous skeletons of these extinct giants have lately been
found in the dried-up lakes of West Australia, north of
Adelaide.

The Cetaceans are mammals which have become adapted
to marine life and assumed a fishlike form, lost their
hair, converted the fore limbs into paddles, lost the hind
limbs entirely, and converted the tail into a swimming
organ. They are only superficially like fish. The skele-
ton and internal organs, the quality of the muscles, the
teeth, are all those of land mammals, and widely different
from fish. They are warm-blooded, bring forth their
young alive, and nurse them after the manner of land
quadrupeds. The brain is far superior to that of any
fish, and the intelligence is of a much higher order than
that of fishes. The intelligence of the dolphin seems to
have been noticed by men in prehistoric times, for it
appears in Greek mythology as the friend and active helper
of man.

The Cetaceans include the largest of known animals,
living or extinct, the whalebone whales and sperm whales,
and the numerous smaller active species of which the
dolphins and porpoises are most familiar. The order is
divided into two groups.

The Whalebone Whales (Mysticetae) are toothless, and
provided with fringed plates of whalebone which act as a
sieve to catch and retain in the mouth the minute crus-

THE VERTEBRATES— IV. MAMMALS 151

taceans, etc., upon which the animal feeds. There are
several kinds of these whales, all of gigantic size. In
the "Right" Whales, 'Balsena,' the head is more arched
and the whalebone plates and fringes longer. In the
Rorquals, 'Balaenoptera,' the whalebone plates are smaller,
and the animal is longer-bodied, the head less gigantic,
there is a dorsal fin, or hump, not present on the right
whales (whence the names of "finner" and "hump-back"
applied to different species), and the throat has a series
of longitudinal furrows. The species of Balsena reach
a length of 40 to 70 feet, with an enormous bulk. The
rorquals, tho somewhat less massive, attain even greater
size. A large "sulphur bottom" whale will reach 75 to 85
feet in length and weigh about 75 tons. A skeleton in the
Museum of Christchurch, New Zealand, is reported as
measuring 87 feet in total length, the skull alone being 21
feet long. The danger and romance of whaling are de-
parted, and it has become a merciless butchery, which
bids fair soon to extinguish utterly the largest and most
magnificent of living animals. The whalebone, which is
now the only practical object of the pursuit, seems a
pitifully inadequate compensation for their extinction.

The Toothed Cetaceans (Odontocetes) have no baleen
plates, but the jaws are set with sharp-pointed recurved
teeth, adapted to seize and hold the fish and other swift-
swimming marine animals on which they prey. The sperm
whale, or Cachalot, attains a size almost rivaling the
Whalebone Whales; 55 to 60 feet is a conservative esti-
mate of the length, and of this nearly a third is the gi-
gantic, blunt-snouted head. In the cavities of the skull
are stored vast quantities of fluid fat, the spermaceti of
commerce. From the sperm whale is also obtained the
rare and valuable substance ambergris, used in the prepa-
ration of perfumes.

Unlike the whalebone whales, which are confined to
the cold temperate and Arctic seas, the sperm whale
chiefly inhabits the tropical oceans. Its food is chiefly

152 ZOOLOGY

cuttlefish, and it is said to especially seek the gigantic
octopus, which lives far beneath the surface of the deep
seas, and has so rarely been seen by man that it was, till
recently, regarded as a fabulous monster. Bullen, in the
'Cruise of the Cachalot/ has given a fascinating account
of a combat between these giants of the deep. The sper-
maceti, oil and ambergris of the cachalot are the objects
of a considerable fishery, which, however, does not at
present threaten the extinction of the animal. The first
two products are found in the other toothed cetaceans,
but in smaller quantities.

The dolphins and porpoises, and their allies, are com-
mon in all parts of the world, mostly marine, but some
of them inhabiting the great tropical rivers. The largest
of the dolphin group is the grampus, or killer, a fierce
predaceous species which reaches a length of thirty feet.
The Killer preys upon seals and porpoises, and several
will combine to attack one of the larger whales. Another
remarkable form is the Narwhal, in which the teeth are
reduced to a single long, twisted tusk, projecting forward
from the head to a length of six or seven feet. The pur-
pose of this twisted tusk is not certainly known.

Among the numerous fossil cetaceans, the most inter-
esting are the Zeuglodonts, a primitive group which serve
to connect the cetacea with the land quadrupeds of the
early Tertiary, especially with primitive carnivora or car-
nivorous insectivores. Altho marine, and fishlike in form,
the teeth and skull characters approach more nearly to
those of early carnivorous land mammals, from which
they were, no doubt, derived. They have been found in
the Eocene formations of Alabama, and, more recently,
in Egypt.

Among the living relics of prehistoric animals pre-
served to this day in the isolated southern continents, the
so-called Edentates are not the least interesting. The
tree-sloths are sluggish, stupid creatures, covered with

THE VERTEBRATES— IV. MAMMALS 153

long, greenish-brown hair, which inhabit the Brazilian
forests, hanging upside down from the trees by their long,
curved claws, feeding upon leaves, and moving slowly and
cautiously from bough to bough, and protected by their
likeness in color and appearance to the mossy-green,
lichen-covered branches around them. The armadillos are
covered by bony plates embedded in the skin, forming a
rigid buckler at each end of the body, with bands of
movable plates between, so that the animal can roll up into
an armor-covered ball. They are fossorial animals, active
diggers, and are found in all parts of South America, and
as far north as southern Texas. The anteaters, also
South American, are covered with long, shaggy hair,
toothless, with long snouts and slender, protrusible tongue,
and powerful claws to tear down the nests of the ants
on which they are especially adapted to feed. These
creatures are all of moderate size, the largest being the
Great Anteater, seven feet in length, including the long,
bushy tail. The term Edentates, or 'toothless animals,'
applies strictly to the ant-eaters only; the others have
teeth, altho they lack enamel. The living edentates are
the remnants of a race which flourished greatly in South
America during the Age of Mammals, while that region
was an island continent, protected by ocean barriers from
the incursions of the more highly developed mammals of
the northern world. Some of the extinct edentates, the
great Ground Sloths and Glyptodonts, attained gigantic
size. The Megatherium almost rivaled an elephant in
bulk, and was extraordinarily massive in skeleton; its
allies, the Mylodons, were somewhat smaller. These huge
animals were nearest to the tree sloths in structure, but
were much too large to have lived in trees. They are
supposed to have used their gigantic claws in digging up
and uprooting trees upon whose foliage they fed. The
Glyptodonts, or Tortoise-Armadillos, were covered with
armor, a massive solid carapace, without the movable
bands of the armadillo, and the feet hoofed instead of

154 ZOOLOGY

clawed. They had very efficient grinding teeth, and were
presumably grazing animals. Some of them equaled a
rhinoceros in bulk. Certain of these gigantic animals
appear to have survived in Patagonia almost to historic
time and to have been actually domesticated by the Indi-
ans of that region. The native legends tell of gigantic
animals which correspond — not very accurately — with the
Mylodon as it must have appeared in life; and in a cave
at Last Hope Inlet, in Patagonia, there were recently
found parts of the skin, well preserved and almost fresh,
together with droppings of the Mylodon, and chopped
grass, on which it is supposed to have been fed; the
" indications being that the animals were kept confined in
a part of the cave.

The Order Insectivora includes the Hedgehogs, Moles,
Shrews and many less familiar animals. The living In-

, sectivores are the scattered remnants of an ancient race
of mammals from whose earlier members were evolved
the higher and more intelligent races which have mostly
displaced them in the struggle for existence. The sur-
vivors are protected by spiny armor or nauseous taste
or by burrowing habits, or else inhabit remote fringes of

* the continents or large islands, where they have escaped
from the competition of higher types. All the insectivora
are small or minute animals, with teeth adapted to a diet
of insects, which form their principal food.

The best known of the insectivores are the hedge-
hogs, covered with a prickly coat, and, like the armadillos,
able to roll themselves up into a ball which defies the
assaults of any ordinary beast of prey; the moles, strictly
subterranean, and almost blind, the fore limbs converted
into very powerful and efficient digging instruments; and
the shrews, less specialized for burrowing, but protected
by their nocturnal habits and nauseous taste. Few birds
or animals will touch a shrew — the owl is almost the only
one that preys upon it. Hedgehogs, moles and shrews

THE VERTEBRATES— IV. MAMMALS 155

inhabit the northern continents, hedgehogs being restricted
to the Old World. Various other insectivores, more or
less related to these, but mostly less specially protected,
are found in South and West Africa, in the East and
West Indies, and in Madagascar, and one species, at least,
formerly existed in South America. In the early part
of the Age of Mammals the Insectivores were far more
numerous, and some of larger size, and they had not then

Fig. 33 — The Peba Armadillo.
An antique type of armored mammal inhabiting South America.

developed the various extreme specializations by which
the surviving members of the order have managed to
prolong their existence. The higher mammals, in the
opinion of Huxley, were probably derived from some of
these very primitive unspecialized Insectivores.

The Bats, Order Chiroptera, are usually regarded as
related to the Insectivores, but they are the most isolated

156 ZOOLOGY

and highly specialized of all mammals in relation to their
habits of flight. In adaptation to this purpose the fore
limbs, and especially the ringers, are greatly elongated, the
hind limbs reduced and slender, twisted around so that the
knee projects backward, and a thin, flexible wing mem-
brane extends from the sides of the body to the tips of the
fingers and from the front of the fore arm to the hind limbs
and usually to the tail. The pectoral muscles which move
the wings are greatly enlarged, as they are in flying birds.

The thumb and the five toes of the hind foot are tipped
with slender, curved claws by which the animal suspends
himself when at rest, generally hanging upside down. Dr.
W. L. Hahn, who has recently studied the habits of cave
bats, observes : "They have no nests, dens or fixed homes.
They have few enemies; consequently fear is little devel-
oped. About five-sixths of a bat's entire existence is spent
in a dormant condition; a large amount of fat is favorable
to torpor. In the caves, where conditions of light and tem-
perature are constant, bats come to the cave entrance at
irregular intervals. The length of time between these in-
tervals depends upon the amount of surplus fat stored in
the body.

"Food consists of insects that are caught on the wing.
Hearing and the tactile sense are chiefly relied upon to
perceive and locate food. Bats are more helpless on their
feet than most birds. In the air they have greater agility.
They can check their momentum very quickly. In flight
they can secure hold of a surface only slightly rough with
a single thumb or with one foot. Neither sight nor the
external ears are necessary for the perception of obstacles
during flight; such are perceived chiefly through the sense
organs located in the internal ear ; but the body hairs have
probably a sensory function as well. Perception is prob-
ably due to the condensation of the atmosphere between
the moving animal and the object which it is approaching.
It is difficult to explain how they find their way by means

THE VERTEBRATES— IV. MAMMALS 157

of the five senses familiar to us. The presence of a sixth
sense, that of direction, will explain all the facts, but it
has not been conclusively shown that such a sense exists."
There are two principal groups of bats. The large
Fruit-bats inhabit the East Indies, Africa and Madagascar,
Australia and many of the Pacific islands, feeding upon
fruit and hanging from branches of trees when not on the

Fig. 34 — Skeleton of a Bat, Showing Bones of Wing.
., radius; u., ulna; di., d2., d.3., d.4., ds., the five digits or
'fingers.'

wing. The smaller insectivorous bats are much better
known and are cosmopolitan in their distribution. The
ears are large and complex, and many kinds possess pe-
culiar leafy outgrowths from the nostrils which aid in
perception of objects around, somewhat as do the antennae
of ants, save that it is the sense of touch that is elaborated,
instead of that of smell. While most of them live on in-
sects, a few are frugivorous or carnivorous, and the South
American Desmodus, the true Vampire Bat, is a blood-

153 ZOOLOGY

sucker, fastening upon men or animals during sleep and
inflicting severe wounds, with serious loss of blood, with-
out awakening the sleeper, by means of its keen-edged
front teeth.

The cave-haunting habits of modern bats are familiar,
and their fossil remains have been found in ancient cave
and crevice formations as far back as the early part of the
Tertiary Period. All the extinct species are closely re-
lated to modern kinds and show nothing of the evolution
of this singular group of mammals. They are probably of
very ancient origin.

Next above the Insectivores in the scale of life may be
placed the Rodents, including the Rats and Mice, Squir-
rels, Porcupines, Rabbits, etc. This group of mammals,
altho comparatively low in scale of organization, is very
abundant and varied, and highly successful in the battle
of life. Their success may be ascribed to their great
fecundity, their adaptability to changing conditions of
life, and their readiness to combine together in social
relations, not generally very complex, yet each serving
to assist the others to a considerable extent. Whatever
be the reasons, the rodents are by far the most numerous
of the orders of mammals, both as to species and indi-
viduals. Nearly all are of small size. They are distributed
all over the world, a few even reaching Australia, and
are terrestrial, arboreal, fossorial or amphibious in their
habits. None of them is marine and none is able to fly,
altho some have membranous expansions of the skin which
can be stretched like parachutes in taking long, soaring
leaps from tree to tree. The limbs and feet are mostly
of primitive type, five-toed, tipped with claws, and the
animal walks on the sole of the foot. The teeth are pe-
culiar in the conversion of one pair of incisors in each
jaw into gnawing teeth, and disappearance of all the other
front teeth; the cheek teeth are adapted to crushing or
grinding. Rodents live mainly upon seeds, roots, nuts,

THE VERTEBRATES— IV. MAMMALS 159

fruits, or upon grasses or the bark of trees; but they are
by no means averse to insect or animal food.

More than half the living species of mammals belong
to this order. It is divided into four groups, of which the
squirrels, porcupines, rats and rabbits serve as types.

The squirrel group includes the squirrels, marmots,
beavers, pocket-gophers, and their allies. The arboreal
squirrels are the most intelligent and attractive of rodents,
and are found all over the world, save in Australia and
Madagascar. Their long, bushy tails, neat, smooth fur,

Fig- 35 — Skulls of Prairie Marmot (left) and Rabbit (right).
Illustrating the rodent type of teeth, with enlarged gnawing in-
cision. (Flower and Lydekker )

and often handsome coloring, and their restless activity
and chatter, offset their occasional depredations on birds'
nests. The marmots (woodchucks, gophers, prairie-dogs,
etc.) are nearly related to the tree squirrels, but terres-
trial and more or less burrowing in habit, adapted to
live in open country and in temperate or arctic climates.
The beavers are more distantly related; they are a small
group, of highly specialized habits, large-brained and in-
telligent for rodents. There are only two living species,
the European and American beaver. As is well known,
they live in colonies, in artificial lakes which they con-
struct by damming streams with logs, brush and mud,
each family making a nest or burrow in or beside the

160 ZOOLOGY

shallow waters of the pond, accessible by an underwater
entrance. Both species have been hunted almost to ex-
tinction for their fur. A large extinct relative of the
beaver, Castoroides, lived in North America during the
Glacial Epoch, equaling the black bear in size, but noth-
ing is known of its habits, except that its remains are
mostly found in ancient swamps and pond bottoms. Dur-
ing the Tertiary Period small animals related to the Beaver
(Steneofiber) were common both in Europe and North
America, but their habits were like those of the modern
prairie dogs. They constructed elaborate winding, cork-
screwlike burrows, and the remains of these burrows,
filled in by sand and petrified, are known in the West
as "Devil's Corkscrews." It is not easy to see how the
peculiar habits of the aquatic beavers could have evolved
from those of these burrowing ancestors, but they were,
perhaps, a side branch, not directly ancestral.

The pocket gophers and pocket mice of North America
are intermediate between the squirrel and rat groups of
rodents. They get their name from the large cheek-
pockets in which they carry food and transport earth from
their burrows. The pocket gophers are completely sub-
terranean, equaling the mole in their digging powers, but
living on vegetable food. The pocket mice are terres-
trial, and some of them active leapers. The jerboas and
their relatives are also specialized for leaping rather than
running, but are more nearly related to the rats and
porcupines than to the squirrels. They inhabit the north-
ern continents and Africa, mostly living in open plains
or desert regions.

The most abundant of the rodent groups are the rats
and mice and their relatives. These are found all over
the world ; a few have even penetrated to Australia, and to
various oceanic islands which few or none of the other
mammals have contrived to reach. They are nearly all
of small size, living upon all kinds of plant food, and

Manatee, Living Form of Once Numerous Species.

THE VERTEBRATES— IV. MAMMALS 161

often more or less omnivorous, adapting themselves very
readily to varying conditions of life and endowed with,
great fecundity. Their depredations upon crops, upon
stored grain, upon household supplies, the damage they
do by girdling trees for the edible inner bark, cause enor-
mous losses in various fields of human activity, so that
they rank with noxious insects in their economic impor-
tance. Birds of prey are their chief natural enemies,
more efficient in general than any artificial check on their
increase.

The porcupine group of rodents are represented by two
or three large, spiny-coated species in the northern con-
tinents, but their headquarters are in South America,
where they include the cavies and chinchillas, viscachas,
agoutis, capybaras, and many others, of which the largest,
the capybara, reaches the size of a pig. Quite a number
of this group of rodents inhabit Africa, and during the
Tertiary Period they were the only rodents in South
America, and one extinct genus is estimated to have at-
tained the size of an ox, much beyond that of any other
rodent.

The last group of rodents are the hares, rabbits and
picas, worldwide in distribution, but most familiar and
abundant in the north temperate and sub-arctic regions.
In Australia and New Zealand they have been introduced
by the white settlers, and have thriven and multiplied
exceedingly, so as to be a serious pest in the absence of
their natural enemies. Their limbs and feet are more
specialized for speed than in most rodents, altho the
rabbitlike cavies and chinchillas of South America show
a corresponding adaptation.

Under the name of Hoofed Mammals, or Ungulata,
are commonly grouped together several orders of mam-
mals which are not in fact nearly related to each other.
They are all herbivorous, adapted to terrestrial life, using

1 62

ZOOLOGY

the feet only for walking or running, and in all of them i
the claws have been thickened and broadened into hoofs,
serving for support, but useless for grasping or climbing.
So far as can be judged, they are derived from several
stocks of primitive clawed ancestors, in each of which

Fig. 36 — Fore Feet of Odd-toed Hoofed Mammals.
A., the tapir ; B., the rhinoceros ; C, the horse. The line of sym-
metry passes through the middle of the third digit. (After
Flower. J

the hoofs have been independently evolved in adapta-
tion to similar habits of life. The horses, tapirs and
rhinoceroses are derived from one primitive stock, the
pigs and ruminants from another, the elephants from a
third, while there are several extinct races of hoofed

THE VERTEBRATES— IV. MAMMALS 163

mammals derived from still other primitive stocks. The
Ungulates are all medium to large-sized mammals, many
of them gigantic, none of them very small. Their brains
are mostly of high type, and in intelligence they rank
with the Carnivora, decidedly above any of the orders
that we have considered, except the Cetacea, and ex-
ceeded only by the higher Primates (Monkeys, Apes and
Men). The two most important groups are the Perisso-
dactyls, or Odd-Toed, and Artiodactyls, or Even-Toed.
Hoofed Mammals. In the former the number of toes,
in the hind foot at least, is three or one, the axis of sym-
metry passing through the middle digit. In the latter the
number of toes is four or two, the axis of symmetry pass-
ing between the two middle digits. There are numerous
other points of difference in the structure of teeth, skele-
ton and soft anatomy, which show that these two groups
are distinct; that while animals so different as the horse
and rhinoceros are derived from a common ancestral
stock, the tapir and the pig, or the rhinoceros and the
hippopotamus, are derived from different primitive stocks
of placental mammals. These relationships are fully con-
firmed by what is known of the geological history of the
various races of ungulates. Owing to their large size and
comparative abundance, fossil hoofed mammals are more
common and better known than any of the other groups,
and the geological history and evolution of many of the
ungulate races is quite fully known.

"The Horse," wrote the small boy in his essay, "is a
square animal with a leg at each corner," a definition that
might perhaps be improved upon. But in fact the horse
needs no definition to bring it before the eye of man,
woman or child. Its graceful proportions, compact, well-
knit body, long head and arched neck, its flowing mane
and tail, its slender limbs and one-toed feet tipped each
by a broad, solid hoof — these are the ideal proportions
of the swift-running hoofed mammal, designed to cover
long distances at a high rate of speed.

164 ZOOLOGY

True horses are practically unknown in a wild state,
the so-called wild horses being, for the most part, de-
scended from animals which have escaped from domesti-
cation. The Przewalsky horse of the deserts of Central
Asia is, however, believed to be a truly wild species. The
closely related asses and zebras occur in the wild state
in Western Asia and in Africa ; they differ from the horse
chiefly in size and color pattern, and all are included in
the genus 'Equus.' In a broad way all of them may be
called horses.

The structure of the feet and teeth in the horse, using
the word in this broader sense, is unique among modern
animals. The foot has but a single toe, corresponding
to the middle or third digit of man, but the second and
fourth digits are represented by small rudiments, "splint-
bones," which lie closely pressed against the back of the
cannon-bone (corresponding to the third metacarpal bone
of the palm in the human hand or the third metatarsal
bone of the instep in the foot). These rudiments are all
that is left of the second and fourth toes; of the first and
fifth there is no trace at all.

The cheek teeth are equally peculiar. They are long,
square columns, growing at the base and pushing up from
the jaw as they wear off at the surface in grinding the
food. They are composed of enamel, dentine and cement;
the enamel, which forms the covering of the usual type
of mammal tooth, is infolded into a complicated pattern,
its worn edges supported on one side by the dentine which
underlies the enamel in the normal mammal tooth and on
the other by cement, a special substance slightly softer
than the dentine, deposited on what is at first the outer
side of the enamel before the tooth pushes up through
the gum. By this means the grinding surface of the
tooth at any stage of wear is composed of a complex
pattern of hard enamel ridges braced on either side by
the somewhat softer dentine and cement. This forms
a most efficient instrument for grinding and triturating the

166 ZOOLOGY

hard, dry grasses which are the natural food of the
horse.

In the successive formations of the Tertiary Period in
the Great Plains region of the Western United States
have been found a series of evolutionary stages leading
up to the modern horse from small ancestors no larger
than a cat, with four toes on the fore foot and three on
the hind foot, and with grinding teeth of the primitive
'bunodont' type, such as are still retained by man and
many other mammals. These little "four-toed horses"
are scarcely distinguishable from the contemporary an-
cestors of tapirs and rhinoceroses. The successive stages
of the divergent lines of evolution which led up into the
three widely different modern types have been found in
the successive formations of the American Tertiary.
About a dozen successive stages are known, nearly all
from complete fossil skeletons, besides numerous incom-
plete ones, which illustrate the gradual transition from
the little 'Four-Toed Horse' to his modern descendant. In
the Eocene the ancestors of the horse had four complete
toes in the fore foot, three in the hind foot, all resting
on the ground. In the Oligocene they had but three
complete toes on fore or hind foot, all resting on the
ground, but the side toes are slender and the middle digit
larger. The outside toe of their Eocene ancestors is
represented by a rudiment or "splint." In the Miocene
the central toe is more enlarged, and the side toes are very
slender and no longer touch the ground, but are like the
"dew-claws" of a dog or deer. In the Pliocene the side toes
are still more slender and the bones of the middle digit have
more clearly the proportions of those of a horse; and in
the Old World it is seen that there were already one-toed
horses, in which the dew-claws had disappeared. In the
Pleistocene Epoch all horses were one-toed like those of
to-day, and at that time there were species of wild horse
in Europe, Asia, Africa, North and South America. Since
that time the geographic range of horses has been much

THE VERTEBRATES— IV. MAMMALS 167

restricted. They disappeared wholly from the New
World, to be reintroduced by European settlers in North
and South America. They are no longer found in a wild
state in Europe, nor in most parts of Asia, and the zebras
and wild asses are rapidly disappearing. The domes-
ticated breeds, which are believed to be crosses of Asiatic,
North African and perhaps native European wild horses,
have been introduced everywhere that civilized man has
made his home; and feral races, escaped from domestica-
tion, have repeopled the high plains of both Americas.

The evolution of the Horse is to be regarded as an adap-
tation to changing conditions of climate and geography
which favored more and more the development of swift-
running types in open grassy plains. At the beginning
of the Tertiary Period the plains of Western America lay
near to sea-level, had a moist sub-tropical climate, and
were heavily forest-clad. Throughout this period they
were being slowly elevated above sea-level, the climate was
becoming colder and more arid, and the forests were dis-
appearing, to be replaced by extensive grassy plains. Of
the original population of animals some retreated south-
ward with the changing climate, and their descendants
are to-day to be found in the tropical forests. Some be-
came extinct, and are known to us only from their fossil
remains. Some, like the horses, were able to adapt them-
selves to the changing conditions, and their descendants,
much changed in form and habits, still survive. Hand in
hand with the changes in foot structure adapting them
to swift running, went changes in the teeth adapting them
to feed upon the hard, dry upland grasses. The steady
increase in size is a common feature in many races of ani-
mals, especially of ungulates.

The Tapirs afford an example of a race which has fol-
lowed the climate southward instead of altering its habits,
and structure. Tapirs to-day inhabit the forests of tropi-
cal America and the Malayan peninsula. They retain the
primitive construction of the feet, four toes in the fore

168 ZOOLOGY

foot, three in the hind foot, and their teeth are not greatly-
changed from the primitive type of the Eocene ancestors
of horses, tapirs and rhinoceroses. Except for increased
size and bulk and the development of a short flexible
proboscis they have changed but little. During the early
part of the Tertiary Period tapirs inhabited all the north-
ern continents, but their range was gradually restricted
further and further to the south.

The history of the Rhinoceroses is much the same as of
the Tapirs. In the early Tertiary their ancestors had
four toes on the front foot, three on the hind foot, and
primitive short-crowned 'bunodonf teeth. Like the early
horses, these ancestral rhinoceroses lost the outer digit in
the fore foot, and began to" lengthen out the crowns of
the teeth, making them more efficient grinders. But they
got no further than these first steps, and then, like the
Tapirs, they followed the changing climate southward, in
preference to adapting themselves to new conditions of
life. Rhinoceroses were common in Europe, Northern
Asia and North- America* as far north as Canada during
the early and middle Tertiary, but by the end of the Ter-
tiary they had disappeared from the northern regions, ex-
cept for a few survivors in Europe and Asia; and to-day
they are found only, in the tropical regions of the Old
World, in India and some of the East Indian islands, in
Africa as far south as Cape Colony. In the New World
they have become wholly extinct.

Other races of the early Perissodactyls have become en-
tirely extinct. Such were the Titanotheres of Tertiary
North America, huge, massive rhinoceros-like animals
with humped back like the bison, and paired bony horns
at the front of the solidly built skull; the Palaeotheres of
the European Tertiary, smaller, hornless, tapir-like in size
and proportions, but with only three front toes ; and most
peculiar of all the Chalicotheres, an odd combination of
horse and rhinoceros in proportions, but with the hoofs
reconverted into large, powerful claws, used probably to

THE VERTEBRATES— IV. MAMMALS 169

dig around trees and uproot them in order to feed upon
their foliage.

In reviewing the historical development of the Perisso-
dactyls it must be deemed an order that has passed its
prime and is tending toward extinction. It was repre-
sented during the Tertiary Period by a great number and
variety of members, both small and large. Its living rep-
resentatives are few in number, of large size, scattered,
widely diverse in form and habits, and, except for the
horses, confined to tropical regions. Even the horses,
the most successful in adapting themselves to modern con-
ditions of life, do not appear to maintain themselves in
competition with their numerous and varied rivals of the
ruminant group, which are by far the most abundant
among modern hoofed mammals.

The order Artiodactyla includes two principal groups,
first the non-ruminants (pigs, peccaries and hippopotami),
with the primitive bunodont type of teeth and with four
separate digits in each foot, altho the side toes are some-
times much reduced; second, the ruminants (camels, deer,
antelopes, sheep and cattle), in which the cheek teeth are
adapted for grinding, altho with a wholly different pat-
tern from the grinders of horses or rhinoceroses, and there
are only two complete digits on each foot, the meta-
podials of which are fused into a single "cannon bone,"
altho the toes remain separate, and the side toes are rudi-
mentary "dew-claws" or altogether absent. The first
group retain more nearly the ancestral characters of teeth
and feet, and have survived owing to certain unusual
habits of life or special means of defense which have pro-
tected them against competition. The second group is the
progressive and dominant group of herbivorous mammals.

The pigs of the Old World and the Peccaries of the
New are provided with bristly hair, thick skin, and very
efficient canine tusks. They are compact-bodied, bold and
active fighters, dangerous adversaries whom their car-
nivorous enemies or herbivorous rivals may well hesitate

170

ZOOLOGY

to attack. Nevertheless, their rangs and numbers have
been much decreased since the Middle Tertiary. Several
large kinds of peccary inhabited North America as far
north at least as the Canadian border up to the Pleistocene
Epoch ; there is now but a single genus which ranges from

w m

iff

TVM

B C

Fig- 37 — Even-toed Hoofed Mammals.
the pig: B., the deer; C, the camel. Note that the axis of
symmetry of the foot lies between the third and fourth digits.
(Flower.) In the pig the side toes are complete ; in the
deer only dew-claws remain ; in the camel they have wholly
disappeared.

Southern Texas to Brazil. In Europe there were also a
number of true pigs, some of large size, during the later
Tertiary; the wild boar is the only surviving type in tern-

THE VERTEBRATES— IV. MAMMALS 171

perate regions, but in tropical Africa and the East Indies
there are several others, the Wart-Hog, Red River Hog,
Babirussa and a number of species of pigs. The pigs, like
the tapirs and rhinoceroses, have followed the tropical
forest and climate southward in its gradual disappearance
from the temperate zone.

The Hippopotamus is among the largest of living quad-
rupeds, thick-skinned, almost hairless, its broad, short feet
with four toes of nearly equal size, its huge jaws and long,
heavy tusks adapted to root in the mud of river bottoms.
Chiefly aquatic in its habits, it can remain under water for
some time before coming up to breathe. It is found to-
day only in the rivers of Central Africa, but had formerly
a much wider range, inhabiting Madagascar and Southern
Asia and ranging northward into Europe.

Nine-tenths of the hoofed animals belong to the Rumi-
nants, a section of the Artiodactyls. They are distin-
guished especially by the peculiar complexity of the stom-
ach which enables them to chew the cud. It is divided
into four chambers, the first and largest, or paunch, serv-
ing to contain the hastily swallowed food, which is later
returned to the mouth, thoroly masticated at leisure,
and passes to the other divisions of the stomach for di-
gestion. The advantage of this habit of "chewing the
cud" to an herbivorous animal whose food requires thoro
chewing are very considerable. Food can be obtained
hastily where rich and plentiful, while the necessary
mastication can be continued while en route from the feed-
ing grounds or during rest, or deferred till a place of
safety is reached. The limbs and feet of ruminants are
highly specialized both for speed and endurance, almost
if not quite as much as in the horse, while the "divided
hoof" — really two separate hoofs closely paired — gives
them a better footing on rough or irregular ground.

Among living ruminants the camels and llamas stand
apart as a primtive and peculiar race, specialized for
desert life. The long, loose-jointed limbs and padded feet

172 ZOOLOGY

lack the speed adaptation of the higher races, but are well
fitted to traverse the loose desert sand; the stomach is
less complex but peculiarly specialized to carry a supply
of water which enables the animal to go without drinking
for several days at a time. Altho the camels are now
found only in the Central Asian and North African deserts
and the llamas in the arid regions of South America, they
were during the Tertiary period a peculiarly North
American family, and the evolution of the race has been
traced almost as completely as the evolution of the horse,
back to little ancestors no larger than a cat, with four
separate digits on each foot. They disappeared from
North America before the appearance of civilized man,
like the native American horses, and the preservation
of camels in the Old World is perhaps, like the preserva-
tion of the Asiatic Horse, due to their being domesticated
by man. It is doubtful whether any truly wild camels
exist either in Asia or Africa. If these domesticated
races be set aside it will be found that camels and horses
have both disappeared from the northern continents,
where they were abundant during the Age of Mammals,
but are preserved in the outlying southern continents, the
peculiarly American camels in South America, the cos-
mopolitan horses in Southern Africa. Looking at the
matter in this way, it may reasonably be supposed that
they were driven into the outlying southern regions
through their inability to contend with the more perfected
ruminants whose center of dispersal was in the great
northern land mass. Both camels and llamas have been
domesticated by man and used as beasts of burden; the
Bactrian or two-humped camel in Central Asia, the
dromedary in North Africa; the llama was the only beast
of burden in ancient Peru, while the smaller alpaca was
kept for its fleece and meat. The wild races of these two
species still exist in the high plains of South America un-
der the names of guanaco and vicuna.

Before taking up the typical ruminants, or Pecora, al-

THE VERTEBRATES— IV. MAMMALS 173

lusion may be made to the chevrotain of the dense forests
of the East Indies, and the water-chevrotain of the equally
dense forests of West Africa, both regions the refuge of
many primitive survivors of the Tertiary fauna. These
two genera are grouped together because of the less per-

Yig. 38 — The Water-Chevrotain of West Africa.
Primitive type of the Ruminants. (Flower and Lydekker.)

fected foot-structure and lack of horns, and represent
quite nearly the early Tertiary stage in the evolution of
the ruminants, as it is found fossil in Europe and North
America.

The true ruminants or Pecora are undoubtedly the domi-
nant group of herbivora to-day. They are a group of
comparatively recent evolution geologically, and first ap-

174 ZOOLOGY

pear in the Middle Tertiary, developing out of primitive
artiodactyls mainly in the Old World. Their center of
diffusion was apparently Northern Asia, whence they
spread to Europe on one hand, to North America on the
other, reaching Africa and South America at a later date,
probably toward the end of the Tertiary period. They in-
clude three main sections; first the Giraffes, in which
the horns are bony excrescences covered with a skin-pad;
second the Deer, in which the horns (antlers) are covered
with a skin-pad (the "velvet") only when newly formed,
and are shed annually; third, the Antelopes, Sheep and
Cattle, in which the horn cones are covered with a heavy,
solid and tough true horn, which is permanent during the
lifetime of the animal.

The Giraffes may be regarded as the most primitive of
these three sections. They are to-day limited to Africa,
the giraffe being adapted to the semi-desert plains, where
its long neck enables it to feed upon the succulent upper
foliage of mimosas and other thorny bushes ; while its ally,
the recently-discovered Okapi, inhabits the deep forests
of Central Africa. Fossil giraffes have been found in
the late Tertiary of Asia and Southern Europe, and nearly
related forms in India (Sivatherium, etc.) were of greater
bulk altho not so tall, and had the horns much larger and
more branched.

The deer are especially adapted to forest life, the teeth
short crowned and suited for browsing. They inhabit
all the forest regions of Europe, Asia, North Africa and
the two Americas, but have been prevented from reaching^
the Ethiopian region by the wide stretch of the Saharan
desert and the arid mountainous country to the east of it.
The largest and most progressive of the deer are found,
as one might expect, in the Arctic and cold temperate
zones of the North, the wapiti and red deer, the reindeer
and caribou, the moose and (European) elk being the
highest development of the family. The smallest and most
primitive members live in Southern Europe, in South-

THE VERTEBRATES— IV. MAMMALS 175

eastern Asia, the East Indies and in Central and South
America. The earliest deer were of small size, at first
hornless, like the modern musk deer of the Himalayas and
water-deer of China, or the fawn of any of the larger
deer; then with a single spike, like the Central American
"brockets," or the second year of the larger deer (to which
the term brocket originally belonged) ; then with two,

Fig. 39 — Heads of Deer and Gazelle, Showing the Antlered
and Hollow-horned Types of Ruminant. (Sclater, Brooke.)

three or more times, all the stages being paralleled both by
the adults of different species of modern deer and by the
annual changes in the young of the larger northern deer.
The antelopes, sheep and cattle are primarily adapted
to living on open plains. The teeth are mostly long-
crowned, and in many of them the grinding edges of the
enamel are braced by a heavy deposit of cement, as in the
horses. They are thus suited to feed upon the hard, dry
plains grasses, which require very thoro chewing be-

176 ZOOLOGY

fore their nutrition becomes available. "Antelopes" is a
broad term that covers all the various races except two —
the sheep and goats, and the cattle — which on account of
their domestication by man are of especial importance
and have received especial names. From the zoological
point of view they are not more different from antelopes
than the different races of antelopes are from each other.
But they may fairly be considered as the highest and
most progressive of the various antelope groups.

The antelopes are to-day most abundant and varied in
Africa. In Europe and Asia, where they were numerous
during the later Tertiary, they have been mostly dis-
placed by the sheep and oxen, but are still found in large
numbers in India, in Arabia and Syria, and a few in the
more central parts of Asia. Except for one or two little
known extinct species, they do not appear ever to have
reached the New World; the so-called Antelope (Prong-
horn) of the Western plains is a solitary survivor of a dis-
tinct race intermediate between deer and antelopes in its
affinities and especially characteristic of North America.

The smallest antelope is the little Madoqua or Pigmy-
antelope of East Africa, no larger than a hare. Not much
larger are the Duikerboks (Cephalophus) of South and
East Africa, so called from the dexterity and quickness
with which they "duck" or dive into the tall grass or
bushes to escape from their pursuers. In these the horns
are small, straight spikes. The gazelles, with longer,
ringed horns, delicate head with large, soft eyes, slender
neck and long limbs, are generally admitted to be the most
graceful of the hoofed quadrupeds and unsurpassed in
speed. In the larger antelopes the horns are either ringed
or spirally twisted, mostly projecting upward with a slight
backward curve, but in the gnu they are depressed on the
side of the head, as in the sheep. Some of the larger
antelopes, such as the African eland or Indian nilghai,
have nearly the size and proportions of domestic cattle.

The goats, sheep and cattle are the latest of the ante-

THE VERTEBRATES— IV. MAMMALS 177

lope groups to appear in geological history, and the wild
species are to-day predominantly Asiatic in their dis-
tribution. The cattle, however, are widely distributed
throughout Africa, India and the East India islands, and
in North America are represented by the bison and musk-
ox. The big-horn and mountain goat of northwestern
North America are the only New World representatives
of the sheep and goats; a single species of wild sheep is
found in North Africa; otherwise they are all Palsearctic,.
a few, such as the Ibex and Chamois, inhabiting the moun-
tainous regions of Europe, most of them the highlands of
Asia. While the cattle are especially plains and lowland
types, the sheep and goats are preeminently mountain
dwellers, active climbers, sure-footed, and able to endure
severe cold. The domesticated species of cattle, sheep and
goats are of enormous economic importance, and have
contributed very largely to shaping the development of
Old World civilization.

Besides the ancestors of the modern pigs and ruminants,
there were various races of this order of hoofed animals
that have not survived. The Elotheres were large ani-
mals with huge skulls, cheek teeth like those of pigs, front
teeth more like carnivorous mammals, feet strictly two-
toed as in camels and ruminants, but the metapodials not
united into a cannon-bone. They inhabited the northern
continents in the middle part of the Tertiary period. The
skull of the largest of them, 'Dinohyus,' is over three
feet long, the animal as large as a hippopotamus but with
much longer legs and short, massive body proportioned
more like the bison. The Oreodonts, very abundant in
North America at the same time, have been called "rumi-
nating hogs," as they combined the four-toed feet of the
pigs with a ruminating type of teeth. They must have
resembled peccaries in appearance and habits, but with
shorter snout. The contemporary Anoplotheres took the
place of the Oreodonts in the Old World; the Anthra-
cotheres, pig-like in proportions, with teeth partly inter-

178 ZOOLOGY

mediate between those of pigs and ruminants, are regarded
-as more or less directly ancestral to the hippopotamus.

The Elephants are the most gigantic of living quadru-
peds and the most singular in appearance. The elongation
of the snout into a long, flexible trunk, serving much the
same purposes as the hands in man, sets them apart from
all other ungulates as, in this respect at least, a higher
mechanical adaptation. For there can be no doubt that
the development of the hand into an effective organ of
prehension, released from the functions of locomotion, has
played an important part in the evolution of intelligent life
in man ; and in the elephant we see an entirely different or-
gan serving the same purpose almost as effectively. To
find the elephant ranking as the most intelligent of hoofed
animals, then, is what might be expected. The limbs are
long, straight and massive, the feet short, rounded, heav-
ily padded, with five small hoofs on each. This construc-
tion is best adapted to support the gigantic weight of the
"body — five to fifteen thousand pounds — and all very large
land animals approach it more or less nearly.

The teeth are very highly specialized. One pair of
tipper incisors is enlarged and lengthened into tusks; all
the other front teeth have disappeared. Of the cheek
teeth only the molars remain, and these are high crowned,
composed of alternating transverse plates of enamel, den-
tine and cement. The three molars come into use one
after another, dropping out as they wear down to the
roots, and in a fully adult elephant only one grinding
tooth is left on each side of upper or lower jaw. Four
grinders and two tusks constitute the entire adult denti-
tion, and even the tusks are absent in the female. The
skull and jaws are extremely short, and large in propor-
tion, giving room for the attachment of the powerful
muscles necessary to wield the trunk and tusks and grind
the food — leaves, twigs, fruits and forest grasses. Un-
like other long-limbed animals (excepting man) the neck

THE VERTEBRATES— IV. MAMMALS 179

is very short, as the trunk makes it unnecessary for the
head to reach the ground.

The average height of elephants is from eight to ten
feet, but the African species at least, sometimes reaches-
twelve feet in height. Jumbo was eleven feet high, his
weight six and a half tons. The Indian species is more
massive, but not so tall as the African one ; its forehead is
higher and grinders larger, with more numerous and
closely set plates; the tusks are smaller and often absent
in males as well as females.

Elephants have been tamed since the days of the an-
cients, both the Indian and African species. Those
brought by Hannibal from Carthage must have been
African elephants ; but the Greeks and Romans were more
familiar with the Indian species.

The two modern species of elephants are the last sur-
vivors of a race widely distributed in prehistoric times.
The mammoths were simply a species of elephant; the
mastodons were a nearly related genus, but with shorter
crowned and more numerous teeth, and other primitive
characters. These during the Pleistocene epoch ranged
over all the northern continents. Mammoth remains have
been found in all parts of Europe and in Asia northward
to the Liakhof Islands in the Arctic Ocean, where vast
quantities of their tusks and bones are preserved in the
frozen soil. In America the mammoths of different spe-
cies ranged from Siberia to Mexico. The Mastodons
were of even wider range, penetrating into South Amer-
ica as far as the Argentine plains. The Arctic species of
elephants were covered with a shaggy coat of reddish
brown wool, mingled with longer black hairs. In Siberia
and Alaska carcasses of these animals more or less com-
plete have been found preserved in the frozen soil. The
southern mammoths were more probably naked-skinned
like the modern elephants, which they somewhat exceeded
in height and bulk. A skeleton in the Paris Museum is
slightly over three meters (thirteen feet) in height. The

180 ZOOLOGY

mastodons were also partly covered with hair. The tusks
in some of these mammoths and mastodons were of enor-
mous size, curling inward and crossing at the tips. Some
of these fossil tusks measure thirteen feet in length and
nine inches in thickness. Like the tusks of modern ele-
phants they are composed of ivory or dentine only, the
enamel being lacking.

During the latter half of the Tertiary Period Primitive
Mastodons (Gomphotherium) inhabited Europe, Asia and
North America. They were much smaller than the Pleis-
tocene Mastodons and Elephants, with tusks in both up-
per and lower jaws, and shorter limbs, longer skull, and
much shorter trunk. The lower tusks are short and
straight, or in the earliest forms curving slightly down-
ward, and with a strip of enamel on the face of the tusk.
In a related genus, 'Dinotherium/ the upper tusks were
absent, the lower ones large and curving downward; and
in this animal the grinding teeth were more numerous, five
on each side of each jaw, while the 'Gomphotherium/ like
the true Mastodon, had but three.

A complete series of intermediate stages between the
Primitive Mastodons and the modern elephants is found
in the successive formations of the later Tertiary in
Europe and Asia. The early history of the Proboscideans
was unknown until very recently, when the explorations
in the Fayum district of Egypt disclosed an early Tertiary
fauna which included, among other large quadrupeds new
to science, the early stages in the evolution of mastodons
and elephants. These carried back the ancestry of the
elephant to a small animal (Mceritherium) about as large
as a cow, with a nearly complete series of teeth, short
crowned grinders, one pair of incisors, enlarged and some-
what like the gnawing teeth of rodents, with long head,
no trunk, and short limbs. Palaeomastodon was inter-
mediate between this type and the primitive mastodons.

Reference has been made to the various extinct relatives
of the Perissodactyls, Artiodactyls and Proboscideans.

THE VERTEBRATES— IV. MAMMALS i8r

But during the Age of Mammals there were a number of
groups of hoofed mammals not related to any of the living
orders, and some of remarkable proportions and gigantic
size. In North America, during the Eocene epoch, lived
the 'Uintatherium' or 'Dinoceras,' a huge creature larger
than an Indian rhinoceros, with elephantine limbs and
feet, its head armed with three pairs of bony horns and
great, saber-like upper tusks. In Africa, about the same
time or a little later, lived the 'Arsinoitherium,' equally
huge and elephantine in limbs and feet, and with a pair of
great, sharp horns at the front of the skull. South Amer-
ica, during the long period that it remained an island
continent, developed a great variety of hoofed mammals,,
unrelated to those of the northern continents, but some-
times paralleling them to a remarkable extent. In the
South American Eocene is found a great elephantine quad-
ruped, the Tyrotherium,' singularly like the ancestral
mastodons in many respects, but probably not closely re-
lated to them. In the Miocene lived another huge beast,
the 'Astrapotherium,' again with elephantine limhs and
feet, and apparently provided with a shorter trunk; but
with tusks like those of pigs and peccaries only of larger
size, and with grinding teeth that bear a general resem-
blance to those of the rhinoceros. At the same time
lived smaller animals, the 'Nesodons/ proportioned some-
what on the lines of a small hornless rhinoceros, and little
Typotheres, rabbit or coney-like in size and proportions,
but in fact related to the Nesodons.

The most interesting members of this Miocene fauna of
South America were the Litopterna, some of which par-
alleled the horses in their foot-structure with extraordi-
nary closeness, altho not at all horse-like in the skull or
teeth. The side-toes were reduced to "dew-claws" as in
the later three-toed horses, and finally disappeared, leaving
only the central toe with a rudimentary nodule of bone
to represent each side toe, like the splint of the modern
horse. The form of the foot bones throughout becomes

i82 ZOOLOGY

singularly like that of the true horses. Other Litopterna
retained three well-developed toes like the rhinoceroses,
but their limbs had rather the shambling build of the camel
than the more compact proportions of rhinoceros or tapir.
At the end of the Tertiary still other gigantic ungulates
developed in South America. The Nesodons gave rise to
the huge massive 'Toxodon/ exceeding a rhinoceros in
size; the three-toed Litopterna to the camel-like 'Macrau-
chenia.'

All these extinct groups of Ungulates were evolved in
North America, in South America and in Africa during
epochs when these regions were cut off from the main
center of diffusion of mammals, the great land mass of
Northern and Central Asia. The corresponding forms
evolved in this larger central region were subject to
severer and wider competition, were more advanced, in-
telligent, active or hardy than the quadrupeds evolved in
the smaller isolated areas. Consequently, when these areas
were joined to the central land mass, its fauna invaded
them and swept out of existence all the competing autoch-
thonic types.

The Manatee and Dugong are the remnants of a group
of herbivorous mammals, nearly related to the ancestors
of the elephants. Like the Cetacea, they have adopted
an aquatic life, and become more or less fish-like in form,
losing the hind limbs, developing the tail into a swim-
ming organ, and the fore limbs into fin-like paddles, and
entirely losing the hair. Unlike cetaceans they are slug-
gish, slow-moving bottom feeders, living on the aquatic
vegetation of tidal rivers or upon sea-weeds. The Dugong
■of the Rea Sea and East Indies, and the Manatee of the
Atlantic coasts are the only survivors. A larger form,
Steller's Sea Cow, inhabited some of the Aleutian Islands
until 1758; and in the Tertiary formations of Europe and
North Africa various ancestral stages have been discov-
ered. The name Sirenia may seem singularly inappro-
priate for such peculiarly ugly animals, yet it is not

THE VERTEBRATES— IV. MAMMALS 183

unlikely that some of the older reports of mermaids were
based upon the dugong, owing to the custom of the parent
holding the young to her breast with her flippers, the
round heads of both being raised out of the water.

The 'Carnivora' are the Beasts of Prey, specially adapted
for flesh-eating and predaceous habits. For the most part
they are exceptionally active, strong and restless, of high
intelligence and perfect bodily mechanism. In so far as
perfection consists in mechanical adaptation to an active
and varied life, the carnivora may indeed be regarded as
the highest of living animals. Man indeed, in respect of

Fig. 40 — The Florida Manatee. (Flower and Lydekker.)

his mental powers, stands far above the rest of creation,,
but as an all-round athlete he must yield the palm to the
Carnivores.

Besides the land carnivora this order includes the Seals
and Walruses, adapted to a marine life, and again par-
tially assuming a fish-like form, altho they have retained
their furry covering, and in the absence of a heavy tail
the hind limbs have been converted into a propelling organ,
instead of disappearing as they have done in cetaceans or
sirenians. The fore-limbs are converted into flippers, and
the teeth mimic those of the early toothed whales in their
adaptation to fish-eating. But seals and walruses are not
as helpless on land as are dolphins or whales ; their adap-
tation to marine life is not so complete. The great "rook-

184 ZOOLOGY

-eries" in which seals congregate for breeding purposes,
and the long migrations which they undertake each season,
are remarkable features of their life.

The terrestrial carnivora are more numerous and fa-
miliar. Their teeth are specialized for seizing their prey
and for cutting flesh. The canine teeth are large, sharp
and strong, one pair of cheek teeth is enlarged and con-
verted into stout shearing blades which act like a pair of
scissors; these are termed carnassials, and the cheek teeth
in front of them are usually of cutting type, while the
molars behind are used for crushing or are entirely ab-
sent. The feet have either four or five digits, the claws
usually sharp and sometimes retractile, so that they can
be drawn back out of the way while walking and extended
only in seizing their prey. They walk either upon the en-
tire sole of the foot or upon the under surface of the toes,
the sole or palm being held free of the ground; but never
upon the tips of the toes, as do the hoofed animals. Most
of the carnivora are good climbers; some live mostly or
altogether in trees. All of them are of high intelligence
and keen perceptions, the senses of sight, smell and hear-
ing very highly developed. They are divided usually in-
to seven families:

i. 'Canidae' — Dogs, wolves, foxes and jackals. Partly
omnivorous, adapted to swift running and very often
hunting in packs. Cosmopolitan.

2. Trocyonidae' — Raccoons, omnivorous and arboreal.
Found only in the New World.

3. 'Ursidse' — Bears, omnivorous, terrestrial, and all of
large size. Cosmopolitan except Australian region.

4. 'Mustelidae' — Weasels, martens, skunks, badgers and
otters. Mostly predaceous and of small or medium size,
found everywhere except in the Australian region.

5. 'Viverridae' — Civets, mongooses, etc. Mostly pre-
daceous and of small or medium size, confined to the Old
World exclusive of Australasia. The few species of Car-
nivora in Madagascar all belong to this family.

THE VERTEBRATES— IV. MAMMALS 185

6. 'Hyaenidse. — Hyenas. Predaceous and of large size,
found only in Africa and Southern Asia.

7. 'Felidse' — The cat family, including the lion, tiger
and various smaller cats. Strictly predaceous, large or of
medium size. Cosmopolitan except Australasia.

The dog family are more adapted for speed than any
other carnivora, and the larger species often hunt in
packs and run down their prey in the open. They are
equally expert in tracking their prey, the sense of smell
being very highly developed. Unlike mcst carnivora, the
claws are blunt and are used only for locomotion ; and they
are quite unable to climb trees. Their range extends from
the Arctic regions to the equator, and southward to Pata-
gonia and the Falkland Islands. The true wolves and
foxes are mostly found in the northern continents; the
jackals are Oriental and African; while the South Ameri-
can canids belong to a somewhat primitive group known
as dog-foxes. The dingo is the only member of the car-
nivora which has entered Australia, but whether intro-
duced by primitive man or naturally is not certainly
proven. All of the family are much alike in structure,
-differing mainly in size, color and habits. They are all
included in the genus Canis except four or five species
inhabiting India, Africa and South America.

The Raccoons of the New World are more or less re-
lated to the dogs, but arboreal, forest-living, nocturnal and
omnivorous. The "coon" has a well-deserved reputation
for cleverness and cunning, qualities shared by the less
known members of the family, the coati, caxomistle and
kinkajou of the Central and South American forests. The
last-named is the most strictly arboreal of the carnivora;
its tail prehensile like the monkeys, which it resembles
in habits and food.

The Bears are the largest of the carnivora. They are
omnivorous, or rather frugivorous, feeding mostly upon
roots and berries. They are long limbed, almost tailless,
walk upon the sole of the foot, and the large, sharp claws

i86 ZOOLOGY

are used in digging out roots, bulbs, insects and honey,
of which last they are extremely fond. Their main sub-
sistence in the summer is upon berries. In the north they
hibernate through the winter season of scarcity and cold,,
coming out in the spring hungry and ravenous, ready to
seize and devour anything they can find. In general,
however, bears are easy-going, good-natured animals,
rarely attacking man, and generally doing their best to
escape when attacked, dangerous only when cornered or
wounded, when hungry, or when their cubs are endan-
gered. Perhaps an exception should be made of the
Polar bear, which is entirely carnivorous, living upon
seals, fish, or occasional land animals, and correspondingly
savage in temperament.

The bears are chiefly a northern race, but are found
in India and the East Indies, in Algeria and in the Andes
mountains. The largest species are the huge Kadiak
bears of Alaska ; the polar bear is almost as large.

The weasel and civet families are mostly small but
bloodthirsty and fierce beasts of prey, with long tails,
rather short legs, and usually slender "vermiform" bod-
ies. Most of them are terrestrial or partly arboreal, but
the weasel family includes also fossorial (badgers) and
semi-aquatic types (otters). The largest member of the
Mustelidae is the Glutton or Wolverene of the boreal zone
in both Old and New World. The Old World Viverridse
are chiefly found in the Oriental region and in Africa;
two or three have reached Madagascar, where they are the
only carnivorous animals. The Mustelidae, on the other
hand, are more northern in their distribution, altho found
in all the great continents except Australia.

The Hyenas are large Old World carnivores related to
the civets, but living in more open country and preying
upon larger game. They are commonly called carrion-
eaters, but are in fact more like the dogs, tracking and
running down live prey or feeding upon carcasses, pretty
much as opportunity offers. They are, however, gross

THE VERTEBRATES— IV. MAMMALS 187

and indiscriminate feeders, contrasting in their manner
of eating with the more dainty habits of the cats; and the
teeth are massive, heavy, usually much worn on the edges.
They now inhabit India, Southwestern Asia and Africa,
but formerly ranged all over the northern parts of the
Old World, never having reached the New. Teeth and
bones of hyenas and their prey are the most abundant fos-
sil remains in the "bone-caves" of England and Northern
Europe.

The Cats are the most strictly predaceous group of car-
nivora. They are especially distinguished by the retrac-
tile claws — but the claws are slightly retractile in some of
the Viverrids — and the teeth are sharper, the shearing
action of the carnassials more perfect, the crushing teeth
more reduced than in any of the other families. The
limbs, especially the fore-limbs, are very flexible and pow-
erful, and they afford perhaps the finest mechanical adap-
tations for combined strength and agility to be found in
the whole animal kingdom. Altho capable of great speed
for a short spurt, they are not able to maintain it over
long distances; they never run down their prey, but track
or lie in wait for it and spring upon it unawares. If they
fail to overtake it in the first few bounds they abandon the
chase. Cats are all dainty eaters, and among the thou-
sands of skulls in large museum collections it is rare to
find one with the teeth much worn, except among the des-
ert species, which must needs encounter considerable loose
sand with the food. It is not true, however, that they
will not devour an animal which they have not themselves
killed.

The largest cats are the lion and tiger, the one inhabit-
ing Africa and Southwestern Asia, the other India and
Eastern Asia. The lion is especially an inhabitant of
desert or arid countries, and his color matches his sur-
roundings ; the brilliant vertical stripes of the tiger are
said to be equally effective for concealment in the deep

188 ZOOLOGY

jungles and forests of Southeastern Asia. Both are
mainly nocturnal in their habits, as are all the cats.

In the New World, the puma and jaguar correspond to
the Old World lion and tiger, but are of smaller size, not
exceeding the leopards of the Old World. The lynxes or
bob-tailed cats are especially boreal in range, inhabiting
the arctic and cold-temperate regions of the northern con-
tinents. Various other smaller cats range down to the size
of the domestic species, inhabiting all the continents ex-
cept Australia.

During the latter part of the Tertiary Period lived va-
rious carnivora, ancestral or related to the modern kinds.
Perhaps the largest of them are the Amphicyons, related
to the dogs but equaling the largest bears in size, and ap-
parently similar to them in habits. Unlike bears, they
were provided with extremely long and heavy tails, ex-
ceeding those of the great cats, while the limbs were rather
short.

But the most remarkable of the extinct carnivora are the
Saber-toothed Tigers or 'Machaerodonts,' related to the
true cats, and similar to them in general proportions and
habits, but with the upper canine enlarged into a great
compressed fang, slightly curved and with sharp, serrate
edges. The jaws were peculiarly loose-hung and could
be opened wide enough to allow full play for the action of
the tusks, and powerful muscles at the back of the skull
enabled the animal to drive them down with tremendous
force into the body of an enemy. The legs were short,
the muscles exceptionally heavy and powerful. In all re-
spects the Saber-toothed tigers appear to have been es-
pecially adapted to prey upon large, thick-skinned, slow-
moving quadrupeds. The largest species equalled a
grizzly bear in size, the smallest were about as large as
a lynx.

In the earlier part of the Tertiary Period there were
numerous kinds of carnivores, with much smaller brains
than the modern kinds and more primitive in various re-

THE VERTEBRATES— IV. MAMMALS 189

spects. These are grouped in a distinct sub-order, Creo-
donta. Some of them were ancestral to the various fami-
lies of modern carnivores ; others have left no descendants.
In habits and general appearance these extinct races were
much like modern beasts of prey, but the various peculiar
features of the several modern races are found in different
combinations.

The order Primates includes Lemurs, Monkeys, Apes
and Man. In this order are the animals of greatest
interest on account of their near relationship to the human
race. Cuvier, it is true, placed Man in a separate order
of Mammals, Bimana, but almost all other zoologists, an-
cient and modern, are agreed in including him in the
Primates.

Taken as a whole, this order is preeminently the ar-
boreal group among the Mammalia. Its members are more
completely and thoroughly specialized for this mode of
life than any other group. The long, slender limbs, flexi-
ble joints, opposable thumb, long toes capped with nails
instead of claws, the long, powerful and often prehensile
tail, are all peculiarly adapted to dwelling among the
branches of the forest, as the teeth are to eating the fruits
and berries which it affords. The highest primates, how-
ever, have departed from the typical habits of the order
and become partially or completely terrestrial.

It is probably to the stimulus of arboreal life that the
Primates owe the beginnings of that higher intelligence
which distinguishes them. Travel among the branches of
trees affords more continuous opportunities for the exer-
cise of intelligent choice in determining every successive
movement than does the more uniform and safer pro-
gression upon the surface of the ground or in the water,
or the violent but unvarying exercise of flying. One finds
that arboreal animals usually rank high in intelligence,
as, for instance, the squirrels among rodents, the raccoons
among the carnivora, the tree-shrews among insectivora,

190

ZOOLOGY

the opossums among marsupials. In addition, the oppos-
able thumb gives to the primate especial facility in touch-
ing and handling objects, and enables him to obtain readily
a more exact and complete knowledge of them.

In their skeleton structure this order has departed less
from the primitive mammal type than most others. A&.

Fig. 41 — Skeleton of the Spider-Monkey.
A type of mammal peculiarly fitted to live among the tree-tops.
Note the long, delicate limbs, the flexible five-toed feet, the
strong prehensile tail, the short but flexible neck, the large
brain. (Flower and Lydekker.)

has been pointed out, the earliest mammals were prob-
ably arboreal, and the primates have retained and per-
fected their adaptation to this mode of life. The most no-
table lines of progress are in the shortening of the face
and enlargement of the brain.

The living primates are divided into two groups — the
more primitive lemurs, and the more progressive monkeys,

THE VERTEBRATES— IV. MAMMALS 191

apes and man. The lemurs are chiefly found in Madagas-
car, but a few of them inhabit Central Africa, India and
the East Indies. They have a rather long face, with less
reduction in the number of teeth than the higher groups,
and in all except the Tarsier the lower incisors project
forward instead of upward. The brain also is decidedly
smaller and less complex, and they are very noticeably in-
ferior to monkeys in intelligence and activity. They are in
fact the little altered survivors of the ancestral primates
of the early Tertiary. Some of these ancestral primates
gave rise to the more progressive higher types, while oth-
ers retreated southward to the fringes of the Asiatic con-
tinents, or crossed into Africa, and thence reached Mada-
gascar. In the last-named island they found their most con-
genial home, free from the rivalry or pursuit of the higher
types of mammals, and developed into a remarkably large
and varied fauna, the largest and most remarkable of
which have very recently become extinct. The modern
Malagasy lemurs are all arboreal, small or of moderate
size, but in the late Pleistocene, probably just before man
gained a foothold on the island, there were large lemurs
of terrestrial adaptation, paralleling some of the ungulate
mammals in their skull, teeth and skeletons ; and others
with remarkably short face and large brain, paralleling
the higher apes. These last, one may suppose, would in
the course of time have evolved into creatures paralleling
man himself, had not their evolution been cut short by the
irruption of the more progressive races developed upon the
great northern land mass, in particular by the invasion
of early races of man. It should be pointed out that
a higher invading race destroys first those inferior races
which come most directly into competition with it, while
those among the native races, which are of different adap-
tation and habits, survive, as they do not interfere with
the higher race. Man invaded the Malagasy region prob-
ably during the Pleistocene (Glacial) epoch; the monkeys
have never reached the island. Hence the highly intelli-

192 ZOOLOGY

gent ground-lemurs, native to the island, which came in
competition with him, became extinct; the less intelligent
and smaller tree-lemurs have survived, because they did
not interfere with man, and had not to compete with
monkeys.

Of the higher or Anthropoid section of the Primates,
the South American monkeys are the most primitive. All
of them are strictly arboreal, one family, Cebidse, with pre-
hensile tails and opposable thumbs; the other, Hapalidse,
including only the little marmosets, in which the opposa-
bility of the thumb has been lost. The marmosets are
squirrel-like in size and habits; the Cebidae are of larger
size, but not as large as the Old World monkeys and
apes. In all the South American monkeys the nostrils
are separated by a broad cartilage, and their apertures look
outward. In the Old World monkeys, as in man, the car-
tilage septum is much reduced, the apertures close to-
gether and facing downward.

The Old World monkeys and baboons are united into a
single family, but are very various in proportions and ap-
pearance. The tail is sometimes long, sometimes short,
and many of them are more or less terrestrial, especially
the baboons. They inhabit all the tropical parts of the
Old World, but except for a species of Macaque that
lives on the Rock of Gibraltar, none are found in
Europe; nor do they live in Northern Asia north of
the Altii Mountains. The Macaques (Macacus) are
short-tailed, rather short-faced, Asiatic in range with
one species in North Africa and Gibraltar. The Langurs
(Semnopithecus) are long-tailed, arboreal monkeys of
southern and eastern Asia. The Maugabeys (Cercoce-
bus) are West African, the Guenous (Cercopithecus)
are also African, but more widely distributed. Both
genera are long-tailed. The baboons (Cynocephalus) are
distinguished by the projecting snout with heavy canine
teeth ; they are mostly of large size, live in herds, and are
more omnivorous and ferocious than any other primates.

THE VERTEBRATES— IV. MAMMALS 193

They are all African or Arabian, except one species from
Celebes, and inhabit rocky and mountainous districts, liv-
ing chiefly upon the ground.

The last group of the Primates to be considered are the
Anthropoid Apes of the family Simiidae. These are of
large size, of higher intelligence than any other primates,
tailless, and closely allied to man in all respects. They are
of arboreal habits, walking when on the ground in a semi-
erect position, the long arms reaching the ground but not
supporting the main weight of the body, and resting on
the back of the fingers instead of the palms as in all lower
animals. The skin is partly naked. The jaws, especially
in the adult males, are much larger and more projecting
than in man, and the brain capacity somewhat less than
half that of man, making allowance for the size of the
body in different species. The four living types are the
Gibbons of Southeastern Asia, the Gorilla and Chim-
panzee of the West African forests, and the Orang-
utan of Borneo and Sumatra. It is from some un-
known Tertiary members of this family of Apes that the
ancestry of Man must be derived. On account of this
relationship the Anthropoid Apes have been very care-
fully studied and described, and their appearance, habits
and structure are familiar to every one.

Remains of monkeys allied to the modern South Ameri-
can genera have been found in the Miocene formations of
Patagonia. In the Miocene of Europe have been found
remains of various monkeys and lower apes of the Old
World. Both are probably derived from the Eocene
lemurs of Europe and North America. So far as the
direct ancestry of the higher apes and man is concerned,
the geological record is very incomplete. The most in-
teresting of recent discoveries is the Pithecanthropos of
Java, founded upon a part of a skull and a femur which
probably (but not certainly) belonged to the same in-
dividual, and indicated an animal walking upright like
man, but in brain capacity intermediate between man

194 ZOOLOGY

and the higher apes. This species, however, according
to the latest investigations, was of Pleistocene age, con-
temporary with fully developed men, so that it cannot
be regarded as a direct ancestor in a genealogical sense.

Since the modern species of anthropoid apes live in
Africa and Southern Asia, and the most primitive races
of man are also found around the shores of the Indian
Ocean, the theory has been advanced that it is to some
part of this region that we should look for the discovery of
fossil remains of the primates ancestral to man. But in
this brief review of the evolution and geological history
of the lower races of mammals it has been seen that while
in the southern continents and around the southern fringes
of the great northern land mass are found numerous primi-
tive survivals of ancient races, yet the main theater of the
evolution of most races of mammals, their chief diffusion
center, has always been the great land mass of the three
northern continents, united more or less completely during
a large part of the Tertiary Period. West Africa and
southeastern Asia, with the East Indian Islands adjoining
it, contain many primitive survivals of races whose evo-
lution center was in the Pabearctic region.

In the present writer's opinion the geological evidence
of the ancestry of man and the most direct phylogmy of
many mammals will be discovered when the Tertiary for-
mations of Central and Eastern Asia are adequately and
thoroly searched for remains of fossil vertebrates. At
present they are practically unknown. From the observa-
tions of pioneer explorers it is very probably inferred that
fossiliferous formations of Tertiary age exist in some
parts of this immense region. The revealing of the evi-
dence which they should afford of the true evolutionary
history of the higher mammals and of man is the task for
the scientific explorers of the twentieth century.

BOTANY

MARION E. LATHAM

BOTANY

CHAPTER I

EARLY DEVELOPMENT

"What is the content and scope of the science of
botany?" asks Prof. Herbert Maule Richards, in a recent
lecture, and his reply is very true. "Popular opinion," he
says, "will answer somewhat easily : Botany consists in
the gathering of plants, and the dismembering of them,
in connection with the use of a complicated terminology.
That is the beginning and end of botany as it is under-
stood by the majority; there is nothing more to be said.
In consequence, the employment of the botanist seems so
trivial, so very remote from important human interests
that no second thought is given to it. The conception
formed in ignorance is continued in ignorance. Even the
zoologist is at an advantage, for the public is finally
forced to admit that it does not know what he is about,
while it understands the botanist very well. He is quite
hopeless, for, while flowers may be pretty things to pick,
they should not be pulled to pieces, and if he does not
happen to be interested in dissecting flowers he is not a
botanist but simply a fraud.

"Under botany we have to consider all the questions as
to the form, functions, the classification and the distribu-
tion of those organisms that are called plants. In the be-
ginning all that was known about plants might be readily
comprehended under the simple caption, Botany, but in
i97

198 BOTANY

modern times the rapid accumulation of facts has de-
manded a segregation of different lines of work. Thus
have arisen the divisions of botanical activity, which, for
our purposes, may be classed under three heads. First,
the taxonomic, or as more commonly called, the system-
atic side, which has to do with the classification, mainly
as established by gross morphology. Second, the mor-
phological field which concerns itself with the outward
and inward form and structure and the development
thereof, which may or may not have direct relation with
taxonomic work. Third, there is the domain of physiol-
ogy which treats of function.

"Any folk which had so far emerged from the stage
of savagery as to stop to notice the world about it would
perforce pay some attention to plants. A discrimination
of the medicinal uses of plants is often noticeable even in
primitive peoples, and with such observation goes also the
discrimination of difference in form, the prototype of
morphological research.

"In our own civilization we can trace back the history
of botany to Aristotle, who affords us some record of the
plant forms known at his time, tho the influence which
his philosophy wielded, even down to the middle of the
last century, was of vastly greater importance than any
contribution which he made to botany itself. Theophras-
tus gave a fuller account of plants, and later came the
inquiring and ever curious Pliny. Dioscorides, however,
in the first or second century of our era, was one of the
first to investigate plants with any attempt at thoroness
even from the standpoint of the knowledge of the time.
As is shown especially by Dioscorides' work, the study of
plants was largely from their use as drugs, and they were
described simply to facilitate their recognition. Any real
knowledge of them was naturally meager, and false ideas
that clung for a long time, some until comparatively re-
cently, prevented any proper conception of form and
function.

EARLY DEVELOPMENT

199

"The contributions become of less and less value as we
approach the middle ages, the botanical writings of which
time were full of the wildest fantasy and superstition. In
the sixteenth century in northern Europe, particularly
Germany, there was a movement toward the real study of
plants from the plants themselves as evidenced by the

Fig. 1 — The Mandrake.
Medieval drawing, showing fear of fabulous human plant. Dog
is pulling out root, as to do so by the hand of man meant loss
of immortality. Horn is blown to drown supposed shrieks
which caused eternal deafness.

works of the herbalists, but no attempt at classification
was made. Here there was an attempt at the enumeration
and illustration of plants from living specimens, and con-
fused and empirical as this work was, it was actuated by
an honest endeavor to record, as accurately as possible,
actual forms, and not fanciful abstractions which never

200 BOTANY

did and never could have existed. All the descriptions
were detached from one another and little or no attempt
was made at classification, tho by the repeated study of
many similar forms the idea of natural relationship began
to dawn in a vague way. The actual purpose of all this
plant study was the recording of the officinal plants, for
special knowledge of plants was still confined to their uses
in medicine.

"While this movement was advancing in northern
Europe, a mainly artificial system of classification was
developing in Italy and found its culmination in the work
of C?esalpino, who strongly influenced the progress of
botany, even after his own time and into the middle of
the eighteenth century."

"As the nature of plants," so begins Csesalpino's book,
"possesses only that kind of soul by which they are nour-
ished, grow, and produce their like, and they are therefore
without sensation and motion in which the nature of ani-
mals consists, plants have accordingly need of a much
smaller apparatus of organs than animals." This idea re-
appears again and again in the history of botany, and the
anatomists and physiologists of the eighteenth century
were never weary of dilating on the simplicity of the struc-
ture of plants and of the functions of their organs. "But
since the function of the nutritive soul consists in producing
something like itself, and this like has its origin in the
food for maintaining the life of the individual, or in the
seed for continuing the species, perfect plants have at
most two parts, which are, however,of the highest neces-
sity ; one part called the root by which they procure food ;
the other by which they bear the fruit."

This conception of the upright stem as the seed-bearer
of the plant, which is in the main correct, also was long
maintained in botany. It should be observed also that the
production of the seed is spoken of as merely another kind
of nutrition, a notion which afterward prevented Mal-
pighi from correctly explaining the flower and fruit, and

EARLY DEVELOPMENT 201

in a modified form led Kaspar Friedrich Wolff in 1759 to
a very wrong conception of the nature of the sexual func-
tion. The next sentence in Csesalpino leads into the heart
of the Aristotelian misinterpretation of the plant, accord-
ing to which the root answers to the mouth or stomach,
and must therefore be regarded in idea as the upper part
altho it is the lower in position, and the plant would have
to be compared with an animal set on its head, and the
upper and lower parts determined accordingly.

Caesalpino's discussion of the seat of the soul in plants
is of special interest in connection with certain views of
later botanists. "Whether any one part in plants can be
assigned as the seat of the soul, such as the heart in ani-
mals, is a matter for consideration," he says, "for since
the soul is the active principle ('actus') of the organic
body, it can neither be 'tota in toto' nor 'tota in singulis
partibus,' but entirely in some one and chief part, from
which life is distributed to the other dependent parts. If
the function of the root is to draw food from the earth,
and of the stem to bear the seeds, and the two cannot ex-
change functions, so that the root should bear seeds and
the shoot penetrate into the earth, there must either be
two souls different in kind and separate in place, the one
residing in the root, the other in the shoot, or there must
be only one, which supplies both with their peculiar capa-
bilities. "

"It may be remarked here," says Julius von Sachs in
his 'History of Botany/ "that the point of union between
the root and the stem, in which Csesalpino placed the seat
of the plant-soul, afterward received the name of root-
neck (collet) ; and tho the Linnsean botanists of the nine-
teenth century were unaware of what Csesalpino had
proved in the sixteenth, and did not even believe in a
soul of plants, they still entertained a superstitious respect
for this part of the plant, which is really no part at all;
and this, it would seem, explains the fact that an impor-

202 BOTANY

tance scarcely intelligible without reference to history was
once attributed to it, especially by some French botanists."

The theoretical introduction to his excellent and copious
remarks on the parts of fructification may supply another
example of Csesalpino's peripatetic method: "As the final
cause, 'finis/ of plants consists in that propagation which
is effected by the seed, while propagation from a shoot is
of a more imperfect nature, in so far as plants do exist in
a divided state, so the beauty of plants is best shown in
the production of seed, for in the number of the parts and
the forms and varieties of the seed-vessels the fructifica-
tion shows a much greater amount of adornment than the
unfolding of a shoot; this wonderful beauty proves the
delight, 'delitas,' of generating nature in the bringing
forth of seeds. Consequently as in animals the seed is an
excretion of the most highly refined food-substance in the
heart, by the vital warmth and spirit of which it is made
fruitful, so also in plants it is necessary that the substance
of the seeds should be secreted from the part in which the
principle of the natural heat lies, and this part is the pith.
For this reason, therefore, the pith of the seed (that is,
the substance of the cotyledons and of the endosperm)
springs from the moister and purer part of the food, while
the husk which surrounds the seed for protection springs
from the coarser part. It was unnecessary to separate a
special fertilizing substance from the rest of the matter in
plants, as it is separated in animals which are thus distin-
guished as male and female."

This last remark and some lengthy deductions which
follow are intended to prove, after the example of Aris-
totle, the absence and indeed the impossibility of sexuality
in plants, and accordingly Csesalpino goes on to compare
the parts of the flower, which he knew better than his con-
temporaries, with the envelopes of the ova in the fetus
of animals, which he regards as organs of protection.

"The doctrine of metamorphosis," suggests Von Sachs,
"appears in a more consistent and necessary form in

EARLY DEVELOPMENT 203

Csesalpino than in the botanists of the nineteenth century
before Darwin; it flows more immediately from his philo-
sophical views on the nature of plants, and appears there-
fore up to a certain point thoroly intelligible. We see in
Caesalpino's doctrine of metamorphosis without doubt the
theory of the flower afterward adopted by Linnaeus, tho
in a somewhat different form." That Linnaeas himself
regarded the theory ascribed to him on the nature of the
flower as the opinion of Csesalpino also, is shown in his
'Classes Plantarum,' where in describing Caesalpino's sys-
tem he says : "He regarded the flower as the interior por-
tions of the plant, which emerge from the bursting rind ;
the calyx as a thicker portion of the rind of the shoot ; the
corolla as an inner and thinner rind; the stamens as the
interior fibers of the wood, and the pistil as the pith of the
plant."

But, to do Caesalpino justice, it would be necessary to
give a full account of his very numerous, accurate and
often acute observations on the position of leaves, the
formation of fruits, the distribution of seeds and their po-
sition in the fruit, of his comparative observations on the
parts of the fruit in different plants, and above all of his
very excellent description of plants with tendrils and
climbing plants, of those that are armed with thorns and
the like. Tho there is naturally much that is erroneous
and inexact in his accounts, yet in the chapters on these
subjects may be seen the first beginning of a comparative
morphology, which quite casts into the shade all that
Aristotle and Theophrastus have said on the subject. But
the most brilliant portions of his general botany are those
in which he gives the outlines of his views on the system-
atic arrangement of plants.

All that Caesalpino says on systematic arrangement
shows that he was perfectly clear in his own mind with
regard to the distinction between a division on subjective
grounds, and one that respects the inner nature of plants
themselves, and that he accepted the latter as the only true

204 BOTANY

one. He says, for instance : "We seek out similarities and
dissimilarities of form, in which the essence, 'substantia/
of plants consists, but not of things which are merely acci-
dents of them, 'qua? accidunt ipsis.' " Medicinal virtues
and other useful qualities are, he says, just such accidents.
Here the path is opened, along which all scientific arrange-
ment must proceed, if it is to exhibit real natural affinities,
but at the same time there is a warning already of the
error which beset systematic botany up to Darwin's time ;
if in the above sentence he substituted the word idea for
that of substance, and the two expressions have much the
same meaning in the Aristotelian and Platonic view of
nature, will be recognised the modern pre-Darwinian doc-
trine, that species, genera, and families represent 'ideam
quandam' and 'quoddam supranaturale.'

The next great figure in botanical science was Joachim
Jung. He was born in Liibeck in the year 1587, and died
after an eventful life in 1657. He was a contemporary
of Kepler, Galileo, Vesal, Bacon, Gassendi, and Descartes.
After having been already a professor in Giessen, he ap-
plied himself to the study of medicine in Rostock, was in
Padua in 1618 and 1619, and there, as may confidently be
believed, became acquainted with the botanical doctrines
of Csesalpino, who had died fifteen years before. He oc-
cupied himself with the philosophy of the day, in which
he appeared as an opponent of scholasticism and of Aris-
totle, and also with various branches of science, mathe-
matics, physics, mineralogy, zoology, and botany. In 1662
his pupil, Martin Fogel, printed the 'Doxoscopiae Physical
Minores,' a work of enormous compass left in manuscript
at the master's death, and another pupil, Johann Vagetius,
the Tsagoge Phytoscopica,' in 1678. Ray, however, states
that a copy of notes on botanical subjects had already
reached England in 1660. He was the first who objected
to the traditional division of plants into trees and herbs
as not founded on their true nature. But how firmly this
old dogma was established is well shown by the fact that

EARLY DEVELOPMENT 205

Ray at the end of the century still retained this division,
tho he founded his botanical theories on the Tsagoge' of
Jung. Jung was in advance of Caesalpino and his own
contemporaries in repeatedly expressing his doubt of the
existence of spontaneous generation.

"The Tsagoge Phytoscopica,' a system of theoretical
botany," says Von Sachs, "very concisely written and in
the form of propositions arranged in strict logical se-
quence, was a more important work and had more lasting
effects upon the history of botany. The first chapter of the
Tsagoge' discusses the distinction between plants and ani-
mals. A plant is, according to Jung, a living but not a
sentient body ; or it is a body attached to a fixed spot or a
fixed substratum, from which it can obtain immediate
nourishment, grow and propagate itself. A plant feeds
when it transforms the nourishment which it takes up into
the substance of its parts, in order to replace what has
been dissipated by its natural heat and interior fire. A
plant grows when it adds more substance than has been
dissipated, and thus becomes larger and forms new parts.
The growth of plants is distinguished from that of ani-
mals by the circumstance that their parts are not all grow-
ing at the same time, for leaves and shoots cease to grow
as soon as they arrive at maturity; but then new leaves,
shoots, and flowers are produced. A plant is said to propa-
gate itself when it produces another specifically like itself ;
this is the idea in its broader acceptation. We see that
here, as in Caesalpino, the idea of the species is connected
with that of propagation.

"The second chapter, headed 'Plantae Partitio,' treats
of the most important morphological relations in the ex-
ternal differentiation of plants; here Jung adheres essen-
tially to Csesalpino's view, that the whole body in all
plants, except the lowest forms, is composed of two chief
parts, the root as the organ which takes up the food, and
the stem above the ground which bears the fructification.
Jung's theory of the flower suffers, as m Csesalpino, from

206 BOTANY

his entire ignorance of the difference of sexes in plants,
which is sufficient to render any satisfactory definition of
the idea of a flower impossible."

While Caesalpino, Kaspar Bauhin, and Jung stand as
solitary forms each in his own generation, the last thirty
years of the seventeenth century are marked by the stir-
ring activity of a number of contemporary botanists.
While during this period physics were making rapid ad-
vances in the hands of Newton, philosophy in those of
Locke and Leibnitz, and the anatomy and physiology of
plants by the labors of Malpighi and Grew, systematic
botany was also being developed, tho by no means to the
same extent or with equally profound results, by Morison,
Ray, Bachmann (Rivinus), and Tournefort. The works
of these men and of their less gifted adherents, following
rapidly upon or partly synchronous with each other, led
to an exchange of opinions and sometimes to polemical
discussion, such as had not before arisen on botanical sub-
jects; this abundance of literature, with the increased ani-
mation of its style, excited a more permanent interest,
which spread beyond the narrow circle of the professional
adepts.

Carl Linnaeus, called Carl von Linne after 1757, was
born in 1707 at Rashult in Sweden, where his father was
preacher. Linnaeus is commonly regarded as the reformer
of the natural sciences which are distinguished by the
term descriptive, and it is usual to say that a new epoch
in the history of our science begins with him, as a new
astronomy began with Copernicus and new physics with
Galileo. "This conception of Linnaeus' historical position,"
Von Sachs points out, "as far at least as his chief subject,
botany, is concerned, can only be entertained by one who
is not acquainted with the works of Caesalpino, Jung, Ray
and Bachmann, or who disregards the numerous quota-
tions from them in Linnaeus' theoretical writings. On the
contrary, Linnaeus is preeminently the last link in the
chain of development represented by the above-named

EARLY DEVELOPMENT 207

writers; the field of view and the ideas of Linnaeus are
substantially the same as theirs ; he shares with them in
the fundamental errors of the time, and indeed essentially
contributed to transmit them to the nineteenth century.
But to maintain that Linnaeus marks not the beginning of
a new epoch, but the conclusion of an old one, does not at
all imply that his labors had no influence upon the time
that followed him."

If the works of the earlier botanists are compared with
Linnaeus' 'Fundamenta Botanica' (1736), his 'Classes
Plantarum' (1738) and his Thilosophia Botanica' (1751).
it becomes evident that the ideas on which his theories
are based are to be found scattered up and down in the
works of his predecessors. Further, whoever has traced
the history of the sexual theory from the time of Camera-
rius (1694), must allow that Linnaeus added nothing new
to it, tho he contributed essentially to its recognition. But
thaj: which gave Linnaeus so overwhelming an importance
for his own time was the skilful way in which he gath-
ered up all that had been done before him; this fusing to-
gether of the scattered acquisitions of the past is the great
and characteristic merit of Linnaeus.

Caesalpino was the first who introduced Aristotelian
modes of thought into botany; his system was intended
to be a natural one, but it was in reality extremely un-
natural ; Linnaeus, in whose works the profound impression
which he had received from Caesalpino is everywhere to
be traced, retained all that was important in his predeces-
sor's views, but perceived at the same time what no one
before him had perceived, that the method pursued by
Caesalpino could never do justice to those natural affinities
which it was his object to discover, and that in this way
only an artificial tho very serviceable arrangement could
be attained, while the exhibition of natural affinities must
be sought by other means.

As regards the terminology of the parts of plants, which
was all that the morphology of the day attempted, Lin-

THE L1NNEAN SVSTEM.

Fig. 2 — First to Tenth Class of Linn^an System,
i., Alpinea ; 2., Lilac; 3., Valerian; 4., Cornel; 5., Aralia ; 6.,
Gagea ; 7., horse chestnut ; 8., spurge laurel ; 9., flowering
rush; 10., Poke Weed. (Kerner.)

EARLY DEVELOPMENT 209

naeus simply adopted all that was contained in the 'Isagoge'
of Jung, but gave it a more perspicuous form, and ad-
vanced the theory of the flower by accepting without hesi-
tation the sexual importance of the stamens, which was
still but little attended to; he thus arrived at a better
general conception of the flower, and this bore fruit again
in a terminology which is as clear as it is convenient.
But there was one great misconception in the matter,
which has not a little contributed to increase Linnaeus'
reputation. He called his artificial system, founded on
the number, union and grouping of the stamens and car-
pels, the sexual system of plants, because he rested its
supposed superiority on the fact that it was founded upon
organs the function of which lays claim to the very high-
est importance. But it is obvious that the sexual system
of Linnaeus would have the same value for the purposes of
classification, if the stamens had nothing whatever to do
with propagation, or if their sexual significance were quite
unknown. For it is exactly those characters of the sta-
mens which Linnaeus employs for purposes of classifica-
tion, their number and mode of union, which are matter
of entire indifference as regards the sexual function.

Linnaeus distinctly declared it was his view that the
highest and only worthy task of a botanist was to know all
species of the vegetable kingdom exactly by name, and
his school in Germany and England adhered to it so firmly
that it established itself with the general public, who to the
present day consider it as a self-evident proposition that a
botanist exists essentially for the purpose of at once desig-
nating any and every plant by a name. Like his predeces-
sors, Linnaeus regarded morphology and general theoreti-
cal botany only as means to be used for discovering the
principles of terminology and definition, with a view to the
improvement of the art of describing plants.

"The most pernicious feature in scholasticism and the
Aristotelian philosophy is the confounding of mere con-
ceptions and words with the objective reality of the

2io BOTANY

things denoted by them," says Von Sachs upon this point.
"Men took a special pleasure in deducing the nature of
things from the original meaning of the words, and even
the question of the existence or non-existence of a thing
was answered from the idea of it. This way of thinking
is found everywhere in Linnaeus, not only where he is
busy as systematist and describer, but where he wishes to
give information on the nature of plants and the phe-
nomena of their life. Linnaeus cared little for experimen-
tal proof; he expends all his art on a genuine scholastic
demonstration intended to prove the existence of sexuality
as arising necessarily from the nature of the plant."

On the whole the superiority of Linnaeus lay in his natu-
ral gift for discriminating and classifying the objects
which engaged his attention ; he might almost be said to
have been a classifying, coordinating and subordinating
machine. He dealt with all about which he wrote in the
way in which he dealt with objects of natural history.

"In any attempt to estimate the advance which the
science owes to the labors of Linnaeus," says the former
writer, "the chief prominence must be assigned to two
points: First to his success in carrying out the binary
nomenclature in connection with the careful and methodi-
cal study which he bestowed on the distinguishing of
genera and species ; this system of nomenclature he en-
deavored to extend to the whole of the then known vege-
table world, and thus descriptive botany in its narrower
sense assumed through his instrumentality an entirely
new form. The second merit is that while he framed his
artificial sexual system, he exhibited a fragment of a natu-
ral system by its side and repeatedly declared that the
chief task of botanists is to discover the natural system.
Thus he cleared the ground for systematic botany."

The main features of Linnaeus' theoretical botany can
best be learned from the 'Philosophia Botanica/ which
may be regarded as a text-book of that which Linnaeus
called botany and which far surpasses all earlier compo-

EARLY DEVELOPMENT 211

sitions of the kind in perspicuity and precision and in
copiousness of material, and indeed it would be difficult to
find in the ninety years after 1781 a text-book of botany
which treats what was known on the subject at each period
with equal clearness and completeness. The vegetable
world, says Linnaeus, comprises seven families, Fungi,
Algae, Mosses, Ferns, Grasses, Palms and Plants. All are
composed of three kinds of vessels, sap-vessels which con-
vey the fluids, tubes which store up the sap in their cavities
and tracheae which take in air; these statements Linnaeus
adopts from Malpighi and Grew.

The parts in the individual plant which the beginner
must distinguish are three : the root, the herb and the parts
of fructification, in which enumeration Linnaeus departs
from his predecessors, by whom the fructification and the
herb together are opposed to the root. In the central part
of the plant is the pith, enclosed by the wood which is
formed from the bast; the bast is distinct from the rind,
which again is covered by the epidermis ; these anatomical
facts are from Malpighi ; the statement that the pith grows
by extending itself and its envelopes is borrowed from
Mariotte.

The root, which takes up the food, and produces the
stem and the fructification, consists of pith, wood, bast and
rind, and is divided into the two parts, 'caudex' and
'radicula.' The 'caudex' answers pretty nearly to the
modern primary root and rhizomes, the 'radicula' to what
is now called secondary roots. The herb springs from the
root and is terminated by the fructification; it consists of
the stem, leaves, leaf-supports ('fulcrum') and the organs
of hibernation ('hibernaculum'). Then follow the further
distinctions of stem and leaves, the terminology, still
partly in use and resting essentially on the definitions of
Jung, is here set forth in great detail. Linnaeus, however,
does not mention the remarkable distinction between stem
and leaf which Jung founded on relations of symmetry.
In this course of mixing up morphological and biological

212 BOTANY

relations of organs he was followed by botanists till late
into the nineteenth century.

Linnaeus goes far beyond his predecessors in distinguish-
ing and naming the organs of fructification. The fructi-
fication, he says, is a temporary part in plants devoted to
propagation, terminating the old and beginning the new.
He distinguishes the following seven parts: (i) The
calyx, which represents the rind, including in this term
the involucre of the Umbelliferae, the spathe, the calyptra
of Mosses and even the volva of certain Fungi, another
instance of the way in which Linnaeus was guided by ex-
ternal appearance in his terminology of the parts of plants ;
(2) the corolla, which represents the inner rind (bast) of
the plant; (3) the stamen, which produces the pollen;
(4) the pistil, which is attached to the fruit and receives
the pollen; here for the first time the ovary, style and
stigma are clearly distinguished. But next comes as a
special organ (5) the pericarp, the ovary which contains
the seed. Nevertheless Linnaeus distinguishes the differ-
ent forms of fruit much better than his predecessors had
done. (6) The seed is a part of the plant that falls off
from it, the rudiment of a new plant, and it is excited to
active life by the pollen. The treatment of the seed and
its parts is the feeblest of all Linnaeus' efforts ; he follows
Caesalpino, but his account of the parts of the seed is
much more imperfect than that of Caesalpino and his
successors. (7) By the word 'receptaculum' he under-
stands everything by which the parts of the fructification
are connected together, both the 'receptaculum proprium/
which unites the parts of the single flower, and the 'recep-
taculum commune,' under which term he comprises the
most diverse forms of inflorescence (umbel, cyme, spadix).

He concludes with the remark that the essence of the
flower consists in the anther and the stigma, that of the
fruit in the seed, that of the fructification in the flower
and the fruit and that of all vegetable forms in the fructi-
fication, and he adds a long list of distinctions between the

EARLY DEVELOPMENT 213

organs of fructification with their names ; among these
organs appear the nectaries, which he was the first to dis-
tinguish.

From Linnaeus the advance was more rapid, and, while
most of the study in plants centered on the work of classi-
fication, there were unmistakable signs of other interests.
The ideas of the classified were still hampered by the
dogma of the constancy of species, which continually
clashed with the insistent and undeniable evidences of the
genetic relationships of organic forms. Despite the move-
ment in favor of the idea of the development of species
from previously existing forms, despite the views ad-
vanced by Lamarck and others at about that time, despite,
indeed, the more strictly botanical investigations in the
morphological field which were brought forward during
the first half of the nineteenth century — despite all these
things, the botanist was unable to break away from the
concept of groups of plants as abstract ideas.

It was not until 1859 that the publication of Darwin's
'Origin of Species' drove biologists to a different point of
view. Then the rational idea of the evolution of organic
forms explained in a similar rational fashion the observed
genetic relationships of groups of plants. "No longer,"
says Richards, "did the classifier hesitatingly admit the
possibility of the evolution of species and deny that of
genera and higher groups, no longer did he maintain his
artificial groups, which had no more relation to each
other than successive throws of dice, but he admitted the
whole great scheme implied by the evolution of organic
forms from preexisting types."

"The natural system was rightly appreciated by Lin-
naeus," says Asa Gray in his 'Structural Botany,' "who
pronounced it to be the first and last desideratum in sys-
tematic botany ; and he early attempted to collocate most
known genera under natural orders, but without definition
or arrangement. In his later years he was unable to ac-
complish anything more." The difficult problem was

214 BOTANY

taken up by Linnaeus' contemporary and correspondent,
Bernard de Jussieu. His pupil, Adanson, published in
1763, in his 'Families des Plantes/ the first complete system
of natural orders. Adanson himself thus defines his idea
of species : "The moderns define a species of plant as a
collection of several individuals which resemble each other
perfectly, yet not in everything, but in the essential parts
and qualities, without, however, giving attention to the
differences caused in these individuals either by sex or
accidental varieties.

Antoine Laurent de Jussieu, nephew of Bernard, fol-
lowed Adanson. "He has been called the founder of the
natural system of Botany," says Asa Gray, "and to him
more than to any other one person this honor may be
ascribed. In his 'Genera Plantarum secundum Ordines
Naturales disposita,' 1789, natural orders of plants, one
hundred in number, were first established and defined by
proper characters, and nearly all known genera arranged
under them."

The next great systematist was Auguste Pyrame de
Candolle. Reversing the order of Jussieu, who proceeded
from the lower or simpler to the higher or more complex
forms, De Candolle began with the latter, the phenoga-
mous or flowering plants, and with those having typically
complete flowers. De Candolle's interest was perhaps
more from a morphological point of view, altho he is to
be regarded as a systematist, and from that standpoint it
will be seen later that his work was of the first importance.

John Lindley in successive attempts (between 1830 and
1845) variously modified and in some few respects im-
proved the Candollean arrangement. Robert Brown, next
to Jussieu, did more than any other botanist for the proper
establishment and correct characterization of the natural
orders. Stephen Ladislaus Endlicer, of Vienna, a con-
temporary of Lindley, of less botanical genius but of great
erudition and aptness for classification, brought out his
complete 'Genera Plantarum secundum Ordines Naturales

EARLY DEVELOPMENT 215

disposita' between the years 1836 and 1840. The 'Genera
Plantarum' of Bentham and Hooker adopts in a general
way the Candollean sequence of order with various emen-
dations, divides the class of Dicotyledons into two sub-
classes, Angiosperms and Gymnosperms, with still further
divisions in the Angiosperms.

In this country botanists have to thank the labors of
John Torrey and Asa Gray for the firm foundation upon
which the knowledge of American flora is built. Of the
two, Asa Gray was by far the broader in his interests and
is regarded by many as the father of American botany.
He had considerable knowledge of other fields than that
of mere systematic botany of the higher plants and was
perhaps the ablest protagonist whom Darwin had in this
country. He wrote numerous papers in defense of the
then new theory of the origin of species. His main work,
however, was the taxonomic study of the flora of North
America.

Discussion of the definition of species, how much a
species includes and of what constitutes a variety is at
present a foremost question among taxonomists, and the
effort seems to look toward simplification and lessening
of the numbers already formed. Linnaeus tells in his
'Philosophia Botanica' (1751): "We enumerate as many
species as different forms were originally created." He
also says, "There are as many species as the Infinite Being
originally produced different forms, and these forms, fol-
lowing the laws of reproduction imposed upon them, have
produced more, but always similar to themselves. There-
fore there are as many species as there are different forms
or structures met with to-day."

The idea of a species set forth by Lamarck is thus
defined: "In botany as in zoology a species is necessarily
constituted of the aggregation of similar individuals which
perpetuate themselves, the same, by reproduction. I under-
stand similarity in the essential qualities of the species,
because the individuals which constitute it offer frequently

216 BOTANY

accidental differences, which give rise to varieties and
sometimes sexual differences, which belong, however, to
the same species, as the male and female hemp, in which
all the individuals constitute the common cultivated hemp.
Thus, without the constant reproduction of similar indi-
viduals, there could not exist a true species."

De Candolle and Sprengle say that "by species we un-
derstand a number of plants which agree with one another
in invariable marks. No doubt there were in the preced-
ing state of our globe other species of plants which have
now perished and the remains of which we still find in
impressions in shale, slate-clay and other floetz rocks.
Whether the present species, which often resemble these,
have arisen from them; whether the great revolutions on
the surface of the earth, which we read in the Book of
Nature, contributed to these transitions, we know not.
What we know is that from as early a time as the human
race has left memorials of its existence upon the earth
the separate species of plants have maintained the same
properties invariably.

"To be sure, we frequently speak of the transitions and
crossings of species; and it cannot be denied that some-
thing of this kind does not occur, tho without affecting
the idea of species which we have proposed. We must,
therefore, understand this difference. Species only appear
to undergo transitions when we have considered an organ
or a property as invariable, which is not so.

"All properties of plants which are subject to change
form either a sub-species or a variety. By the former we
understand such forms as continue indeed during some
reproductions, but at last, by a greater difference of soil,
of climate and of treatment, are either lost or changed."
John Lindley in his 'Introduction to Botany' defines spe-
cies as "a union of individuals agreeing with each other in
all essential characters of vegetation and fructification,
capable of reproduction by seed without change, breeding

EARLY DEVELOPMENT 217

freely together and producing perfect seed from which a
fertile progeny can be reared."

To Asa Gray "species in biological natural history is a
chain or series of organisms of which the links or com-
ponent individuals are parent and offspring. Objectively
a species is the totality of beings which have come from
one stock, in virtue of that most general fact that likeness
is transmitted from parent to progeny.

"The two elements of species are (1) community of
origin and (2) similarity of the component individuals.
But the degree of similarity is variable, and the fact of
genetic relationship can seldom be established by observa-
tion or historical evidence. It is from the likeness that the
naturalist ordinarily decides that such and such individuals
belong to one species. Still the likeness is a consequence
of the genetic relationship, so that the latter is the real
foundation of species.

"Varieties are forms of species marked by characters of
less fixity or importance than are the species themselves.
They may be of all grades of difference from the slightest
to the most notable; they abound in free nature, but as-
sume particular importance under domestication and culti-
vation, under which variations are prone to originate,
and desirable ones are preserved, led on to further develop-
ment and relatively fixed."

Charles Darwin, whose work has done so much to put
all natural sciences upon their present basis of experimen-
tal observation, does not commit himself to an actual
statement. He says that "no one definition has satisfied
all naturalists; yet every naturalist knows vaguely what
he means when he speaks of a species. The term variety
is almost equally difficult to define, but here community of
descent is almost universally implied, tho it can rarely
be proved."

"All the individual plants which resemble each other
sufficiently to make us conclude that they are all or may
have been all descended from a common parent" are in-

218 BOTANY

eluded in one species by George Bentham. "These individu-
als may often differ from each other in many striking par-
ticulars, such as the color of the flower, size of the leaf,
etc., but these particulars are such as experience teaches
us are liable to vary in the seedlings raised from one in-
dividual. When a large number of the individuals of a
species differ from the others in any striking particular,
they constitute a variety." Britton and Brown consider
that "a species is composed of all the individuals of a kind
capable of continuous successive propagation among them-
selves."

"Nature produces individuals," declares Charles E.
Bessey, "and nothing more. She produces them in such
countless numbers that we are compelled to sort them into
kinds in order that we may be able to carry them in our
minds. This sorting is classification-taxonomy. But right
here we are in danger of misunderstanding the matter.
We do not actually sort out our individuals. We imagine
them sorted out. It is only to a very slight extent that the
systematic botanist ever actually sorts out individuals.

"So species have no actual existence in nature. They
are mental concepts and nothing more. They are con-
ceived in order to save ourselves the labor of thinking in
terms of individuals, and they must be so framed that they
do save us labor."

"It should be borne in mind," ably summarizes Asa
Gray, "that the natural system of botany is natural only
in the constitution of its genera, tribes, orders, etc., and
in its grand divisions; that its cohorts and the like are as
yet only tentative groupings, and that the putting together
of any or all these parts in a system, and especially in a
lineal order, necessary as a lineal arrangement is, must
needs be largely artificial. So that even the best per-
fected arrangements must always fail to give of themselves
more than an imperfect and considerably distorted reflec-
tion of the plan of the vegetable kingdom or even of our
knowledge of it."

CHAPTER II

PLANT STRUCTURES

The work of the earlier botanists was given over to
two main objects, the classification of species and varie-
ties in a manner that should most readily account for the
entire system, and the determination of a true basis for
such a taxonomic classification, requiring a somewhat
close study of the morphology and the physiology of the
plant. The later botanists, beginning mainly from the
bases laid down by Linnaeus, developed the Science of
Botany into a study of no little complexity ; and questions
arose, of intense interest in themselves, but which took
for granted a basic knowledge of these simpler matters
of structure and of classification. As it would be difficult
to carry the development of botanical thought up to its
modern complexity without an assurance that the reader
was conversant with the general outline, it is thought
wiser to touch on it briefly here.

Plants are differentiated from each other by certain
variances of their parts, which again reveal causes deeper
still. Wherefore an understanding of the nature of these
parts should precede a statement of their differences.

Just as the man has various members, by which he sees,
hears, feels, so have the plants several kinds of organs.
The advantage of this to the plant becomes plain by using
the common illustration of the difference between a tribe
of savages and a civilized community. Several kinds of
organs in a plant mean to the plant just what division of
219

220 BOTANY

labor means to the community; it results in better work
and more work.

All the work done by plants comes under two heads:
nutrition and reproduction. This means that every plant
must care for two things, (i) the support of its own body
(nutrition), and (2) the production of other plants like
itself (reproduction). To the great work of nutrition
many kinds of work contribute, and the same is true of
reproduction. In a complex plant, therefore, there are
certain organs which specially contribute to the work of
nutrition and others which are specially concerned with
the work of reproduction.

The plant is extremely dependent upon its surround-
ings, more so because of its lack of locomotion. For
example, it must receive material from the outside and
get rid of waste material. Therefore, organs must estab-
lish certain definite relations with things outside of them-
selves before they can work effectively; and these neces-
sary relations are known as life-relations. For example,
green leaves are definitely related to light — they cannot
do their peculiar work without it; many roots must be
related to the soil; certain plants are related to abundant
water; some plants, such as parasites, are related to other
plants. Each organ, therefore, must become adjusted to
a complete set of relations, and a plant with several organs
has many delicate adjustments to care for. Three con-
spicuous organs, root, stem and leaf, are concerned with
nutrition ; and most of these plants have at some time also
another structure, the flower, which is concerned with
reproduction.

On examining an ordinary leaf, the blade is seen to
consist of a green substance through which a network
of veins is distributed. The larger veins that enter the
blade send off smaller veinlets that are invisible. This
is plainly shown by a skeleton leaf, wherein it appears
that the vein system or venation of leaves is exceedingly:

PLANT STRUCTURES

221

diverse, altho all forms can be referred to a few general
plans.

In some leaves a single very prominent vein known as
the midrib runs through the middle of the blade. From
this all the minor veins arise as branches, and such
a leaf is said to be pinnately veined. In other leaves sev-
eral large veins (ribs) of equal prominence enter the blade

A\ W C

Fig. 3 — Tvfes of Venation.

A., pinnately veined leaf of quince : B., palmately veined leaf of

geranium ; C, parallel-veined leaf of lily of the valley.

and diverge, each giving rise to smaller branches. Such
a leaf is said to be palmately veined. In still other leaves
all the visible veins run approximately parallel from the
base of the blade to its apex, such leaves being parallel-
veined, as distinct from the two preceding, which are both
net-veined.

The upper and the under surface of a leaf is covered by
a delicate transparent skin (epidermis), which generally
shows no green color. "Examined under the compound
microscope," says John M. Coulter, "it is seen to be made

222 BOTANY

up of small units of structure known as cells. Each cell is
bounded by a wall, and in the epidermis these cells fit
closely together, sometimes dovetailing with one another.
Characteristic openings in the epidermis also will be dis-
covered, sometimes in very great numbers. The whole
apparatus is known as a stoma. These numerous openings
are the stomata, which give passageway into the interior
of the leaf, putting the internal cells into communication
with the air outside and so facilitating the interchange

Fig. 4 — Cross-sections of Leaves.
A., bush clover ; B., begonia ; C, lily.

of gases. The size of these apertures may vary under
different conditions.

"Between these two epidermal layers is the mass of
green tissue making up the body of the leaf, and known as
mesophyll. This comprises cells containing the numerous
small green bodies (chloroplasts) that give color to the
whole leaf. Usually the mesophyll cells are arranged dif-
ferently in the upper and lower regions of the horizontal
leaf. In the upper region the cells just beneath the epi-
dermis are elongated at right angles to the surface of the
leaf, and stand in close contact, forming the palisade tis-

PLANT STRUCTURES

223

sue. In the lower region of the leaf the cells are irregu-
lar in form, and so loosely arranged as to leave air space
between the cells, the whole region forming the spongy
tissue. The air spaces communicate with one another,
thus forming a labyrinthine system of air chambers
throughout the spongy mesophyll. It is into this system

Fig. 5 — Upper Layers of Lilac Leaf.
e., epidermis ; p., palisade mesophyll ; ch., chloroplast ; sp., spongy
mesophyll ; i., intercellular spaces ; v., small vein cut across ;
L, end of vein; col., collecting cells; s., stoma. (Hanson.)

of air chambers that the stomata open, and thus what may
be called an internal atmosphere is in contact with alt
the green working cells, and this internal atmosphere is
in free communication, through the stomata, with the
external atmosphere."

"In general," says G. F. Atkinson, "the function of the

224 BOTANY

foliage leaf as an organ of the plant is five-fold: (i) That
of carbon-dioxide assimilation; (2) that of transpiration;

(3) that of the synthesis of other organic compounds;

(4) that of respiration; (5) that of assimilation proper or
the making of new living substances."

The importance of the work of leaves is apparent, but
this work cannot be done unless the leaf is exposed
to light. This fact explains many things in connection
with the position and arrangement of leaves. Leaves must
be arranged to receive as much light as possible to help
in their work, but too intense light is dangerous; hence
the adjustment to light is a delicate one.

If green plants should stop the manufacture of car-
bohydrates the food supply of the world would soon
be exhausted. All other forms of food are derived from
carbohydrates in some way, and only green plants can
add to the stock that is being drawn upon continually.
This means that green plants must manufacture carbo-
hydrates not only for their own use but also for the use
of animals, and of plants that are not green. Since leaves
are chiefly expansions of green tissue, they are conspicu-
ous in the manufacture of carbohydrates.

It must be remembered that the manufacture goes on
wherever there is green tissue, whether it is found in
leaves or not. A very conspicuous fact about this manu-
facture is that it cannot go on unless the green tissue is
exposed to light. This explains why leaves are adjusted
in so many ways to obtain light.

It also gives name to the process, photosynthesis, the
name indicating that the work is done in the presence of
light. The process demands that carbohydrates shall be
made from raw materials common in nature and easily
obtained by plants, and in photosynthesis two such sub-
stances are used. One of these is water, which in the
plants commonly thought of is absorbed by the roots from
the soil. The other substance is carbon dioxide, a gas
present in small proportion in the air (really in the form

PLANT STRUCTURES 225

of carbonic acid gas), but one which is being constantly
renewed as it is used, so that it is always available. Water
is made up of one part of oxygen and two parts of hy-
drogen, while carbon dioxide consists of two parts of
oxygen and one part of carbon. These are just the ele-
ments that enter into the structure of a carbohydrate.

In photosynthesis the elements of water and carbon
dioxide are separated, and recombined to form a carbo-
hydrate, and in this process oxygen is a waste product
and is given off by the working cells. Therefore, in the
sunlight a leaf is absorbing carbon dioxide and giving
off oxygen, and this gas exchange is the superficial indi-
cation that photosynthesis is going on.

"Such an important organ as the leaf," says Coulter
again, "with its delicate active cells necessarily in com-
munication with the air, is exposed to numerous dangers.
Conspicuous among these dangers are drought, intense
light and cold. Perhaps the most common danger to most
plants is an excessive loss of water, and when a drought
prevails the problem of checking transpiration is a most
serious one. As the leaves are the prominent transpiring
organs, the chief methods of protection concern them.

The epidermis may be regarded as an ever-present
check against transpiration, for without it the active meso-
phyll cells would soon lose all their water. In some plants
of very dry regions what may be regarded as several epi-
dermal layers appear. The cuticle which is often de-
veloped upon the epidermis is one of the best protections
against loss of water. It is developed by the exposed
walls of the epidermal cells, and being constantly renewed
from beneath, it may become very thick and many-lay-
ered. In dry regions, or in any much exposed place, the
cuticle is a very constant feature of plants.

"In many leaves," remarks Atkinson, "certain of the
cells of the epidermis grow out into the form of hairs or
scales." They may form only a slightly downy covering
or the leaf may be covered by a woolly or feltlike mass so

226

BOTANY

that the epidermis is entirely concealed. In dry or cold
regions the hairy covering of leaves is very noticeable,
often giving them a brilliant silky white or bronze look.

In dry regions each leaf endeavors to expose as small a
surface in proportion to substance to the drying air
and intense light. That this reduction in size holds a
direct relation to the dry conditions is evident from the
fact that the same plant often produces small leaves in
a dry region and larger ones in moist conditions. In the
case of the cactus, a large group in the dry regions of

6 — Day (A.) and Night (B.) Positions of a Clover-like
Plant.

the Southwest, the leaves have become so much reduced
that they are no longer used in photosynthesis, and this
process is carried on by the green tissue of the globular,
cylindrical, or flattened stems. The rosette habit is a
very common method of protection used by small plants
growing in exposed situations, as bare rocks and sandy
ground. The clustered, overlapping leaves form a very
effective arrangement for resisting intense light or
drought.

There are leaves which can shift their positions ac-
cording to their needs, directing their flat surfaces
toward the light, or more or less inclining them. Such
loaves have been developed most extensively in the

PLANT STRUCTURES 227

great family to which peas and beans belong, the most
conspicuous ones being those of the so-called sensitive
plants. The name has been given because the leaves re-
spond to various external influences by changing position
with remarkable rapidity. A slight touch, or even jarring,
will call forth a response from the leaves, and the sudden
application of heat gives striking results.

Insect-devouring plants usually grow in swampy regions,
the leaves forming small rosettes upon the ground. In one

Fig. 7 — Sensitive Plant Before and After Shock.

form of sundew the blade is round and the margin is beset
by prominent bristle-like hairs, each with a globular gland
at its tip. Shorter gland-bearing hairs are scattered also
over the inner surface of the blade. All these glands
excrete a clear, sticky fluid, which hangs to them like
dewdrops, and which, not being dissipated by sunlight,
has suggested the name sundew. If a small insect becomes
entangled in one of the sticky drops the hair begins to
curve inward, and presently presses its victim down upon
the surface of the blade. The famous 'Venus Flytrap' is
found only in certain sandy swamps in North Carolina.

228

BOTANY

The leaf-blade is constructed so as to work like a steel
trap, the two halves snapping together, and the marginal
bristles interlocking. A few sensitive hairs, like feelers,
are developed on the leaf surface, and when one of these is
touched by a small flying or hovering insect the trap snaps
shut and the insect is caught. Only after digestion, which
is a slow process, does the trap open again.

The stem is distinguished as that part of the plant which
bears the leaves. "It has for its chief function," says C. C.

Fig. 8 — Transverse Sections of Stems,
Secondary. (Strasburger.)

Primary and

Curtis, "the production and display of the leaves and roots
and the conduction of the materials which these organs
are especially concerned in handling. It serves as a con-
nection between them, carrying up the material absorbed
by the roots and distributing the various substances re-
ceived from the leaf." The stem may be compared to a
system of transportation carrying building material for
new cells and arranging for the bearing away of that
which is waste.

The stem best adapted for the proper display of leaves is
generally upright, for they can be spread out on all sides
and carried upward toward the light. To maintain the

PLANT STRUCTURES

229

erect position is not a simple mechanical problem, and in
large, woody stems it involves an extensive development
and arrangement of supporting tissues. Other stems lie
along the ground bearing leaves only on the free side,
while a third great group is that of the climbers, which
use other plants as supports. The great lianus of South
America belong to this class.

Fig. 9 — Transverse Section of Woody Stem.
pi., primary cortex; c, cambium ring; cr., bast; pm., primary
medullary ray; pm'., expanded extremity of a primary medul-
lary ray ; sm , secondary medullary ray ; g., limit of third
year's wood. (Strasburger.)

It has been shown that the stem is in a sense a trans-
portation system, and it becomes immediately evident
that the material transported must be largely in soluble
form. This liquid is known as sap. "It is important to

230 BOTANY

notice," say J. Y. Bergen and C. M. Davis in their 'Prin-
ciples of Botany,' ''that sap is by no means the same sub-
stance everywhere and at all times. As it first makes its
way by osmotic action inward through the root hairs of
the growing plant it differs little from ordinary well water.
The liquid which flows from the cut stem of a tree just
before the buds have begun to burst in the spring is mainly
water often with a little dissolved organic acids, proteids
and sugar. The sap which is obtained from maple trees

Fig. 10 — Cross-section Through Sunflower Stem.
M., pith ; X.. xylem, containing spiral (s., s/) and pitted (c, e.')
vessels; C, cambium; P., phloem, containing sieve vessels
(sb.) ; b., a mass of bast fibers ; ic, pith rays between the
bundles ; e., starch sheath ; R., cortex.

in late winter or early spring is far richer in nutritious
material, while the elaborated sap which is sent so abun-
dantly into the ear of the corn at the time of its filling out
contains great stores of food to support plant or animal
life."

Most root-forms are adapted for growth in the soil, but
there are many of which this is not true. Thus many of
the orchids have aerial roots which fasten the plants to
the branch of a tree and absorb moisture from the heavy

PLANT STRUCTURES 231

humid air of a tropical forest; others are adventitious, like
the ivy, which cause the plant to cling to a wall ; others
again, like the mistletoe and the dodder, are parasitic and
are adapted to prey upon their host, while another large
group of roots are adapted to life in the water, such as the
duck-weed.

The length of roots is rarely realized. Thus winter
wheat has been found to extend to a depth of seven feet,
and the average root stretch of a plant of common oats is
154 feet. The Mexican mesquite has been known to ex-
tend sixty feet below ground in the search for water.

The growing tip of each root and rootlet is protected
by a cap of cells called the root-cap. This root-cap
consists of several layers of cells, the outer ones grad-
ually dying or being worn away as the tip of the root
pushes through the soil, and being replaced by new layers
which are continually forming beneath.

A short distance behind the root-cap the surface of
the root becomes covered by a more or less dense growth
of hairs, known as root-hairs. These hairs are out-
growths, sometimes very long ones, from the superficial
cells, a single cell producing a single root-hair. In fact,
the root-hair is only an extended part of the superficial
cell The root absorbs water and materials dissolved
in it from the soil, and the root-hairs enormously increase
the absorbing surface. Thousands may occur on a square
inch of surface.

In the center of a young root is a solid vascular cylinder,
often called the central axis, sometimes enclosing pith.
Investing the solid vascular cylinder of the root is the
cortex, which often can be stripped from the central axis
like a spongy bark.

The wood (xylem) and the bast (phloem) of the vas-
cular cylinder do not hold the same relation to each
other as in the stem. The vascular cylinder, instead of
being made up of vascular bundles, with wood toward
the center and bast toward the outside, as in stems, is

232

BOTANY

made up of wood and bast strands alternating with each
other around the center. The wood strands radiate from
the center like the spokes of a wheel, and the bast strands
are between these spokes, near their outer ends. This

embryonal stage ; B. and C, elongatin;
(Giesenhagen.)

Cells from Root-bark.

or growing stages.

arrangement of wood and bast is peculiar to roots. The
vascular bundles of the root connect with those of the
stem, and these in turn with those of the leaves, so that
throughout the whole plant there is a continuous vascular
system.

CHAPTER III

REPRODUCTION STRUCTURES

The root, the stem, and the leaf being the three prin-
cipal organs in the nutrition of a plant, the matter next
of importance is a consideration of the manner of its
reproduction. Usually this is popularly supposed to be
by a flower, but a large division of plants are flowerless
and reproduce in many diverse ways. As, moreover, the
mode of reproduction often constitutes a means of differ-
entiating between various species, it will be treated
therein, but certain main principles may be laid down.

Thus the earliest form of reproduction is that of mere
cell division, which cell, so far as can be seen, is not
marked out from other cells; indeed, all the cells are
capable of division. Next comes the setting aside of a
certain cell which is called a spore ; and what seems
strange in the vegetable world, certain of these, by the
lashing about of filaments, are able to swim, and are
called 'swimming spores.' So far all has been without
sex, and is called 'asexual/

But, still very early in the plant kingdom, two cells
very like the swimming spores, yet different in action,
are produced, which are called 'gametes'; these have an
affinity for each other, come together, fuse or fertilize,
and, thus fertilized, are called "zygospores," and from
these are thrown off spores which can produce new plants.
These two gametes at first are very similar, but in higher
forms become strongly dissimilar, and are called sperms
233

234 BOTANY

and eggs. The organ producing the sperms is called the
'antheridium,' that producing the egg is known as the
'oogonium,' in still higher types the 'Archegonium.' The
last stage in this type of reproductive process is that in
which different plants (sometimes different stems) pro-
duce sex organs which may be termed respectively male
and female. The highest and the vast division of the
Plant Kingdom, known as 'Spermatophytes,' or seed-
bearing, is so called because of its development of seeds
and reproduction thereby. The gymnosperms, of which
pine trees are the best known, produce no flowers, but
the Angiosperms have the sexual system very fully de-
veloped in the flower.

A flower is a highly modified stem peculiarly adapted
for perpetuation. The stem-like nature of the flower is
very noticeable before it opens, at which time a series of
leaves protects the delicate parts within. These green
leaves are known as the calyx, each leaf of which is sep-
arately distinguished as a sepal. "As the bud opens," says
Curtis, "a number of organs are disclosed ; particularly
noticeable are a set of variously colored leaves known as
the corolla, each leaf of which is called a petal. Within
the perianth (which is the calyx and corolla together) are
two kinds of organs, the pistils and the stamens, collec-
tively known as sporophylls, since their special work is to
produce certain cells called spores." The anthers dis-
charge pollen, which is carried in various ways to the
pistil, where the ovules are situated. It is by the fertiliza-
tion of the female nucleus of the egg-cell at the apex of
the embryo sac in the pistil by the male nucleus from a
pollen grain that plants arise.

The transfer of the pollen to the pistil. — This transfer —
i.e., pollination — is effected in many Angiosperms by in-
sects, altho in some cases the wind serves to carry pollen,
as it does in the Gymnosperms. This mutually helpful
relation between flowers and insects in some cases has
become so intimate that thev cannot exist without each

REPRODUCTION STRUCTURES

^3S

other. Flowers are modified in many ways in relation to
insect visits, and insects are variously adapted to flowers.
"The pollen/' Coulter points out, "may be transferred to
the stigma of its own flower, 'self-pollination/ or of some
other flower of the same kind, 'cross-pollination.' In the
latter case the two flowers concerned may be upon the
same plant or upon different plants, which may be quite
distant from one another. Since flowers are very corn-

Fig. 12 — Various Forms of Pollen Granules. (Wettstein.)

monly arranged to secure cross-pollination, it must be
more advantageous in general than self-pollination.

"The advantage of this relation to the insect is to
secure food. This the flower provides in the form of
either nectar or pollen ; and insects visiting flowers may be
grouped as nectar-feeders, represented by moths and but-
terflies, and pollen-feeders, represented by the numerous
bees and wasps. The presence of these supplies of food
in the flower is made known to the insect by the display
of color, by odor, or by form. Moreover, the flower not
only must secure the visits of suitable insects but also
must guard against the depredations of unsuitable ones."

236

BOTANY

Cross-pollinating flowers may be illustrated under three
heads, distinguished from one another by their methods
of hindering self-pollination; but it must be understood
that almost every kind of flower has its own way of solv-
ing the problems of pollination. The following illustra-

Explosive Pollination.

1.. insect, touching style, bursts open flowers with a cloud of pol-
len ; 2., bee's weight releasing keel, style and stamens spring
up with a jerk, ejecting pollen. (Kerner.)

tion will serve to show one of the processes, that de-
pendent upon position. In this case the pollen and the
stigma are ready at the same time, but their position in
reference to each other, or in reference to some confor-
mation of the flower, makes it unlikely that the pollen
will fall upon the stigma.

REPRODUCTION STRUCTURES

237

In the family Leguminosa, to which the pea, bean, etc.,
belong, the several stamens and the single carpel are in
a cluster enclosed in a boat-shaped structure, 'keel,' formed

Fig. 14 — Diagrammatic Section of Ovary and Ovule.
At the moment of fertilization in angiosperm. The track of the
pollen tube is shown down through the style and the walls of
the ovary to the micropylar end of the embryo sac.

by two of the petals. The stigma is at the summit of the
style and projects somewhat beyond the pollen sacs, some
of whose pollen lodges on a hairy zone on the style be-
low the stigma. While the stigma is not altogether se-
cure from receiving some pollen, the position does not

238

BOTANY

favor it. The projecting keel is the natural landing place
for a bee visiting the flower; and it is so inserted that
the weight of the insect depresses it and the stigma comes

Fig. 15 — Development of the Ovule and Embryo of the
Shepherd's Purse.

A., young ovule; B., outer integument (oi.) growing beyond inner
(ii.), showing young embryo sac (es.) ; C, diagram showing
mature ovule ; D., development of the suspensor (s.) ; E.,
early divisions of terminal to form embryo ; F., later stage
of same; G., later stage showing two cotyledons (c.) and
root region (r.) ; H., longitudinal section of ovule ; em.,
embryo sac; s., suspensor; e., endosperm; ii., inner integu-
ment; m., micropyle. (Bergen and Davis.)

REPRODUCTION STRUCTURES

239

in contact with its body. Not only does the stigma strike
the body, but by the glancing blow the surface of the
style is rubbed against the insect; and upon this style,
below the stigma, the pollen has been shed, and is rubbed
off against the insect. At the next flower visited the

Fig. 16 — Seedling of Bean.
A., embryo removed from testa ; B., young seedling, showing
hypocotyl, cotyledons and epicotyl ; C, older seedling, show-
ing the first internode and leaves of the stem. (Gray.)

stigma is likely to strike the pollen obtained from the
previous flower, and the style will deposit a new supply
of pollen.

But in the general flower, as visited by the insect, the
pollen grains that reach the stigma, the specially pre-

24o BOTANY

pared surface for receiving them, begin to put out pollen
tubes. These tubes grow through the stigma and enter
the style; grow down the style and enter the cavity of
the ovary; reach the ovules and enter their micropyles;
and finally penetrate the ovule to the egg. Throughout

Pig. 17 — Seedling of White Mustard, Showing Positive
Phototropism of Stem and Negative Phototropism of Root.

this progress of the tube the male cells are in its tip, and
when the egg is reached they are discharged from the
tube and one of them fuses with the egg. This is the
act of fertilization, and through it the egg becomes an
oospore.

An important difference between Gymnosperms and

REPRODUCTION STRUCTURES 241

Angiosperms should be noted here. In Gymnosperms the
pollen reaches the ovules, for they are exposed, but in
Angiosperms the pollen reaches only the surface (stigma)
of the pistil that encloses the ovules.

The oospore, lying in the midst of the ovule, at once
begins to germinate, and forms a young plant, or embryo.
When the embryo is forming, the ovule develops a hard
coat outside, and a seed is the result.

The seed coats are varied in many ways, as in the pea
and the Brazil nut, but their internal anatomy follows the
same general pattern, and they nearly all contain food for
the embryonic plant. It is this food in grains and in
nuts which is used as foodstuff by man. The three kinds
of food stored in seeds are starch, oil and albuminous sub-
stances called proteids. The young seedling does not push
its way straight out of ground, but sends up an arched part
of the steam, known as the hypocotyl, and when the sur-
face of the ground is broken the stem straightens and the
cotyledons appear.

The lower elongating tip of the hypocotyl directs its
growth downward — that is, toward the earth — even if it
has to curve about the seed to do so. It is exceedingly sen-
sitive to surrounding influences, a condition that is called
irritability, especially so to gravity, a condition that is
called geotropism, the root being said to be geotropic. If
the same stimulus and response that directs the root-tip to-
ward the soil continues to direct it within the soil it con-
tinues to grow directly downward and becomes a tap-root.
When such a root, having entered the soil, begins to send
out branches, these do not respond to the stimulus of
gravity as does the tap-root, for they extend through the
soil in every direction. It is likewise sensitive to light, the
stem being attracted and the root repelled. With the
establishment of roots in the soil, and the exposure of
green leaves to the light and air, germination is over,
for the plant is able to make its own food.

CHAPTER IV

TAX0N0M1C BOTANY

The first great division of the plant kingdom comprises
the Algae and Fungi, grouped under the term 'Thallo-
phytes, meaning plants wherein such special vegetative or-
gans as leaves and roots are either lacking or rudimen-
tary.

The Algae grow in the water, and hence their habits are
adapted to a water environment. They are often called
sea-weeds, but altho they are very abundant along sea-
coasts they are also found in fresh waters. Some of them
are so small that the individual bodies are visible only
under the microscope, but others are large, the sea-kelp
having been known to have a stem nine hundred feet long.

Altho all algae contain chlorophyll, and hence are able
to make their own food, they do not all appear green, for
in many of them the chlorophyll is obscured by other col-
oring matters. The four great groups of Algae are named
from the general color of their bodies.

The Blue-Green Algae, or the 'Green Slimes,' form blue-
green or olive-green patches on damp tree trunks, rocks
and walls. The name of the group refers to the fact
that in addition to the chlorophyll the cells contain a
characteristic blue coloring matter which does not mask
the green, but combined with it gives a bluish-green tint
to the plants when seen in masses. Not all the blue-green
Algae are bluish-green in tint, however, for the presence
of other substances may disguise it, and the color may
242

TAXONOMIC BOTANY

243

be yellow, or brown, or even reddish. The color of the
Red Sea, which has given it its name, is due to the pres-
ence under certain conditions of immense quantities of
one of the blue-green forms.

The green algae are so named because the green of
the chloroplasts is neither modified nor obscured by other
colors, and the slants have a characteristic grass-green

-Two Types of Marine Alce, Gulf-weed and Rock-
weed, 'Fucus/ (Luerssen.)

color. Some of the green algae are associated with the
blue-green algae in the pollution of water reservoirs.

The brown algae, of which the giant kelp of the Pacific
coast, with a length of 900 feet, is the largest, are all
anchored plants, chiefly marine. The first great group
of brown algae, of which a small form, Ectocarpus, is a
well-known representative, is distinguished by its swim-
ming spores and its similar gametes. The smaller group,
besides the common "rock-weed" or Fucus, contains the

244 BOTANY

famous gulf-weed, or Sargasso weed, which makes a float-
ing bank of dense weed in the North Atlantic, known as
the Sargasso Sea. These differ from the first group in
producing no swimming spores, and in its dissimilar
gametes (eggs and sperms).

The red algae are mostly marine forms, and receive
their name from the fact that a red coloring matter com-
pletely masks the chlorophyll. As a consequence the
plants are various shades of red, violet, dark purple, and
reddish brown, often beautifully tinted. In general, the
bodies are much more graceful and delicate than those
of the brown algae. There is the greatest variety of
forms, branching filaments, ribbons, and filmy plates pre-
vailing; and often profuse branching occurs, the plants
resembling mosses of delicate texture.

The reproduction of the red algae is very peculiar, be-
ing entirely unlike that of the other algae. No swimming-
spores are produced, but sporangia occur that produce and
discharge spores without the ability to swim. Since each
sporangium usually produces four such spores, they are
called tetraspores. Floating about in the water, instead
of actively swimming, they finally germinate and pro-
duce new plants. The sexual reproduction, however, is
most remarkable. The sperms, like the tetraspores, are
without cilia, and simply float into contact with the carpo-
gonium, whose form is like that of a flask with a long,
narrow neck. In the bulbous base of the carpogonium
the female cell is developed. In a very simple case the
floating sperm comes in contact with the long neck, the
two walls become perforated at the point of contact, the
contents of the sperm enters and passes to the carpo-
genic cell, and thus fertilization is accomplished. As a
result of fertilization there appears on the plant a spore-
containing structure like a little fruit. The spores it con-
tains produce the alga plants again.

The Fungi do not contain chlorophyll, and this fact
forms the sharpest contrast between them and the algae.

TAXONOMIC BOTANY

24.5

The presence of chlorophyll enables the algae to be inde-
pendent of any other organism, since they can manufac-
ture food out of carbon dioxide and water. The ab-
sence of chlorophyll compels the Fungi to be dependent
upon other organisms for their food. This food is ob-
tained in two general ways: either (1) directly from
living plants and animals, or (2) from organic waste
products or dead bodies. In case a living body is attacked

m^ is1

Fig. 19 — Micro-organisms of Bacteria.
1., 'blood-portent' (found in 'red' rains) ; 2., the same, in zooglea
form ; 3., the vinegar fermentation ; 4., the same, highly mag-
nified; 5., Asiatic cholera; 6., the same, highly magnified;
7., anthrax and red-blood corpuscles ; 8., the same, highly
magnified; 9., relapsing fever; 10., sarcina ventriculi. (Ker-
ner.)

the attacking fungus is called a 'parasite/ ana the plant
or animal attacked the host. In case the food is obtained
in the other way the fungus is called a 'saprophyte.' For
example, the rust that attacks wheat is a parasite, and the
wheat is the host; while the mold which often develops
on stale bread is a saprophyte.

Bacteria include the smallest known living forms of
fungi, some of which are spherical cells only V25000 inch

246 BOTANY

in diameter. It is estimated that 1,500 of certain rod-
shaped forms, placed end to end, would about stretch
across the head of an ordinary pin. Even to distinguish
ordinary bacteria, therefore, the highest powers of the
microscope are necessary. However, they are so very
important to man, on account of their useful and destruc-
tive operations, that every student should have some in-
formation about them. Public attention has been drawn
to them chiefly on account of the part they play in many
infectious diseases.

Bacteria are found almost everywhere — in the air, in
the water, in the soil, in most foods, and in the bodies
of plants and animals, as regular inhabitants. Many of
them are entirely harmless, some are useful, and others
are very dangerous. The 'pure' water of springs and wells
contains abundant bacteria, while in stagnant water and
sewer water they swarm in immense numbers.

Reproduction is by cell division, as among the blue-
green algae, a group which the bacteria resemble in many
ways. This cell division is remarkably rapid in bacteria,
resulting in such prodigious multiplication of individuals
in a comparatively short time that it is impossible to im-
agine what would happen if bacteria were left free to
reproduce to their full capacity. Bacteria have been ob-
served to reproduce themselves in fifteen to forty minutes
after their formation ; that is, a single generation of such
bacteria is that length of time. It would be interesting
to determinate the number of progeny from a single bac-
terium at the end of twenty-four hours if such a rate were
maintained.

Yeasts are much larger than bacteria and have a more
complex cell structure, for there is present a clearly de-
fined nucleus. The cells reproduce in a peculiar method
called 'budding/ This consists in a cell putting out one
or more projections which gradually enlarge and finally
become pinched off. Often the cells thus produced cling
together in short, irregular chains. The chief interest

TAXONOMIC BOTANY 247

in connection with yeasts is the important part they
play in the fermentation of sugar solutions, "splitting"
the sugar into alcohol and carbon dioxide, a process also
induced by certain bacteria, but chiefly by the yeasts.

Fermentation by yeasts is employed on a large scale in
the manufacture of beer, wine, and spirits, and in the
making of bread. In the last-named process the dough i&

Fig. 20 —Diagram of Bread Mold. (Mucor.)
a.v b., c, three sporophores ; c, mature.

inoculated with yeast plants and placed in a sufficiently
warm temperature to induce rapid growth. The plants
begin to reproduce actively by budding, the sugar in the
dough is split into alcohol and carbon dioxide, and the
latter, a gas, expands and puffs up the dough, making it
light and porous ; that is, causing it to "rise."

One of the most common of the Mucors, or 'bread molds,'
forms white, furry growths on damp bread, preserved

248 BOTANY

fruits, manure heaps, etc. It may be grown easily by
keeping a piece of moist bread in a warm room under
a glass vessel. The sources of its food supply indicate
that it is a saprophyte.

Rusts are destructive parasites that attack almost all
seed plants, but those that attack the cereals are of spe-
cial importance. Wheat, oats, rye and barley all have
their rusts, and in the United States there is a yearly
loss of several million dollars on account of the ravages
of the wheat rust alone, scarcely a field being entirely
free from the pest. Naturally, these parasites have been
investigated persistently, but while very much has been
learned about their life histories and behavior no remedy
has been discovered. It has been found that certain va-
rieties of wheat resist the rust better than others and
that varieties ripening early escape serious injury; and
these facts may lead to the breeding of resistant and
early races.

The popular idea of a fungus is that of a fleshy, color-
less form, such as the mushroom. This name is very in-
definite, being sometimes applied to any of the fleshy
fungi of the umbrella form, and sometimes including
among such forms only those that are edible, the poison-
ous forms being spoken of as toadstools.

The life history of the ordinary edible mushroom of
the markets will serve as an illustration. The mycelium
of white, branching threads spreads extensively through
the substratum of decaying organic material, and by those
who grow mushrooms is called spawn. This mycelium,
altho the least conspicuous part of the mushroom, is, of
course, the real vegetable body. Upon this underground
mycelium little knoblike protuberances arise (buttons),
growing larger and larger until they develop into the
umbrella-like structures commonly spoken of as mush-
rooms. This umbrella-like structure, however, corresponds
to the sporophores that arise from the mycelia of other
groups of fungi, except that it includes a large number

TAXONOMIC BOTANY 249

of sporophores organized into a single large body. There-
fore, the real mushroom body is a subterranean mycelium,
upon which the structures commonly called mushrooms
are the spore-bearing branches. In pulling up a mush-
room, fragments of the mycelium may often be seen at-
tached to it, looking like small rootlets.

The puffballs are fleshy fungi that differ from the
mushrooms in having the spores enclosed until they are
ripe. There is a subterranean mycelium, as in the mush-
rooms, but the spore-bearing structure is a fleshy, globu-
lar body containing irregular chambers lined with the
spore-producing layer. When young this body is solid
and white, but as the spores mature it becomes yellowish
and brownish, gradually dries up, and finally is only a
brown, parchment-like shell containing innumerable ex-
ceedingly small spores that are discharged by the break-
ing of the shell. Some of the puffballs become very large,
reaching a diameter of twelve to eighteen inches.

Lichens are abundant everywhere, forming splotches of
various colors on tree trunks, rocks, old boards, etc. They
have a general greenish-gray color, but brighter colors
also may be observed. The great interest connected with
lichens is that they are not single plants, but that each
lichen is formed of a fungus and an alga living together
so intimately as to appear like a single plant. In other
words, a lichen is not an individual, but a firm of two
individuals very unlike one another. If a lichen be sec-
tioned the relation between the two constituent plants
may be seen. The fungus makes the bulk of the body
with its interwoven mycelial threads, in the meshes of
which lie the algae, sometimes massed. It is these en-
meshed algae, showing through the transparent mycelium,
that give the greenish tint to the lichen. It has been
found that the lichen-alga can live quite independently
of the lichen-fungus. On the other hand, it has been
found that the lichen-fungus is completely dependent upon
the algae, for the germinating spores of the fungus do not

250

BOTANY

develop far unless the young mycelium can lay hold of
suitable algae. Artificial lichens also have been made by
bringing together wild algae and lichen-fungi. Lichens,
therefore, are really combinations of a parasitic fungus
and its host, the parasitism being peculiar in that the
host is not injured. The fungus lives upon the food made
by the alga, and the relation suggested is that the alga
is enslaved by the fungus.

Fig. 21 — Foliose Lichen Growing Upon a Board. (Coulter.)

With the Liverworts a new division of the Plant King-
dom is entered, known as the Bryophytes, possessing
'archegonia,' but no vascular system. Among these the
simplest of the archegonia forms' are found.

Mosses are very abundant and familiar plants. They
grow in all conditions of moisture ; many of them can
endure drying out wonderfully, and hence they can grow
in very much exposed situations, as do many lichens. In
fact, lichens and mosses, being able to grow in the most
exposed situations, are the first plants to appear upon

TAXONOMIC BOTANY

251

bare rocks and ground, and are the last plants seen in
climbing* high mountains or in going into very high
latitudes.

Mosses have great power of vegetative multiplication,
new leafy branches putting out from old ones indefinitely,
thus forming thick carpets and masses. Bog mosses often
completely fill up bogs or small ponds and lakes with

Fig. 2

Mosses.

germinating spore ; 2., protonema ; 3., bud from protonema ;
4., section of tip of male shoot with antheridia ; 5., tip of
female shoot with archegonia ; 6., developed sporogonium.
(Kerner.)

a dense growth, which dies below and continues to grow
above, so long as the conditions are favorable. These
quaking bogs, or "mosses," as they are sometimes called,
furnish very treacherous footing unless rendered firmer
by other plants.

The conspicuous part of an ordinary moss plant con-
sists of a more or less erect and usually branching stem
bearing numerous delicate leaves. The plant is evidently

252 BOTANY

able to make its own food, and it is anchored to its sub-
stratum by hairlike rhizoids. Its power of vegetative
propagation has been described. At certain times there
appears at the end of the main stem, or at the end of a
branch, a rosette of leaves, often called the moss flower.
In the center of this rosette there is a group of antheridia
and archegonia, sometimes both kinds of organs in a single
rosette, sometimes only one kind. From the fertilized egg
cell of the archegonium arises the capsule containing
spores (sporophyte), from which the new moss plant
springs.

The third division, or Pteridophytes, is represented first
by the ferns, but also includes the 'horsetails' and club
mosses. The ferns are well-known plants and the ordi-
nary forms are easily recognised; in fact, the general
appearance of the large compound leaves is so characteris-
tic that when a leaf is said to be fernlike a particular
appearance is suggested. In the tropics not only are great
masses of the low forms to be seen, from those with
delicate and filmy, mosslike leaves to those with huge
leaves, but also tree forms with cylindrical trunks en-
cased by the rough remnants of fallen leaves, and some-
times rising to a height of thirty-five to forty-five feet,
with a crown of great leaves fifteen to twenty feet long.

If an ordinary ferri be examined it will be discovered
that it has a horizontal underground stem or rootstock,
which sends out roots into the soil and one or more
large leaves into the air. These leaves, appearing to
come directly from the soil, were once supposed to be
different from ordinary leaves, and were called fronds;
but altho the name is still used in connection with fern
leaves it is neither necessary nor accurate. These leaves
are usually compound, branching either pinnately or pal-
mately. There are two peculiarities about fern leaves
that should be noted. One is that in expanding the leaves
seem to unroll from the base, as tho they had been rolled
from the apex downward, the apex being in the center

TAXONOMIC BOTANY 253

of the roll. When unrolling this gives the leaves a
crozier-like tip. The other peculiarity is that the veins
fork repeatedly. This combination of unrolling leaves and
forking veins is very characteristic of ferns.

"Probably the most important fact about the fern body,"
says Coulter, "is that it contains a vascular system. The
appearance of this system marks some such epoch in the
evolution of the plants as is marked among animals by
the appearance of the backbone. As animals are often
grouped as vertebrates and invertebrates, so plants are
often grouped as vascular plants and non-vascular plants,
the latter being the Thallophytes and the Bryophytes, the
former the ferns and the seed plants. The presence of
this vascular system means a special conducting system,
and in connection with it there are developed the first
roots and the first complex leaves.

"On account of the vascular system, and other resistant
structures, the remains of ferns have been preserved in
great abundance in the rocks. These records show that
the ferns are a very ancient group, occurring in special
abundance during the Coal-measures.

"Another striking fact about this leafy body of the
ferns is that it never produces sex organs, but does pro-
duce spores abundantly. This means that it is the sporo-
phyte in the life history of the fern, and when it is
contrasted with the sporophyte of Bryophytes the differ-
ences are remarkable. Among the liverworts and the
mosses the sporophyte is a leafless structure attached to
the gametophyte, and dependent on it, while the gameo-
phyte is the leafy body doing chlorophyll work. Among
the ferns, however, the sporophyte is an elaborate leafy
structure and entirely independent. Therefore, when one
ordinarily speaks of a moss and a fern, the gametophyte
is referred to in the former case and the sporophyte in
the latter. This means that in passing from mosses to
ferns plants have transferred the chief work of food

254

BOTANY

manufacture from the gametophyte to the sporophyte,
which has thus become the conspicuous generation.

"The sharp and easily marked distinction between the
prothallus (gametophyte) and the fern plant itself

Fig. 23 — Life History of a Fern.
a fern prothallium seen from under side ; 2., section of arche-
gonium ; 3., antheridium ; 4., escape of spermatozoids ; 5.,
young sporophyte; 6. complete sporophyte; 7., under surface
of pinnule of (6.) ; 8., a young prothallium. (Kerner.)

(sporophyte) has led certain writers on "biology" to
consider the fern as a typical plant for the purpose of
comparison with certain typical animals which are as-

TAXONOMIC BOTANY

255

sunied to represent a similar stage of evolutionary de-
velopment. Aside from the dangers which arise from
such an assumption, it must be said that in many respects
ferns are not typical. They should not be regarded as
the ancestors of the present flowering plants, but as a

Fig. 24 — Normal Secondary Growth of Conifer Wood.
1., Wedge-shaped section, showing ten years' growth; 2., enlarged
portion, showing the anatomical characters of a year's growth.

somewhat highly specialized offshoot from the main line
of descent which at the present geological age is not
"biologically successful" in competition with the seed-
bearing forms."

The Gymnosperms are one of the two groups of seed

256 BOTANY

plants, the most familiar ones in temperate regions be-
ing pines, spruces, hemlocks, cedars, etc., the group com-
monly called evergreens. It is an ancient group, for its
representatives were associated with the giant club mosses
and horsetails in the forest vegetation of the Coal-meas-
ures. Only about four hundred species exist to-day as a
remnant of its former display, altho it still forms exten-
sive forests. Gymnosperms are very diverse in habit.
They are all woody forms, but they may be gigantic trees,
trailing or straggling shrubs, or high-climbing vines.
There are two prominent living groups of Gymnosperms.

Cycads are tropical forms with large fernlike leaves.
The stem is either a columnar shaft, crowned with a ro-
sette of large compound leaves, with the general habit
of tree-ferns and palms, or they are like great tubers,
crowned in the same way. The tuberous stems are often
more or less buried. In ancient times cycads were very
abundant, but now they are represented by about eighty
species, scattered through the Oriental and Occidental
tropics. They are especially interesting in their resem-
blances to ferns, and some of them might be mistaken
for ferns did they not bear large seeds.

Conifers are the common Gymnosperms, often forming
great forests in temperate regions. Some of the forms
are widely distributed, as the pines, while some are now
very much restricted, as the gigantic redwoods, 'Sequoia/
of the Pacific slope. The habit of the body is quite char-
acteristic, a central shaft extending to the very top. In
many cases the branches spread horizontally, with di-
minishing length at the top, forming a conical outline,
as in the firs. This habit gives the conifers an appearance
very distinct from that of the other trees.

The large cone of the pine is made up of sporophylls
that become very thick and hard, and that are packed1;
closely together until they spread apart to let out the
seeds. On the upper side of each sporophyll, near its
base, there are two sporangia, in each one of which there

TAXONOMIC BOTANY

257

is a single large spore (megaspore). So large is the
spore that it looks like a conspicuous cavity in the center
of the sporangium. These structures also bear old names
that may be used. The sporangia were called 'ovules/
and the sporophyll bearing them was called a 'carpel/
The large spore was regarded only as a cavity in the
ovule. The cone, therefore, is a group of carpels, and
to distinguish it from the staminate cone it may be called
the 'carpellate cone/

Fig. 25 — Carpellate
Cone of Pine.

A., partly sectioned ;
B., young carpel with
two ovules ; C, old
carpel with mature
seeds.

Fig. 26 — Staminate Cone of Pine.

A., section of cone, showing sporo-
phylls bearing sporangia ; B., sec-
tion of stamen, through one pollen
sac; C, cross-section of stamen,
showing both pollen sacs ; D., the
winged pollen grain. (Strasburger.>,

It is evident that the pine tree, bearing these sporangia,
is the sporophyte in the life history; that is, it is the sex-
less generation. The sporophyte has now become so
prominent that it seems to have become the whole plant.
The pine being heterosporous, there are male and female
gametophytes. The small spores (pollen grains) germin-
ate and produce very small male gametophytes. Only
a few cells are formed, and these remain in the pollen
grain. The single large spore within the ovule is peculiar

258

BOTANY

in never leaving it; it is never shed, but produces a
female gametophyte which lies embedded in the center of
the ovule. The reason, therefore, why the gametophytes
of such plants are not ordinarily seen is that one is within
the pollen grain and the other within the ovule.

"Before fertilization can take place," remarks Coulter,

27 — Cones of Mountain Pine.

"the pollen grain, which develops the male gametophyte
with its sperms, must be brought to the ovule, which con-
tains the female gametophyte with its archegonia. The
pollen grains (microspores) are formed in very great
abundance, are dry and powdery, and are scattered far and
wide by the wind. In the pines and their allies the pollen

TAXONOMIC BOTANY 259

grains are winged, so they are well organized for wind dis-
tribution. So abundant is the pollen of conifers that it .
sometimes falls like a yellow shower, and the occasionally
reported "showers of sulphur" are really showers of pollen
from some forest of conifers. Some pollen must reach the
ovules, and to insure this it must fall like rain. To aid in
catching the falling pollen the scale-like carpels of the cone
spread apart, and the pollen grains, sliding down their
sloping surfaces, collect in a little drift at the bottom of
each carpel, where the ovules are found.

"In this position each of the most favorably placed pol-
len grains begins to put forth a tube (pollen tube). This
tube, containing the two sperms in its tip, grows through
the ovule and reaches the archegonia. Then the sperms
are discharged, and when they reach the egg fusion takes
place and fertilization is accomplished."

The Angiosperms are the flowering plants. In many
flowers there is no regularity in the number of members
in each set. For example, in the water lily petals and
stamens occur in indefinite numbers, and in the buttercup
the same is true of stamens and carpels. In most flowers,
however, definite numbers appear either in some of the
sets or in all of them. When these definite numbers are
present they are prevailingly either three or five; that
is, there are either three or five sepals, petals, stamens
and carpels; altho it is very common to have two sets
of stamens, in which case they number six or ten. These
numbers appear so constantly in great groups that the
two grand divisions of Angiosperms, called Monocotyle-
dons and Dicotyledons, are characterized by them, the
former having the parts of the flower in threes, the latter
in fives. This does not mean that all flowers of these
two divisions have one or the other number, but that
these are the prevailing numbers in case there is a definite
number at all. Not a few Dicotyledons have flowers with
the parts in threes, and a still larger number have them
in fours.

200

BOTANY

In many cases stamens and pistils are not found to-
gether in the same flower. In such cases there are stamin-
ate flowers — that is, those without pistils; and pistillate
flowers — that is, those without stamens. These two kinds
of flowers may be borne upon the same plant, which is
then said to be monoecious (one household) ; or upon dif-

Fig. 28 — Pollination of an Orchid.

wasp alighting; 2., front view of flower; 3., side view with
part of perianth cut away; 4., two pollinia ; 5., wasp, licking
honey, touches pollinia ; 6., wasp leaving flower with pollinia
attached to his head ; 7., wasp visiting another flower, caus-
ing pollinia to touch stigma. (Kerner.)

ferent plants, which are then said to be dioecious (two
households). These terms are applied indifferently to
the plants or to the flowers, either the plants or the flow-
ers being spoken of as monoecious or dioecious. About

TAXONOMIC BOTANY 261

forty monocotyledonous families are recognised, contain-
ing numerous genera and about twenty thousand species.
The Dicotyledons are a much larger group than the
Monocotyledons, containing more than 200 families and
about 100,000 species. Most of them are easily recog-
nised by the floral number five or four, the net-veined
leaves, and the arrangement of the vascular bundles of
the stem in a hollow cylinder.

In the lower stretches of the Dicotyledons there are
a number of small families that include the most common
hardwood or deciduous trees, and this assemblage of con-
spicuous forms may be considered together without se-
lecting any special family. They include elms, sycamore,
walnuts, hickories, oaks, chestnuts, willows, poplars, cot-
tonwoods, birches, beech, etc. These trees are all charac-
terized by their simple and inconspicuous flowers, which
are usually wind-pollinated.

Passing from these forms, which, in the older termi-
nology, are not inaptly described as "apetalous," there is
the very large group of plants which have distinct and
separate petals which are well described by the adjective
polypetalous. It would be impossible in the space at com-
mand to adequately describe or even name the important
plants which come under this head. As a type one might
perhaps take the flower of the flax, the parts of which
are regular and symmetrical, and show, except in the
ovary, no fusion. But there may be wide departure from
forms like these, and the habit of considering any one
flower as a type and the other forms as deviations from
that type is one which the modern botanist eschews.

It is not unreasonable to suppose, however, in a gen-
eral way that the irregular flowers, like the sweet pea, for
example, have, in the evolutionary sense, been the result:
of later development than the simpler and symmetrical
forms. One potent factor in the development of partial
fusions and of flowers which are not radially symmetrical
is probably that of the relation of the flower to insect

262 BOTANY

visitation for the furthering of cross-pollination. A tend-
ency is found in general toward modifications which, as
they can be interpreted, make for the restrictions of the
movements of insects or parts of insects among the floral
organs and thus render more probable the carrying of
pollen from one flower to another.

The culmination of this tendency, along with condition
known as epigyny (the insertion of the calyx, corolla and
stamens on the ovary), is seen in the sympetalous dicoty-
ledonous type. In the sympetalous or gamopetalous flower
the petals are fused into a bell or tube, a condition which
may or may not be accompanied by other fusions. It is
conceded that the Compositese (Sunflowers, Daisies, As-
ters), which are of this sympetalous type, represent the
final and highest development of the dicotyledonous flower.
Composites are found everywhere, but are most numerous
in temperate regions, where they are usually herbs. The
name of the family suggests the most conspicuous feature,
namely, the organization of the numerous small flowers
into a compact head which resembles a single flower, for-
merly called a compound flower.

So common are the Composites that the general struc-
ture of the head should be understood. Taking the head
of Arnica as a type, the outermost set of organs consists
of more or less leaflike bracts or scales, 'involucre,' which
resemble sepals; within these there is a circle of flowers
with conspicuous yellow corollas, 'rays/ which are split
above the tubular base and flattened into a strap-shaped
body, and much resembling petals ; within the ray-flowers
is the broad expanse called the disk, which is closely
packed with very numerous small tubular flowers known
as 'disk-flowers.' If a disk-flower be removed it will be
discovered that the ovary is inferior, and that arising from
it, around the tubular corolla, there is a tuft of delicate
hairs, 'pappus/ vhich represent the sepals. This pappus
surmounting the akene in Composites may be lacking.

CHAPTER V

DEVELOPMENT OF MORPHOLOGY

"We owe the term morphology to Goethe," to quote from
Goebel. He says : 'Scientific men in all times have striven
to recognise living bodies as such, to understand the rela-
tions of their external, visible, tangible parts, and to inter-
pret them as indications of what is within, and thereby in
some measure to gain a comprehensive notion of the
whole. . . . We find therefore in the march of art, of
knowledge and of science many attempts to found and
construct a doctrine which we may name the morphology/
It is quite evident then that morphology does not deal
merely with the distinction and the naming of the outer
parts of plants, altho this, which really belongs to termi-
nology, has been in part incorrectly called morphology.
Morphology does demand the knowledge of the different
appearances of the members of the plant body, but only
as a means to an end ; it requires not isolated facts, but
the relation of facts to one another.

"Terminology can be based on the study of dried plants,
but morphology has, as Goethe stated, to do with "living
bodies," which are involved in changes of a fixed charac-
ter and are subjected to the influences exercized upon
them by the outer world ; it has, in other words, to do with
that part of life phenomena which finds expression in the
external configuration.

"In nature the form and function of an organ stand in
the most intimate relation to each other. Herbert Spencer
263

264 BOTANY

says: "Everywhere structures in great measure determine
functions and everywhere structures are incessantly modi-
fying structures. In nature the two are inseparable co-
operators, and science can give no true interpretation of
nature without keeping their cooperation constantly in
view. An account of organic evolution in its more special
aspects must be essentially an account of the interactions
of structures and functions.

"The first question to which we have to find an answer
is, How came it that the functions of organs were entirely
divorced from morphology?" continues Goebel. "It is,
and rightly so, one of the fundamental declarations of
this study that the function of an organ tells nothing of
its 'morphological significance,' or, in other words, the
same function may be performed by organs of very differ-
ent morphological value; 'homologous' organs must be
distinguished from 'analogous' ones. The tendrils of the
vine and of the passion-flower, for example, are shoot
axes whose leaves are entirely or almost entirely sup-
pressed, but the tendrils of the Leguminosse and of
other plants, altho alike in form and function to those of
the vine and passion-flower, are transformed leaves. The
tendrils in the two cases are analogous ; they are not
homologous.

"This knowledge is one of the weightiest acquisitions of
morphology, but it has been the cause of an incorrect gen-
eralization. Because organs of like morphological signifi-
cance may take on different functions, the functions which
they perform have been considered as of subordinate im-
portance and therefore of no moment in the determination
of the characters of the organs. Hence it has been con-
cluded that they must be entirely neglected in the grouping
of the different members of plants in general categories.

"This conclusion is erroneous. It has led to an unten-
able position, especially in that fundamental problem of
morphology which from the time of Goethe has been
styled the 'Doctrine of Metamorphosis.' By this we un-

DEVELOPMENT OF MORPHOLOGY 265

derstand the fact that manifold as are the organs of plants,
they can be referred back to a few 'fundamental forms'
through whose 'transformation' the many and different
members of the plant body have arisen.

"When we inquire how these primary forms and their
transformations have been represented to us, we meet
with different conceptions on the part of those authors
who have taken pains to reflect upon the idea with which
they dealt. In the idealistic morphology, as it was ex-
pounded by Goethe, A. Braun and Hanstein, the doctrine
of metamorphosis concerned itself with an essentially the-
oretical construction. Goethe himself has plainly stated
his view as follows : 'That which according to our idea is
equal may in reality appear either as equal or as similar
or, indeed, as completely unequal and dissimilar; this is the
essence of the pliant life of nature.' In somewhat other
form this idealistic notion has been preserved, inasmuch as
the history of development was raised by the labors of
K. F. Wolff, R. Brown and Schleiden to the rank of one
of the most important aids to organography. The view
which I have called the 'Differentiation Theory' is based,
as indeed the whole of the doctrine of metamorphosis, on
the study of the transformation of leaves, the manifold
character of which is well known. The differentiation
theory assumes that at the vegetative point of the shoot
indifferent primordia arise which are capable of develop-
ment according to the needs of the plant in manifold ways,
but have this in common — they are leaves. The other
view assumes a real transformation of a primordium in
such a way that, for example, the primordium of a foliage
leaf, instead of developing actually into a foliage-leaf, can
become in the mature condition a leaf of quite a different
character."

That the study of morphology should not have developed
as rapidly as that of systematic is not to be wondered
at, and other than the passing references which will be
found it would be purposeless to dilate upon the crude

266 BOTANY

ideas of the earlier writers. While it cannot be said that he
was by any means the first to consider morphological prob-
lems, in many ways De Candolle's work afforded a sounder
foundation for proper morphological conceptions than
most of his predecessors.

"The efforts of Jussieu, De Candolle and Robert Brown
were directed to the discovery of the relationship between
different species of plants by comparing them together,"
says Sachs. "The doctrine of metamorphosis founded
by Goethe set itself from the first to bring to light the hid-
den relationship between the different organs of one and
the same plant. As De Candolle's doctrine of symmetry
derived the different species of plants from an ideal plan
of symmetry or type, so the doctrine of metamorphosis
assumed an ideal fundamental organ, from which the dif-
ferent leaf-forms in a plant could be derived. The stem
came into consideration only as carrying the leaves; the
root was almost entirely disregarded. As the resemblance
of nearly allied species of plants suggests itself naturally
and unsought to the mind of the unbiassed observer, so
also does the connection between different organs of a
leafy nature in one and the same plant.

"Goethe's conception of the matter was from the first
much less clear and chiefly because he was never able to
bring the abnormal into its true connection with the nor-
mal or ascending metamorphosis. In the first sentence of
his 'Doctrine of Metamorphosis' (1790) he says, 'that it
is open to observation that certain exterior parts of plants
sometimes change and pass into the form of adjacent
parts, either wholly or in a greater or less degree.' In the
cases of which Goethe is here thinking a distinct meaning
can be affixed to the word metamorphosis; if, for example,
the seeds of a plant with normal flowers produce a plant
which has petals in place of stamens, or in which the
ovaries are resolved into green expanded leaves, it is
actually the case that a plant of a known form has given
rise to another plant of a different form; in other words,

DEVELOPMENT OF MORPHOLOGY 267

a change or metamorphosis has really taken place. But
we cannot reason in this way in the case of that which
Goethe calls normal or ascending metamorphosis. For the
plant taken as constant, the idea of metamorphosis has ,'
only a figurative meaning; the abstraction performed by *
the mind is transferred to the object itself, if we ascribe
to it a metamorphosis which has really taken place only in
our conception. The case would be different if we could
assume that the stamens and other organs of the plants
lying before us were ordinary leaves in their progenitors.
So long as this assumption of an actual change is not even
hypothetically made, the expression change or metamor-
phosis is a mere 'idea.' This distinction Goethe has not
made; he did not clearly see that his normal ascending
metamorphosis can only have the meaning of a scientific
fact, if a real change is assumed to take place in the
course of propagation in this case as in that of abnormal
metamorphosis or misformation."

"In the years immediately before and after 1840 a new
life began to stir in all parts of botanical research, in
anatomy, physiology and morphology. Morphology was
now specially connected with renewed investigations into
the sexuality of plants and into embryology, and attention
was no longer confined to the Phanerogams, or flowering
plants, but was extended to the higher and later on to the
lower Cryptogams, or flowerless plants (the old division
of Linnaeus). These researches into the history of devel-
opment first became possible when Von Mohl had restored
the study of anatomy and Nageli had founded and elabo-
rated the theory of cell-formation about the year 1845.
The success of both these inquirers was due to the pre-
vious development of the art of microscopy; it was the
microscope which revealed the facts on which the founda-
tions of the new research were laid, while its promoters
at the same time started from other philosophical princi-
ples than those which had hitherto prevailed among bota-
nists.

268 BOTANY

"Serious attention to microscopy was one of the causes
which introduced the best observers to the practice of
inductive inquiry and gave them an insight into its nature,
and in a few years' time when the actual results of these
investigations began to appear and when a wholly new
world disclosed itself to botanists, especially in the Crypto-
gams, then questions arose on which the dogmatic phi-
losophy had not essayed its ancient strength. The facts
and the questions were new and untouched and presented
themselves to unprejudiced observation in a purer form
than those which during the first three centuries had been
so mixed up with the old philosophy and with the prin-
ciples of scholasticism. "Von Mohl, who only occasion-
ally occupied himself with morphological subjects," says
Sachs, "was a firm adherent of the inductive method,
and was bent on the establishment of individual facts
rather than of general principles; but the founders also
of the new morphology, Schleiden and Nageli, started from
philosophical points of view which, different as they were
in the two men, had yet two things in common, a demand
for severely inductive investigation as the foundation of all
science and the rejection of all teleological modes of ex-
plaining phenomena, in which latter point their opposi-
tion to the idealistic nature-philosophy school was most
distinctly manifested.

"They had indeed one very important point of contact
with this school, the belief in the constancy of organic
forms ; but this belief, not being connected with the Pla-
tonic doctrine of ideas, was with them only a recognition
of everyday observations, and was therefore of less funda-
mental importance, being felt merely as an inconvenient
element in the science. Treating the question in this way,
and influenced by the results of the new researches, they
either inclined to entertain the idea of descent before the
appearance of Darwin's great work or gave a ready assent
to the principle of the new doctrine, tho they expressed
some doubts respecting matters of detail. Hofmeister's

DEVELOPMENT OF MORPHOLOGY 269

researches in morphology and embryology threw an en-
tirely new light on the relations of affinity between the
great groups in the vegetable kingdom, and were leading
more and more to the view that there must be some spe-
cial peculiarity in the question of the constancy of organic
forms."

"But the idea of evolution in the vegetable kingdom was
brought more distinctly home to men's minds by paleon-
tological researches. Unger especially, while advancing
the knowledge of the structure of cells and of vegetable
anatomy and physiology and generally taking a prominent
part in the development of the new botany, applied the
results of its investigations to the examination of primeval
vegetation and showed the morphological and systematic
relations between past and existing floras. After twenty
years of preliminary study he declared distinctly in 1852
that the immutability of species is an illusion, that the new
species which have made their appearance in geological
periods are organically connected, the younger having
arisen from the elder. In the year that Darwin's book on
the origin of species appeared Nageli wrote : "External
reasons, supplied by the comparison of the floras of suc-
cessive geological periods, and internal reasons given in
physiological and morphological laws of development and
in the variability of the species leave scarcely a doubt that
species have proceeded one from another."

"Tho these words might not contain a theory of descent
capable at once of scientific application, yet they show that
the latest researches and candid appreciation of facts were
compelling the most eminent representatives of the botany
of the day to give up the constancy of forms. At the same
time in the genetic morphology which had developed itself
mainly under Nageli's guidance since 1844, and still more
in embryology, which in Hofmeister's hands was leading
to results of the greatest systematic importance, there lay
a fruitful element destined to correct and enrich Darwin's
doctrine of descent in one essential point. That doctrine

270 BOTANY

in its original form sought to show that selection, the
result of the struggle for existence, combined with per-
petual variation, was the sole cause of progressive improve-
ment in organic forms. But Nageli, relying on the results
of German morphology, was able as early as 1865 to point
out that this explanation was not satisfactory, because it
leaves unnoticed certain morphological relations, especially
between the large divisions of the vegetable kingdom,
which scarcely seem explainable by mere selection in
breeding.

"While Nageli allowed that Darwin's principle of selec-
tion was well adapted to explain fully the adaptation of
organisms to their environment and the suitableness and
physiological peculiarities of their structure, he pointed
out that in the nature of plants themselves there are inti-
mations of laws of variation which lead to a perfecting
of organic forms and to their progressive differentiation
independently of the struggle for existence and of natural
selection. The importance of this result of morphological
research has since been recognised by Darwin. Thus
Nageli supplied what was wanting in the theory of de-
scent and gave it the form in which it is adequate to ex-
plain the problem already recognised by the systematists of
the old persuasion — namely, how it is possible for the
morphological affinity of species in the system to be in so
high a degree independent of their physiological adapta-
tion to their environment. The modern teaching on vege-
table cells, modern anatomy and morphology and the im-
proved form of the theory of selection are the product of
inductive inquiry since 1840. It is one of the characteristic
features of this period of botany that morphology enters
into the closest connection with the doctrine of the cell,
with anatomy and embryology, and that researches, espe-
cially into the process of fecundation and the formation of
the embryo, form to some extent the central point of mor-
phological and systematic investigations.

At this time, when there was such necessity for general

DEVELOPMENT OF MORPHOLOGY 271

critical coordination and attack on the methods of the
day, Schleiden began his writing. In all his work were
to be found side by side with facts of real importance re-
flections of the man himself and generally coarse polemic,
coupled with a free praise or blame of other workers.

Schleiden's greatest contribution was his establishment
of the true nature of the cell and the propounding of what
may be called the cell doctrine of the structure of plants.
This was published in 1848, a year before the appearance
of a similar contribution by Schwann as regards animal
forms. Both of these investigations mark a new epoch in
the study of the structure of organic forms, and from that
time the researches into the inner morphology of plants
made rapid progress.

"Schleiden's mode of dealing with the natural system
must be reckoned among the good services which he
rendered to method; not because his classification
of the vegetable kingdom presents any specially in-
teresting features or brought to light any new affinities,
but because we see an attempt made for the first time to
give detailed characters drawn from morphology and the
history of development to the primary divisions, and be-
cause by this means the positive and distinct nature of the
Cryptogams was from the first clearly brought out. The
old way of treating morphology, as tho there were only
Phanerogams in the world, and then having recourse to
unmeaning negatives in dealing with the Cryptogams, was
thus set aside, much to the profit of the immediate future,
which directed its attention specially to the Cryptogams.

"Soon after Schleiden first stirred the scientific world a
man of a very different character of mind began to address
himself to the great task. This was Carl Nageli, whose
researches from this time onward laid the foundations of
knowledge in every department of botany. Like others,
he felt the necessity of first determining his position with
respect to the philosophical principles of the investigation
of nature, but he did not proceed to give a general exposi-

2J2 BOTANY

tion of the inductive method as opposed to the dogmatism
of the idealistic school. He went straight to the applica-
tion of the laws of induction to the most general problems
of organic nature and specially of vegetation.

"It is easy to say," remarks von Sachs, treating of his
work, "that the task of natural science is simply to deduce
conceptions and laws from the facts of experience by aid
of exact observation. Many considerations present them-
selves as soon as the attempt is made to satisfy this de-
mand, for it is not enough merely to accumulate individual
facts. The point to which the inductive inquiry is to lead
must be kept constantly and clearly before the mind.
Nageli insisted that it is only in this way that facts and
observations have any scientific value ; that the one impor-
tant thing is to make every single conception obtained by
induction find its place in the scheme of all the rest of our
knowledge. Since in nature everything is in movement,
and every phenomenon is transitory, presenting itself to
us in organic life especially as the history of development,
all due regard must be paid to this condition of constant
motility in forming scientific conceptions. The history of
development is not merely to be treated generally as one
of various means of investigation, but as identical with
investigation into organic nature."

"Nageli set himself in earnest to meet the demands of
inductive inquiry, such as he had himself described them.
Moreover, he connected his own morphological investiga-
tions, as fas as possible, with the lower Cryptogams, ex-
tending them afterward to the higher Cryptogams and to
the Phanerogams — that is, he proceeded from simple and
plain facts to the more difficult, thus not only introducing
the Cryptogams into the field of systematic investigation,
but making them its starting-point. In this way mor-
phology not only secured a foundation in exact historical
development, but it assumed a different aspect, inasmuch
as the morphological ideas hitherto drawn from the Phan-

DEVELOPMENT OF MORPHOLOGY 273

erogams were now examined by the light of the history
of development in the Cryptogams.

"This was one innovation; the second, closely connected
with it, was the way in which Nageli made the new doc-
trine of the cell the starting-point of morphology. Both
the first commencement of organs and their further growth
were carried back to the formation of the separate cells,
and the remarkable result was to show that in the Crypto-
gams especially, whose growth is intimately connected
with cell-division, precise conformity to law obtains in the
succession and direction of the dividing walls and that the
origin and further growth of every organ is effected by
cells of an absolutely fixed derivation. The most remark-
able thing was that every stem and branch, every leaf or
other organ has a single cell at its apex, and that all suc-
ceeding cells are formed by division of this one cell ac-
cording to fixed laws, so that the origin of all cell-tissue
can be traced back to an apical cell."

While important fragments as to their life-histories and
structures were described, they had little connected scien-
tific value, save perhaps the discovery that the fertilization
in certain Cryptogams as in animals was effected by sper-
matozoids. As to the flowering plants, the true function
of the pollen tube and of the development of the embryo
was not at all understood.

"This important question was set at rest by Wilhelm
Hofmeister. He showed that the egg-cell is formed
in the embryo-sac before fertilization, and that it is this
which is excited to further development by the ap-
pearance of the pollen-tube and produces the embryo.
Hofmeister had observed the organization of the ovule,
the nature of the embryo-sac and of the pollen-grain
and the formation of the embryo from the fertilized egg-
cell step by step and cell by cell, and his account of these
processes was aided by the light which Nageli's theory of
the cell and his reference of all processes of development
to the processes of cell-formation had thrown upon the

274 BOTANY

"history of development. He went on to apply the same
method to the study of the embryology of the Mosses and
the Vascular Cryptogams, and followed the development of
the sexual organs cell by cell in a large number of species.
The intimate connection between such different organisms
as the Liverworts, the Mosses, the Ferns, the Horse-tails,
the Club-mosses, the Conifers, the Monocotyledons and
Dicotyledons could now be surveyed in all its relations
with a distinctness never before attained. Alternation of
generations, lately shown to exist tho in quite different
forms in the animal kingdom, was proved to be the highest
law of development and to reign according to a simple
scheme throughout the whole long series of these ex-
tremely different plants. It appeared most clearly in the
Ferns and Mosses, tho at the same time with a certain dif-
ference in each; in the Ferns and allied Cryptogams a
small inconspicuous body grows out of the asexually pro-
duced spore and immediately produces the sexual organs.
From the fertilization of these organs proceeds the root-
bearing and leafy stem of the Fern, which in its turn again
produces only asexual spores. In the Mosses, on the
other hand, a much differentiated and usually long-lived
plant is developed from the spore, and this plant proceeds
again after some time to form sexual organs, the product
of which is the so-called Moss-plant. The first generation
that arose from the spore, the sexual, is in the Moss the
vegetative plant, while in the Ferns and their allies the
whole fulness of vital activity and of morphological differ-
entiation is unfolded in the second generation which is
asexually produced.

"Here all was at once clear and obvious, but Hofmeister's
researches also showed that the same scheme of develop-
ment holds good in the Rhizocarps and Selaginellae, where
two kinds of spores are formed; and it appeared plainly
from their case that the recognition of the true relation
between the production of spores and sexual organs is the
.guide to the morphological interpretation. When the

DEVELOPMENT OF MORPHOLOGY 275

processes in the large female spore of the most per-
fect of the Cryptogams was known, the formation of
the seeds in the Conifers was at once understood ; the
embryo-sac in these answered to this large spore, while the
endosperm represented the prothallium and the pollen-
grain the microspore. The last trace of alternation of
generations, so obvious in the Ferns and Mosses, was seen
in the formation of the seed in the Phanerogams. The
changes which the alternation of generations passes
through from the Mosses upward to the Phanerogams
were, if possible, still more surprising than the alternation
of generations itself.

"The reader of Hofmeister's 'Vergleichende Untersuch-
ungen' was presented with a picture of genetic affinity be-
tween Cryptogams and Phanerogams, which could not be.
reconciled with the then reigning belief in the constancy of
species. He was invited to recognise a connection of de-
velopment which made the most different things appear
to be closely united together, the simplest Moss with
Palms, Conifers and angiospermous trees and which was
incompatible with the theory of original types. The as-
sumption that every natural group represents an idea was.
here quite out of place. The notion entertained up to that
time of what was really meant by the natural system had
to be entirely altered ; it could as little pass for a body of
Platonic ideas as for a mere framework of conceptions.
But the effect of the work was great in respect to the
system also ; the Cryptogams were now the most important
objects in the study of morphology; the Mosses were the
standard by which the lower Cryptogams must be tried;
the Ferns were the measure for the Phanerogams.

"Embryology was the thread which guided the observer
through the labyrinth of comparative and genetic mor-
phology; metamorphosis now received its true meaning,
when every organ could be referred back to its parent-
form, the staminal and carpellary leaves of the Phanero-
gams, for example, to the spore-bearing leaves of the Vas-

276 BOTANY

cular Cryptogams. That which Haeckel, after the appear-
ance of Darwin's book, called the phylogenetic method,
Hofmeister had long before actually carried out, and with
magnificent success. When Darwin's theory was given to
the world eight years after Hofmeister's investigations,
the relations of affinity between the great divisions of the
vegetable kingdom were so well established and so patent
that the theory of descent had only to accept what genetic
morphology had actually brought to view.

"But the Algae, Fungi and Lichens presented a chaotic
mass of obscure forms in contrast with the well-ordered
knowledge of the Mosses and Vascular plants. There
was a difficulty in drawing the boundary-line between
the lower animals and plants. The difficulty was solved
by classing all objects capable of independent move-
ment with animals. Thus whole families of Algse were
claimed by the zoologists, and when the swarmspores of
a genuine Alga were seen for the first time in the act of
escaping, the phenomenon was described as the changing
•of the plant into an animal.

"Such was the condition of affairs with respect to the
Algae about the year 1850, when Hofmeister made the
formation of the embryo in the Phanerogams, the Vascular
Cryptogams and the Mosses the central point of investiga-
tion in morphology and systematic botany. He made it
clear that a perfect insight into the whole cycle of develop-
ment in the plant and into its affinities can only be ob-
tained in making its sexual propagation, the first com-
mencement of the embryo, the starting-point of the investi-
gation. It was natural to expect as happy results from the
embryology of the Algse as had been obtained in the case
of the higher plants. It was important, therefore, that the
observer should no longer rest satisfied with a knowledge
01 the sexual multiplication of the Algae. He must inquire
into their asexual propagation, and by its aid discover the
complete history of their development. Former observa-
tions suggested the probability that here too sexual propa-

DEVELOPMENT OF MORPHOLOGY 277

gation is the prevailing rule. A splendid result appeared
in 1853 in Thuret's account of the fertilization of the genus
Fucus; this was a simple process as a matter of embryol-
ogy, but the sexual act was so clear and even open to ex-
perimental treatment that it threw light at once upon other
cases more difficult to observe. Then followed discoveries
by different workers of sexual processes in rapid succes-
sion. Pringsheim, however, was not content with carefully
observing the sexual act. He gave detailed descriptions
of growth in the same families in its progress cell by cell,
of the formation of the sexual organs and the development
of the sexual product. The asexual propagations which
are intercalated into the vegetation and embryology were
shown in their true connection. Processes were recognised
which often recalled the alternation of generations in the
Muscinae ; it was shown that very different forms of sexu-
ality and of general development occur in the Algae, and
these led to the formation of systematic groups, quite dif-
ferent from those founded on the superficial observation of
collectors. From the confused mass of forms not before
understood Pringsheim brought out a series of character-
istic groups, which, thoroly examined and skilfully de-
scribed in words and by figures, stood out as islands in the
chaotic sea of still unexamined forms and threw light in
many ways on all around them. The Algse offer at present
a greater variety in the processes of development than any
other class of plants. Sexual and asexual propagation and
growth work one into the other in a way which opens en-
tirely new glimpses into the nature of the vegetable world.
"Some useful observations also had been accumulating
for some time on the Fungi. As early as 1729 P. A.
Micheli (1679-1737) had collected the spores of numerous
Fungi, had sown them and obtained not only mycelia but
also sporophores (fructifications). Yet Rudolphi and Link
at the beginning of the last century ventured to deny the
germination of the spores of Fungi. Persoon in 1818

278 BOTANY

thought that some Fungi grow from spores, others from
spontaneous generation.

The study of the lower fungi presented many difficulties,
but by the method of carefully working out complete life-
histories, or at least attempting to do so, progress was
being made. To the brothers Tulasne belongs the credit
of first breaking ground in this direction.

"But mycology owes its present form to none more
than to Anton de Bary. With a correct under-
standing of the only means which can lead to
sure results in this difficult branch of study, De Bary
made it his first endeavor to perfect the methods of ob-
servation, and not only sought for the stages of develop-
ment of the lower Fungi in their natural places of growth,
but cultivated them himself with all possible precautions,
and thus obtained complete and uninterrupted series of de-
velopments. By these means he succeeded in proving that
parasitic Fungi make their way into the inside of healthy
plants and animals, and that this is the explanation of the
remarkable fact that Fungi live in the apparently uninjured
tissue of other organisms, a fact which formerly had led
to the supposition that such Fungi owe their origin to
spontaneous generation or to the living contents of the cells
of their entertainers. Pringsheim had already observed
these occurrences in 1858 in the case of an unusually sim-
ple water-fungus (Pythium). De Bary showed that the
intrusive parasite vegetates inside the plant or animal
which is its host and afterward sends out its organs of
propagation into the open air, and that at a given time the
organism attacked by the fungus sickens or dies. These
investigations were not only of high scientific interest to
the biologist, but they produced a series of results of the
greatest importance to agriculture and forestry and even
to medicine.

"With the Fungi even more than with the Algae the chief
difficulty in making out a complete series of developments
in the history of each species arose from the frequent in-

DEVELOPMENT OF MORPHOLOGY 279

tercalation of the asexual mode of multiplication into the
course of its development and in the further peculiarity
that the several stages of development in some cases could
only be completed on different substrata. One of the most
important tasks was to find the sexual organs, the exist-
ence of which was rendered probable by various analogies,
and after De Bary had observed the sexual organs in the
Peronosporeae in 1861 he succeeded in 1863 in proving for
the first time that the whole fruit-body of an Ascomycete
is itself the product of a sexual act which takes place on
the threads of the mycelium.

"But the most important result remains to be told. It is
that the two classes of Algae and Fungi, hitherto kept
strictly separate, must obviously be now united and an en-
tirely new classification adopted in which Algae and Fungi
recur as forms differing only in habit in various divisions
founded on their morphology.

"A few words must be given here to the Lichens. They
are the division of the Thallophytes whose true nature
was last recognised, and that only in modern times. Till
after 1850 scarcely more was known of their organization
than Wallroth had discovered in 1825 — namely, that green
cells, known as gonidia, are scattered through the fungus-
like hyphal tissue of the thallus. After Mohl's investiga-
tions in 1833, it was known that free spores were formed
in the tubes of the fructifications (apothecia) and that a
dust collected from the thallus and consisting of a mixture
of gonidia and hyphae was in a condition to propagate the
species. The genetic relation between the chlorophyll-
containing gonidia and the fungus-like hyphae long con-
tinued to be obscure, till at last, after 1868, it was shown
that the gonidia are true Algae and the hyphal tissue a
genuine Fungus and that therefore the Lichens are not a
class coordinating with the Algae and Fungi, but a division
of Ascomycetes which have this peculiarity, that they spin
their threads round the plants on which they feed and
take them up into their tissue.

CHAPTER VI

ORGANOGENY AND ADAPTATION ( ECOLOGY)

Reference has already been made to the service which
Schleiden did in promulgating the idea of the cell as the
morphological unit of plant structure. As will be seen, he
was not, indeed, the first to observe them, tho he was the
first to properly understand their significance. Since the
cell is the ultimate unit to which morphological discussions
must necessarily hark back, it is well to examine a little
more closely just what these cells are.

"A thin cross-section from the stem or leaf of any plant
shows, when magnified, a network of cells not unlike those
of the honeycomb. This fact was first discovered in 1667
by Robert Hooke, an Englishman, wEo happened to take
such a section to test the improvements he was making on
the microscope. The first real study of cell structure was
made by Malpighi, an Italian, in the year 1671. The sec-
tion thus examined appears to be divided into small cham-
bers or cavities, separated from each other by a common
wall. The single cavity with its enclosing wall, like a
room in a house, received the name of cell. The origin
of these cells, or elements of plant structure, was at first
supposed to be similar to that of air bubbles in a somewhat
viscous liquid, but this supposition was soon found unten-
able, as in no young growing tissues was there found any
indication of the liquid in which the bubbles were sup-
posed to form.

"At a much later period it was discovered that the wall,
280

ORGANOGENY AND ADAPTATION 281

or membrane, which gave the name to the cavity which it
surrounds, was really the less important part and that the
cell contents were the only necessary element. This is
shown by the fact that the wall is a product of the con-
tents and that at certain periods of the plant's life the cell
may exist without it. Discoveries of this kind gave rise
to an entirely different conception of the nature of the
plant-cell. It is now known that this, in its simplest or
least differentiated condition, consists of a small portion
of the viscous liquid known as protoplasm, in which, under
ordinary magnification, no structures are visible. It is
in this general sense that Reinke defines a plant-cell as
follows : "An individualized, not farther divisible struc-
ture, consisting of or containing protoplasm which either
shows life processes or has shown them."

"In studying the anatomy of a plant-cell," says E. L.
Gregory in 'Elements of Plant Anatomy,' "it will be neces-
sary to consider one in its ordinary condition of develop-
ment— that is, as an element of any plant, differentiated
sufficiently to perform the ordinary functions of plant-
cells. Such cells are usually considered as consisting of
two parts, wall and centents, or as it is frequently stated,
wall and protoplasm, the latter including a nucleus and one
or more vacuoles. Before taking up the study of these
parts separately, it may be well to examine the cell as a
whole in reference to several features — namely, size, form,
mechanical and physiological principles, and finally to dis-
cuss briefly certain theories concerning organized struc-
tures in general. By far the greater number of plant-cells
are microscopic, but they vary greatly in size. The small-
est occur among the organisms known as bacteria. Some
of these are spherical in form and measure from seven-
tenths to one micro-millimeter (.001 millimeter) in
diameter.

"Cells vary as much in form as in size; those without a
membrane incline to the spherical shape, since the proto-
plasm composing them is in a half-liquid state. Many

282

BOTANY

swarm-spores are pear-shaped, but they generally assume
a spherical form on coming to rest. The forms of some
naked cells are subject to rapid change.

"In all the higher plants new cells are formed by the
growth of walls across the cavities of the old cells. The
new walls join the old at certain angles, and when the cells
are young they are inclined to a hexagonal form. As
growth continues the form is liable to change in various

Fig. 29 — Various Types of Cells.

ways. If the cell should grow equally fast in all parts it
would tend to retain its original form. This very rarely
happens, and even when it does, the shape of such a cell
is influenced in a greater or less degree by the manner
of growth of those surrounding it, as the growing wall is
flexible and its shape easily changed by pressure or trac-
tion from without.

"The individuality of the cell is shown by the fact that
each has its own predetermined manner of development.
All young cells of any plant are, at first, nearly similar in
form and size, but later on each cell is seen to follow cer-

ORGANOGENY AND ADAPTATION 283

tain laws of growth which are, to a certain extent, inde-
pendent of all external forces. From these laws, together
with various mechanical causes, arises the great variety of
form in the cells of ordinary plants. The peculiar forms
common to certain unicellular plants illustrate even better
than those of higher ones the inherent tendency of cells to
grow in a certain manner.

"From the small size of the average cell two advantages
result to the plant: First, strength and solidity; secondly,
the greatest possible amount of surface for the transfer of
cell contents. The first insures mechanical support; the
second is connected with those changes in the chemical
nature of the cell contents by which the life processes of
the plant as a whole are carried on."

Herbert Spencer included a consideration of plants in
his scheme of the "Principles of Biology." However some
of his deductions may be regarded at the present time, the
fact remains that he summed up in at least a convenient
form the ideas of morphological differentiation as in-
fluenced by the idea of Evolution. It is true that Spencer's
knowledge of plants was much of it second-hand, but his
treatment of the subject was a philosophical one and in
the main sound.

The problems of Morphology fall into two distinct
classes, answering respectively to the two leading aspects
of evolution. "Evolution," says Spencer in his 'Principles
of Biology,' "implies insensible modifications and gradual
transitions, which render definition difficult — which make
it impossible to separate absolutely the phases of organi-
zation from one another. Thus, on inquiring what is the
morphological unit, whether of plants or of animals, we
find that the facts refuse to be included in any rigid for-
mula. The doctrine that all organisms are built up of cells,
or that the cells are the elements out of which every tissue
is developed, is but approximately true. There are living
forms of which cellular structure cannot be asserted; and
in living forms that are for the most part cellular, there are

284 BOTANY

nevertheless certain portions which are not produced by
the metamorphosis of cells. Obviously, the earliest forms
must have been minute, since, in the absence of any but
diffused organic matter, no form but a minute one could
find nutriment. Obviously, too, it must have been struc-
tureless, since as differentiations are producible only by
the unlike actions of incident forces, there could have been
no differentiations before such forces had had time to
work. Hence distinctions of parts like those required to
constitute a cell were necessarily absent at first. And we
need not therefore be surprised to find, as we do find,
specks of protoplasm manifesting life and yet showing no
signs of organization.

"A further stage of evolution is reached when the im-
perfectly integrated molecules forming one of these minute
a?gregates become more coherent, at the same time as
they pass into a state of heterogeneity, gradually increas-
ing in its definiteness. That is to say, we may look for
the assumption by them of some distinctions of parts, such
as we find in cells and in what are called unicellular or-
ganisms. They cannot retain their primordial uniformity,
and while in a few cases they may depart from it but
slightly, they will, in the great majority of cases, acquire
a decided multiformity ; there will result the comparatively
integrated and comparatively differentiated Protophyta
and Protozoa. The production of minute aggregates of
physiological units being the first step, and the passage
of such minute aggregates into more consolidated and
more complex forms being the second step, it must natu-
rally happen that all higher organic types subsequently
arising by further integrations and differentiations will
everywhere bear the impress of this earliest phase of
evolution.

"From the law of heredity, considered as extending to
the entire succession of living things during the earth's
past history, it follows that since the formation of these
small, simple organisms must have preceded the forma-

ORGANOGENY AND ADAPTATION 285

tion of larger and more complex organisms, the larger
and more complex organisms must inherit their essential
characters. We may anticipate that the multiplication and
combination of these minute aggregates or cells will be
conspicuous in the early developmental stages of plants
and animals, and that throughout all subsequent stages
cell production and cell differentiation will be dominant
characteristics. The physiological units peculiar to each
higher species will, speaking generally, pass through this
form of aggregation on their way toward the final arrange-
ment they are to assume, because those primordial physio-
logical units from which they are remotely descended
aggregated into this form."

Goebel more recently, naming Spencer along with Hof-
meister and Sachs as one who has contributed in a special
degree to the science of organography, has proceeded along
somewhat similar lines, tho with a far wider knowledge of
the actual facts. In discussing the question of the elabora-
tion of the plant body, his introductory statements are
illuminating.

"It is manifest," he says, "that the distinction of organs
must have originally been based upon differences of outer
form. The word 'blade' indicates that the original concep-
tion of a leaf was that of a flat organ which was distin-
guished by this character from the usually cylindric stem ;
under the designation root all subterranean organs were
reckoned. It is, however, now generally known that there
are leaves which have all the appearance of shoots, and
the converse is also the case.

"External form is closely connected with function and
with anatomical structure. In the vegetative organs the
form may change, accompanied by a change in anatomical
structure; 'metamorphosis' may take place, and a flower-
leaf is the homologue of a foliage-leaf, notwithstanding
that it has quite a different form.

"The history of development of the stem of the leaf is
usually different. In the first place the duration of devel-

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BOTANY

opment is unlike; leaves have limited growth, shoots have
unlimited growth. But there are many shoots which nor-
mally exhibit limited growth; for example, the short
shoots, or spur-shoots, of many conifers and broad-leaved

Fig. 30 — Diagram of Tip of Stem in Longitudinal Section.
a., formative region ; lb., leaves and branches in various stages

of development ; v., vascular bundles ; c, cortex ; p., pith.

(Curtis.)

trees. These, however, may under certain conditions be-
come shoots of unlimited growth and be transformed into
long shoots.

"A striking illustration is furnished by species of the
genus Utricularia, which are among the most remarkable

ORGANOGENY AND ADAPTATION 287

plants in the world. In this genus the floating 'shoots' of
the water-form, as well as the creeping 'stolons' of the
land-form, are homologous with leaves, but the difference
between stem and leaf has entirely disappeared. The or-
gans which are homologous with leaves produce flowers
and other shoots and exhibit unlimited growth, and that
they are really leaves with prolonged apical growth is only
to be determined by a careful comparative study. Every
distinction then that we may draw between shoot and leaf
is only relative, is not fundamental.

"There is, however, this point still to notice : Leaves are
in most cases outgrowths of shoot-axes and they arise on
their vegetative point as lateral members ; nevertheless
terminal leaf-organs — organs arising from the end of a
shoot-axis — are known. They occur in the flowers of
many plants ; the cotyledon in many monocotyledonous
plants is terminal in the embryo. There are also mono-
cotyledonous embryos upon which leaves arise, altho no
vegetative point of the axis is visible, and a similar condi-
tion is also found in Isoetes. Further, the vegetative body
of Lemna is nothing else than a leaf producing leaves ; it
is not a leafless twig, as is commonly assumed.

"A plant-body in which the shoot-axis does not exhibit
differentiation into stem and leaf is termed a thallus. The
expression thallus, which signifies nothing more than
shoot, was first used by Acharius in describing the lichens,
and subsequently it was extended to the Algae, the Fungi
and the thallose liverworts. There is no sharp limitation
between a thallus and a leafy shoot.

"The external relationships of configuration of the bodies
of plants are determined by the peculariarities of their liv-
ing substance, the protoplasm, which in the higher plants
is enclosed within the numerous cells which compose the
plant; it is only among the lower plants that we find uni-
cellular bodies. In land-plants the cellular structure is
general and the several cell-chambers are separated from
one another by firm walls."

288 BOTANY

Here Goebel speaks of Sachs' definition of the energid
as the unit of cell structure, quoting Sachs, who says:
"By an energid I mean a single nucleus with the proto-
plasm which it dominates." Thus he distinguishes the
monergic type of plant, which is unicellular and has but a
single nucleus — i.e., is a single energid — and the polyergic
forms which have many energids that are usually separated
into individual cells by cell walls, tho in some of the lower
forms they may not be.

"It has been possible," he continues, "in a large number
of cases to discover a relationship between their forms and
their life-functions. We see this, for example, among
diatoms. The monergic cells of fixed species have a differ-
ent construction from that which obtains in the actively
moving or floating species. It is also clear that the pear-
like form of most swarm-spores is especially favorable for
their movements. In other cases, however, we know so
little regarding the special life-relationships of the plants
that we are quite unable to speak with certainty. We can-
not, for example, say whether the rod-like or sickle-like
desmids have relationships of a kind different from those
of the plate-forms.

"The degree in which the single energids are united with
one another may be more or less intimate. A polyergic
plant is either an energid colony or ccenobium (cellular or
non-cellular), in which a division of labor between the
several energids has not yet appeared and each energid is
capable of living for itself, or the energids exhibit a divi-
sion of labor, and, altho in unison with one another, are
therein different from one another; they form an energid
dominion. This is what has come to pass in the majority
of the polyergic plants. There are, of course, many transi-
tions between these two conditions, and their separation is
in a measure artificial, being based upon extreme relation-
ships.

"In the higher plants the shoot is differentiated into
sfeoot-*xis and leaf in all cases except in some degenerate

ORGANOGENY AND ADAPTATION 289

parasites. There are, it is true, leafless shoots of limited
growth, but these are quite exceptions. In the lower forms
of plant-life such a differentiation of the shoot may also
take place. The sexual generation of many liverworts and
of the whole of the mosses shows an evident division into
shoot-axis and leaf, and, as has been above explained, this
condition is reached among the liverworts in the most
different cycles of affinity, which have developed quite inde-
pendently one of the other. That the leaves of the sexual
generation of mosses are not homologous with those of the
asexual generation of the Pteridophyta is sufficiently clear,
but terminology is only a means to an end, and I have no
hesitation in calling the leaf-like organs which we find in
many Thallophyta 'leaves.' "

The development of morphology, both as it applies to
cell and tissue structure alone and as it applies to the study
of life-histories, has made rapid advances in the last few
decades. There have been and are numerous keen investi-
gators covering all morphological fields. The present
knowledge of the structure of the individual cell has
greatly increased, and the store of information regarding
the embryology of the higher plants, tho founded on the
classic work of Hofmeister, is well-nigh a new science.
The study of life-histories in as complete a way as possible
is now the aim of morphological investigators.

"The morphologist," says H. M. Richards, "who de-
votes his time to the study of life-histories is engaged in
the work of tracing the race history of plants from the
comparison of the individual development of more or less
nearly related forms. Thus the homologies which have
been traced among the flowering plants and their nearest
allies among the ferns and other forms indicate to us
the probable race history of these groups. It is true that
the beginning of this work dates back some decades, but
it is still, to a large extent, an open field, and numerous
investigators are actively prosecuting research along these
lines. For example, the alternation of a sexual and non-

290 BOTANY

sexual generation of plants which has long been known
as characteristic of the life-histories of higher forms has
recently been established among the lower groups, and
thus a much clearer view of the whole series of the plant
kingdom is being obtained."

The branch of botanical research known as ecology is
one of the most inclusive. It may be regarded as an at-
tempt to grasp the full meaning of the morphological and
physiological manifestations of the living plant not only as
they concern itself, but also in their relation to all factors
of its environment, whether with other organisms or with
purely physical agents. It is evident that the problem is a
stupendous one, and in the present state of knowledge
"both of physiology and morphology it cannot be expected
that necessarily permanent results are to be obtained.
Nevertheless it serves a highly important end in calling
attention to and insisting upon the fact that environmental
factors must influence the individual; that no organism,
even a plant, is a free agent in determining its career or
the career of its progeny.

Ecology is the application in a broad and more philo-
sophical way of the methods of the physiological anatomist
coupled with those of the taxonomist; but, in addition, the
work of the botanist touches the field of the physiographer
and geologist. "Ecology," says H. M. Richards in his
'Botany,' "is the endeavor to uncover the plan of nature as
it governs the relations of the different plant forms in a
given area, to understand the why and the wherefore of
the association of very different forms in one locality.
The keynote of the philosophical development of this topic
rests on the conception of the constant struggle of indi-
viduals or groups of individuals to maintain themselves
against other forms, which leads to a balanced relation of
the different species in a given flora."

From the beginning one of the greatest of ecological
problems has been that of the origin and significance of

ORGANOGENY AND ADAPTATION 291

adaptations. "In other days/' remarks Henry C. Cowles
in his 'Trend of Ecological Philosophy/ "the solution was
sought in special creation, one of the most unscientific of
all theories, because altogether subversive of experiment.
The entire question was prejudged at the outset. The
theory of special creation, however, has not been especially
harmful, because it has generally seemed so unlikely as to
have received but little support among scientific men. Per-
haps the most baneful of all ecological theories has been
the Lamarckian theory of direct adaptation.

"The theory of natural selection has worked great harm
in the ecological study of plant structures. Thorny plants
have been supposed to be selected by reason of animal in-
cursion, and such complex things as floral structures have
been supposed to be the result of parallel selection on the
part of flowers and insects. There is no adequate evidence,
experimental or otherwise, for views of this character.
Such experimental work as has been done appears to show
that the success or failure of a plant rarely depends upon
this or that little advantage, upon which natural selection
may be supposed to work, but rather that its perpetuation
depends for the most part upon other things than its so-
called adaptations.

"Few more perfect adaptations for their function can be
thought of than the digestive glands of insectivorous
plants, and yet there is no evidence in support of the idea
that such plants have been able to survive by reason of
these glands. The evolution of such a complex flower as
that of the orchid along lines that are parallel with the
evolution of the mouth parts of a special insect requires a
nicety of operation that seems staggering, and all the more
because the flower, at least, seems to have evolved so far
along the lines of zygomorphy as to be a source of disad-
vantage rather than of advantage, an impossible idea to
the natural selectionist.

"The facts of regeneration show that plants and animals
are often in a position to make an instant new reaction to

292 BOTANY

conditions unlike those to which they have ever been ac-
customed and that these reactions may or may not be ad-
vantageous. In any case, natural selection can have no
possible connection with their origin. The trend of the
time, especially among botanists, is unmistakably toward
the abandonment of natural selection as a theory of evolu-
tion, but ecological work is finding a dominant place for it
as one of the controlling factors in succession. The stu-
dent of vegetation dynamics, more perhaps than any other,
finds displayed before him an incessant struggle for exist-
ence ; in the changing conditions the fitness of an old spe-
cies to remain or of a new species to displace it is com-
monly a matter of profound importance in the vegetative
change produced.

"To the working ecologist the necessary consequences of
the abandonment of the idea of adaptation and of natural
selection as a causative factor are most vital. First and
foremost there comes the possibility of disadvantageous
trends in evolution. To some extent such tendencies will
be checked by the destructive operation of natural selec-
tion, so that only such new species as are most fit are likely
to survive and have progeny. But in view of the ideas
that have generally prevailed in past years, it cannot be
emphasized too strongly that plants may retain useless
structures and even structures that are moderately harm-
ful and yet live on if they also possess other structures or
habits that are sufficiently advantageous. This conception
at once relieves ecologists of one of the most arduous of
their former duties, the establishment of an advantageous
function for every organ and of a benefit in every func-
tion."

CHAPTER VII

PHYSIOLOGY OF PLANTS

"Every living organism has the power of producing off-
spring which inherit the characteristics of the parent
stock/' says Pfeffer in his 'Physiology of Plants/ "The
fact that the acorn always produces an oak, a
fungus spore the same specific fungus, is sufficient
proof that it is the inherent properties of the living
substance of the embryonic organism which primarily
determine the shape, character and indivdual peculiarities
of the adult organism. In the young plant the full de-
velopment of such characters takes place only through
interaction with the external world, and not unless
certain necessary conditions are fulfilled. Thus, if the
plant is deprived of nourishment it finally dies of hunger,
while vital activity and growth are only possible in the
presence of water and within certain limits of tempera-
ture. It is evident that the absence of any one of the
necessary conditions must invalidate the remaining ones,
so that if the amount of water is insufficient, or if the
temperature sinks too low, the vital activity of the or-
ganism is depressed or completely arrested, and similarly
at a high temperature death ultimately supervenes. Hence
Physiology is primarily required to determine the powers
and possibilities of individual organs and cells and their
various interactions.

"The manifestations of life when traced back to their
ultimate origin are always found to originate in the proto-
293

294 BOTANY

plasm, an undifferentiated mass of which constitutes the
substance of the simplest living elementary organism.
Hence one of the tasks of Physiology is to throw light on
the manner in which the inherent nature of the proto-
plasm is responsible for the chemical and physical changes
to which it gives rise. It is as impossible to picture a regu-
lar continuance of life otherwise than by the cooperation
of different organs and biological elements as it is to
imagine a watch which could still keep time after the
removal of certain of the wheels.

"The chemical nature of the living organism, with its
indissolubly connected chemical and mechanical proper-
ties, is of much greater importance than that of a ma-
chine; for in the changes which take place in the self-
regulating protoplasmic mechanism chemical nature and
affinities are, in all cases, of fundamental importance.
Hence progress in Physiology necessarily goes hand in
hand with progress in Chemistry. From a physiological
standpoint it is hardly possible, for example, to over-
estimate the importance of a complete knowledge of the
chemical constitution of the proteids, which take so promi-
nent a part in building up the living protoplast, especially
in view of the possibility that each particular species may
be characterized by a specific variety of living proteid.

"There is no reason for regarding life as the product
of an extraordinary and mystical natural force; it is to
be treated simply as a special and peculiar manifestation
of energy. Moreover, since we can only guess at the
evolutionary history of the organism, it is only possible
for us to deal with the physiological and other properties
which it now possesses, and however clearly we may be
able to explain the peculiarities of a given plant as being
due to characters and tendencies inherited from its pa-
rents, we shall still be unable to determine with certainty
the evolutionary origin of that particular species.

"The production and hereditary transmission of vari-
ations are connected in many ways with the general

PHYSIOLOGY OF PLANTS 295

physiological problems with which we are immediately
concerned. When any variation takes place an alterna-
tion in the structure or nature of the protoplast must
have previously occurred, provided the variation is not
merely a temporarily induced one, but is one capable of
hereditary transmission to the offspring. This is true
for the lowest as well as the highest plants, and whether
the variation is perpetuated by sexual asexual repro-
duction. The conclusion that a change of this kind neces-
sarily indicates an alteration in the arrangement or char-
acter of the protoplasmic constellation is, indeed, a logical
necessity, even tho it is impossible to determine exactly
how the given variation arises or is induced.

"The reproduction of hybrid forms is evidently due to
the combination of two different kinds of living sub-
stance. There can be no doubt that if it were possible to
interchange the nuclei of two separate and distinct proto-
plasts, assuming that the strange nuclei and protoplasts
could live and grow together, two new organisms would
be produced differing from one another and from the
original protoplasts. These special characteristics of the
new organisms would be preserved so long as the union
and cooperation between the parts of the new protoplasts
were maintained. This would also be the case if, for
example, a bacterium existed in intimate and permanent
symbiotic union with the protoplast, as a chloroplastid
does, and were transmitted from generation to generation
in the ovules.

"It is, as a matter of fact, not inconceivable that the
existence of certain species, as such, depends upon pro-
toplastic or symbiotic unions of similar character to the
above. Nor is the possibility excluded that the tiny sym-
biont might be too small to be visible, or might be unable
to continue an independent existence outside of the pro-
toplast. Comparatively recently lichens were regarded
as distinct organisms, altho we now know that they are
the products of a synthetic union of two distinct plants,

296 BOTANY

and that by the artificial synthesis of various algae and
fungi new forms, or forms similar to those already known,
may be produced with relative ease.

"Nevertheless, as is well known, variation capable of
hereditary transmission may arise without the help of
foreign protoplasm, and certain bacteria afford especially
instructive examples of these. Thus in many bacteria the
power of forming either spores or certain metabolic prod-
ucts may be inhibited by a particular mode of treatment,
and in some cases this inhibition is permanent, so that
even under normal cultural conditions a reversal never
takes place. The variety thus produced will hence remain
constant in a neutral environment, altho there always re-
mains the possibility that by the action of other agencies
a return to the original condition may be induced. Acci-
dental reversions are, as is well known, by no means un-
common in the higher plants.

"Saltatory variations often do appear in organisms, and
may arise under precisely similar external conditions in
particular individuals only, or may even affect these in
different manner or degree. It has previously been stated
that Physiology must necessarily seek an explanation of all
vital processes in the developmental and formative powers
of the protoplast. Our knowledge on this point is still in
its infancy, and we must be content if we can gain here and
there a glimpse into the internal protoplasmic mechanism.
Even tho our knowledge with regard to the structure of
protoplasm were to be enormously increased we should still
see, not the causes and forces which are acting, but only
the results which they produce. The most perfect men-
tal picture of the plant or of the protoplast must neces-
sarily fail to reveal the hidden and invisible causes which
make it assume its specific form.

"Above all, it must be remembered that the simplest
protoplast is an organism of very complex structure, and
that its various activities result from the interactions of
its component parts and organs. The particular result

PHYSIOLOGY OF PLANTS 297

which any given cause produces is due to the special
nature of the given protoplast. Every plant must there-
fore necessarily have certain special protoplasmic char-
acteristics which are peculiar to it alone. At the same
time, protoplasts of similar origin may temporarily or per-
manently acquire special properties by a progressive dif-
ferentiation of labor and by adaptation to special aims
and purposes. Nevertheless, the plant protoplast, so long
as it remains living, retains all the general features which
characterize a typical vegetable cell.

"In order to attain certain ends the organism forms
parts which are not living or capable of life. One such
organ is the cell-wall which the protoplast constructs as
a protective mantle in which it may live and work ; indeed,
the protoplast living inside its cell-wall may be compared
to a snail in its shell. In certain cases the protoplasmic
contents may escape from the cellulose investment as a
naked swarmspore, which later may build for itself a new
domicile.

"In the protoplast, just as in a snail, the internal struc-
ture and functional importance of the component parts
require to be studied. Within the protoplast are spaces
having considerable functional value, which are surround-
ed by living substance, but whose contents are not living.
Such are the vacuoles, which subserve a variety of func-
tions. They may serve for the storage of reserve food
material, while the dissolved substances which they con-
tain give rise to the osmotic properties of the cell and
preserve these properties during growth. As the vacuoles
increase in size the cell becomes much larger, but the
amount of protoplasm which it contains undergoes no
increase, or but little, so that finally it is reduced to a
thin primordial utricle or bag, closely adpressed to the
cell-wall, and containing a single large central vacuole.
Vacuoles are laboratories in which food may often be
digested or building material prepared for use, while at
the same time they are utilized in translocation.

298 BOTANY

"The body of the protoplast, the protoplasm as we
may call it, is built up of organs and elemental structures.
The nucleus is an organ of very general importance, and,
indeed, a separation into nucleoplasm (karyoplasm) and
cytoplasm probably occurs in all protoplasts. On the
other hand, chromatophores, including chlorophyll cor-
puscles, are organs of special character and are absent
from fungi. When such special organs are present they
may be given the general name of plastids.

"Like all living substance, the plasmatic organs are of
considerable complexity. This is readily . perceptible in
the resting nucleus, and is admirably shown when the
latter divides; while the chromatin fibers, which are then
so markedly visible, may also be seen to have a definite
structure of their own. Besides the plastids already men-
tioned, the cytoplasm may contain minute bodies, often
in great numbers, which, regardless of their morphologi-
cal and physiological nature, may be termed microsomes
or microsomata. They may be composed in some cases
of non-living substance, but in other cases may be minute
living plastids.

"In a small cell, or one of the organs of such a cell, the
component units must necessarily be still smaller, and yet
have positive dimensions; while the smaller and more
numerous these units are the more varied and complicated
will the possible combinations be. At the same time a
relatively greater surface area is correlated with the
smaller size, and this is a factor of the utmost importance;
for bacteria teach us what remarkable powers are con-
ferred by extreme minuteness and what extraordinary
processes it renders such organisms capable of perform-
ing.

"The various operations which are continually going on
in the body of the plant involve the execution of a consid-
erable amount of work. This is very evident in the enor-
mous development of a large tree from the relatively small
seed. Such a process of construction has involved the

PHYSIOLOGY OF PLANTS 299

preparation of a vast quantity of highly complex mate-
rial from very simple chemical substances. The processes
incident to life also, tho they may not lead directly to
the formation of such substances, cannot be conducted
without involving a considerable amount of work, whether
the plant is a minute body consisting of a single protoplast,
or an organism of a much higher degree of complexity."

"If we turn now to consider the sources of the plant's
energy," continues J. Reynolds Green in his 'Introduction
to Vegetable Physiology, "it is evident that they must be
in the first instance of external origin. . . . The radiant en-
ergy of the sun, indeed, is the only possible source which
can supply it to normal green plants. The rays which
emanate from the sun are generally alluded to as falling
into three categories: those of the visible spectrum, those
of the infra-red, and those of the ultra-violet. The sec-
ond of these are frequently spoken of as heat rays and
the last as chemical.

"The greatest absorption of energy appears to take
place in consequence of the peculiarities of chlorophyll.
This substance, whether in the plant or when in solution
in various media, absorbs a large number of rays in the
red and in the blue and violet regions of the spectrum, to-
gether with a few others in the yellow and the green. The
solar spectrum, after the light has passed through a solu-
tion of chlorophyll, is seen to be robbed of rays in these
regions, and hence to present the appearance of a band
of the different colors crossed by several dark bands.
The greater part of the energy so obtained in the cells
which contain the chloroplasts is at once expended, partly
in constructing carbohydrate food materials and partly
in evaporating the water of transpiration, the latter proc-
ess being much the more expensive."

Speaking of these carbohydrate food materials, H. M.
Richards says: "It is evident that the starch, which is
the first substance that we readily recognise, is not the
first substance which is formed. Modern research points

300

BOTANY

more and more to the conclusion that it is the simplest
of carbohydrates that is produced, a substance known as
formaldehyde. But what is especially interesting is that
it seems not impossible that this primal reaction may not,
after all, be a function of the living protoplasm, but a
chemical reaction that can be carried on outside the cell
through the agency of chlorophyll It is in the further
elaboration of this first substance formed that the living
protoplasm is apparently necessary. At any rate, we
know that the energy demanded for the process must be

Fig. 31 — Absorption Spectrum of an Alcoholic Solution of

Chlorophyll Extracted from Foliage Leaves.
The broad black on the left indicates in what portion of the

spectrum — namely, the red-orange — the greatest absorption

takes place.

afforded by the particular rays of sunlight which the
chlorophyll absorbs."

"There is plenty of evidence," continues Green, "of the
power of plants to avail themselves of the heat rays. Not
only can the air rob the plant of heat by radiation, but
when its own temperature is high it can communicate heat
to it in turn. Indeed, its absorption by the leaves would be
a source of considerable danger to the plant were it not for
the cooling effect of transpiration, which dissipates 98 per
cent, of it during bright sunshine. No doubt this dis-
sipation is one of the chief benefits secured by transpira-
tion.

"It is evident, however, that in the general economy
of the plant something further must be at work in con-
nection with the supply of energy. The absorption of
these external forms must take place at the exterior of the

PHYSIOLOGY OF PLANTS

301

plant, while many the processes of expenditure are carried
out in parts which are more or less deep-seated. We are
obliged to turn our attention, therefore, in this connection
as in that of the construction and utilization of food, to
processes of accumulation, distribution and economy.

$3 . * /PL

Qxgp

Fig. 32 — Forms of Starch Grains.
1., from corn-cockle; 2., from wheat; 3., from spurge; 4., from
bean; 5., from Indian corn; 6., from canna ; 7., from potato;
8., from potato (highly magnified); 9., from oats; 10., com-
pound grain from seed of a grass; 11., from meadow saffron;
12., from rice; 13., from millet. (Kerner.)

"What is the immediate fate of the energy absorbed?
It enters the plant in what is known as the kinetic form.
A very considerable part of the kinetic energy of the sun's
rays, we have already seen, is devoted at once to the
evaporation of the water of transpiration, but some of it
is employed by the chloroplasts to construct some form of

302 BOTANY

carbohydrate. The energy so applied can be again set
free by the decomposition of this formed material. If the
latter were burned its combustion would be attended by the
evolution of a certain definite amount of heat. This heat
would represent the energy that had been applied to
the construction of the material so burned. Any ac-
cumulation of material in the body of the plant pep-
resents, therefore, not only a gain of weight or sub-
stance, but a storage of energy. This has disappeared
from observation during the constructive processes, but
can be liberated again during their decomposition and
applied to other purposes. Energy which has thus been
accumulated and stored is known as potential energy,
to distinguish it from the actual or kinetic energy origi-
nally absorbed. The formation of material in the plant,
therefore, involves a storage of energy in the potential
form, and wherever such material is found there is in
it an amount of energy which can be liberated with a
view to utilization at any point to which the material
has been transferred.

"The protoplasm itself contains a store of such poten-
tial energy. It can only be constructed at the expense
of food supplied to it. The formation of the protoplasm
which follows the supply of food to the cell involves
work, and the energy so used is partly changed from the
kinetic to the potential condition. When the protoplasm
undergoes what we have called its self-decomposition,
which is continually taking place, a certain amount of
this potential energy is liberated and can be observed
and measured in various ways. When destructive metabo-
lism is active there is usually a rise of temperature, as
in the processes of the germination of seeds. A certain
amount of the liberated potential energy in this case mani-
fests itself in the form of heat. A vegetable cell which
obtains no direct radiant energy from without can, con-
sequently, obtain the energy it needs from within itself
by setting up decomposition, either of its own substance

PHYSIOLOGY OF PLANTS 303

or of certain materials which have been accumulated
within it.

"The transformation of potential into kinetic energy-
is associated with decomposition just as the converse
process is bound up with construction. Destructive metab-
olism in the cell is then the means by which its energy
is made available. The processes of this katabolism go
on in the interior of each cell. Each liberates at least
as much energy as it requires for the maintenance of its
life and the discharge of its particular functions. The
processes associated with the utilization of the stored
energy are, then, chemical decompositions in which vari-
ous constituents of the cell are involved. These* are of
two kinds, in the first of which the protoplasm itself takes
part, and which comprize the processes in which its own
breaking down takes place; in the second it effects the
splitting up of other bodies without a necessary disruption
of its own molecules.

"Respiration is to be looked upon as a process very
largely connected with the utilization of the store of en-
ergy which each cell possesses, and perhaps primarily
to be concerned in the transformation of that energy
from the potential to the kinetic form. The oxygen ap-
pears to be necessary mainly for the purpose of exciting
those decompositions of the protoplasm which are so
dependent upon its instability."

CHAPTER VIII

GROWTH AND VARIATION

"In studying the growth of plants," says Reynolds
Green, "the relation which it bears to the processes of
metabolism must be borne in mind. The constructive pro-
cesses are much greater than those which lead to the disap-
pearance of material from the plant-body. The result of
this is that there is a conspicuous increase in the substance
of the plant as well as an accumulation of potential energy
which can be made use of by the plant through various de-
compositions which its protoplasm can set up. The great
permanent accumulation of material is what we associate
with the processes of growth. Mere increase in weight
in an organ does not, on the other hand, necessarily imply
any growth.

"Growth," he continues, "is in the strict sense always
associated with the formation of new living substance,
and is very generally accompanied or immediately fol-
lowed by additions to the framework of the growing
cells or organs. It is in nearly all cases attended by a
permanent change of form. This is perhaps not so evi-
dent in the case of axial organs as it is in that of leaves
and their modifications, tho even in them it can be de-
tected to a certain extent. It is much more conspicuous
in the case of leaves, for the latter, as they expand from
the bud, have usually a different shape from that of the
adult ones, and the assumption of the mature form is a
gradual process, taking place as the age of the leaf in-
304

Giant Bamboo (compare size of man at foot).

GROWTH AND VARIATION 305

creases. Growth may, in the light of the considerations
just advanced, be denned as permanent increase of bulk,
attended by permanent change of form.

"Growth in the lowliest plants may be coextensive with
the plant-body. In all plants of any considerable size,
however, it is localized in particular regions, and in them
it is associated with the formation of new protoplasts,
In the sporophytes of all the higher plants there exist
certain regions in which the cells are merismatic; that is,
which have the power of cell multiplication by means of
division. In such regions, when a cell has reached a cer-
tain size, which varies with the individual, it divides into
two, each of which increases to the original dimensions
and then divides again. As these growing regions con-
sist of cells, the growth of the entire organ or plant will
depend on the behavior of the cells or protoplasts of which
its merismatic tissues are composed.

"The growth of such a cell will be found to depend
mainly upon five conditions: (1) There must be a sup-
ply of nutritive or plastic materials, at the expense of
which the increase of its protoplasm can take place, and
which supply the needed potential energy. (2) There
must be a supply of water to such an extent as to set up
a certain hydrostatic pressure in the cell. (3) The sup-
ply of water must be associated with the formation of
osmotic substances in the cell or it cannot be made to
enter it. In the absence of the turgescence which will
be the result of the last two conditions no growth is pos-
sible, for reasons that will presently appear. (4) The
cell must have a certain temperature, for the activity of
a protoplast is only possible within particular limits, which
differ in the cases of different plants. (5) There must be
a supply of oxygen to the growing cell, for, as we have
seen, the protoplast is dependent upon this gas for the
performance of its vital functions, and particularly for
the liberation of the energy which is demanded in the
constructive processes. This is evident also from the

3o6

BOTANY

consideration that the growth of the cells is attended by
the growth in surface of the cell-wall; and as the latter
is a secretion from the protoplasm — a product, that is, of
its katabolic activity — such a decomposition cannot read-
ily take place unless oxygen is admitted to it.

"Growth, so far as it implies only the formation of
living substance, is thus a constructive process. It is,

■Apparatus for Measuring Growth. (Giesenhagen.)

however, intimately associated with destructive metabolism
or katabolism, the latter being involved in the construc-
tion of the increased bulk of the framework of the cell
or cells, and being essential to supply the energy needed
for the constructive processes.

"The process of the growth of a cell is limited in its
extent, tho the limits vary widely in different cases. In
some, cells grow only to a few times their original dimen-

GROWTH AND VARIATION 307

sions; in others they may attain a very considerable size-
In any case, however, we can notice that the rate of
growth varies regularly throughout the process ; it begins
slowly, increases to a maximum, and then becomes gradu-
ally slower till it stops. The time during which these
regular changes in the rate can be observed is generally
spoken of as the grand period of growth."

Closely connected with the metabolic activities of the
plant in the release of energy for life processes is the
phenomenon of digestion. In the simplest conception di-
gestion means merely the rendering soluble and assimilable
of insoluble food substances; but the active agents of
digestion — the enzymes — may, and in all likelihood do,
have a far more intimate connection with the life of the
cell than the mere preparation for absorption of food
exterior to the actual living substance.

"The process of digestion in plants," continues Green,
"is chiefly intracellular, and takes place in all cells in
which reserve materials occur. It is only occasionally
that it is found taking place on the exterior of the plant ;:
that is, not in the interior of a cell. In a few cases it is.
carried on in connection with the absorption of nitrogen-
ous or protein food, as has been already shown. Diges-
tion, tho most generally associated in plants with the
utilization of reserve materials, may thus occasionally be
met with in connection with the absorption of food from
without, when it is a process precisely similar to the di-
gestive processes of the higher animals, tho it is some-
what simpler in the details of its mechanism. The intra-
cellular digestion of plants agrees very closely with that
of many of the humbler animals, and corresponds also
with such processes in the higher forms as the utiliza-
tion of the glycogen of the liver and the fat of various
regions.

"Absorption of food from without, after preliminary di-
gestion, is much more frequently observed when we study
the nutritive processes of the Fungi. Not only protein,.

308

BOTANY

but also carbohydrate and fatty substances are thus di-
gested outside the body of the plant, and the products
of the digestion are subsequently absorbed.

Fig. 34 — Plants of Buckwheat Cultivated in Various Nutri-
tive Solutions.
i., normal solution containing all necessary salts; 2., solution with

potassium compounds omitted ; 3., with sodium salts omitted ;

5., with nitrogen compounds omitted.

"The protoplasm of the cell, among its many properties,
no doubt has the power of setting up these decomposi-
tions, and probably in many of the very lowly plants, in
which the whole organism consists of only a few proto-

GROWTH AND VARIATION 309

plasts or perhaps a single one, the work is altogether
effected by its instrumentality. The protoplast, in fact,
carries out all the various processes of life by the interac-
tions of its own living substance with the materials ab-
sorbed by it, aided in the constructive processes by the
chlorophyll apparatus, if it possesses one. In such a pro-
toplast we may observe at times the storage of such a
reserve material as starch, and its digestion at the appro-
priate period.

"Even in more complex plants it is certain that the
living substance of every protoplast is in a constant state
of change, initiating many decompositions in which its
own substance takes part, as well as others into the course
of which it does not itself enter. Among these decom-
positions we must include the various intracellular digest-
ive processes. Tho all protoplasm has this power, it is
not usual in plants, any more than in animals, to find it
exclusively relying on it. The work of digestion, at any
rate, is generally carried out by peculiar substances which
it forms or secretes for the purpose. We have in plants
a large number of these secretions, which are known as
enzymes, or soluble ferments.

"The action of these enzymes is not at all completely
understood. They appear not to enter into the composi-
tion of the substances which are formed by their activity,
and they seem to be capable of carrying out an almost
indefinite amount of such work without being used up
in the process. They are inactive at very low tempera-
tures, but effect the decompositions they set up freely
at the ordinary temperature of the plant. As the tem-
perature at which they are working is raised their activ-
ity increases up to a certain point, which varies slightly
for each enzyme, and is called its optimum point. This
usually ranges between 300 and 45 ° C. If the tempera-
ture is raised above the optimum point the enzyme be-
comes less and less active as it rises, and at about 60-70 ^

310 BOTANY

C. it is destroyed. The exact point, however, varies a
good deal in the cases of different enzymes.

"Enzymes work most advantageously in darkness or in
a very subdued light; if they are exposed to bright sun-
shine they are gradually decomposed, the violet and ultra-
violet rays being apparently most powerful in effecting
their destruction. They are often injuriously affected by
neutral salts, alkalies or acids, tho in this respect there
exists considerable diversity throughout the group.

"The enzymes are manufactured by the protoplasm of
the various cells in which they occur, being produced
from its own substance in a manner somewhat similar
to that of the formation of the cell-wall. Usually their
presence is accompanied by a marked granularity of the
protoplasm, due to the formation in it of an antecedent
substance known as a zymogen, which is readily converted
into the enzyme. This granularity does not, however, al-
ways occur, tho we have reason to suppose that the secre-
tion of the enzyme always takes place by successive stages.
The zymogen has not, however, been definitely detected
In all cases.,,

While, as has been stated, the digestion of substances
within the cell is the most common occurrence, there are
riot a few cases, even among the highly developed plants,
where digestive ferments are excreted and act upon mate-
rials exterior to the cell itself. The absorption of food
material stored in the seed is often an instance of this,
"but more strikingly is it seen in the so-called carnivorous
plants, such as the sundew, etc., that were so carefully
investigated by Darwin. In the latter case these plants
can actually utilize the available nitrogenous material pre-
sented in the form of animal substance; in short, meat.

This process of extracellular digestion is, however, more
especially the attribute of the strictly parasitic or sapro-
phytic plants, notably the lower fungi and the bacteria.
Of necessity they must digest from the substratum on
which they grow the necessary food material, unless it

GROWTH AND VARIATION 31 r

happens to be presented to them in soluble and diffusible
form, a circumstance of rare occurrence. The Bacteria
are the most important as well as familiar of such plants,,
and as producers of enormously vigorous fermentation for
their size there are no organisms which approach them.
Their fermentative power has long been made use of in
many industries, and at the present time is the especial
study of preventive medicine in endeavoring to fully un-
derstand and guard against the deleterious effects of
disease-breeding bacteria on the human organism. Asso-
ciated with bacteria, in a purely physiological sense, and
no other, are the highly degenerate fungi known as yeasts,
the power of which in producing extracellular alcoholic
fermentation has been known in a purely empirical way
since prehistoric times.

Ptomaines, toxins, indeed some of the poisons asso-
ciated with so-called toadstools and snake venoms, are
all enzymatic or fermentative in their nature, and a very
small quantity of them is capable of producing relatively
enormous changes in the substances on which they act,
and come under the general physical class of catalytic
agents. The present aim of bacteriological research, as
applied to disease organisms, is to discover the best mode
of combating the toxins, and that has been found in the
antitoxins, which have the power of uniting the toxins
and rendering them harmless, altho it must be said that
the manner in which they do this is not fully understood.

The study of all classes of enzymatic substances in the
living organism, plants as well as animals, is at present
the field which promises more than any other to elucidate
the mysteries of life processes, and with the aid of mod-
ern physical chemistry the next few decades may mark
a striking advance in man's knowledge of what living pro-
toplasm really consists.

"The life of every plant is of limited duration," to quote
from the Text Book of Botany by Strasburger, Nott,
Schenck and Karsten, "Death ensues sooner or later, and

312 BOTANY

the decayed remains form a part of the surface soil. All
existing vegetable life owes its existence to the capacity
inherent in all organisms of reproducing their kind. Re-
production is accordingly a vital power which must be ex-
ercized by every existing plant species. It is also evident
from the very nature of reproduction that in the production

Fig. 35 — Cotyledonic Liberation Variation.
i., Gourd; 2., Asaptida ; 3., Immortelle; 4., cross-section of (3.);
5., Cardopatium. (Kerner.)

of new organisms a process of rejuvenation continually is
being carried on. The descendants commence their de-
velopment at a stage long since passed over by the parents.
"The physiological significance of sexual reproduction
is not at once apparent. In many plants the vegetative
mode of reproduction is sufficient to secure the necessary

GROWTH AND VARIATION 313

multiplication of the species, so that plants are able to
continue without sexual reproduction. Since monoge-
netic reproduction is sufficient for the preservation of the
species, sexual reproduction must answer some purpose
not attained by the vegetative mode of multiplication, for
otherwise it would be altogether superfluous that the same
plant, in addition to the vegetative, should also possess the
sexual form of reproduction, which is so much more com-
plicated and less certain.

"What makes digenetic reproduction essentially differ-
ent from monogenetic is the union of the substances of
the parents and the consequent transmission and blending
of the paternal and maternal properties. It is in this
qualitative influence that the chief difference between
sexual and vegetative reproduction is shown. And this
may be regarded as the special advantage of sexuality.
By vegetative reproduction the quantitative multiplica-
tion of the individual is secured, while by sexual repro-
duction a qualitative influence is exerted. The vegeta-
tively produced progeny consist of unmixed descendants;
the sexually produced offspring, on the other hand, are
the result of a blending of the parents.

"In vegetative multiplication the complex of properties
unfolded in the descendants does not, as a rule, differ from
that possessed by the parent form. The sexually produced
offspring, on the other hand, endowed with the properties
of the father, can never be identical with the mother plant,
but possess the properties of both parents. When these
are divergent they frequently play very different parts in
the descendants, some (dominant) characters appearing
conspicuously, while others (recessive characters) become
less marked or remain completely latent. In this way
the descendants do not exhibit a uniform mean between
the parents, but some may resemble the father, others
the mother. These relations determine the character of
the sexually produced descendants. Variations appearing
in single individuals will, unless they are of an absolutely

314 BOTANY

dominating character, become modified and ultimately lost
by crossing with ordinary individuals. In such a case
sexual reproduction tends to maintain the constancy of
the species. In other cases, as when one parent possesses
new and dominant characters, or when both parents tend
to vary in the same direction, the deviation from the
ancestral form may be maintained or increased by sexual
reproduction.

"The great tendency to variation commonly exhibited by
hybrids illustrates how the equilibrium of the complex
properties of a sexually produced individual is affected
by divergent parental tendencies. But even as a result
of ordinary fertilization not only small and readily dis-
appearing variations (fluctuating variations) but some-
times more striking ones occur, in which the offspring
differs so strongly from the parents in characters which
can be inherited that it appears to be a new species or
sub-species. In such sudden variations (the occurrence
of which Von Kolliker, and with him Korschinsky, term
heterogenesis, while De Vries more recently calls it mu-
tation) these authors seek the starting points of the origin
of new species. This would occur when a particular spe-
cies passes, from unknown causes, into a period of mu-
tation such as De Vries demonstrated experimentally in
GEnothera Lamarckiana. The fluctuating variations which
largely determine the valuable characters of economic
plants — e.g., the high percentage of sugar in the Sugar
Beet — are in contrast to the mutations not fixed on in-
heritance. Careful and continued selection of the varying
progeny is thus necessary to maintain the required stand-
ard of the race."

Hugo de Vries himself says, in writing on this matter
of variability: "Before Darwin, little was known con-
cerning the phenomena of variability. The fact that
hardly two leaves on a tree were exactly the same could
not escape observation; small deviations of the same

GROWTH AND VARIATION 315

land were met with everywhere, among individuals as
well as among the organs of the same plant.

"Darwin was the first to take a broad survey of the
whole range of variations in the animal and vegetable
kingdoms. His theory of Natural Selection is based on
the fact of variability. His main argument is that the
most striking and most highly adapted modifications may
"be acquired by successive variations. The direction of
the adaptations will be determined by the needs in the
struggle for life, and natural selection will simply exclude
all such changes as occur on opposite or deviating lines.
In this way it is not variability itself which is called upon
to explain beautiful adaptations, but it is quite sufficient
to suppose that natural selection has operated during long
periods in the same way. Eventually, all acquired char-
acters being transmitted together would appear to us as
if they had been simultaneously developed.

"Correlations must play a large part in such special
evolutions. Darwin repeatedly laid great stress on this
view, altho a definite proof of its correctness could not
he given in his time. Such proof requires the direct ob-
servation of a mutation. . . . The new evening primroses
which have sprung up in my garden from the old form of
OEnothera Lamarckiana, and which have evidently been
derived from it, in each case by a single mutation, do not
differ from their parent species in one character only,
but in almost all their organs and qualities.

"Some authors have tried to show that the theory of
mutation is opposed to Darwin's views, but this is erro-
neous. On the contrary, it is in fullest harmony with
the great principle laid down by Darwin. In order to
be acted upon by that complex of environmental forces
which Darwin has called natural selection the changes
must obviously first be there. The manner in which they
are produced is of secondary importance, and has hardly
any bearing on the theory of descent with modification.

"A critical survey of all the facts of variability of

316

BOTANY

plants, in nature as well as under cultivation, has led me
to the conviction that Darwin was right in stating that
those rare beneficial variations which from time to time

Fig. 36 — Parental Form of Mutants ('(Enothera Lamarcki-
ana').

A., B., C, leaves from rosette ; D., leaf from middle of flow-
ering stem ; E., bract ; F., flower with petals removed ; G.,
petal.

happen to arise — the so-called mutations — are the real
source of progress in the whole realm of the organic
world.

GROWTH AND VARIATION

317

"The origin of new species, which is in part the effect
of mutability, is, however, due mainly to natural selec-
tion. Mutability provides the new characters and new

_u

Fig- 37 — A Mutant of De Vries (Evening Primrose).

elementary species. Natural selection, on the other hand,
decides what is to live and what to die. Mutability seems
to be free, and not restricted to previously determined
lines. Selection, however, may take place along the same
lines in the course of long geological epochs, thus direct-
ing the development of large branches of the animal and

318 BOTANY

vegetable kingdoms. In natural selection it is evident
that nutrition and environment are the main factors. But
it is probable that while nutrition may be one of the main
causes of mutability, environment may play the chief part
in the decision ascribed to natural selection."

Dr. Daniel T. MacDougal in a lecture published in 1905
tells us that "scattered through the literature of botany and
horticulture of the last century are scores of records of the
sudden appearance of sports and forms of the aspect of
species which fully support all of the conclusions drawn
from the observations on the evening primroses. An ex-
amination of the facts, easily brought together, allows us to
see that certain general principles in the organization of
the plant, and in its behavior in these breaks or salta-
tions in heredity, may be made out.

"The first and most important of these is one which was
advanced by De Vries speculatively, before he began his
experiments in heredity — namely, that the plant is essen-
tially a complex group of indivisible unit-characters.
These unit-characters may not always be expressed or
recognisable in external anatomical characters, since they
'may be in a latent condition or totally inactive.

"Popular belief in the influence of environment and the
inheritance of acquired characters finds its commonest
expression in 'that plants have been changed by cultiva-
tion.' Domesticated races are spoken of as 'garden
forms' by botanists and horticulturists, with the implica-
tion that they are specialized types resulting from the
effects of tillage. Now, so far as actual cultivation is
concerned, this assumption is without foundation, since
at the present time no evidence exists to show that the
farm, garden or nursery has ever produced alterations
which were strictly and continuously inheritable, or were
present, except under environic conditions similar to those
by which the alterations were produced, altho vague state-
ments and erroneous generalizations to the contrary are
current. It is true, of course, that structural and physio-

GROWTH AND VARIATION 319

logical changes may be induced in a strain of plants in
any generation, which may persist in a share to the sec-
ond, or even in some degree to a third, but no longer.
Some very important operations of the market gardener
and the farmer are dependent upon this fact."

"The matter of general scientific agriculture opens an
immense field," says H. M. Richards. "The scientific care
of our forests, for trees may be regarded as a crop,
and their culture agriculture, is a question to which we,
in this country, are awakening none too soon. Forestry,
as practiced in Europe, demanding as it does expert bo-
tanical knowledge, perhaps not by the foresters themselves
but by those who direct their labors, has saved what were
the fast diminishing wooded areas."

"The scientific rotation of crops, the use of fertilizers,
and the study of the physical and chemical condition of
the soil in connection with the living plants," continues
Professor Richards, "involve certain questions which
may mean the success or failure of much farming. These
questions can only be settled by careful investiga-
tions which take into consideration the nature of the
plants themselves as well as the physical conditions
of their environment. Some may say that knowledge
along this line has been satisfactorily handed down from
father to son; that the farmer knows his business better
than does the scientist; but it is a patent fact that this is
not so. For instance, many a farm which has been dam-
aged for a long period of years by the overliming of the
soil might have been spared had the farmer of fifty years
ago had the knowledge which we now have of the relation
of lime to the other mineral substances needed by the
plant, of when to apply it and when to withhold it. It
is the difference between merely empirical knowledge and
that which is based on scientific principles.

"When the contest comes between virgin soil and long-
tilled land, the latter, no matter how rich it may once
have been, must needs be cultivated more intensively if

320 BOTANY

it is to hold its own. Intensive cultivation requires the
aid of special information, and it is here that scientific
agriculture comes into play. Few people realize that
without artificial fertilizers, the direct outcome of highly
theoretical work on the raw foodstuffs of plants, much
of the farming of to-day would be almost impossible ; and
the proper use of fertilizers is but one of many ques-
tions.

"We are coming now, in this country, to a stage in its
development when scientific agriculture must be seriously
considered. Fortunately, it is being so considered, and the
federal and State establishments devoted to the investi-
gation of these agricultural questions may confidently be
expected, I think, to help in the solving of the practical
economic questions that must arise in the competition of
our own agriculture with that of other lands. The way it
must be done is by the introduction of improved methods,
based on carefully conducted scientific research, that often
find their stimulus in the highly theoretical investigations
of the pure scientist. Thus must the so-called impractical
devotee of science come in contact with the practical man
of affairs, and furnish him knowledge that can be used
for the benefit of all."

Tl. o