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ELEMENTS OF ZOOLOGY

THE MACMILLAN COMPANY
NEW YORK + BOSTON + CHICAGO
SAN FRANCISCO

MACMILLAN & CO., LimiteEp
LONDON + BOMBAY + CALCUTTA
MELBOURNE

THE MACMILLAN CO. OF CANADA, Lrtp.
TORONTO

Kano liorta,

(GROUP OF BUTTERFLIES ON GOLDEN-ROD, TO ILLUSTRATE DISPLAY OF COLOR
ON WINGS.

Above, a fritillary (Areynnis); to the right, a nymph (Brenthis bellone); below, the
monarch (Anosia plexippus) ; to the lelt, a wood nymph (Satyrus),

ELEMENTS OF ZOOLOGY

TO ACCOMPANY THE
FIELD AND LABORATORY STUDY OF
ANIMALS

BY

\ B nal a) 1r na r > s
CHARLES BENEDICT DAVENPORT, PH.D.
DIRECTOR OF THE DEPARTMENT OF EXPERIMENTAL EVOLUTION
CARNEGIE INSTITUTION OF WASHINGTON, AND OF THE
BIOLOGICAL LABORATORY OF THE BROOKLYN INSTI-

TUTE OF ARTS AND SCIENCES, COLD SPRING
HARBOR, LONG ISLAND
AND

GERTRUDE CROTTY DAVENPORT, B.S.

FORMERLY INSTRUCTOR IN ZOOLOGY AT THE
UNIVERSITY OF KANSAS

WITH FOUR HUNDRED AND TWENTY-ONE ILLUSTRATIONS

REVISED EDITION

Netw Bork
THE MACMILLAN COMPANY
1911

All rights reserved

Copyricut, 1900 and 1911,

By THE MACMILLAN COMPANY.

Set up and electrotyped. Published February, 1911.

Norwood ¥ress
J. 8. Cushing Co. — Berwick & Smith Co.
Norwood, Mass., U.S.A.

PREFACE

Tus book has been rewritten to make certain additions that
the experience of teachers has indicated would be useful
and to introduce some of the newer topics of general bionomic
or ecological importance whose study has marked the past
decade. Zoology is a rapidly growing science, and text-books
for secondary schools, no less than for colleges, must fre-
quently be rewritten to give a proper view of the subject.

The additions relating to anatomy are intended to round
out the student’s knowledge as gained from a first-hand dis-
section of certain type-forms. What these forms should be
is left to the teacher, but they are suggested in the treatment
of each chapter dealing with “anatomy and physiology.”
Some work in dissection of types is undoubtedly beneficial,
but the danger must be avoided of making the course primarily
anatomical. There is this great importance of anatomical
study — properly made by the student—that it gives him
an understanding of the internal mechanism of organisms,
including himself. In the modern development of medicine,
which is undertaking more and more to educate the general
public so that it may avoid disease, a knowledge on the part
of every child of the organs and functions of the body will
be of the greatest value. Indeed, it is hardly too much to
predict that some day the importance of the dissection by
every high-school child of a series of types leading to the
mammal shall be regarded as essential for carrying out the

Vv

vl PREFACE

programme of eliminating or at least diminishing the ravages
of tuberculosis and venereal disease upon our population.

On the other hand, an acquaintance with a variety of ani-
mals may well heighten an interest in nature and lift the
mind away from the sordid and petty things of which our
modern life in great cities is all too full. <A love of nature is
a moral tonic.

The Laboratory Guide has been omitted from this volume.
This has been done because the best teachers prefer each to
use his own laboratory guide based upon animals and equip-
ment at his command and his experience as to the work that
is most successful with his own pupils. This is quite as
it should be. With the modern methods of manifolding, a
teacher can strike off in a short time directions to an indefi-
nitely large class, and vary them as he thinks fit from year
to year.

The book remains, not a treatise on the science of zoology,
but an introduction to the study of animals. It contains an
outline of what we conceive to be most important for the
ordinary citizen to know concerning animals, and it will, we
trust, stimulate a few to pursue the study of animals as a life
work with the aim of adding to human knowledge and dis-
covering important guiding principles.

The book is somewhat profusely illustrated. Many of the
figures are from photographs. Many of the photographs of
the late W. H. C. Pyncheon and V. H. Lowe remain; those
of the former being mostly of invertebrates at Cold Spring
Harbor. In addition to those gifts of prints and cuts acknowl-
edged in the Preface of the First Edition, we have to thank
Mr. W. 8. Blatchley for permission to reproduce from his
“Gleanings from Nature” our Figures 95a and 96. For per-
mission to reproduce Figures 412 to 414, 417 to 418, and 420,

PREFACE vil

we are indebted to Messrs. Henry Holt & Co. For Figure 415
we have to thank the Cambridge University Press, and for
Figure 416 the Ray Society. For Figures 517, 318, 519, and
348 we are indebted to the New York Zoological Society
through its Director, Dr. W. T. Hornaday.

During the past ten years, we have received numerous photo-
graphs of animals and habitats. Some of these have been
reproduced for the most part without naming the donors, but
none the less with high appreciation of the gifts.

Finally, we have to thank those teachers who have made
useful suggestions as to how the book could be improved.
We have had helpful criticisms from Mr. J. H. Emerton on
the Spider Chapter, and Mr. W. L. W. Field of the Milton
(Mass.) Academy has read the entire manuscript carefully
and made many suggestions that we have carried out.

It seems improbable that with our increasing submersion
in scientific investigation we shall ever be able to offer another
revision of this book; nevertheless, we shall prize a continua-
tion of that criticism and suggestion from teachers who use
the book which in the past has brought us many friends.

CHARLES B. DAVENPORT.
GERTRUDE C. DAVENPORT,

Cotp Spring Harpor, Lona Isuanp, N.Y.,
November 28, 1910,

CHAPTER

I.
Il.

XY.
XVI.
XVI.

~ XVITI.

XIX.

CONTENTS

PAGE

The Anatomy and Physiology of Insects: The Cricket 1
The Grasshopper: A Study of the Enemies of Vege-

tation . : : 3 : : , : : 2 Slt
The Butterfly: A Study in Animal Coloration . - 29
The Beetle: A Study in Ecology . : ; : . 60
The Fly: A Study of Disease-producing Animals . 76
Lithobius: A Study of Light-shunners ; . . 90
The Spider: A Study of Animal Architecture . . 102

The Anatomy and Physiology of Crustacea: The
Lobster : : ; : : : : é - 120

The Crayfish: A Study in Geographical Distribution 128

Daphnia: A Study of the Food of Fishes. : . 153
The Anatomy and Physiology of Annelids . . . 161
The Earthworm: A Study in Subterrestrial Or-

ganisms. : : : : : p : . 168
Nereis: A Study of Life on the Seashore . : » 182
The Anatomy and Physiology of Mollusca, illustrated

by the Snail : : ‘ ; , ‘ : . 198
The Slug: A Study in Animal Behavior. . . 208

The Fresh-water Clam: A Study of River Faunas . 225

The Anatomy and Physiology of Echinoderms, with +
Particular Reference to the Sea-urchins . ; . 238

The Starfish: A Study of Embryology ; ; . 246

Hydra: A Study of Attached Animals : ' . 260
ix

CHAPTER
XX.
AXE.
XXIT.
XXIII.

XXVIT.
XXVIII.

CONTENTS

Paramecium: A Study of the Smallest Organisms .

The Ancestry of Vertebrates

The Smelt: A Study of Food Supply

The Frog: A Study of the Origin of Land Life

The Lizard: A Study of Dryness Lovers .

The English Sparrow: A Study of Birds and Migra-
tions.

The Mouse: A Study of the Evolution of Domestic

Animals
The Development of the Frog’s Ege .

A Brief Ilistory of the Science of Zoology

ELEMENTS OF ZOOLOGY

ELEMENTS OF ZOOLOGY

CHAPTER I

THE CRICKET: A STUDY OF THE ANATOMY AND
PHYSIOLOGY OF INSECTS

THE cricket is a thing that can move of itself, can feed and
grow and produce young like itself; consequently it is
living. It has numerous external parts and
complex internal organs ; hence it is an or-
ganism. It moves freely from place to
place, and devours and digests solid food ;
and so it is an animal (Fig. 1).

An animal is a complex machine built up
of aremarkable substance called protoplasm
and of materials that it produces. Proto-

3 i hee : Fra. 1.— Cricket,
plasm looks like a jelly, but it is really itself iamatire: Nat.
highly organized, so that the animal ma- sna ee by
chine differs from man-made machines in
having a mechanism inside the very substance of which its
parts are made. Some idea of protoplasm may be got from
Figure 2, which shows a bit of it existing as a free living
animal with no other organs than those essential to all proto-
plasm. But in higher animals the body gains a great size ;
contains huge spaces that are filled with water or air; and is
built up of membranes that cover the surface of the body (the
skin) or line the food-canal and body-cavities, of masses
that support the other parts (the skeleton) or are used for

B 1

2 ZOOLOGY

moving organs (the muscles), of threads that convey mes-
sages as telegraph wires do (the nerves), and of delicate
tubes that convey air or food to the innermost parts of the
body (the air-tubes and the blood-vessels) or carry fluids and
particles from the body to the exterior (the excretory and

SEES p

Fie. 2.—Ameeba, the proteus animalcule. Greatly magnified. n., the

nucleus ; w.v., water vacuoles ; c. v., contractile vacuoles ; f.v., food vacuoles,
E. B. Wilson, ‘‘ The Cell”

reproductive ducts). These parts differ in form and arrange-
ment in different kinds of animals. The study of the form
and arrangement, of the different organs of the body is called
Anatomy; the study of the work the parts do is called
Physiology.

General Form of the Cricket. — What general resemblance
in form is there between a cricket and a cat? Which end
moves forward in locomotion (anterior; the opposite end is
called posterior)? Which surface is next to the earth (ven-
tral), and which is normally turned up toward the sky (dor-
sal)? What different structures does each surface bear?

THE CRICKET 3

Which side is right, which left, and why? Such are the ques-
tions which attention to a living cricket will readily answer.
They are important because these surfaces and sides and
ends are essentially similar even in such unrelated animals
as the cricket and cat, which have this in common that they
move over the ground.

The External Structure of the Cricket (Figs. 3 and 4). —
The cricket’s exterior differs from ours in being covered with
a thick varnish-like layer called the cuticula. This cuticula
is the cricket’s skeleton, for it supports the body and gives
attachment to the muscles of the legs. The cuticula extends
over the mouth parts and even into the mouth. It cannot

Fic. 3.— Side view of female cricket, with legs and wings removed.

stretch and so, in order to let the animal grow, the cuticula
bursts from time to time and is shed. The cricket’s body is
made up of a trunk and appendages. The trunk consists of
a series of rings, or somites (Fig. 4), which are grouped into
three main regions known as head, thorax, and abdomen. The
rings are most clearly seen on the abdomen, where each bears,
on the two sides, a pair of small holes that are the entrance
to the system of air-tubes of the cricket and are known as
spiracles. The thorax is made up of three somites, each of
which bears a pair of legs, and two of them each a pair of
wings. On the head the somites are blended, but the origi-
nal number can be made out by applying the rule that each
somite carries a pair of appendages. There are one pair

4 ZOOLOGY

of feelers (antenne), a pair of jaws, a pair of under jaws
(maxille), and a paired under lip, (labiwm). In addition the
eyes correspond to a somite and there is perhaps one other.
The total number of somites to the body can, consequently,

be computed.

Fia. 4.— Dorsal view of cricket with appendages disarticulated.

The legs are covered with the cuticula, which is thick to
give them strength to support the body, but divided by thin
rings (joints) into segments to permit the legs to bend. The
thick segment nearest the body is called, on account of a
resemblance in position to the upper bone of our legs, the

THE CRICKET i)

femur; the next segment is the é¢bia; and then comes a three-
jointed tarsus. These three divisions are found among in-
sects in general. With fewer, the insect could hardly walk.

The wings are broad, flat outgrowths of the body- wall and,
like it, are covered by the cuticula. Between the two layers
of the cuticula are remnants of a space in which run the
air-tubes — these constitute the wing-veins, while the thin
parts of the wing enclosed by the veins are called wing-cells.
The arrangement of veins and cells in the different kinds of
insects, though following one plan, shows many modifications
in detail. In the cricket the upper wings are more leathery
than the lower, which, when not in use, are folded like a fan
under the protecting upper pair. The hind wings alone are
used in flight. The mechanism of flight is as follows. The
front edge of the wing is relatively stiff, while the hinder half
is loose and flops up when the wing descends and down when
it ascends. Consequently in both up and down stroke the
wing meets a little resistance from behind and on the down
stroke from below as well, and this resistance behind is what
pushes the insect forward, while the resistance below keeps it
up in the air. Each stroke counts a little, and by making
many strokes a second even a heavy-bodied insect can propel
itself in the air. The cricket, however, is very bad at flight
and practically never uses its wings for this purpose.

Organs and Functions of Nutrition. — The mouth of the
cricket lies between and at the base of its heavy jaws. This
is the entrance to a digestive tube that runs through the middle
or axis of the body and has its other opening in the last ring of
the abdomen. As the food passes along this tube it is acted
on mechanically and chemically in different ways, and the
various parts of the tube show special regions each for its

6 ZOOLOGY

particular kind of work (cf. Fig. 5). The food of the cricket
consists of various sorts of animal and vegetable débris, — old
fragments of meat, pieces of cloth or paper, fallen fruit, ete.
Bits of suitable size are torn off by the mandibles and carried
to the gullet, where they are wet by the saliva. Thev then
pass into the crop, an enlarged part of the tube, where the
hard food is held and worked over until it is softened hy

various juices secreted by the glands. The food then passes

Fic. 5.— Longitudinal section of female cockroach to show position
of principal organs, Oe., esophagus; S. gl., salivary gland; S.7r.,
salivary reservoir ; Cr., crop ;G., gizzard ; St., stomach ; R., rectum ;
Ht., heart; N.C., nerve cord. x5. After Miall and Denny.

to the third part of the tube, the stomach. Between crop and
stomach a number of sacs open which secrete the digestive
juices. From the stomach the digested food goes into a long
the intestine — through the walls of which the
soluble portions pass and mix with the fluids of the body,
Finally the indigestible portions collect in the hinder part of
the tube to be from time to time expelled.

Respiration in the cricket is effected by a very different

plain tube

mechanism from ours. From the spiracles on the rings of the
abdomen and the thorax pairs of tubes called trachew enter the
body and divide again and again, going to the main muscles of
the back, to the food-canal and reproductive organs, and to the

THE CRICKET 7

ventral nerves and muscles (cf. Fig. 6). To all of these organs
oxygen is carried by the air-tubes. The problem which has to
be met is how to force the air in and out of these fine tubes.
This seems to be done by bringing the sides of the body together,
thus causing the fluids of the body to press on the air-tubes.
When the spiracle is open, the air is forced out of it; when the
spiracle is closed, the air is forced
from the larger stems into the
finer tubes lying in the tissues.
There is a spiral spring (consisting
of a thickening of the cuticula) in
the inside of the main stems of the
trachee that restores the cylindrical
form of the tube after compression.

Circulation in the Cricket. — In
the higher animals the food dis-
solved in the food-canal is carried
by tubes, called hlood-vessels, to the
heart, from which it is pumped to all
parts of the body. The blood-ves-
sels carry not only fluid food but
also oxygen and bring away waste

from the tissues. In insects, as we Fic. 6.— Alimentary canal of
cockroach. x}. Miall and

xygen is carri
have seen, oxygen is carried by a ‘Denny.

special system of air-tubes. The

digested food passes through the wall of the food-canal into

the cavity of the body. In the body-cavity it is kept in slug-

gish circulation by the heart, — a long dorsal tube full of holes,

— the pulsations of which drive the body fluids forward.
Excretion in the Cricket. — In every chemical laboratory

there are obtained, in addition to the useful things sought,

8 ZOOLOGY

certain useless or waste by-products, and these have to be
carried away. So in the living body, which is a sort of chemical
laboratory, there are many waste products, and these have to
be taken from the tissues where they first appear and conveyed
to the outside of the body. In insects these waste products are
picked up from the body-fluids by means
of tubes that empty into the intestine.
From the intestine they pass with the un-
digestible food matter to the outer world.

Reproduction in the Cricket. —A
starvation, floods,
severe cold, attack by other organisms

variety of accidents

— kill vast numbers of crickets each year.

The normal number is maintained only

by reproduction, or the production of new

ones. While in some animals reproduc-

tion takes place by a division of the
parental body into two nearly equal in-
dividuals, in the higher animals usually
only a piece of the parent— called a germ-

cell—is set free, and the offspring has to

Fic. 7.—View of ar- develop from this small bit. Also in most
rangement of tracheal
or breathing tubes in

the cockroach. After cells (usually, but not always, from differ-
Miall and Denny. eae he :
ent individuals) must meet and unite
before development begins. To provide food for the de-
veloping young, one of the two germ-cells is of large size
and full of foodstuffs. It is called the egg, and the
individual producing it is called a female. The other germ-
cell is not stuffed with food, but is active and goes into

the egg and through to its centre; it is called the sperm-

animals, but by no means all, two germ-

THE CRICKET 9

cell and is produced by the male. The union of egg and
sperm-cell is called fertilization. The young eggs are formed
in the female cricket within several tubes that lie in the cavity
of the abdomen and together make up the ovary. The ripe
eggs reach the exterior through a tube or duct known as the
oviduct, and in it they are fertilized. The chief business of the
ovary is to produce food for the eggs. In the oviduct the egg
becomes covered with a tough protecting shell. The tip of
the body of the female cricket is drawn out into a long, firm
“ovipositor”’ (Fig. 3), which can be prodded into the ground,
so that the egg that is laid is placed several centimetres below the
surface, where there is less danger of drying up, of being burned
by the sun’s rays, and of freezing and thawing during the winter.

The musculature of the cricket consists, in the abdomen,
principally of dorsal and ventral muscles that bend and
straighten the abdomen, telescope the segments, and aid
respiration. In the thorax and the head are the powerful
muscles that move the wings, legs, and mouth parts. The
muscles are fastened to the outer cuticula, since there is no
internal bony skeleton.

The nervous system of the cricket consists of a series of
central masses of nerve-cells corresponding to our brain and
spinal cord, and a system of nervous fibres running out from
the central masses. The brain lies over the mouth as in man,
but instead of connecting with a dorsal cord as in ourselves,
it connects by means of a nervous ring surrounding the gullet
with a pair of nerve-cords running along the ventral side of
the body. These ventral nerve-cords are united by cross-
strands at points where the cord is enlarged, forming little
brains called ganglia, and from these ganglia nerve-fibres
run out to the muscles and to the sense-organs.

10 ZOOLOGY

The sense-organs of the cricket are not so complex as our
own. Organs of taste have been found in the mouth, and it is
certain that insects can tell one kind of food from another.
The sense of hearing is found among many insects, as the loud
sounds made by some of them indicate. Indeed, in the grass-
hopper there is a membrane on the first segment of the abdo-
men which acts like the membrane of the drum of our ear.
Finally, the organ of sight is well developed. The eyes of the
cricket are a pair of large areas on the head made up of numer-
ous little eyes, each of which sees a part of the field of view.
Consequently the whole eye throws on the sensitive nerve-
endings a series of little pictures which together, like the blocks
of a mosaic, make up the whole picture of what is before the
insect.

CHAPTER II

THE GRASSHOPPER: A STUDY OF THE ENEMIES
OF VEGETATION

LiF originated in the water and made its early development
in the sea. But when, in the course of time, land suitable for
life appeared, vegetation became established there. By means

Fig. 8.— The vegetation-covered land.

of this vegetation the heat of the sunlight falling on the land

became utilized by organisms (Fig. 8). When land vegetation

had become established it offered a rich feeding ground for

animals. Animals cannot, like plants, make use directly of
ll

12 ZOOLOGY

the energy of the sun, but only indirectly by feeding on vegeta-
tion. Now the group of animals that ranks first among the
feeders on terrestrial vegetation is that of insects.

Geology tells us that land plants first became prominent in
what is called the Devonian age, or the age of fishes. At this
time ferns and allied small plants and cone-bearing trees were
already abundant. At this same time the first insects appeared,
and some of them were like our crickets and grasshoppers. In
the next age—the Carboniferous — vegetation developed enor-
mously, and it was at this time that most of our great coal-beds
were laid down by the death of great forests. Insects appeared
in great abundance and variety and most of the lower groups
of insects that we now know were there. So we see that the
development of insect life on the land went on hand in hand
with that of vegetation.

That insects have played well their part as devourers of
vegetation there can be no doubt. We shall have occasion
to see that this is so as we consider one by one the different
groups of insects. One has only to consider the constant fight
that the farmer wages against the insect enemies of crops to
realize how fully able insects are to destroy vegetation. Every-
where the farmer uses poisonous sprays or powders, and even
then his losses by bugs, cotton-boll beetles, potato-beetles,
scale-insects, and the rest amount to many millions of dollars
each year. Asan example of destructive insects none is better
than the grasshopper.

The grasshopper is, like the cricket, an animal belonging
to a group known as insects (technically Hexapoda'). The
group is given this technical name because nearly all insects
have six legs. With few exceptions insects have also both

1From two Greck words meaning ‘‘six’’ and ‘‘legs.”’

THE GRASSHOPPER 13

feelers, or antenne, and air-tubes, or trachee, by means of
which they breathe or respire.

The grasshopper and its allies belong to a subdivision of the
Hexapoda — the “ order” Orthop'tera.1. In the members of
this order the fore and hind wings are unequal, the jaws are
used for biting, and the young, when they hatch out of the egg,
look like their parents, excepting that they have no wings.
While there is, then, during development something of a change
in form, it is not a thoroughgoing or complete one. Insects
which undergo only an incomplete change of form as they

3

grow older are said to have an ‘‘ incomplete metamorphosis.”

”

The name “grasshopper ” is applied to two “ families ” of
Orthoptera, one of which has short horns or antennie; the
other, long horns. Both of these families have long hind legs
used in jumping, and an elongated body flattened from side to
side. This shape enables them to move in between closely
packed blades of grass. The head is wedge-shaped and directed
downwards.

Ecology. — The short-horned grasshoppers, which are the
most clestructive, live in all parts of the world, usually in rather
dry situations, such as sandy slopes and uplands (Fig. 9), arid
deserts, and rocky mountain sides. They all eat plants or
herbs (hence are called herbivorous), and many species go in
flocks or swarms. Such species are said to be social or grega-
rious, While kinds that live alone are called solitary.

Economics. — Grasshoppers are destructive to agriculture.
In ordinary seasons the loss is relatively not great, but almost
every autumn reports of great destruction caused by them
come from different parts of the world. In our country great
injury was formerly done by the Rocky Mountain locust. At

1 Meaning ‘ straight wings,’’ 7c. lying straight out along the axis of the body.

14 ZOOLOGY

Fic. 9.— The home of the short-horned grasshoppers.

various times this species was impelled by some cause, prob-
ably overcrowding, to fly eastward from its mountain home
in countless numbers and to devastate the lowlands as far
east as the Mississippi River. From 1873 to 1877 the Rocky
Mountain locust was so destructive to vegetation in this re-
gion that Congress appointed a commission to investigate the
species. In describing its effect the commission reports :—

“ Falling upon a cornfield, the insects convert in a few hours the
green and promising acres into a desolate stretch of bare, spindling

348 ZOOLOGY

in two long, parallel strings of albumen, which lie coiled at the
bottoms of ponds, hatch out in May, and metamorphose about
a month later.

The frogs (Ranid:e) are almost confined to the Northern
Hemisphere and the East Indies. In the northern United

Fig. 328. — Green frog, Rana clamitans. Nat. size. Photo. of living animal

by W. H.C. P.
States there are some eight species, of which the com-
monest are: the leopard-frog, of green color, with irregular
black blotches edged with whitish; the pickerel-frog, light
brown, with two rows of oblong square brown blotches on the
back ; the wood-frog, living in damp woods, pale reddish brown»
with a brown band on the side of the head; the green frog, of
uniform bright green to brown color, with numerous small
dark spots, and with glandular folds (Fg. 328); and the bull-
frog, of great size, green, with small, faint spots on the
back.

CHAPTER XXIV
THE LIZARD: A STUDY OF DRYNESS LOVERS

IN spreading over the land, animals have come into situations
where rain falls only for a small part of the year. In such
places not only is the ground usually dry, but vegetation is
sparse. Nevertheless, certain animals have come permanently
to occupy even such desert situations, and, indeed, entire
genera or families prefer desert habitats. They are the lovers
of dryness. The animals most common in our own deserts
are certain hard-shelled, black beetles, lizards of many kinds,!
the little sphermophiles, looking like slender chipmunks, with
now and then a rattlesnake. All of these animals and many
others that live and feed on the ground burrow into the soil.
There they remain during the heat of the day, coming forth
at night to feed and seek their mates. These desert animals
must go for weeks or even months without drinking water,
such moisture as they can get being obtained from roots
and green parts of succulent cacti. Almost always the skin of
such animals is hard, preventing the loss of internal waters by
evaporation. Indeed the whole body of these animals seems
to be very dry, and they need only ashght amount of water to
live. Even in ordinarily moist climates there is a great deal
of difference between animals in respect to their need and love
of moisture. While many land animals are found in moist
woods and under damp logs, or by the edges of lakes and

1 Fig. 329.
349

THE GRASSHOPPER 15

stalks and stubs... . Their flight may be likened to an immense
snowstorm, extending from the ground to a height at which our
visual organs perceive them only as minute, darting scintillations,
leaving the imagination to picture them indefinite distances beyond.

In alighting, they circle in myriads about you, beating against
everything animate or inanimate — driving into open doors and win-
dows; heaping about your feet and around your buildings, their jaws
constantly at work, biting and testing all things in seeking what they
can devour.”

The locusts of the Old World are likewise frequently very
destructive. The species that lives in southern Europe, North
Africa, Asia Minor, Syria, Java, and Japan is doubtless the
locust of the Bible. The description given by the prophet
Joel is very vivid and accurate :—

“A day of darkness and of gloominess, a day of clouds and of thick
darkness, as the morning spread upon the mountains; a great people
and a strong; there hath not been ever the like, neither shall be any
more after it, even to the years of many generations. <A fire de-
voureth before them, and behind them a flame burneth: the land is as
the garden of Eden before them, and behind them a desolate wilder-
ness; yea, and nothing shall escape them. The appearance of them
is as the appearance of horses; and as horsemen, so shall they run.
Like the noise of chariots on the tops of mountains shall they leap,
like the noise of a flame of fire that devoureth the stubble, as a strong
people set in battle array. Before their face the people shall be much
pained ; all faces shall gather blackness. They shall run like mighty
men; they shall climb the wall like men of war; and they shall march
every one on his ways, and they shall not break their ranks... .
They shall run to and fro in the city; they shall run upon the wall;
they shall climb up upon the houses; they shall enter in at the
windows like a thief.”

General Development of the Grasshopper. — The common

red-legged grasshopper lays its eggs during autumn in holes
in the ground two and three centimetres deep. The holes are

16 ZOOLOGY

drilled by the horny plates at the tip of the abdomen of the
female. The eggs, 30 to 100 in number, are laid in a mass and
covered with a sort of jelly. The eggs pass the winter in the
eround and hatch in early summer into young grasshoppers.
As the young grow larger they molt several times; that is, they
cast off the cuticula. After each molt the body is left soft
and colorless and, being freed of its hard, tight, varnish-like
coat, it isin a condition to grow rapidly. After each molt the
small wines or wing-pads also become larger, and the relative
sizes of other parts of the body change. Just before the last
molt the young grasshopper crawls up some vertical object,
clutches it firmly with the hind feet, and remains motionless
in this position for several hours. Then the cuticula splits
along the middle of the back. The head and body inside the
cuticula swell. The head protrudes through the split, and
gradually the entire body works forward and out of the old
cuticula, not easily indeed, but with violent writhings and
pullings. The legs and antenne are especially hard to free.
They can pass out through the joints of the old skin only
because they are soft and flabby. But soon after they be-
come exposed to the air the new cuticula, already formed
beneath the old one, hardens into a firm covering. The wings,
which developed in a roll, spread out, dry, and then fold up in
the way we see them in the adult.

Allies of the Grasshopper. — The order Orthoptera, to which
the grasshopper belongs, includes six principal families, which
have certain resemblances to each other as well as points
of difference from insects that belong to other orders.
Typically, they are rather soft-skinned, with long bodies and
long legs. Most of them, except the praying mantises, feed
on plants or on decaying matter. On account of their com-

THE GRASSHOPPER 17

paratively soft skin they are a favorite food of birds and other
animals that eat insects.

The cockroaches (Blattide) are by preference creatures of
the tropics. Those that live in cold climates like dark and
warm places. The few kinds found in our fields live chiefly
under stones and logs, and some of them are wingless (Fig. 10).
The two kinds that are our household
pests were accidentally imported from
Europe. One of these is the small,
brown ‘ Croton bug” which is found
among water pipes in kitchens; and the

other is the large black species common

in sugar-refineries, slaughter-houses,

S,
and bakeshops. Al! are omnivorous,

eating such things as sugar, bread- pre. 10.— Wingless cock-
stuffs, clothing, bookbindings, bedbugs, oe noo Ete
and other insects. The eggs of cock-
roaches are laid in asmall lump, and all enclosed in a single,
brownish capsule through one end of which the young hatch.
The praying mantises (Mantide) have received their
popular name because of the devotional attitude in which the
greatly enlarged front legs are held. Unlike other Orthoptera
they are carnivorous; that is, they feed upon live animals.
They hunt and devour other insects, —some even that are larger
than themselves, — and they prey upon each other. While
most of the species are tropical, one (Fig. 11) is abundant in
our Southern States and another occurs in the Missouri Valley.
The earwigs (Forficu'lidx) resemble short-winged beetles
(page 66), but differ from them in having large pincers or for-
ceps at the hind end of the body. The earwigs (Fig. 12) use
the forceps in seizing prey or in grasping one another. Earwigs
Cc

18 ZOOLOGY

hide during the day under stones or débris of the seashore, or
in flowers on which they feed. Those that hide in débris feed

Fie. 11.— Phasmomantis carolina. Praying-mantis of southern United
States. Nat. size. Copied from Packard.

on living and dead animals and plants found there. They
either crawl about or fly during the night. The name “ ear-
wig’’ seems to have arisen
from an unwarrantable be-
lief that these insects pen-
etrate into the ears of
persons who are asleep.

The walking-sticks and
leaf-insects (Phasmidz)
show to a marvellous de-
gree a likeness to the twigs
and leaves among which
they live. The most re-
markahble forms live in the
tropics. Such have large
wings which resemble in

form, color, and venation

Fic. 12. — Dorsal and lateral views of an either living or dry leaves.
earwig, common along shores (Ani- . e

solabis maritima). Upon those species that

THE GRASSHOPPER 19

resemble dry leaves, blotches looking like mildew are found.
Even the legs may be thin and
expanded so as to resemble
foliage. In our country occur
only the twiglike, wingless
forms known as walking-sticks
(Fig. 13). These walking-
sticks change color to corre-
spond with the changes of
twigs from season to season ;
for the young walking-sticks,
which appear in the spring, are
green like young twigs, but in
the autumn the adults are gray
or brown. This likeness of
animals to things outside of
the animal kingdom has been
called protective resemblance
and has probably become
established because of the
freedom from attack which it
gives to its possessors. Our
common northern species feeds
on leaves, especially those of
the oak. Occasionally it does
much damage to trees.

The long-horned _ grass-
hoppers and katydids (Locus-
tidee) are closely akin to the
type studied. The family in- a ee ee ee
cludes many grasshoppers © stick” (Diapheromeru femorata).

20 ZOOLOGY

found in meadows and marshes (Fig. 14). The Katydids
have their whole trunk and wings green like the foliage
they inhabit. When the large, upper wings are rubbed to-
gether, they vi-

brate and cause
the familiar
note. Other
members of this
group are the
Cricket Grass-
hoppers (Fig.
15), wingless

forms of a

Fic. 14.—Orchelimum, meadow grasshopper. Nat. brown color and

size. Photo. by W. H.C. P.
arched profile,
which live in cellars, under stones, and bark of trees, and the

Cave Crickets, which live in constant darkness.

Fie. 15.— Ceuthophilus, cricket-grasshopper. Two-thirds nat. size. Photo.
by We. C.F,

The crickets (Gryllide) are found all over the world.
They have short, cylindrical bodies and live chiefly in hidden

THE GRASSHOPPER 21

places, such as beneath stones or in holes which they make in
the ground. Their eggs are laid loosely in their retreats.
They make a familiar chirping noise, the blended sounds
of which, as heard on a summer evening, rise and fall in a dis-
tinct rhythm. The rate of chirp seems to be entirely deter-
mined by temperature, so that in the case of the “ tree-cricket ”
one may compute the temperature by means of the formula
T=50+ +s at in which 7 stands for temperature in degrees
Fahrenheit, and N the number of chirps per minute. The
mechanism by which the chirp is produced is as follows: Near
the middle of each of the upper
wings of the male cricket is a

vein of such roughness as to
form a sort of file, and near the
edge of the wing is a thickened
scraper. When the upper
wings are brought in contact
above the body, and the scraper
of one is rubbed across the file
of the other, the wings are set
in vibration, producing the call.

A peculiar form of Gryllidz
is the mole-cricket (Fig. 16),
whose fore feet have become

much modified for burrowing.

The Orthoptera constitute
one of the lowest orders of in-
sects. The orders described
below in this chapter are also Fie. 16.—The mole cricket of

: . : the northern United States
of simple organization: — (Gryllotalpa borealis).

ZOOLOGY

The order Hemiptera includes certain insects which resemble
the Orthoptera in undergoing an incomplete metamorphosis ;
so that the young, or larve, look much
like the adults in form and develop
without sudden transitions. They dif-
fer from the Orthoptera in having mouth
parts adapted to piercing tissues and
sucking the Juices of animals and plants.
There are two main groups; namely,
the True Bugs, or Heteroptera, in which
the first pair of wings are thick at the
base but have thin tips overlapping
each other over the back (Fig. 16), and
the clear-winged bugs, or Homoptera,

I'1c. 17. — The Spined Tree-
bug. After Lugger. in which the entire wings are thin and
transparent and rest in contact over the back like the sides
of a roof,
The suborder Heteroptera includes a vast number of insects
usually of small size and of very varied habits.

live under the water and are

Some of them

known as water-boatmen,

back-swimmers, water-scor-
pions, and giant water-bugs.

Others skip over the surface

of the water and are known
(Fig. 18),

as water-striders

while still others live only on
land. Some of the latter, such

as the chinch-bug, squash-

bugs, and stink-bugs, are very destructive to plants.

Fic. 18.—(Hygrotrechus.) The
water-strider. Nat. size. Photo. by
W.H.C. P.

Still

others, such as the assassin-bugs (Fig. 19), kill injurious in-

THE GRASSHOPPER 23

sects, and hence are useful to agriculture.
To the Heteroptera also belongs the bed-
bug, a loathsome human parasite, most
of whose near relatives live in flowers.
Thus out of the Heteroptera, a prevail-
ingly herbivorous group, there have
arisen, through the acquisition of new
habits, certain carnivorous forms, and
finally certain parasitic ones. The ex-

treme case of degeneration in this series F1¢- 19. — The assassin

bug, Reduvius. Black.
is the family of lice, which have become Nat. size. Photo. by
permanent Makers
parasites, being unable to eat
anything except the liquid or
semiliquid food afforded by their
“ hosts.”

The Homoptera include insects
of very diverse size and form.
The largest are the cicadas, or
“locusts” (Fig. 20), some of
which have the remarkable habit
of requiring thirteen or seventeen
years for their development.
Consequently these cicadas ap-
pear only at intervals of thirteen
or seventeen years. The eggs
are laid in twigs, the young drop
to the ground, bury themselves,
and live by sucking juices from
Fic. 20.— Cicada septemdecem, the the roots of trees. Eventually

seventeen-yearlocust. Reduced.
Photo. by V. H. L. they come to the surface, leave

24+ ZOOLOGY

their larval skin (Fig. 21), and fly away as full-grown cicadas.
In the case of our more familiar species of cicada there is a brood
every year.

Besides the cicadas the Homoptera include the little leaf-
hoppers and tree-hoppers, the very destructive scale-bugs
(Fig. 22), the mealy bugs, most of
which attack fruit trees and their
fruits, and the plant-lice, or aphids
(Fig. 23).

The following groups, containing
relatively few important species,
are placed in this chapter with the
Orthoptera although they are not
closely related to that order.

The may flies (Ephemeride)
are large winged insects which are
seen in great numbers in early
summer. Their fore wings are
finely veined and much larger than

the hind wings. The mouth parts

are rudimentary, and there are two
Fig. 21.— Pupal case of cicada. &

Two-thirds nat. size. Photo. OF three threadlike appendages at

by W. H.C. P. the tail end of the body (Fig. 24).
As the systematic name implies, they have a very ephemeral
existance in the winged or imago state. The imagos appear
in swarms, eat nothing, and live only a few hours, to deposit
their eges upon or under stagnant water. The larve hatch
in the water, feed upon small aquatic plants and _ insects,
breathe by means of gills borne upon the back, and live in this
immature condition for one, two, or even three years (Fig. 25).
After many molts the winged form emerges from the water

THE GRASSHOPPER

into the air, but, unlike all other insects,
it undergoes an additional molt just before
laying its eggs. As the insect is subjected
to many accidents in its long and defence-
less larval life and in its brief and precarious
winged state, each species is preserved
only by producing an enormous number
of young.

The dragon-flies (Odona'ta) have four
membranous, net-veined wings, of which
the front pair are never larger than the hind
ones. Their large heads carry relatively
enormous eyes. Two groups of dragon-
flies may be distinguished according as the
wings when at rest are extended (Fig. 26)
or folded together over the back. Dragon-
flies live on the wing, hovering over water
and preying upon other insects, especially
mosquitoes. The eggs develop in the water
into aquatic larve which are quite unlike

Fic. 22.—A_ scale
insect (Lecanium).
Remains of females
after production of
young; seen ag
swellings on the
bark. Nat. size.
Photo. by V.H. L.

Fig. 23.—A woolly aphis (Schizoneura)
on apple twig. Photo. by V. H. L.

the adult. Especially the
jaws are peculiar, being
jointed and capable of be-
ing suddenly thrust out, in
order to catch the animals
which serve as prey.
These larvee are easily
reared over winter in an
aquarium, where not only
their ferocious habits, but
also their peculiar method

26

ZOOLOGY

of breathing by means of water taken in at the tail end of

the food-canal, may be observed (Fig. 27).

Fic. 24.— An adult May

fly.

White ants, or termites (Isoptera, Fig.
ants, live a very similar social or communal life.

fly.
Haswell.

Fic. 25.— A larval May
From Parker and

28), while not true

They differ

from ants in the venation of the net-veined wing (when present).

Fic. 26.—Two North
American Odonata, be-
longing to the family
Libellulidee. About one-
half nat. size. Photo. by
VE,

in wood or under stones.
ants occur in any community:

White ants are most
abundant in the
tropics, where they
build great conical
nests of sand ce-
mented by their sa-
liva; but they are
found also in tem-
perate countries.
The common eastern

termite (Termes

flavipes) ranges from

Massachusetts
southward, and lives

Fic. 27.—-Old larva
or pupa of Dragon-
fly (4Eschna). Nat.
size. Photo. by

We EiiG: iP:

Three kinds or castes of white
(1) workers, with small,

round heads and con-
cealed mandibles; (2)

soldiers, with

square heads and long,
powerful mandi-
bles; and (3) the royal
class of kings and
queens, which have
wings until after the

marriage flight.

the males and females from the various
colonies fly forth to mate, and thus a breed-

Fig. 29. — Cory-
dalis, the dobson.
Two-thirds nat.
size. Photo. from
life by W.H.C.P,

THE GRASSHOPPER 27

large,

At acertain time in May

ing takes place between

colonies. Only a few Joy oh. Wweeaes
of the pairs, however, queen termite.
find workers to aid them in establishing a
new colony. The queen, after she is estab-
lished in a new hive, merely produces young,
the abdomen becoming immensely swollen
and elongated to fifteen centimetres with
the eggs which are about to be laid. In
tropical countries the termites are trouble-
some to man by injuring trees and devouring
the woodwork of houses.

The order Neuroptera includes certain
insects which differ from the Orthoptera
in having larve very unlike the adult,
and in having a resting pupal stage in
which the metamorphosis into the adult is
completed. There are four clear, net-veined
wings, and the mouth parts are used for

28 ZOOLOGY

biting. The largest representative of this group is the
Horned Corydalis (Fig. 29), whose larva lives in streams
and is called the dobson. The adult is found among fallen
leaves or on tree-trunks.

The ant-lions are of interest because of the peculiar habits
of the larvee, which live in sheltered sandy places and make

Fic. 30.— Life history of ant-lion. Larva in their pits; one on surface at
right ; ball containing pupa in centre ; adult at left. From Bailey-Coleman,
‘ Biology.”

funnel-shaped pits a few centimetres in diameter. The sides
of the pit are so steep that if an ant by accident falls into
it and attempts to emerge, it will slide down to the bottom
with the rolling sand. The larva lying in wait buried in the
sand at the bottom, quickly protrudes its jaws and grasps its
luckless prey (Fig. 30).

CHAPTER III

THE BUTTERFLY: A STUDY IN ANIMAL
COLORATION

Butrerriuirs, together with Moths, belong to the order
Lepidoptera,'! insects that when fully developed have long,
coiled, sucking mouth parts forming, together, the proboscis,
and large, membranous wings covered
with colored scales. All Lepidoptera
undergo a complete metamorphosis.

Lepidoptera occur on all continents, but
there are more species in the tropics of
South America and Africa than elsewhere.
The number of known species is over
twenty-five thousand.

General Development. — The Lepidop-
tera in their development from the egg
undergo fundamental changes in form.
The eggs, of which the female may lay
several hundred, consist of a germ en-
closed in a tough coat or egg membrane.

Fig. 31.
As the germ develops, the membrane

finally bursts and a little wormlike creature emerges. Its body
is made up of a number of rings placed one behind the other.
The first of the rings is the head and bears the biting jaws.
Certain of the rings that follow bear legs which end in claws.

1 Lepis, scale; petron, wing.
29

3 ZOOLOGY

Some of the hinder rings bear short, stubby feet. This is the
larval stage of the butterfly, and is commonly known as the
caterpillar (Fig. 31).

The caterpillar feeds ravenously and grows rapidly. Its
body is enclosed in the cuticula. As the caterpillar grows,
this skin is put under tension until finally it bursts at the

Fic. 32.— Molting caterpillar. Fic. 33.—Period of stretching; old
cuticula to left.

anterior end (Fig. 32), and the caterpillar emerges, provided
with a new cuticula formed beneath the old one. This new
cuticula is, at first, elastic, and the caterpillar takes advantage
of this fact to increase its length and diameter by as much
as one-third (Fig. 33). The new skin rapidly hardens, and so
confines the ever-developing caterpillar until it is again unable
to withstand the internal pressures. Then another molt
occurs. Thus the cuticula of the caterpillar makes it neces-
sary that growth should not be continuous, but should proceed

THE BUTTERFLY 31

by jumps. From one molt until the next constitutes a stage
in the caterpillar’s development, and most caterpillars pass
through several of these stages. In the last stage the caterpillar
ceases to feed and wanders about until, having reached a suit-
able locality, it molts for the last time. It is now shorter
and stouter and is
covered with a
much thicker cutic-
ula, and in this

stage remains mo-
tionless for a long
time. In this ap-
parently quiescent
stage the future
butterfly is known
as the pupa. Some
caterpillars spin a
web of silk about

themselves known
as the cocoon
(Figs. 34,35). The
cocoon is attached
to some object
above ground. Others pupate above ground, protected only
by a thick cuticula, while still others pupate under ground
in a sort of cell which in some species is lined with silk or silk
mixed with the hairs of the caterpillar.

The inactivity of the pupa is only apparent. Inside the
cuticula, development is proceeding rapidly, leading to a
very fundamental change of form. From the back of the
animal there grow out wings, and from its head antenne and

Fia. 34.— Cocoon.

32 ZOOLOGY

the proboscis, while from the under side grow three pair
of feet. These may be seen pressing against the wall of the
pupa. Finally, the cuticula of the pupa bursts, and there
emerges the last stage of the butterfly, known as the imago. The
wings, which are at first folded, are broadly expanded and
dried, and then the
butterfly is ready
to take its flight
(Frontispiece).

Ecology. — But-
terflies feed mostly
during the larval
stage (Tig. 36) ; the
pupa can take no
food; the adults of
many species touch
no food, but in
other cases suck
the nectar of flow-
ers, the sap of
plants, and the

juice of fruits. The

Fig. 35.— Cocoon, cut open to show pupa. larvee feed, aS ck
rule, on plants; but
a few, such as the clothes-moth and certain enemies of scale-
insects (page 24), feed on animal matter. The plant feeders
differ in the variety of food they use. At one extreme we
have forms that starve unless they can reach their own par-
ticular food-plant ; at the other extreme there are caterpillars
which can live upon the foliage of many kinds of plants.
Certain families of plants are especially preferred by cater-

TUE BUTTERFLY 3

pillars as food. Thus of the hundred species of New England
butterflies, eight feed upon oaks, eleven upon willows, thirteen
upon the rose family, and twenty-eight upon the pea family.
It follows from the restricted food of many caterpillars, that
the range of the species must often be determined by that of
its food-plant.

The imagos fly in the daytime, especially in the sunshine.
Certain species are characteristic of the roadside, others of
meadows, gardens, or woods, while

still others are found flying every-
where. Owing to its ordinarily
short life, the imago is usually
found not far from its larval food-
plant, upon which it lays its eggs.
The Wings of the Butterfly. —
The most conspicuous organs of the

butterfly are, its wings, and of all
insects the butterfly has the largest
wings. The wings are conspicuous
not only on account of their size,

}

but also the brilliant colors which

—

they usually wear. Our common- ;
- Fic. 36.— Feeding larva.

est butterflies are known to every

lover of the fields owing to their striking white, yellow, red,
and blue colors. While for most animals inconspicuousness
seems to be advantageous, butterflies and a considerable num-
ber of moths make no effort to hide their colors. The Lepi-
doptera stand in the insect world as a type that has developed
organs for the display of color. Of the meaning of the color
display of Lepidoptera we have only imperfect. knowledge.

Many of them are protected from the attack of their natural

D

3 ZOOLOGY

enemies — the birds —by a disagreeable taste, and their
bright colors serve to remind birds of their inedible nature
and so afford them greater immunity from attack. But this
can hardly be a complete explanation of the color of
Lepidoptera, for many nocturnal species have strikingly
beautiful color patterns. We shall consider directly some
special uses to which the coloration of Lepidoptera has been
put.

The Broods of Butterflies and their Polymorphism. —
Butterflies winter over in various stages, some in the egg stage,
some as larvee, others as pup or as imagos. Some kinds
pass the winter in either of two stages. In whatever stage
they tarry, the life current runs very slow, and during this
season few changes take place. In the spring, development
goes on rapidly: the winter generation becomes mature and
a summer generation is started. Frequently there is more than
one brood produced during the summer, even in the Northern
States. Farther south two and even three summer broods are
still commoner. Where two or three broods occur they may be
quite dissimilar. This is very strikingly illustrated in the case
of the Zebra Swallow-tail (Papilio ajar) of the southeastern
United States, which has more than one brood each year.
The early spring form (“ marcellus’”’ form) is the smallest,
and has the tail tipped with white ; the summer form (“ ajax ’’)
is the largest, and has the tail two-thirds longer than the
marcellus form. Other illustrations of this seasonal difference
are given by the imported Cabbage Butterfly, the Gray-veined
White, and the Spring Azure. This dissimilarity between the
broods of different seasons is known as “ seasonal dimorphism ”’
or “ polymorphism.” The cause of the difference between
the different broods seems to be the dissimilar weather

THE BUTTERFLY 385

conditions, especially heat, under which they have developed.
Mr. W. H. Edwards in this country, and Weismann and others
in Europe, have shown that, when the summer brood is kept
during development in a refrigerator, the butterfly has the color
of the winter form.

Protective Resemblance and Mimicry.— Every one who has
visited a natural history museum must have noticed that the
polar mammals are apt to be more or less white, while those

Fic. 37.—Catocala ilia, the underwing. Upper wings, bark color; lower
wings, black with orange bands.
which live in tropical forests are dark. It is easy to under-
stand that these colors in their proper surroundings make the
animals which wear them hard to see. This may be of advan-
tage in enabling them to escape the observation of their
enemies, which are seeking for them, or to avoid being seen
by their prey as they approach. This general resemblance
to their background is seen even in some caterpillars, e.g. the
tomato-worm, which is colored so exactly like the leaf on which
it feeds that it is hard to find. Other caterpillars, belonging
to the family of ‘‘ measuring worms,” have the color of the

36 ZOOLOGY

twigs of the plant on which they feed, and the resemblance is
heightened by the way they have of stiffening and standing
out like a branch from the stem. A common genus of moths

Fic. 38.— A, Kallima, the leaf-butterfly of the East Indies, flying; a, at rest.
B, Siderone, another leaf-butterfly, flying ; b, at rest.
(Catoca‘la, Fig. 37) which fly by night and have showy hind
wings, rest by day on trees, showing only their fore wings,
which so closely resemble the bark as to be almost indistin-
guishable from it. Still more striking is the resemblance which

THE BUTTERFLY 37

we find between some adult butterflies and dry leaves as seen,
for example, in Kallima, a butterfly of the East Indies (Fig. 38).
The resemblance of the butterfly to the leaf extends even to
details, for the clear patches on the wing resemble holes,
while little circular markings resemble the patches made by
particular kinds of fungi. This resemblance of an animal to
inanimate objects in its environment is known as protective
resemblance.

Examples of the species of butterflies which appear to be let
alone by birds, owing to their disagreeable odor or acrid taste,
are the Danaidz, to which family our “ Monarch ” belongs.!
Closely resembling the Monarch in this country is the “ Vice-
roy” (Limenitis archippus). This resemblance of the ed-
ible Viceroy to the inedible, acrid Monarch is, it is believed,
sufficient to deceive even the birds, and thus the Viceroy
gains considerable immunity from attack. This resemblance
of an edible to an immune species is known as mimicry.
The origin of protective resemblance and mimicry are both
explained by the theory of Natural Selection, or Darwinism.
Since either of them is of great utility to the organism, their
possession, even to a slight degree, however accidentally gained,
will give their possessor an advantage over its neighbors in
the struggle for existence. Consequently it will be more apt
to survive and transmit its peculiarity to its offspring. By

this means an adapted race will arise and crowd out the un-
adapted.

Protective resemblance and mimicry in other animal groups.
— Although Lepidoptera afford the best examples of protec-
tive coloration and mimicry, these phenomena are not con-
fined to this group. Other insects besides the Lepidoptera

1See Frontispiece.

38 ZOOLOGY

show adaptation in color and form with reference to their
environment. The case of leaf and stick insects has been
referred to on page 18. Grasshoppers found on beaches and
other sandy areas are much lighter than the same species in
erassy meadows. Some of the true bugs, which live on
shrubs, resemble thorns. Some flies (page 82) mimic bees in
shape and the humming sound that they make; and certain
beetles almost exactly resemble the bark and lichens on which
they occur. Among mammals and birds the stripes with
which their coat or plumage is marked serve to break the
uniformity of coloration in the same way that the lights and
shadows break the uniformity of a landscape. The striped
animals blend into the landscape and so become inconspicuous.
The spots on certain deer closely resemble the flecks of
sunlight in the forest (Fig. 39). The light color of the
under part of animals serves to reduce the effect of shade and
so to do away with the sudden transition between the ground
and the animal’s body (Fig. 361). Many of the lower
groups of animals, such as fishes and lizards, are able to
change the color of their bodies so as to make them harmo-
nize with their background. Thus the flatfishes or flounders
are much lighter when they rest on clear sand than when they
rest on muddy bottoms, and crabs, by permitting the growth
of seaweed on their backs, become hidden from their
enemies. Other inhabitants of brilliantly colored coral
reefs have the colors of coral. Thus adaptations in color and
form are widespread, and the general theory expressed
in the preceding paragraph serves to account for them
wherever found. But it would be rash to assert that every
detail of form or color had been determined by the struggle
for existence.

TUE BUTTERFLY 39

Economics. — The Lepidoptera in general are very de-
structive to vegetation. In the review of the different families
that follow there will be found an account of some of the more
important economic species. Unfortunately we have in this
country not only an abundance of injurious native species,

Fic. 39.— A ‘sylvan scene...
Where shadows dark and sunlight sheen,
Alternate come and go.”

but many exotic forms that have been imported. When these
forms were removed from their natural enemies their fecundity
was left unchecked, and the result has been that they have
brought great devastation on vast agricultural districts. The
earnest attempt of a state to keep down for a while an intro-
duced pest, even at great expense, is commendable. Among
the useful Lepidoptera are the silkworms, of which the most
important belong to a single family (Bombycidze) described
below.

+0 ZOOLOGY

Types of the Butterflies.—The Swallow-tails (Papilio)
are our largest butterflies. Here belong the yellow Tiger
Swallow-tail (turnus), with black stripes, which is found over
nearly the whole United States; and the black Swallow-tail
(asterias), whose wings are crossed by rows of yellow spots, and
whose hind wing bears an orange, black-eyed spot. Its larvee
feed on wild or cultivated composite plants, especially parsnip
leaves.

The cabbage-butterflies (Pieris) have white or yellowish
wings, tipped and spotted with black, or sometimes with
orange. They hover over damp spots in roads or fly through
garden patches. The larvie are very destructive and feed on
cabbage and related plants.

To the Nymphs belong the Angle-wings, whose fore wings
are notched on their outer edge. Here belongs the butterfly
which we sometimes see on warm days in winter or early spring
—the Mourning-cloak. This has purplish brown wings with
a broad yellow border, and a row of pale blue spots. The
Graptas belong here, too; they may be told by the silver spot
on the hind wing.’ In the Admirals the wings are less deeply
notched. The red Admiral is purplish black above, with an
orange band and white spots running obliquely across the
upper side of the fore wing. It occurs in England as well as in
the United States. Here belongs also the Viceroy, which is not
closely related, but is quite similar to the Monarch because
the former mimics the latter.) They are both of a tawny
orange color, with a white-spotted black border on the outer
wing margin. The Monarch is the larger and, like the birds,
has the habit of migrating southward in the fall and returning
in the spring. The Fritillaries? include some large butterflies,

1 Trontispiece. 2 Thid.

THE BUTTERFLY 41

having numerous round and triangular silvery spots on the
under side of the hind wing.

The Spring Azures (Lyczenas') include small satin or steel-
blue species which exhibit marked seasonable polymorphism ;
the Coppers, orange-red or brown species ; andl the hair-streaks,
or Theclas,® small, brown butterflies usually with two tails to
the hind wing.

The Hawk-moths (Sphingide?*) fly swiftly and powerfully,
and as they hover over flowers at dusk can hardly be
distinguished from humming-birds. The larvae have a

Fia. 40. — Smerinthus geminatus, the twin-spotted sphinx. Nat. size. Photo.
by W. B.C, 2.

caudal horn or tubercle. The commonest of these are the
tomato or potato
There are about one hundred species of the hawk-moths in
the United States. The Twin-spotted Sphinx (Fig. 40), so
called from the black spots of the hind wing, is destructive to
fruit and shade trees. The Pandorus Sphinx (Fig. 41) is of a
beautiful olive color; its larva feeds on vines.

“ce

worm,” green in color and handed.

1 Lukaina, a poetic name of Venus. 24 Greek feminine name.
3 From Sphinz, or sphinx, a fabled monster. The larva of this moth as-
sumes an attitude like the sphinx.

42 ZOOLOGY

The wood-feeders (Xylotropids!) are chiefly medium to
small, clear-winged species which fly at dusk or in daylight.
Their larvee live in stems of squash, cucumber, etc., and bore
into shrubs and trees (Fig. 42).

The Tiger-moths (Arctiide *) are for the most part con-
spicuously striped or spotted. The larvee are very hairy.
The best known is the furry, brick-red and black Isabella

@
Fic. 41.— Philampelus pandorus, the Pandorus sphinx. Nat. size. Photo.
by W. H.C. P.

caterpillar, which can be seen during October in New England,
hurrying nervously in search of winter quarters.

The silkworms (Bombycide*) include, as a rule, large and
thick-bodied moths. Here belong the only moths of use to
man. Of these, Bombyx mori*is the most generally employed
in the manufacture of silk. It originally came from China,
feeds on the leaves of the white mulberry, and is reared chiefly

leulon, wood ; trepho, to feed; beeause the larvee feed on wood.

2? From arktos, bear.

3 Bombyx-like. Aristotle called the rustling silk bomboz ; hence the name
Bombyx for the silkworm.

4morus, a mulberry tree.

THE BUTTERFLY 43

in China, Japan, Italy, and France. The method of culture
is as follows: The eggs (‘‘grains’’) are laid in the autumn, kept
over winter in a dry, airy, and cool place, and hatched when the
mulberry begins to send out its leaves. On these leaves the
larvee are put to feed, and after

a month they begin to spin.

For commercial purposes the
larvie are induced to spin the
cocoons on prepared twigs or
straw. A few days after the
cocoon is completed its in-
hahitant is killed in hot water.
The cocoon is made of a con-
tinuous thread about three
thousand metres long, of which,
however, only about six hun-
dred metres make good silk.
This long thread has to be
unravelled. The outer end is

: Fic. 42.— Larva of one of the Sesi-
loosened by soaking the cocoon ~ jdwe boring in stem. Nat. size.

in hot water; then several of | Photo. by V. H. L.
these ends are brought together and united to form a
single fibre of raw silk. Another imported silk-moth
common in parts of the United States is the Cynthia!
moth, whose larva infests Ailanthus trees. True American
forms are the brown Polyphemus? moth, whose larva
is colored light green, with oblique yellow stripes; the
Promethea? moth, whose cocoon is formed in a folded leaf
1A poetic name of Diana, from the mountain Cynthus.

2 The name of the fabled one-eyed giant blinded by Ulysses.
2A name in Greek mythology,

44 ZOOLOGY

which is securely fastened by silk threads to its twig; the
Cecropia moth, expanding six inches, whose coarse tegumentary
cocoon is bound along its whole length to a twig; and the

Fic. 43.— Citheronia regalis, the regal moth. Olive and red wings, yellow
spots. Nat. size. Photo. by W. H.C. P.

nearly equally large Regal moth (Citheronia regalis, Fig. 48),
whose larva is our largest caterpillar (Fig. 44). All of these
species are easily reared from the larve or cocoons.

Closely allied to the Bombycids are the Tent-caterpillars,

Fig. 44.— Larva of Citheronia regalis. Head to left. One-half nat. size.
Photo. by W. H. C. P,

which are never of great size.

THE BUTTERFLY

fi
t

{
ob

They are destructive species

which infest apple trees and even forest trees (Figs. 45 and 46).

Fic. 45.— Adult
female of Ch-
siocampa — dis-
stria. From life.
Nat. size. Pho-
to. by V. H. L.

Eggs are laid in a ring-like cluster around a

twig (Fig. 47).
and hatch out in the spring as
young larve. The larve are
eregarious and spin a tent-lke
web, on which they live when
not feeding (Fig. 48). When
ready to transform, they spin a
cocoon made of a yellow powder
mixed with silk.

The Owlet moths (Noctui-

Here they pass the winter

Fia. 46.— Adult

male of Clisio-
campa. From
life. Nat. size.
Photo. by V.
Hed.

dee!) are night fliers and are attracted by our lamplights.
They are the most numerous of all our moths, eighteen hundred

species being known from our country.

Among the largest

members of this group are the Catocala? moths alreacly referred

to.

Here also are placed the boll-worm, which eats cotton-

Fic. 47. — Egg-masses of forest tent-caterpillar, laid on branch.

V.H. L.

Photo. by

pods and green ears of maize; the cotton-worm, which destroys

the foliage of cotton; the army-worm, which devours grass

1From nox, night.

2 kata, below; kalos, beautiful.

46 ZOOLOGY

and young grain; and the myriad cut-worms, of which some
gnaw off young garden shoots at the level of the ground, while
other kinds ascend trees and destroy buds.

Fic. 48.— Nest of Clistocampa disstria, the forest tent-caterpillar, showing
the web and the way the larvee crowd together on it. Photo. by V. H. L.

An allied family includes the Tussock moth (Fig. 49),
whose variegated larva bears dense brush-like tufts of whitish
hairs on the first four abdominal segments, and is very
destructive to shade trees in our cities; the Gypsy moth, im-
ported some years ago into Massachusetts, where the state

THE BUTTERFLY

has attempted its annihilation; and the
Brown-tail moth, also lately imported to
Boston.

The measuring-worms (Geometridae)
are, like the Noctuids, very numerous and
very destructive. They are so called be-
cause the larve have a way of proceeding,
as it were, by inches in their locomotion
(Fig. 50). One of the most important
subdivisions is that of the canker-worms,
which often strip fruit and shade trees of
their foliage.

The leaf-rollers (Tortricids!) comprise
numerous small, moths
whose larve are, notwithstanding, very
destructive. They are so called because
many species cause the leaf on which they

feed to curl.

inconspicuous

One of the most destructive
of these moths is the codling-moth, a great
pest of the fruit-
grower, for the
larva bores into
the hearts of
apples and pears,
causing them to
fall prematurely.

Fic. 50.—A ‘‘measuring
worm.”

47

Fic. 49.—Notolophus,
the Tussock moth.
The wingless female
is shown below a
mass of eggs she has
just laid. Nat. size.
From life. Photo.
by W. H. C. P.

The tineids comprise the smallest
of the Lepidoptera.
frequently bear long fringes.
larvee are so small that they often

Their wings

The

1 From torqueo, to roll or wind.

4

os)

ZOOLOGY

live in the interior of leaves and form winding or blotch-like

(a3 ”

mines”? in them. The larvee of some species make a case

out of pieces of leaves united by silk and carry this about

66

with them. They are known as “ case-bearers” (Fig. 51).

To this family belong the clothes-moth, of which we have three

Fic. 51.— Case-bearing insects on a twig. Photo. from life by V. H. L.

species. They fly in the middle of spring and lay their eggs on
woollen cloth, furs, or feathers, upon all of which the larve
feed.

Another order of insects very different in appearance from
the Lepidoptera but still related to them is the order Hymen-
optera,’ which includes bees, wasps, ants, and certain less well-
known insects. They all have four similar membranous wings
as the Lepidoptera do; but, unlike the Lepidoptera, their
wings are not covered with scales, but are transparent. The
mouth parts are formed for biting or for sucking, but the
proboscis is not so long that it rolls up as in Lepidoptera.

The Hymenoptera belong to one or the other of two groups —
the stinging Hymenoptera, in which the female is provided
with a sting; and the boring Hymenoptera, which are provided

1Hymen, membrane ; pteron, wing.

THE BUTTERFLY 49

with an ovipositor, or long tube, by which eggs can be placed
at some distance below the surface. To the first division be-
long the bees, wasps, and hornets, certain digging or boring
wasps, and the ants. To the second division belong certain
species, —as, for example, the ichneumon-flies, — which are
parasitic on other insects, the gall-flies or gall-wasps, and the
plant-eating Hymenoptera.

The bees (Apidze!) include both social species and those
which lead solitary lives. Of
the latter, some dig their nests

in the ground, others are masons
and build their nests of mud,
others are carpenters and make

tunnels through pithy plants or

even solid wood, while still others p,.. 53—Bombus, the bumblebee.
are leaf-cutters. These leaf-cut- Nat. size. Photo. by W. H.C. P.
ting bees carve circular disks from rose leaves, out of which
they make cells for their young.

Of the social bees, our native species belong to the genus
Bombus,—the “bumble” bees (Fig. 53). The bumblebees
build nests in the ground. The queens alone survive the
winter. In the spring each queen chooses some mouse nest
or other ready-formed cavity in a meadow, and places within
it a ball of pollen. Upon this food she lays eggs, which
develop into worker bees. As soon as the workers are full-
grown they begin the task of gathering food and the queen
then devotes all her energy to egg-laying. Later in the
3eason males and young queens also appear in the nest.
The old and young queens dwell together in harmony until
autumn, when all the members of the colony perish excepting

1From apis, bee.

50 ZOOLOGY

the young queens, which pass the winter in some sheltered
spot and form new colonies in the spring.

The introduced, semi-domesticated honey-bees have quite
a different social economy. In the first place, the nest is
perennial; consequently
the young and old queens
cannot remain in the same
hive, else the nest would
become ‘overcrowded by
the presence of too many
families. As young
queens mature, the old
queen seeks to destroy
them; but she is usually
forced out of the hive by
the workers, a number of

which accompany her.
This migration is what we
call “swarming.” ! When

several young queens Ma-

Fic. 54.—Swarm of bees. Photo. by tyre at the same time,
D. and 38.

duels or repeated swarm-
ings ensue until only one queen remains. When a new colony
is started in a hive or hollow tree, a comb is formed of wax
secreted by the worker bees, and into this the queen depos-
its eges destined to develop into workers. Still later, eggs
destined to form drones are laid in cells larger than
those in which workers develop. The developing young
workers and drones are fed with honey and bee-bread. Honey
is derived from the nectar of flowers which is lapped up

1 Vig. 54.

THE BUTTERFLY 51

by the workers, is stored for a time in the crop, where
it undergoes certain transformations, and is then regurgi-
tated into the cells. The nature of the transformation of
the nectar in the crop of the bee is not precisely known, but
it is not great enough to prevent the characteristic flavors of
the flowers of the buckwheat, orange, and so on, from being
retained in the honey. The bee-bread is made from the pollen
of the flowers, which is brought into the hive on the hind legs
of the workers. When a new queen is needed for the colony,
and the queen cells are empty, one may be produced by the
workers in the following manner: The partitions between
three worker cells are destroyed and two of the embryos are
killed. The enlarged cell is filled with a special nutritive
compound manufactured by the workers and known as royal
jelly. The remaining embryo, fed upon this especially nutri-
tious jelly, develops not into a worker but into a queen.

Of the true wasps (Vespide'), some are solitary; others,
like certain of the bees, rear their families in the nests of other
species (guest-wasps) ; while still others are social. The last
group includes our best-known species. The colony of social
wasps contains males, females, and workers. As in the case
of bumblebees, only the females survive the winter ; in the
spring they build small nests and lay worker eggs. The work-
ers, when grown, enlarge the nest and care for the numerous
progeny of the queen. Our social wasps belong either to the
genus Polistes,?2 which includes the ordinary black, brown, or
yellow bodied wasps, which build mushroom-shaped nests be-
hind window blinds and under boards (Fig. 55) ; or to the genus
Vespa, which includes the black and spotted hornets and yellow-
jackets, that build great masses of paper combs enclosed in a

1 From vespa, wasp. 2 polistés, founder of a city.

52 ZOOLOGY

nearly spherical gray paper envelope (Fig. 56). These are
found attached to trees or parts of buildings. The paper is
made of finely masticated wood-fibre cemented

VW “~~ | by a secretion. Certain vellow-jackets form
ay nests in the ground. The hornets are well
‘ y, known as among the most vindictive of our
\ northern insects, and their sting is capable of
f a producing considerable pain. In all Hymenop-

tera the pain of the sting is due to the introduc-
Fic. 55.— Polistes. 4: a : y nb ep
Slishtly reduced. ton of a poison into the body of the victim
Photo. by W.H. through the stinging organ. This poison is
Cs P: . ,
secreted by a special gland of the insect.
The digger and mud wasps (Fossoria ') have the most varied

abits. One of the most familiar species is Pelopeus,? whic
habits. O f th t famil pecies is Pel 7 which

somewhat resembles a true wasp,
but may be easily distinguished from
it by the long, slender attachment of
the abdomen to the
thorax and by the
fact that the wings

when closed le flat

and horizontal (Fig.
Ns Rea ok ; Fic. 56.— Vespa, a hornet.
57), whilein the true ~ Nat. size. Photo. by W.

Ho. FS

Fic. 57.—Digger wasps they are folded

wasp, showing

like a fan. Other species bore into the pith of

position of wings.
Nat. size. Photo. plants or make burrows in the ground. Many
by W. H.C. P. peek : : .
are predaceous, feeding on spiders, cicadas, ete.

The ants (Formicide *) constitute a well-known group hav-
ing features so marked that other insects, excepting the termites,
will hardly be confused with them. From the termites ants

1Vrom fossor, digger. 2 pélos, slime. 3 From formica, ant.

THE BUTTERFLY 53

may be distinguished by the fact that the first segment of the
abdomen forms a small knot or scale lying between the thorax
and the remainder of the abdomen (Fig. 58).

The intelligence of ants is notorious. This intelligence has
developed in connection with a highly organized social life.
This social life is a communistic one. Homes are built, food
is gathered, wars are made, and domains are defended bravely
and loyally all for the sake of the entire community. The
individual is little regarded, and each one is born to a caste
from which escape is impossible. For, in addition to the dis-

Fic. 58.— Camponotus, the carpenter ant. Uniformly black. Shows scale

behind thorax. Nat. size. Photo. by W. H.C. P.
tinction of sex characteristic of other species, we have here
workers, and these workers may be of different kinds. Thus
certain workers get food and care for the young; others,
which serve as soldiers and defend the colony or conduct war,
are In some cases provided with powerful jaws. In some spe-
cies there are three or more classes of workers, each having its
characteristic form of body.

Ant Colonies. — A colony is founded by a female. On warm
days the young males and females may leave the nests and
take flight in great numbers. This is the marriage flight of
the queens. Within a few hours after nightfall of the day of
this flight the males perish, while the queens settle down to
the ground, tear off their wings, and each of them seeks an

54+ ZOOLOGY

appropriate place to begin the formation of a new colony. If
by chance a queen is discovered by some of her workers, she
is cared for by them; otherwise she must get on alone. She
makes a small nest and lays eggs, which quickly develop into

Fic. 59.— Mound over ants’ nest, Nevada.

workers, which then assume the task of constructing the nest
of the new colony. The nests of our ordinary species consist
simply of tunnel-like passageways dug in the ground and en-
larged at intervals to form small chambers. Most species dig
their nests preferably under protecting stones or the roots of
trees; in other cases a hillock of earth and twigs, an “ ant-
hill,” is constructed. These mounds may attain a diameter
of from six to ten feet (Fig. 59).

Ant Language. — In connection with their communal life
ants have gained a power of communication. By the agency
of their antennee, with which two comrades are constantly

THE BUTTERFLY ve

stroking each other, they can tell each other of the whereabouts
of food, of the approach of an invading army, or of the need
of aid. They distinguish members of their own community
from those of other communities, and recognize one of their
number, even after a long absence, and receive it back to the
colony with demonstrations as of joy.

Social Life of Ants. — To illustrate the complex social life of ants,
a more detailed account is here given of certain interesting species.
Certain ants, such for instance as our Formica’ sanguinea,’ a rust-red
species often found living beneath large, flat stones, make slaves of
another species of ant which (a curious coincidence) is a dark-colored
species. In some slave-making species (the Amazons) the jaws have
become so modified to aid in capturing slaves that they are abso-
lutely dependent upon their slaves for food, and would die sur-
rounded by food were none of their slaves at hand to feed them.

The Harvester Ant. — One of our most interesting ants is the
Agricultural Ant of Texas (Pogonomyrmes * molefaciens*). This ant
makes a circular clearing about its mound, upon which it allows only
one species of grass to grow. The ripe seeds of the grass are carefully
harvested by the ants and stored within the chambers of their mound.
From time to time such seeds as have spoiled in the granaries are
brought out and thrown away. During rainy seasons, some of these
seeds germinate as though planted (Fig. 60).

The army ants, of which there are several species, occur in great
numbers in tropical South America. Like many other species which
live by hunting, they migrate from a locality after having exhausted
it of their food. While on the march, the young of the species are
transported by some of the adults. When an army of these ants
approaches a place, every living animal endeavors to escape. The
breeding birds must be on the alert to pick off the advance guard to
prevent them from returning to the army with news of the presence
of nestlings. Insects of all sorts, young and old, fall a ready prey to

1 Ant. 3 nogon, beard ; myrmex, ant.
2 Sanguis, blood, referring to color. 4 Mole or mound builder.

ob ZOOLOGY

Fic. 60.— Mound and clearing of Harvestcr ant, near Great Salt Lake, Utah.

these swarms.

Some spiders escape by suspending themselves by

their threads, and insects which resemble leaves often find safety in

keeping rigidly still.

Fic. 61.— Pimpla pedalis, a parasite
on the caterpillar of Clisiocampa.
a. male, b. female. Photo.
fee 5 Ee

by

When an army of these ants enters a house, the

inhabitants find it wisest to leave
the invaders in poss

sion, for ina
few hours the house is cleared of
every living thing — moths, cock-
roaches, rats, mice, all have fled
or been devoured.

The leaf-cutting ants are an-
other tropical American species.

The colony is very perfectly organ-
ized. The duties of the workers
are divided among different gangs.
Thus, when a tree has been se-
lected, one gang ascends the trunk

THE BUTTERFLY 57

and cuts the leaves in pieces of a definite shape. The pieces flutter
to the ground, are picked up by another gang and carried to the

entrance of the ant-hill, where
they are deposited to be carried
into the nest by a third relay.
The bits of leaves are used to
line certain of the passage-
ways, and a fungus is grown
upon them which serves the
ants as food. The leaves are
probably stored to provide this
fungus food.

The parasitic Hymenop-
tera have the habit either
of laying eggs in the body of
another insect, — one of the
plant-lice, a caterpillar, or

Fic. 62.— Cocoons of Microgaster, a para-
sitic hymenopter, on a sphinx larva.
Photo. from the living object by V. H. L.

other species, — or else they lay their eggs in the nest of some

species of insect so that the larva can make its own way into
the host (Figs. 61-63). The long, tail-lke ovipositors of the

Fic. 63.— Ophion, an Icbneumon which infests caterpillars. Nat. size.
Phot, by W. H.C. P.

58 ZOOLOGY

female ichneumon are, in some cases, used to drill holes into
trees occupied by insect burrows, so that her eggs can be laid
therein. These parasitic species are invaluable to agriculture
in keeping down injurious insects.

The gall-wasps, popularly not distinguished from the strict
gall-flies, are familiar to us from their works. They lay eggs

Fig. 64.— Larvie of sawfly on grape leaf Photo. by V. H. L.

in various kinds of plants, especially in oaks and members
of the rose family. An excessive growth of the plant tissue,
called a gall, is caused either by a poison dropped into the plant
with the egg, or by the irritation of the developing embryo.!
The galls of gall-wasps are often more or less spherical masses
which are closed, in consequence of which the confined insect
must bore its way out. The galls made by the same species
of insect on one kind of tree are quite similar, but if the same
insect stings another species of tree a different kind of gall is
produced. Also when different species of gall-wasps sting one
1Cf. Fig. 93, p. $4.

THE BUTTERFLY 59

and the same leaf, the galls will be unlike. Hence the char-
acteristic form of the gall is determined both by the species
of plant and by the species
of insect which lives in it.
It is interesting to collect
galls, watch for the emerg-
ing wasps, determine their
species, and thus get their
entire life history. The
gall-wasps are, on the whole,
injurious to agriculture.
The plant-eating Hymen-
optera are extremely de-
structive pests. The young
are known as “‘slugs,”’ from

their resemblance to the Fy. gets Gh Nematua asawhy ona
true slugs, which are snail- gooseberry leaf. Photo. by V. H. L.
like animals. They infest pear trees and rose bushes, leaving
scorched, dried leaves behind them.! Here also belong the
currant-worm and the sawflies (Figs. 64 and 65), which eat
leaves like caterpillars, but differ from them in having twelve
or sixteen prolegs instead of ten.

1See ‘‘ The Pear Slug,’’ in Circular No. 26, 2d Series, U. S. Department of
Agriculture, Division of Entomology.

CHAPTER IV
THE BEETLE: A STUDY IN ECOLOGY

Among all animals the beetles (Coleoptera !) are character-
ized by having developed in the direction of passive resist-
ance to their enemies through the acquisition of a hardened
exterior. We know that seeds are preserved from the depre-
dations of many preying animals and are protected from
unfavorable climatic conditions by an outer covering which
has a great variety of forms, but is always hard, angular, and
unattractive. So, likewise, the beetles are distinguished, on
the whole, by hardness, angularity, and unattractiveness as
compared with the butterflies. Let us see how the insect tvpe
which has produced a body so gorgeous and frail as a butterfly
can be so modified as to form a beetle. We notice first that
the pair of front wings (called elytra) are greatly thickened and
hardened so that they can no longer be used for flying but serve
only to protect the membranous hind wings which are folded
beneath them and on which flight depends. The cuticula of the
head has become greatly thickened, feeding is accomplished
by powerful biting jaws, the horny legs possess powerful spines
and end in claws. These profound modifications of the body
serve likewise to prevent the loss of the fluids of the body so
that beetles can withstand the dryness of deserts as well as
great extremes of heat and cold. In fact, the hard and rigid form
of the beetle which makes it possible for it to live under very
extreme conditions permits it to occupy every niche in nature.

1 koleos, sheath; pteros, wing.
60

THE BEETLE 61

In consequence of this capacity for adaptation there are more
species of beetles than of any other group of animals. Roughly
speaking, one-half of all the insects and one-fourth of all the
species of animals are beetles.

Some of the habitats occupied by beetles we shall now con-
sider. Many beetles run on the surface of the ground even
during the day. Such are the Running or Tiger beetles.
Some live on the ground under stones during the day and go
out at night on foraging expeditions. Others live a great deal
of the time in the air, as, for example, the Fireflies.
Another kind, of which the Potato-beetle is an example,
lives on plants. Certain others, such as the meal-beetles
and the household pest known as the Buffalo-bug, live
buried in dry vegetable matter. In their larval state many
beetles live in the trunks of trees. Still other forms live in
carrion and decaying vegetable matter, and finally there are
many kinds that spend their entire life in water.

In respect to their food beetles are equally adaptable. Some,
like the Tiger and Ladybird beetles, live exclusively on live
animals; others, like the Potato-beetle, feed on the foliage of
plants. Many, like the Snout-beetles, suck the juices of fruits.
Others feed on dry animal or vegetable matter. Still others
devour carrion, and a very few are parasitic on other animals.
In so far as certain beetles feed upon other carnivorous species
of insects, as do certain Tiger and Carrion beetles, or upon small
fish, as do some of the Dytiscide, or upon domestic bees, like
certain allies of the weevils, they may be indirectly injuring
man. Of all the families of beetles, probably the leaf-eaters
cause greatest destruction; next to them come the weevils,
followed by the “ longhorns’’ and the others. Every part of
the plant has its coleopterous enemy. As Le Conte and Horn

62 ZOOLOGY

have said: ‘‘ The function of the Cerambycide is to hold the
vegetable world in check by destroying woody fibre; the Bru-
chide (weevils) effect a similar result by attacking the seeds ;
and the Chrysomelide by destroying the leaves.”

The geographical range of beetles is likewise great. They
penetrate to the tops of the highest mountains. They are
found on the most arid deserts, where they attain very great
size and very great hardness. While they reach their greatest
abundance in the heavily forested tropics, they are found in
extreme northern lands.

During development beetles, like Lepidoptera and Hymen-
optera, undergo great change in form. As an illustration we
will consider the development of the Colorado Potato-beetle.
In this species the orange-colored eggs are laid often in a very
regular manner on the under side of the potato leaf. Here
they develop for several days. In about a week, however,

‘ grub,” comes out.

the young, reddish, black-spotted larva, or ‘
Like the adult beetle, it has three pairs of thoracic legs. After
feeding actively for two or three weeks, the larva descends
into the ground, forms a naked yellow pupa, and emerges in
about ten davs as an adult. From two to four broods are
produced during the year. The adult beetles spend the winter
in the ground, crawling forth and laying eggs the following
spring (cf. Fig. 65a).

The habits of the larve of the different kinds of beetles are
as varied as those of the adults. Some of the larvee live in
the ground with their jaws exposed in wait for prey. Many
wander about to seek food either on land or under water.
Others eat the wood in which they are embedded, while still
others are nourished by the ball of carrion in which the mother
has deposited her eggs.

THE BEETLE 63

The form of the larva also varies much to adapt it to its
surroundings. When the larve live under bark they become
greatly flattened. Those that feed in wood or grain are mostly
cylindrical. Those that live on the surface of leaves, like the
Potato-heetle, are often oval or irregular in shape.

The number of species of beetles which have been described
is probably over one hundred thousand. Of these, over ten
thousand inhabit America north of Mexico. Fortunately

Fie. 65a.— Larva of Lachnosterna, the June bug, at roots of aster. Photo.
of living animals, nat. size, by V. H. L.

this vast number can be included within a relatively small

number of families, of which the salient general characteristics

will here be considered.

The running beetles are characterized by a more or less slender
body, long, delicate legs, and quick movements. They are
found chiefly on or near the ground. There are two principal
families. The first includes the tiger-beetles (Cic’indel’ids '),
which are colored bright brown or green (Fig. 66). ‘They are
light-lovers, heat and moisture lovers. Consequently they are
found in sunny places, especially on paths or sandy shores
which reflect the sun’s rays, and almost always in the vicinity
of water. In their flight they are among the swiftest of insects;

1 Derived from candela, candle.

64

ZOOLOGY

a capacity of which they make use in the capture of living

and especially of flying prey such as flies.

Their powerful

jaws are long and sharp, and so they are well adapted for seiz-

Fic. 66.— Three common species of Cicin-
dela, the tiger-beetle. Left, red-copper
bronze ; middle, brcwn, with yellow mark-
ings; right, bright green, cream-colored
markings. From Packard.

ing and holding fast their
victims. The larve are
elongated, hunchbacked
creatures, with a huge
head armed with long

jaws. They live in ver-
tical burrows, generally
in the vicinity of water.
With their heads close
to the entrances of their

burrows they lie in wait for their prey.

The second family of the running beetles includes the ground-

beetles (Carab’ide').

thousand snecies, of extremely

This family is composed of about ten

varied form, size, and coloration.
Most of them are of a shiny black
color, usually with ridges or rows
of points running along the elytra
(Fig.66a). They are, for the most
part, darkness-lovers and contact-
lovers, and so occupy a very dif-
ferent place in nature from that of

the tiger-beetles. During the day-
time they are concealed under-
neath boards and stones, penetrat-
ing into the narrowest crevices.

changes.

Fic. 66.a.— Calosoma

scrutator,
the searcher, a ground-beetle.
Nat. size. Photo. by W. H.C. P.

But at night their instinct
They fly and climb trees and shrubs in search of

1 karabos, beetle.

TUE BEETLE 65

other insects. Since most of them are moisture-lovers, they
abound chiefly in the neighborhood of watercourses. Although
the majority prey on living animals, some species are vegetable-
feeders. The larve of one species are very destructive in the
Southern States to young Indian corn. Certain forms emit
ill-smelling fluids, often with a popping sound. These fluids
are believed to help defend the beetles from their enemies.

The next two families, both water-beetles, the divers (Dytis’-
cide’) and the whirligig beetles (Gyrin’id”), include bectles
which are quite as destructive to animal life of the water as
the runners are to that of the land. As could be predicted
from their habitat, they are moisture-lovers, contact-lovers,
and cold-lovers. Their shape is peculiarly modified for life
in or on the water. The legs are broad like oars and the body
is pointed at the front and covered with fine hairs which
entangle bubbles of air. The air-bubbles help to buoy the
animal in the water and to afford a supply of oxygen. The
Dytiscide are usually the larger species and have long,
thread-like antenne which they use in testing the character
of the bottom. The Gyrinide, which are small beetles, whirl
around on the surface of the water, often in groups. They
have short antenne. Each eye is divided into an upper
half, used for looking into the air, and a lower half, used for
looking into the water. The larve of hoth of these families
have a long and spindle-shaped or flattened body and live
in the water.

The water scavenger-beetles (Hy’drophil’idze*) make up an-
other family of aquatic beetles that are less strictly carnivorous

1dytikos, fitted for diving.

2 gyros, circle; because this bectle swims in a circle.
3 hydros, water; philos, loving.
F

66 ZOOLOGY

than those of the two preceding families, but they have other
very similar instincts. On account of their living on decaying
vegetation they do not move so rapidly through the water as
the Dytiscidee. They have heavier and clumsier bodies. They
carry a film of air on the lower surface of the body where the
air-tubes open, and thus they are enabled to spend a long time
on the bottom without having to come to the surface.

The short-winged beetles (Staph’’ylin’idie!) are so called be-
cause the elytra cover only a short part of the abdomen (Fig.
67). Consequently they are not capable of
long flight and are found chiefly on the ground.
The family consists of a vast number of species

varying greatly in their behavior, but for the
most part they are lovers of darkness, contact,
and moisture. In consequence of these in-
stincts they are abundant under stones and in
decaying wood and along shores of lakes and
seas where débris is cast on the beach. They
devour both animal and vegetable matter.

Fia. 67. — Astaphy- i :
linid Anthophagus. Indeed, the family includes the great terres-

From Packard. — ¢rjal scavengers among beetles. Their elon-
gated body permits them to penetrate into woody fibre or into
the earth for decaying vegetable mold. Since their reactions
are much like those of ants and of termites they are frequently
found associated with these two groups, being even permanent
and regular guests in the nest of such insects. Some species
mimic ants and wasps not only in general form and color, but
also in the movements of the tip of the abdomen, which, when
the animal is irritated, is raised as though to sting (Fig. 68).
The larve are not unlike the adults and inhabit similar situations.

1 Staphylinos, a kind of insect, from staphyle, bunch, of grapes.

THE BEETLE

67

The carrion or sexton beetles (Sil/phide!) include species

with a great range of size and form... Their reactions to light,

moisture, etc., are much like those of the short-winged bectles,
but they have taken a farther step away from the normal food

fer eth

Fic. 68.— Side-view of a staphylinid, clevating its abdomen.

of beetles in that they have come to live exclusively upon car-

rion. Some of them are heavy-bodied, with powerful legs.

When one or more pairs of these beetles discover a dead bird

or small mammal on the ground, they dig out the earth from

underneath and pile it upon the animal
until eventually the carcass is entirely
buried. Then the female deposits her eggs
upon the body, so that a rich supply of food
is provided for the young larvze which hatch
from the eggs.

Another division of the carrion-beetles
are contact-lovers, and accordingly their

bodies are much flattened to enable them to Fie 69.—A carrion

penetrate into crevices (Fig. 69). They
will often be found under the carcass of an
animal lying on the ground. They lay

beetle, Si/pha ameri-
cana. From ‘‘Stan-
dard Natural His-

tory.”

their eges and the young develop in these same restricted

quarters.

1From silphe, the Greek name of an ill-smelling insect.

68 ZOOLOGY

The family of wool-beetles (Dermes’tidz!) includes many
small beetles that love contact and dryness. They feed upon
the dryest sorts of animal matter, such as wool, leather, furs
of all sorts, and dried and salted
meats. They can readily pene-
trate into the midst of such food-
stuffs, on account of their small
size. One of the members of this

family is the familiar Buffalo-bug
Fic. 70.—A dermestid, or mu- shield ee eee: 1

seum pest, Anthrenus. Left, which aevours clothing and car-

larva; middle, pupa; might, pets. Another species devours

adult. From Packard. ; f , i

the dried specimens in collections

of insects and plants such as are found in museums. Conse-
quently such collections have to be subjected several times a
year to the poisonous fumes of carbon disulphide. As in
many other insects, it is the larve, which in this species are
fuzzy, that cause the great destruction (Fig. 70).

The stag-beetles (Lucan‘id:e*) have received their common
name from the resemblance of their long, often branched man-
dibles to the antlers of astag (Fig. 71). In the

case of the giant stag-beetle of the Southern

States, the mandibles are more than three-
fourths the length of the body. The larve are
lovers of contact and moisture, and bore into the
wood of the roots and trunks of trees. The
adult beetle, as its antler-like mandibles sug-

gest, is a lover of freedom, and roves about

living on the sap of trees, which it procures by Fia.71.—Doreus,

] ‘ bs a stag - beetle.
cutting through the thin bark. Cire ees
The Lamellicorn beetles are distinguished by — by W. H.C. P.

1¥From derma, skin, and esthio, to gnaw. 2 From lucanus, surprise.

THE BEETLE

69

the composition of the tip of the antenne out of a number of
thin plates or lamella. The tumble-bugs or scavenger Lamelli-
corns (Scar’’ab’idez?) are lovers of light and freedom (Fig. 72).

They form balls out of the dung of
various animals which they sometimes
roll long distances. The dung-rolling
habit has long excited interest; in-
deed, among the Egyptians it was an
object of superstition. So high was
the veneration of this people for this
their sacred beetle that they repro-
duced it, in their paintings and sculp-

Fic. 72.— Copris, a tumble-

ture. The ball of dung is really — bug. Nat.size. Photo. by

intended for the deposition of an egg,

W.H.C.P.

and it is rolled by both males and females to a hole in the

ground which has been dug in a safe place for its reception.

The group of leaf-eating lamellicorns is represented by the

Fia. 73.— Macro-
dactylus, the
rose-bug. Nat.

size. Photo.
W.H.C. P.

by

June-bugs. The adults are attuned to a very
low intensity of light, so that they stay in
hiding in the daytime, coming forth at
night to feed upon the foliage of trees and
shrubs. They are, however, attracted by
lamplight, and enter through the open win-
dow with a busy humming sound, but soon
come in violent contact with the wall or a
piece of furniture, and fall heavily to the floor.
The larve of June-bugs are lovers of contact
and darkness. They pass the winter in the
soil in burrows which they construct among

the roots of garden vegetables and other plants (Fig. 65a). The

1Scarabeus, beetle.

70 ZOOLOGY

Rose-bug (Fig. 73), another species of this family, is active in
the sunlight and is destructive to the blossoms or fruit of the
rose, grape, cherry, and other plants.

The Metallic wood-borers (Bupres’tid#!) are destructive to
trees. The larve love contact and darkness, and being pro-
vided with large heads and powerful jaws,
they gnaw their way through the bark and
wood of trees. The adults have an entirely
different behavior (Fig. 74). They love the
sunlight and freedom; hence they are found
upon flowers and the bark of trees. Here
their metallic colors are conspicuous.

Closely allied to the foregoing is the family

Fic. 74.—Buprestis Of click-beetles, or El’’ater’ide.2 These have
rufipes, a metallic
wood-borer. From :
“Standard Natural leaping into the air by means of a special
History.”

the power, when placed on their backs, of

device on the under side of the animal (Fig.
75). The larve, called “wireworms ” because of their round,
hard bodies, live under the bark of trees and of rotten wood
or upon vegetation in the ground. They are most destructive
to sprouting grain, especially
Indian corn. It requires several
years for them to mature.
The fireflies (Lampyr’ide *)
make up another and a well-

known family. They have soft

wing-like elytra, and on the thorax is a great shield, which

partly or wholly covers the head. Certain species that do not
1From bouprestis, a Greek name for a beetle causing swelling in cattle

(bous, ox).
2 elater, driver. 3lampo, to shine; oura, tail.

THE BEETLE 71

give light live on flowers, especially the goldenrod; the lumi-
nous species are active at night. The light-giving organ lies
in the abdomen. The
larvae also are luminous
and are known as glow-
worms (Fig. 76).

In several of the forego-
ing families of beetles the
adults live free, while the
larvee penetrate into wood.
In the family of bark-
borers or engraver-beetles
(Scolyt’idze!), however, the
adult also lives and feeds

in the innermost layers of Fic. 76.—A firefly, Photuris. a. larva;

‘ b. adult. The lines to the left of figures
bark. In this case the represent actual lengths of animals.

adult beetle also is a lover From Packard.
of contact and darkness. As they eat in lines, a pattern is
formed which is characteristic for each species. Along these
lines, niches are made in which eggs are laid and
larvee hatch. The borings are injurious to the
trees, often causing their death. Herbaceous
plants also are infested by certain species. An
example is the destructive Pine-borer (Fig. 77),
which is common throughout the United States
Fia. 77.—Den- and Canada.

droctonus, 20 One of the most injurious of all the families

engraver bee-

tle. Magnified of beetles is that of the weevils (Curcu’’lion’-
2.5 times. F ie : ‘
“ ee ce ae ide). Most of our weevils are small, and their

ural History.” heads are drawn out into a long snout by

1 From skolyptd, to mutilate. 2 curculio, a grain-weevil.

72

ZOOLOGY

which they bore holes in plant tissue to receive their eggs

(Fig. 78).

The dull colors of the beetles render them incon-

spicuous to insect-feeding birds. The num-
ber of species is reckoned at over ten thousand,
and the family is of world-wide distribution,
its dispersion having been aided by commerce.
Grain-weevils are great pests in stored wheat,
rice, or maize. They also lay their eggs in

planted seeds, buds, nuts, stone fruits, and

fleshy fruits.

Fic. 78.— Balani-
nus, a weevil, of
brown color.
From Packard.

of

family
beetles ”

America alone.
very long. The larve bore
into even the hardest woods,
anc live there for two or three
years. Timber and _ shade
trees are thus greatly dam-
aged. A favorite collecting
ground for ‘‘ long-horns is
the goldenrod (Fig. 81).
Still
family is that of the leaf-

another destructive

4

eating beetles (the Chrys’’-

long-horned beetles,
(or Cer”ambyc’ide 4),

Extremely destructive also is the great

“buck-

of which

about six hundred species are known in North
The antennz and legs of these beetles are

omel'ide*), to which the

pie Bice mo ven Fa. 79.—Prionus laticollis, a long-
Potato-beetle belongs. Thesc oa: leek ae eco ene ch
beetles are thick androundin W.H.C. P.

1 kerambyx, a beetle with long horns. 2 Figs. 79 and 80.

%chrysomela, gold beetle.

THE BEETLE 73

shape. They lay their eggs upon the leaves of plants. The
larvee feed on the leaves or burrow in the stem. Usually the
larva is conspicuously colored and exposed, and relies for protec-
tion upon its disagreeable odor and taste. The most cestruc-
tive species to agriculture in the northern United States is the
ten-lined Colorado potato-beetle. Until about 1859 this species
fed upon the sand-bur, at the east-
ern base of the Rocky Mountains
and south into Mexico. With the
advent of settlers and the planting
of the cultivated potato (a native
of Mexico), this more thrifty,
cultivated species was adopted as
its foodplant, and the potato- :
beetle began its eastern migra- Fic. 80.—Orthosoma brunneum,
tion. Tt spread slowly at first, but “2° _Saieht bodied = Pnonid.

Brown color. Nat. size. Photo.
within fifteen years had reached — by W. H.C. P.

the Atlantic coast. The little red, yellow, and black asparagus
beetle; the yellow, black-striped cucumber and melon beetle,
and the tortoise-beetle, whose broad, iridescent, translucent
elytra are conspicuous on the leaves of the morning-glory,
nettle, and other plants, all belong to this family.

So long has become our list of destructive beetles that it
is with satisfaction that we turn at the end to a family which
is almost wholly beneficial to the vegetable kingdom as well
as to most vegetable-feeders, including man. This is the lady-
bird family (Coc’’cinel’lidx!). These beetles hunt their prey
both in the larval and adult stages, feeding upon small insects
and insect eggs (Figs. 82 and 83). They are especially active
in freeing plants from scale-insects and plant-lice. So rapidly

1 From Greek kokkos, kerry.

T4

ZOOLOGY

do the latter multiply that were it not for the voracious larve
of the ladybird, most plants would be destroyed in a single

season. The larve

Fia. 81.—Cyllene robi-
nz, locust borer.

of the ladybirds are dark, spotted, and
hairy. The elytra of the imago are in
most species reddish in color.

The list of beetles directly or indirectly
useful to man is small. The carrion-
beetles, tumble-bugs, and rove-beetles,
which feed upon decaying animal and
vegetable matter, are useful as scavengers.
Of those which serve us by killing other
insects injurious to vegetation, the lady-
bird beetle stands first. The economic
importance to us of this one family can
hardly be estimated. Different kinds of
ladybirds feed on different species of in-
sects. At one time it seemed that the
orange industry, if not that of fruits in
general, was doomed in California on ac-
count of the destruction wrought by the
introduction of a scale-insect. As the
insect had been imported, we had no
native beetle which attacked. Search
was made abroad, and a ladybird beetle
was found in Australia which feeds on

this particular scale-insect. The Australian beetle was intro-

duced into California, and now the scale-insect is subdued.
The larve of some of the checkered beetles! feed upon the
larvee of boring beetles, while the larve of tiger-heetles watch

1A family of rather small beetles, living in flowers and on trees, and
often with contrasting colors.

THE BEETLE 75

at the mouth of their burrows for other insects upon which
they feed. Carabid beetles are said to ascend trees in search
of canker-worms. Larve of ground-heetles prey upen the
pupating plum Curculios, and other
beetles eat cutworms.
One beetle, the blister-bectle,
known in the markets as the Span-
ish fly, has been for ages used as a eters z
drug. When disturbed, there ex- lata. Adult.
a ee eee udes from the joints of this insect ne
lata on a leaf. g liquid serving as a protection, V.H.L.
Nat. size. . F , 2 ‘
Photo. by Since it burns or blisters the disturber. This

MoH ds property is retained in the dried substance. The

article sold in drug stores is obtained from crushing the dried
beetle. The larve of various beetles have been prized as food
by certain peoples from the Romans of Pliny’s time down to
the present, for they are eaten with relish by certain tribes of
South American Indians. Fireflies sewn in lace are sometimes
worn by the Spanish and Cuban women as adornments for
evening dresses, while other beetles with particularly hard
and beautifully colored and iridescent wing-covers are used
as settings in hat ornaments and buckles, as well as in
jewelry.

CHAPTER V

THE FLY: A STUDY OF DISEASE-PRODUCING
ANIMALS

THE great majority of human diseases are due to the multi-
plication in man’s body of other organisms. Such organisms
are known as parasites. Parasites do not constitute a separate
group of organisms by themselves, like the butterflies, but
in almost every class certain species or even whole families
have come to live upon other organisms. The usual history
of the degradation of an animal to parasitism is as follows:
The ancestors of the animal have come to live upon the waste
products of other animals or even upon the outside of other
animals. Later some of their descendants have come to
penetrate into the interior of the host, as the parasitized animal
is called, either through the skin or by way of the food-canal.
It is advantageous for them to do so, because in the interior they
find not only better food, but warmth and protection as well.
The worst parasites are the smallest, because the small ones have
almost unlimited power of multiplication and because most
of them set free substances that act as poisons on the body of
the host. One of the most dangerous groups of these micro-
scopic parasites is that of the bacteria, which are usually classi-
fied as fungi; that is to say, plants without green coloring-
matter. Not all, but nearly all, of the bacteria are parasites.
Fully as dangerous, however, are the parasites belonging to the

76

THE FLY 77

group protozoa, or primitive animals and it is especially with
these that we have to deal in this chapter.

The greatest difficulty that a parasite has to encounter is
how to find a way to pass from one individual to another. After
it has wrought its fatal work upon the body of one individual,
it must be able to reach a new host in order that it may not
altogether perish with the host it has killed. There are two
principal ways in which this transfer from one individual to
another takes place. Either the parasites or their eggs are
extruded from the body of the first host and are taken by a
healthy individual with its ordinary food or water, or else the
parasites are actually conveyed from one individual to another
by means of so-called intermediary hosts. These intermediary
hosts are sometimes animals that devour the carcass of an
animal dead of a disease and are in turn eaten (with the dis-
ease germs) by a healthy individual belonging to the same
species as that which died, or else they are animals that suck
the blood of other animals, and in passing from individual to
individual infect, of course unwittingly, the healthy with
parasites from the diseased. This rdle of intermediary host
is played by the group of flies (Dip’tera') more than by any
other. Consequently the Diptera are a great menace to man
as conveyers of many of the most dreaded diseases to which
he is subjected.

The Diptera are fitted to play the réle in nature of disease-
bearers because of their life history, instincts, and structure.
For the most part they are lovers of heat, so that they are most
abundant in the tropics. It is the Diptera and the diseases
they bear, not the heat, that make the tropics such an un-
healthy or even fatal abiding-place for man and for many of his

1 dis, twice; pleron, wing.

78 ZOOLOGY

domesticated animals. In our climate the Diptera occur
chiefly in houses, stables, and among animals, where the
highest temperatures are to be found.

The larve of some Diptera live in the water, but others dwell
in decaying matter. Indeed, some kinds feed exclusively
upon horse manure and upon other kinds of filth, and others
feed upon our foodstuffs. The larve that live in decaying
matter are slender without even an enlargement for the head
or with any especial organs around the mouth, since they have
only to suck the fluids in which they develop. In accordance
with their structure and habitat we find them loving moisture,
darkness, a high temperature, and contact. The latter instinct
leads them to penetrate into the material in which they breed.
Many eggs are laid by each female parent, and their develop-
ment is very rapid; indeed, many generations are produced
in a single summer.

The imagos, unlike the larve, live a free life and, for the
most part, in the bright sunshine. They have only a single
pair of wings, but they are powerful flyers and are thus well
fitted for their hideous work in disseminating diseases. Their
mouth parts are usually provided with a small, dagger-like
organ with which they pierce the skin. Through the opening
thus formed they suck the blood of their victim. If the victim
is diseased, the Diptera become thus inoculated with the disease,
and when they pass to a healthy animal and puncture its skin,
some of the disease germs may be inserted into the body of the
healthy individual. In this way mosquitoes cause malaria
and yellow fever to spread.

The method of transportation of disease germs described in
the above paragraph, although the commonest, is not the
exclusive method. Wherever flies that have developed in

THE FLY 79

filth or crawled over it to lay their eggs are permitted to walk
over food, they may leave germs on the food. In this way
germs of such intestinal diseases as diarrhoea, dysentery,
typhoid, and cholera are disseminated, provided these cliseases
are present in the neighborhood.

When people are crowded together, as in army camps, and
insufficient care is exercised to keep flies from access to the food-
stuffs, the transportation of intestinal diseases is appalling and
the death rate enormous. This was sadly illustrated in some
of the army camps of our Spanish-American War. The best
way to prevent dysentery is to prevent the larve of flies from
developing in the filth of the camps, and secondarily the adult
flies must be prevented from coming in contact with our
bodies and our food.

The larve of Diptera may be exterminated by treating their
breeding-places with insecticides, of which kerosene oil is one
of the best. The adults may be kept away by screening the
doors and windows.

Although so very numerous, flies would be still greater pests
if it were not for the fact that they are preyed upon by various
parasitic animals and plants. The larva of the house-fly
is sometimes infested by minute parasites belonging to the
insect group of Hymenoptera. <A still more important foe is
a minute fungus which infests house-flies in the autumn. The
dead flies may often be seen on window-panes with fine white
threads sticking out of the body, and surrounded by a halo
made up of the spores discharged from the fungus upon the
glass. Finally, robber-flies and spiders kill great numbers.

The order Diptera is a large one and a difficult one to study,
for it contains many species frequently composed of small indi-
viduals which are comparatively unknown. The members of

80 ZOOLOGY

the group can usually be distinguished by having only two
wings, the posterior pair being rudimentary and transformed
into “ balancers’”’ that end in knobs. An account of the prin-
cipal families follows.

The short-horned Diptera (Brachycera!) is the division to
which the house-fly, as well as various other common flies,
belong. House-flies? (Muscidee) are of several species. In
the commonest species the female lays one or two hundred eggs.
These, in warm weather, hatch in a few hours into larve,
commonly called “maggots.”” The larve are wholly foot-
less, and even the head is only a slightly developed structure.
The larve acquire full size in about a week ; pupate and hatch
about a week later. The process of pupation is a complicated
one, for all the larval organs, excepting certain patches of
tissue, are destroyed. By the growth of these patches the
individual is formed anew. These changes are all deep lying,
and nothing seems more passive than the brown pupal case.
Finally the case breaks at one end, and the fully formed fly
emerges. The metamorphosis which the fly has just under-
gone is a complete one.

The larve as well as the adult flies breathe, like other insects,
by means of a system of air-tubes (trachez) which can be
seen best in some aquatic larve with the aid of a strong mag-
nifying-glass. The virtue of kerosene oil in killing larval flies
is due to the fact that larve cannot breathe through the film
of oil.

One of the most destructive members of the family Muscidee
is the tsetse-fly of tropical Africa (Fig. 84). The bite of this

lbrachys, short; keras, a horn.
2Tt has been suggested that these should be called ‘typhoid flies” or
“septic flies,” to make familiar the danger that lurks in them.

THE FLY 81

fly is so dangerous that horses and dogs cannot penetrate the
region infested by it. Even herds of cattle may be killed by
this fly. Consequently travellers have been hindered in
penetrating into this country, and the opening up of tropical
Africa to agriculture and commerce has been much interfered
with. The injurious effect of the bite of this fly is due to a

Fic. 84.— Glossina moristans, the tsetse-fly. Fie. 84a.—Syrphus.
From the ‘‘ Standard Natural History.” From Packard.

parasite introduced by it into the body of the victim, and caus-

ce ”

sleeping sickness.
Another destructive family includes the bot-flies, which

ing the disease known as

have a general resemblance to honey-bees or bumblebees.
Their larvee are parasitic in mammals. Of this family the
bot-fly of the horse is the most generally known. These flies
hover about the legs of horses and lay their eggs upon the
horse’s hair. The larve, irritating the horse’s skin, are licked
by the horse into its mouth and swallowed. In the stomach or
intestine of the horse they get abundant food, and there they
develop. The larve of another species, ‘‘ the ox-warble ”

ifs »

or “ grubs,” are taken into the mouth of cattle, and live for
a time in the gullet. Then they bore their way through the

G

82 ZOOLOGY

walls of this tube, and travel on until they make their way out
through the skin to the surface. Another injurious species is

the sheep bot-fly, whose larve cause ‘‘staggers”’

in sheep.
The flower-flies (Syrphidz!), like the bot-flies, mimic honey-
bees, bumblebees, and wasps. The adults feed on the pollen
and nectar of flowers, and even imitate the
humming of the bee. The larve of some
forms feed upon plant-lice ; others, upon de-
caying vegetable matter. They may occupy
the nests of various stinging Hymenoptera.
The larve of some species are known as rat-
tailed maggots on account of their having

a characteristic appendage. These are some-
i ae times found floating in foul water or even in
Photo. by W.H. salt water (Fig. 84 a).
a The robber-flies are usually of large size,
have a short head, prominent eyes, legs covered with stiff hairs,
and abdomen either long and slender (Fig. 85) or stout.
These flies attack and devour other flies and even insects much
larger than themselves, such as bumblebees and dragon-flies.

The horse-flies include the largest flies, and those whose
bite is the most painful (Figs. 86, 87). The female sucks the
blood of various short-haired domestic animals, especially of
horses and cattle. The male, however, feeds on flowers. The
larvie are carnivorous and live in the earth or water.

The long-horned flies (Nematocera) have generally slen-
der bodies and long antenne composed of six or more joints.
The larve are frequently aquatic or infest plant tissues, but
are not parasitic upon animals. To this suborder belong the
black-flies, gall-gnats, mosquitoes, and crane-flies.

? syrphos, a Greek name for a gnat.

THE FLY 83

The black-flies are familiar pests in the forests of our North-
ern country. The females, which alone suck blood, occur in
such numbers and are so active that they render certain places

Fig. 86.— Tabanus lineola, white- Fic. 87.—Chrysops, banded horse-
lined horse-fly. x 1.2. Photo. by fly. =< 1.5. Photo. by W.H.C.P.
W. H.C. P.

almost uninhabitable to man. Their bite often produces
wide-spreading and painful inflammation, accompanied by
swelling (Fig. 88). The larve are aquatic. The Southern
black-fly or “ buffalo-gnat ’’ sometimes
causes the death of domestic animals.
The gall-gnats are minute flies which
lay eggs on plants. The larvee make their
way into the plant tissue, and cause the
further development of the tissue to he
abnormal, so that excrescences or galls are Fic. 88. — Simulium,

the black-fly. En-
produced. The galls are formed only in Jarged. | From

Packard.

Fe. 7

growing tissue such as the tips of branches,
buds of flowers or growing leaves, and are less striking on the
whole than the galls of Hemiptera (Fig. 89). A certain kind
of gall-fly, called Hessian-fly (Fig. 90), is extremely injurious
to wheat because it infests wheat seedlings and so weakens
them that they produce no grain. Other minute gnats or
midges are destructive to clover in the United States, either

84 ZOOLOGY

by binding the leaves together and sucking the sap of the plant
or by destroying the young seed.

The mosquitoes, or Culicide,! are so well known that it is
hardly necessary to describe them. The larve are aquatic.

Fig. 89.— Plant galls produced by Hemiptera and Diptera. 1. Pine-apple gall
on twigs of the spruce fir produced by the spruce-gall Aphis (Chermes abretis,
one of the Hemiptera). 2. Covering gall on the petiole of the pyramidal
poplar (Populus pyramidalis), produced by Pemphigus bursarius, one of
the Hemiptera. 3. Covering galls on an ash Jeaf (Frarinus excelsior), pro-
duced by Diplosis botularia (Diptera). 4. Covering gall an Pistacia (Pistacia
lentiscus), produced by Pemphigus cornicularius. 5. Solid galls on the cortex
of Duvana longifolia, produced by Cecidoses eremile (Hemiptera). 6. Lon-
gitudinal section of one of these galls. 7. Capsule galls on the leaf of the
turkey oak (Quercus cerris, Hemiptera), produced by Cecidomyia cerris.
8. One of these galls cut through, with the operculum still firmly attached.
9. The same, with the operculum falling away; 3. The remaining figures
natural size. From Kerner, ‘‘ Pflanzen Leben.”

1 Culex was Pliny’s name for fly.

THE FLY 85

The eggs are laid in a boat-shaped mass, which floats on the
surface of the water. The larvze escape from the lower ends
of the egg-cases, and are known
as “wigglers.”’ The larve of
some species rest vertically near
the surface of the water, head
downward, with the tail end of the
body at the surface of the water,
since respiration takes place at
that end (Fig. 91, A,c); other
species lie horizontal at the sur-
face of the water. Upon emere> Fia. 90.— Cecidomyia, the Hessian-
ing from the water, the mosquito fly. a, larva; b, pupa. From
Hoste aah oes pupal slit: mk. tis the ‘‘ Standard Natural History.”
legs and wings harden. Since a disturbance in the water at
this time would jeopardize
the life of the mosquito, this
insect always breeds in quiet
waters (Fig. 92). From the
habits of the larve it follows
that they can be easily killed

while in the pond by pour-
ing kerosene oil on the
water, for this forms a film

Fic. 91.— Culex, the mosquito. A, larva;
c, its respiratory tube. B, pupa; d, the
respiratory tubes; a, the end of the on the surface and prevents
abdomen with the two oar-like swim- : 5 a ‘ll
ming appendages, dorsal view. After respiration. Minnows wi
drawing of E. Burgess. free a pond from larve if the

edges of the pond are kept free from grass so as to allow the

fish to get to them.
Mosquitoes are not merely a nuisance, but are disseminators

of some of the most dangerous of human diseases. Malaria

86 ZOOLOGY

is due to germs of microscopic organisms that live in the
salivary glands of some kinds of mosquitoes (Anopheles) and
are injected into the blood of its victim at the time of biting.
The mosquito gets the malaria germs from the blood of infected
persons. Another genus (Stegomyia) found in the tropics dis-
seminates the germs of yellow fever. Still another species

Fia. 92.— A quiet water where mosquitoes breed.

conveys about a minute round worm, Filaria! hominis, allied to
the vinegar eel, which thrives as a parasite in the blood-vessels
of men living in the tropics, and causes a painful and usually
fatal swelling of the arms and legs. The embryos are found
in the surface circulation only at night, during which time man
is most defenceless toward the mosquito. At this time they
are sucked out of the blood by the mosquito and develop in
its alimentary tract. Later they are deposited in stagnant

1 fiium, thread. 2of man.

THE FLY 87

water with the eggs of the mosquito, and reach man’s body
again if the water be drunk by him.

The crane-flies (Tipulide,! Fig. 93) look like mosquitoes,
but can easily be distinguished from them by the fact that
they have a V-shaped groove on the back of the thorax. They
are larger, and have relatively longer legs than the mosquito.
Their legs are easily broken, and seem to be so much in the

Fia. 93.— A crane-fly. Nat. size. Photo. by W. H.C. P.

way that flight is clumsy. The adults are quite harmless, but
some of the larve work destruction by feeding upon tender
plants and causing them to wither and die.

There remain to be considered a number of degenerate flies —
degenerate because parasitic in the adult state. The first
family we may consider is that of the louse-flies.2 These
small insects have a firm proboscis used for piercing, and stout
legs. Only certain of the genera develop wings, and some of
these lose them after they gain their hosts. They live, like
lice, in the fur of mammals or the feathers of birds. They

1Latin, tipula, water-spider. 2 Suborder Pupipara.

8S ZOOLOGY

are viviparous, the larve being ready to pupate at the time
of birth. The sheep-tick is one of the best-known forms.
Diptera allied to the foregoing live as parasites on the body
of the honey-bee.

Fleas are likewise wingless, blood-sucking parasites. The
body is compressed from side to side, so that it can move easily
amongst the hairs of its host. The hindermost legs are strongest
and are used in springing. Fleas develop in dust in the cracks
of the floor and about the sleeping-places of domestic pets.
One species prefers mankind and is believed to disseminate
certain diseases such as the bubonic plague. They may be
combated by means of cleanliness and Persian insect powder.

The foregoing study of the Diptera shows how great a men-
ace they are to man’s health. But indirectly they are inju-
rious to man by attacking domestic animals and cultivated
plants. Thus the tsetse-fly is a menace to the commerce of a
large part of a continent. The horse-fly, the horn-fly, which
worries cattle, the buffalo-gnat, which worries or even kills
domestic animals, and the dangerous bot-fly are all causes
of great loss to industry. Also the larve of some flies infest
vegetables, such as cabbage, radish, cauliflower, onion,
as well as various fruits, and cause great damage. The
gall-enats destroy clover and its seed; and, worst of all, the
Hessian-fly infests wheat and Indian corn. This last-named
scourge, so called because of a tradition that it was imported
in the straw bedding of the troop-ships which brought over the
Hessian mercenaries in 1775, has spread, within a century,
over the eastern half of the United States, and has at various
times injured the wheat crop to the value of millions of dollars.
The larve of certain Muscidz! attack, in Europe, the stems,

1 Of the genus Chlorops.

THE FLY 89

leaves, and ears of wheat, rye, and barley, and cause in some
years great destruction, especially in Scandinavia.

Over against the injury wrought by the Diptera may be
placed certain benefits bestowed by them. In the first rank
come certain species which prey upon injurious insects, either
in the larval or adult stage. The robber-flies prey on the Dip-
tera, Hymenoptera, and certain beetles, but they are not care-
ful to choose alone injurious species. The larve of the Syr-
phide prey on the injurious plant-lice ; those of horse-flies are
carnivorous, and feed on insect larva. The larvee of certain
small flies are internal parasites of bugs, beetles, and other
(mostly injurious) insects. Finally, the larve of some crane-
flies, robber-flies, and Syrphidx, by boring into rotten wood,
help in the work of forming forest mold. The Diptera, like
almost every other insect group, has its economically injurious
and beneficial species. However, the good that they do is so
small in comparison with the destruction that they directly
cause to animals and plants by worrying or feeding upon them
or by bringing to them various noxious and fatal diseases
that, on the whole, the world would be a better place to live
in if there were no Diptera.

CHAPTER VI
LITHOBIUS
A STUDY OF LIGHT-SHUNNERS

Man is a diurnal animal, loving the sunlight. The animals
that we know best are those that are active in the daytime
since we ourselves are most active at that time. But many

Fia. 94.— A colony of light-shunners under an upturned stone. From above
downward in the figure, an earthworm, a short-winged beetle, a Julus, an
ant with pups, and a carabid beetle.

classes of animals are entirely nocturnal. This is true because
their organization is such that a strong light is disagreeable
to them. They shun a strong intensity of light, and so in the

daytime are found hidden under stones (Fig. 94) or the bark
90

LITHOBIUS 91

of trees (Fig. 94 a), in deep woods or in caves. If one of these
light-shunners is placed on a table near a window, through
which the sunlight is falling, it will turn tail to the sun and
move away from the window. If one goes out at night with
a lantern, however, one will find many animals running about
on the surface of the ground seeking for food or for their mates.
Many light-shunners, such as those that live in caves, remain

Fic. 94a.— A colony of light-shunners on the under side of an upturned piece
of wood. From left to right, Armidillidium, Oniscus, Helix, and Lithobius.

there during their entire life, never experiencing rays of natural
light. They get into the caves in the first place because they are
light-shunners and because their organization fits them to live in
the dark. Like most light-shunners, cave animals love not only
darkness but contact and moisture as well; all of these con-
ditions they find in caves, particularly in damp crevices and
corners. Very many close relatives of cave animals are to be
found outside of caves in greenhouses, secreted under boards
during the daytime, just because they find in greenhouses the
conditions of equable temperature, moisture, and contact
which their nature demands,

92 ZOOLOGY

The principal large cave animals are various bats, which are
found clinging to the walls ; a few salamanders, allied to our
little red salamander of the woods (Fig. 95); and certain fishes,
many of which are blind. A number of insects live in caves.

(22 The commonest are two or three kinds of

& yee small beetles that live under stones and a

4. few flies that live in decaying matter; a

ee cricket-grasshopper, already referred to on

ee Dae page 20; a little ‘‘spring-tail,” the minute

fod ne vei a insect which swarms on the damp rocks.

ie \* There are also a few myriapods, which we

! ioe L shall study further in this chapter; some

ie spiders; a blind cray fish, which lives in the

hy, streams that usually flow through caves;

ete - and a few smaller crustaceous animals.

es aN Each of these groups is more fully con-
ee a4 ®) sidered in the following paragraphs.

oe z The bats, of which about 500 species from

ee all parts of the globe are known, constitute

“an one of the most specialized groups of Mam-

Xo mals. They are able to

Pel n= fly, owing to the great

5 aes

~___ elongation of their fin-
Fie. 95.— Adult of Spelerpes maculicaudus, gers and to a delicate

the-give aalercipnider: membrane stretched he-
tween them. They fly almost exclusively at night or toward
dusk ; and they seem to be guided less by their eyes than by
the vast number of delicate organs of touch that are scattered
over the wing membrane. Also the tip of the nose is crowded
with touch organs, which are often borne on a fantastically

folded membrane. The outer ears are usually very large,

LITHOBIUS 93,

indicating an acute sense of hearing. These peculiarities
are special adaptations to a nocturnal life in which other
senses replace that of sight. During the daytime bats lie
hidden in hollow trees, crevices of rocks, in caves, and behind
window blinds of houses. Little explanation can be given
for their peculiar relation to light; it does not seem to be an
adaptation to feeding on nocturnal animals, for many bats
are frugivorous. Doubtless they gain from their nocturnal
habits a certain immunity from attack by hawks and other
birds of prey. The most primitive of the living bats fly late
in the day. As the group evolved the habit of flying at night
was subsequently acquired, and this suggests that bats have
been getting more and more sensitive to light. In caves, bats
fly back and forth but pass often into the free air to capture
flying insects. Then, before dawn breaks, they return to the
darkness of the cave.

The commonest salamander that inhabits our caves belongs
to the species Spelerpes maculicaudus. This genus is wide-
spread, being known from New England to Minnesota and
into the Southern States. In New England, where there are no
caves, it lives among the rocks and, like its relatives of the
same genus, prefers moist crevices and lies concealed during
the day. Wherever there are caves, as in Indiana and Ken-
tucky, this salamander is found inhabiting them in great num-
bers, just because the caves offer the conditions to which they
are adapted. The eyes of this salamander are functional, but
there are other, less common, cave salamanders whose eyes
are degenerating.

The cave fishes of the United States all belong to one family.!
Those members of the family that live in caves have a

1The Amblyop’side (Fig. 95a).

94 ZOOLOGY

colorless body and eyes that are rudimentary or concealed
beneath the skin. Their behavior has been thus described:
“ Tf these Amblyopses be not alarmed, they come to the surface
to feed, and swim in full sight, like white aquatic ghosts.
They are then easily taken by the hand or net, if perfect
silence is preserved, for they are unconscious of an enemy
except through the medium of hearing; this sense, however,
is evidently very acute, for at any noise they turn suddenly
downwards, and hide beneath stones, etc., on the bottom ”
(Cope). There is, however, reason for thinking that their

Fic. 95 a.— Amblyopsis, the cave blind-fish, from Blatchley : ‘‘ Glean-
ings from Nature.”

tactile sense is acute, for the head is provided with numerous
tactile warts. These fishes spend their whole life in the caves,
never seeing the light of day, and the question arises, whence
did they come, how did they get into the caves, and why are
they blind? As to the first question it is certain that they must
have come from surface streams, because all their numerous
close relatives still live above ground. To learn how the blind
fishes got into caves we must study their relatives above ground,
and we shall find that some inhabit dense swamps and others
occur under stones in springs. The whole family of Ambly-
opsidze are light-shunners and, being such, a cave has offered
the best possible place for one of this family. As to why they
are blind it appears that it is not due to their cave life, since
some of the relatives above ground in regions where there are

LITHOBIUS 95

no caves have degenerating eyes. One may say that Ambly-
opsis came to inhabit caves because it was going blind rather
than that it became blind because it got into a cave. ‘

Of the cave beetles one belongs to the genus Quedius. It
is found not so far within the cave but that a dim light reaches
it. The adults are not wholly blind. It feeds on excrement
or decaying remains of cave animals. Now Quedius is a
large genus of the family of Staphylinide (page 66), most of the
members of which are scavengers. As Quedius
above ground is usually to be found under or
embedded in decaying matter where it is in the
dark, it involves no change of habits to be
a scavenger of the caves. Another beetle —
Anophthalmus '— has gone further ; it is found
at the darkest part of the cave and is wholly
blind. It belongs to the family of Carabide
(page 64) which are predaceous beetles that ae ee ae
hunt chiefly at night. Anophthalmus may hunt — from __Blateh-

é sakae 5 ley: ‘‘Glean-

all day and all night, for it livesin eternal dark- ings from
ness, and can get a supply, although all too Nature.”
scanty, of living prey such as spiders, mites, and springtails.

The flies are among the most abundant of the inhabitants
of caves. The commonest species are short-horns, which
congregate in moist places on the walls and are exceedingly
sluggish in their movements. Their larve live in the excre-
ment of the larger animals or in carcasses. Outside of caves
these flies are found under wood or stones.

The cave crickets belong to the genus Ceuthophilus (page
20). Their sight is defective, but they are sensitive to touch.
Since the other members of the genus that live above ground

1Fig. 96.

96 ZOOLOGY

hide during the day, it is easy to understand that the cave
affords a favorable environment for such a light-shunning
species.

The springtails, some of which live in caves, are among the
smallest and simplest of insects, and perhaps the most numer-
ous in individuals (Fig. 97). On a single bare beach one-fourth
of a mile long the number of springtails living
between high and low tide has been estimated
at 100,000,000. The group as a whole loves
moisture. They also love contact, so one sees
them burrowing into the sand. They are
seen to be most numerous at night; they
shun the light. Finally, they feed on any
organic débris. This is evidently a group
that is fitted to live in caves, and so the
springtails are found in the caves of both

Fic. 97.-A spring- America and Europe. Some of them in the

tail. (From Parker ¢ayves are blind and colorless. But this con-

and Haswell’s

Text-book of dition is not to be attributed only to the

veolcey) absence of light, for some of the allies of the
cave springtails that live above ground are colorless and blind.
Also some of the individuals of one species, at least, live above
ground, while other individuals live in caves. Both sets shun
the light of day; but it is only certain fortunate individuals
that have got into caves.

Most of the spiders that live in caves are related to those
that build cobwebs in our cellars and barns. It is easy for
such lovers of darkness and moisture to find a suitable home
in caves. But the cave species live under stones and make
only a few strands of web. They seem to feed on the larger
springtails.

LITHOBIUS 97

Finally, the blind crayfish deserves a further word besides
the brief reference in Chapter VIII. Most boys know that
all crayfishes love the darker parts of streams, and when placed
in strong light, they act as though it were painful to them.
As they live in streams they would, in cavernous countries,
often be brought to the point where a stream issues from a
cave. The darkness of the cave would be a lure to them.
Consequently some of them in time would come to be perma-
nent inhabitants of it. The loss of sight and pigment would
follow.

Thus we see, in general, that the fauna of caves is not an
accidental one, nor one made up of accidentally associated
animals. It is a society of light-shunners. They are lucky
to have a cave to live in.

Lithobius belongs to the group Myriapoda,! which is closely
allied to insects, but is characterized by life in dark, moist
places. The Myriapoda differ from most insects in being
wingless and in having the body divided into two regions,
head and trunk, and in having either one or two pairs of legs
on each segment of the trunk, so that there are, all together,
many pairs of legs instead of only three as in insects.

There are two principal groups of Myriapoda, the Centipedes
and the Millipedes. The Centipedes (Chilop’oda ), to which
group Lithobius belongs, have only one pair of appendages
to each body segment. They are active and ferocious animals.
All are terrestrial and live chiefly under stones and bark, within
or under decaving wood, among barn-yard refuse, in loose
soil, and under fallen leaves. Chilopods feed upon living

1 myrios, very many; pous, foot.
2 More correctly Cheilopoda, from cheilos, lip, and pous, foot; because
the mouth parts (modified feet) are partially united to form a sort of lip.
H

98 ZOOLOGY

insects, mollusks, and worms, and may be useful to agriculture
through the destruction of injurious insects. Lithobius has
been observed to spend hours in killing an earthworm, whose
juices it sucked as food. _Bluebottle flies also serve it as food
while in confinement.

Litho’bius! is of world-wide distribution, and over one
hundred species are recognized. Our common straw-colored,

Fic. 98.— A piece of upturned bark with a colony of light-shunners, — Litho-
bius, a sow bug, a pill bug, and a small snail.

Eastern species, Lithobius forficatus? (Fig. 98), is found also in
South America, as well as over most of Europe. It seems
to be replaced south of Virginia by another species, spinipes.
Scutig’era *is easily distinguished by its long legs; its hind
legs, indeed, are longer than its trunk (Fig. 99). Our common
Iastern species (rare north of New York City) is about 25
centimetres long, and is of a light brown color, with stripes on
the back. It is very active, and feeds especially on spiders.
It looks something like a spider itself when in rapid movement.

1lithos, stone; bios, to live. 2 provided with shears, forfex.
3 scutum, shield; gerrere, to bear.

LITHOBIUS

-
SS

oes

are

oa

Pe eon tsetse

Fic. 99.—Scutigera. Nat. size.
From Wood.

99

The Scutigeras are characteristic

_of the tropics, where they live

preferably in cellars, crawling up

horizontal walls.

Scol’opendra! includes longer

and stouter myriapods than Litho-

bius (Fig. 100).

belong the poison-
ous centipedes of
tropical countries.
Among these is the
giant Scolopendra
of our Southern
States, South
America, and the
West Indies, which
reaches a length of
25 centimetres or
more. This ani-
mal has a poison-
ous bite, which is
fatal to insects and
other small ani-

mals, and causes painful and even dangerous
wounds uponman. The biting apparatus is the
first pair of feet, modified to form sharp hooks,
and provided with poison-glands, which open

near the apex of the claw.

According to Hum-

boldt, the Indian children of South America tear
off the heads of large centipedes and eat the remaining portions.

1 Greek name for milliped.

To this genus

Fic. 100. — Scolo-
pendra. Nat.
size. From
Leunis.

100 ZOOLOGY

Geoph’ilus' includes relatively slow-moving species, often
attaining great length, having up to two hundred segments to
the trunk (Fig. 101). The species are common in
Europe and America. They live mostly under
stones. There is a European species, Geophilus
electricus, which is phosphorescent and shines
in the dark like a glow-fly.

The Millipedes, or Diplopoda, have, as the
name implies, two pairs of legs to each segment
of the trunk. They are usually more or less
cylindrical animals. The antenne are rather
short, and the jaws, which are somewhat shorter

than the centipede’s, lack the poison-glands of

nie eee that group. Accordingly we find the millipedes

ophilus mor- feeding not upon animal but upon vegetable
dav. Nat.
size. Photo.
by W.H.C.P. parts are well adapted. The following millipedes

substances, for the chewing of which their mouth

representing two families, can be found under boards in almost
any greenhouse.

Julus is commonly known as the galley-worm (Fig. 102).
The members of this genus crawl rather .
slowly, and when at rest coil the body. .
When disturbed, they give out a strong
odor through lateral openings of the body.
They feed on dead snails and earthworms ; p,4. 102. — ulus eana-
some species, on ears of Indian corn or — densis. Nat. size.
: ‘ ian Photo. by W.H.C.P.
strawberries. Their eggs are laid in holes
in the ground in the spring; consequently they may be easily
dug up at this season.

Pol’ydesmus ” includes somewhat flattened species, which,

1ge, the earth ; phileo, to love. 2 polys, much; desmos, band.

LITHOBIUS 101

when disturbed, roll up spirally. P. canadensis, of the northern
United States, is deep brown, with hairy antennze (Fig. 103).
These myriapods are destructive to agri-
culture, especially to cabbage and straw-
berries.

Two genera of myriapods which stand
somewhat isolated deserve a passing
notice. Pau’ropus! and allied genera
include a few animals, about 1 millimetre
long, found on the moist loam of woods.
They are intermediate between chilopods
and diplopods, inasmuch as they have only
one pair of legs to a segment, but the er
segments tend to unite in pairs. Scol’open- ee AE - i alae
drella? is a small, white species, having tus). » 1.5. Photo. by
very large antenne and a pair of back- WADE Sey
ward-directed stylets. The mouth parts are very much like
those of the lowest insects, so that Scolopendrella bridges the
gap between myriapods and true insects. The presence of
these connecting species indicates that the groups that are now
separated are of common origin.

rgd
mat
ae
a

CO ANNAN ANN ARNG FANN NAN
Ce ae ii is cenaneor

E?

aa

Fic. 104. — Peripatus, the air-breathing, wormlike animal that bridges the
gap between Myriapods and worms.

Finally, the myriapods seem to be connected with the
worms by a peculiar air-breathing tropical animal known
as Perip’atus (Fig. 104). In many details of structure this
resembles a polychaetous worm (Chapter XI).

1 pauros, small; pous, foot. 2 Diminutive of Scolopendra.

CHAPTER VII

THE SPIDER— A STUDY OF ANIMAL ARCHI-
TECTURE

Mosr plants are rooted to the soil, while most animals are
free to move from place to place. Nevertheless many species
of animals, particularly the higher ones, have some place to
which they repeatedly return and which may be called their
Home. This home is usually the place which serves to rear
the young and to shelter both them and their parents.
The simplest sort of a house consists of a lot of agglutinated
particles of sand enveloping the body of the animal. Within
this sand-tube the eggs may be laid. Such a tube of sand is
constructed by many worms (page 188). Certain mollusks,
which are protected by hard shells, make burrows in rocks
in which they pass a part of their lives. When these mollusks
are very numerous (page 230), the rocks may be quite honey-
combed by their burrows. Many of the higher crustaceans
form more or less permanent burrows in the sea bottom, where
they may dwell and protect their eggs during the breeding
period. All of these sorts of homes, however, are very simple
architecturally compared with those of some insects, spiders,
and vertebrates.

Certain burrowing insects, like the termites (page 26) and
ants (page 53), build complicated communal homes within
the earth. Others, like the wasps (page 51) and bees (page
49), construct nurseries of mud, paper, or wax. In the group

of spiders complicated structures have been developed, less for
102

THE SPIDER 103

the purpose of protecting the young or forming a communal
home than for the purpose of entrapping prey. The forms of
webs invented by spiders are very numerous and their study
is full of interest. We shall consider them further on, after we
have learned something of their structure (Fig. 105).

In the vertebrates the simplest homes are those made by

Fig. 105.— Web of Tetragnatha, placed horizontally over a fish-way. Photo.
by W. HAAG. P.
fishes. These may be merely piles of pebbles to cover the eggs
or they may rise to the complexity of nests woven of plant
fibre, as in the case of the sticklebacks (Fig. 315). The compli-
cated nests built by birds, for the purpose of rearing their
young, reach their highest’ expression in our Baltimore
oriole and in the tailor bird of Australia. Finally among
the mammals we find examples of animals that burrow
like the wood rat of the Great Basin; that build houses

104 ZOOLOGY

of sticks, like the muskrat and beaver; that build nests
in trees, like the squirrel; and that rear houses of skins,
thatch, brick, stone, and wood, like man.

Fic. 106.— Mygale, a tunnel-weaver, allied to the ‘‘ trap-door spider.”
Nat. size.

In the present chapter we shall consider a group of Arthro-
pods, in which some sort of architecture is nearly universal.
This is the group of Spiders (Araneina). They are charac-
terized by the fact that the head and thorax are united in
one piece, called the cephalo-thoraz. The abdomen is con-
nected with the cephalo-thorax by a stalk and bears the spin-
ning organs (called spinnerets) at its hinder end (Fig. 106).

THE SPIDER 105

Compound eyes and antennz are absent, and so we see that
spiders are very unlike insects. The first pair of mouth
appendages are called chelt’cere and end in claws, at whose
apices the poison-glands open to the exterior. The second
pair of mouth parts, called pedipalps, are long and seem to
take the place of antenne. Near the stalk of the abdomen
on the ventral side is a pair of slits
which open into two lung sacs. In
a few spiders there is a second pair

of slits; such spiders have four
lung sacs.

All spiders spin a nest, but all do
not spin webs. The large webs
that attract our notice are the per-
fected product in the evolution
of spinning. The most primitive
spiders appear to be those that A aa nes ara
burrow in the earth and line their mon grass spider. Nat. size.
tubes with silk. Such spiders are Photo: by W. H.C. P.
known as tunnel-weavers. They are found in our Southwest-

ern States and are commonly known as trap-door spiders. The
lid of the tube or tunnel is made of dry clay and is penetrated
through and through by the spun silk. When the lid is closed, it
looks exactly like the ground around it, so that the opening is easily
overlooked. Some of these spiders acquire great size (Fig. 106).

A step in advance is seen in the tube-weavers (Fig. 107).
The tube-weavers spin in the grass their tubes of silk, at the
bottom of which they live, while at the outer end they build
over the grass a platform, which serves them mainly as a trap
for jumping insects. Such are the webs that one sees in the
grass on a dewy morning (Fig. 108).

106 ZOOLOGY

Next we have certain spiders which build irregular webs.
Such are the line-weavers. To this group belong the common
cobweb spiders of our cellars and outhouses. The web consists
of a fine irregular mesh with strands running above and below
it in various directions. The spider stands below the main part

Fie. 108.— Web of a tube-weaver Tegenaria; looking down upon the web,
which is in a corner between two vertical walls. The tube is in the angle.
Photo. by W. H. C. P.

of the web, hanging back downward. Such a web serves to

entangle and hold flying insects upon which the spider preys

(Figs. 109, 109 a).

Finally the orb-weavers (Orbitelariz') spin a web lying
mostly in one plane and having a geometric form often of re-
markable perfection and symmetry. Such extraordinary struc-
tures deserve careful attention. Foundation lines (Fig. 110) of
unusual strength are first laid down to form the outer frame

lorbis, circle; tela, web.

THE SPIDER 107

of the web. Then radii are spun from a central little ball of
floss to the frame. The radii are, often at least, laid down
alternately on opposite sides of the centre. The number of radii
formed by a species of spider is not perfectly constant, but

Fria. 109.— Web of a line-weaver. Photo. by Emerton.

varies within limits. It would be an interesting occupation
to sketch a number of webs of Argiope, showing the variations
in the number of radii and the other details of form. After the
radii are placed, the spiral lines are laid down. In the com-
pleted web four regions are distinguishable, as follows, passing
from the centre outward: (1) the inner spiral zone, consisting
of four to eight turns at the centre; (2) the free zone inwhich

108 ZOOLOGY

no spiral is laid down; (3) the outer spiral, the main part of
the spiral framework; (4) the foundation space, beyond the
spiral lines, and at the outer margin of the web (Fig. 111).
No study is more interesting than that of the details of

Nu

5

Fic. 109a.— Web of Linyphia, one of the cobweb spinners, in a spruce tree.
Photo. by Emerton.

construction of these parts of the spider-web, while they are

being made out of doors or in large glass jars.

The web of the orb-weaver has undergone, in different species,
very striking modifications. Thus, in some cases only frag-
ments, asit were, of an orb are built (Fig. 112). In one case
the spider lives in a recess behind the web and keeps in touch
with the web by means of a line running to its centre. By pull-
ing upon this line the centre is drawn back towards the

THE SPIDER 109

spider. If an insect should enter the web, the spider releases
its pull upon the central part, and the web springs out-
ward, strikes the insect, and causes it to adhere to the
threads.

While, on the one hand, some spiders have evolved in the
direction of the construction of complicated webs, some, on
the other hand, have never ac-
quired the web-spinning habit.
Such, for example, are the wander-
ing spiders, which may be classi-
fied into three chief groups.

(1) Crab spiders are so called
because they run sideways. They
make nests by fastening together
leaves by threads of silk. Their
young are reared in these nests,

and watched over by the mother
Fra. 110.— Diagram on nomencla-

(Fig. 113). ture of partsof anorb-web. FS,
(2) Running Spiders.— These foundation space; SS, spiral
: space; CS, central space; FZ,
are for the most part large and _ freezone; NZ, notched zone ; H,
powerful species which wander entte- From MeCook.
over fields or along watercourses in search of prey. Our North-
ern species are chiefly “wolf spiders” (Lycoside,’ Fig. 114).
The female carries her eggs about in a special cocoon attached to
the end of the abdomen. The young are borne on the back
of the mother. The great size, black color, and hairiness of
some of these spiders have given them an apparently unjusti-
fied reputation of being very poisonous. Naturalists who have
allowed these spiders to bite the hand report that the bite is

rarely more poisonous than that of the mosquito. Some of

1 lykos, wolf,

110 ZOOLOGY

the Lycoside live on sandy wastes (Fig. 115), where they make
holes in the ground lined with silk (Fig. 116).

(3) Jumping Spiders (At’tide!).— This family includes
many familiar, active species of high intelligence. Some of

Fic. 111.— Orb-web of Epeira. a, first spiral line ; b, second spiral line ;
c, line to nest. From Emerton.

these of grayish color live in houses, and are recognized as mem-
bers of this family by their half-running, half-jumping gait
(Fig. 117). The cocoon is attached to some object and enclosed
in a sort of tent, in which the mother also lives to guard the
young.

Other Uses of the Spinning Instinct. We have seen that

1 rom Latin, Aéta, club-footed man.

THE SPIDER 111

spiders make webs of the silk that they spin and that many
ground spiders line their nests with silk. Silk is, however, used
for many other purposes, and it would be difficult to say
which is the principal use. The mass of eggs that the female
lays is always covered by a
cocoon of silk. The silky
threads may serve also to
suspend the spider while it
drops from a tree, or they
may, by their friction with
the air, serve to suspend cer-
tain spiders in aerial migra-
tions.!. This latter use is es-
pecially noteworthy. A small
spider, when desirous of tak- |,
ing flight, climbs up some |W

high object, such as a fence Fre. 112.— Web of Hyptiotes in a
bush, one quarter of the real di-
ameter.

post, elevates the spinnerets,
and spins loose silk into the
air (Fig. 118). After enough of it has been thus formed, the
spider lets go, and is supported by the currents in the air
while it is wafted great distances. Thus Darwin, on his
voyage in the Beagle, saw cobwebs bearing up spiders floating
in the air over his vessel more than sixty miles from shore.

1 The ballooning habit of spiders has been noticed since early times, but
it was formerly misinterpreted. Thus Pliny speaks of wool being rained.
The poet Spenser wrote : —

“ More subtle web Arachne cannot spin;
Nor the fine nets, which oft we woven see,
Of scorched dew, do not in th’ ayre more lightly flee.”

Thompson writes:

“ How still the breeze! save what the filmy threads
Of dew evaporate brushes from the plain.”

112 ZOOLOGY

The method of spinning deserves careful attention. The
spinning-organs consist of a set of glands lying in the hinder
part of the abdomen, and opening to the exterior through
a number — often several hundred — of spinning “ spools.”
These spools are the modi-
fied mouths of glands, and
are grouped upon and be-
tween tubercles called spin-
nerets. The secretions of
the glands, as they are poured
out into the air, fuse together
and harden into a thread.
The thickness of the thread
is determined by the number
of glands secreting together.

The economic importance

of spider webs is consider-
Cac able. First of all, they are of

the greatest importance in
Fic. 113.—Thomisus, a crab spider. 2 |

Diagram showing arrangement of eyes capturing many destructive
at bottom of figure. From Emerton. insects, such as flies, mosqui-
toes, and moths. Another use to which they have been
put is in making silk cloth. The silk of the spider is smoother
and glossier than that of the silkworm, but it is much harder to
collect in quantity. A spool is passed against the spinnerets of
an individual spider and slowly revolved, winding the silk upon
it. The difficulty comes in rearing the spiders, for they are ex-
tremely voracious, and if the supply of flies is insufficient, they
attack and devour one another. Consequently they must be
kept isolated and fed individually, and yet vield in the end only
an ounce or so (about 30 grammes) of silk. Other uses of spiders’

THE SPIDER 113

silk are: in the construction of cross-hairs in telescopes and,
in medicine, asa narcotic in case of fevers, — a temporary fad.

Poisonous Spiders. — Spiders are feared by many people
from a belief that they are very poisonous, even fatally so.
Spiders have, indeed, biting jaws
provided with poison-glands, and
their bite is often fatal to insects
and even to small birds and mam-
mals. But most spiders cannot
spread the jaws sufficiently to make
a bite in the human skin, and even
the largest forms seem to inflict but
a slight wound, scarcely ever greater
than that of a mosquito. The
stories of the severe effects of the
bite of the Tarantula, one of the Ly- Fre. 114. — Ocyale (Pisaurina)
cosidze, are entirely fabulous. el el et aa ne

Spiders show a marked sexual using it as a sort of artificial
web. Photo. by Emerton.

dimorphism. Particularly among

the orb-weavers the males are much smaller than the females
of the same species, but the legs of the male are rela-
tively the longer and stronger. The male is usually shorter
lived than the female, for the latter has often to watch the
egg-cocoons, or carry them about with her until the
young hatch out. The male also builds less perfect. webs than
the female. The relation existing between mated pairs is
often peculiar. The male is frequently killed and eaten by the
female; but if the male can overcome the female she may
fall his victim. Among wandering spiders there is often a
selection by the female from among several rivals, which en-

gage in severe battles with each other.
I

114 ZOOLOGY

The Position of Spiders in the Zoological System. — Spiders
clearly belong to the arthropods because, like the grasshopper,
they have a thick cuticula (which is molted as the animal
erows) and jointed legs. Spiders differ from insects, however,
in several important respects. They possess four pairs of
legs instead of three. The head and thorax are united. The

Fig. 115.— A sandy waste (dune region of Fire Island Beach, Long Island)
where many spiders burrow in the sand.

antennz are absent. Consequently it is an error to speak of
spiders as insects; rather they, together with several allied
groups, belong to a distinct division of the arthropods, the
Arachnida. The Arachnida, indeed, breathe air, but the air
passes into a little pouch on the under side of the abdomen and
in between numerous thin sheets, like the leaves of a book,
so that the whole breathing apparatus is often called a lung
book. They have also a system of air-tubes which is much

THE SPIDER 115

less developed than that of insects. Although they belong
to the air-breathing arthropods they are without wings, and
are therefore confined to the surface of the ground, except in
the case of the ballooning species just described. In conse-

Fic. 116.— The entrance of the vertical tube ta the sand-Lycosa.

quence, the thorax is not a distinct and prominent part of
the body, as in insects, but is indistinguishably united with
the head. The abdomen never carries legs as does that of the
water arthropods. In this respect the Arachnida agree with
the insects rather than with the water-inhabiting crustaceans.

Although the spiders are the largest group of the Arachnida,
there are several other kinds of animals included in this class.

116 ZOOLOGY

The scorpions (Fig. 119) and their allies are more primitive
than the spiders, since their bodies are longer and more worm-
like. The abdomen is divided into two regions: in front, a
broader and, behind, a narrower called the post abdomen.
The scorpions are animals of the tropics and of the deserts,

Fic. 117.— Attus, a jumping spider. Fic. 118.— Young Lycosa about

From Emerton. to fly. From Emerton.
and are found during the day under sticks and stones. Their
thick skin enables them to resist the dry air of the desert which
tends to wither all it touches. The tip of the tail bears a
sting. Into this sting a poison sack empties. The wound of
the large scorpions, such as are found in the tropics, is fatal
to many animals upon which the scorpion preys. The wound
is very painful to man and occasionally fatal. We have only
one species of scorpion (Bu'thus) in our Southeastern States,
but there are several species in the southwest.

THE SPIDER 117

The harvestmen, or
daddy-long-legs (Phal’- ] ie

Hand

ian,

angidea) are extremely
common (Fig. 120). They
are somewhat spider-like,
but differ in having legs

Tibia | palp.
Femur
Troch.

---Cephth,

manv times the length of :
the body. Their long legs
enable them to walk over
the foliage of trees and
smaller plants by stepping 7 .
from leaf to leaf. They y, a
wander over fields also s

and not uncommonly are

Dorsal ridge. —
Luteral ridge --

Dorsal furror --

seen on porches of houses.

They are rapacious ani-

mals, feeding on small

insects, and are highly

beneficial to agriculture. Bla.
The mites and ticks jee)

(Acarina) have their ab- Fig. 119.— Buthus, a European scorpion.
domen united into one Dorsal view. Mz., maxillary; Cephth.,
‘ eh the ts cepkalo-thorax ; Troch., trochanter ; Tars.,
piece with the head and tarsus ; dbd., abdomen ; Bla., poison blad-
thorax, so that the body der ; St. sting. From Kraepelin in ‘‘ Das
a Tierreich.

is round. They exhibit

great diversity of form and habits, most being of very small
size. All are terrestrial, excepting one group of aquatic
mites (Hydrachnids). They are often of a bright red
color. The free-living species prey on smaller animals as
well as dead organic substances. Others are parasitic in

animals or plants, living in fur or feathers (Fig. 121), and

118 ZOOLOGY

Fie. 120.— Liobunum dorsatum, one of the harvestmen. The long legs are
apt to be thrown off in handling the living animal. The second left leg is
accordingly absent in this specimen. Nat. size. Photo. by W. H. C. P.

Fic. 121.—Psoroptes, the sheep scab, female. Right figure, dorsal view ;
left figure, ventral. Much enlarged. After Salmon, Bulletin 21, Bureau
Animal Industry.

THE SPIDER 119

even penetrating into the skin, as the small red
“jigger”’ or “ chigger”’ of our Southern States
does.
Finally, there lives in the sea an aberrant
family of spiders which crawl on the sea-
a . Fia. 122.— Pal-
bottom or over hydroids, and thus have for- “Jeno, a sea-
saken a terrestrial life for a completely aquatic spider. * 1.6.

. Photo. living
one (Fig. 122). by W.H.C.P.

CHAPTER VIII

THE ANATOMY AND PHYSIOLOGY OF
CRUSTACEA: THE LOBSTER

General Form of the Lobster.— The lobster closely
resembles the crayfish (Fig. 123) except it is much larger.
Like the cockroach it is approximately bilaterally symmetrical
and is segmented. We may distinguish in the body the trunk
_and the appendages. The trunk is divided into two main
regions: the abdomen and a united head and thorax (cephalo-
thorax). The segments of the abdomen are distinct like those
of the cricket, but unlike the latter each segment bears a pair
of appendages. There are seven segments in the abdomen of
the lobster. Since the segments of the cephalothorax are not
distinct, they cannot be counted directly, but by assuming that
each pair of appendages corresponds to a segment, as in the
case of the abdomen, the number of cephalothoracic segments
is estimated to be thirteen.

The appendages of the body show a diversity of form in
accordance with the various kinds of work they have to do.
At the front of the head are the two pairs of long organs of
touch — antenne; then come the stout. crushing jaws (mandi-
bles) ; next are five pairs of appendages concerned in holding the
food while it is being devoured. Then follow five pairs of walking
appendages and, on the abdomen, a number of pairs of flappers
(swimmerets), the series terminating in the great tail flappers.
As can be inferred from the structure of the appendages the

lobster can both walk over the rocks at the edge of the sea or
120

Fie. 123. — Median longitudinal section through the European crayfish show-
ing parts of body appendages and internal organs. aa, artery to antenna;
ab, abdomen ; an, anus; bd, bile duct ; bfy, great claw ; bm, ventral nerve ;
cs, stomach ; cth, cephalothorax ; em, muscles of back ; fm, muscles of ven-
tral side; g, brain; h, heart ; hd, large intestine; lr, liver ; md, small intes-
tine ; 0, opening in heart ; oa, artery to eye ; oaa, dorsal artery to abdomen ;
oe, gullet; pl, 1-5, swimmerets; pig, tail; ps, hinder part of stomach ; sa,
artery along sternum ; ¢, testis (also tail) ; waa, artery to abdomen ; vd, duct
from testis; vdo, outer opening of duct.

121

122 ZOOLOGY

in shallow water, or it can swim free in the water. By suddenly
striking the tail fin forward the lobster can dart backward,
trailing the great clawsin the wake. The strokes of the power-
ful tail also tends to roil the mud of the bottom and thus to
hide the retreat of the animal. Although the body is encased
in a cuticula of great thickness and firmness, yet the presence
of thin-skinned joints makes not only the abdomen but also
the largest of the appendages capable of complex movements.

Organs and Functions of Nutrition. — The lobster feeds
principally upon fish, either dead or alive, upon various other
crustacea and mollusks, and also upon marine plants. The
food, held in place by the mouth-parts, is triturated by the
jaws and passes by a short gullet into the stomach. The
outer cuticula is turned in at the mouth and lines not only the
gullet but also the stomach. In the stomach it is thickened

”

and hardened in three points to form ‘ teeth ”’ which, in the
muscular movements of the stomach, clash together in such
a way as to crush any larger particles that have escaped the
mincing of the jaws. Digestion takes place in the succeeding
part of the food canal which runs nearly straight to the last
segment of the body. A great gland (liver) secretes the diges-
tive juices and empties them at the beginning of the intestine.
Beyond the opening of the gland the absorption of the digested
food takes place through the wall of the canal.

Organs and Functions of Respiration. — Owing to the fact
that the lobster lives in the water from which it takes its
oxygen, the respiratory organs are outgrowths of the body
instead of internal tubes as in insects. Such outgrowths are
called gills. Gills must have thin walls to allow of the passage
of gases through them; they must be much branched to make

1 Fig. 123.

ANATOMY AND PHYSIOLOGY OF CRUSTACEA 123

as great a surface as possible for the passage of these gases, and
they must be protected from injury, such as being bitten off
by fishes. Consequently we find the gills of the lobster tufted
and hidden under a fold of the skin — the carapace. From

Fic. 124. — Respiratory organs of Astacus fluviatilis. The gill cover removed,
and gills undisturbed. a ,, small antenna, a2, large antenna; ab, abo, first
and second abdominal segment; eps, ‘‘scaphognathite”’; plb, ‘‘ pleuro-
branch”; pdb;, 42, ‘‘podobranchs’’; ply, first pleopod ; 6-13, thoracic ap-

”

pendages. From Lang, ‘‘Comparative Anatomy.

or near the base of each leg one to four gills arise and lie in the
gill chamber. The water is pumped through this gill chamber
by the motion of certain fanlike organs. Each gill contains
a vessel carrying blood from the body to the gill (afferent)
and one from the gills to the body (efferent). The total
number of gills (Gk. branchia) varies with the species (Fig. 124).
Usually one or two spring from the foot itself (podobranch) ;
one or two from the joint (arthron) connecting foot to trunk
(arthro-branch); and one from the side wall (pleuron) of the
body (pleurobranch!).

1Get a lobster or crayfish and see how many gills of each of these classes
occur on each segment of the thorax (Fig. 125).

124

ZOOLOGY

Organs and Function of Circulation. — The circulatory

organs of the lobster, as of the higher Crustacea in general, are

ems

Fic. 125.—Cross section of thorax of
Astacus fluviatilis of Europe, diagram-
matic. abm, ventral muscles of the ab-
domen; bf, leg; bm, main or ventral
nerve cord; d, intestine; dbm, dorsal
muscles of abdomen ; ep, wall of thorax ;
h, heart ; k, gills; kd, gill cover ; J, liver ;
ov, ovary; pc, space around heart; sa,
sn, artery running along sternum; vs,
ventral blood space. The arrows show
the direction of blood flow. From Lang,
‘“Comparative Anatomy.”

gills.

highly developed. The
heart is a long, muscular
tube lying in the dorsal
part of the thorax. It is
perforated by several pairs
of lateral openings through
which the body fluid passes
from the surrounding body
into the heart.
Thence it is forced down-
wards by a great artery to
the ventral system, for-
ward to the
glands, stomach, mouth-
parts, and eyes, and back-
wards to the muscles of the
The blood that
enters these various organs
oozes out into the general
cavity of the body, streams
into the gills, and is thence
returned to the heart.
Thus the heart and the tis-
sues receive blood full of
oxygen acquired in the

cavity

digestive

abdomen.

The blood of the lobster is not colored red like our

“blood because it lacks the blood corpuscles that give our blood

its color.

Nevertheless the blood is able to absorb oxygen

from the water and give it off again to the tissues.

ANATOMY AND PHYSIOLOGY OF CRUSTACEA 125

Excretion. — The elimination from the blood of the waste

products of tissue changes takes place in a pair of organs lying

at the base of the antenne, and known
as the green glands. Into these organs,
which contain coiled tubules, the arteries
enter and give up the waste products.
These products accumulate in a bladder
lying over the gland and from time to
time pass out through a duct whose
opening may be seen at the base of the
great antenne.

Reproductive Organs. — The sexes
are separate in the lobster. The eggs
are produced in a pair of great sacs
which run along on top of the other
viscera and are united by a connecting
strand (Fig. 126). Each sac has its own
duct to the exterior, and this opens at
the base of the third pair of walking
appendages. The sperm is formed ina
pair of sacs resembling the ovary in
general shape, but opening by a duct at
the base of the last thoracic appendage.
It will be noticed that excretory gland,
oviduct, and sperm duct all open out at
the base of appendages, and we shall see

Fic. 126. — View of ovaries
and oviduct (od) of Ameri-
can lobster, dorsal part
of carapace removed.

in studying the structure of ringed worms (‘ annelids ”’) that
nearly every segment has its duct. Consequently the three
paired ducts of the lobster may be regarded as a rudiment

of the condition found in ringed worms.
Musculature of the Lobster. — As the outer cuticula of the

- 4>—con,

Fic. 127.— A single facet
or elementary eye of
the lobster. crn, clear
cuticula; nl.crn, nuclei
of cuticula ; con, cone
cell ; nl.con, its nuclei ;
nl.dst, nuclei of outer
pigment cells (retina) ;
nlpx, nuclei of inner
pigment cells; rhb, rod;
mb.ba, membrane lying
at base of rods; fbr.r,
new fibre to pigment
cells. G. H. Parker.

ZOOLOGY

lobster is very thick and strong it affords
correspondingly powerful support for the
well-developed musculature, for, as in the
grasshopper so in the lobster, the muscles
are attached to and pull upon the cutic-
ula. The powerful muscles are able to
make the strong strokes of the abdomen
In the abdomen the
dorsal muscles run longitudinally from

used in swimming.

the front edge of one segment to the front
When they contract,
the abdomen is straightened.

edge of the next.
The ven-
tral muscles are very complicated. They
run from one segment to the next and,
as they are attached below the hinge of
the segments, when they contract the
abdomen is bent. The musculature of
the appendages is well developed and
complicated.

The nervous system is arranged essen-
tially like that of the cricket. From the
dorsal brain two nerves pass around the
gullet forming the esophageal ring and
then pass as a pair of nerves near to the
ventral line as far as the hinder opening
(anus) of the food canal. The two nerves
are tied together by ganglia in most of
the segments, and nerves are given off
to the appendages, body muscles, viscera,
and sense organs.

Of the sense organs touch seems to

ANATOMY AND PHYSIOLOGY OF CRUSTACEA 127

be located chiefly in the long antenne which serve, like a
blind man’s cane, to inform the creature of what lies some
distance in front of him. The location of the chemical sense
seems to be in the smaller antenne. The eyes are well
developed and are placed on long stalks capable of a certain
degree of rotation and of retraction out of danger. The

Fie. 128.— Upper figure, young lobster with otocyst in place showing
normal behavior. Lower figure, the same with otocyst removed; keeps
upright with difficulty. From Loeb.

eye is compound like that of the cricket, and as many
partial images are formed on the sensitive part of the eye
—retina—as there are facets or elemental eyes (Fig. 127).
There seems to be no true sense of hearing in the lobster;
but it has a special organ of equilibrium and apparently a keen
sense of position. This organ is the otocyst and is located in
the basal joint of the smaller antenne. The young of the
lobster does not have an active otocyst (Fig. 128). The animal
tends to roll from side to side except as the hanging appendages
aid in keeping it stable. At a later stage its otocyst becomes
active, and then the larva keeps its appendages stretched out
in front and swims without rolling over. The otocyst is the
chief organ that enables it to tell when it is right side up.

CHAPTER IX

THE CRAYFISH: A STUDY IN GEOGRAPHICAL
DISTRIBUTION

Every animal is adjusted to particular conditions of temper-
ature, moisture, light, contact, food, and other factors of
environment. These adjustments determine, as has been
abundantly illustrated in the preceding chapters, the exact
situation an animal shall occupy. The situation is known as
its habitat. The number of different kinds of habitats is very
great. They may, however, be grouped into certain large
classes, so that we may distinguish marine animals, fresh-
water animals, terrestrial animals, subterrestrial animals,
aerial animals, and so on. A particular species lives normally
in one of these classes of habitats, and its distribution on the
earth is hmited by the bounds of its habitat. Thus the dis-
tribution of the brook trout follows branching lines on the map
because the streams themselves do so. There are very few
animals, either in the sea or on the land, whose distribution
is ubiquitous, just because their suitable habitats are widely
separated.

But not all of the similar habitats all over the whole world
are occupied by a single species adapted to such a habitat.
The trout of the brooks of one continent are not exactly the
same as those of another continent. We find rather, in widely
separated areas, different species which occupy precisely
the same kinds of habitats. Consequently the traveller who

journeys from his native land to a foreign country meets there
128

THE CRAYFISH 129

a collection of strange animals. The American leaves behind
him such wild animals of the woodland as the Virginia deer,
the skunk, the woodchuck, porcupine, and opossum, and, if he
goes to Europe, may see instead the roebuck, the polecat,
and the hedgehog, but no representative of the group to which
the opossum belongs. If he goes to Africa, his familiar forms
will be replaced by still stranger ones. Instead of the deer he
will meet with antelopes and a lot of new groups represented
by the elephant, rhinoceros, and hippopotamus. If he journeys
to Australia, he will find that practically all the wild animals
belong to the same group as does our opossum. The deer are
there represented by kangaroos and the porcupine by the
wombats. This dissimilarity even of the land quadrupeds in
different parts of the globe has made it possible to divide the
land into certain life-regions. Thus we have the North Amer-
ican; the Eurasian (7.e. Europe + northern and central Asia) ;
the Oriental, south of the Himalayas ; the Ethiopian, including
that part of Africa south of the Sahara; the South American
which stretches north into Mexico, and, finally, the Austra-
lian (Fig. 129).

These different life-regions are land areas more or less com-
pletely separated from each other by barriers of some kind,
such as water, mountain chains, vast desert tracts, or sudden
changes of temperature. In each of these isolated regions
a peculiar and characteristic collection of animals, known as its
fauna, has come todevelop. The faunas of some of these re-
gions are more closely interrelated than those of others, and this
interrelation often gives an important clew to land connections
in former geologic times. Thus the North American animals
are much more closely related to those of Eurasia than are the

African. This similarity of animal forms speaks for a former
K

130 ZOOLOGY

land connection between Europe and America by Behring’s
Strait or by the way of Greenland.

The comparison of the animals of a new country in which
one may be journeying with those of one’s native land gives

b as
“tO
Ro Ge

Pee oN Sees 5
| he eh OTP pel Bots
ciel res
OS, ay
7 bila On
=

i
‘S

ce
(eo eee + |

T+

4 Zi
( es

Fic. 129. — The zoological regions of the globe. 1, North American; 2, South
American; 3, Eurasian; 4, Ethiopian; 5, Oriental; 6, Australian.

the keenest zest to travel. We see, therefore, how important

it is to be acquainted with the native fauna of our own

country.

As a specific example of geographical distribution the cray-
fish 'may be considered. This animal, which is closely related
to the marine lobster,? is an inhabitant of fresh-water lakes,
rivers, and pools. It thrives in diverse surroundings; for

1 The old English spelling of this word was ‘“crevis” or “crevice.” The
cre came to be spelled phonetically cray, while vis became changed to fish in
accordance with the popular nomenclature of all aquatic animals.

2 The English word “lobster”’ is from the old English lopystre, which is

probably corrupted from the Latin locusta, by which term Pliny refers to
the lobster.

THE CRAYFISH 131

some species prefer cool mountain streams and others muddy
pools, while certain species, both in Europe and America, are
found in brackish as well as fresh water. Indeed, the Euro-
pean Astacus fluviatilus is said to be frequently caught off the
Livonian coast, even some distance out at sea. Individuals
of an American species have been taken from a mineral spring
impregnated with sulphur and magnesia at a temperature of
70° F. (21° C.), while several kinds of the American “ bur-
rowing” or “chimney ”-forming species have been found
in meadows and clay bottoms, often at great distances from
streams. Certain species that are blind inhabit caves only.
In England, according to Huxley, “in granite districts, and
others in which the soil yields little or no calcareous matters
to the water which flows over it, crayfishes do not occur.
They are intolerant of great heat or of much sunshine; hence
they are most abundant in those parts of rivers which flow
east and west, and thus yield the most shade from the midday
sun.”

There are two great groups of subfamilies of crayfishes.
One, restricted to the Northern Hemisphere, is found in
Europe, Asia, and North America. The other is found in the
Southern Hemisphere, in Australia, Tasmania, New Zealand,
Fiji Islands, Madagascar, and South America. No crayfishes
have been found on the continent of Africa or in the rivers of
northern Asia that flow into the Arctic Ocean, or in those of
southern Asia. These Asiatic rivers are populated by fluviatile
crabs, to which the crayfishes of the region have probably
succumbed. All the islands now inhabited by crayfishes, such
as England and Japan (excepting Cuba), were probably once
connected with the mainland (Fig. 130).

The northern subfamily of crayfishes contains, according

1382 ZOOLOGY

to Faxon, two genera— As’tacus and Cam’/barus— of which the
latter can be subdivided into the subgenera Cambarus and
Cambaroides. These groups occupy distinct geographical
areas. The genus Astacus is found, in the Old World, in
Europe and western Asia as far south as the Aral and Caspian
seas, and in America in the region west of the Rocky Moun-

Fic. 130.— The distribution of erayfishes. The shaded areas are inhabited
by various genera as described in the text.

tains, draining into the Great Salt Lake and the Pacific Ocean.
It is thus seen to occupy the western sides of the two northern
continents. Likewise Cambarus and Cambaroides occupy the
two eastern coasts of the northern continents; for Camba-
rus is found in North America east of the Rocky Mountains
in the region bounded on the north by Lake Winnipeg and
New Brunswick and on the south by Guatemala and Cuba,
while Cambaroides is limited to the Amoor River basin in
Asia, and to Japan.

We thus find among the crayfishes what is known as dis-

THE CRAYFISH 1383

continuous genera; that is, genera which now occupy widely
separated areas, like Astacus in Europe and Pacific North
America, but which once ranged over the intervening regions
as well. From some cause, the struggle for existence became
too severe in the intervening regions, so that Astacus and Cam-
barus were annihilated on the eastern and western sides of
the continents respectively. In southern Asia we find that the
struggle was doubtless with the successful river-crab. It is
interesting to note that, probably on account of the preserving
influence of climate, the other animals and the plants of the
eastern sides of the two continents and those of the western
sides are more alike than those from opposite sides of the same
continent. One of the best pieces of evidence for the conclu-
sion of a former hemispherical distribution of the two genera
of crayfishes is that there occur in the caves of Carniola in
southern Austria crayfishes! belonging to the genus Cambarus ;
—the only known living representatives of this type in
Europe. The mere fact that it lives in a cave is not sufficient
to make the crayfish Carniola of a Cambarus, for in North
America the genus has certainly not originated under the in-
fluence of subterranean life ; it is more likely that the caves of
Carniola have protected these crayfish from the widespread
destruction which has overwhelmed their fellows outside.
Only one crayfish, Cambarus bartonti, is found in New England,
and here only in the rivers of Maine, Vermont, and central and west-
ern Massachusetts. The common species of the Middle States is
C. affinis. C. diogenes and C. immunis are common burrowing species

of the Central States. C. pellucides is the blind species found in
Mammoth and Wyandotte caves.

The food of the crayfish is very varied; it may be living or

1 These crayfishes are blind, like the cave-inhabiting Cambarus of America.

134 ZOOLOGY

dead, animal or plant. On account of the need of calcareous
matters in the food, crayfishes are especially fond of the
stoneworts (Chara) and various succulent roots, like the carrot.
It is said that crayfishes sometimes make excursions inland in
search of plant food. They likewise devour shells of snails,
their own cast-off skins, and occasionally one another, shell
and all.

The crayfish belongs to the class of Crustacea, since it
breathes by means of gills, possesses two pairs of antenne,
a pair of mandibles bearing palps, and a pair of appendages
on all body segments excepting the last. The Crustacea are
divided into two subclasses, — Entomos’traca, of which
Daphnia is an example, and Malacos’traca, to which the cray-
fish belongs. All the Malacostraca! have nineteen pairs of
appendages.

The lobster (Homa’rus) is, as we have already seen, the
nearest living salt-water relative of the crayfish. There are
only two species of the genus Homarus. One, Homarus
americanus, occurs on our Atlantic coast; the other, H. vulgaris,
is the lobster of Europe. On our Pacific coast there is the
“spiny lobster,” but this is not closely related to the Eastern
lobster (Fig. 131). The national government has transplanted
the Atlantic lobster to several localities on the Pacific coast,
but it is not yet known whether it will thrive there. The
American lobster ranges from Labrador to Delaware Bay,
and from near shore to a depth of 100 fathoms. It attains
its greatest size on the rocky shores in the cooler waters from
Maine to Labrador. It migrates but little along the coast;
in the fall, however, it moves out into deep water, and in the

1From malakos, soft, ostrakon, shell; since the shell is less hard than that
of mollusks.

THE CRAYFISH 135

spring back again into the shallower bays; the time of migra-
tion depending upon the length of the season. It is said to be
a nocturnal animal, searching most actively for its food at

itl

Fig. 131.— Palinurus, the spiny lobster. One-fourth nat. size. From Rath-
bun; drawn by H. L. Todd.

night. The sense which probably aids it most in this search
is the chemical one, as the attraction of the bait in the traps —
the so-called lobster-pots — testifies. In respect to food it is,
like the crayfish, omnivorous.

Protection of the Lobster.— There has been much dif-
ference of opinion in regard to the size at which a lobster

136 ZOOLOGY

becomes mature and before which, therefore, it cannot be
caught without danger of extermination. The legislation on
the matter has accordingly been very varied. In Connecticut
the law makes the limit six inches, while in Massachusetts
and New York it is placed at ten and one half inches. Her-
rick has carefully investigated the relation of length to maturity,
and concludes that, on the Massachusetts coast at least, the
lobster becomes mature between the limits of eight and twelve
inches, and hence that all present legislative protection is
insufficient. The rarity of large lobsters in our markets
testifies to the correctness of this conclusion.

Enemies of the Lobster. — Besides its worst enemy, man,
both the adult (particularly the egg-bearing female, called by
fishermen the ‘ berry lobster”? or “berry hen”) and young
lobsters are attacked by many kinds of fish. Two or three
internal parasites are known to infest the lobster, while some-
times it is greatly hampered in its movements by the number
of messmates it carries about attached to its shell. Barnacles,
mussels, tube-forming worms, and various sea weeds are all
found at times attached to the shell of the lobster. Upon
molting, however, the animal is enabled to rid itself of all
these hangers-on; but this process is attended with great
dangers to the lobster, since the animal is, during molting, so
soft bodied as to be able to offer little resistance to its enemies.

The molting process in the lobster and crayfish is
accomplished in the following manner: previous to the
throwing off of the old skin a new soft one is formed in-
side, the lime is absorbed from the old shell in a dorsal
line along the carapace, reaching from the rostrum to
its posterior margin. Absorption also takes place at the
joints of the limbs. Such absorptions give a greater flexi-

THE CRAYFISH 137

bility to the shell, which is useful in the act of molting.
When the lobster has attained this stge, it is dark in color, and
known by fishermen as the “ black lobster.” The soft cutic-
ula now breaks transversely immediately behind the carapace,
the blood leaves the limhs, which are thus made flabbier, and
by involuntary muscular movements they are drawn, large
claw and all, through the joints of the old shell. The anterior
portion of the body is first drawn out through the break behind
the carapace and, lastly, the tail. Not only isthe entire outer
covering cast off, but the lining of the esophagus, stomach, and
intestine as well, since these organs are formed by an infolding of
the skin. By means of the return of the blood to the limbs and
rapid absorption of water, the body of the lobster soon swells
to a size far beyond that of the old shell. There remains
in the stomach, after molting, a calcareous nodule which has
long been known by the name of “ crab’s-eye.”’ These “ crab’s-

“charms ”’ against

eyes”’ were formerly much sought after as
ill health. Their function was for a long time rather
obscure. It is now believed that during the time of ab-
sorption of lime from the shell, previous to molting, the
blood becomes strongly impregnated with lime. If all the
lime that must be removed were to remain in the blood,
it would probably be fatal to the animal; hence it is taken
up by secreting cells located in the wall of the stomach,
and there deposited. After the old skin is cast, the gastro-
lith is soon absorbed, probably to aid in strengthening
the new shell. Bits of water-worn shells, entire gastropod
shells, parts of lobster coverings, spines of sea-urchins, etc.,
have been found in the stomachs of lobsters and crayfish,
which likewise would probably have been dissolved and used
in hardening the shell.

138 ZOOLOGY

Shrimps and prawns! belong to a thin-skinned, long-tailed
family of Crustacea.2. They are extremely common in bays
along our coast, and even penetrate into rivers. Two river
shrimps * are found in the United States east of the Mississippi
River. These Crustacea are able to maintain their enormous
numbers only by virtue of their great reproductive capacity,
which is the mere necessary since they furnish almost the
entire food supply for many kinds of fishes and other foes.

Fic. 132. — Palemonetes vulgaris, a common shrimp.

Even in the principal shrimping grounds of the United States
—such as San Francisco and New Orleans — there is said to
be no diminution in the numbers of shrimps.

The burrowing shrimps (Thalassinide‘) are crayfish-like
species that burrow in the mud flats of our coast. They
remain concealed during the day. They are much smaller
than crayfishes and are difficult to obtain, so they have no
market value and are commonly little known.

The hermit-crabs (Paguride®) occupy a position inter-
mediate between the long and short tailed decapods in respect

1The term ‘‘shrimp”’ is applied to the smaller species, and ‘ prawns” to
the larger.

2 Fig. 132.

3 Palemon Ohionis and Paleomonetes exilipes.

4 thalassinos, color of the sea.
5 pagouros, a kind of crab.

THE CRAYFISH 139

to the length of their abdomen. The abdomen is soft, and
the young animal, which is at first free-living, protects it by
inserting it within the coiled shell of some gastropod. The
abdomen becomes unsymmetrical, being coiled to one side
to correspond with the shape of the borrowed house (Fig. 133).
The abdominal feet become degenerate, with the exception of

Fic. 133.— EHupagurus longicarpus. Two individuals in shells. Photo. while
alive by W. H.C. P.
the posterior pair, which are each modified into a sort of hook,
by means of which the crab maintains itself securely in the
shell. When one shell becomes too small, it is abandoned for
a larger one. Numerous species of hermit-crabs occur on our
coast, ranging from the shore line to a depth of several hundred
fathoms. Eupagurus longicarpus is the active little hermit
found in almost any tide-pool from Massachusetts Bay to the
Gulf of Mexico. Hydroids, polyps, sponges, often attach
themselves to these borrowed shells (Fig. 133); indeed, one
Chinese species always bears an anemone on its large claw,
with which it plugs up the aperture when obliged to retreat
within its shell. One of the East Indian hermit-crabs, the

140 ZOOLOGY

so-called palm-crab, feeds upon cocoanuts, which it opens by
inserting its claws into the eyes and then breaking the shell
upon the rocks.

The mole-crabs (Hippide!) include certain oval animals
that burrow in sandy beaches, head first like a mole. The
abdomen is partly turned under the body in a position some-

Fic. 134.— Eupagurus longicarpus removed Fic. 135. — Hippa talpoides.
from shell. 13. Photo. by W. H.C. P. Nat. size. Photo. by
WW. FG P.
thing like that of the crabs. Therefore these animals make an
interesting link between the long-tailed (Macrura) and short-
tailed (Brachyura) crustaceans (Fig. 135).

The crabs (Brachyura) are represented on our shores by
three principal families, which may be designated as triangular
crabs, arched crabs, and square crabs.

The spider-crabs, or sea-spiders, as they are sometimes
called, belong to the triangular crabs. As their name imples,

1Trom hippos, horse; used by Aristotle as the name of a kind of
crab,

THE CRAYFISIL 141

their legs are very long and slender. These crabs frequent
oyster-beds and sea-bottoms in general. When seen stalking
over such uneven surfaces, the advantage of these stilt-like
legs is at once evident. The surface of the body of some
species of spider-crabs is hairy, entangling inorganic matter,

while hydroids, barnacles, and algz attach themselves to the
shell, so that the crab, when quiet, is concealed by them, while

“es a? wy
a4, a SO tte a A Be he alien, Se eee

Fic. 136.— The smaller spider-crab, Libinia dubia. Two specimens lying on
the beach.

these attached organisms, in turn, gain by their association
with the crab most of the advantages of locomotion. Libin’ia
dubia (Fig. 136), which ranges from Cape Cod to the Gulf
of Mexico, is the commonest of our species that undergo such
concealment. The great Japanese spider-crab is said to be
the largest of all the Crustacea, some individuals measuring,
from tip to tip of the first pair of legs, 18 to 20 feet.

The edible crab is a typical arched crab. It is so called

1Fig. 136.

142

ZOOLOGY

because the carapace is arched in front. The carapace is also
broader than long, and narrower behind than in front. The

Fic. 137.— Panopeus sayt, al-
lied to Cancer. The mud-
crab. One-half nat. size.
Photo. by W. H.C. P.

legs of this family are short and
broad, and in some species the pos-
terior pair is especially broad — an
adaptation for swimming. These
crabs may be divided into two
groups—the burrowing crabs and
swimming crabs. To the burrowing
crabs belongs the genus Cancer
(Figs. 137, 138), which includes the
edible crab of Europe, especially

prized in England, together with several American species ;

while our common edible,

soft-shelled or blue crab, Callinec’tes

by W. H.C. P.

hasta’tus of the East, and the beautiful “ lady-crab”’ (Fig. 139),
belong to the swimming group. Crabs of other families are,

THE CRAYFISH 143

however, eaten in various localities and by various peoples.
For example, our little oyster-crab (Fig. 140), found in the

Fig. 139.— Platyonichus ocellatus, lady-crab. Reduced to one-third. Photo.
by W. H.C. P.

mantle chamber of the oyster, is eaten by us together with the
oyster or separately.

The fiddler-crabs are representative of the square crabs.
These are the familiar animals which crowd salt-marshes and
run sideways to and from their
burrows (Fig. 141). One claw
is much larger than the other.
When the crab is disturbed, the
large claw is brandished in a

manner which has been likened ee ee eae :

G. : innotheres ostreum. x 4.
to the movements of a fiddle From Rathbun.
as one plays uponit. Gelast’/mus pug'naz is the most abundant
species, and ranges from Cape Cod to the Gulf of Mexico.
Together with Cambarus it does much damage by burrowing
in the levees of the Mississippi River (Fig. 142).

144 ZOOLOGY

There remain to be considered a number of orders of the
higher crustacea (Mal’acostraca) other than decapods. The
mantis shrimp (Sto-
map’oda) is so called
because of a certain
resemblance to the
mantis insect (Fig.
143). This animal is
found on our east
coast, where it bur-

Fic. 141.—Gelasimus pugnaz. Nat. size. rows in the sand. It
Fronto-dorsal view. Photo. by W. H.C. P. is a little longer than

a crayfish. Being hard to catch, it is not much used as

CAB “ae Nae

Fie. 142.— Fiddler-crabs and their burrows. The method of exposing the
large claw at the opening of the burrow is shown.

THE CRAYFISH 145

food. The Isopoda! include certain marine and fresh-water
groups, and the sow-bugs or wood-lice (Fig. 144), note-

worthy as the largest group of land
Crustacea. The Amphipoda? are
exclusively aquatic creatures, found
under decaying vegetation on
beaches of lakes or the sea (Fig. 145),
and crawling amidst marine hy-
droids. Being laterally compressed,
the Amphipods tend to lie on one
side when at rest.

The economic importance of the
decapods may be inferred from the
fact that the receipts for the Atlantic
lobsters taken and sold by United
States fishermen was estimated for
the year 1901 at $1,400,000.

Formerly the American lobster

was more numerous

and attained greater
size than now, but
excessive fishing has
so depleted the sup-
ply that the lobster

so-called Norwegian

Nai i:

Fic. 143. — Squilla empusa, the
mantisshrimp. Dorsal aspect.
From Rathbun.

is in danger of extermination. In Europe the

lobster is much used as

food, while on our Californian coast the so-called

Fic. 144.—Onis- spiny lobster or sea-crayfish takes the place

cus, the sow-
bug. Dorsal

of our true Atlantic lobster and, like the latter,

view. Nat.size. jg said to be in danger of extermination on

Photo. by
W.H.C.P. 1 sos, equal ; pous, foot.
L

2amphi, both; pous, foot.

146 ZOOLOGY

account of overfishing. The crayfish is not as much used
for food in America as in Europe. In Paris it is so much
esteemed that the enormous crayfish farms throughout France
are unable to supply that city; consequently crayfishes are
imported from Germany.
In America, it is our French
population mainly that
makes a market for the
crayfish.

Of the crabs which reach
our market the most im-
portant is the blue crab.
These crabs are kept moored
in floating boxes until they
have molted, and then they
are sent to market as soft-

Fic. 145.— Talorchestia longicornis, the
beach flea. Nat. size. Photo. by shelled crabs. The value of
W.H.C. P.

the blue-crab fisheries on the
Atlantic and Gulf coasts was almost half a million dollars.
The shore-crabs (Cancer) are little eaten in the United States.!

The shrimps and prawns have within recent years begun to
appear in large numbers in the Eastern markets. For many
years the Pacific species have been dried and shipped by the
Chinese in large quantities to China.

Development of Lobsters. — Lobsters lay eggs in July and
August. In the fall they migrate to deep water, and pass the

1 Very unfortunate is the destruction of the ‘“king-crab”’ (Limulus), which
is only distantly related to the Decapoda. In Delaware Bay they are caught
in great numbers and ground up as fertilizer. As they are taken only during
the breeding season, they are being rapidly exterminated. The American
Limulus belongs to an order entirely unrepresented on the European coast
(Fig. 146).

THE CRAYFISH 147

winter there. In the spring they migrate back to the shore —
the female tarrying behind the male until the eggs of last
summer, which she still carries attached to her swimmerets,
shall be further grown. In June the young hatch out, molt,

Fic. 146. — Limulus polyphemus, the king-crab or horseshoe-crab.

and swim to the surface. The female now molts, but does
not spawn again for a whole year; that is, she spawns in
alternate years. The number of eggs carried varies with the
age of the female; middle-aged lobsters may carry up to one
hundred thousand eggs, but the old or young ones as few as
three thousand. The egg as freshly laid is about 1.5 milli-
metres in diameter and is stored with food material, called
yolk, much as in the case of the hen’s egg. As in the chick,
the development takes place, as it were, on top of the egg
(Figs. 147, 148). Eyes and mouth appendages early make

148 ZOOLOGY

their appearance ; then the other appendages, and the tail (Fig.
149). For a long time the back of the thorax is greatly dis-
tended by the yolk stored there, and the eyes are huge (Fig.
150). During the early moltings (Fig. 151) the young lob-
sters undergo a terrible mortality, so that out of ten thousand
embryos hardly two, on the average, survive. After the fifth

Fic. 147.— An early stage of devel-
opment of egg of thelobster. Ap- es :
pendapes becoming bifid. Paired Fic. (148. — Surface view of egg nau-
dotted areas above indicate eyes; phius. Antenne show beginning of
these are followed by the first three segmentation; mandibles and max-
paired appendages; antennules, an- illee seen on each side of the abdo-

tenne, and mandibles. Below in men. Embryo 16-18 days old.

the middle line is the forming tail ; x 25. From Herrick.

above isthe mouth. After Herrick.
or sixth molt the little lobsters sink to the bottom, and then
begin their journey shoreward. From this time until they are
about four inches long, only very few individuals have ever
been seen. This is due, it is said, to the fact that they hide
deep down among the rocks, where they cannot be dredged.
When they are four inches long or so, they become bolder,
leave the rocks, and, like the adults, make burrows for them-
selves in the sand or uncler stones.

Development of Crayfish. — The crayfish develops simi-

THE CRAYFISH 149

larly to the lobster, —from a large egg filled with yolk. The
early stages are much like those of the lobster; but those
changes which in the lobster take place during the first three
stages of free life are in the crayfish passed in the egg. Con-
sequently at the time the crayfish hatches it is almost, but
not exactly, like an adult crayfish except in size. The tail-

Fic. 149.— Surface view of embryo Fig. 150.— Lobsterembryo. 61 days
with all of thoracic appendages old; eyes have developed pigment.
formed. The forked telson partly x 15. From Herrick.
overlies the brain. Note the large
eyes, which are yet without pig-
ment. Embryo about 21 days old.

x 25. From Herrick.

fin of the just-hatched crayfish has, to be precise, a somewhat

more oval form, and the first pair of swimmerets are undevel-

oped; but these differences soon disappear.
Regeneration of Lost Parts. —If you attempt to pick up

a crab by one of its claws, you frequently find yourself in

possession of a portion of the leg only, while the crustacean

has made good its escape. Moreover, it will be seen that the
leg always separates at a certain place; namely, between the
second and third segments. This is the place where a fusion

150 ZOOLOGY

occurs between two segments which are free in the first larval
stage. This power of protective mutilation occurs in those
appendages which are most apt to be seized, — namely, the
and is wholly under the control of the
reflex nervous system, for it may occur when the entire volun-

five thoracic legs,

tary nervous system has been removed. The leg of a dead

Fig. 151.— Larval view of lobster, extracted from an egg
which was about ready to hatch. The concretions in the
intestine are destined to go into the new cuticula after
molting. » 25. From Herrick.

crustacean shows no such capacity. If the leg of a lobster is
cut off at some point beyond that of normal rupture, the limb
will later be found cast off up to this point. Here a sort of
double membrane or diaphragm exists, with a central opening
only large enough to admit the passage of nerves and blood-
vessels. Upon rupture this passage is soon plugged up by
coagulated blood — clearly a device to prevent excessive
hemorrhages. Soon after a leg is cut off a papilla-like body

THE CRAYFISH 151

grows out from the stump of the limb, develops into the shape
of a small limb, and grows larger, with each successive molt,

until the normal size is reached.
The antennz, too, are much exposed
to injury, but with them autotomy
is not practised. They begin to
grow out at the place of injury, and
at least one molt is necessary for
their complete restoration.
Abnormalities in the claws of the
lobster are not uncommon. The
thumb-like protuberances of the
next to the last of the joints of the
great claw is sometimes bifid, or
carries a large wart. The finger
which opposes the thumb is also
sometimes forked (Fig. 152). Many
of these abnormalities are probably
due to injury of the claw; but others
cannot be explained in this way.
For instance, cases have been ob-
served of lobsters having crushing
claws of equal size on the two sides
of the body. Similar abnormalities
are found in other arthropods.
They are always instructive be-
cause, being natural phenomena,

Fie. 152.—Two abnormal claws.
Upper figure shows a double
outgrowth to the finger. In
lower figure there is an extra
finger. From Herrick.

they must have a cause, and this lies in the altered conditions

of development.

Physiological Division of Labor. — The difference between a
“highly developed ” animal and a lowly organized one is not

152 ZOOLOGY

first of all a difference of size nor a difference in the number
of parts, —just as a large population or numerous cities are
not the primary characteristics of a highly civilized state. But
just as a complex civilization is one in which each of the
different citizens has his own special task to perform for the
commonwealth, so a highly developed organism is one in which
each different organ has its special réle to play. The worm
Nereis! has more segments to the body than the crayfish, but
these segments are very nearly alike —the fins especially are
quite similar. In the crayfish, on the other hand, the append-
ages are dissimilar. Each pair has a special function to perform
and is specially adapted, often complexly fashioned, to meet
this need. What is true of the appendages is likewise true, to
an equal degree, of the internal organs. The internal organs
of Nereis are repeated in each segment; but in the crayfish
the egg ducts le in one segment, the heart in another part of the
body, and so on. Some of the segments have given up one or
more functions to perfect a single one in which it has specialized.
There has been a division of labor between the different parts
of the body, and in consequence a greater perfection in the
performance of each function. More perfect fulfilment of
function is the result of physiological division of labor, just
as a higher civilization is the result of individual division

of labor.
1 Compare Figure 161.

CHAPTER X

DAPHNIA: A STUDY OF THE FOOD OF FISHES

Ir one sweeps the long grass in a field with a stout, fine net,
one will gather in a minute or two great numbers of insects.
In this way one gets a notion of the vast abundance of insects
that there must be on all the land. Little wonder then that
vegetation suffers so from insect attacks or would suffer were
the number of insects not kept down by birds, lizards, and
toads which find their principal subsistence on them.

What insects are to the land the water-fleas or Entomostraca
are to the water; they are ubiquitous there. And what in-
sects are to the birds Entomostraca are to fishes. How numer-
ous they may become is shown when a fine silk net is drawn
through the water and the small Entomostraca are strained
out. By these means the volume of small organisms in one
cubic centimetre of water has been determined for various
localities. It appears, in general, that the organisms are more
numerous in lakes than in streams (Fig. 153). Thus in studies
made in the middle Illinois River and adjacent lakes the
volume of organisms in 1 cu. metre of water was, for a
small stream, 0.3 of a cubic centimetre; for a large river
(the Illinois) 3 cu. em. ; for five lakes in Illinois, 2 to 23 cu. em.
In one year the river (at Havana, Illinois) discharges 75,000
tons of microscopic organisms (Kofoid). In studies on the
small lakes of Wisconsin, Birge has calculated the number of

Entomostraca in a cubic metre at different levels and at different
153

154 ZOOLOGY

times of the year. The average for all localities and periods
is about 40,000 individuals per cubic metre of water in the
lakes. In the late spring the population of the lakes may rise
to 250,000 per cubic metre near the surface; near the bottom

Fie. 153.— A typical lake, exposed to the sunlight and swarming with alge
and Entomostraca.

it may fall to 500 or even less. Ina lake of 80 square kilometres
there may be 160 billion Entomostraca weighing all together
about 20 tons, and this mass of organisms is renewed several
times each summer.

The abundance of Entomostraca in a lake varies with the
time of year. The numbers are relatively small during the
winter, but with the melting of the ice at the end of March

DAPHNIA: A STUDY OF THE FOOD OF FISHES 100

or in April they begin to increase, reaching a maximum in May.
During the midsummer a marked decline occurs, to be followed
by arise at the end of September or in October; after that
the numbers decline for the winter. The reason for these two
maxima is that the spring and autumn are periods of rapid
growth of the food of the Entomostraca, and this in turn is due
to the mixing up of the waters at those periods, and conse-
quently of the salts and organic stuff upon which, in last
analysis, the Entomostraca depend. This mixing up of the
waters depends on the variation of the density of water
as its temperature changes. Water is heaviest at 4° C.
above the freezing-point and tends to settle below water
that is warmer or colder than 4° C. In the spring the bot-
tom waters remain near the freezing-point (0° C.), while the
surface temperature rises. As it approaches 4° the surface
water grows heavier and falls to the bottom, forcing the colder
water up, and this goes on until the whole mass of the water
has reached the temperature of 4°,— this constitutes the spring
circulation of the water; after that, the surface water, becom-
ing still warmer, remains on top. In the autumn the whole
mass of water, even to the bottom, has at first a higher tem-
perature than 4° C., but as the frost comes the surface water
gredually approaches 4° C. and begins to fall, forcing the
warmer, lighter water to the surface. Eventually the densest
(4° C.) water is at the bottom, while the surface water freezes
(at 0° C.) and floatson top. This is the autumnal movement
of the waters. By means, then, of these remarkable vertical
movements of the waters of lakes the bottom food is made
available for the surface swarms of Entomostraca.
Entomostraca live not only in fresh water, but also in the
sea — that greatest consumer of the sun’s energy. Living

156 ZOOLOGY

in a rich soup of smaller green organisms upon which they can
feed, they multiply enormously. As many as 20,000 of the
adults of one species of Copepod have been counted in one
cubic meter of sea water, and of larval Entomostraca, nearly
200,000. And the total volume of the Entomostraca of the
ocean, if brought together, would make a conical hill about
12 kilometres in diameter and 300 metres high. The
Entromostraca of the sea if driven into Long Island Sound,
which is 80 miles long and 10 miles wide, would fill it full from
the bottom to the present sea-level, leaving no room for water,
and this vast bulk of organisms is frequently renewed.

This enormous mass of Entomostraca is made available
for man, since it forms the principal food of many edible fishes.
As the fish swims through the sea near the surface it opens its
mouth and lets the water flow into it and out at the sides
through the gills. In passing out the small solid particles
are strained from the water by the gill-rakers and are then
swallowed. As the young fish feed they grow, and so the
Entomostraca are transformed into food for man.

The group of Entomostraca includes a great variety of or-
ganisms which are all of small size with a variable number of
body segments and appendages. There are five orders which
we will next consider.

The fairy shrimps or Branch’iopoda' include long, mostly
macroscopic organisms with 10 to 40 pairs of legs. The legs
are leaf-like and serve both as paddles and as breathing organs.
These animals are found in the spring in pools that dry up
later in the year. They produce eggs which have such thick
shells that they can withstand drying for a year or even several
years; indeed they will not hatch until thev have been dried.

1 Latin, branchium, gill ; Greek, pous, foot,

DAPHNIA: A STUDY OF THE FOOD OF FISHES

157

One genus (Artemia) loves water that is even denser than sea-

water.
is crystallizing out.
largest of our fairy shrimps,
which is conspicuous because of
its broad shell.

The water-fleas or Cladoc’era
include Daphnia and numerous
other very short Entomostraca
that are much flattened from
side to side (Fig. 155). They
live in ponds and lakes all over
the globe. During the autumn
in northern latitudes certain
species lay fertilized eggs that
may lie dormant for a year or
more. During the greater part
of the year females alone occur,
and unfertilized eggs (called also
“ narthenogenetic ’ or ‘ sum-
mer” eggs) are alone produced.

The body of Daphnia is en-
This
makes the Daphnia so heavy
that it tends to sink in the water
and is only kept up by the vig-
orous swimming strokes of the

closed in a heavy shell.

Fic. 154.— A pus

It lives in the Great Salt Lake and in vats where salt
To the genus Apus (Fig. 154) belongs the

glacialis, ventral
aspect. abd.f, abdominal feet;
ant. 1, antennule; ant. 2, antenna;
lbr, labrum; md, mandible; mz,
first maxilla; 0v, aperture of ovi-
duct; s.f.pl, sub-frontal plate;
sh.gl, shell-giand; th.f, thoracic
fect; thf. 1, first thoracic foot.
After Bernard.

legs and its great antenne or feelers which increase the friction

with the water, so that falling is less rapid.

The family of bivaive entomostraca or Os’tracoda! comprise

lgstrakon, shell of a testacean ; eidos, like.

158 ZOOLOGY

some very abundant, minute, bean-shaped little crustaceans,
which have to move their appendages very vigorously to sup-
port their heavy bodies in the water. The Ostracods are found
in almost all pools and streams, especially in the early spring.
Many of them seem to be ex-
clusively parthenogenetic.
Of the Copep’oda‘! the
commonest fresh-water
genus is Cyclops, which
occurs in a similar habitat
with Daphnia and is some-
times found even in pure
drinking water. The fe-
male carries a conspicuous
egg-sac on each side of the
abdomen, and reproduc-

Daphnia tion occurs with such rapid-
Fic. 155.— Daphnia. ant. 1, 2, first and ity that one Cyclops might,
second antenne ; br, brain; br.p, brood-
pouch ; d.gl, gland; f, spines on the fect; under the most favorable
ht, heart; sh.g, shell gland. After Claus. conditions, have 5. billion
descendants in one year. It is consequently easy to understand
how Cyclops often becomes the most. abundant entomostracan
in our waters, and how in some lakes it has been found that
there are over one million of them to each square metre of
water surface. Large numbers of the Copepoda are marine.
One of the most common is Acartia (Fig. 156), which swarms
to such an extent on the surface of the water as to make great
phosphorescent. areas.
Barnacles are the only attached non-parasitic Crustacea.
Certain species of them are found fastened to rocks on the

1kdpe, oar; pous, foot.

DAPHNIA: A STUDY OF THE FOOD OF FISHES 159

Fic. 156.— Acartia, a marine Copepod. Greatly magnified. Photo. by
W.H.C. P.

seashore between tide-marks (Fig. 157). If you watch barna-
cles in rock pools, you can see them open the valves of their

Fic. 157.— Mussel-shell bearing barnacles (Balanus). Photo. by W. H.C. P.

160 ZOOLOGY

shells, protrude their elongated appendages, which together
form a sort of rake, and pull in particles which happen to be
floating about them. Other species of barnacles attach them-
selves to floating seaweed, ship bottoms, and whales; under
these circumstances, despite their sessile habit, they enjoy
a constant change of locality. Barnacles doubtless gain great
protection from the circumstance that they are sessile and
enclosed in shells; but their peculiar habits have given rise to
certain peculiarities in reproduction. They are hermaphro-
ditic; i.e. both male and female germ cells occur in the same
individual. Despite this fact, dwarf male individuals are
occasionally found inside the shell of the barnacle; these are
known as “ complemental males.” The general form of the
barnacles has also become greatly
modified by their sessile habit,
so that they were long regarded
as mollusks, until it was shown
that the larvee are almost exactly
like those of other Entomostraca.

Trilobites! are extinct giant
Entomostraca, closely allied to
Branchiopods. They were im-
mensely abundant in early geo-
logic times, and their remains
form a large part of certain rocks.
They had a segmented body, with
bifid appendages and long an-
tenn, and their compound eyes

Fic. 15.—A restoration of the Were borne on the great frontal
ventral aspect of a Trilobite. shield. Some of them were nearly
Note in particular the character ‘ F 7
of the appendages. After Beecher. half a metre long (Fig. 158).

1 Having three lobsters.

CHAPTER XI

THE ANATOMY AND PHYSIOLOGY OF ANNELIDS

General Form of the Body.— The annelids or ringed worms
(Fig. 159) are of especial interest because they seem to be
the ancestors of all the higher animals having a body composed
of rings or segments. Such are all Crustacea, Tracheata
(including insects), and Vertebrates. The origin of the
ringed condition of the body is uncertain; the lower worms do
not have it, so it must have arisen from the unseemented con-
dition. We can help to understand how segmentation of the
body arose by inquiring as to its present meaning. The rings
are more distinct when the worm contracts, less so when it
expands in any part; consequently the rings are due to the
muscles of the body wall. Now in the most perfect annelids
the cavity of the body is divided by partitions into a series
of compartments, resembling the water-tight compartments of
an ocean steamer (Fig. 161). The muscles of the body-wall
run in each compartment from one partition to the next, so
when they contract, swelling, like all muscles, chiefly in the
middle and little at the attached ends, they cause the wavy
outline of the body that we see in the contracted worm. From
one constriction (partition) to the next is one segment. The
reason why the body muscles run in this way is to permit the
worm to writhe — a mode of locomotion very useful in moving
through mud or even water. The writhing, or S-shaped move-

ment of the body (Fig. 182) necessitates, however, contract-
M 161

162 ZOOLOGY

Fic. 159.— An annelid (Eunice).
Anterior and posterior ends of
the body only; dorsal view. fa
unpaired feeler; fp, paired feeler;
a, eyes; fe, feeler-cirri ; k, gills
pe, dorsal parapodia; p, para-
podia ; ac, anal cirri. After Lang.

ing certain parts of the body-wall
and expanding others on the same
side of the body at the same time,
and this is possible only with short
muscles. When the muscles run
continuously from head to tail, as
in the “ vinegar eel,” the body
flops from one side to the other as
a whole.

The segmentation of the body
has led to important consequences.
Each segment contains not only
its own muscles, but a pair of ap-
pendages that are moved by the
muscles, nerves to control the
muscles, blood-vessels to supply
them with food, and a pair of
excretory organs to carry off waste
products. Each segment is, in-
deed, a nearly complete organism,
and, consequently, even small
parts of an annelid cut out from
the rest of the body may live a
long time and even regenerate the
lost head and tail.

The head of the annelid is simple
in the earthworm and the other
herbivorous forms; but in Nereis
and the other carnivorous species
(Fig. 160) it gains a great size
and is provided with various sense

ANATOMY AND PHYSIOLOGY OF ANNELIDS 163

organs — tactile organs known as dorsal tentacles and ventral
“ palps ”’ and eyes and taste organs. The tail segment, which
contains the anus, frequently bears a pair of tentacles which
are useful when the worm moves, as it often does, backward.

The lateral appendages of the more perfect annelids are
stout, fleshy, paired protuberances on each segment of the
trunk. These are covered with a thin skin to permit of ex-
change of gases with the water, and so they would be without
support were it not for great dark bristles, one of which lies

Fic. 160.— Diagrammatic representation of pharynx of a carnivorous
Annelid. g, brain; k, jaw; ph, pharynx; m, mouth; rt, retractors; pt,
protruders; vf, extrusible part of pharynx; p, its papille. A, pharynx
retracted. B, pharynx protruded. In B, ct, retractors; pt, flexible part of
pharynx. After Lang.

in the axis of each of the two main lobes of the appendage and

serves for the direct attachment of the muscles that move the

appendages. In addition, the appendage carries many finer
bristles (cheetze, whence the name “‘chetopod,” applied to the
group to which Nereis belongs), and these are exceedingly
diverse in form in the different families of chetopods. In
certain species the bristles cover and protect the body (Fig.

179).

The organs of nutrition consist of a food-canal and its glands.
The food-canal usually begins in a mouth cavity at the hinder
end of which is a thick muscular pharynx, the entrance to which
is guarded by a pair of jaws made of the same substance as the

164 ZOOLOGY

cuticula. The remarkable thing about this front end of the
food-canal is that it can be rolled out, carrying the jaws to
some distance in front of the head, where they can seize their
prey and drag it back into the mouth (Fig. 160). Behind the
pharynx comes a short gullet into which glands pour digestive
fluids, and then comes the long intestine, extending through the
middle of the trunk to the last segment. The food-canal of
the polychztes behind the pharynx is characterized by great
simplicity (Fig. 161).

Respiration in polychetes is effected through the skin,
particularly that of the swimming appendages. It is impor-
tant to notice that this is the primitive condition out of which
the respiratory organs of Crustacea have arisen, but in the
latter group, owing to the thick cuticula of the legs and the
larger size of the animal, special outgrowths of the appendages
(gills) have been evolved. We see the beginnings of such
gills in certain polychetes (Fig. 159). In sessile polycheta
(page 188) respiration is confined to certain appendages which
have become greatly enlarged so as to extend beyond the
mouth of the tubes in which they live.

The circulatory system of polychetes is highly developed.
A contracting vessel extends along the whole of the mid-dorsal
line and a smaller tube runs along the midventral line (Fig.
161). These are connected in each segment (Nereis) by a
pair of vessels which (in Polychzetes) break up into capillaries
in the swimming appendages or gills to facilitate respiration.
Blood-vessels also run to the intestine to absorb the digested
food. The heart pulsates rhythmically, forcing blood toward
the head. The blood contains a few corpuscles, but the fluid
is itself red and capable of uniting chemically with oxygen at
the skin and yielding it to the tissues.

resk Lert
NOLL

QOr5.veSS—

vert. vess

TL, CO—

Fia. 161.— Semi-diagrammatic view of anterior part of body of Nereis with
dorsal wall removed so as to show alimentary canal, oes, int; the septa;
blood-vessels (dors. vess, vent. vess.); and the nephridia (neph). Behind,
intestine removed to show ventral blood-vessel and nerve cord (ne. co) ; gl,
glands of esophagus; para, swimming feet; perist, peristome; perist. tent,
tentacles of the peristome ; ph, pharynx and its jaws; praest, part of head
lying above mouth. From Parker and Haswell.

165

166 ZOOLOGY

The execretory organs are little coiled tubes of which typi-
cally a pair lies in each segment (Fig. 161). The inner mouth
of the tube opens into the body-cavity, where it sucks in parti-
cles floating in the body-cayity. The wall of the tube, which
is richly supplied with blood-vessels, extracts from the blood
the waste products, thus purifying it. The inner end and
cavity of the tube is lined by little beating hairs (cilia) which
maintain a movement of fluids toward the outer end of the
tube. It is to be noted that the excretory tubes are repeated
in nearly every segment, for we have seen that in the higher
animals — Crustacea — tubes are found in various segments
but performing diverse functions. This is a law of evolution
of organs — at first a repetition of similar ones with a common
function and then a reduction of the total number with a special-
ization of function and structure to each.

The reproductive organs of annelids are relatively simple.
Although the sexes are separate in Polycheetes and in the
earthworm and its allies (Oligochetes) both eggs and sperm
are formed in the same individual; nevertheless any egg of
an individual is not fertilized by a sperm-cell of the same indi-
vidual. The egg and sperm-cells develop in the lining of the
body-cavity and when ripe, fall into the body fluid. They
are sometimes picked up by the excretory tubes and cast into
the sea, where fertilization occurs; but sometimes the ripe
individuals break in two in order to allow the sexual products
to escape. In certain annelids the escape of thé egg and sperm
occurs in thousands of individuals at the same hour, so that
the sea swarms with eggs and sperm; thus the chances of their
getting together are increased. The special case of Autolytus
is referred to on page 187. From the fertilized eggs embryos
covered with cilia arise, which swim free in the sea as they

ANATOMY AND PHYSIOLOGY OF ANNELIDS 167

develop. There is abundant food for them here, but the
danger is great, for the surface is constantly being swept by
fishes that live on the pelagic fauna.

The musculature of annelids has been treated of in the intro-
duction to this chapter. The nervous system is of the same
type as that we have studied in the lobster—a dorsal brain
and a double ventral nerve chain connected by a nervous ring
around the pharynx. From the ventral nerve-cord in each
segment branches go off to the two lobes of the paddles.

The sense-organs of annelicls vary greatly in the different
orders. In the earthworm they are few and simple. The
whole surface of the body bears sensory hairs, and as these
are the only sense-organs known in the earthworm they
are probably (in different regions of the body) capable
of being irritated by mechanical, chemical, thermal, or
luminous stimuli. Nereis, on the other hand, has special
sense-organs. Four eyes rest on the brain. Each is a cup-
like depression of the skin. At the bottom of each are the
special sensitive cells connected with a prominent nerve going
to the brain. The tentacles of Nereis are doubtless tactile, and
the palps probably have also a taste sense. Thus we see that
a carnivorous form like Nereis has well-developed sense-organs,
enabling it to find its prey; while herbivorous species, like
the earthworm, lack such special sense-organs. Each species
has organs agreeing with its needs.

CHAPTER XII

THE EARTHWORM: A STUDY IN SUBTERRESTRIAL
ORGANISMS

THERE is every reason for believing that the primitive organ-
isms lived in water, for we find the simpler organisms living in
water to-day. Indeed, the small ancestral organisms would
dry up if exposed to air. Whether the very earliest organisms
developed in fresh water or in salt water is uncertain and im-
material, but it is quite certain that the principal branches of
the animal kingdom originated in the sea, on or near the shore.
From the shallow seas their descendants passed on the one
hand into the depths of the sea and on the other either up the
estuaries and into the rivers or, in a few cases, directly upon
the land. Of the forms that thus came to inhabit fresh water
many have succeeded in reaching the shallow pools and small
streams which dry up during a part of the year. Such animals
have been forced, in order to protect themselves from desic-
cation, to penetrate into the muddy bottoms. This habit of
living in the ground is now common to many kinds of animals.
The elementary instincts with which the burrowing habit is
associated are, first of all, a love of contact and of darkness
and, usually, of moisture also. The food of burrowing animals
is usually any sort of organic débris and roots, but the higher
types, like the moles, feed on lower subterrestrial organisms.

Even at the seashore many kinds of marine animals have
acquired burrowing habits. Thus, many of the simplest

organisms, such as sponges, burrow into solid objects at the
168

THE KARTHWORM 169

bottom of the sea. Perhaps the commonest burrowers, how-
ever, are those elongated animals — elongated in association
with the burrowing capacity — that we call sea-worms. A
fuller account of many of them is given in another chapter.
Many of the Crustacea burrow and feed upon the burrowing
worms.

The burrowers of the land are the best known to us. They
have been derived from organisms that lived in fresh water.

Fie. 162.— Flash-light photograph of earthworm and slug crawling on a
pavement at night. Photo. by D. and 8.

Among the land burrowers are the earthworms; certain
Crustacea, like the crayfish; many insect larve; and a few
mollusks and vertebrates. In the present chapter we have
especially to consider the earthworm (Oliogocheta !).

Earthworms, as the name implies, are inhabitants of the
ground, through which they burrow and in which they gain
their food. They sometimes come to the surface at night in
search of companions and food (Fig. 162). Even during the
day in rainy weather they extend the anterior end of the body
out of their burrows. Earthworms, found on the surface at
other times, have, for the most part, been parasitized by a

1 oligos, few ; chete, hair.

170 ZOOLOGY

fly, and are in consequence weak or dying. During the day-
time, if the surface moisture permits, they lie near the mouth
of their burrows, probably for the sake of the sun’s warmth.
In this position they can be seen by looking down into the
holes. At such times they are often caught by birds. In dry
weather, or when the ground is freezing, earthworms burrow
deep to a moist stratum, or to below the frost-line, and hiber-
nate there.

Food. — Earthworms are omnivorous. As they burrow
through the ground, the earth is taken into the food tract, and
the digestible particles are dissolved out and absorbed as food.
Earthworms can, however, be fed upon green and dead leaves,
decaying wood, seedlings, bits of flesh, and even filter paper.
Earthworms have the habit of dragging into their burrows
leaves which they intend to devour. There the leaves are
moistened with a fluid excreted by the worm. This fluid
partially digests the food. After being taken into the alimen-
tary tract, the food reaches an organ of the canal known as the
gizzard. This part has thick muscular walls, and contains
in its cavity small stones; by the action of both the muscular
gizzard and the small stones, the food is ground up in much the
same way as are the grains of corn by the aid of stones in the
gizzard of a hen.

Resistance and Regeneration. — Earthworms have a re-
markable power of resisting certain untoward conditions.
Thus they may be kept for months in a moist vessel without
food, or with only filter paper, without starving. On the other
hand, they die in a dry atmosphere in a few hours, whereas
they may be submerged in water for several days without
injury. Very remarkable is their power of healing after injury.
If an earthworm be cut in two near the middle, and the halves

THE EARTHWORM 171

be kept under favorable conditions, each half may develop
its missing organs, so that two complete worms will result.
The anterior half of one worm may be attached to the hinder
end of a second worm by the cut edges, owing to the fact that
the cut edges grow together. This operation is called grafting.

Economics. — Earthworms are, to a certain extent, inju-
rious to vegetation, since they eat tender seedlings and roots;
but, on the other hand, they are almost indispensable to agri-
culture. Their burrows permit rain to percolate deep into the
ground, instead of running off on the surface. They keep the
soil loose, facilitating the penetration of the roots of plants.
The earth that passes through their bodies is ejected on the
surface of the ground near the openings of their burrows, and
is called a “ casting.””’ By means of castings the deeper-lying
earth is brought to the surface, and the surface layer of rich

earth, called “ vegetable mold,”

is in this way increased in
thickness by additions to its upper surface. The thickness of
the layer of mold which the castings of one year, if uniformly
spread out, would make has been estimated by Darwin to be
in England about two-tenths of an inch. Most of these
castings are merely taken from the deeper-lying mold, but
they are enriched by the intestinal secretions in passing
through the body of the worm. These intestinal secretions
are said to have the power of slowly dissolving sand and
thus of turning it into soil. Darwin says: “It is a mar-
vellous reflection that the whole of the superficial mold over
any smooth expanse has passed, and will again pass, every few
years, through the bodies of worms. The plow is one of the
most ancient and most valuable of man’s inventions, but long
before he existed the land was, in fact, regularly plowed,
and still continues to be thus plowed, by earthworms.”

df ZOOLOGY

Earthworms are also a source of disease. They burrow into
the carcasses of buried animals that have died of infection
and bring the disease germs to the surface, where they may
infect healthy animals. They are believed to carry the germs
of gapes — a worm parasitic in chicks.

Earthworms belong to the sub-kingdom of ringed worms
(Annelids!). The annelids are divided into two orders, one of
which lives chiefly in the sea and is called Pol’ycheta,? while
the other lives chiefly in fresh water or in the ground and
is known as Ol/igocheta. Earthworms belong to the latter
order. This order is distinguished, in addition to its non-
marine life, by the absence of foot-pads and parapodia, by
having few bristles, and by the absence both of tactile append-
ages at the head end and of gills.

The Oligocheta are either aquatic or terrestrial. The
aquatic Oligocheta are among the commonest inhabitants of
ponds and ditches, living sometimes in the mud and sometimes
at the surface of the water.

Tubifex * is common in slow-running brooks, and lives in the
mud of the bottom, forming tubes in it. The thread-like
bodies of the worm are stretched up beyond the surface of the
mud and wave in the water in graceful undulations. Often
the worms are so numerous that their reddish color gives a
decided tinge to the bottom. They thrive well in fresh-water
aquaria.

Dero ‘ is very common on the surface of ponds, particularly
in the midst of duckweed (Lemna), the leaves of which it
cements together to form a floating tube in which it lives, and
by which it is accompanied in all its migrations. Dero can

lannulus, a little ring. 3 tubus, tube ; facere, to make.
2 poly, many ; cheta, hair, 4dero, to skin or flay.

THE EARTHWORM 173

also be told by the sort of funnel at the hinder end of the trans-
parent body, from the margins of which finger-like filaments
arise which aid in respiration (Fig. 163).

Fic. 163.— Dero, the duck-weed worm. Enlarged. After Reighard. The
lettering is as follows: or., mouth; phz., pharynx; oe., esophagus; sg.o.,
segmental organ; in., intestine; pav., pavilion or tunnel; dg.app., finger-
like appendages. From Reighard.

Nais! does not construct tubes, and it has no respiratory
filaments at the hinder end of the body (Fig. 164). It also
has eyes; while Dero has none. Both Dero and Nais have
the interesting habit of reproducing by dividing the body trans-
versely. Jn the middle of the body tentacles hegin to arise,
a new mouth is formed, and the worm constricts into two.
Indeed, sometimes several new heads may be forming in the

1 nats, a water-nymph.

174 ZOOLOGY

midst of a single worm. This habit is of advantage not only
in multiplying the number of individuals of the species, but
also as a means of protection. For if, by chance, the larva
of the water-heetle (Dytiscus) seizes a Nais and bites it in
two, the part which es-
capes can go on devel-
oping new individuals.

The terrestrial Oligo-
chete include the com-
mon earthworm and, in
addition, worms that
live on the seashore be-
tween the tides and
even in places which are
rich in vapors of am-
monia arising from de-
caying stuff.

There is another

Fic. 164.— Nais. a, mouth; 0, anus; ¢, in- group of fresh-water

testine. From Leunis. worms which is closely
related to the Oligocheta but which has a very different
” are flattened
worms, which, like the earthworm, show metamerism; that
is, there is a repetition of the internal organs. They are also
segmented; that is, the body has external rings, although
they may be obscure. One segment does not, however, as in

appearance. The leeches, or ‘“ bloodsuckers,

the earthworm, correspond with one set of internal organs
(metamere), but there are three, four, or five segments to a
metamere. Teeches have no appendages and no bristles;
but they have a sucking disk at the posterior end of the body
for the purpose of sticking to things (Fig. 165). They usually

THE EARTHWORM 175

have a smaller, anterior sucking disk around the mouth, which

may or may not be provided with teeth, for the purpose of

cutting through the skin. When
there are no teeth, the pharynx
can be thrust out, forming a pro-
boscis. With a few exceptions, all
leeches live in water; but in Cey-
lon there is a land-leech which
lives in foliage and attacks man
and other animals. Other leeches
may live in damp places at a con-
siderable distance from water.
Such a leech has been described in
this country that was dug up ina
garden at a point about 60 metres
from the nearest rivulet, where
it was feeding on earthworms.
Leeches suck the blood of fishes
and other aquatic animals.
Certain kinds devour worms, in-
sects, and other small creatures.
Rarely do they feed on plants.

The commonest of the larger blood-
suckers of our waters is Nephelis,’

which is not distinctly segmented.

It varies from black to slate color,

spotted. It lives in running water,

{. Pontobdella 2. Clepsine

Fic. 165. — Two leeches, Clepsine,
found in ponds, often parasitic
on frogs; and Pontobdella, a
marine species living on fish.
From Parker and Haswell.

and is sometimes striped or

ditches, and ponds.

Clepsine ? is a very flat and broad leech, which is common under

floating wood. It feeds on snails and creeps like the inch-worm.

The female carries its young attached to its under-surface (Fig. 165).

1 Nephele, wife of Athamas.

2From klepto, to steal.

176 ZOOLOGY

In conclusion brief mention must be made of certain worm-
like animals still more distantly related to the earthworm.
The first of these is marine, but has the same slow-moving,

burrowing habits as the earthworm. These animals have

become more modified in connection with their burrowing

habits than the earthworm, for they

Gephyrea.!
This group con-
tains several rather

rare animals, some of

Fia. 166. — Phasco-
losoma, a Gephy-

which are edible, and

are held in esteem by

rean. One-fourth
nat. size. From the Chinese. One of
Leunis.

the commonest is
Phascolosoma,? which is a tough but
smooth-skinned, cigar-shaped worm,
which one can dig up on our sandy sea-
beaches (Fig. 166).

from the other a great proboscis ending

One end is pointed;

in tentacles surrounding a mouth can be
extruded. Another species found on our
beaches after a storm, something like a
small cucumber in shape and size, has a
row of bristles at each end, indicat-
ing its relationship with the bristle-
bearing worms. This striking species,

lgephyra, bridge ; because they were once
considered to bridge the gap between holothu-
rians and worms.

2 phaskolos, sac; soma, body.

have lost not only their

appendages, but in the adult stage even the
segmentation of the body. This is the class

ant set

Y a

Fia. 167.— Echiurus. About
one-half nat. size. prob,
proboscis; ant. set, anterior
sete; post. set, posterior
sete. After Greef, from
Parker and Haswell’s Text-
book.

THE EARTHWORM 177
Echiurus,' is segmented when young like Nereis, but eventually
it loses its segmentation (Fig. 167).

Possibly allied to the Gephyrea is the group of Bryoz’oa,?
or moss-animals. These are noteworthy from the fact that

Fic. 168. — Pedicellina americana, an endoproctous bryozoan. A colony,
magnified 15 diams. Photo. of living animals by W. H. C. P.

they are compound, many individuals budding off from one

another, as in plants. They are found abundantly both in

the sea and in fresh water. There are two main groups, the

End’oprocta (Fig. 168), in which the individual consists of a

lechis, adder ; oura, tail. 2bruon, moss; zoon, animal.
N

Fic. 169.—Bugula turrita, a marine ectoproct. A colony, magnified 1.5
diams. Photo. of living animals by W. H.C. P.

Fie. 170.— Plumatella polymorpha, a fresh-water ectoproct, magnified 1.5
diams. Photo. of living animals by W. H. C. P.

THE EARTHWORM 179

long stalk and a “head” or body proper; and the Ect’o-
procta (Figs. 169, 170), usually without such a stalk. The

Fic. 171.— A, entire shell of the brachiopod Magellania from dorsal aspect ;
B, from left side; C, interior of ventral valve; D, of dorsal valve. ad.m,
impressions of closing muscle; b, beak of shell; c.p, ‘‘ cardinal” process
of shell; d, plate closing the ventral shell; d.m, impression of muscles that
open the valves; d.v, dorsal valve ; f, hole through which stalk passes to at-
tach shell to the rock ; p.m, impression made by muscle that protrudes the
stalk; s, socket for tooth (t) of ventral valve; s./, loop to hold tentacles ;
sp, partition or septum ; v.v, ventral valve. From Parker and Haswell.

Ectoprocta are the commoner. The marine species form lace-
like mats on seaweed, or stand up as branching, bushy colonies

180 ZOOLOGY

(Fig. 169). Some of the fresh-water forms make loose, antler-
like colonies (Fig. 170), while others lie on the surface of a
more or less spherical mass of jelly which they have themselves
secreted.

The lamp-shells (Brachiopoda) are a vanishing class. Their
fossil remains crowd the rocks almost from the first appearance
of organic remains. While
thousands of fossil species
have been described, only
about 125 living species
are known, — all marine.
Although the individuals
are usually numerous in
localities where they occur,
the localities are few. In
our country they are found
on the coast of Maine and
Fic. 172.—The brachiopod Magellania, near Cape Hatteras. The

with the ventral valve removed. c.p, the Ri

“cardinal’’ projection of shell; Uph, the Brachiopoda have a two-

bearer of the tentacles ‘‘lophophore”’ ; valved shell like a clam,

lph, its coiled arm, the tentacles removed

from right side; mth, mouth. From Par- but the valves are not

eae right and left, but dorsal
and ventral (Fig. 171), and consequently have nothing to do
with the shells of mollusks. The body somewhat resembles
two arms

that of a single individual of a Bryozoan colony
stand up on the right and left of the mouth and these are
crowded with tentacles whose cilia create a vortex in the water,
bringing small particles to the mouth (Fig. 172). The food
canal is bent like a U, the loop of the U being at the hinge of
the valves, half buried in the sand, while mouth and arms are
elevated into the surrounding water. On account of the fact

THE EARTIIWORM 181

that Brachiopoda originated so long ago their affinities are
hard to decipher. They seem to be more closely related to
the Annelida and Bryozoa than to the Mollusks, but they lie
near to the ancestral stem whence all of these branches have
arisen.

CHAPTER NXIII

NEREIS: A STUDY OF LIFE ON THE SEASHORE

More than any other part of the earth the seashore has been
the place of origin of the diverse types of animal life. The
reason for this is not far to seek if it be granted that a diver-

Fic. 173. — The rocky shore, worn smooth by the beating of the sea.

sity of environment favors the origin of a great variety of forms
of life. When we realize fully how admirably each organ-
ism is fitted to some particular niche in nature, we cannot
doubt that the more varied the environment, the more varied

the life. Some of the niches which the seashore offers may be
182

NEREIS 183

recognized by any one who travels along the coast. We may
see abrupt rocky promontories whose base stands in many
fathoms of water. Against such a wall of rock the restless sea

‘a? ab Bhs

Fic. 174.— A bit of the rocky shore, and its adhering organisms. At the left
some brown seaweed, at the night bunches of mussels lying in crevices of
the rock, in the centre and above barnacles adhering to the rock.

is ever hurling itself, wearing the rocks smooth by its repeated

beatings, and yet the crevices of these same rocks are occupied

by many kinds of animals. These are able to maintain
their place either by being rooted to the rocks, like the

184+ ZOOLOGY

hydroids, the sponges,! the mussels, and the barnacles (Fig.
174), or else they have some device for clinging fast, as
in the case of the starfish, and many snails and crabs. At
the opposite physiographic extreme we find the sea penetrating
as a harbor deep into the mainland.? The boundary between
the sea and the land is in these cases often very uncertain

Fic. 175.-—— An enclosed harbor or arm of the sea penetrating deep into the
mainland.

because the semiaquatie plants grow far out into the water,
forming the edge of a salt-marsh. Here twice a day the sea
bottom is exposed to the air by the retreating tide, and terres-
trial animals wander out upon it to feed. In this situation the
permanent animals are those that burrow in the mud or pene-
trate between the roots of marsh-grass or swim about on the
surface of the water (Fig. 176). These animals feed on the
débris that floats on the surface of the water or else crawl
about on the bottom to browse on the alge which flourish
1 See Chapter XIX. 2 Wig. 175.

NEREIS 185

there. These animals of the quiet harbor are mostly weak and
defenceless ; they seek chiefly to avoid their enemies by retreat-
ing from them. Between the rocky promontories and the
salt-marsh exist all possible gradations, and in each different
habitat one will find a totally different fauna.

In this chapter we shall consider an animal living in the
bottoms of harbors, known as the sandworm (Ne’reis). It

Fic. 176. — An estuary with a salt-marsh in the distance where semiaquatic

plants grow far out into the sea.
abounds in sandy or muddy beaches at or below low-water
mark and is especially abundant where tidal currents flow
swiftly, thus constantly renewing the water, oxygen, and food
particles. Nereis is, for the most part, a lover of darkness
and contact. Hence it inhabits burrows which it lines with
a secretion of mucilaginous consistency that binds together
the particles of sand or mud. For a week or two in summer,
however, during the breeding season, Nereis gains a new set
of instincts. It leaves its burrows and swims about near the
surface of the sea.

186 ZOOLOGY

Nereis lives on both plant and animal food.

To capture its

prey it thrusts out a long proboscis, provided with two power-

[___..___J it swims free at night
se ame So cae during the breed-
idonotus, the
scaled worm. ing season. Such a
Nat. size, f :

Photo. by W. favorite with fishes
H.C. P. naturally makes ex-

cellent bait, and is well known to

¢

fishermen under the name ‘ clam-

worm” or “ sancworm.”’ _,
We have seen that Nereis lives

for a short period each year a free

life, swimming in the sea. Accord- ~

ingly its body is divided into rings
of muscle enabling it to writhe.
Locomotion by writhing is further
facilitated by the existence of a
pair of appendages (parapodia) on
each segment. The appendages are
nearly alike on all the segments of
the body. They diminish in size,
however, toward the tail. Cor-

1 See Fig. 160.

glove may be rolled inside out.

ful jaws. The thrusting-out consists essentially
of a rolling inside out,—just as the finger of a
When the pro-
boscis is rolled in again, the jaws, retaining their
grip on the food, carry it into the food canal.+
While many kinds of small animals serve Nereis
as food, it is itself devoured by various fishes
which dig it out of the sand or capture it when

Fic. 178.— Aphrodite, a sea-mouse.
From Johnston.

NEREIS

187

related with its carnivorous life are its powerful jaws and well-

developed sense organs on the head.
feelers, and tasting organs.

These consist of eyes,

From such forms as Nereis there has developed a long series

of worms inhabiting the sand or constructing special tubes

At the end of the
series there are included worms that live
permanently in thin limy tubes and have
lost the locomotor and sense organs of

in which to live.

Nereis. Weshall examine in order some
of these different worms and shall ob-
serve certain modifications in structure
which they undergo in relation to their
modified life.

But first we should know that not all
free-living,
Nereis.

marine annelids are like
On the one hand we have forms
that do not burrow at all in the sea
bottom, but which lie so close to stones
and shells that they seem to form a
part of them.
with scales, and they are known as
scaled-worms (Fig. 177).
members of this group, known as “ sea-
mice” (Fig. 178), the scales are hidden
from view by long bristles.
tles are merely greatly enlarged represen-

Their flat body is covered

In a few

These bris-

Fic. 179.— Autolytus, a
representative of a fam-
ily of Polycheta in
which the animal buds
off male or female in-
dividuals from its hinder
end. bud, head of the
budded individual.
After A. Agassiz.

tatives of the bristles found on the swimming pads of Nereis.

A second form (Autolytus!, Fig. 179) lives in little tubes

attached to seaweeds and hydroids.

Its method of repro-

1qutos, self ; lwo, to separate ; hence, self-separating.

188 ZOOLOGY

duction is remarkable. The same method, however, occurs
in different guises in many other free-living annelids. In this
form the paddles or parapodia at the anterior half of the
animal are different from those at the posterior half, for the

latter are large and fitted for swimming.

Se . Eventually one of the middle segments of
(rye
}
(Ey

the body becomes transformed into a head,

i 1
| 7 bearing eyes and tentacles; then the whole
: f | of the hinder half breaks off ‘of itself.”

Hbts The newly formed head is now the head
ie end of the new individual. This individ-
} ual leads a different kind of life from the
half which remains in the tube, for it
| ‘swims freely in the water. The separated
is) | individuals are either male or female,
_{ whereas the part which lives in the tube

Fa. Ko. —Clemenelia: never produces eggs, but merely forms a
straw-worm. The an-
terior segments only

are shown. After M. to form a sexual individual.
Lewis.

new tail every time the old tail is cut off

We have now to consider the non-loco-
motor or sedentary Polycheta. The first of these is not
greatly changed from the free-living type. This is Cly-
menella (Fig. 180), which looks like a reddish, jointed
straw. It builds tubes of agelutinated sand in which it
spends much of its life. Parapodia occur on each segment,
but they are very small. Amphitrite (Fig. 181) builds firm
tubes of sand. Its parapodia are rudimentary behind. The
function of respiration is carried on by three pairs of parapodia
which are borne on the head. These are immensely enlarged,
forming blood-red gill tufts. Amphitrite has many close
allies that show different stages of degeneration. Thus the

NEREIS 189

worm known as the “ blood-spot ” (Polycirrus, Fig. 182) is
reduced in size, and instead of gill tufts it has a large number of

Fig. 181.— Amphitrite, removed fromits Fic. 182.— Polycirrus, the blood
tube. Nat. size. Photo. by W. H.C. P. spot. Nat. size. Photo.

thread-like organs, the cirri, at the head end. Certain species,
such as Cistenides (Fig. 183), form complicated tubes out of
grains of sand cemented together in a regular arrangement so
as to form a firm wall.

Finally, Serpula! secretes crooked, round, calcareous tubes,
which may be found adhering to stones near low water

1From serpens, serpent.

190

ZOOLOGY

(Fig. 184). From the mouth of the tube the head, with its tenta-
cles, may be protruded, but it quickly retracts from danger

Fic. 183.— Tube of
Cistenides slightly
enlarged.

and closes the opening of the tube, as a
marine snail does its shell, by means of an
operculum or lid.

We have now to consider some groups of
worms which differ from the annelids in not
having the trunk composed of a series of
rings. The first of these is the group of
nemerteans (Nemertini, Fig. 185). It in-
cludes chiefly marine animals, of some-
what flattened form and great length,
even as great as thirty metres. They
protrude a long, slender proboscis. The
body readily breaks up into a great many
pieces when the worms are handled roughly,

but since each of the pieces may regenerate into an entire

worm, this behavior

is not self-destruction,
but self-preservation.
These worms are es-
pecially abundant in
the sand of the sea-
shore, although land
nemerteans occur.
The other two groups
of unringed worms
have gained a parasitic
habit, and in conse-
quence have become
much modified in form

|

Fic. 184.—Serpula tube on a bit of oyster shell

that is perforated by the boring sponge.
tube lies in the centre of the figure.

size.

Photo. by W. H, C. P.

The
Nat.

NEREIS 191

and structure. Such is the case with some of the round-
worms. Some of these are thread-like, live in springs
or pools, and are regarded by the uninitiated as ani-
mated horsehairs. Others are spindle-shaped, as, for example,
the “vinegar eel” and the
roundworms that are common
in stagnant water. Others
live in the food canal, as, for
example, the stomach-worm
(As’caris) of the horse and the
pinworm of man. Others sfill
penetrate into the muscles,
and cause great pain and often
death. Such is the pork-
worm (Trichi’na!), which gets
into man by means of un-
cooked pork, multiplies in the
food canal, migrates in great

numbers into the muscles
and encysts itself there (Fig.

Fia. 185. — Cerebratulus, a cream-col-
ored nemertean. Head end at upper
186). part of figure ; mouth turned toward
F observer, proboscis retracted. In-

The second group that is stantaneous photograph of living

partly parasitic is that of the worm by W. H.C. P.

flatworms. Some flatworms live free in ponds. They will be
found abundantly among plants taken from small ponds in the
summer and autumn, and are commonly known as Plana’ria +
(Fig. 187). They may be recognized not only by their flat-
tened form, but also by a curious proboscis which protrudes
from the middle of the under side of the body and bears a
mouth at its tip. These creatures have a marvellous power

1 thriz, hair. 2 nlanus, flat.

192 ZOOLOGY

Fic. 186.—Trichina. A, encysted form in muscle of pork; B, female; C,
male; bh, envelope of cyst; cy, cyst; de, male duct; e, embryos; f, fat
globules; h, testis; mf, muscle fibre ; oe, pharynx ; ov, ovary ; no, opening
to egg duct; zh, cell masses in intestines. After Claus.

NEREIS 193

of regeneration, so that every piece into which a worm is cut
will reproduce an entire one (Fig. 188).

Other flatworms are parasitic, such as the liver-fluke of the
sheep (Fig. 189). This destructive parasite has a complicated
series of stages to go through before
it becomes adult. Thus the flukes
in the liver of the sheep produce % +}
eggs which develop into embryos.

These embryos get out of the liver \
into the food canal, and thence to
the exterior. If they are deposited
near a pool of water, they may
develop further; otherwise they
must die. In the water a ciliated
larva! hatches from each egg, swims
about for a time until it finds a
fresh-water snail, bores into it, and
encysts itself there. In this en- 9%) 2
cysted stage the worm is known as “
a ‘“sporocyst,” because it is full oe
of germs (spores) of a new genera-
tion.2 The spores develop in the

snail into curious organisms, a sort

._ , Fic. 187.— Species of fresh-water
of secondary larvee known asredia.* planaria. 1, Dendroccelum

The redia may produce, by a kind !acteum, cream color; 2, Pla-
. gD Pals naria maculata; 3, head end
of internal budding, new rediz, and of same to show light streak.

so on repeatedly, until at last,on the “fter Woodworth.
death of the snail, or from some other cause, the last generation
of redize produces liver-flukes.!. The young liver-flukes wriggle
1 Fig. 190, A. 2 Fig. 190, B. 3 Fig. 190, C.
4 These, while young, have tails, and are called “ cercaria,”’ Fig. 190, D.
oO

194 ZOOLOGY

out of the snail, attach themselves to damp grass, lose their tails,
and encyst themselves. If these cysts be eaten by a sheep,
they develop in the sheep’s body into an adult liver-fluke

Apr.4,
March 13

Dec.10 Feb.14
i Feb.5. £2:
Jan.25.
Fic. 188. — Showing results of cutting Planarians into two pieces; the pieces
develop into entire animals. After Morgan.

(Fig. 189). Thus the stages which we can recognize in the liver-
fluke are : —
First generation: egg from liver-fluke, larva, and adult sporocyst.
Second generation: redia (this may be several times repeated).
Third generation: ‘‘cercaria’’ larva, encysted larva, and adult
liver-fluke.

NEREIS 195

Another flatworm is such an abject parasite that it has lost
most of the organs usually possessed by worms. This is the
tapeworm (Fig. 191). When the eggs of the tapeworm are
taken into the body of an herbivorous animal, the embryos
develop there for a while and then stop.
When flesh containing these embryos is
eaten by a carnivorous animal, the em-
bryos attach themselves to the food canal
of their host by means of hooks and
sometimes also by means of four suckers.
The head thus constituted (called scolex)
produces, by rapid growth, a long chain
of segments, each of which is full of germs. pas
: me Ne Fig. 189. — Distomum,
The chain, or “ tape,” absorbs fluid food, the liver-fluke. Nat.
which soaks through its body-wall. As ‘ize. #zer, excretory

é pore; mo, mouth;
the segments at the older end of the ani- — repr, reproductive ap-
erture ; sckr, posterior

sucker. From Parker
of the alimentary tract to be picked up, and Haswell.

™mo

7Tepr

sche

”)

mal mature, they are set free and pass out

perchance, in the food of an herbivorous animal or else to
perish.

The tapeworms are remarkable because they show to what
extremes of degeneration a parasite may go. They have
lost so fundamental an organ as the food canal. All com-
plex sense-organs and organs of locomotion are lacking, and
the worms have become mere sacs of reproductive cells.
This is the usual tendency of internal parasites, — to multi-
ply enormously their means of reproduction so as to increase
the chance of infecting another host. On the other hand,
the sense-organs, brain and nervous system, and muscles
tend to degenerate because the parasite has little use for
them.

196 ZOOLOGY

The economic importance of parasitic worms is very great.
Thus, although no great epidemics of the flukes have occurred
in this country, a million sheep are annually lost by this para-
site in Great Britain; and in 1879 and 1880 it was estimated
that three million sheep died annually in England alone of

Fic. 190.— Development of Distomum. <A, ciliated larva; B, sporocyst con-
taining developing redie ; C, redie, containing a daughter rediz and embryo
liver-flukes; D, free-swimming, tailed larva of liver-fluke; b. op, birth
opening ; ent, food canal of redia; eye, eyespots; gast, young redia; germ,
mor, early stages in formation of the embryo liver-fluke ; int, intestine of
larval liver-fluke ; ws, cesophagus; or. su, oral sucker; pap, head papilla of
ciliated larva, 4; ph, pharnyx; proc, processes of redia; vent. su, ventral
sucker. After Thomas.

this parasite. In Buenos Ayres, during 1882, a million sheep
died of fluke disease. By great care in preventing infection,
especially during damp seasons, we may be able to prevent any
such disaster in this country.

NT

NEREIS

Fig. 191.— Tenia solium, the human tapeworm. Entire specimen, about

Cap, head. After Leuckart.

natural size.

CHAPTER XIV

THE ANATOMY AND PHYSIOLOGY OF MOLLUSCA:
ILLUSTRATED BY THE SNAIL

General Form of the Body.— Mollusks are non-segmented

¢

animals; Cuvier spoke of them as ‘‘ massive ” animals, since
their form is usually short and stout in strong contrast with
that of the elongated worms. They have a right and a left
side and a dorsal and ventral surface, but in many mollusks,
as in the snail, the body is coiled into a close spiral, so that the
primitive bilateral symmetry is obscured. In view of the fact
that of the three main groups of the mollusks — lamelli-
branchs, gasteropods, and cephalopods —two are almost
exclusively symmetrical and the third (gasteropods) con-
tains a great number of symmetrical forms, we may conclude
that bilateral symmetry is the primitive condition for mollusks
and that the spiral of most gasteropods is a special and recent
modification. Such a spiral shell was probably originally
a conical cap over the body. As this cap was built up at the
edge to accommodate the increasing bulk of the growing young,
it elongated until finally it formed along, unwieldy cone. The
most convenient and compact form for storing such a body is
a spiral or helix. This is the condition of the shell of most
gasteropods; it is well illustrated by the common snail.

The soft body of the mollusk is usually supported and pro-
tected by a shell (Fig. 192). This is formed from the skin, here

called ‘‘mantle,”’ whose glands pour out a secretion that
198

ANATOMY AND PHYSIOLOGY OF MOLLUSCA 199

hardens in contact with the air or water. Increase of the
shell takes place chiefly at the margin. Here the three layers
of which the shell is composed are secreted — the prismatic
layer (Fig. 192, prs) made up of prisms whose axes are per-
pendicular to the sur-
face, the thin outer
varnish which serves to
protect the shell from
chemical action and
bears most of the char-
acteristic coloration of
the shell (pre), and, in-
side the prismatic layer,
thin sheets of lime (7)
which are secreted not

only at the margin, but ieee

farther back on the Fic. 192.—Cross-section of the shell and
mantle of Anodonta. ct, connective tissue

mantle. The shell of a layer of the mantle ; ep. 1, itsouter cell-layer ;
bivalve has essentially ep. 2, itsinner cell-layer ;n, ‘mother of pearl”
vus layer of shell; prs, prismatic layer; pre,

the same structure. ‘“periostracum ’’ or outer varnish, also called

The skin of mollusks ‘epidermis.’ From Parker and Haswell.

is relatively soft, but in land species like the garden snails
it gains a considerable thickness and is, moreover, abun-
dantly provided with glands which pour out a mucus over
the. skin when it becomes too dry, thus preventing further
loss of water. The outer wall of the body has always
an organ characteristic of mollusks; namely, the mantle.
In lamellibranchs this is a great pair of folds arising from near
the mid-dorsal line of the body and reaching down on each side
to the mid-ventral line. This is the organ that secretes the

two valves of lamellibranchs. In gasteropods (Fig. 193) the

200 ZOOLOGY

mantle fold is less conspicuous because it is hidden deep in
the spire, but the edge of it may be seen protruding from the
margin of the aperture. In the naked mollusks— eg. the
slugs — the mantle appears as a reduced cap on the back of
the animal.

Appendages are not present in most mollusks; locomotion
is effected in the snail by the whole ventral part of the body

a pl,

Fic. 193.— The snail Helix aspersa, fully extended from the right. After
Howes. a, anus at edge of mantle; plz, the breathing pore; s, shell;
p, edge of ‘“‘aperture”’ of shell; ga, the genital aperture ; ¢;, one of the two
tentacles carrying the eyes; ¢t, anterior tentacles; i, upper lip. From Lang.

—the foot. In these animals a great mucus gland lies just

above the skin of the foot and pours out, from near the anterior

part of the body, a stream of mucus over which the animal
glides. The different modifications that the foot shows in
different mollusks are considered in the following chapters.

In contrast to the foot the head bears very characteristic

appendages — the tentacles, which can be rolled out of

harm’s way or be stretched to an extraordinary distance.
Organs of Nutrition. — The different species of mollusks feed

on almost every kind of organic stuff, from the fine organic

débris suspended in water to the succulent green leaves of

ANATOMY AND PHYSIOLOGY OF MOLLUSCA 201

gardens, and even on live animals, including those of their own
species. In snails the mouth lies in a large head bearing
various sense-organs. Just inside the mouth a short gullet
leads to a tough pad upon which is a file-like rasping organ
called the radula (Fig. 194). The teeth in one cross-row are not
all alike as in a file, but vary in a complex way that differs in

Fic. 194.— The snout of a snail cut vertically and lengthwise to show the
mouth and rasping organ. 1, Dorsal wall of head; 2, mouth; 3, jaw; 4,
radula ; 5, cartilage of tongue ; 6, muscular wall of pharynx ; 7, muscles run-
ning from pharynx to ventral wall of head ; 8, space in head for withdrawal
of tongue; 9, pocket for radula; 10, esophagus; 11, opening to salivary
gland ; 12, fold behind radular pocket. From Lang.

different species; the successive cross-rows are, however, very

similar. The teeth are composed of a tough, hard substance

(chitin), but the front rows, which are those that are in action

at any time, eventually wear off and are replaced by new

teeth that push forward. During feeding, the hard edges of
the mouth or “ jaws” are protruded, and the food is dragged
into the mouth and cut into small pieces which then pass on to
the fleshy pad, where they are rasped or grated by the radula.
Thence the food passes through an cesophagus to an enlarged

202 ZOOLOGY

part of the food-canal called the crop. On the crop lie the
salivary glands (Fig. 195, 10), and the first stages of digestion
occur here. Beyond the crop is the stomach (14) into which
opens the great digestive gland (17). Here is done the main
work of rendering fluid the usable parts of the food; the di-
gested portion enters into the blood, the unusable portion
passes through the intestine to the anus (18) which by a loop
is brought not far from the head, so that it may be exposed
outside of the shell when the animal is expanded (Fig. 193).
Thus we see that the striking peculiarities of the food-canal
are its radula, its huge digestive gland, and its U-shape.

The digestive organs of the lamellibranchs lack the radula
and crop, but there is an enormous liver in the midst of which
the food-canal seems to lie. The anus is situated at the oppo-
site end of the animal from the mouth. In the case of cepha-
lopods there are jaws and a radula; also the large digestive
gland occurs and the anus lies well forward. In their diges-
tive apparatus the cephalopods closely approach the gastero-
pods.

Organ of Respiration.—In most aquatic gasteropods
there is at least one gill (occasionally two) lying close to the
inner wall of the mantle cavity (Fig. 196). The gills consist
of numerous finger-like processes in which the blood-vessels
run. Water that is brought into the mantle cavity bathes
the gills which extract oxygen from it. In cephalopods are
one to two pairs of plume-like gills lying in the mantle cavity.
In common snails on the other hand, owing to their terrestrial
life, the gill is wholly wanting and the whole mantle cavity
becomes a lung richly provided with blood-vessels. As stated
elsewhere, air-breathing mollusks can respire through the whole
surface of the body.

203

ANATOMY AND PHYSIOLOGY OF MOLLUSCA

Organs of Circulation.—In mollusks there is a dorsal heart

usually consisting of two chambers: one, the auricle (Fig. 196,

aur), receives the blood from the respiratory organs ; the other,

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Ssyed [B1oA0Ss UL ‘PUBLE VANSOTIP ‘[] + SpUBl[D AIVAT[eS ‘OT OOF OY} Jo ofosNUl “6 + VINPBI LO}
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‘7 ‘SOMOP{JO}FW ‘opls JUS oy} WIJ poMoLA PUB 4NO popooSsIp ‘XIJOH JO oqn} pooy — "GET ‘OL

the ventricle (vent), pumps it onward to the different parts

In the snail the circulation is as follows: The

of the body.

204 ZOOLOGY

blood that is forced out of the ventricle finds almost immedi-
ately two paths open to it; one large vessel (post. aort) goes
to the digestive gland, the intestine, and part of the repro-
ductive organs, while the other vessel (ant. aort) leads to the
main muscles of the head and foot, the stomach and crop, and
to such of the reproductive organs as are not supplied by
the first artery. Over each organ the artery breaks up into
the finest capillaries so as to come into most intimate contact
with the tissues, where it does its work of receiving or convey-
ing fluid food and oxygen. Beyond, these capillaries flow
together into veins by which the blood is carried to the
mantle chamber or lung. Here is another capillary system
in which the blood is aerated and out of which it is collected
into a large vein that leads directly to the auricle of the heart.

The blood of the snail, as of most other mollusks, is color-
less. However, on exposure to the air, so that it can absorb
oxygen, it turns slightly bluish. This change of color is due
to the oxidation of a substance that carries oxygen from the
respiratory surface to the tissues, just as the red coloring matter
(hem'oglobin) of our blood does. The oxygen carrier of
mollusks is called hem’ocyanin. A few mollusks have also
hemoglobin in the blood.

Fic. 196. — Dissection of a large marine snail, Triton. The mantle cut along
dorsal line leaving gill on left flap and rectum on right, pharynx, crop, and
kidney cut into to show structure. an, anus; ant. aort, artery going to
head ; aur, auricle (receiving chamber) of heart; buc, cavity of pharynx ;
cer. buc. con, nerve connecting pharynx to brain (cer. g) ; cten, gill; int, intes-
tine ; 1. buc. g, left pharyngeal ganglia; Ll. sal. gl, left salivary gland; neph,
kidney and its opening (neph. ap) ; od, odontophore ; oes, esophagus, cut at
oes’; osph, ‘‘osphradium,”’ a taste organ; ovid, oviduct; pluer. g, ganglion
supplying the viscera ; post. aort, artery to viscera; post. oes, part of cesoph-
agus behind crop; rad. s, radula sack; rect, rectum; sal. du, salivary
duct ; siph, siphon; supr. g, ganglia above viscera; tent, tentacle and its
nerve, tent. n; vent, ventricle of heart.

regt 9
ANATOMY AND PITYSIOLOGY OF MOLLUSCA 205

Jue
ouc
é buc.g rads
oes’ sal.diu

cerbuc.con
oes

206 ZOOLOGY

Organs of Excretion. — Mollusks have well-developed kid-
neys which are paired in most symmetrical species; but in
unsymmetrical species, like most gasteropods, only one is
present. In the snail the kidney lies close to the heart. It
opens on the one hand into the body-cavity surrounding the
heart and, on the other, into the mantle-cavity near the anal
opening behind the right eye-stalk.

Organs of Reproduction.— The sexes in mollusks are
usually separate, but in land-snails the eggs and sperm-cells
are produced in different parts of one and the same gland.
The eggs on their way out receive a large amount of albumen
from a gland, and further down in the oviduct an egg membrane
is secreted. The eggs of land-snails are laid at various times
of the year in bunches in moss or under boards and leaves, and
are clear, translucent little spheres about two millimetres in
diameter.

Musculature. — The whole skin in the snail is highly muscu-
lar, but the muscles gain their greatest importance in the foot,
where they assist in locomotion. Important muscles run to
the head from the visceral region, and it is by them that the
head is retracted into the shell (Fig. 195, 5-7).

Nervous System.— The nervous system of mollusks is very
different from that of annelids and Crustacea. There are a few
pairs of knots of nervous matter or ganglia. The two mem-
bers of a pair are united by nerves, and each ganglion is con-
nected with the brain. The brain is a pair of ganglia (Fig. 196,
cer. g) lying over the esophagus. It sends out nerves forward
to the various sense-organs of the head and backward to a
pair of ganglia lying just below the cesophagus and to a second
pair lving in the foot. These lower ganglia receive nerves from
the skin and its muscles, and from the various viscera. Thus

ANATOMY AND PITYSIOLOGY OF MOLLUSCA 207

the whole nervous system is characterized by the compactness
of its central ganglia.

Sense-organs. — The sense of touch seems to reside in all
parts of the skin, but is best developed in the tentacles. Snails
have a delicate chemical sense. Those that live in water
will direct themselves toward a bit of food when a current
from the food bathes their bodies. A land-snail will apparently
smell food several centimetres away. The chemical sense
seems to be located either near the opening of the mouth,
or, a8 in some marine snails, in a special organ located on the
mantle wall and known as the osphradium (Fig. 196, osph).
Eyes are placed in the garden-snail at the tip of the upper
tentacles. The eye, which can be retracted into the tentacle,
consists of a nearly globular cup containing a central lens and
a retina. It is doubtful whether, despite the long-stalked eye,
snails can see far; indeed, they are nocturnal animals and live
in dark places during the day, so that they could not make
use of a very delicate and perfect optical apparatus. Eyes
occur also in lamellibranchs and cephalopods. They are
numerous on the mantle of the scallop, and the squid has a
pair of very perfect eyes. As for hearing, there is little evidence
that snails have this sense. The ‘“ otocysts” that are found
in most gasteropods are probably (like the otocysts of higher
crustacea) organs of equilibrium.

CHAPTER XV

THE SLUG: A STUDY IN ANIMAL BEHAVIOR

Every movement that an animal makes is a response to
some stimulus applied to its contractile substance. This
stimulus may be applied directly to the contractile substance;
as, for example, when a muscle is pinched. Thus if we pinch the
muscle of a frog’s leg after the leg has been removed from the
body, the muscle that has been irritated will contract. The
stimulus may, however, be applied indirectly, as when we
dodge a ball moving near us. In this case the sight of the ball
stimulates the eye, a message is sent to the brain and from
the brain to the muscles which produce the dodging. In either
case it is clear the movement results from some stimulus.
With the exception of a possible origination of a stimulus in
the brain itself all movements are reactions to some external
stimulus. Now the stimuli which affect us are those changes
in the external world for the appreciation of which our body
is provided with certain parts called sense-organs. We have
a sense-organ for receiving the stimulus of light, the eye. We
have sense-organs for appreciating the contact quality of bodies
including vibration, the organs of touch and of hearing. We
have organs for testing the chemical qualities of substances, the
organs of taste and smell. We have organs for detecting
changes of temperature. These lie scattered in the skin over
the whole surface of the body. We have organs for appreciat-
ing pressure, both its direction and its amount, and especially

we can appreciate gravity when we move up or down. By
208

THE SLUG 219

means of all these senses then, and of certain others, we not
only become aware of the world about us and of what changes
are taking place in it, but our behavior in this world is
determined.

What is true of ourselves in respect to the determination of
our behavior by environment is true of all other animals, for
man is, indeed, in respect to his senses, merely one of the
animals. When we turn over a stone (Fig. 94), and see a
number of insects under it, hastening away until finally all
have become hidden again, we may be sure that this rapid
movement is in response to the stimulus of light, which sud-
denly falls upon them, and to the withdrawal of the comfortable
contact with the stone above. The movement to which the
animals have been stimulated will be found to be, for the most
part, away from the light. This tends to bring them into a
darker region, and if in the neighborhood they find a crevice
or hole, they will come to rest there. So, too, if we look at a
stream full of trout, we shall find that they all stand with their
heads directed up-stream. They are responding to the moving
current which would tend to carry them away.

When we see a ladybird beetle in the autumn climbing up
the side of a house, or a potato beetle climbing up a potato
plant, we may be sure that they are reacting to the guiding
stimulus of gravity ; and when we see flies coming toward a bit
of carrion, flying against the wind, we may be sure that they
are directed in their movements by the chemical particles
conveyed by the wind from the carrion to their sense-organs.

No group of animals better illustrates the principles of
animal behavior than the slowly moving snails and slugs.
They are not only sensitive to a great variety of stimuli, but

the great deliberateness of their movements enables us to
P

210 ZOOLOGY

study their reactions to different. stimuli, taken one at a time.
In this chapter we shall consider the different sorts of animals
related to the slugs and snails, with special reference to their
behavior.

The slug belongs to the group of Mollus’ca! defined as
animals which possess two distinctive organs — the foot, by
means of which locomotion is effected, and the mantle, a fold
of skin covering over or enclosing a greater or less part of the
body. The mantle usually secretes on its outer surface a cal-
careous shell. Exceptionally, both shell and mantle may be
entirely absent in the adult. Among the Mollusca the slug
is placed in the class Gasteropoda. The front part of the body,
called the head, bears the sense-organs which are in nervous
connection with a brain situated just over the mouth. The
foot is an unpaired organ situated upon the ventral side of the
body and is used to crawl upon. It is rather remarkable that,
despite the slowness of its locomotion and the ease with which
the movements associated with locomotion can be studied, the
exact mechanism of locomotion in the slug is unknown. The
slug exudes a constant stream of mucus from the mouth of a
sack situated Just over the sole of the foot, and this stream of
mucus seems to be the apparatus of propulsion. The stream
of new mucus impinges upon that already thrown out and the
reaction drives the animal forward. Gasteropods? usually
have an external shell, but some species are without it, as
is the case with the slug. When the shell is present, it is made
of one piece; that is, it is wndvalve.

Slugs belong to the group of air-breathing, land-inhabiting
gasteropods, or Pulmonata.* They may be found in the spring,

1 mollis, soft. 2 gaster, belly, stomach; pous, foot.
* Provided with lungs; from pulmo, lung.

THE

SLUG 211

summer, and autumn under wet decaying pieces of wood,

under stones or fruit, in the
in a word, in moist, dark
sand, ashes, and sawdust,
dry up the mucus which they
secrete over their body to retain
its internal fluids. Slugs are
nocturnal (Fig. 162), hence they
have the reputation of being
rather rare. During the winter
they live in the ground, encased
in their own slime, but some
species frequent greenhouses in
cold weather and in consequence
of this habit may remain active
all the year round.

The food of slugs consists
chiefly of the green leaves of suc-
culent plants, and also of ripe
fruit, such as apples. Our larg-
est slug, Limar maximus,’ is easily
maintained in captivity by keep-
ing in a dark box and feeding on
the blanched leaves of cabbage.

because

grass, on the shady side of fences ;
situations.

They especially shun
these substances tend to

Fic. 197.— Illustrating the transi-
tion of form in the shell of certain
Opisthobranchs, from the pointed

spiral to the almost flat plate. The
genera figured are: A, Acteon;

B, Aplustrum; C, Cylichna; D,
Atys; 2, Philine; F, Dolabella;
G, Aplysia; H, Pleurobranchus.
Drawn to various scales. From
Cooke, ‘‘ Mollusca.”

In captivity one individual will sometimes devour another.

Economically, slugs are of importance because at times in some

localities they cause much destruction in gardens and greenhouses.

Particularly in Europe, a species of Limax has often devastated

fields of young shoots and devoured many bulbous plants.

In the apparent absence of a shell the slug seems to be an

1 Largest.

919 ZOOLOGY

the snails —

aberrant gasteropod. Other land gasteropods
have an evident shell. In Limax the shell is reduced to a thin,
horny plate, embedded in the mantle. Between the condition
seen in the snail and that
in Limax there are inter-
mediate conditions, some
in which the large shell is
partly covered by the man-
tle, and others in which the
shell has become reduced in
size. In allies of Limax—
in a genus called Arion —
the shell is reduced to a few
calcareous grains. An ex-
actly similar series in the

degeneration of the shell is

Fie. 198.— Illustrating the gradual cov-
ering of the shell (sh) in certain Opistho- ¢ . : :
branchs by the epipodia (ep) and snails, illustrated in Figure

found in certain marine
male cepalg thes rave {© 197. ‘The beginnings ofthis
phander; C, Aplustrum; D, Aplysia; process of covering the shell
E, Philine. From Cooke, ‘‘ Mollusea.”’
are seen in many gastero-
pods in which the mantle edges may protrude beyond the lips
of the aperture, and are folded back over the outer surface of
the shell. A mere developed condition is seen in species like
Aplysia, in which the mantle is permanently turned over the
back.!| In Limax the turned-up edges of the mantle have
permanently grown together. The turning back of the mantle
seems to afford additional protection to the visceral mass.
But after the complete overgrowth of the mantle the shell is
useless, and consequently degenerates.
1 Fig. 198 D.

THE SLUG 218

The lung-snails (Pulmonates) are either terrestrial, like the
slug, or aquatic. Of the terrestrial pulmonates other than the
slug the most important are
the snails of the genus Helix!
Helix ? is noteworthy, because it
is richer in species than any
other molluscan genus, contain-
ing over three thousand of them.
The distribution of the genus is
world-wide. In North America

: : Fic. 199.—Shell of Helix albola-
the snails are most abundant in “4,;. 3 common forest snail, Nat.
limestone regions, hence they are size. Photo. by W. H.C. P.

less common in New England than in many other parts of the
United States.

id

Fic. 200.— A salt marsh by the edge of the sea, where Mclampus lives.

The reason why Helix contains so many species is because
it is undergoing a rapid evolution to-day. That this is so is

lhelix, a turning round, as in the spire of a snail-shell. 2 Fig. 199.

214 ZOOLOGY

shown by the enormous variability of individual species.
Thus in our own country a species, Helix nemoralis, introduced
from Europe, has produced at Lexington, Virginia, 385 varieties
in an area not over one-half mile in extent. These variations
consist of different combinations of ground
color and of stripes on the shell. But the
animal itself is equally variable, for any

species of Helix, collected in large numbers,
will show individuals having abnormalities
Fic. 201.—Melam- both in regard to the number of tentacles

pus, the salt-marsh and of eyes upon each tentacle. Besides
snail. Nat. size.

Photo. by W. H. Helix, a very abundant cosmopolitan land
ae: pulmonate is Pupa.! The shell is many
times whorled, and has a blunt apex. Being of small size, it
is, however, less commonly known. It is found in woods
under leaves or in old stumps and decaying logs, where it
feeds. It is a lover of darkness, moisture, and contact.

_ Intermediate between the terrestrial and aquatic pulmonates
is the family Auriculide, the members of which live on the
seashore, in salt marshes (Fig.
200), or on rocks where they may
even be immersed in_ brackish
water at high tides. One of the
commonest forms is Melampus
(Fig. 201), found among the roots

of marsh-grass. Fic. 202.—Left Physa, hetero-

Of the aquatic pulmonates thre sirophe, the left-handed. pend

a P ; e snail. Right, Limnza, the right-

genera are common and easily handed pond snail, with the

sats Hee : 9 apex eroded off as is usually the

distinguishable. Limneza, the case in adult shells. Nat. size.
“pond snail,” is common in Photo. by W. H.C. P.

1A little girl or doll. 2 From limne, a marsh.

THE SLUG 215

ditches and muddy or stagnant ponds. Its shell runs up
into a sharp spire, and is right-handed, 7.e. holding the
shell so that its aperture is next the observer and below, the
aperture is at the right (Fig. 202). Limnza crawls over the
bottom, up the stalks of aquatic plants, and on the surface
film of water. It comes to the surface, indeed, with great reg-
ularity, thrusts its lung-opening out into the air and breathes,
and then it rapidly retreats into the water. It is a remark-
able fact that an air-breathing organism, whose ancestors were
aquatic and gill-breathing, should, after having once become
emancipated from the water and having acquired lungs, have
returned again to the water. Indeed, some Limnzas have
become so adjusted to an aquatic life that they can live at
the bottom of deep lakes and never come to the surface to
breathe. In the case of such snails the lung is permanently
filled with water; the oxygen dissolved in the water being
used in respiration. The Limnzas that live in shallow
ponds are deprived of water in times of drought. They
then burrow deep in the mud and close the aperture of their
shell. By this means the loss of the water of the body is pre-
vented and the existence of the animal is prolonged until the
return of the rainy season.

Physa ! has a smaller, relatively stouter shell than Limnza,
and one whose coil is left-handed (Fig. 202). It lives in even
the smaller ponds and brooks, and may be easily reared in
aquaria. It feeds freely upon any kind of vegetable matter.
Physa_ heterostropha is the common species of the United
States (Fig. 202, left).

Planorbis? is coiled in one plane like a watchspring.’ It

1 physa, bellows. 2 planus, flat; orbis, circle.
3 Fig. 203.

216 ZOOLOGY

lives in a similar habitat with Physa. A great many species
are known, and they vary much in size. Snails of this genus
likewise are easily kept in the aquarium, and
lay numerous eggs encased in gelatinous

envelopes adhering to the glass.
Of the shells of marine gasteropods,
which are favorite objects in collections

Fig. 203.—Planor- because of their beauty and permanence,
bis, the flat-coiled
pond snail. Nat. : k
size Photo. by Lit'torina! is an example of the entire-
W.H.C.P.

only a few types can be mentioned.

mouthed marine snails. The commonest
form at most parts of the shore-line north of New York at
the present time is Littorina littorea.2 This is known in
England as the periwinkle, and is there used as food. As
its systematic name implies, it occurs on the seashore,
which it often crowds so as to force all other species from it.
It occurs north to Greenland, and on the
northwestern European coast. It has not
always occupied our shores, but has been
migrating southward.

In 1855 Littorina was found in the Gulf

of Saint Lawrence ; in 1869 it was stated to
occur in Halifax; in 1870 a few individuals Frc. 204. — Littorina lit-

; ‘ ee torea, the shore snail.
were found on the Maine coast; during 1871 — Nat. size. Photo. by

the species occurred on the New Hampshire ess

coast; in 1872 one specimen was found at Salem, Massachusetts ;
in 1875 the first two specimens were taken at Woods Hole,
Massachusetts, south of Cape Cod; in 1880 the first specimen
was taken at New Haven; in 1891 it occurred as far south
as Delaware Bay. In 1899 it was not very abundant at

1 Fig. 204. 2 From littus, the seashore.

THE SLUG 217

Cold Spring Harbor, near the western end of Long Island Sound,
but has since become so. Persons who live on the coast south of
New York City would do well to note carefully the abundance of
the species on their part of the shore-line. Besides littorea there
are two species of Littorina which were on our coast when records
first began to be made. The species may be distinguished by the
circumstances that L. littorea has a black head and a heavy shell
of brown or olive color. JL. rudis! is

HS

smaller, its shell has an angle at the apex
of 60° to 70°, and varies in color from white
to red. JL. palliata? has a shell with an
apical angle of 95°, and varying from white
to orange, slate, or brown.

Nat'ica is another common species ee
with an entire aperture to the shell. ee ane
It can be at once distinguished from nat. size. Photo. by
Littorina by the “ umbilicus,” or de- ee
pression situated at the left of the mouth and in the axis of
the shell (Fig. 205). In the living animal the shell is often
quite enveloped by the large fleshy foot. The members of
this genus lay their eggs in spiral ‘ collars”? made of ag-
glutinated sand. These are common objects of the seashore.

Ful'gur ? is a good example of a prosobranch having a canal
at the mouth of the shell. The canal exists for the purpose of
containing the siphon by which water is brought to the animal
as it lies buried in the sand. Fulgur is our largest common
gasteropod.

Its shell is about 150 millimetres long, and pear-shaped. In
one species the margins of whorls are grooved (Fig. 206); in the

1 Rough, rude. 2A cloak. 3 Lightning.

218

ZOOLOGY

other they are carried out into thorns. The egg-cases are tough

and membranaceous and resemble rows of coin strung on a string,

the whole being slightly coiled.

In U'rosalpinx ! the canal is short (Fig.
207). This typical representative of the
murexes is everywhere abundant on our
Eastern coast. It is much hated by
oystermen, by whom it is known as the
“oyster drill.” It bores through the shell
of this and other bivalves by means of its
radula and sucks out the contents through

the hole.

Fra. 206. — Shell of Ful-

The muddy bottoms of protected

gur (Syeotypus) canic- Marine harbors are occupied by the mud-
ulatus, one of the gnail (Nassa), whose canal is a mere notch

Fasiolaride. One-

fourth nat. size. Photo. through which the very long siphon can

by W. H.C. P.

be extended. The long siphon enables

it to draw in pure water while its body is embedded in the

mud. This burrowing serves either as a
protection from predaceous species or pre-
vents desiccation when the flats are left
uncovered by the retreating of the tide.
One may often see Nassas grouped in solid
masses around the body of some dead mol-
lusk. They are attracted toward the food
by a marked chemical sense, and they move
toward the source of any current that con-
veys particles that stimulate this sense.
Crepid'ula,? the boat shell or “ decker,”

loura, tail; salpinx, a trumpet.
2A small sandal (crepida).

———— |
Fie. 207. — Urosal-
pinx, the oyster
drill. Nat. size.
Photo. by W. H.
Cc. P.

THE SLUG 219

belongs to a type in which the spire has become almost obsolete.
It is still represented, however, in a rudimentary way at the
left of the aperture (Fig. 208).
The modified shape is asso-
ciated with the habit the mol-
lusk has of lying, aperture
downward, close to the rock or
another shell. By this means
the animal is better protected.

The “deck” is a plate which “"Tyo-thinds nat. sue. Photo. by
has been developed internally W. H.C. P.

to help hold the animal in the shell.

The limpets are modified sea-snails. They are bilaterally
symmetrical and are cov-
ered by a flat, conical shell
which is applied closely to
the rock all around the
base in such a way as to

protect the animal within.
In some species (genus
Fissurella!) there is an
opening at the apex of the
shell through which the
water is expelled that has
passed over the gills.

Our common Eastern rock

Fig. 209.— Patella vulgata, seen from the limpet is not perforated ; it
ventral side. f, foot; g.l, circlet of gill .
lamellz ; m.e, edge of the mantle; mu, at- known as Acmea? In
tachment muscle; si, slits in the attach- i :
ment muscle; sh, shell; v, efferent branchial 1 A little slit or fissure.
vessel; »’, aorta; ve, smaller vessels. From 2akmaios, in full bloom,
the ‘‘ Cambridge Natural History.” maturity.

220 ZOOLOGY

Europe, limpcts (Patella, Fig. 209) are used as food; but on our

Eastern coast they are too rare for this.

The hinder-gilled mollusks (Opisthobranchs) include a
large proportion of symmetrical shell-less species. The most
familiar of these are the sea-slugs. They may
be found among hydroids hanging from rocks,
or in tide-pools. Our species are usually less
than twenty millimetres long. They are often
covered with numerous gills, which give them a
velvety aspect. When placed in an aquarium,
they lay eggs in gelatinous coils on the hydroid
stems. Eolis! is a common genus (Fig. 210).

Besides the gasteropods, two groups of mol-

lusks may be briefly mentioned here. In one
Fig. 210.— Eolis. group the body is very symmetrical, not only
externally, but also internally, which is not true of most
symmetrical gasteropods. A common representative is Chiton?
(Fig. 211). This animal has a sort of coat of mail, since its
shell is made up of eight pieces, lying one
behind the other, along its back. When re-
moved from the rock or shell on which it rests,
it coils up like a pill-bug or armadillo.

Fic. 211.— Chiton
(Trachydermon)

group of squids and cuttlefishes (Ceph'alo- @piculatus, the
3 elas armadillo - snail.
poda*). They have a large, distinct head, Nat size. Photo.

by W. H.C. P.

Coérdinate with the Gasteropoda is the

a circle of arms about the mouth, a funnel-
shaped foot, and huge eyes on each side of the head (Fig. 212).
The squids are the best-known cephalopods, since they travel

1 Kolis, daughter of Eolus, the god of the winds.

2Coat, case, covering.

3 kephale, head ; pous, foot; because the arms or foot are placed around
the mouth.

THE SLUG 221

in schools in our harbors and are often cast upon the shore after
astorm. They can also be obtained in the markets of our coast-
wise cities, since their flesh is used to
a certain extent as food. Cuttlefishes,
best known from their ‘‘ bones ”’ or rudi-
mentary shells lying deep in the mantle,
are inhabitants of deeper waters. They
have shorter bodies than the squids,
and their arms are eight in number,
instead of ten as in the case of the squids.
In both groups locomotion is effected by
the reaction to a stream of water which
is taken into the mantle chamber at the
edges of the mantle and is forced out
through the “ funnel,” which lies be-
tween the eyes (Fig. 212).

The shell is rudimentary in both the
squids and the cuttlefishes, and like
that of the slug is embedded in the
mantle. There are two living genera
of Cephalopoda which have an external
shell. One is an ally of the cuttlefishes ee ae ee Peal,

—the paper nautilus or Argonauta,’ Eastern squid. One-third
nat. size. From Rathbun.

which is found in all tropical seas.
The other is the sole survivor of aonce abundant group. This
is the Pearly Nautilus of the Indian and Pacific oceans. Its
shell is divided into water-tight compartments, in the last
formed of which the animal lies. It keeps its attachment to
the shell by means of a central strand of tissue — the siphon
(Fig. 213, s). Allied to the Nautilus is the huge family of

1A sailor in the Argo.

D2) ZOOLOGY

Ammonites, of which two thousand fossil (extinct) species are
known, ranging through many geological ages.

Fia. 213.— Nautilus pompilius, the Pearly Nautilus. Median section. c, outer-
most chamber whose bottom is formed by the septum, se; s, siphon travers-
ing all compartments; e, eye; h, hood; m, part of mantle, reflected over
the shell ; /, lobes enclosing tentacles (é); si, incomplete funnel ; mu, shell
muscle ; n, gland secreting the capsules for eggs. After Owen.

CHAPTER XVI

THE FRESH-WATER CLAM: A STUDY OF RIVER
FAUNAS

THE main divisions of the animal kingdom originated along
the seashore. From the seashore animals have passed to the
bottom of the deep sea, over the surface of the seas, and into
the estuaries that open into the seas. Certain forms have
penetrated farther and farther up the estuaries and have
become, eventually, permanent inhabitants of fresh water.

The habitats offered by fresh water are of several sorts.
First there are the flowing streams (Figs. 214,215). Near the
mouths of streams the current is slow, while in the upper
courses it is rapid. Then there are the permanent bodies of
fresh water, such as ponds and lakes. Finally there are the
intermittent streams and ponds in which animals are subjected
alternately to water and drought. In the present chapter
we have to consider the animals that live in rivers and some of
the adaptations they show to a fluviatile life. In the first
place the number of different kinds of animals and the abun-
dance of individuals is less in swiftly flowing rivers than in
lakes, for the swiftly flowing river is a difficult habitat in
which to live. Free-swimming organisms tend to be swept
away unless they are powerful enough swimmers to stem the
current. The minute organisms that swarm at home on the
surface of lakes are found in rivers merely as victims of floods,

and are being swept away to their destruction. The animals
223

224 ZOOLOGY

Fic. 214.— A pool where a waterfall flows into a relatively quiet sheet of water.
The home of hydra, fresh-water clams, planarians, and leeches.

ge oe

Fig. 215.—A rapidly flowing stream with a fauna like that shown in Fig. 216.

THE FRESH-WATER CLAM 225

that permanently reside in and are best fitted for the river
habitat have either clinging organs or a high specific gravity
and live on the bottom, or else they burrow into the bottom
mud. Consequently, we find in rivers many attached animals
(Fig. 216). Thus there are sponges, the little hydra which is
referred to in Chapter XIX, Bryozoa, and, in certain parts of
the world, even barnacles. Among the animals that can cling
by means of an adhesive surface are a great variety of snails,
whose powerful foot enables its possessor to adhere to the rocky
bed of rivers. Here too one finds flatworms and leeches and
the larve of certain insects which live in nets cemented to the
stones. Among animals that are provided with other means
of prehension are crayfish, which live under stones and in pools.
In the mud or sand at the bottom are found numerous worms
and, especially in limestone countries, fresh-water clams.

All these different kinds of fluviatile animals have been
derived directly or indirectly from the ocean and have found
themselves well adapted to live in a rushing current. It will
be worth while to see how they have reached their present
home.

The fresh-water sponges belong to one small group, whereas
their marine allies are vastly more varied. The origin of fresh-
water sponges is, however, obscure. Of the Hydra-like animals
there are a few that are found chiefly in estuaries ; and in such
locations they show us that representatives of the group are
still emigrating from the sea. So, too, in the case of the Bryozoa
there are several species allied to marine families of that class
that are found in the lower courses of streams and are evidently
just beginning to become emancipated from the sea. The
river mollusks belong to several different groups which have
migrated independently into the streams. Thus in the South-

Q

226 ZOOLOGY

Fic. 216.— The fauna of a rapidly flowing stream. In the centre, nets
of the caddis-fly ; below, some hydras; still farther down, a sponge with a
leech and a clam (Psidium) left, and a bryozoan (Pectinatella) to the right.
J. H. Emerton.

bo

THE FRESH-WATER CLAM 27
ern states we have certain large water snails which are allied
to species found on the coast of the Gulf of Mexico. The
Unios find their nearest marine allies among the mussels of the
sea. In fact in the group of mussels the attempt to acquire
a fluviatile life has been made several times independently.
In Europe a mussel, very similar to that of the seacoast, has
entered the rivers of Russia and, by the aid of connecting
canals, those of Germany (Dreisenia). Among the fishes there
are those that pass from the sea to rivers regularly once a
year during the spawning season. Others live in estuaries,
but travel up and down to a limited extent. In view of the
migration of fishes to-day it is not difficult to see how some of
them, although of marine ancestry, came to live permanently
in the rivers.

Of all the varied animals of fresh water perhaps the most
conspicuous, in our Central states, are the clams. These we may
now consider in detail. The fresh-water clams belong to the
group of lamellibranch mollusks, characterized by the absence
of a distinct head, by the possession of leaf-like gills on the
sides of the body, and by the presence of a limy shell composed
of a right and a left valve. Economically this group is the
most important to man of all Mollusca. It includes both
marine and fresh-water species. About six thousand species
of living lamellibranchs and over ten thousand fossil species
are recognized. They all fall into two principal subdivisions.
The first (Siphonata) includes species which possess a siphon
and have the mantle edges grown together, while the second
(Asiphonata) has no siphon and has the mantle lobes for
the most part wholly separated. Consequently the first group
can live in the mud, drawing pure water from the surface,
whereas the second cannot do so.

228 ZOOLOGY

The fresh-water mussels (Anodonta and Unio) are extremely
common in the ponds, lakes, and rivers of North America.
Anodonta is more apt to be found in still waters and Unio in
running waters. They lie partly buried in the mud of the
bottom, with the valves of the shell gaping open and the
partly united edges of the mantle protruding. They do not
lead wholly sedentary lives, but may burrow or plow along
the bottom.

Fic. 217.— A, advanced embryo Anodonta; B, free Glochidium; /, pro-
visional byssus; s, shell; sh, hooks; sm, adductor muscle ; so, sense organs ;
w, cilia. From Korschelt and Heider’s ‘‘ Embryology.”

Their food is gained from organic particles borne along
in the current of the water. A part of this current is carried
through the mantle chamber and forced out again, deprived
of usable food and of the oxygen used in respiration. By
devouring organic matter these clams act as useful scavengers
of the water. On account of'the sessile habits of Unios they
can hardly go in search of their food, and so it is necessary
that they should live in a current of water which will bring
them food.

The family of Unionide, to which Unio and Anodontia
belong, is of world-wide distribution, but nowhere else are

THE FRESH-WATER CLAM 229

Unionidz so numerous as in the United States. They show
in our country a most marvellous variability also, so that hun-
dreds of kinds have been described from our waters. The
abundance of Unios in North America is due to the fact that
nowhere else is there such a large area of soluble limestone as
in our Mississippi Valley. The clams take from the water
the lime which they use in making their shells, change it into
an insoluble form, and thereby reduce the amount of the
inorganic matter in solution, and so render it more fit to
drink and to sustain other animal and plant life.

Although numerous and of large size, Unios do not seem to
be much used as human food. The aborigines, however,
made use of them, as the great shell-heaps on the banks of
rivers of the Ohio Valley testify. They yield also pearls,
which occasionally, especially in the Ohio Valley, are of pre-
cious quality. Even the small, imperfect pearls are of value,
since they are ground up to make the powder used in polishing
the more valuable pearls.

The spawning season of our Unios is short. The eggs pass,
during the latter part of October, into the gills of the parent,
where they undergo their early development, protected by
the parent shell and supplied richly with oxygen. The cleavage
of the egg is into unequal spheres because of the larger amount
of yolk in some of the cells than in the others. Eventually
a shell is formed, which divides into two valves united by a
straight hinge. A spine is formed on the free edge of each
valve, and a thread (‘byssus ”) is secreted from the body.
The young (Glochidium, Fig. 217), in the spring, become free
from the mother and attach themselves to the gills or fins of
a fish by means of the spines on the shells. Here they become
transformed. The single adductor muscle disappears, and

230

ZOOLOGY

becomes replaced by the two found in the adult; the gills

Fic. 218.— Teredo navalis,
in a piece of timber. P
pallets; SS, siphons; 7
tube; V, valves of shell.
From the ‘Cambridge
Natural History.”

arise, the shell gains its adult character,
and becomes free from the fish on which
it has lived temporarily as a parasite.

There are other species of fresh-water
lamellibranchs besides the Unionide.
They have much the shape of our com-
mon hard-shell clam of the sea, but are
much smaller in size, rarely exceeding
fifteen millimetres. Cyclas is of world-
wide distribution, but it is especially
common in North America. It occurs
in ditches, ponds, and rivers of New
England, as well as in the South and
West. Some species of the genus in-
habit brackish water.

The remaining families which we
shall consider come from the sea, and all
occur on our Eastern coast. Three
grand divisions may be recognized: (1)
the burrowers (Pholadide, Teredide,
Solenide, Myide); (2) the heavy-
shelled bottom feeders (Mactride,
Vencride, and Arcidz) ; (3) the byssus
spinners (Mytilide, Aviculide, Pec-

. tinide, Ledidx, and Ostreid).

The Teredidz! and Pholadidz? in-
clude certain wood and rock boring

’ species, which do great damage by bor-

1 tereo, to bore.
2 pholas, Greek name for a boring mussel.

THE FRESH-WATER CLAM 231

ing into wooden vessels and pilings (Fig. 218). In such loca-
tions they are commonly called ship-worms. The boring is done
by the movements of the shell, combined with the action of the
muscles and foot. The only thing which seems effectively to
stop these mollusks from boring into wood is iron rust, so that
piles driven full of nails are apt not to be attacked.

In the razor-shells (Solenide,! Fig. 219), the animal, like
the shell, is elongated and subcylindrical. By means of its

Fie. 219.— Ensis directus. Young. Nat. size. Photo. by W. H.C. P.

foot, which can be protruded between the valves, it excavates
with great rapidity a hole in the sand or mud into which it
draws itself. These mollusks are sometimes used for food,
but it is not easy to get them in quantity.

The hen-clams (Mactride *) include species that are more
elliptical and larger than the common hard-shelled clam or
” and have a proportionately lighter shell (Fig. 220).
They are not often used as food because they become very
tough when cooked.

“‘ quohog,

The soft-shelled clams (Myidz *) include the common clam
of New England, Mya arenaria, abundant along our whole
Eastern coast and much used as food. These clams occur
in great numbers in every mud-flat. Their great siphon is
extended at high tide to the surface of the ground, so as to

1 solén, a channel or tube. 2 maktra, a baking-trough.
3 mya, Greek name for a kind of mussel.

232 ZOOLOGY

take in and throw out water (Fig. 221); but at low tide it is
retracted, and the clam lies invisible in its burrow. This

Fic. 220.— Mactra solidissima, the Eastern hen clam. Nat. size. From
Gould-Binney.

clam was much prized by the Indians, as the great, ancient
shell-heaps along the coast testify. In 1892 the clam com-

Fic. 221.—The ‘‘soft-shelled’”’ clam (Mya arenaria), with its siphon ex-
truded to the right and its foot projecting to the left.

merce for New England was estimated to be worth nearly
half a million dollars (Fig. 222).
The hard-shelled clams (Veneride ') include Venus merce-

1 Venus, the goddess of love.

THE FRESH-WATER ULAM 233

Fic. 222.— On the mud-flat, digging the soft-shell clam.

naria, which is the commonest species, and is most abundant
south of Cape Cod. It owes its name
fact that the purple-colored patch seen on the margin of the

“mercenaria ”’ to the

Fic. 223.— Venus mercenaria, the hard-shelled clam. At the left the foot
protrudes from the shell ; at the right the siphons. Nat.size. From Verrill,
“Invertebrates of Vineyard Sound.”

234 ZOOLOGY

shell was used as money (‘‘ wampum ”’) by the Indians. The
shell is extremely heavy, and
usually nearly circular in outline
(Fig. 223).

The arks (Arcide ') and their
allies include several species hay-
ing a more or less elongated

hinge-joint crowded with many
Fic. 224.—Arca pexata, the bloody
clam. Nat. size. Photo. by
W. H.C. P. ern species (Arca pexata, Fig.

224) has bright red blood and is commonly known as the
“bloody clam.”
The mussels (Mytilid 2) are the familiar blue black, wedge-

small teeth. Our common East-

Fic. 225.— Bit of bed of mussels lying at base of the marsh-grass (Spartina),
exposed at low tide. At rising tide a swift current flows over this bed.

larca, an ark. 2 mytilos, an edible mussel of the Greeks.

THE FRESH-WATER CLAM 235

shaped shells attach in clusters or beds to rocks near low tide.
In the absence of rocks they may attach themselves to the
roots of the marsh-grass. They form so solid a wall here as
to protect the mud and the marsh-grass that
is growing in it from being washed away.
Thus the relations of marsh-grass and mus-
sels are reciprocally advantageous (Fig. 225).
Mussels are edible and in Europe they are j
reared for the market on woven nets, which y,4. 996. —Thesecal-
are submerged at each tide. lop (Pecten trra-
3 : dians). Right or
The pearl mussels (Aviculide!) are a lower valve. One-

group closely allied to the last, but not Dalf nat. size.
represented on shores. They are important because they
produce the best pearls. Pearl-fishing has been carried
on since the earliest preserved historic records. The pearl
banks of Ceylon are known to have been fished for two
thousand years. The finest pearls,
however, come from the Persian
Gulf. They are gathered there
by native divers, who, after tak-
ing several deep breaths, either
dive down unaided or descend
7 upon weighted ropes. When they

Fic. 227.—One of the Ledide.

Yoldia, foot protruding below. ¢anno longer remain under water,
Nat. size. Photo. by W. H.C. P.

they either ascend again unaided
or are rapidly drawn up to the boats above. The pearl oysters
brought up to the surface are then examined for pearls. The
pearl is the secretion of the oyster about a small foreign body,
such as a grain of sand or a parasitic worm. This secretion
prevents the irritant from injuring the tissues. It is of the

1A small bird (avis).

236 ZOOLOGY

same nature as the substance lining the shell. The latter
is the mother-of-pearl of commerce, and is used for knife-
handles, buttons, and the like. The iridescence is not due
to the chemical composition of the secreted substance, but
to the fact that it is deposited so as to leave fine lines on the
surface which diffract the light.

The scallop-shells (Pectinide ') occur along our whole coast.
They live in shallow water, and are capable of rapid movement
in the water by clapping the valves. The adductor muscle

Fic. 228.—The Eastern oyster (Ostrea virginiana). One-third nat. size.
Photo. by W. H.C. P.

of the valves alone is eaten by man. The common species is
Pecten irradians, which has a ribbed shell of varying color
(Fig. 226).

The lidas (Ledidz) include certain elongated shells with
a shiny epidermis, and a large number of teeth on the hinge,
which are found chiefly in mud in rather deep water. The
animal has a large foot (Fig. 227) with which it burrows rapidly.
It can also move rapidly through the water as the scallops do.

The oysters (Ostreidze?) include the most important inver-
tebrate food fishery, being valued at twenty to thirty million
dollars per year for our Atlantic seaboard. Oysters are found

1 pecten, comb. ? From Greek name for oyster.

TUE FRESH-WATER CLAM Put

on all coasts. Our Ostrea virginiana! extends from the Gulf
of St. Lawrence to the Gulf of Mexico. The oysters of our
Western coast are not so important as the Atlantic species.
In Japan, however, there is a species occasionally gaining a
length of three feet. The principal European species is
Ostrea edulis. The oyster was formerly commoner and larger
north of Cape Cod than it is now, for the great aboriginal
shell-heaps (‘‘ Kitchen-middens ”) of the New England coast
contain shells of enormous size. The cause of this gradual
extinction of the oyster is uncertain, but is believed to be due
partly to general climatic and geographic changes and partly
to overfishing.
1 Fig. 228.

CHAPTER XVII

THE ANATOMY AND PHYSIOLOGY OF ECHINO-
DERMS WITH PARTICULAR REFERENCE TO THE
SEA-URCHINS

General Form of the Body. — In the echinoderms the body
has a radial arrangement of parts; 7.e. there are more than
two similar parts arranged around the chief axis of the body,
whereas in bilaterally symmetrical animals, like ourselves,
there are only two such parts. In echinoderms the number of
such parts is nearly constant; namely, five (Fig. 229). Now
a radial arrangement of parts is a characteristic of an attached
organism —a hydroid sea-anemone, sunflower, or tree — as
a bilateral arrangement is of a locomotor organism. Conse-
quently it is tolerably certain that the ancestors of echinoderms
were attached animals. Among modern echinoderms such
attached animals are, indeed, found in the groups of Crinoids
or Sea-lilies, a group that was formerly more abundant than
it is now (Fig. 252). Also in earlier geologic times echino-
derms were represented by two or three other classes now
totally extinct, of which some were stalked. It is possible
that from such sessile organisms the free-living echinoderms
of to-day sprang.

In the body of any echinoderm we recognize a main axis
with two quite different poles, 7.e. at the two ends of the axis
the body is quite different. That pole where the mouth
usually lies is called oral; the opposite pole aboral. Typically
there are five equal parts arranged about this main axis. In

238

ANATOMY AND PIYSIOLOGY OF ECHINODERMS 239

those sea-urchins, however, that have assumed the habit of
free locomotion on the oral surface (Fig. 230), the mouth has
moved from the centre
toward one edge and the
anus, which is typically at
the centre of the aboral
pole, has moved toward the
opposite edge, so that, in
these cases, the body has
become bilaterally sym-
metrical and the alimentary
tract tends to run horizon-
tally instead of vertically.
This result shows the effect
of a locomotor habit on the
radial form.

The body-wall of echino-
derms contains limy plates
(Fig. 230). These are best
developed in the sea-ur-

chins and sea-lilies, where
‘ q PO = Ae apie .
they enease the entire ae 229. A aoe cucumber (eo nna ria),
showing the radial, tree-like, arrange-
body. Ten bands run ment of partsin an echinoderm. Parts
| iigna td are seen to be arranged ona basisof five.
along meridians fron) one Three rows of tubular feet show; two
pole to the other ; in alter- rowsare hidden. There are ten tentacles
4 at the upper end of the body of which two
nating bands the plates are (front middle) are small. From Parker
perforated for passage of 2” Haswell.
the tube-feet — such are called the radial bands or radii; the
others are called interradii. In starfishes the interradii are
small and unimportant, forming the part of the body-wall

lying between the arms. The limy plates lie embedded

240 ZOOLOGY

in the skin where they have been formed; from them
often arise other structures — spines, which gain a great

Fic. 230.— A sea-urchin that has gained a bi-
lateral shape. The mouth is shown at the
upper (anterior) end; the anus at the pos-
terior end. A, dorsal or aboral view; B,
ventral or oral view. From Parker and
Haswell.

size in certain sea-ur-
chins and are moved by
muscles at their base.
Certain spines are mod-
ified and have special
uses; such are the little
forceps that abound
about the mouth and
are believed to help
keep the other spines
clean. In the sea-cu-
cumbers (Holothurians),
alone, is the skeleton
insignificant, being
made up of small spic-
ules that take on a va-
riety of forms, such as
rods, anchors, wheels,
etc. (Fig. 231). Since
these bodies are rela-
tively small, the skin of
holothurians is flexible
and often transparent.

The Water-vascular
System. — The most

characteristic feature of echinoderms is a system of water-tubes
which serve for locomotion. This system opens to the exterior
by means of a sieve-like body placed at the aboral pole called
the madreporite. Thence a canal runs to a circular canal sur-

ANATOMY AND PIIYSIOLOGY OF ECHINODERMS 241
rounding the cesophagus, and from this canal a tube runs out and
along each of the radii. From this radial canal in turn a series
of tube-feet are given off on the right and left; these are the
locomotor organs (Fig. 232).
Thus the locomotor organs are
tubes closed at the outer end
and full of water. Atits inner
end each tube-foot is swollen
into a large bladder. The way
a tube-foot acts is as follows:
The circular muscles in the wall
of the bladder and of the foot
itself contract, thus forcing
water out into the tube-foot,
which in consequence elongates
enormously and may reach out
beyond the tip of the spines.
Upon touching a solid object

the sucker on the end of the
tube catches hold. Then the
muscles that run lengthwise of
the foot contract and shorten
the foot, its fluid flowing in-

Fic. 231.— Spicule from the skin of
sea-cucumbers. 1, anchor and an-
chor plate; 2, ‘‘stool”’ of Cucu-
maria; (Fig. 229) 3,‘ cross’’ from
a Cucumaria; 4, rod from tube-feet;
5, supporting plate from tube-feet ;
6, another form of ‘‘stool”’ ; 7, rod

from tube-feet; 8, latticed hemi-
sphere; 9, ‘‘wheel.’’ All much
magnified. From Lang.

to the bladder. If the solid
object is immovable, then the
starfish or sea-urchin moves toward it; but if the object is
easily moved, it may be brought toward the echinoderm.
Organs of Nutrition. — A complete foot-canal, beginning
with a mouth and ending at an anus, is found in echinoderms
in general, excepting the serpent-star and a few other starfish.

The mouth is guarded by hard parts which in sea-urchins
R

a ZOOLOGY

become five large, bony jaws—constituting together the

“lantern of Aristotle” (Fig. 233).

These jaws are worked

by powerful muscles, and each carries a chisel-shaped tooth

RS

be

(x

ELL
Xe

«

ai
z
x

.

—

(

i?
oe

Ys

Fig. 232.-— The water-vascular system of
a starfish. m, madreporite, connecting
by acanal, (m’), with the circular canal
(c), from which the radial vessels (r),
run to each arm and on which lie the
vesicles (ap) that serve as reservoirs.
From the radial vessels (r) tubes (r’),
are given off to the tube-feet and their
bladders (a). From Parker and Has-
well.

that is capable of continuous
growth. It would be difficult
to find in nature adaptations
complete than the
transformation of twenty-
five incipient plates into five
powerful and effective jaws.

The food, torn up by the
jaws, passes into the diges-
tive tube which, instead of
extending straight to the
aboral pole, forms a large
loop in the body. No dis-
tinction between stomach
and intestine is to be made

more

out, and there are usually no
large glands; but in most
echinoids there is a long tube
lying alongside the intestine
(stph, Fig. 234),
from it near the mouth and

opening

emptying into it again at the
middle third of its course.

It is possible that this tube serves to supply oxygen to the

blood vessels that go to the intestine primarily for liquid

food.

Organs of Respiration.— These are very varied in the
different classes of the echinoderms, and probably in each

ANATOMY

individual several different organs aid in breathing.

AND PHYSIOLOGY

OF ECHINODERMS 243

In

sea-urchins, as in starfishes, there are hollow outgrowths of the
skin which are so thin that oxygen can be absorbed by them

from the surround-
ing water. In star-
fishes out-
growths are very
numerous and
small; in echinoids
there are a few
large ones near the

such

mouth.
tion probably also
takes place through
the walls of the am-
bulacral feet and in
the extra intestine,
as just described.
The class of holo-
thurians have an
extensive,
branched sac which
lies in the cavity of
the body and is
filled with water
that is periodically

Respira-

much-

renewed. This sac is called a “ water-lung ’

tree.”

Ce ues
wipe OFT VES
amir

CoS

WHEeSUP

Fic. 233.— A section through a typical sea-urchin,

showing the mouth (mo.) and the jaws with the
muscles (mus.) that move them. The food canal
(alt.) has been cut at the beginning of the intestine
(int.) and the great loop (cf. Fig. 234) of the latter
removed for simplicity. The rectum (rect.) and
anus (an.) lie at the upper pole. Other parts that
are referred to are: ab. r. ves, circular vessel around
anus; amp, bladders at base of tube-feet (t.f.) ;
aur, calcareous loops for attachment of muscles;
cel, the body cavity; int. ves, intestinal blood
vessel; mad., madreporite and its canal (mad.
can.) ; nerd. r, nerve-ring about mouth; oc, eye-
bearing plate; or.7r.v, circular vessel around
mouth; plex, gland on madreporic canal ; pol. ves,
reservoir to water system; rad. amb, radial am-
bulacral vessel; rad. ne, radial nerve ; siph, a tube
on the intestine (cf. Fig. 234). From Parker and
Haswell.

’

or “ respiratory

Organs of circulation are ill defined. Great spaces or
cavities occur in the body which frequently surround the

other organs.

These spaces contain sea-water plus a certain

244 ZOOLOGY

amount of nutritive matter. Traces of thin-walled vessels
occur; one set accompanies the water-vascular system and
a complicated set of capillaries lies in the intestines. No
“ pulsating ” heart is known; hence the fluid must pass only
very slowly through
these spaces.
Organs of ex-
cretion are not
present, probably
because the dis-
solved products of
decomposition
readily pass out
through the tube-
feet and the skin,
which are bathed

Fic. 234. — View of internal organs of a sea-urchin
after removal of the oral half of the body wall.
The food canal (alz.) is shown entire, beginning at by constantly re-
the lantern (dant.) and passing along the esophagus
(@s.) and intestine (ali. ali.) to the rectum (rect.). newed sea-water.
Parts of five ovaries (ov.) are seen arranged around R epro ductive
the anus. The blood vessels are represented by a
circular vessel around the mouth (or. r. ves.), one O rgans.—_ The
around the anus (ab. r. ves.), and avessel on the in- J... : F
testine (int. ves.). The siphon is shown at siph. SESS AAT usually
From Parker and Haswell. separate in echino-

derms. The eggs or sperm-cells are usually formed in the
walls of pouches opening interradially; in typical sea-
urchins, at apertures in five plates lying around the anus.
Eggs are poured out and stream down among the spines
and often develop there under their protection.

Musculature. — Owing to the rigid outer skeleton, a gen-
eral body musculature is nearly wanting except in holothu-
rians. Muscles move the jaws and the spines of sea-urchins,
and these are frequently very powerful.

ANATOMY AND PHYSIOLOGY OF ECHINODERMS 245

The nervous system is mainly on the surface of the skin.
There is a ring of nervous tissue (Fig. 233, nerv. r) surround-
ing the mouth and sending a branch along each radius (rad. ne.).
Each branch controls the movement of the tube-feet of its
radius. In sea-urchins a special set of
nerves go to the musculature of the Jaws.

Sense-organs. — The tube-feet are
certainly delicately sensitive to touch in
all echinoderms, and in starfishes the ter-
minal tentacles seem to be specialized
organs of sense. Red “ eye-spots”’ are
found at the ends of the arms of star-
fishes. These spots are covered with

Fic. 235.—One of the
little pits or depressions that are full of little spheres of sea-ur-
chins, diagrammatic and
much magnified; cut
can hardly forma picture on a retina. lengthwise. (1), the cal-

ei careous mass covered with
Over the oral surface of the radii of sea- skin (2), borne ona limy

pigment and no doubt absorb light, but

urchins are scattered modified spines stem (3), which in turn
aes _ is worked by muscles at
consisting of small spheres resting on a (4), over a knob (6) of
‘ . the limy plates (7). The
tubercle (Pig, 225), “These siormally tes ace ander the
hang straight down; and if asea-urchin control of a nerve-centre
. at (5). From Lang.
be turned wrong side up, they press on
the skin and perhaps thus make the animal aware of its abnor-
mal position. They are thus thought to be organs of “ orienta-

tion,” — informing the animal of its position in the world.

CHAPTER XVIII
THE STARFISH: A STUDY OF EMBRYOLOGY

Srnck fatal accidents are all the time happening to individ-
uals of any species, in the course of time a species would become
entirely extinct were there not some way of continuing it.
All animals as well as plants have a single method of making
good the losses due to death, and this method is the division
of the individual, so that two or even a hundred or more
take the place of one. This process of multiplication of indi-
viduals through the division of a single individual is called
reproduction.

Although all forms of reproduction are fundamentally one,
several sorts may be distinguished, owing to certain minor
differences between them. Thus there is the method of fis-
sion, as seen in the lowest organisms, in which the body of the
reproducing individual divides into two equivalent parts.
Then there is reproduction by budding, as seen in certain
aquatic animals and nearly all plants, where an outgrowth or
bud arises on the side of the parent individual. This bud
gradually develops into the form of the adult and may then,
under certain circumstances, be cut off from the body of the
parent individual. Also there is the method of sporulation,
in which the body of a single organism breaks up at once into
a large number of equivalent parts called spores. The method
that has become commonest among both animals and plants,

however, is that of reproduction by germ-cells. By this process
246

THE STARFISI 247

only a small part of the body is divided off to form the next
generation. In this case the living thing thus separated from
the parent is not only very small but, apparently, very simple.
It undergoes a series of changes by which it becomes more
and more complex until finally the adult form is achieved.
The study which traces the changes that the egg passes through
in its development into the adult is known as embryology. As
an example of the embryological history of an organism we
may consider the development of the starfish egg.
Development. — Starfishes have the sexes distinct; and
the sex can sometimes be told by the color. In the common
Eastern species! the female has a bluish tint, while the males
are of a reddish brown color. Both the eggs and sperm are
extruded into the water through small openings on the aboral
surface at the interspace between two adjacent arms. The
ege is hardly visible to the naked eye and is enclosed in a
delicate membrane through which one of the sperms penetrates
into the egg. This is called fertilization. The entrance of
the sperm seems to start the development of the egg. First,
the egg undergoes cleavage; that is to say, the single sphere
breaks up into two, four, eight, sixteen spheres, and so on
(Fig. 236). Finally a hollow ball, made up of these spheres
or cells, is formed, called the “blastula.” Next the wall of
this hollow sphere is pushed in at one side, forming a sort of
cup with two walls. This is the so-called “ gastrula.” The
cavity of this cup is the digestive cavity. At first it is a sac
with only one opening, but later a second opening, the true
mouth, breaks through and the former opening persists as
the anus. Pairs of arms, edged with cilia, now bud out on
each side of the body. At this stage the organism is alike

1 Asterias vulgaris.

248 ZOOLOGY

b.

g h Oy
Fic. 236. — Illustrating the transformations from the egg to the young
larva of an echinoderm (the sea-urchin, Arbacia). From W. Kk. Brooks.
a, first cleavage plane formed, 2-cell stage; b, second cleavage plane
formed, 4-cell stage; c, third cleavage plane formed, S-cell stage; d,
view from one pole of the 16-cell stage ; e, same stage from the side; f, a
later stage with numerous cells; g, same stage seen in section, the ‘ blas-
tula’’; fh, the transition to the gastrula stage ; 7, side view of young larva.

THE STARFISH 249

on the two sides or bilaterally symmetrical.'. It swims freely
in the water and is known as a larva. The larva has, it will
be observed, very little relation in form to the adult starfish.
The change from the larval to the adult starfish is known as a
metamorphosis. Even in the bilateral stage the system of
water-tubes of the adult starfish has begun to form and, finally,
over the stomach on the left side five pockets, radially ar-
ranged, make their appearance; these are the five radial
water-tubes, one of which runs down each future arm. On
the right side of the stomach, calcareous plates are laid down
to form the aboral wall of the starfish.2 The young star is
now found as a parasite at the hinder end of the larva. Soon
all the front end of the larva, together with the long arms,
becomes absorbed.

The larva now ceases to swim and settles to the bottom.
There the process of resorption is completed, the upper and
lower surfaces of the star approach each other, the limy skele-
ton and sucking-feet rapidly develop. At this stage the disk
is so large and the arms so short that the young starfish looks
more like a sea-urchin than an adult starfish. The elongated
arms are acquired at a later stage.

1 Fias. 237, 238. 2 Fias. 239, 240, ab, ab’.
Fias. 237-240. — Larval stages and metamorphosis of starfish. After draw-
ings of E. B. Wilson, from Brooks, ‘Invertebrate Zoology.”
Fic. 237. — Dorsal view of starfish larva with beginnings of ciliated arms.
Fic. 238. — Ventral view of same larva.
Fic. 239. — Side view of an older larva in which young star is beginning to
arise.
Fia. 240. — Ventral view of same larva. a, anterior end; b, posterior end;

1-4, ciliated projections; a’, preoral arms; am, oral surface of young star
with beginning water-tubes, am-am*; ab, ab’, ab®, aboral surface of star;
c, postoral arm; 7, intestine; m, mouth; n, lateral arm; o, anus; @,
cesophagus; g, g', dorsal lateral arms; s, stomach; ww’, water tubes;
am, Fig. 238, region from which water-tubes arise.

Fic. 238.

Fie. 237.

260

THE STARFISH 251

Systematic Position. — The starfishes belong to the group
of Echinodermata,! as is proved by their five-rayed structure;
the well-developed system of limy plates in the skin; a system
of water-tubes, used for loco-
motion; and the separation
of the intestine from the
body-cavity.

Distribution and Habitat.
— The common pink star-
fish of the eastern United
States (Asterias? vulgaris *)
ranges from Labrador to
northern Florida.’ It lives
near the shore, extending out
SE ty cae

not abundant at greater rays. One-half nat. size. Photo. by
W.H.C. P.

depths than sixty fathoms.
It is found especially on the oyster-beds, where it is very destruc-
tive. On rocky coasts starfishes will be found in crevices of the
rock or in tide-pools. They love cool waters, and are often
found hanging on vertical walls or ledges. Upon reaching the
surface of quiet water, they may extend one or more of their
arms out upon the under side of the surface film and seem to
hang in part from it.

Abnormalities are frequently found among starfishes, —
partly on account of their capacity for regeneration, even from

1 echinos, hedgehog, sea-urchin ;' derma, skin.

2 From aster, star.

3 Common.

* A dark brown form, sometimes called Asterias Forbesti, is recognized by

some authors as a separate species inhabiting the coast from Massachusetts
Bay southward.

252 ZOOLOGY

the disk and a single arm. Thus one may find a starfish with
three or four rays, er with a small ray between normal-sized
ones. Not all abnormalities seem to be the result of mutila-
tion, however; for example, sometimes two arms seem to be
fused (Fig. 241).

Fic. 242. — Cribella sanguinolenta. Nat. size. From Leunis.

Other Starfishes. — Besides Asterias vulgaris there are over

five hundred species of starfishes. In some of these — as in

Asterias — the skeletal plates of the skin make a network;
in others they form a solid calcareous covering.!

1To the first class belong, besides Asterias vulgaris, Asterias ochracea,
which occurs commonly on the Pacific coast from Sitka, Alaska, to San Diego,
California. This hasa much thicker, more solid skin than the Atlantic species.
A. gigantea attains a diameter of over two feet. Asan example of the second
class may be cited Cribella sanguinolenta (Fig. 181), a smooth, leathery,
blood-red starfish, about ten centimetres in diameter, which, next to A.
vulgaris, is our commonest Eastern species.

THE STARFISH 253

Certain starfishes have many arms instead of only five! In
still other starfishes the rays are partially connected by a mem-
brane like the web of a
duck’s foot, so that the
whole outline is nearly
pentagonal (Fig. 244). In
extreme cases the outline
becomes strictly pentag-
onal or even approxi-
mately circular in plan,
like a sea-urchin. The
last species shows a transi-
tion between starfish and
urchin.

The Serpent-stars.— In
the serpent-stars (Ophiu- Fic. 243. — Solaster, a multi-rayed starfish.
oridea 2) the organs are Reduced. From Leunis.
not prolonged from the disk
into the arms, consequently
the arms may be thrown off
without injury to the ani-
mal; hence the name
“brittle-star.”” The brittle-
stars fall into two groups, in
one of which, the serpent-
stars, the arms are un-
branched,? while in the

1Tt is so in the case of Solaster
endeca of the northern Atlantic
(Fig. 243).

2ophis, serpent ; oura, tail.
3 Fig. 245,

Slightly reduced. Photo. by W. H.C. P.

254 ZOOLOGY

other, the ‘ basket-fish,” the arms are branched.' The ser-
pent-stars * live in crevices of the rock and, being of rather
small size, are not commonly seen. At the base of the arms, on
the right and left, are a pair of slits, which form the exits from
pouches into which the reproductive glands open (Fig. 246).
In certain species the pouches are used for brooding the
young.

The hasket-fish occur in Northeastern waters, from low tide
to one hundred fathoms, and are often brought up by fisher-

Fic. 245. — Amphiura squamata. One of the Ophiuride. Nat. size.
Photo. by W. H.C. P.

men, to whose lines they are led by their instincts to cling.
The branching of the arms enables the animal to hold its prey,
which consists of shrimp and fish.

The sea-urchins, or echinoids, may be regarded as starfishes
in which the arms have shortened and the disk enlarged so
as to fill up the interspaces, and make a solid, nearly spherical
form. The sea-urchins eat various small animals and get food

1 Fig. 246.
* Of the serpent-stars there are two common forms on the New England
coast, — a white species, with long, slender arms, Amphiura squamata (Fig.

245), and the spotted Ophiopholis, which has shorter, stouter arms.

THE STARFISH 255

also from small bits of organic matter in the mud which they
swallow. They live more concealed than the starfish, for
some burrow in the mud and others — such as our green sea-

Fic. 246. — Part of basket fish (only a portion of one arm showing) viewed
from oral pole. In each inter-radius a pair of slits leading to the brood
pouches. From Lang.

256 ZOOLOGY

urchin of the Maine coast (Fig. 247)— grind out pockets in
the rocks by means of their spines. Others cover themselves
with seaweed, and thus become inconspicuous. — Besides the
green sea-urchin, which is found north of Cape Cod, we have
a black sea-urchin (Arbacia), which extends south as far as

Fig. 247. — Strongylocentrotus, the Eastern green sea-urchin, with tube
feet extended. From ‘Standard Natural History.”

North Carolina. We have on the east coast also two kinds of
flat sea-urchins (sand-dollars), which live in the sand from low
water to one hundred fathoms. Their spines are small and
silky (Fig. 248),

The sea-cucumbers, or Holothurians,! may be likened to soft-
skinned sea-urchins, with the body drawn out to the form of
a cucumber, or even of a worm. The limy skeleton is reduced

'holothurion, a sort of water polyp.

THE STARFISH 25

to small plates lying in the skin. The mouth is surrounded by
a circle of tentacles (Fig. 249). The ambulacral feet are some-
times absent. The Holothurians live in sand and mud, often
deeply buried, and feed on small marine animals or the decay-

Fig. 248. — View from mouth side of a sand-dollar (Mellita). From Lang.

ing particles mingled with the mud which they devour. They
are of considerable economic importance. The members of
one genus (Holothuria) are taken in great numbers on the
coral reefs of the Pacific Ocean and the China Sea, where they
are commonly known as “ trepangs.” They are cut open,
washed, boiled, dried, and sometimes smoked. They are sold
in Chinese ports and some species are considered by Chinese
epicureans as great delicacies, being cut up into small lumps

which are boiled to make a soup.
Ss

258 ZOOLOGY

Several species of Holothurians occur on the Maine coast. A
barrel-shaped form with a sort of tail (Caudina,! Fig. 250) occurs on
the Massachusetts coast. <A
worm-like form, but with a
beautifully transparent skin
(Synapta,? Fig. 251), is found

in sandy beaches from Massa-
“2% chusetts to New Jersey.

The sea-lilies, or Cri-
noids,* are familiar as fossils
to residents of New York
State and the Ohio and
Mississippi valleys. The
living animals are less often
seen, for they are inhabit-
ants of the deep sea. They
have a cup-like body, with
the mouth at its centre
directed upward, and sur-
rounded by tentacles (Fig.
‘ 252). The cup is either
Fie. 249. — One of the sea-cucumbers borne on the end of a long

(Cucumaria) showing mouth (2), sur- Bi REE: See
rounding tentacles (1), and anus (3). stalk or is unstalked. The
About nat. size. From Lang. former condition is more

usual among the fossil species; the latter becomes more and
more common as the geological ages follow one another.
leauda, tail.

2 sunaplos, fastened together ; from sun, with, and apto, to fasten.
3krinon, lily ; eidos, form.

TT

STARFI

THE

SOOM
ee

im

LM, So

Nea

ey

avg
3

ee:
ad

PaaS a:
—™ en
3g 28.
aas
a> Ss
Oo ©
=

|g
i -~o
ea eels
Nous
a eS
aos
2 Bw

Fre,

Fia. 251. — Synapta inherens.

b, longitudinal

muscles ;c,alimentary tract.

a, tentacles ;
After Quatrefages.

.—Asea lily, Melacrinus inter-

After P. H. Carpenter.

ruptus.

CHAPTER XIX
HYDRA: A STUDY OF ATTACHED ANIMALS

A common distinction between plants and animals is that
plants are attached and rooted to the soil, whereas animals are
able to move from place to place. Although this distinction
holds in the case of most animals and plants it is not without
numerous exceptions. Thus there are many lowly organisms
which are assigned to the plant kingdom that have never lost
the power of swimming about. This is true of the small, green
organisms that live on the surface of the sea or in the waters of
ponds. It is also true of the whole group of bacteria that play
so important a part in disease. On the other hand, there are
a few animals that have lost the capacity for locomotion in
their adult stage and are rooted to the substratum like plants.
There are four different types of attached or sessile animals:
(1) the Sponges and (2) the group of Ccelenterata, both of
which we shall consider in the present chapter; (3) the Moss-
animals or Bryozoa considered in Chapter NIT; and (4) the
Mantle-animals or Tunicates considered in Chapter NXT. In
their young stages all of these animals are free-swimming,
but throughout their adult life are attached to the solid objects
of the bottom. We are bound to conclude that all attached
animals have been derived from free-swimming ancestors,
and we have therefore two questions to answer: Why should
any free-swimming form evoive into an attached one, and What
changes have attached animals undergone in abandoning
their free life?

260

HYDRA 261

In regard to the first question we can only say that in the
attached condition animals are no less able to live and multi-
ply than in the free-living state. The sponges and the corals
that help to build oceanic islands, and the Bryozoa that are
found on every sea-coast and in nearly every lake and pond
are eminently successful groups.

In regard to the changes in form which aecompany sessile
life more may be said. First, the attached or sessile animals
tend to grow, like the trees, by buds. The new individuals,
budded from the old, may in some cases separate from the
parent individual and swim away to become attached again at
a distance, or they may remain as permanent branches. By
repetition of the budding process a tree-like form may be pro-
duced, as in the corals. Secondly, attached animals, since
they do not move from place to place, have less need of sense-
organs with which to find the way. Consequently, we often
find attached animals devoid of organs of hearing and even
of sight, although the touch reaction is always present. As
a result of the reduction of sense-organs on the head, the brain
has become greatly reduced. Of course all locomotor organs
have become rudimentary and the muscular system has corre-
spondingly become very rudimentary. These reductions in
turn have affected the nervous system so that it has become
greatly simplified. Thirdly, since attached animals are not
able to hunt for their prey, they must take what is wafted to
them by currents in the water. Furthermore, they are supplied
with a mechanism for making whirlpools the apex of which
leads to their mouths. This mechanism often consists of
tentacles covered with cilia, the beating of which creates the
vortex whereby small particles of food are drawn into the
mouth. Finally, the methods of reproduction have been

262 ZOOLOGY

multiplied. In addition to reproduction by means of eggs and
the buds already referred to, there are special kinds of buds
formed to tide the species over some difficult period such as
winter or periodic drought.

The Hydra, which is the type of attached animal we propose
to study, belongs to the phylum of Ccelenterata,—a phylum
that includes both sponges and certain organisms with nettle
organs. The Coelenterata are, for the most part, sessile
animals. Consequently they have a more or less radial or
tree-like form, since animals attached to the earth tend to
form a cylindrical stem with branches springing out on all
sides of it. They have also a system of internal cavities
serving for the digestion of food as well as for a body-cavity.
The body-wall (which is also the wall of the food-cavity) is
made up of two layers,—an outer skin, or ectoderm, which is
protective and contains sense-organs, and an inner skin, or
entoderm, which has a digestive and absorbing function.

The sponges are sessile; have no nettling organs, and
have the body-wall perforated by many fine incurrent open-
ings and a large exhalent opening (Fig. 253). Most sponges
produce buds and give rise to colonies; they also frequently
produce little round bodies which survive when the rest of the
species is killed in the winter and hatch out the following spring.
A few sponges are simple individuals, having the form of a
cask. The delicate body-wall is supported by a network of
spicules made up, in the different groups, of different materials.
In some cases the spicules are limy, as in all the common
fresh-water species; in other cases they are silicious, as in the
glass sponges; while still others are horny, like the bath-sponges.
Generally the sponge is not a simple individual, but is a colony
made up of a number of individuals (zooids) that have budded

HYDRA 263

froma central one. This is the case, for example, in the bath-
sponges. A small bath-sponge is composed of the skeleton of
only a single individual, whereas the larger sponges may be com-

Fia. 253. — Sycon gelatinosum. A portion slightly magnified: one cylinder
(that to the right) bisected longitudinally to show the central stomach-
cavity opening on the exterior by the osculum, and the position of the in-
current and radial canals; the former indicated by the black bands, the
latter dotted. zp. marks the position of three of the groups of inhalant pores
at the outer ends of the incurrent canals; 0, osculum.

posed of half a dozen or more zooids, the number of which may

be determined by counting the number of large openings in the

sponge. The soft living matter may easily be removed from
the skeleton, and this is regularly done in preparing the sponges

used in commerce. Our common bath-sponges come from

264 ZOOLOGY

tropical waters and are torn, either by divers or, as in Florida,
by hooks of special form, from the rocks at the bottom of the
sea near the coast. About 2250 persons are engaged in the
sponge fisheries of Florida, and the annual catch is sold for
about half a million dollars. The principal centre of the in-
dustry is Key West.

The group of nettle animals is characterized first of all by
little organs which, in many species, are capable of irritating
even the skin of man; these organs consist of a little bladder
which secretes a poisonous fluid and a long tube by which it
passes out of the bladder. The nettle animals also have a true
mouth surrounded by tentacles. The Hydra belong to this
group.

There are two common species of Hydra: the one is of a green
color (Hydra' viridis *), and the other is flesh-colored (H.
fusca*). They are found in standing or slow-running water,
attached to submerged plants, sticks, and stones. Throughout
the winter they live at the bottom of ponds, below the ice.
The body of Hydra is soft and highly contractile, so that, when
first drawn from the water, it appears like a speck of jelly.
Left undisturbed, the animal expands, and its five to eight ten-
tacles wave slowly about in search of food. The tentacles are
richly supplied with nettling cells, each of which contains a
fluid-filled capsule, in which is coiled a thread-like tube.
When stimulated by contact with some foreign body, the ten-
tacle closes around it, while from each capsule the lasso-thread
rolls out as the finger of a glove is rolled inside out, and an irri-
tating poison is discharged. If a small animal has been the
irritant, it is instantly caught in the thread, paralyzed by the

1 hydra, a mythological monster, capable of regenerating its head.
2 Green. 3 Brown.

HYDRA 265

poison, and soon conveyed to the Hydra’s mouth. The
principal food of Hydra consists of small worms and the
smaller Crustacea, such as Daphnia and Cyclops.

Fie. 254. — A colony of Cordylophora lacustris, on a shell of Mytilus. For
clearness, a number of the erect branches are cut off at the stolon. a, very
young shoot without lateral branches; 6, young stock with lateral branches
but no gonophores; c, a stock with gonophores on lateral branches;
d, fully grown stock with lateral stems. After Schulze.

Fresh-water Hydroids are of extremely few kinds. Hydra
was once regarded as the only instance, but others are now
known. One of these, called Cordyloph’ora (Fig. 254), is found
chiefly in brackish water or in fresh water near the coast.
Like many of the marine hydroids, Cordylophora produces its
young in special capsules, called gonophores, which are rudi-
mentary jellyfishes (Fig. 254,c). The young become free when

266

ZOOLOGY

they have gained an elongated, cylindrical form. There are
other fresh-water species which have free jellyfishes. In this

Fic. 255.—Stylactis, a tubularian
hydroid, growing on asnail.
size. Photo. of living animal by

W. iH. C.P.

country we have a_ species,’
hitherto known only about
Philadelphia, whose hydroid
stage is extremely small and
bears no tentacles. The jelly-
fishes are set free during July.
Freshwater jellyfishes have also
been described from Lake Tan-
ganyika, Africa, and from a
tank at Regent’s Park, London,
to which they had doubtless
been imported on plants. It is
very probable that all fresh-
water hydroids which produce

Fic. 256. — Hydractinia, a tubularian hydroid. a, colony growing on gastro-
pod shell inhabited by a hermit-erab; b, bit of colony enlarged; dz, modi-

fied, tactile individuals ;

Parker and Haswell.

8,

reproductive individuals; sp, spines. From

1 Microhydra Ryderi.

HYDRA 267

jellyfish have, geologically speaking, recently come from the
sea. Hydra is, however, probably a genus that has been es-
tablished in fresh water for a long time.

The marine hydroids are, in contrast to the fresh-water
ones, very numerous. The organ-pipe corals (Hydrocorallide')
are peculiar in that they secrete a great amount of calcareous
substance, so that they were formerly regarded as belonging
to the typical corals (Scyphozoa, see page 275). They may
be easily distinguished by the absence of radial septze in the
cups occupied by the hydroid. Here belong the millepore
corals of Florida.

The tubulurian hydroids (Tubularide *) include some Hy-
droids of large size, since single individuals of Tubularia may
become six inches long. Other species grow on gasteropod
shells which are occupied by hermit-crabs (Figs. 255 and 256).
So thickly do they grow that they make a plush-like covering
on the upper part of the shell, and they have the curious habit
of building out the lip of the shell so as to enlarge the aperture.
Because they do this the hermit-crab, as it grows larger, is
not forced to exchange the shell for a larger one, and so does
not leave the hydroids on the cast-off shell to roll about on the
beach and perish.

Of the bell-hydroids, Campanularide,? one of the com-
mon representatives is Obelia,* which may be found at low
tide hanging from rocks beneath seaweed, and looking like
delicate white threads (Fig. 257). Observed under the micro-
scope each stem appears as a series of heads called hydranths
placed in zigzag fashion, one beyond the other. Another

1 Combining the qualities of Hydra and the corals.
2 From tubulus, a little tube.

3 campanula, a little bell.

+ obelos, a spit.

268

ZOOLOGY

common kind is Sertularia,! which forms rusty brown threads

(Fig. 258).
and oppositely.

All the hydranths of one stem occur in one plane

Fie. 257. — Obelia, a group of campanularian hydroid colonies.

Nat. size.

Photo. by W. H. C. P.

Both tubularian and campanularian hydroids may give rise

to jellyfishes.

<<

i
Fig. 258. — Sertularia, a small colony.
1.5 nat. size.

1 Derived from serta, garland.

These jellyfishes are formed as buds on the

hydranth, and after they be-
come able to move of them-
selves they are cut off from the
The
jellyfishes then give rise to the

parent and swim away.?

sexual products and discharge
them into the water (Fig. 260).
As in this case the life-history
of the animal consists of an
attached individual alternating
2 Fig. 259.

HYDRA 269

with a free-swimming one, we have here an alternation of gen-
erations. In other cases the jellyfish is formed but never sepa-
rated from the parent, and the eggs develop in the bud. Instill

\_ entcav.

Fie. 259. — Bougainvillea ramosa. A, entire colony, natural size; B, por-
tion of the same magnified; C, immature medusa; cir.c, circular canal;
cu, cuticle or perisarc; ent.cav., enteric cavity; hyd, polyp ‘or hydranth;
hyp, hypostome or manubrium; med, medusa; mnb, manubrium; rad.c,
radial canal; ¢, tentacle; v, velum. From Parker’s ‘Biology,’ after
Allman. This is closely allied to the New England B. supercilians,

270 ZOOLOGY

other cases a mere bud is formed which becomes full of sexual
products without ever acquiring resemblance to a jellyfish!
The jellyfish is the primitive type which has undergone a
reduction in some cases to a gonophore. It is an interesting
fact that in certain species sometimes jellyfishes and some-

end lam

Fic. 260. — Dissection of a medusa with rather more than one-quarter of
the umbrella and manubrium cut away (diagrammatic). The ectoderm is
dotted, the entoderm (end. lam.), striated; the black is a membrane be-
tween them; /, cyst containing a little sensory body; vl, ‘‘velum,”’ a shelf
to diminish the opening of the bell. Food system: mth, mouth; mnb,
manubrium, or gullet; rad.c. cir.c, radial and circular canals, parts of the
digestive cavity. Reproductive system: gon, germ-cells.

times gonophores will be produced. In the hell-hydroids the
gonophores are encased in a cuticular capsule, but in the
tubularian hydroids they are quite naked.

There are certain hydromeduse in which the hydroid stage
is unknown or known to be lacking. Here belong some jelly-
fishes of our Hastern coast, which may become twenty to thirty
centimetres in diameter (Fig. 261). Besides these the sea

1 See Fig. 254, ¢

HYDRA 271

contains many small species, which are easily captured in the
net, and which are of extreme beauty and delicacy.

Besides the Hydromedus:e, the group of Hydrozoa includes
the siphonophores.' These animals are always colonial and
free-swimming, and are among the most beautiful inhabitants
of the sea. Those who have crossed the Atlantic are ac-
quainted with the ‘ Portuguese man-of-war” (Physalia,?
Fig. 262), which often swarms in the Gulf Stream. The huge

Fic. 261. — A large jellyfish that has no hydroid stage (Zygodactyla). Re-
duced. From a drawing by A. Agassiz.
float which lies on the surface of the water serves also as a sail
by which the animal is transported by the wind. There are
other smaller, more graceful species of more typical form (Fig.
262 a). The structure of a siphonophore is very complex.
From the float hangs a central stem. Upon this stem are
budded feeding zooids (hydranth-like forms provided with
mouth and tentacles) and reproductive zooids (forms which
produce the germ-cells). There are leaf-like expansions, also,
which are rudimentary jellyfishes. All the many forms budded
on the stem are modifications of the hydroid type.
Contrasted with the Hydrozoa are the beaker animals

1 siphon, a siphon ; phorus, bearing. 2 bladder.

272 ZOOLOGY

| {IRS
j b\ :
Fria. 262. — Physalia arcthusa. } Zs é

Nat. size. After Agassiz. Y WN
\
i Wile
Fic. 262 a. — Halistemma. ter-
gestinum. The entire colony. fl {
ca, conosare; dz, dactylo- \

zooid; hph, hydrophyllium 4
or bract; net, nectoealyx or swimming-bell ; nfc, battery of nematocysts;
p, polyp; pn, pneumatophore or float; ¢, tentacle. After Claus.

HYDRA 273

(Scyphozoa!), which are, on the whole, larger. These, too,
occur both in the sessile, polyp form, and in the jellyfish form.
The sea-anemones are common examples of the polyp. They
are, for the most part, solitary, fleshy creatures, often brilliantly
colored, and therefore appropriately called by the Germans

Fie. 263. — Metridium, one of our sea-anemones. Two individuals shown

expanded. Photo. of the living animals in the water, by W. H. C. P.
“ sea-roses,”’ and in this country and in England “ sea-anem-
ones.” They are of cylindrical form, bear a circle of tentacles
around the mouth at the upper end, and have a muscular base
by which they attach themselves. They vary in diameter
from one-sixth of an inch to two feet. Some species live in
the sand, out of which they get some organic food, and at
least one species is free-swimming.

T 1 skyphos, cup; zoon, animal.

274 ZOOLOGY

Our commonest Northern sea-anemone is Metridiwm mar-
ginatum (Fig. 263), which occurs on rocky shores south to New
Jersey, but reaches its centre of development along the coast
of Maine. It varies greatly in color, some individuals being

Fic. 264.—Sea-anemone with wall partly cut away. ¢, tentacles. Muscu-
lar system: lon, longitudinai muscle; p.m, parietal muscles, or those of
the body-wall; s.m, sphincter, or circular closing, muscles; ¢.m, trans-
verse muscles. Food system: mth, mouth; gul, gullet; sgph, siphono-
glyph; mes. 1, 2,0, ‘‘mesenteries”’ of first, second, and third order of size ;
lp, lappets; ost. 1, 2, openings in mesenteries ; mes.f, mesentcrial filaments.

white, others salmon-colored or olive. The flat upper surface

bears the slit-like opening to the internal sac. Either one or
both angles of this slit have thickened edges, and correspond-
ing to this difference is a difference in the internal structure.

Inside, the central cavity is separated into compartments by

radial partitions (Fig. 264).

HYDRA 275

The coral polyp does not differ essentially from Metridium.
But it has the habit of secreting lime at its base, so that, in
course of time, a high cup is built up. The top of the cup
bears radial septa,! which are laid down in the interspaces
between the fleshy partitions such as are found in Metridium.
Since most corals, like hydroids, bud freely, and since every
bud secretes coral at its base, an extensive and complicated
limy mass may be produced. This is the way in which the
brain corals and branching corals are formed.

Fig. 265. — Coral cup of Manicina. Nat. size. Photo. by W. H.C. P.

The only coral of the northeastern United States is Astrangia
dane, which occurs north to Cape Cod. It is a beautifully trans-
parent species, and forms thin encrustations of limy matter (Fig.
266).

The Sea Walnuts or Ctenophora are a small group of exclu-
sively marine organisms that are usually placed in the group
Cnidaria, but differ very widely either from the Hydra or the
Seyphozoa. The mouth lies centrally at the lower pole of the
barrel-shaped animal, and is usually guarded by one or two
tentacles. The food-cavity runs through the axis of the body,
enlarging near the upper pole. From this enlargement a

1Fig. 265.

276 ZOOLOGY

certain number of canals run out along the surface of the jelly-
like body. The surface of the body is clad with special hair-
like bodies or cilia, which are arranged after the manner of
the teeth on a comb. A large number of combs is placed in
each of the rows running from the upper to the lower pole, and
by their incessant beating the animal is driven forward.

The body of the ctenophore is very transparent, a result of
its composition ; for it is made up chiefly of water with a small

tg ge ia) a a
Fic. 266. — Astrangia dane, a cluster of our Northern coral-polyps, resting

on limy bases of their own secretion. The animals are extremely delicate

and transparent. From a lithograph by Louis Agassiz’s artist Sonrel.
amount of pure jelly. Consequently the organism is as clear
as the sea itself, so that the animal is hard to distinguish.
Many marine animals are as transparentas the water, and there
is reason for thinking that they enjoy, in consequence, a certain
immunity from attack by their enemies. It is curious, how-
ever, that these same animals are phosphorescent, so that they
glow brilliantly in the water at night, especially after irrita-
tion (Fig. 267).

Coral reefs are almost exclusively the product of coral
polyps modified by the environmental conditions. The reef-
building corals live in shallow water from low-water mark to
a depth of one hundred feet only. Their distribution along

HYDRA Q77

the coast-line depends upon the winter temperature of the sea,
since they cannot live at a temperature below 20° C. Conse-
quently reef-building corals are confined to warm latitudes.
However, tropical shores which are washed by arctic currents,
such as the west coasts of Africa and South America, are des-
titute of coral formations. On the other hand, shores in the
temperate zone that are washed by
tropical currents, such as our Florida
coast which is washed by the Gulf
Stream, may be rich in coral reefs. Cor-
als demand undiluted sea-water, hence
they do not thrive in harbors which re-
ceive the waters of great rivers — a cir-
cumstance of great importance for the

commerce of tropical countries. More-
over, corals require a rock bottom on Fie. 267.— A sea-walnut,
z P 2 seen from the broad side
which to build, and they cannot gain a = (fdylia). Half nat. size.
foothold on shores where the cliffs de- % 44! opening; }, lat-
nee eral tube; c, circular
scend precipitously to great depths. tube; d,e,f,¢,h, rowsof
Coral reefs receive different names ac- Paddles. After Agassiz.
cording to their varying relations to the shore. Fringing reefs
are found close to the shore-line. Barrier reefs lie at some dis-
tance from land, with a body of quiet water between them and
the shore. An Atoll isa further step, in which a small island,
formerly surrounded by a barrier reef, has disappeared, leaving
a circular reef surrounding a body of water (Fig. 268). Exactly
how the central land disappears, whether by subsidence of the
sea floor as the reef grows up or by being washed away, is still
a matter of dispute.
Budding and the formation of colonies. — The nettle ani-

mals, as we have seen, are one of the groups of animals that

278 ZOOLOGY

have the habit of forming colonies by budding. In all cases
the buds arise from a definite part of the parent body and de-
velop into a definite form, often exactly like that produced from
the egg. When the buds remain attached to the parent, a
compound individual or colony is produced. These colonies
differ greatly inform. Thus among hydroids we have colonies
which produce runners, from which alone, and not from other
hydranths, new hydranths arise. In another case (Obelia),

Fic. 268. — Atoll in Fiji Islands (Nanuku Levu). The large circle of white
made by breakers indicates the position of the coral reef. A small bit of
land still remains in the interior lagoon. Photo. by Dr. W. McM. Wood-
worth. From A. Agassiz, ‘Coral Reefs of Fiji.’

one hydroid buds from the side of another and rises beyond it,
continuing the main stem of the colony. Since its descendants
do the same, the stalk is made up of successive generations of
hydranths. Sometimes the hydranths are placed close to-
gether and opposite, like the leaves of arbor vite (Sertularia,
Fig. 258). Again, there may be a main stalk composed of one
hydranth and a series of lateral branches in one plane, making
a fan-like arrangement of the colony. Or the lateral branches
may rise in any plane, producing a bushy colony. The va-
riety in the form of colony possessed even by a single species
adds to the diversity of hydroids.

In any colony a division of labor may occur among the con-

HYDRA 279

stituent individuals, or zooids. Thus in the simplest cases
among the nettle animals we have crawling zooids, or stolons,
and feeding zooids. In other species we have, in addition,
reproductive zooids, nettling zooids, and passive, thorn-like
zooids. These zooids are, in their earliest stages, equivalent,
and seem to have the power of developing into the same thing.
Nevertheless some of them develop into very imperfect indi-
viduals incapable of exercising any active function. These
organized colonies are interesting from a sociological stand-
point because they illustrate the complete subserviency of the
individual to the good of the community. This subserviency
is found in all successful colonies of animals.

Regeneration. — Closely allied to the power of budding is
that of reproducing a lost organ. Supposing the “ head ”’
(mouth and tentacles) of a Hydra to be cut off, the base will
reproduce the lost head. Suppose the base to be removed,
the head will reproduce a new base. When a Hydra is cut in
two transversely, two Hydras result where formerly there was
only one. Even three or more Hydras may arise when a
Hydra has been cut into somany pieces. Where other condi-
tions are favorable to life, you can hardly kill a Hydra by mu-
tilation. A trace of this capacity for regeneration, as it is
called, is seen also in man when a wound heals and a diseased
organ, even when partly destroyed, is made whole again.

CHAPTER XX

PARAMECIUM: A STUDY OF THE SMALLEST
ORGANISMS

THE smallest organisms have an especial interest because
they show the simplest structure and because they must have
been the earliest produced. Thus they are the nearest living
representatives of the ancestors of both the animal and plant
kingdoms. What the first organism that evolved was will
doubtless never be known, but if it were found it probably
would be invisible to the naked eye. The process of evolu-
tion has led to an increase in the complexity of the individual
and also, in the long run, to an increase in its size. These
simplest organisms are placed in the group Protozoa, a group
that is characterized by the fact that the body contains no
specialized tissues and organs, but is made up of a single cell,
and is usually microscopic. Protozoa live in water or in
moist situations. The lowest plants are known as Proto-
phyta. As it is impossible to draw a sharp line separating
the Protozoa and Protophyta, they are sometimes placed in
one group named Protista.

Although so minute, the Protista play a réle of great impor-
tance in the world and are of especial interest toman. Indeed
their work is of a sort that can best be done by an organism of
small size. In the first place many of the Protista, both
animals and plants, contain leaf green or chlorophyl. This

enables them to make use of the energy of sunlight to build up
280

PARAMG@CIUM 281

their bodies out of inorganic materials. As they grow they
divide, and this capacity for multiplication seems unlimited.
The Protista swarm upon the surface of ponds and of the sea.
They are devoured by myriads of Crustacea (Entomostraca),
whose capacity for reproduction seems, in turn, limited only
by the number of Protista. These Entomostraca, however,
constitute, as shown in more detail in Chapter X, the main
food supply of many of our most important food fishes. Thus
the chain of relations is complete between the Protista and
man.

The Protista that are without pigment occupy a very dif-
ferent niche in nature. They live on organic matter. Many
of them devour the decaying materials that are found on the
bottom of ponds. Some live on the surface of other organ-
isms, feeding upon the waste matters eliminated. But many
others have gone farther and live as parasites in the interior
of the body of other organisms. In the highly nutritious
medium in which they now find themselves they multiply
tremendously. As a result of this accelerated growth they
eliminate large quantities of substances into the body which
are often highly injurious, even bringing about the death of
the higher infested animal. Until a few years ago it was sup-
posed that the most dangerous of these parasitic Protista
were plants, but to-day we recognize that almost any group
of Protista may give rise to dangerous human parasites.
“Malaria,” yellow fever, cholera, and many other tropical
diseases of man and domesticated animals are due to Protozoa.
Many of these parasitic Protozoa are conveyed from one indi-
vidual to another by means of insects that bite persons already
parasitized. The parasites imbibed with the blood of the
victim usually develop further within the insect and, when the

282 ZOOLOGY

insect bites a healthy person, the latter becomes inoculated
with the disease. Thus biting insects are disseminators of
disease.

Protozoa were unknown to man until the latter half of the
seventeenth century, when a Dutch naturalist named Leeu-
wenhoek, by means of the newly invented compound micro-
scope, studied and described several kinds which he had found
in standing water and called animalcula or water insects.
Later, these creatures were called Infusoria because they de-
velop in infusions of organic matter in water. As the micro-
scope hecame perfected, progress was made in the study of
these organisms, but less than a century ago several eminent
zoologists maintained that the Infusoria possessed digestive,
nervous, circulatory, and reproductive organs. The proper
structure of Protozoa has been generally recognized only
within the last sixty years.

The ideas formerly entertained concerning the origin of
Protozoa were as erroneous as those relating to their internal
structure. These erroneous ideas were a tradition from a time
when even scientific men held that many of the larger animals,
such as eels, bees, and flies, were generated without parents.
This was the theory of “spontaneous generation.” In time
this theory became much more restricted. It was found that
the maggots in putrid meat are not generated “spontaneously ”’
out of the meat, but are derived from flies’ eggs, and, in their
turn, develop into fertile flies. But the idea that “ Infusoria ”
are formed out of the organic material of infusions continued
to be held until much more recently,

until Pasteur,! Tyndall,

and others proved that fluids heated to a sufficiently high tem-

perature for a long enough time, and then, while hot, sealed
1 Fig. 269.

PARAMG@CIUM 283

from contact with the dust of the air, do not develop Infusoria,
no matter how long they may be kept. This method of exclud-
ing Infusoria and other minute organisms, especially bacteria,
is employed to-day in canning meat, vegetables, and fruit.
The experiments referred to gave a death-blow to the theory of
spontaneous generation, and led to the conclusion that all
Protozoa are derived from living
germs.

Whence the living germs come
which enter the water it is not
difficult to determine. Many
Protozoa can pass into a quiescent
“ spore ”’ stage in which they may
be dried and blown about without
loss of life. Dry grass, straw,
and other substances contain
some of the germs, and others
float in the air and fall as dust
into the water. Even drinking
water may contain here and there a ean ere
an infusorian or its germ. When, coverer of the importance of
therefore, one fills a clean vessel — Pacteria in the air for disease

; and fermentation.
with pure water, and puts hay or
dry leaves in it, and lets it stand open to the air in a warm
place, it is pretty certain that there will be germs in the mixture.
The heat and the organic infusion merely facilitate their devel-

opment.

The reproductive capacity of Protozoa is so great that their
importance in the world, despite their small size, is not
astonishing. One of the early students of Protozoa, Ehren-
berg, computed that from one individual of Paramecium

284 ZOOLOGY

268,000,000 might be developed in one month by the process
of division. Apparently the division does not ordinarily go on
indefinitely, but from time to time the Paramcecia unite tem-
porarily in pairs and undergo an exchange of some of their
nuclear matter. This is doubtless the beginning of what is
known in the higher animals as sexual reproduction.

The Protozoa! are divided into four principal ciasses ar-
ranged according to the character of the locomotion. In the
simplest forms, called Rhizop’oda, the entire body changes

Fic. 270. — Amceba, the proteus animalcule. Greatly magnified. n, the
nucleus; w.v, water vacuoles; c.v, contractile vacuoles: f.v, food vacu-
oles. E.B. Wilson, ‘The Cell.”

shape and the appendages can be retracted so that the whole

body assumes a spherical mass. The simplest of the Rhi-

zopods is the Ameba.2 This type varies greatly in size, from

0.02 mm. to about 0.3 mm. It appears as a clear, glistening

body of changing outline. The body, when viewed with a high

power, shows a complicated structure. It contains various

1 Greek, protco, earliest ; zoon, animal. 2 amoibe, alteration.

PARAMM@CIUM 285

granules derived from ingested food, vacuoles of water, and a
dense though transparent, spherical or ellipsoidal body, the
nucleus, which it is often difficult to make out on the living
animal.'. The whole substance of the Amceba is mobile, so
that the internal organs have no fixed relation to one another.
Quantities of Amceba can usually be obtained for study by
gathering the mud from the edges of stagnant pools, or by

yy
ie z
£ oy gt
cvae Me a
iy/ \_)

/ Oa
£
a a

Ce PT P| \

ZH-)
e's \ a

\” m

spt ae
RU Cvae

Fie. 271. — Euglena viridis, a lash-animalcule. A-—D, four views illustrating
the characteristic movements; H and H, enlarged views of adult; F,
outline of anterior end further enlarged; G, resting stage; cy, cyst; A, fla-
gellum; m, mouth; nu, nucleus; @, gyllet; pg, pigment spot; r, reser-
voir. After Kent and Klebs.

scraping the green growth from flower-pots and letting these
gatherings, covered with a little water, stand in a fairly warm
place for two or three weeks.

The second class is that of the spore animalcules, or Spo’ro-
zoa. This class includes some of the worst parasites among
the Protozoa. Here belong the germs of “‘malaria’”’ and a
host of related diseases occurring almost exclusively in the
tropics. The Sporozoa are minute, rod-like organisms. They

1 Fig. 270.

286 ZOOLOGY

increase by transverse division; but periodically they roll up
into a sphere, form a tough shell, and divide into numerous
“spores,” which, under favorable conditions, are set free
in great numbers.

The third class, known as lash-animalcules, or Flagellata,
is well represented by a common form, Euglena (Fig. 271). It
is of microscopic size, but occurs in such numbers as often to
give a decided green color to the pools of water it inhabits. It

=< : -> is spindle-shaped, and bears a lash at
its anterior end. At the base of the
lash is a red “ eyespot.”’

Allied to Euglena is Volvox,! a

ied = spherical, multicellular organism, half
‘Ss Foe 3 j _ animal and half plant, and forming a

aa al | sort of connecting link between the
Cs Saas ve

Fic. 272. — Volvox globator. 5 ‘
Much magnified. Photo. the multicellular higher organisms.

of the living animal. Volvox occurs abundantly in our
ponds, and gets its name from its manner of revolving in the
water (Fig. 272).

To the fourth or highest class of Protozoa has been restricted
the name Infusoria formerly applied to all Protozoa. In the
Infusoria the body has a definite and more or less permanent

Protozoa (or one-celled animals) and

form. The hair-like appendages (cilia), by which they move
about or seize their prey, cannot be retracted.

Of all the Infusoria, none is more abundant than Para-
meecium. It occurs everywhere, principally in stagnant fresh
water, but also in salt water. It lives entirely on vegetable
food, and is sure to abound wherever plant matter is under-
going decay. When a culture is once started from a hay in-

1 From volvere, to roll,

PARAMECIUM 287

fusion, which takes one or two weeks, it will be found to
thrive well on corn-meal.

Since the cilia of Paramcecium are of nearly uniform size
and occur all over the body, it has been assigned to the order
Holotricha. In another order of Infusoria the cilia are greatly

Fic. 273. — A stalked Vorticella, Carchesium. Greatly magnified.
From a photograph of the living animals.
enlarged around the mouth, and on account of this difference
in size the order is named Heterotricha. As an example of the
Heterotricha, the trumpet-animalcule (Stentor!) may be
mentioned. This is found attached to vegetable débris —
sticks, stones, water-weeds, and other objects—occurring in
pools, ponds, lakes, and sluggish streams. These things should
be gathered and placed in an aquarium, when the Stentors, if
present, will attach themselves to the glass sides of the vessel.

1 Stentor, a Greek at Troy, known for his loud voice.

288 ZOOLOGY

The attachment of Stentor to objects is not permanent, for it
may loose its hold and swim free. When the animal is stained
in hematoxylin, the characteristic nucleus, looking like a chain
of beads, becomes evident.

The bell-animalcule (Vorticella) is found in pools or infu-
sions, permanently attached by a long stalk. When the ani-
mal is irritated, it contracts its stalk, which twists into a close
spiral. In other species, colonies are formed, so that a num-
ber of heads is attached to a central stalk (Fig. 273). A
colony, when fully expanded, appears like a fine, white mould
attached to a submerged object. In both of these types the
food consists of small organic particles, which are swept
into the gullet by the circlet of cilia placed around the upper
end of the body.

The Suctoria are sessile Infusoria, from whose upper surface
numerous remarkable sucking tentacles arise. By means of
these tentacles the animal can hold on to Parameecia and
other free-swimming Infusoria, from which it extracts the
body fluids. Some Suctoria are stalked, while others are un-
stalked. They are found most abundantly in standing water,
either fresh or salt, and are often attached to other animals, —
Bryozoa, entomostracans, and pulmonate mollusks.

CHAPTER XXI

THE ANCESTRY OF VERTEBRATES

SoMEWHERE out of the great variety of phyla of invertebrates
the vertebrate stem arose. The origin of this branch of the
animal kingdom has a special interest for us because to it
belong not only man but also the most of our favorite fellow-
creatures, our domestic animals, the birds, and the fishes. We
have now to consider what is known of the ancestry of verte-
brates.

In seeking the origin of any phylum we must first separate
out what is essential and universal in it from what is secondary
and special. And first of all, the phylum of vertebrates is
distinguished by the possession of an internal skeleton whose
simplest forerunner is a rod of tissue lying in the axis of the
body and running from the head to the end of the tail. This
rod is called the chorda. It is found in some simple animals
which have no other internal skeleton, and so they and verte-
brates are often classed together as Chordates. The essential
feature of Chordates are four: (1) the chorda just referred to ;
(2) gill-slits passing through the wall of the throat so that
water taken into the mouth passes out through the neck, as is
seen in fishes; (3) a nervous cord that lies wholly on the dorsal
side of the animal; and (4) a heart which lies on the ventral
side. Any animal which can show this combination of charac-
ters, or any of them, thereby reveals its affinity to the verte-

brates, no matter how lowly it may be.
U 289

290 ZOOLOGY

Not less important are the points in which chordates resem-
ble other animals. First of all they are bilaterally symmetrical
animals, at least in their young stages; secondly, they are seg-
mented animals, and they have ventral organs repeated as in
other externally ringed animals. Consequently they show
their affinities to the great groups to which annelids and ar-
thropods also belong. A diagram showing the relationship
of chordates to the invertebrate groups already studied would
be something like this:

Chordata

y

vy,
Arthropoda fe

Annelida

|
Echinodermata | Mollusea
te

Scolecida !

Coelenterata
Porifera
ne

Protozoa

Applying now the four criteria of chordates enumerated
above, we find that they discover strange associates for the
vertebrates. Of these the most remarkable is a group long
known as Tunicates, animals which in some cases are attached
and in others float on the surface of the sea. Tunicates show
a great variety of external forms (Fig. 274), but they all reveal
their chordate nature in their youthful forms. Thus in the
tadpole stage (Fig. 275) we see the chorda (noto) in the axis
of the body, the nerve-cord (med) above it; and one of the
throat slits (sé7g) already formed. When the animal attaches
itself, it loses its tail and chorda, but the number of gill-slits

1 Includes flatworms, roundworms, rotifers, bryozoans, and brachiopods.

THE ANCESTRY OF VERTEBRATES 291

greatly increases. The body now shows (Fig. 276) two open-
ings; one inhalent (0), and one exhalent (at). Some species,

THALIACEA>

Se
t Ascidiids Cynthiids Compound
Moelgulids Ascidians

Fre. 274. — A group of Tunicates showing the attached forms (Ascidiacea)
both simple (left-hand side of picture) and compound (at right); the
oceanic forms (Thaliacea) that swim near the surface; and the small tailed
forms (Larvacea) that look like the larval stages of higher Tunicata. From
Cambridge Natural History.

after becoming attached, form colonies by budding new zooids

upon the side of their body. The whole colony may have a

common exhalent opening (Fig. 277, cl).

Below the tunicates is a small group of worm-like animals

bo
eo)
bo

ZOOLOGY

Fic. 275. — Diagram of the metamorphosis of the free, tailed larva into the
fixed Tunicate. A, stage of free-swimming larva; B, recently fixed larva;

C, older fixed stage; adh, papillae for adhesion to the rock; afr, ‘‘atrial”’
cavity; cil.gr, ciliated groove on wall of pharynx; end, glandular groove
in pharynx; ht, heart; med, ganglion of heart; n.gn, brain; noto, noto-
chord; or, mouth; rect, rectum; sens.ves, sense space; stig, throat
(gill) slits; sol, shoot from which buds arise; ¢, tail. From Korschelt and
Heider.

THE ANCESTRY OF VERTEBRATES 293

whose affinity with chordates is a little less certain. These
animals belong to the genus Balanoglossus (Fig. 278); they
live in the mud of the seashore
and have doubtless lost many
organs as a result of their
burrowing habit. The elon-

Fie. 276.— Ciona, a simple Fie. 277. — Two small colonies of
Tunicate. 0, mouth; at, open- compound Tunicates (Botryllus).
ing of atrium, or exhalent The ‘“‘zooids”’ are grouped about a
opening; st, stolon. After center, have a common cloacal
Leuckart and Nitsche’s dia- opening (cl), but separate mouths
gram. (or). After Milne-Edwards.

gated body is divisible into three parts: the proboscis at the an-
terior end; the collar; and the trunk. In the trunk an anterior
region containing gill-slits (br, Fig. 279), and a posterior region
that is without gills can be distinguished. The mouth lies
between the proboscis and collar and leads into a nearly

294 ZOOLOGY

straight food-canal, in the anterior part of which there are
numerous openings to the exterior — the gill-slits. There is
a small sac, lying dorsal to the

pharynx, which is regarded
as a chorda. The brain is
dorsal, and there are both
dorsal and ventral nerves.
If Balanoglossus is indeed a
chordate, it isa degenerate de-
scendant of a primitive form.
Above the tunicates, and
showing the clearest possible
affinities to the fishes, is a re-
markable animal about 5 zen-
timetres long. It lives almost
buried in the sand of the sea-
shore in various parts of the
world, and is known as Am-
phioxus (Fig. 280). It is
bilaterally symmetrical, or
nearly so, and has a distinctly
segmented body. The food-
Fia. 278. — Balanoglossus, the acorn- canal runs nearly straight
tongued worm. The proboscis at the .
anterior end is at the top of the figure through the body and is
(arty outside); behind an 2 perforated in the pharynx

long, brown-red trunk. Nat. size. by 90 or more pairs of gill-
Photo. of livinganimal by W. H.C. P.

slits. These do not, however,
open directly to the exterior, but into a large chamber that has a
single posterior connection with the outer world. Through the
axis of the body, from the tip of the snout to the end of the tail,
runs the chorda, which, in this animal, is a sort of jelly-like rod

THE ANCESTRY

(Fig. 281, nch).
tem (br and sp. cd) lies above the
chorda; it begins in a slight en-
largement whose cavity communi-
cates with the exterior by a nasal
pit and carries a large pigmented
“eyespot” (e. sp). The blood
system consists of a ventral vessel

The nervous svs-

carrying blood forward and a dor-
sal one carrying it backward.
The ventral vessel connects with
the dorsal vessel by a pair of
eill-
gill-
slits), and from the pharynx the
The
direction of the dorsal current in

vessels running along each
arch (br.sep, between the

blood runs toward the tail.

the trunk of Amphioxus is thus ex-
actly opposite to that of worms.
There is a series of kidney tubules
(nph) much resembling those of
annelids, and the reproductive
cells are formed in glands that are
repeated in many segments of the
body.
vertebrates, the outer skin con-

In Amphioxus, as in in-

sists of a single layer of cells, below
which lie cells of a connecting
nature. Finally, on the exterior a
pair of folds, like fins, runs con-
tinuously from near the mouth to

the outer pore of the gill-chamher.

OF VERTEBRATES 295

pe

RUTTEN

Fic. 279. — Drawing of entire
Balanoglossus. br, gills; co,

collar; gen, genital ridges;
hep, ridges lying over liver;
pr, proboscis. From Parker
and Haswell; after Spengel.

296 ZOOLOGY

This is believed to be the forerunner of the appendages of
vertebrates.

This review of the most primitive chordates indicates that
the ancestors of vertebrates were elongated, worm-like, seg-

ml, pl

alrp venl fr

io,
cir’ “i ih rbd gon arr tee ae

Fic. 280. — Amphiorus lanceolatus. A, ventral; B, side view of the entire
animal. an, anus; atrp, atriopore; cd.f, caudal fin; c7r, cirri; dors.f,
dorsal fin; dors.f.r, dorsal fin-rays; gon, gonads; mtpl, metapleure;
myom, myomeres; nch, notochord; or.hd, oral hood; vent.f, ventral fin;
vent.f.r, ventral fin-rays. After Kirkaldy.

mented animals. In this respect they resembled annelids,
but in certain respects the internal organs of vertebrates are
inverted as compared with those of invertebrates thus : —

INVERTEBRATES VERTEBRATES
Main nerve-cord . . . . . «|. ventral dorsal
Heaths AAs dorsal ventral
Direction of flow in areal v Seal
im brunle 4. 4s toward head toward tail
Direction of flow in dures: Sect
intrunk . .. . . . . .| toward tail toward head

It will be seen that the relations of the above parts in verte-
brates become the same as in Invertebrates if we think of the
former as turned on their backs. It seems, at first sight,

RTEBRATES

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THE ANCESTRY

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tral movement of the mouth from the neural to the hemal side.

CHAPTER XXII
THE SMELT: A STUDY OF FOOD SUPPLY

GREEN plants only can transform inorganic substances into
living matter with the aid of the energy of the sun. Yet it is
upon such inorganic substances that all living matter eventu-
ally depends for its increase, and it is from solar energy that
all vital energy sooner or later comes. Accordingly, animals,
including man, must get their energy either from plants or
from plant-devouring animals.

The total amount of energy clerived from the sun is enor-
mous. On the land this energy is absorbed by forests, by the
grasses of prairies and meadows, and by growing crops; and
is by them transformed into new, living material. Man is
constantly working to increase the proportion of solar energy
that becomes fixed in the crops, but only a very small propor-
tion of the surface of the land is yet under cultivation. There
are great tracts, such as deserts and rocky places, where the
falling energy seems to be quite wasted, and the same seems
to be true of the water surface of the earth, which amounts to
three-fifths of the whole (Fig. 282). It is, however, very far
from the truth that the solar energy falling on the sea is lost,
for the entire surface of the sea swarms with microscopic green
organisms which are to the sea what the grass of the fields is
to the land. The green plants of the ocean are the food of the
small Crustacea called Entomostraca (p. 156), and these,
as we saw in Chapter X, in turn are the food of fishes. In

298

THE SMELT 299

employing fish as food man is utilizing the energy that falls
on the sunlit ocean (Fig. 282 a).

So great is the expanse of the ocean that the amount of
surface alge and of the fishes is practically unlimited. No
nation has utilized to the utmost the possibility of fish food
from the sea, yet some derive their main sustenance from fish-

Fig. 282. — The Open Sea.

eries. This is particularly true of Holland, and it is an old
proverb in that country ‘‘ that the foundation of Amsterdam
was laid on herring bones.”

The principal fisheries in the United States are those of cod,
herring, mackerel, and salmon. Boston and Gloucester fish-
ing fleets alone in the year 1902 supplied about 33,000 tons of
codfish to our markets, and probably twice as much was taken
by other nations combined. The herring fishery, which reaches
its greatest importance on the northwestern coast of Europe,
has engaged annually 100,000 men and over 300 larger vessels
during the past quarter of a century. As many as 22 million
herring have been caught in two days by fishermen of a single
English town, One of the greatest fisheries of the United

300 ZOOLOGY

States is that of the salmon; over three million cases con-
taining thirteen to fifteen million fish are packed annually on
our Pacific coast. Over 43 million salmon were caught in
Alaska in one year (1908). These figures, which are so large

Fic. 282 a.— The Return of the Fishermen. From a painting by Ber-
thelemy.

as to be difficult to grasp, give us a faint idea of the vast-
ness of the process by which the energy absorbed by the
microscopic organisms of the sea is utilized as food by man.
Fish are employed by man, not only as food, but, heing some-
times obtained in greater numbers than the market requires,
they have been used to fertilize the land. Most coastal
states have declared it illegal to use fish as fertilizers of land,
and there is now little excuse for doing so. Modern canning
methods make it now possible to utilize even the largest

THE SMELT . 301

catches; the excess is immediately preserved to be used in
periods of scarcity. The
bones and scraps from can-
ning factories may well be
used in the manufacture of
fertilizers, for they are rich

”

in phosphorus and other im-

eye; ex.br.ap, external

Biology.

portant foods for plants.

“

Fish culture. — Excessive
fishing has depleted many
rivers in which fish were
formerly abundant. An at-
tempt has been made, with
more or less success, to re-
stock such streams. Fish
are artificially hatched, and
the young (or fry) are
shipped to the streams need-
ing to be restocked. The
United States maintains 49

From Parker :

i m

an, anus; c.d.f, caudal fin; d.f.1, d.f.2, dorsal fins; e,

Side view of dogfish (Afustelus antarcticus), with a strip of skin in the middle of the body removed
branchial apertures; 1.1, lateral line; mth, mouth; myc, myocommas; mym, myomeres; na, nasal aperture ;

pet.f, pectoral fin; pv.f, pelvic fin; sp, spiracle; v.f, ventral fin.

such fish hatcheries, which g : ia ae

in 19064 distributed © a s
1,250,000,000 fish. In ad- iS <
dition, many states maintain is
independent hatcheries, so 8
that the total number of s
young annually hatched and A
set free by all our hatcheries 3
must approach two billion. 99 8
Of course a large proportion . 3

io

of these young fish are de-

02 ZOOLOGY

eo

stroyed before they reach maturity, but there can be little
doubt that vast numbers survive to breed.

Fishes are one group of the vertebrates, or back-boned ani-
mals. Vertebrates are characterized by the possession of an
internal skeleton that supports the soft parts of the body, by
the possession of two pairs of limbs, and by paired openings
leading from the throat to the outside, which last are found
in the higher forms in the embryonic stage only. In the fishes

Fig. 284. — Salmo fario. a.l, adipose lobe of pelvic fin; an, anus; c.f, caudal
fin; d.f.1, first dorsal; d.f.2, second dorsal or adipose fin; 1.1, lateral line; op,
operculum ; pet./, pectoral fin; pv.f, pelvic fin; v.f, ventral fin. After Jardine.

these openings are lined by finger-like processes into which the
blood flows. These are known as gills and it is in them that
the blood takes oxygen from the water. The appendages of
fishes are used as paddles in the water and are known as fins.
The tail is well developed and, by its powerful side-blows in
the water, propels the fish rapidly forward.

Classification. — Fishes are classified into five groups, the
lowest of which contains the lamprey eels. The next higher
in organization (cartilagenous fishes) includes the sharks,
skates, and rays.'. The third group (the bony fishes) includes
the vast majority of our common fishes. A fourth group —

1 Fig. 283.

TUE SMELT 30:

QO

(armored fishes) Ganoids — was in former geological times
much more abundant than now, but still populates the waters
of our Central States. The fifth group is that of the Lung-
fishes (Dipnoans), which includes a few rare fishes that live
in the mud. As the bony fishes are the best
known and most widespread we may take
one of them, the brown trout (Fig. 284), for
an anatomical study.

The general form of body.—- Three regions
may he distinguished ; viz. head, trunk, and
tail. The head bears the mouth and many
organs of special sense. Its conical form
facilitates passage through the water. The
head is encased in large, bony plates; the
trunk is covered by scales; and the tail
carries a thin membrane.

Fie. 285. — One of

Die: trumle bears: ss avranan sortase

two pairs of appendages and three median
appendages in addition to the tail. The
plates and scales constitute the external
skeleton, which is developed in the skin.

bre of the tail of

thetrout. CN, the
centrum ; N.A,
neural arch; WN.

SP, neural spine;
H.A, hemal arch

: eee cae aes (because toward
The internal skeleton consists of an axial ena: Ae aie.
portion replacing the chorda. Thisismade From Parker and

: : Haswell.
up of dice-box (or hour-glass) shaped bodies,

each of which bears ahove a bony arch, which protects the
main or dorsal nerve and supports the median fin (Tig. 285).
Below, each bears a pair of slender bones, the ribs in front of the
anus and the ventral arches behind. The brain-case consists of
numerous bones, some of which arise in the skin and others be-
long to the axial skeleton (Tig. 286). Here on the head skeletal
parts of widely different origin come together into one cranium,
and even form parts of one and the same bone. In ourownskull

ZOOLOGY

304

skin origin, and

the same is true of the thin bones that make the sides and roof

bones that carry teeth are of

the parts of the

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tinuation of the vertebree of the axial skeleton.

THE SMELT 305

In addition to the axial skeleton there is the skeleton of the
anterior and posterior appendages. The skeleton of each
pair of appendages is borne upon a bony ring which nearly
encircles the body. These are called respectively the shoulder
and pelvic girdles. The skeleton of the fin consists of a row
of cylindrical bones which bear at their outer extremities
the horny rays that support the fins.

Organs and function of nutrition (Fig. 287).— The large
mouth bears teeth not only on its Jaws but also on its roof (vo).
The whole of the interior of the mouth was, in the ancestors
of fishes, covered with scales of the same sort as those that
covered the body just outside the mouth. All teeth have their
origin in such fish-scales. In early fishes the number of teeth
was large and the position undefined, but in the higher animals
the number has become limited to a single row on each jaw.
At the hinder part of the mouth are four vertical gill-slits
(ph), fringed by a bony straining apparatus, the gill-rakers.
The water that has been taken in through the mouth is forced
out through the gills by closing the mouth in front and raising
its roof so as to expel the water. The remainder of the food-
canal consists of a stomach that is twisted on itself and of
an intestine which usually forms either no convolutions or
only the simplest. The liver (7) communicates by a tube
with the anterior part of the intestine, and is provided with
a large gall-bladder (g.bl). Immediately below the liver
opening is a bunch of hollow tubes called the ceca (py.c).
These are also digestive in function. An air-bladder (a.6/) lies
just over the intestine, and in front it opens into the pharynx
(pn.d). The air-bladder of fishes functions so as to enable
the fish to vary the volume of gases in the body and thus to

vary its specific gravity. It is often spoken of as an organ of
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THE SMELT 307

flotation, and in it the lungs of land vertebrates seem to be
foreshadowed.

Respiration. — The first stage in respiration is carried out
in the gills, where the oxygen in the water is picked up by the
blood which circulates in them. The second stage of the res-
piratory process occurs in the tissues to which the blood gives
up its oxygen.

Organs of circulation. — Beneath the pharynx of the trout
there is a heart, consisting of two chambers, an auricle and a
ventricle. The auricle receives the venous blood from the
trunk directly and that from the intestine after it has passed
through the liver, where it relinquishes most of its food. The
ventricle is more muscular and passes into the aorta, as the
main vessel leading out from it is called. Together they force
the blood through the gills, where it is purified and from which
it passes to the head, trunk, trunk-walls, and viscera. The
blood, as in other vertebrates, contains red blood corpuscles.

The organs of excretion are a pair of kidneys (hd), lying all
along the dorsal wall of the abdomen above the air-bladder.
In early development each kidney consists of a series of tubules,
one for each segment of the body, as in annelids. These
tubules collect fluids from the body-cavity as well as from the
blood-vessels and convey it to the outside.

Organs of reproduction. — The number of eggs laid by
most fishes is very great, and so fishes have correspondingly
large ovaries. The germ-glands both of the female and male
lie along the sides of the body-cavity, and both open to the
exterior at a point immediately behind the vent (w.g.s). The
eggs and sperm are both thrown out into the water. There
fertilization of the eggs (7.e. union with a sperm) takes place
and development begins.

308 ZOOLOGY

Musculature.— The muscles may be classified, like the
general parts of the body, into muscles of the trunk (Fig. 283)
and tail and muscles of the head, including those of the jaws,
tongue-bones, operculum, and gill-arches.

The nervous system consists of the brain and spinal cord
and of the nerves supplying the skin, sense-organs, viscera,
and limbs. The brain (Fig. 287, crb, etc.) is by far the largest
mass of the nervous system because it receives nerves of general
sense and probably has a general control over the behavior
of the animal. It is divided into three parts, sometimes called
fore, mid, and hind brain. In the higher vertebrate classes
these parts develop in different. proportions.

Sense-organs. — The organs of chemical sense reside in the
olfactory sac on the snout. The lips of the sac have closed
near the middle, leaving a front and rear opening through
which the water rushes. Other organs of chemical sense are
the organs of the lateral line, which at its anterior end di-
vides into many branches running over the head. Originally
the sense-organs of this line were distributed along the bot-
tom of a sort of trench. Now, however, the trench is cov-
ered over by the skin and scales forming a canal. The scales
are perforated at intervals to connect the outside with the
interior of the canal. There is good reason for thinking that
the ear is only a specialized part of the lateral line organ, and
that is where it got its semicircular canals. There is also an
otolith in each ear which probably assists in the equilibrium
of the fish. The eye of the fish has to be used under the
water. Our eyes are not fitted for seeing under water as
our lens is too flat. In the case of the trout the lens is
nearly spherical and is forced back towards the retina. Rays
from the water will not be bent on entering the lens, which

THE SMELT 309

has about the same specific gravity as water, but will be se-
verely bent as they leave it. This accounts for the small dis- |
tance between the lens and the retina.

The smelts belong to the bony fishes and are related to the
trout. They are preéminently inhabitants of the northern
temperate zone, since all but one of the ten genera occur only
there. They are small marine fishes, and although a few are
inhabitants of the deep sea, most live near the shore, and in the
spring ascend rivers to spawn. Some of them have become cut
off from descending to the sea, and live permanently, as “ land-
locked” forms, in fresh water. Such “ land-locked ” indi-
viduals are of smaller size than the marine ones. The food of
smelts, like that of other salmons, is chiefly animal, consisting
of smaller fishes or insects, small crustaceans, and mollusks.

Smelt are of considerable economic importance, since they
share with other members of the salmon family a delicately
flavored fiesh. Our Atlantic form (Osmerus! mordax?), which
ranges from Delaware Bay northward, is caught most abun-
dantly in Maine. The total Atlantic smelt fishery is valued at
$125,000. Smelt eggs are artificially hatched and planted in
rivers previously uninhabited by them. Smelt are said to
return to these rivers after spending the winter in the sea.

The family Salmonidez, which in its widest sense includes
the smelts,? comprises some of our most important food fishes.
It is distinguished from other families of spineless finned fishes
by having both ventral (v.f, in Fig. 284) and adipose fins (df,
Fig. 284) present. The head is naked, but the body is scaly
and rounded.

1 osmerus, odorous; the Greek name is the equivalent of the English ‘‘smelt.”’

2 Biting.

3 By recent authors the smelts are assigned to a distinct family, the Argen-
tinide.

310 ZOOLOGY

Besides the smelt there are, in this family, numerous impor-
tant species. The salmon proper? are restricted to the north
temperate and arctic regions, and live either in the sea, migrat-
ing to fresh water to spawn, or exclusively in brooks and
lakes. The migrations of salmon from the sea up the rivers
are remarkable. Hundreds of miles are sometimes journeyed,
rapids swum, and falls leaped, for the purpose of laying eggs
in some remote lake. At the end of their journey the eggs
are laid and male and female parents die. On the Atlantic
coast the Penobscot River has the most important run of
salmon. The Pacific salmon pass up the Sacramento and
Columbia rivers, and up many rivers of British Columbia and
Alaska. In these rivers the fish are caught as they ascend to
breed. Such is the greediness and lack of foresight of the
canning fisheries on the Columbia River that very few salmon
are permitted to pass the nets of the canning factories, and
consequently the apparently inexhaustible supply of this fish
has been immensely reduced and threatened with destruc-
tion, but it will probably be preserved by the assistance of
artificial hatching.

The trout, of which there is a number of kinds on both
continents, is commercially much less important than the
salmon proper. Asa result of overfishing, and the pollution
of streams by factories and sewage, this fish is disappearing
from Eastern waters.

The whitefish, of which we possess many species, is exclu-
sively an inhabitant of fresh water? and is derived chiefly from
the Great Lakes. Its teeth are almost completely absent, or
very small; it feeds almost exclusively upon small arthropods
and mollusks. It is of very great commercial importance,

1 Fig. 284. 2 Vig. 288.

THE SMELT 311

its fisheries being valued at nearly three million dollars a
year.

Fie. 288. — Coregonus, the lake whitefish. Much reduced. From Goode.

Leaving now the salmon, we may briefly consider some of
the other more important families of bony fishes.

Fig. 289. — Morone americana, the white perch. The fish is searching for
food along the bottom of the aquarium, an instinct which it shows in
nature also. About one-third nat. size. Photo. of living animal by Dr.
R. W. Shufeldt, from ‘‘Bull. U. 8. Fish Com.,”’ 1899.

312 ZOOLOGY

The darters are spiny-rayed fishes of small size, from four
to seventeen centimetres long, brightly colored, and with well-
developed pectoral fins. They live in clear streams, half
concealed under stones, and are most abundant in the Missis-
sippi drainage basin.

Fic. 290. — Eupomatis gibbosus, the common sunfish. Two-thirds nat.
size. Photo. of living animal by Dr. R. W. Shufeldt, ‘‘Bull. U. 8S. Fish
Com.,”’ 1899.

The perches are a widespread family, represented in this
country chiefly by the common yellow perch of the East, the
“wall-eyed pike” of the Great Lake region, and the white
perch of the Atlantic coast (Fig. 289). These fish have an
oblong, compressed body covered with small scales; they are
highly rapacious, and are believed to be destructive to the
young of other species of fish. They are esteemed as food,
although not to the extent of annihilation.

THE SMELT 313

The sunfishes! have a perch-like form, but have only one
dorsal fin instead of two. They live in fresh water, have
rapacious habits, are brilliantly colored,
and build nests in the sand, which the
male watches over and defends with
courage. Some species living in the
Great Lakes are known as black bass, or
rock bass. The small species, with the
brilliant red edge to the operculum, is
called pumpkinseed.

The toadfishes (Fig. 291) are repre-
sented in our faunas by a common
species which lives under stones in har-
bors and attaches its eggs to the under
side of stones. It is a vigorous fighter.

The sculpin (Fig. 292) is closely re- Soy
lated to the toadfish. Like the latter, Fic. 291.— Batrachus tau,
it has a broad head and nearly scaleless com Me ea Sn
body. The pectoral fins are large, and size. Photo. by W. H.
the two dorsal fins extend along the ee
greater part of the back. Allied to the foregoing is the rock
eel (Fig. 293), which is sometimes brought up in the seine from
a depth of 8 to 10 fathoms.

Fic. 292. — The little sculpin, Acanthocottus. Two-thirds nat. size.
Photo. by W. H.C. P.

1 Fig. 290.

314 ZOOLOGY

The silversides are especially abundant along our Atlantic
coast. They have an elongated, somewhat compressed body,

Frag. 293. — Pholis, the rock eel. Right side. Nat. size. Photo.

and a broad, bright silvery band on the sides, against a green-
ish general body color. The dorsal spines are slender. The

Fic. 294. — Gasterosteus pungitius, the nine-spined stickleback ; male (above)

and female near the nest in rushes. The female is about to deposit its
eggs in the nest.

THE SMELT 3815

fish swim near shore, in dense schools. One species on the
California coast is known as a “smelt,’”’ and is a good food fish.

The sticklebacks are small, elongated fishes, having an
extremely slender tail and a large mouth. The dorsal fin

Fic. 295. — Gasterosteus bispinosus, the two-spined stickleback. Above,
nest with eggs, and male entering. Below, male depositing its milt on
the eggs.

Figs. 294 and 295 are reproductions of water-color paintings in the Mu-
seum of Comparative Zoology at Harvard College.

is preceded by two or more large, isolated spines. The fishes

live in either fresh or brackish water. In some of the species

the male builds an elaborate nest from bits of aquatic plants,

firmly united by a special sticky secretion. The nest, which

316

ZOOLOGY

is built among the plants of the stream, consists of a short
cylinder, through the horizontal cavity of which the fish can
lie while it deposits its eggs. The male guards the single nest,

Fic. 296.— Gadus morrhua, the codfish. About one-seventh nat. size.

After Storer.

and is polygamous, @.e. fertilizes in the one nest the eggs from

various females (Figs.

Fic. 297.— Outline of one
of the flatfishes, seen
from the upper side,
reduced. From ‘‘Cam-
bridge Nat. Hist.”

294, 295).

The codfishes, among the most im-
portant of food fish, have ventral fins,
without spines, and jointed fin-rays,
well-developed tail fin, and barbel on
chin. Our common codfish (Fig. 296)
occurs over the whole of the North
Atlantic; but the most important fish-
ing localities are the banks near New-
foundland, especially Grand Bank.

The flatfishes are peculiar among
fishes in that they have the habit in the
adult stage of lying on one side. In
consequence the under eye migrates to
the upper side, so that both eyes come
to lie on the same side of the body.
The mouth also tends to become unsym-

THE SMELT 317

metrical. The flatfish, consequently, illustrates well the prin-
ciples of self-adjustment to a peculiar environment (Fig. 297).

The catfishes have four to eight long barbels around the
mouth, and have no scales on the body (Fig. 298). They
are most common in South America, but there are a large
number of species in the United States, mostly found in the
Mississippi Valley and the Great Lakes, inhabiting deep or
sluggish waters, and living in the mud. The common New

Fic. 298. — Ameiurus nebulosus, the catfish. About one-half nat. size. Photo.
of living animal by Dr. R. W. Shufeldt, ‘‘ Bull. U. S. Fish Com.,”’ 1899.

England species is Ameturus catus. It was with reference to
our common New England species, the bullhead or horn-pout,!
that Thoreau wrote that they are ‘a bloodthirsty and bully-
ing race of rangers, inhabiting the river-bottoms, with ever a
lance at rest and ready to do battle with their nearest neigh-
bor.” The stiff, jagged rays of the pectoral fins can make
severe wounds. The great catfish of the Mississippi River
may weigh up to ninety kilograms, and, like most other
species of catfish, is much prized as food.

The suckers are characteristic North American fish
abundant in every creek, and consequently known to every

1 Fig. 298.

”

318 ZOOLOGY

lover of woods and brooks. The lips are thick, and drawn
down at the corners.|. They are rather sluggish fishes, feed
on small aquatic insects, and suck up mud. They are not
generally esteemed as food, inasmuch as their flesh is coarse

oe

Nina

Fia. 299. — The brook sucker. After Goode.

and very full of bones. In the Mississippi Valley, however,
they are so abundant and large that they are of some commer-
cial importance.

The term “ minnow ” is applied to two distinct families of

Fig. 300. — Fundulus heteroclitus, a killifish or shore minnow. Nat. size.

small fish. One of these is also known as “ killifish.”” The

killifish have a broad head covered with scales, and have well-

developed teeth in the mouth. They occur in schools in

shallow water along the shore, and ascend streams to their

source. They are carnivorous, and feed at the surface. In

one species from the Southern coast, the male is only about
1 Fig. 299.

THE SMELT 319

two centimetres long, and is the smallest known vertebrate.
Our commonest species on the shore or in brackish water
is Fundulus! (Fig. 300). The minnows of the other family
have a narrow head without scales, and with few teeth in the
mouth. They occur exclusively in fresh water, and are known
as ‘‘shiners.” The “ goldfish ” is related to this group.

The pike and pickerel (Esox *) are roughly cylindrical fishes,
with large mouth, elongated, depressed jaws, and strong,

Fig. 301. — Lucius luctus, the pike. About one-fifth nat. size. Photo. of
living animal by Dr. R. W. Shufeldt, ‘‘Bull. U. 8S. Fish Com.,’’ 1899.

hooked teeth. They are large and voracious fresh-water
fishes, confined, with the exception of a single species, to the
United States. The “muskallunge” of the Great Lakes
reaches a length of two metres. It is, fortunately, some-
what rare, otherwise there would be few other inhabitants
of our large streams.

The shad is a representative of a family — the herring fam-
ily — which has played an important part in the civilization
of Europe. The Emperor Charles V. said that the herring
brought greater wealth to the Netherlands than did America

1 fundus, bottom.
2 (sox, a fish living in the Rhine, mentioned by Pliny.

320 ZOOLOGY

to Spain. Our common shad! ranges from Newfound-
land to Florida With the Pacific salmon and cod it is
commercially one of our most important fishes, for the catch
of Atlantic shad for 1902 was valued at nearly one million
dollars. The Pacific coast has been successfully stocked with
shad from the Atlantic. The Atlantic shad, like the salmon,
migrate up streams to deposit their eggs. The alewives have
the same habit. The herring, on the contrary, spawn in the
sea, As the common name, allied to the German Heer, an

Fic. 302. — Alosa sapidissima, the shad. After Goode.

army, implies, they travel in great schools. The menhaden,
which also occur in great schools, have of late years been de-
stroyed in vast numbers to make fertilizers.

The eels are easily distinguished by their serpent-like form,
the absence of ventral fins, the long dorsal fin, and the rudi-
mentary or absent scales. These fish occur all along our coast,
and ascend streams. During the day they lie hidden in mud,
and at night they feed, their principal prey being small aquatic
animals, the young of other fish, and shrimps and crayfishes
during the molting period. On account of the narrowness of

1 Alosa sapidissima; Alosa, from Saxon allis, old name of the European
shad ; sapidissima, most delicious.
2 Fig. 302.

THE SMELT 3821

the gill-opening, they may live for some time out of water in
amoist place. The reproduction of the eel was long a mystery.
All sorts of creatures have in past times been supposed to pro-
duce them, ranging from the gods to water beetles. They
have even been thought to be generated from slime. We now
know, however, that there are both male and female indi-
viduals ; that the males live chiefly, but not exclusively, in the

Fic. 303. — Siphostoma fuscum, the pipe-fish. Nat. size. Photo.

sea; that reproduction occurs chiefly in the sea; and that the
young females come from the sea and pass up the rivers during
the spring.

The pipe-fishes and their allies! include a number of aber-
rant forms. Some of these are greatly elongated, like the pipe-
fish proper (Fig. 303) ; others are shorter and stouter, like the
“sea-horse.” All have a prolonged snout, and usually a
long, slender tail. The body is encased in bony plates, and
the male is often provided with a brood-pouch, in which the
developing young are carried.

1 Lophobranchii.

322 ZOOLOGY

Having considered the bony fishes in detail, we may take
up the other classes of fishes.

The lamprey eels, or Cyclostomi, are the only parasitic
vertebrates. In the adult stage they either live attached to

Fic. 304. — Petromyzon, thelamprey. One-fourth nat. size. After Goode.

the outside of other fishes, sucking their blood, or else they
may penetrate into the body cavity. They do not bite, be-
cause they have no lower jaw, and are known as “ round-
mouthed ” eels.!. Lampreys are found in the seas and in the
rivers of the temperate zones. They occur on our Eastern
coast and ascend rivers; others live in the lakes of New York,

Fig. 305. —Acipenser, the sturgeon. One-sixteenth nat. size. After
Goode.
in the Great Lakes, and in the Mississippi Valley. In Europe
they are much esteemed as food.

The sharks and rays (Selachians) include all inhabitants
of the sea. They may be distinguished from the bony fishes
by the rough skin, beset with spines, and by a skeleton that
is made not of bone, but of cartilage. We have a number

Vig. 304,

wy

THE SMELT 323

of sharks on our Northeastern coast, of which the dog-fishes
and the sand-shark are the commonest (Fig. 283). They are
all carnivorous animals and powerful swimmers. They feed
on the larger crustaceans and fish.

The living Ganoidei are a remnant of a very extensive group

which existed in geological times. North America is especially

Fig. 306. — Lepidosteus, the garpike. One-cighth nat. size. After Tenney.

rich in existing representatives of this group, as of several
other old groups, such as the turtles, tailed amphibians, and
the king-crab. Of the five families of ganoids, four are repre-
sented in this country. In the following four paragraphs a
type of each of the native families is considered.

The sturgeons have five rows of hony scales on the trunk
and four barbels on the head.!. They occur both in the sea

Fig. 307. — Amia calva, the bowfin. One-sixth nat. size. From Leunis.

and in the Great Lakes and the rivers of the Central States.
Although of large size, they feed for the most part on small
aquatic animals, such as worms, insect larvee, and small fish.
The flesh of some species is much used as food; the eggs taken
from the ovaries (roe) are pressed into a delicacy known as

“ caviar.”
1 Fig. 305.

From Dean, after Ginther.

Reduced.

308. — Ceratodus forstert.

Fia.

ZOOLOGY

The spoonbill, which has an elon-
gated, flattened snout and is almost
without scales, is a large fish found
in the Mississippi River. It is also
called “ paddle-fish ” or “ duck-bill
catfish.” It becomes two metres
long, and seeks small animals in the
mud, which it stirs up with its snout.

The garpikes are known by their
long snout (Fig. 306). They are
completely clad in an enamel coat
of mail. They are of sluggish
habits, but voracious, and their
flesh is valueless as food. One
species is found in China, the others
in the rivers of North America.

The bowfin (Amia !) occurs in the
rivers and lakes of the United
States. Ithasashort body, a blunt
head, and a long dorsal fin (Fig.
307). It is the sole survivor of a
formerly large family.

The Dipnoi? include only three
rare foreign forms, which seem to
form a transition between fishes and
the higher groups, for some of them
have lungs in addition to gills.
From some such lunged fishes must
the amphibia have arisen (Fig. 308).

1 Ancient name of a fish.
2 dis, twice ; pnoe, breath.

CHAPTER XXIII

THE FROG:—A STUDY OF THE ORIGIN OF LAND
LIFE

Tr is certain that the primitive animals lived in water because
all the lowest forms that we know to-day are aquatic and dry
up at once if left in the air. Only some of the higher and
more specialized forms have been able to live on dry land.
Such are the insects, spiders, certain parasitic forms, and the
higher vertebrates. There are a few scattered, terrestrial rep-
resentatives of other groups, such as the earthworms, certain
Crustacea (the wood-lice), and land snails. Animals that are
fitted to live in water find that they are not well adapted to
the land because of the great differences in the two habitats.
In the first place, water animals usually have only a thin skin.
This would not protect the body from loss of water in the air.
Consequently, only the thicker skinned aquatic animals can
become terrestrial. Second, such thick-skinned aquatic
animals must have gills for breathing. These thin-walled
structures cannot exist in dry air. Breathing organs of land
animals must be placed deep in the body so that the air is
moistened by the body before it reaches them. Again the
weight of the body is supported in the water by its buoyancy,
so that the appendages are placed laterally and function as
oars. But on the land the body must be supported by the
appendages on the solid substratum, consequently the appen-
dages are placed below the body. Finally, since all those

825

326 ZOOLOGY

animals that depend upon currents of water to bring them
food have a mode of feeding that is incompatible with living
in the air, they have given rise to no terrestrial species.

The newt well illustrates the changes of form and structure
that an aquatic animal must undergo in adapting itself to the
land. The young newts, as they hatch from the eggs lying in
the water, are thin-skinned animals with delicate, bushy gills
extending out from the
side of the head. The
legs are very small, or
absent, and locomotion
is by a large fin on the
tail. By the move-
ment of this fin the
animal is propelled
through the water very

Fic. 309.— A female newt (Desmognathus much as a fisherman

fuscus) guarding its eggs in a hole by the side geylls a boat. By the
of water. Nat. size. After Wilder.

time the newt has left
the water and has become adjusted to the moist air of the
damp ground on which it lives, the outer layers of its skin
have become somewhat horny and the bushy gills have become
lost (Fig. 309). Respiration now takes place in the throat, or
in other cases in pockets formed from the throat and known
as the lungs. Four legs directed downward support the body
above the ground, and the tail-fin withers away, so that only a
rounded tail remains.

The transformation that the individual newt undergoes in
its lifetime is an epitome of the evolution of many terrestrial
forms. Thus, in the tropics, certain shore crabs have come to
live in the upper part of the beach and eventually in the forests

THE FROG 827

and even on the trees. Their gills have withered away, and the
gill cavities now function as lungs. The hard shell, which
served as a coat of mail to ward off attacks of enemies in the
sea, serves the land crabs to prevent the loss of water. Again,
the ancestors of the wood-lice are common in streams, and even
in this situation are already provided over the whole body
with a thick skin called the cuticula. The possession of this
cuticula has permitted the development of land life in this
group. The gills, which are thin-walled plates in the aquatic
forms, become hollowed out to form lungs. In the case of
snails the thick skin, which is useful in secreting the shell of the
aquatic forms, has permitted some of its possessors to live on
land. Certain representatives of the group, namely, the slugs,
have lost the shell without suffering any disadvantage, because
they have a very thick skin. Even with the thick skin, how-
ever, slugs do not risk a very dry situation, and if forced to
remain long in dry air they varnish themselves over with a
water-tight layer of mucus. In the slugs, as we have already
seen, the gill-chamber has been transformed into a lung-cham-
ber by the degeneration of the gills and the diminution of the
gill-opening so that the influx of air may be reduced or in-
creased as it is dry or moist.

Why have any aquatic organisms given rise to terrestrial
descendants, in spite of the fact that there is room in the
sea for all, and food is almost inexhaustible? The probable
answer to this question is that some species whose structure
permitted land life found it advantageous to leave the water
from time to time to escape from enemies. In the new field
they obtained an abundance of oxygen and food, so they pro-
longed their stay there until, finally, they became better
adapted to the land than to the sea.

328 ZOOLOGY

The first animals to come to the land were probably the
earthworms, many of whose aquatic allies live in ponds that
are apt to dry up during the summer. The aquatic worms are
preserved from annihilation only by burying themselves in
the muddy, damp bottom. One of the next groups to give
rise to terrestrial forms was that of the Arthropods, some of the
representatives of which still retain in their bodies evidences
of their aquatic ancestry. Thus in the terrestrial Peripatus

Cn a

eal HHS AAR AND
hains't..

3
Tw
: pas

Fie. 310.— Peripatus, the air-breathing wormlike animal that bridges the

gap between Myriapods and worms.
(Fig. 310) the air-breathing organs have not yet developed, and
the appendages are placed laterally instead of ventrally. From
some such primitive form the plant-eating insects arose, and
on account of the almost limitless supply of vegetation devel-
oped mightily. Then came the carnivorous forms, like the
spiders and their allies, to prey on their herbivorous forerun-
ners.

Among the vertebrates the primitive forms lived in the
water, but in the group Amphibia, which includes the newts,
salamanders, frogs, and toads, there are forms that show the
transition from aquatic to terrestrial life. Most of them
begin life as aquatic animals and end it as terrestrial.

The Amphibia comprise about a thousand species which are
distributed in three great groups. Those forms that retain
their tails permanently, even when they come to land, are
known as Urode'la. They are confined in their distribution
to the Northern Hemisphere, excepting two or three species

THE FROG 829

that extend their range along the Andes south of the Equator.
North America is especially rich both in species and individ-
uals of Urodela. Those which lose the tail in the adult stage,
like the frogs, are called the Anu'ra. These are found in all
parts of the world, especially in South America and Australia.
A third group (Gym'nophiona), which is found only in the tropics,
contains animals that have a worm-like body, live in the ground,
and have more or less rudimentary eyes. It will be seen that
the Amphibia are found chiefly in tropical and subtropical
countries, although a large number thrive in colder parts of the
temperate zone.

As an example to illustrate the structure of Amphibia we
may take the frog.

General Form of the Body. — The frog is not a typical am-
phibian, since it has lost its tail, so that only head and trunk re-
main, and the anal opening lies at the very hind end of the
body. The appendages have become long and slender as
compared with those of the fish, and five distinct toes are
present on each foot. The whole body is covered with a
delicate skin devoid of scales such as fishes have, or other
outgrowths ,and coverings of the skin such as are found in
birds and mammals. The skin contains abundant glands,
however, the secretions of which may be poured over the
skin to protect it from drying up.

The Skeleton of the frog consists of an axial and an appen-
dicular part (Fig. 311). The vertebral column consists of a few
simple vertebree, to each of which a pair of short ribs is fused.
The skeleton of the rudimentary tail is represented by a long,
bony rod.!. The skull is simple as compared with that of the
fish, partly because of the absence of gills and partly because

1 Urostyle, UST., Fig. 311.

AST

Fig. 311. — The skeleton of the frog (Rana temporaria). A. Skeleton seen from above.
The left half of the shoulder girdle and the left fore and hind legs are removed,
also the membrane bones on the left side of the skull. Cartilagenous parts are
dotted. Names of bones that are first formed in cartilage are in GOTHIC capitals,
those formed directly in the skin are in ITALIC capitals. a.c.hy, anterior horn
of hyoid bone; acth, depression to receive femur (fe.); AST, ‘‘astragalus’’; b.hy,

base of hyoid; Cc, ‘‘calcan,’” bone of a spur; CAL, ‘‘calcaneum”’ of the ankle;

THE FROG 331

of areduction and fusion of parts. The teeth, instead of being
scattered over the mouth, are found chiefly on the jaws, but
there are also a few small patches of
teeth on the roof of the mouth.

The shoulder girdle forms a complete
ring extending from the shoulder blade
(S.SCP), which lies on the ribs, to the
breastbone below. To this are at-
tached the upper armbones (HU) of
the relatively short fore legs. The lower
arm is supported by a united radius and
ulna. The pelvic girdle is so long as to
give great elasticity to the attachment
of the skeleton of the long and powerful
hind legs, which are used in Jumping
(FE and TI. Fl).

Organs of Nutrition.— The food of

frogs is very varied, consisting of
Fig. 312. — Three stages

(from above downward)
tadpoles, etc. These are caught in the | in the movement of the
tongue of a frog in catch-
ing an insect. From
tongue, which is attached in front and “Cambridge Nat. Hist.”

free behind, so that the hind end may be flopped out some dis-
tance in front of the mouth to strike an insect (Fig. 312).

worms, mollusks, insects, small fishes,

roomy mouth, often with the aid of the

EX.OC, exoccipital, connecting with vertebral column; FE, femur; fon,
openings in skull; FR.PA, fronto-parietal; HU, humerus; IL, ileum;
MX, maxilla; olf.cp, olfactory capsule; ot.pr, otic process; p.c.hy, pos-
terior horn of hyoid; PIZX, premaxilla; PR.OT, pro-otic bone (ear) ;
RAUL, radio-ulna; SP.ETH, sphenethmoid; SQ, squamosal; S.SCP,
suprascapula; sus, bone suspending lower jaw from skull; TI.FI, tibio-
fibula; ¢r.pr, transverse process; UST, urostyle. v.1, cervical verte-
bra; V.9, sacrol vertebra; VO, vomer; I-V, digits. B. The fourth verte-
bra, anterior face; a.zyg, anterior linking process; cn, centrum; Im,
lamina; n.sp, neural spine; pd, pedicel; tr.pr, transverse process. After
Howes, from Parker and Haswell.

332 ZOOLOGY

Beyond the mouth a short gullet leads to the large stomach.
Next, the food passes into the upper digestive portion of the

Geel ts °
rreaPel gl ens ed Clag hg 5.3) ST" ch BL
oUt ork ford mae elys| sped PEE helluse Pur Tu

eux — ey oe : = \

®

eck Ses =

etal

Fig. 313. — Diagram of viscera of a male frog, Rana temporaria, seen from the left
side. SKELETAL System: Skull: FR.PA, fronto-parictal ‘of cranium; PILX,
premaxilla; SPH.ETH, sphenethmoid; M.MCK, cartilage base of lower jaw;
b.hy, tongue-bone (hyoid) ; ve.t, teeth on vomer bone. Vertebral Column: en.5,
centrum of third vertebra; n.a.1, neural arch of first vertebra; UST, urostyle.
Girdles and Appendages: ep.cor, epicoracoid; IL, ileum; IS, ischium; 0.ST,
omo- and epi-sternum; pu, pubis. ALIMENTARY SysTeEM: tng, tonguc; eus.t,
Eustachian tube (remnant of gill-slit); g/, glottis; gud, gullet; st, stomach; du,
duodenum; Jr, liver; b.d, bile duct; pn, pancreas; s.int, small intestine; ret,
rectum; cl, cloaca; an, anus. CIRCULATORY SYSTEM: c.art, conus arteriosus;
lau, left auricle; ped, pericardium; s.v, sinus venosus; v, ventricle; cp.ad,
fat body; d.ly.s, dorsal lymph sinus; spl, spleen; v.ly.s, ventral lymph sinus.
RESPIRATORY System: /./ng, left lung; r.dmg, right lung; p.na, posterior ‘nares.
UroGENITAL System: kd, kidney; wr, ureter opening into the cloaca, cl, at
ur’; bl, urinary bladder opening at bl’ into the cloaca; ts, testis; vs.sem, semins]
vesicle. NErvowus System: crb.h, cerebral hemisphere ; cblm, cerebellum ; sp.c
spinal cord; olf, olfactory lobe of brain; opt./, optic lobe of brain. From Park i
and Haswell.

intestine, known as the duodenum, where the secretions of the
liver and the pancreas are poured (Fig. 313). This is followed
by a long, absorbing portion, and this, in turn, by the rectum,
which receives also the excretory and reproductive products,
and consequently functions as a “ cloaca.”

THE FROG 333

Organs of Respiration. — Although the young frog (tadpole)
uses gills for absorbing the oxygen dissolved in water, the adult
breathes also air. Even the adult doubtless absorbs the
oxygen of the water through the thin skin, and perhaps also
through the lining of the pharynx; but the main organ of
respiration is the pair of lungs (ring and ling). The lungs
are sacs whose inner surface is divided by partitions into air-
cells which greatly increase the respiratory surface. Through
the thin walls of the air-cells there flows a constant stream of
blood, gaining oxygen from the air in the lungs.

Organs of Circulation.— The impure blood from the body
collects in a single vessel, and then enters a chamber of the
heart called the right auricle. Thence it passes through an
opening, guarded by valves, to a chamber that has thick mus-
cular walls, and is called the ventricle. When the ventricle
contracts, the blood is prevented by the valves from returning
to the auricles, and passes out of the ventricle into a great
arterial trunk, or “conus” (Fig. 314). Alongside of the
right auricle, but completely separated from it by a par-
tition, is the left auricle. This contains richly oxygenated
blood freshly received from the lungs. The left auricle con-
tracts at the same time with the right, and pours its blood into
the same ventricle. It would seem inevitable that the pure
and impure blood should completely mingle, but this is pre-
vented by the prompt contraction of the ventricle, assisted by
a rather complicated mechanism. The conus lies on the right
side of the ventricle, so that it is nearer to the stream of impure
blood emerging from the right auricle, and is first filled by it.
The first outlets from the conus that this impure blood meets
are the arteries that go to the lungs, and so, with the assistance
of certain valves in the conus, the impure blood flows to the
lungs. As the ventricle continues to empty itself, a mixed

3384 ZOOLOGY

blood emerges, and, slipping over the entrance to the now filled
pulmonary arteries, goes on to the dorsal aorta and the organs

Fic. 314. — The heart of the frog with the cavities laid open. Blood
enters from the venous sinus into the right auricle, r.au, at s.au.ap. The
right auricle is completely separated from the left (daw) by a partition
(spt.aur). Both auricles open by the same aperture, guarded by two
valves (au.v.v) into the ventricle, xf. The left auricle receives the pul-
monary veins at pul.v. The exit of blood from the ventricle is guarded
by valves at v, and its further path directed by a valve at lv, into the
right and left pulmonary arteries, pul.cu.fr, and c,c,c', into the arteries
going to the general trunk, syst.dr and b, 6’, and into the arteries going
to the head, carr, with its carotid artery (car.a) and so-called gland
(car.gl) ; and with its tongue branch (/g.a).

of the trunk ; finally the purest blood, which is the last to leave
the ventricle, passes on to the last pair of vessels, which go to
the brain, where it is most needed. The fact that the trunk

THE FROG DDO

receives mixed blood results first in a relatively low body tem-
perature and, second, in slow chemical changes in the body —
a sluggish life.

Organs of Excretion and Reproduction. — The two kidneys
(Fig. 313, kd) lie in the dorsal part of the body cavity. They

Fie. 315.— Aurode, Salamandra maculosa, of Europe, showing exter-
nal ringed condition of the body. After Cuvier.

consist of a mass of tubules closely intertwined with
blood-vessels that yield their waste products to the
tubules from which they pass by the ureters to the
cloaca.

The male germ glands (ts) lie at the anterior end
of the kidneys and their products pass through cer-
tain tubules of the kidney and so, by way of the

urcters, to the cloaca. Thus certain of the excretory tubules
serve in the frog, as in annelids, to carry the germ cells to the
exterior.

The ovaries of the frog are large sacs covering the kidneys.
The ripe eggs fall from the ovary into the body cavity, are
picked up by the oviducts which open into the body cavity,

336 ZOOLOGY

and are carried through them to the cloaca, receiving on
their journey the jelly, which swells up enormously when the
eges enter the water at the time they are laid and while the
sperm is making its way to the eggs.

A i

+

cerebellum Typ

v7?

i —medulla NIE A

"a

Re
Nee

Fie. 316. — The brain of the frog viewed from above (A) and below (B).
I, olfactory nerve going to olfactory lobe (ol. lobe). II, optic nerve going to
Tropt, the optic tract of the brain. J11, 1V,; Vi, 1X, X, XI, XIT @),
other nerves to brain. Z.H, mid brain; Jnf, infundibulum. Med, the
medulla with its first nerve at 7. From Wiedersheim, ‘‘Comp. Anat.”

The muscular system of the frog is reduced on account of its
shortened body. In the tailed amphibians the ringed condi-
tion of the body musculature is still evident (Fig. 315), but
in the frog this appears only in the straight abdominal muscles.

'

“AJOINOG [VoIBOOoT “XN yoday oy} Wor ‘wnuenbe ue ur Suray ‘uasg ‘Joo-pnu sy, — ‘ZTE “ol

1D

338 ZOOLOGY

©

The muscles of the breast and appendages offer special com-
plications.
The nervous system shows an advance over that of fishes.

The brain has two large lobes in front (olfactory lobes,
ol.lobe), but the front part of the brain proper (cerebrum) and

Fic. 318.— Mud-puppy (Necturus), photographed while living in an aqua-
rium. From Report N. Y. Zoological Society.

the cerebellum are poorly developed. The spinal cord is
shortened and modified on account of the shortening of the
trunk.

Sense-organs. — The sense of smell is chiefly located in the
nasal sacs, which open anteriorly to the exterior and posteriorly
into the mouth. The eye is essentially like that of other verte-
brates. The ear also consists of a central chamber and three
semicircular canals. There is a large external membrane, and

THE FROG 339

its vibrations are conveyed to the inner ear by a single rod
instead of the flexible chain present in man.

Families of Urodela.— Of the American Urodela,! the
mud-eel, or Siren, of the Southern States has external
gills and persistent gill-slits. This species becomes sixty
centimetres long and snake-like, has lost its hind legs, and
is of a dark lead color (Fig. 317). It is needlessly feared by
the negro rice cultivators, who slaughter it in great numbers.

Fie. 318 a.— Typhlomolge, a blind, necturus-like salamander from the
caves of Texas. Photo. from life. After W. W. Norman, from ‘The
American Naturalist.’’

The mud-puppy (Necturus), frequently known also as water-
dog, is found from the Hudson River to the Mississippi Valley,
and is very abundant in the Great Lakes. Its external gills
are very large, and red with the blood flowing in them. It
feeds on small water animals. In April or May it lays eggs
about the size of a pea. A curiously modified form of Nec-
turus occurs in caves of North America (Fig: 318). An-
other member of this family is the cave ‘
Austria.

‘olm” of western

The Congo snake (Amphiumide) is found in the Carolinas
and Gulf States. This black, snake-like urodele is about a
metre long, and lives in bayous and muddy ditches (Fig. 319).
It has the entirely undeserved reputation of being injurious.

1 oura, tail; delos, conspicuous.

340 ZOOLOGY

The hellbender (Cryptobranchidz ) inhabits the Ohio Valley
and the South.? It loses its gills before it becomes adult and
the gills-slits close. It is a very voracious scavenger of the
water, bites the hook fiercely, and is noted for its great te-
nacity of life under unfavorable conditions. The only other

Fic. 319. — The ‘Congo snake’? (Amphiuma means). From the Report
N. Y. Zoological Society.

living representative of this family is the Japanese giant sala-

mander, which becomes three metres long.

The salamanders (Amblystomidee *) include some twenty-five
species belonging to five genera, four of which occur in north-
ern and eastern Asia, and the fifth, Amblystoma, is confined
to the United States and Mexico, except for one species that
occurs in Siam. In this family the external gills are absorbed

1 kryptos, hidden ; branchion, gill. 2 Fig. 320.
3 From amblys, blunt ; stoma, mouth.

TUE FROG 341

in early life. The common species of New England and the
Central States is known as the Spotted Salamander. It is

Fic. 320. — Cryptobranchus, the ‘“‘hellbender.’”’ Reduced. From ‘‘Standard
Natural History.”

about 15 centimetres long, and black, with a series of yellow
spots on each side of the back. It lays eggs in springs or ponds
during April; the dark gray eggs are contained in great masses
of jelly which are attached to sticks at or near the surface of the

Fic. 321. — The larva of Amblystoma tigrinum. the Axolotl stage of the
tiger salamander. From Mivart.

342, ZOOLOGY

¢

water. The larve of the more southern species often reach
a size considerably larger than the adult, and breed before the
gills are absorbed. In a Mexican species the larval state is
never passed. The larva of Amblystoma (Fig. 321) was for-
merly described, indeed, as a distinct species under the name
of Axolotl.

Fic. 322. — The red-backed salamander (Plethodon) : A, dorsal view ;
B, lateral view. Nat. size. From hfe.

The newts! (Plethodontide ? and Desmognathide *) include
a number of small Urodeles, having a close general resem-
blance and similar habits.

Plethodon, of the eastern United States, is lead-colored above,
very often with a broad, red dorsal band (Fig. 322). It is found
under logs, and is very active. Spelerpes is lemon-yellow and
white below, and Desmognathus is brown above, with gray or

1 Newts may be captured by sweeping with a net the muddy bottoms of
small, spring-fed pools. They can be kept for months in an aquarium, where
they should be fed thrice a week with earthworms or freshly chopped beef.

2 plethos, abundance ; odontos, tooth.
3 desmos, bond; gnathos, jaw.

THE FROG 343

purplish spots on the sides. Both Spelerpes and Desmognathus
live in and about running brooks, under stones and fallen logs.
Their eggs are attached to the under surface of submerged stones.
The adults are easy to keep in confinement in a moist fernery.
They may be obtained out of doors all the year round, excepting
during the time of deep snow.

Metamorphosis. — As we have seen, all Amphibia have gills
while young, but some lose them before maturity while others
retain them permanently. Those species which retain the
gills pass their whole life in water; the others may live on the
land. The loss of gills is associated with the assumption
of a land life. In the Amblystoma we have species which are
curiously intermediate between the two classes in that they
may retain their gills, tail-fins, and other structures adapted
to aquatic life,! even to the time of reproduction ; or they may
lose their gills and tail-fins. The first result follows if they are
prevented from coming on land; the second, if they are
forced to leave the water. The capacity of the Mexican
Axolotl for either becoming an adult or remaining a larva was
first shown by some experiments of the German naturalist
Weismann and a pupil of his. It will be seen that, when forced
to live in the water, Axolotl retains permanently a larval con-
dition ; and one would never know that in this larval condition
the animal is not adult were it not for the accident of its some-
times becoming adult. It is quite possible that all of the
Urodela which retain their gills throughout life may formerly
have had a gill-less adult stage which is now lost.

Early Development of Urodela. — The eggs of Urodela are
deposited in a gelatinous mass in water, and are attached to
submerged plants, or to other objects in the water, either singly

1Compare Fig. 321.

344 ZOOLOGY

or in masses, according to the species. The eggs contain
much yolk; consequently the cleavage is partial, and the em-
bryo seems to develop on a small part only of the yolk, and for

Fic. 8. Fic. 9. Fic. 13, Fic. ry. Tic. 15.
Fic. 323. — Developmental stages of Spelerpes bilineatus. Figs. 1-5, neural
groove beginning to form; Figs. 6, 7, neural groove closed; Figs. 8, 9,
head beginning to form; Figs. 10-12, tail formed, yolk absorbing; Fig. 13,
embryo capable of moving in egg membrane; Fig. 74, embryo just able
toswim; Fig. 15, three days after hatching. The letters indicate the suc-
cessive stages. After H. H. Wilder, from ‘‘The American Naturalist.”

some time after hatching the yolk mass hangs as a lump on the
under side of the embryo. Very early a deep groove, bounded
by a pair of folds, arises on the edge. This groove is large in

THE FROG 345

front (Fig. 323 6). It forms the beginning of the brain and
spinal cord. The feathery gills and the beginnings of the ap-
pendages next sprout out, while the trunk continues to elon-
gate and assume the form of a young salamander (Fig. 323 h).

Fie. 324. — Pipa americana. Female with young in pits on its back.

Families of Anura. — Of the Anura there are eight or ten
times as many species as there are of the Urodela. They are
distributed into nearly a score of families. Of these a few of
the more interesting deserve to be mentioned.

The South American Pipa (Pipide) is noteworthy because
of the habit which the female has of brooding its young in
pits of the skin on its back (Figs. 324, 325).

348 ZOOLOGY

in two long, parallel strings of albumen, which lie coiled at the
bottoms of ponds, hatch out in May, and metamorphose about
a month later.

The frogs (Ranidie) are almost confined to the Northern
Hemisphere and the East Indies. In the northern United

Fie. 328. — Green frog, Rana clamitans. Nat. size. Photo. of living animal
by W. FoeCeP.
States there are some eight species, of which the com-
monest are: the leopard-frog, of green color, with irregular
black blotches edged with whitish; the pickerel-frog, light
brown, with two rows of oblong square brown blotches on the
back ; the wood-frog, living in damp woods, pale reddish brown
with a brown band on the side of the head; the green frog, of
uniform bright green to brown color, with numerous small
dark spots, and with glandular folds (Fg. 328) ; and the bull-
frog, of great size, green, with small, faint spots on the

back.

CHAPTER XXIV
THE LIZARD: A STUDY OF DRYNESS LOVERS

IN spreading over the land, animals have come into situations
where rain falls only for a small part of the year. In such
places not only is the ground usually dry, but vegetation is
sparse. Nevertheless, certain animals have come permanently
to occupy even such desert situations, and, indeed, entire
genera or families prefer desert habitats. They are the lovers
of dryness. The animals most common in our own deserts
are certain hard-shelled, black beetles, lizards of many kinds,!
the little sphermophiles, looking like slender chipmunks, with
now and then a rattlesnake. All of these animals and many
others that live and feed on the ground burrow into the soil.
There they remain during the heat of the day, coming forth
at night to feed and seek their mates. These desert animals
must go for weeks or even months without drinking water,
such moisture as they can get being obtained from roots
and green parts of succulent cacti. Almost always the skin of
such animals is hard, preventing the loss of internal waters by
evaporation. Indeed the whole body of these animals seems
to be very dry, and they need only aslight amount of water to
live. Even in ordinarily moist climates there is a great deal
of difference between animals in respect to their need and love
of moisture. While many land animals are found in moist
woods and under damp logs, or by the edges of lakes and

1 Fig. 329.
349

300 ZOOLOGY

swamps, others frequent dry country roads, sandy beaches,
and the driest hilltops. Certain land-snails live by preference
in sandy places and even in deserts. The tiger-beetles and
some flies are characteristic of dry situations. One or two
species of sowbugs are capable of living away from mois-
ture, although their ancestors so recently left the water. Cer-

Fie. 329. — Home of lizards (scene in the Nevada desert). They rest on
the stones, dart lke streaks of light across the desert floor and into the
‘bunch grass.”

tain birds shun the marshy places which their allies prefer.
Field plovers and the Eskimo curlew belong to the water-
fowl, but they live in the dry uplands. Animals that thus
inhabit dry situations are there by preference because of their
nature. They would find life in marshes not only distasteful,
but probably incompatible with existence.

The reptiles, which are on the whole best represented in the

THE LIZARD 351

desert, are vertebrates in whose skin horny or bony patches
are formed. They constantly breathe by means of lungs, and
lay large eggs provided with a tough, leathery, or calcareous

Se
y Snr
SON
RSQ

Fie. 330. — Skeleton of a turtle (Cistudo, of Europe), seen from below, the
plastron having been removed and placed at one side. C, rib-plate;
Co, corocoid, a part of the shoulder girdle; F, fibula; Fe, femur;
A, humerus; Jl, ihum; Js, ischium; Pu, pubis; Pro, pro-coracoid ;
R, radius; Sc, scapula; 7, tibia; U, ulna; e, ‘‘entoplastron ’’ or inner
plate of plastron; Hp, epiplastron or upper plate; M, marginal plates;
Nu, nuchal plate; Py, pygal plates. From Zittel.

shell. There are about thirty-five hundred species of living rep-
tiles, which are grouped into four principal orders as follows : —

(1) Turtles, or Chelonia, (2) Lizards, or Sauria, (3) Serpents,
or Ophidia, (4) Alligators, or Crocodilina.

302 ZOOLOGY

Asan example of the structure of a reptile, we may consider
the anatomy of the turtle.

General form of body.— The turtle is depressed and
rounded, and the trunk carries an upper and a lower plate,
affording protection to the entire body.

Skeleton. — The vertebrz are few, in correspondence with
the shortened body, and are immovable upon each other (Fig.
330). The spines of the vertebre are flattened out to form
the median row of bony
plates, and the ribs are
flattened to form the
“costal” plates. These,
with certain plates at
the margin, form the
“earapace” of the
turtle. The bony cara-

Fic. 331.— Skull of a turtle (Chelone) viewed , :
from the left side. The bones shown are Dace 1s covered by horny
named from in front backward: Mav, max- plates which are derived
illary; F, frontal; J, jugal; Pdf, post- D
frontal; Qj, quadrato-jugal; Q, quadrate ; from the skin, and only
Sq, squamosal; Par, parietal; S.o, supra-

tr. par oughly agree with th
occipital. From ‘Cambridge Nat. Hist.” roughly Agree with the

bony plates lying below
them. The breast-bone and ventral ribs are replaced by
the “plastron,”” which is made up of four paired and one
median plate. The skull is massive, and the bones of the side
of the head form a broad arch, enveloping and protecting, but
separated by a space from, the brain-case proper (Fig. 331).
The shoulder and pelvic girdles are fused with the shell, but
the skeleton of the appendages is typical, though often show-
ing special adaptations for swimming.
The organs of nutrition. — The food of turtles is extremely
varied, according to their habitats. Land tortoises eat toad-

THE LIZARD 393

stools, fruits, and other vegetable matter. Water turtles eat
worms, insects, frogs, and fishes. Some sea-turtles, like our
green turtle, eat various alg; others, like the tortoise-shell
turtle, are carnivorous, living on fish and mollusks. The jaws
are toothless, but are provided with a sharp cutting edge. The
stomach and intestines are
simple. The cloaca is large.
Organs of circulation.— The
general features of the circula-
tion are similar to those for
birds described in the next
chapter. But the heart, while
showing an advance over am-

shee x : Fia. 332. — Diagram of the heart of a
phibians, is far from showing turtle. Systemic blood from the

the perfection of development "#ht auricle (R.A), passes by the
; i course, x, through the opening at y
found in birds and mammals. __ in the incomplete septum, a, into the
chamber, Cp; thence, on contraction
of the ventricle to the pulmonary
received hy the right auricle artery (P.A) by the pathz. Blood
from the lungs passes from the left
auricle (L.A) through the passage w
The ventricle is incompletely (guarded hy the valve, v), into the
ee : : : larger chamber of the ventricle. On
divided into a right and a left — contraction, the opening y being
soe os ie ‘ automatically closed, the blood goes
chamber by i perfor ated Date by s and? to the left and right
tition (Tig. 332, a). When the aortas, respectively, and so on to
the body. After Huxley.

Venous blood from the body is

and poured into the ventricle.

auricles contract, the blood
from the right auricle passes to the right side of the
ventricle, called the pulmonary space (Cp), and the blood
from the left auricle (pure and bright because having just come
from the lungs) fills the rest of the ventricle. When the ven-
tricle contracts, the imperfect partition (a), cutting off the
pulmonary space, becomes drawn tight across the ventricle.

The blood in the pulmonary space goes to the lungs to become
2a

354 ZOOLOGY

purified, and the pure blood in the ventricle, mingled with
some venous blood, goes to the aortas (RAo, LAo), and so
on to the trunk and head. Thus, in the turtles, the body
receives a little impure blood, and this fact results in keeping
down the temperature of the body.

The organs of respiration are a pair of large lungs. These
show a great advance over those of the frog, since they are not
mere sacs, but contain many lobules. As the body is encased in

an inflexible shell, the

£ a lungs cannot be filled by
raising the ribs, as is the
case with us, and so the
turtle seems to depend
ly i largely upon the move-

Fic. 333. — Side view of the brainof aturtle ments of its capacious
(Emys). J, olfactory nerve; IJ, optic
nerve; Lol, lobe of smell; VH, cerebral
hemispheres; MH, optie lobes; Tro, from the lungs. Certain
“optic tract’’; HH, cerebellum; NA, ee:
medulla; R, spinal cord; Inf, ‘infundi- water tortoises have

,

throat to force air into or

bulum ”’ terminating in the ‘‘ hypophysis.’

reat sacs opening from
From Wiedersheim, ‘‘Comp. Anat.” 8 & I 2

the cloaca, whose walls

are filled with blood-vessels, and which may be alternately
filled with and emptied of water through the cloacal opening.
The oxygen of the fresh water is absorbed by the blood-vessels
in the wall of the sac. Thus these sacs are like gill chambers
in some lower animals, and enable the turtles to breathe
even while submerged. However, this device is only a tempo-
rary expedient and cannot long replace respiration by the lungs.
The organs of excretion and reproduction. — The kidneys
are small and round, in marked contrast to those of amphibi-
ans, of which, indeed, they represent only the posterior por-
tion. They are, on the other hand, like the kidneys of the

oo
or
an

THE LIZARD

higher vertebrates. The testes and ovaries lie dorsal, near the
kidneys, and discharge their products by special tubes (not
through the excretory tubules) into the cloaca. The eggs are
provided with a hard egg-shell and, in most pond and river
species, are laid in the spring in sandy soil at a depth of 30 to
80 centimetres.

The muscular system of turtles is (in correspondence with
the round, bone-encased body) much reduced, except in the
neck and appendages, which are capable of varied and extraor-
dinarily rapid movements.

The nervous system shows, at least so far as the brain goes,
a decided advance over amphibians. The lobes of smell are
reduced in size, and the cerebral hemispheres are well devel-
oped (Fig. 333). Also the cerebellum attains a fair size, indi-
cating increasing power of correlated movements.

The sense-organs are well developed. Turtles are very
sensitive to touch, even on the shell. They discriminate
between various sorts of closely related plants, showing a well-
developed sense of taste and smell. The ear shows no great
advance over that of Amphibia. The eye is protected by a
ring of bony plates in the sclerotic coat. In addition to two
eyelids there is a membrane — the nictating membrane — that
can be rapidly drawn across the front of the eyeball; this we
shall see also in birds. It probably serves to cleanse the
front of the eye and perhaps to regulate the amount of
light entering the eye. Although not present in turtles, men-
tion must be here made of a third eye looking out from the
middle of the skull, and called the pineal eye. This eye is
functional in some lizards (Fig. 334). In our own brains there
is arudimentary organ having the same relative position, and
which has long been known as the pineal gland. This organ

356 ZOOLOGY

was once regarded by a philosopher as the seat of the soul,
on the ground that the soul is a unit and that the pineal gland

Fig. 334. — Section of the pineal eye of a lizard (Hatteria): c, cornea;
i, lens; h, cavity of eyeball; r, 7’, retina; z, cells in stalk; st, stalk;
g, blood-vesse After Spencer.

is unpaired. We now know that it is the rudiment of a once
functional eve.

The lizards (Sauria) constitute a large order characteristic
of the tropical and subtropical countries, and reaching the
maximum of its development in South America, while in the

TUE LIZARD 357

northern continents it is relatively poorly represented. Most
lizards have an elongated body, four legs, eyelids, and a breast-
bone or sternum. Lizards are, as a rule, carnivorous, and since
they destroy insects injurious to vegetation they may be
considered as beneficial to man.

Most of our lizards belong to the family Iguan’ide,! a
family that is most abundant in the Western Hemisphere.
They are known by the thick tongue, by a large scale in the

Fig. 335. — Phrynosoma, the horned toad. Photo. by E. R. D.

middle of the head in front of the eyes, and by the fact that all
four legs are well developed. The genus Anolis, known as the
American chameleon, contains eighty tropical species. Our
species lives in pine woods from the latitude of Tennessee
south to the Gulf and the island of Cuba. Its graceful form
and bright colors make it one of the most beautiful of lizards.
It lives on trees, eats insects, is not timid, can live well in con-
finement, and, like the chameleon of Europe, has the power of
changing its colors from bright green to dirty brown. Besides
Anolis, we have various other lizards of the family Iguanide.
The horned toad of the Southwest, which has a broad, flattened

1 Native name.

308 ZOOLOGY

body and long spines on the head, and lives in dry, sandy
places, is a familiar object.t In the South Central and South-
ern States lives the elongated “ swift,” of varying color, often
with black, irregular cross bands above, with iridescent colors
on the throat of the male, and with large, strongly keeled scales

Fic. 336. — Lacerta viridis, the green lizard of Europe. After Brehm.

and aslender tail. The largest of the Iguanide is the “leguan”
of the West Indies and South America, which gains a length
of 1.75 metres, or over five feet.

The family of water-lizards, or Varan’idz,? contains the
largest known lizards. The Nile varanus attains a length of
nearly two metres. It lives in the rivers of Africa, feeds on
small crustaceans, birds, birds’ eggs, frogs, fish, and occasion-

1 Fig. 335. 2 Latinized from the Arabic word waran, lizard.

THE LIZARD 359

ally also on young crocodiles and crocodile eggs. The an-
cient Egyptians regarded these crocodile-like lizards as the
greatest enemies of the crocodile.

The common lizards (Lacertidze!) of middle and southern
Europe are agile, harmless creatures, often of bright colors,
and are commonly and favorably known. The more abun-

Fic. 337. — Heloderma, the Gila monster. About two-fifths nat. size.
From Brehm.

dant are the “ green lizard” (Fig. 336), the “ sand-lizard,”
and the “ wall-lizard ” of the Latin countries.

The Gila monster (Helodermidz) is the largest lizard of
the United States. It inhabits New Mexico, Arizona, and
the country southward. The lizard is colored brown, with
reddish spots and numerous yellowish punctations (Fig. 337).
It is nocturnal in its habits, and its bite is very poisonous,
although rarely fatal to man.

1 From lacerta, lizard.

360 ZOOLOGY

The family of slow-worms includes the famous glass-snake,
or joint-snake, of the South. This snake-like lizard has no
legs, or only rudiments of the hinder pair. It is noted for the
ease with which it breaks in two when struck or lifted by the
tail. This result is due to the fact that, as in certain other
lizards, the vertebre of the tail are unossified along the middle
plane, so that they separate at this point upon the slightest
blow. The muscles of this species seem also to be arranged

Fic. 338. — Chameleo, the chameleon. From Leunis.

so as to facilitate separation. In Europe there is a lizard of
this family, the so-called “blindworm” (having, however,
well-developed eyes), which is found in retired localities, from
which it comes out, especially in the evening, to capture earth-
worms and slugs.

The Chameleon, famed in literature, comes from Africa.
Its change of color depends upon the possession of several
layers of different color in the skin, which can be separately
expanded or contracted as required, in consequence of which
sometimes one, sometimes another, color comes to predomi-
nate. It captures insects, a habit which is facilitated by its
power of protruding the tongue to over half the length of its

THE LIZARD 361

body and bringing the sticky end in contact with its prey.
The protrusions and retractions of the tongue take place with
marvellous rapidity (Fig. 338).

While in point of size the lizards of geologically recent times
are inconsiderable, those of former epochs were huge. These

Fie. 339. — Hadrosaurus. From reconstruction model. Osborn, ‘Rept.
Amer. Mus. Nat. Hist.”
former or fossil lizards were most characteristic of the middle
life era or the Mesozoic age. They belong to three main
groups; namely, swimming, walking or wading,! and flying
lizards. The swimming lizards were sometimes over 10 metres
long, and had feet modified as paddles. The land lizards
were elongated, three-toed, carnivorous reptiles, with hollow
leg bones like birds. In the flying lizards a strong, compact
body was provided with hollow, air-filled bones, and locomo-

1 Fig. 339,

362 ZOOLOGY

tion was effected by a huge membranous expanse stretched
between the elongated posterior finger, the trunk, and the
hind legs. The spread of the wing was about three feet.
The turtles, or Chelo’nia,! form an order distinct from the
lizards. They are characterized by a depressed form, a bony
case, and toothless jaws. Like other reptiles, they are most
abundant in tropical countries, since the high external tem-

Fie. 340. — Hawkbill-turtle. Much reduced. From Brehm.

perature compensates in a way for the insufficiency of the
mechanism for maintaining from the inside a high blood
temperature. Turtles are abundant in Africa, and are much
commoner in North America than in Europe. Three principal
families of Chelonia may be distinguished. A short account of
each follows.

The family of marine turtles includes certain turtles that
live in all oceans, and may acquire a weight of as much as one
thousand pounds. The green turtle, used in making soup,

1 Cheldne, turtle.

THE LIZARD 363

occurs on the Atlantic coast as far north as Long Island.
From the hawkbill turtle (Fig. 340) comes the tortoise-shell
used in certain ornaments. In the “‘leatherback”’ the shields
are incompletely ossified.

The family of soft-shelled turtles includes certain turtles
that live in rivers or ponds of the Mississippi Valley and the
Gulf drainage basin (Fig. 341). They
have a flat, rounded shell, the feet are
broadly webbed, and the neck is long.
Although the ancestors of turtles were
without the hard shell, it seems prob-
able from the whole structure of the
upper and lower plates that the soft-
shelled turtles are not ancestral, but of
recent origin, and have recently lost
the hard shell of their ancestors.

The family of fresh-water and land ft aN
tortoises is known as Testudinide.’ “CAS y by
Our snapping-turtle is distributed Fie. 341.— Trionyx, three-
from Canada to equatorial South aie ae Bla eee
America. It feeds on fish, and lays From Leunis.
from forty to fifty eggs, which it buries at a depth of
about a metre (Fig. 342). The alligator snapper of the Gulf
States attains the length of a metre, and is regarded as
the “most ferocious and, for its size, the strongest of
reptiles.” The box-tortoises occupy the northeastern and
central parts of North America. They are well known by
the fact that the body is short and high, the plastron is pro-
vided with a movable hinge, and the carapace is colored

black and yellow.’
1 From testa, a shell, 2 Fig. 343.

364 ZOOLOGY

Fig. 342. — A snapping-turtle in the act of digging a nest.

Other common tortoises of the eastern United States are the musk-
turtle, told by a strong odor of musk; the painted turtle, of green-
ish black color and with marginal plates marked with bright red;

Fie. 343. — Terrapene carolina, the box-tortoise.

Photo. of living animal
by W. H.C. P,

THE LIZARD 365

the speckled tortoise, black with round orange spots; and the wood
tortoise, with keeled shell, and plates marked with concentric strie.

The order of snakes, or Ophi’dia,! is characterized by the
elongated body without appendages, and by the absence of
eyelids and sternum. Like other reptiles, the snakes are chiefly
tropical, but inhabit also the temperate zones. They feed
on living animals. Hidden in the muscles of certain kinds of

Fic. 344. — Euteenia, garter-snake, dorsal view. Photo. by E. R. D.

snakes, rudimentary appendages are found, so we may conclude
that the ancestors of the snakes had legs. It is because snakes
are without legs that they travel so well through thickly
matted vegetation.

The family Colubride? includes the great majority of our
common non-venomous snakes, such as the garter-snake,}
water snake, black snake, milk snake, and spreading adder.
Allied are the boas of South America and the pythons of India,
which attain a length of six metres ormore. Not being poison-

1 ophis, serpent. 2 colubra, serpent. 3 Fig. 344,

366 ZOOLOGY

ous, their bite is not dangerous, but they attack large birds and
even medium-sized mammals, and crush them to death in the
folds of their body.

The family Elapide includes the large, venomous serpents
of the East, the cobra of the East Indies, and the asp of the

Fie. 345. — Elaps corallina, a harlequin snake of South America allied to
the bead-snake of the South. From ‘‘Standard Natural History,” after
Brehm.

Egyptians. The bite of these serpents is quickly fatal to man.
To this family belongs also the bead-snake of our Southern
States, which is, however, harmless (Fig. 345).

The Crotalide' include the rattlesnakes, characteristic of
America? Of this family the most dangerous is the water
moccasin, or black moccasin, which inhabits the Southern

1 krotalon, clapper. 2 Figs. 346, 347.

THE LIZARD oO

[et no oy ae
“ie tn a

Fic. 346. — Crotalus, the rattlesnake. Photographed as the snake was
about to strike. Taken in Wyoming and kindly lent by H. W. Menke.

Fig. 347. — The rattlesnake. The recoil after striking. Photographed in
Wyoming and kindly lent by H. W. Menke.

Note in both figures the elevated rattle, toward the right.

368 ZOOLOGY

States, and gives no warning noise as does the rattlesnake.
The copperhead of the eastern half of the United States is also
dangerous, but is mostly confined to wooded, mountainous
regions. The rattlesnake was once common over the whole

Fic. 348. — Florida crocodile. (Courtesy of the New York Zoological
Park.)

of the Northern States as far west as the Rocky Mountains,
but it is now nearly exterminated in well-settled districts.
Related to these are the venomous vipers of Europe.

The order of crocodiles, or Crocodilina, contains only
some twenty living species, distributed in three genera.
The gavial is the crocodile of the Ganges River. It captures
even large mammals and man. The crocodile in the strict
sense is found in the Nile and other African rivers, in certain

THE LIZARD 369

countries on the western border of the Pacific, and in north-
ern South America, Central America, and the Antilles. Of the
alligators, which have a different arrangement of the dentition
from the crocodiles, there are seven slightly differing species,
all of which are South American, excepting a Chinese species
and the alligator of our Southern States. The latter feeds on
fish, and attacks larger animals (Fig. 348).

CHAPTER XXV

THE ENGLISH SPARROW: A STUDY OF BIRDS AND
MIGRATIONS

Most animals, unlike most plants, are free to travel about in
search of food and mates. Thus every morning in winter the
crows can be seen flying from their rookery in the forest to
distant fields where some grain still remains. At low tide
along the seashore many of them come to pick up clams. At
night they all fly back again to their rookery. When a family
has been raised, the young move away from their birthplace
to seek feeding-grounds, mates, and homes of their own.
Usually this dispersal is so gradual that it is not observed;
but in certain mammals the young of a season may swarm
from their native home and traverse the country like an army.
This is the case with the widely known lemmings of Scandi-
navia. The importance of their march has been much exag-
gerated, for the migration has been noticed only a few times.
The numbers involved in these migrations, however, were
great. The lemmings travelled far; some did not stop even
when they reached the sea, but plunged into it and were
drowned. Their behavior well illustrates the blindness of the
impulse that drives them from home.

Even man migrates when his native country becomes over-
crowded and there are attractive prospects in other lands.
History records the migrations in ancient times of men from
central Asia into Europe, and one may witness any day at the

370

THE ENGLISH SPARROW 371

port of New York the incoming of hundreds of immigrants
allured by the prospects of freedom from military service,
excessive taxation, and oppression in various forms. To-day,
with improved facilities for travelling across continents and
oceans, the human tide moves back and forth more freely than
ever before.

In temperate climates the change of seasons leads certain
animals to migrate towards the equator during the winter and
to return towards the poles in summer. It has been suggested
that the animals were first driven southward by the glacier, a
vast ice-cap that reached in North America from the pole south-
ward to a line extending from New York City to southern Ohio,
thence to near Chicago and on, southwestward, over the Great
Plains to the Rocky Mountain region. When the glacier re-
treated northward again, the animals that had been forced
south made their way back to the homes of their ancestors.
But many of them returned to the south again on the ap-
proach of each winter’s cold. For example, the Bison, which
formerly lived in countless thousands on the Great Plains,
migrated south with the sun, and thus kept in verdant pas-
tures, and similarly to-day scores of species of birds migrate
in the spring and autumn.

The Migration of Birds.— In respect to their migratory
habits all birds are divided into four classes. The examples
that follow are all taken from the latitude of New York City
and Chicago.

1. Residents. These do not migrate, or migrate so short a
distance that those individuals that nest in the northern part
of the range do not move below the southern limit of the
summer range of the species. Examples: the blue jay and
song sparrow.

0

wl

r

T2 ZOOLOGY

2. Winter residents. This class includes those species that
summer to the north and winter only less far north. Exam-
ples: white-throated sparrow and junco or snowbird.

3. Summer residents of any place comprise those species
that nest at the place and winter southward. Examples:
song-thrush, bobolink.

4. Transients. These are species that pause at a place only
while passing from their nesting-place in the North to their
winter home in the South, or which tarry a few days on their
northward journey. Examples: great blue heron, fox-
sparrow, black-poll warbler.

Migration Routes. — The nesting area of any of the migra-
tory species has the form of a band extending east and west a
certain distance along the continent. From this zone during the
fall migrating period the birds move southward along the
meridians, and as they do so the lines of migration gradually
converge, corresponding to the narrowing of the continent.
Consequently, there is a crowding along certain lines, such as
the seashore and river-courses. Thus the birds that follow
down the streams of the Middle West become concentrated into
a narrow migration route when they all reach the lowlands of
the Mississippi River. Some species pass south of the southern
boundary of the United States, and a number even reach the
mainland of South America. Thus the redstart, one of the
commonest of our “ wood-warblers,” reaches Colombia,
Venezuela, British Guiana, and Ecuador. In passing from
southeastern United States to South America, birds take
various routes. Some go by the Antilles, and others fly
across the Gulf of Mexico to Yueatan. The Antillan
route has two main paths, one by the Bahamas and one
by Cuba.

THE ENGLISH SPARROW 373

To get a conerete idea of the migration of a particular species let
us consider in detail the movements of the redstart. This species
breeds from the Gulf of St. Lawrence to British Columbia. Its north-
ern limit in the summer is northern Canada, its southern is North
Carolina. It winters in the Greater and Lesser Antilles and along the
northern shore of South America. About March 20 the redstarts
reach southern Florida, having come from Cuba. The van of the
migrating hosts arrive, on the average, successively at, Raleigh, North
Carolina, April 10; Washington, District of Columbia, April 23; New
York City, May 4; and Montreal, May 16. They move westward
from Florida as well as north. They reach St. Louis, April 17;
Chicago, May 8; Manitoba, May 14, and Athabasca, May 23.
Kansas City is reached about May 5, and British Columbia early
in June. By the middle of August the Canadian birds begin to
migrate southward, the last bemg seen at Athabasca, August 14;
Manitoba, September 20; Chicago, October 5; New Orleans, Octo-
ber 27, and southern Florida, November 4. Every year this broad
red veil of bird life floats slowly northward, in April and May, and is
drawn back to the tropics in September and October. Other species
of birds move similarly, but with great variation in speed and distri-
bution in their summer range.

The peculiar charm of the study of bird migration is due to
the fact that the return of the birds after a long winter heralds
the coming of spring. We hail with delight the return of the
blackbird and robin. The successive weeks show a constantly
increasing number of new arrivals. At the latitude of New
York and Chicago the pheehe, field-sparrow, chipping-sparrow,
barn-swallow, chimney-swift, cat-bird, wood-thrush, hum-
ming-bird, king-bird, orioles, and wood-warblers follow in quick
succession. The height of the spring migration period is
reached in the early part of May.

Of the species that do not migrate there is no better example

374 ZOOLOGY

than the English sparrow, which is common in all our large
cities and in many farming districts. The term ‘ English ”
sparrow is somewhat of a misnomer, for at the time it was
introduced into our country this bird ranged over all Europe,
where it is known as the house-sparrow. The history of the
spread of this bird shows us in a vivid way what are the suc-
cessful qualities among birds. Originally this sparrow was
confined to middle Europe, and probably made its way into
Germany at the time of the Romans. It has since swept all
over Europe, including the British Isles, and has penetrated
even into Siberia. It has crossed the Mediterranean and is
found along the Senegal River, and, probably through human
agency, has penetrated to the Cape of Good Hope. It has
been transplanted voluntarily by man to North America, Aus-
tralia, and Java. It seems to occupy among birds the place
taken among mammals by the rats. Crafty, pugnacious,
obtrusive, thieving, dirty, it has become a nuisance wherever
it has penetrated. But just these pushing qualities, com-
bined with small size, great hardiness, a universal diet, and
immense fecundity, have enabled it to make its way against
all competitors. Its introduction into America can only
be regarded as a deplorable blunder.

Spread of English Sparrows in America. — The first impor-
tations of the house-sparrow (Passer domesticus) to North
America were made at Brooklyn, New York, in 1850 and 1852.
The second importation survived and multiplied. Subsequent
importations were made to Maine, Rhode Island, and Pennsyl-
vania, so that by 1870 the sparrow was firmly established in
the eastern United States. From this time on the sparrow
spread at a rate unparalleled by any native bird. By 1886
it had spread as far west as Kansas, and had established colo-

THE ENGLISH SPARROW 375

nies at Salt Lake City, San Francisco, and other outlying
regions; and throughout this territory it occurred in great
abundance. Since then it has penetrated west to the Rocky
Mountains, and south to Texas. This extraordinary spread
has been due to several causes. As alreacdy suggested, the
bird can adapt itself to various climatic conditions and its
fecundity is very great. Thus in our Southern cities there
are from five to six broods a year, and from four to six young
in each brood. Assuming that twenty-four young, half of them
females, are produced by a pair each year, and that all the
females breed when one year old, and successively for ten years,
and that there are no deaths, then in the tenth year 136 billion
individuals will have been produced from the original pair.
To the realization of the possible maximum of reproduction
there are, however, many checks, especially the destruction
of birds by accidents, disease, and beasts and birds of prey.

Food of English Sparrow. — The house-sparrow was intro-
duced for the purpose of destroying or holding in check the
“canker-worm” and the various other caterpillars which
destroy our fruit, forest, and shade trees. There is much doubt,
however, whether the house-sparrow is at all efficient in the way
of destroying insect pests, while it is quite certain that it fights
with and drives away our native insect-eating birds. More
important still, it destroys large quantities of grain in the field
as well as many kinds of garden produce, so that, on the whole,
the English sparrow must be reckoned destructive to agri-
culture. Of late years it has come into our Southern markets
as a substitute for the rice-bird, and it is to be hoped that there
will be a widespread demand for it in the market.

Increase of Exotic Species. — The extraordinary spread of
the English sparrow after importation to this country is not

376 ZOOLOGY

wholly explained by its large fecundity ; for although equally
reproductive in Europe it increases less rapidly there than
here. Also it is not due to any peculiarity of our country, for
the bird is a similar pest in Australia. Similar facts concern-
ing the spread of other animals lead us to conclude that it is
the new country which permits the rapid spread and conse-
quent destructiveness. Thus, when the cabbage-butterfly
(Pieris rape) was brought to this country, it spread with such
rapidity that, starting in 1860 at Quebec, it has now spread all
over the United States as far as the Rocky Mountains. Again,
the grapevine insect pest, Phylloxera, a native of this country,
but not particularly destructive here, has been accidentally
transported to France, and there it has wrought great havoc
in the vineyards. Another instance, this time of an aquatic
animal, shows the same result: the periwinkle, Littorina
littoria,' now the commonest snail on the seashore north of New
York, has migrated down the shore from Halifax since 1868.
This old species in the new country has almost driven out the
other shore mollusks, to such an extraordinary degree has it
multiplied. Now why should animals in a new country develop
with such unusual rapidity? It is because, coming into a new
country, they have left behind them their natural enemies, and
there has not yet been time for them to acquire new ones.
Eventually new enemies are gained, or their old ones over-
take them, and then the numbers of the exotic form become
reduced ; a new equilibrium becomes established.

Asan example of the structure of a bird, and for comparison
with the anatomy of the English sparrow, the common pigeon
may be taken.

General Form of the Body. — If the smaller (or “ contour ’’)

1 See page 216.

THE ENGLISU SPARROW 3)

Fig. 349. — The pigeon viewed from the left side with most of the body-
feathers removed. FEATHERS SysTEM: ad. dg. rmx, remex (flight) from the
base of the fingers; al.sp, false wing; ch.rmg, remiges on the ‘cubit”’
or forearm; hu.pt, feather tract of the humerus; lg, ligament of the
flights; md.dg.rmg, remiges of the mid-digit; mtcp.rmg, remiges of the
metacarpal region; pr.dg.rmg, remiges of the tip of the finger; pr.pigm,
wing web (patagium) in front of arm; pr.ptgm, patagium behind arm ;
ret, one of the tail feathers (rectrices) and the saes from which they have
been removed (ret’) ; sp.pt, feather tracts of the spine; v.apt, featherless
space of the belly. Other references: an, anus; au.ap, ear opening;
cr, cere; dg, 1, 2, 3, fingers; dg, 1, 2, 3, toes; na, nostril; net.m, nictitat-
ing membrane; o.gl, oil gland; ts.mtts, tarsus. From Parker and
Haswell.

378 ZOOLOGY

feathers of the body be removed from one side of a pigeon
(Fig. 349), it will be seen to consist of a head, trunk, and, behind
the vent, a rudimentary tail. In front the trunk is drawn out

Fic. 350. — Feathers of the common pigeon. A, quill feather, basal portion ;
cal, the quill; inf.wmb, lower depression; for admission of blood-vessel
and nerve; sup.umb, upper depression; rch, shaft. B, hair-like
feathers, ‘‘filoplumes.” CC, nestling down. From Bronn’s ‘ Tiesreich.”’

into a long neck connecting with the head. The length of the
neck gives great freedom of movement to the bead, a move-
ment useful not only in flight and in picking grain from
the ground, but also in enabling the bird to reach every
part of the plumage. There are two pairs of appendages, of
which the anterior is greatly modified, being without fingers,

THE ENGLISH SPARROW 379

and serving to carry the great flight feathers. The hinder
appendages, used as legs, bear four toes, whose great spread
serves to increase the base of support for the relatively large
body.

Body Covering. — The feathers are of two general sorts,
those which form a relatively close covering over the body
of the bird and serve to maintain its high temperature, and the
great quill feathers which are the main organs of flight. Those
which are borne on the fore limbs serve to propel the bird
through the air, whereas those which arise from the tail may,
by their change in position, control the direction of flight.
The earliest feathers of the young pigeon are called ‘ down ”’
feathers, and consist of a cylindrical base which breaks up into
many branches above the skin (Fig. 350C). Among the main
body-feathers of the adult there are found hair-like feathers
which break up into several branches at the tip (Fig. 350 B).
These feathers serve as connecting links to show the real
relations between feathers and hair. The remaining feathers
of the adult plumage are, however, much more complicated
(Fig. 350 4). They consist of a central shaft which passes
into the quill below the level of the skin. Outside the skin,
however, the shaft bears on each side a row of “ barbs,”
which, taken all together, make up the “ web ”’ of the feather.
The barbs cling together so that the web acts as a unit, and as
the web is concave toward the downward stroke and convex
toward the upward stroke, the air is held better in the down
stroke, and this is therefore the more effective in lifting the
bird than the upward stroke is in depressing it. When a single
barb is removed from the web, it will be seen to bear two rows
of microscopic organs which are the interlocking apparatus
(Fig. 351). The organs on that side of the barb facing the tip

580 ZOOLOGY

are called distal barbules, and are provided with hooks, whereas
the organs facing the base of the feather are called proximal
barbules, and bear flanges. The hooks of the one barb inter-
lock with the flanges of the next following barb, and thus all
the barbs are held together in one firm web.

Skeleton. — The bones of birds are exceedingly light, many
of them being hollowed out and filled with sacs connected with
the lungs and containing heated air. This hot air greatly

Fie. 351. — Structure of a feather. Two barbs are represented cut across.
Each bears to the left three ‘‘distal barbules’? armed with hooks which
engage in the flanges of the ‘proximal barbules”’ lying to the right of the
neighboring barb. After Pycraft.

increases the buoyancy of the bird in the air. The avial
skeleton differs from that of most other vertebrates in the
great length of the neck region, the compactness and rigidity
of the trunk, and the shortness of the tail (Fig. 352). The
latter ends in a square bone which consists of a lot of rudimen-
tary vertebrie fused together. This piece corresponds to most
of the long tails of reptiles, and in some fossil birds (Archeopte-
rix, see also Fig. 388) the vertebra of the tip of the tail are still
distinct. The skull is very compact and light, and the limits of
the different bones of which it is composed are hard to make out
except in young specimens (Fig. 353). The lower jaw is sup-
ported from the skull, as in the lower vertebrates, by a special

THE ENGLISH SPARROW 381

hinge called the “ quadrate”’ bone. Neither upper nor lower
jaw bear teeth in living birds, but fossil birds are known which
bear teeth. One of the most notable features of the skull of
birds is the remarkable length of both the upper and lower

car

Fria. 352. — Bones of the trunk of the pigeon: th.v./, first and th.v.5, last
vertebra of the thorax; s.scr, sacrum; cd.v, caudal vertebr, ending in
the tail piece, pyg.st. The ribs are short on the neck (cv.r); on the
thorax they consist of two parts, the vertebral (vr.r), and sternal (s¢.r)
ribs, of which the former bears the uncinate process (unc) ; scp, scapula;
cor, corocoid; fur, wishbone or furcula; acr.cor, process of the corocoid;
gl.cv, place of union of the humerus; sf, sternum, and its keel, car. The
pelvis includes: the ilium, 7, ischium, 7s, and pubis, pu.acth, acetabu-
lum for reception of the head of the femur; a.tr, for attachment of the
ligaments of the femur; is.for, foramen of ischium; obt.n, obturator
notch. From Parker and Haswell.

jaws, which are drawn out to constitute the beak. Another
feature is the enormous cavity reserved for the eye.
Surrounding the viscera are five pairs of ribs which connect
below with the huge breastbone or sternum, a bone remarkable
for its deep keel. This keel serves for the attachment of the
breast muscles, by means of which the powerful downward

382 ZOOLOGY

stroke of the wing is performed. The skeleton of the wing is
connected with that of the trunk by two bones, one of which

Fig. 353. — Skull of a young pigeon in three views: A, dorsal; B, ventral;
and C, lateral. With the aid of the skull of a young pigeon or chicken
one can find the bones which bear the names indicated: a/.s, alisphenoid ;
an, angular, and ar, articular of the lower jaw; bo, basioccipital; d,
dentary (but bearing no teeth in modern birds); eo, exoceipital; eu,
opening of Eustachian tube; f.m, great foramen of skull; fr, frontal;
v.o.8, interorbital septum; ju, jugal; Uc, lachrymal; /b.s, lamboidal
suture; m.eth, mesethmoid; mer, maxilla; rexr.p, maxillopalatine
process; na, na’, na’’, nasal; o.c, occipital condyle; or. fr, orbital plate
of frontal; pa, parietal; pa.s, parasphenoid; pl, palatine; p.ma, pre-
maxilla; pt, pterygoid; qu, quadrate; s.an, supraangular; s.o, supra-
occipital; sg, squamosat; (y, tympanic cavity; IJI-NXJI, opening for
cerebral nerves. From Parker's ‘‘ Zootomy.”

THE ENGLISH SPARROW 383

runs up to the vertebre and the other down to the breastbone.
The two halves of the girdle thus formed are kept apart
by a bone that serves as a spring, the so-called wishbone
(Fig. 352, fur). While the shoulder girdle is thus character-
ized by a high degree of elasticity as befits its important work
of supporting the strokes of the wing, the pelvic girdle, on the
other hand, consists of a pair of bones rigidly fastened to the
immovable sacral vertebre.

The skeleton of the wing consists of a single bone in the
upper arm, two bones in the forearm, and rudiments of three
fingersin the hand. The skeleton of the leg consists of a single
bone (femur) in the upper leg, two bones (tibia and fibula)
in the lower leg, a kneepan (or patella) at the joint between
the upper and lower leg, and a foot consisting of four digits
which are grown together in what corresponds to the sole of
the foot in man (the shank of the bird’s leg), but are separate
in the toes.

Organs of nutrition in the pigeon are much more com-
plex than in the lower classes of vertebrates (Fig. 354). From
the toothless mouth, with its long tongue, the long gullet leads
through the neck to enlarge into a capacious crop lying just
in front of the wishbone. Here the food, which consists
chiefly of grain, is thoroughly soaked and softened. Thence
it passes by a continuation of the gullet to the stomach, which,
as in most birds, consists of two parts; the first, which is
glandular; the second, or gizzard, which is muscular. In the
first part the grain is further softened and treated by the se-
cretions of the glands; in the second it is mechanically treated,
being crushed and ground by aid of small stones that have been
swallowed by the bird. From the gizzard leads the intestine.
In its anterior part the digestive processes are active, and it

ZOOLOGY

384

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THE ENGLISH SPARROW 385

is into this region that the principal digestive fluids (those from
the liver and pancreas) are poured. The great middle portion
of the intestine, together with a pair of blind sacs (ceca)
opening into it, serves for the absorption of the digested sub-
stances and, finally, the indigestible remnants are collected
in the rectum, whence they pass, through a cloaca, to the
external vent. The cloaca receives also the excretory products.

Organs of Respiration. — These also reach an extraordinary
complication in birds. From the larynx, which, as in man, is
supported by cartilages but is not, in birds, the vocal organ,
a long windpipe passes to the two lungs. Where the wind-
pipe begins to subdivide to form the bronchi of the lungs, there
is found the vocal organ of birds —the syrinx (Fig. 355) ;
nothing like it is found in any other class of vertebrates, and
it gains a very complex structure in the singing-birds. As it
would take a long time to describe the mechanism of the
syrinx, this will not be attempted; suffice it to say that the
sound is produced by the vibration of a membrane which is
stretched part way across the windpipe.

The respiratory organs proper are of two kinds — the lungs
and the air-sacs. The lungs (Fig. 355) are relatively small
organs and are not mere bags, as in the lower orders of verte-
brates, but spongy masses rich in blood-vessels. Through this
sponge-work the pure inspired air rushes on its way to the air-
sacs which lie beyond. Consequently the blood of the lungs
is bathed by a current of fresh air, and this insures that it shall
receive a maximum of oxygen and this, in turn, results in the
bird maintaining a high body temperature, 103° F. (40° C.), in-
stead of 98° F. (37° C.), asin mammals. The air-sacs of birds
correspond, in a way, with the little terminal sacs of the bron-

chi in ourselves, but some of these have become immensely
2c

386 ZOOLOGY

enlarged and occupy great spaces of the body and even com-

municate with the cavities of the bones.

These air-sacs serve

not only to diminish the specific gravity of the body, but also

the tidal air.

as reservolrs to receive

bp"

by /

Fic. 355. — The lungs of the pigeon, together
with the lower end of the trachea, viewed from
the ventral side: ¢r, trachea with the syrinx
(sy) at its lower end where the two bronchii (br)
branch off, eventually dividing into branches,
br’, br’. The pulmonary artery enters at
p.a, and the vein leaves at p.v. With the
lungs, various air sacs are connected at a.in,
the anterior thoracic; at p.in, the posterior
thoracic; at p, the abdominal; at sh.b, the
interclavicular, and at sp.b, the cervical. From
Parker's ‘‘ Zootomy.”’

pure blood from the tissues is received

From these reservoirs

some of the air is no
doubt absorbed by
the blood and other
fluids of the body;
the
are periodically

but reservoirs
emptied through the
air-tube, as are the
terminal sacs in our
own lungs.

Organs and Func-
tions of Circula-
tion. — The heart is
completely
into a right and a

divided

left side, as in man.
Each side has a re-
ceiving chamber or
auricle, and a dis-
charging chamber or
The im-

by the right auricle,

ventricle.

passes to the right ventricle, and thence is pumped into
a paired pulmonary artery, of which one branch goes to

each lung, where it breaks up into capillaries.

The re-

collected, oxygenated blood is returned to the left auricle,

1 Fig. 354,

THE ENGLISH SPARROW 387

enters the left ventricle, whence it is pumped to the tissues.
The great artery that carries blood from the left ventricle
is called the aorta. It quickly divides into a right and a
left branch, from each of which an artery goes to the head
with its brain and sense-organs, and to the wings and their
great muscles. The right branch of the aorta passes up around
the throat and reaches the vertebral column and runs under
this (as the dorsal aorta) to the tail. It gives off blood-vessels
to the food-canal and its glands, to the legs, to the kidneys, and
other organs. The blood which is thus carried by the arteries
to various organs of the body breaks up in each of them into
capillaries and is finally collected into veins which eventually
empty, as stated above, into the right auricle. While passing
through the capillaries, the blood gives up its oxygen and re-
ceives from the organs carbon dioxide and other waste products
of activity lying in these organs.

The organs of excretion consist of a pair of bodies of compact
form like those of reptiles and mammals, and in striking con-
trast to the elongated, segmented kidneys of Amphibia. This
kidney, indeed, represents only the hinder end of the kidney
of Amphibia. It is richly supplied with blood that carries ex-
cretory products which, passing from the blood-vessels, enter
little tubes. These tubules eventually empty into a central
basin which, in each kidney, connects by a larger tube with
the cloaca and the exterior (Fig. 354).

The Organs and Functions of Reproduction. — In the female
the ovary and oviduct of the right side has atrophied ; only
that of the left side persists. The eggs grow, in the oviduct,
to an enormous extent by the addition of yellow food matter
—the yolk. As a yolk passes down the oviduct a layer of

albumin or ‘

‘white ’’ is poured around it; next a thin mem-

388 ZOOLOGY

brane, and lastly a hard, white shell. Two of these eggs are laid,
one after the other, in successive days, and then incubated by
the parents, who by sitting on them maintain them at the tem-
perature of the body, so that the egg develops. After fourteen
days the young pigeon hatches and is fed and brooded by the
parents for a time longer until it is able to care for itself.
The muscular system is best developed in connection with
the function of flight. Every one who has eaten a chicken or

Fic. 356. — The brain of the pigeon, left side: olf, olfactory lobe; ch,
cerebral hemispheres; pn, pineal body; cb, cerebellum with a side lobe
at f; ot, optic tract; mo, medulla oblongata; J-NJJ, cranial nerves;
spJ, spinal nerve. From Parker's ‘t Zootomy.”’

turkey knows of the great “ breast’ muscles. These consti-
tute “ white ” meat in the turkey because they are relatively
bloodless, being little used for flying; but in pigeons, which
fly readily, the breast muscles are full of blood and are dark.
The great breast muscles depress the wing, the reaction to
which keeps the bird in the air. The other muscles of the
body are less important. Those of the neck and tail are well
developed, corresponding to the mobility of these parts, but,
owing to the compact, immobile nature of the trunk proper, the
musculature of that region is very slight.

THE ENGLISH SPARROW 389

The nervous system consists of the brain, spinal cord, and
the sympathetic system. The brain shows a great advance .
over reptiles, particularly in the development of the hind
brain, or cerebellum —the centre of codrdination (Fig. 356).
Since flight demands extreme codrcdination, we can under-
stand the large cerebellum of birds.

Fic. 357.— Median section through the eye of the pigeon: cn, cornea;
ir, iris; l, lens; cl.pr, lens muscles; pet, pecten; opt.nr, optic nerve;
rt, retina; ch, choroid coat; scl, sclerotic coat. After Vogt and Yung,
from Parker and Haswell’s ‘‘ Zoology.”

Sense-organs. — As befits such active animals, pigeons, like
birds in general, have well-developed sense-organs. Organs of
smell, lying at the base of the beak, and those of hearing, having
much the same structure as in man, are present. But the
most perfect organ is the eye which has relatively a large size.
It differs from that of man in its lenticular (compressed) form,
well adapted to the vision of distant objects. A peculiar organ

390 ZOOLOGY

lies in the aqueous humor in front of the entrance of the optic
nerve — it has the form of a comb (whence called pecten) and
is deeply pigmented, but its function is quite unknown (Fig.
357).

The class of Birds, or Aves, as they are technically called,
is divided into eleven orders as follows: —

1. The running birds: Birds incapable of flight because
their wings are rudimentary, e.g. Ostriches.

2. The swimming birds. These are the web-toed birds like
the loons, gulls and terns, petrels, pelicans, ducks, geese, and
swans.

3. The shore birds. These possess long, stilt-like shanks
with slight web; such are the flamingoes, herons, storks,
cranes, snipes, and plovers.

4. The ground birds, including the turkeys, grouse, fowl, and
quail.

5. The pigeons, perchers on rocks, with all four toes on the
same level.

6. The birds of prey, with hooked beak and claws (talons),
including the vultures, hawks, and owls.

7. The talkers, with beak shorter than high, including the
parrots, paroquets, ete.

8. The cuckoos and kingfishers.

9. The woodpeckers, with long beaks fitted for drilling into
bark.

10. The long-winged birds, or humming-birds, swifts, and
goat-suckers, of varied form, for the humming-birds have
slender bills, but the other groups have short bills and large
mouths. The wings are generally long and pointed.

11. The perchers, including most of the common migratory
birds.

THE ENGLISH SPARROW 391

The order of runners (Cursores) includes the African ostrich,
the American ostriches, or rheas, the cassowaries of the East
Indies, and certain wingless birds of New Zealand (Apteryx !),

Fig. 358. — Apteryx australis, with egg. From a specimen in the Royal
College of Surgeons, London. From Parker and Haswell, ‘‘Text-book of
Zoology.”

These are regarded as the most lowly developed of the birds;

the vanes of their feathers are not united, but separate to form

a sort of hair-like covering to the body. The African ostrich

is the largest living bird. It wanders in families or flocks in

the deserts of Africa, and feeds on grass, grain, and small

1 Fig, 358.

392 ZOOLOGY

animals. It also swallows undigestible matters, such as stones,
which probably aid it in triturating its food. The nest consists
of a hollow scooped out of the earth, into which about thirty
eggs are laid. Ostrich feathers are used for ornament, and so
important is the commerce in these articles that ostriches are

Vy

FOX

Fic. 359. — Common tern (Sterna hirundo).

extensively farmed in South Africa, southern California, and
Arizona. The feathers are cut off and not pulled out, so that
the operation of gathering the feathers is a painless one for the
bird, but attended with some risk to the operator.

The swimmers, or Natatores, comprise the ducks and geese,
the pelicans, the petrels, the gulls and terns, and the divers.
Of the geese, the wild goose, or Canada goose, is most commonly
seen in its migrations. Of the native ducks we have many
kinds, almost all rapidly disappearing before the “ sportsman.”
The pelicans are large fish-eating birds, with a huge bag-like

THE ENGLISH SPARROW 393

lower bill. In this country the white pelican is not un-
common. The large-winged petrels follow in the wake of
coastal vessels. The terns, which are slender birds with a
straight bill,! were once abundant along our coast, but have
been decimated to “ ornament” bonnets. The gulls, which

Fic. 360. — Spotted sandpiper (Actitis macularia).

are heavier than the terns, and have hooked bills, are still abun-
dant along the seashore and Great Lakes. Finally, the loons
are large birds, powerful fliers and swimmers, which are found
in the lakes of the Northern Hemisphere. They are quick
divers, and can swim under water for a considerable distance.

The waders (Grallatores) include a great number of shore
birds known as plovers, sandpipers, snipes, rails, cranes, herons,
and storks. The plovers walk and fly along shore, picking up

1 Fig. 359.

394 ZOOLOGY

worms, mollusks, and amphibians; the golden plover is a well-
known game bird. The snipes are found in meadows or, less
commonly, in woods. One of the most common is the spotted
sandpiper, also called ‘“ tip-up ” from its rocking movements
(Fig. 360). It is seen walking around the margins of ponds and
rivers. Woodcock and large snipe are found in moist places.
Among the herons, our great blue heron attains a length of

Fic. 361. — Ruffed grouse (Bonasa umbellus).

four feet, and is a notable resident of swampy regions, while
the egrets have been practically exterminated to meet the de-
mands of milliners.

The order of scratchers (Gallinee) includes a number of ter-
restial birds of large size, especially the grouse or partridges,
the pheasants and common fowl, the guinea-fowl, and the tur-
keys. On account of their large size and well-flavored flesh,
they are much used as human food. The grouse of America
include the familiar “ bob-white,” or quail, which is being

THE ENGLISH SPARROW 395

rapidly reduced in numbers in populous regions; the Canada
grouse, which does not occur south of New York; the ruffed
grouse of the Eastern States;! and the prairie chicken of the
Great Plains, which has
also become almost exter-
minated. In Europe the
large “capercaillie””? and
the blackcock are favorite
game birds. The pheas-
ants are characteristic of
southern Asia and China ;
they comprise some of the
most brilliantly colored
and greatly ornamented
of birds, such as the
peacock and the golden
pheasant. Here also be-
long our barnyard fowl
derived from a wild spe-
cies, Gallus bankiva, in-
habiting northern India,
the East Indies, and the
Philippines. The guinea-
fowl is a native of Africa,

where it goes in large Fic. 362.— Passenger pigeon (Hctopistes

flocks and is difficult of Pugr nents)

approach. The turkeys are North American birds. The

wild turkey formerly occurred over all the United States

and Mexico. It was first taken to Europe in 1524, was domes-

ticated there, and now occupies much of its former habitat as
1 Fig. 361.

396 ZOOLOGY

a domesticated fowl. From this brief view we see that the
family of Gallinacei is, for man at least, the most important
family of food-birds.

The order Columbine includes the pigeons and _ allies,
characteristic of the Eastern Hemisphere. The most inter-
esting species of the group — the dodo and the solitaire, for-
merly inhabitants of the islands of Mauritius and Rodrigues,
respectively — have become extinct within historic times
through the settlement of these islands by whitemen. These
birds had rudimentary wings and tail. Their nearest living
ally seems to be the “
The pigeons proper are represented in North America by three
wild species (Fig. 362). The domesticated pigeon, Columba
livia, is a native of southern Europe or western Asia.

manu-mea’”’! of the Samoan Islands.

The birds of prey (Raptores) include eagles, hawks, and
falcons; the vultures; condors; and owls. These birds feed
chiefly on birds and mammals, which they capture alive in
their claws or beaks; a few live on carrion. They occur in all
parts of the globe. The bald eagle, used as a symbol of the
republic, is the commonest of our eagles. Among our hawks,
the sparrow-hawk, which is only about the size of the robin,
is one of our most abundant; others are the sharp-shinned
hawk, which kills birds almost exclusively and is especially
destructive to poultry,? and Cooper’s hawk, which is also de-
structive to birds. These two hawks have practically no
redeeming qualities, except the fact that they prey upon the
English sparrow. The vultures are represented in our fauna
by the turkey-buzzard which, like other members of the family,
feeds on carrion. The condor is the largest of the American
Raptores. It preys even upon live sheep and calves. The

1 Redbird, 2 Fig. 363.

THE ENGLISU SPARROW 397

owls, which live in dark holes and feed upon small mammals
at night, are found over most of the globe. Our commonest

species is the reddish gray screech owl.2 The great horned

Fic. 363. — Sharp-shinned hawk (Ac- Fic. 364. — Screech owl (Megascops
ctipiter velox). asto).

owl is an inhabitant of wooded tracts, and is destructive to
poultry and small mammals. The snowy owl is one of the
handsomest of all owls, and is frequently seen stuffed in
houses in Europe as well as in North America.

The parrots and cockatoos (Psittaci) are sometimes called

2 Fig. 364.

598 ZOOLOGY

“climbers.” In the cockatoos the feathers of the head are
elevated to form acrest. In the parrots there is no such crest ;
in one subdivision the tail is long; inasecond, very short. The
representatives of this family are found almost exclusively in
the tropics, in Brazil, the Moluccas, and in Australia. In gen-

Fie. 365. — Conurus carolinensis, the Carolina paroquet. One-fifth nat.
size. After Wilson.
eral, these birds have a loud voice, and certain species may be
trained to articulate words and combine them into sentences.
There is only one parrot native to the United States — the
Carolina paroquet (Fig. 365). This formerly occurred north
to the Ohio River, but it has been within recent years practi-
cally exterminated by plumage hunters.

THE ENGLISU SPARROW 399

The toucans and cuckoos on the one hand and the king-
fishers on the other are grouped into the order Coccyges. The
toucans are characterized by an enormous bill, whichin extreme
cases is as long as the rest of the bird. It would be extremely

Fie. 366. — Belted kingfisher (Ceryle alcyon).

heavy were it not filled with air spaces of great extent. These
birds inhabit Brazil. The great hills are of use in feeding on
fruits. Filling the place in the Old World of the toucans of the
New are the hornbills of Africa and Asia, which are likewise
frugivorous. The cuckoos are typically represented by the Old-
world cuckoos. Like our own cow-bird, they have the peculiar

400 ZOOLOGY

habit of laying their eggs in the nests of other birds, espe-
cially insectivorous birds, where they are brooded and the young
are fed by the foster-
mother. Our native
cuckoo, however, broods
its own eggs, and is a
useful insectivorous bird.
The kingfishers are also
placed in this group.
They are especially an
Old-world family, but
one genus (Ceryle) has
found its way into the
Americas. These birds
feed chiefly on fish, and
they have gained a com-
pact, oily plumage to
prevent them from get-
ting wet when they
plunge for their prey.
Our species is known as
the belted kingfisher
(Fig. 366).

The woodpeckers, or

Fic. 367. — Flicker (Colaptes auratis).

Pici, include for the
most part arboreal birds which feed chiefly on insects,
and have loud, harsh cries. The common idea that they
are sap-suckers and destructive to trees seems to be true
only of one of our species — the yellow-bellied wood-
pecker. The heavy, long bill enables woodpeckers to
peck holes in trees for wood-eating insects, and the long,

THE ENGLISH SPARROW 401

barbed, protrusible tongue aids in removing the prey. Our
commonest woodpeckers are the golden-winged woodpecker,
or flicker,! the red-headed woodpecker, the hairy woodpecker,
and the downy woodpecker. An interesting question con-
cerning the golden-winged woodpeckers of the East and South-
west is whether they
hybridize where _ their
areas of distribution over-
lap.

The “long-wings ” in-
clude the humming-birds,
swifts, and goat-suckers.
The humming-birds are
mostly small species,
limited to our hemisphere,
and characteristic of the
tropics. They fill the
same place among the
birds that hawk-moths do

among insects, in so far as
they are fitted to visit Fic. 368. — Ruby-throated humming-bird
trumpet-shaped flowers. recs SONDRA
They do not feed solely upon nectar, but devour in-
sects also. They are usually brilliantly colored, and fly
with great swiftness, nest in trees, and lay only two white
eges. One species, the ruby-throated humming-bird, reaches
New England and Canada (Fig. 368).

The swifts have a broad gape, and no bristles at the base of
the bill. They have habits much like swallows, and are found
especially in the warm parts of the world. Most species of this

1 Fig. 367.
2D

402 ZOOLOGY

family have salivary glands, whose secretions aid in cementing
the nest. Our common representative of this group is the
chimney-swift, or chimney-swallow.! Certain Chinese species
make nests entirely of the mucilaginous secretion of the sali-
vary glands; these constitute the edible birds’-nests of the
Chinese. The goat-suckers include night-flying birds, with
exceedingly broad gape and insectivorous habits. The night-

Fia. 369. — Nest of chimney-swift. Photo. looking down chimney, by
D. and 8.
hawk of North America, and the whippoorwill, named for its
characteristic night cry, are familiar examples.

The order of perchers, or Passeres, is the most important for
us because of the abundance of species and individuals included
init, and because of the intimacy that many of them have cul-
tivated with man. The representatives of the order that live
in the United States are arranged into about fifteen families,
concerning each of which a brief account follows:

The flycatchers (or Tyrannidie) are an exclusively American
family, feeding on insects. The best-known representatives are

| Fig. 369.

THE ENGLISIT SPARROW 403

the courageous kingbird (Fig. 370), the wood pewee (Fig. 371),
and the water-loving pheebe.

Fic. 371. — Nest of pewee. Photo. by D. and 8.

404 ZOOLOGY

The larks are a family chiefly of Old-world birds of dull
color, building a rough nest on the ground, and feeding on seeds
and insects. The skylark of Europe is renowned as a songster.

Fie. 372. — Blue jay (Cyanocitta cristata).

In this country we have one representative of the family, the
horned lark, found also in Europe.

The crows (Corvidie) and their allies are all of them birds
of large size and omnivorous, but prefer animal food. The
crow, the raven of the West and of Europe, and the blue jay

THE ENGLISH SPARROW 405

(Fig. 372) are the commonest North American species of this
family.

The blackbird family (Icteridz) includes numerous species
with different habits. These are also confined to America, and

Fia. 373. — Purple grackle (Quiscalus quiscula).

are especially abundant in the tropics. They feed, for the

most part, on seeds. The commonest representatives are the

crow blackbird,! of large size and iridescent plumage; the

Baltimore oriole, which weaves a hanging nest; the orchard
1 Fig. 373.

406 ZOOLOGY

oriole, with less orange than the preceding ; the large meadow-
lark, brownish above and yellow below ; the red-winged black-

bird; the cow-bird, which builds no nest, but lays its eggs in

Fic. 374. — The American crossbill (Loria curvirostra).

the nests of various small birds; and the ‘“ bobolink,” as it
is called in the North, whose song is the merriest of all birds.
In the South, whither the bobolink migrates in the winter, it is
a great pest in the rice-fields, and is known as the “ rice-bird.”
It is slaughtered there as a game bird.

The sparrows (Fringillidze), to which family the English

sparrow belongs, constitute a large group comprising over

THE ENGLISH SPARROW 407

five hundred species, found in all parts of the world, ex-
cepting, until recently, Australia. In the United States
it is the largest family of birds, comprising in most. places
about one-seventh of the species. Among common or
striking native Fringillide may be mentioned the crossbills,!
yellowbird, vesper-sparrow, white-throated sparrow, tree-

Fie. 375. — Chipping-sparrow (Spizella socialis).

sparrow, chipping-sparrow,? snowbird, song-sparrow, fox-
sparrow, chewink, cardinal grosbeak, rose-breasted grosbeak,
and indigo-bird. Most of these birds are known to every
country boy.

The tanagers are exclusively American and belong especially
to the tropics. They live in the woods, and feed on berries and
fruits. The northernmost member of the family is the scarlet
tanager of the eastern United States (Fig. 376).

The swallows are found over the world. They are powerful
fliers, and are insectivorous. Formerly all of them bred in

1 Fig. 374. 2 Fig. 375.

408 ZOOLOGY

Fic. 377. — Barn-swallow (Chelidon erythrogaster).

THE ENGLISIT SPARROW 409

boughs, and hollow trees, cliffs, and some species still retain
these habits. The best-known species are the bank-swallows,
which, living in colonies, form
numerous holes in railroad cuts
and sand-banks in general; the
white-bellied swallow, abundant
about water; and the barn-swal-
low (Fig. 377), with a chestnut
belly, which builds its nest in the
rafters of our barns (Fig. 378.)

The waxwings are found over Ftc. 378. — Nests of barn-swal-
the Northern Hemisphere. They Po vee eens
are migratory, go in flocks, feed on insects and fruits, and
chatter rather than sing. Our commonest species is called
“ eedar-bird ” (Fig. 379).

The shrikes are of world-wide distribution. They are
vigorous, pugnacious birds, which have the habit of impaling

grasshoppers and other small animals upon thorns, and leay-
ing them there. In Germany there is a tradition that the
shrike daily impales nine victims, and it is hence commonly
called Newntodter, or “ ninekiller.”’ The impaling seems to be
done chiefly in the winter time, and apparently has for its pur-
pose the storing of food against possible famine. Among birds
frequently destroyed by them is the English sparrow, and it has
been suggested that the shrikes should be encouraged to live in
parks of cities infested by sparrow pests; but unfortunately the
shrikes do not confine themselves to this intruder. We have
two species of shrikes, a northern (Fig. 380) and a southern.

The vireos or greenlets are bright, handsome, and exclusively
American birds. The commonest species are the red-eyed
vireo (Fig. 381) and the yellow-throated vireo.

410 ZOOLOGY

The family of wood-warblers is the peculiar glory of
America. It contains numerous small, mostly brilliantly col-
ored birds, which migrate. Although a few of them — like the
redstart, the Maryland yellowthroat (Fig. 382), the redpoll

a

Fig. 379. — Cedar waxwing (Ampelis cedrorum).

warbler, the chestnut-sided warbler, and the vellow warbler
are abundant, few of the thirty-five or forty Eastern species can
be said to be commonly known except to careful observers of
birds; for during the migrations they hide in thickets, and are
extremely shy.

The wrens are characteristic of South America, but some have

THE ENGLISH SPARROW 411

Fic. 381. — Red-cyed vireo (Vireo olivaceus).

412 ZOOLOGY

spread into North America and northern Europe. Our house
wren, which is a near relative of the European house wren,
is an active little brown bird, with asharply bent-up tail.! In
this same family belong the mocking-hirds, the centre of whose

Fic. 382. — Maryland yellowthroat (Geothlypis trichas).

distribution is Central America, the West Indies, and the south-
ern United States. The large brown thrasher and the catbird
are familiar over the country. The mocking-bird does not

1 Fig. 383,

THE ENGLISH SPARROW 413

get far north into New England. It is regarded by many as
superior to the nightingale as a singer.

The family of titmice includes also the nuthatches. The tits
are chiefly Old-world birds, but we have a common represen-
tative in the black-
capped chickadee, well
known from its cheerful
whistle. In this family
belong the nuthatches
which run over tree-
trunks, head up or down,
indiscriminately (Fig.
384).

The little brown
creeper which travels
over the bark of trees
much as the nuthatches
do and uses its tail-
feathers as props against
the tree-trunk (Fig. 385)
belongs to an_ allied
family.

The family of thrushes
includes several common
American birds, —the robin, abundant about houses during
the summer, but for the most part migrating south from New
England during the winter; the wood or song thrush,! one of
our finest songsters; the bluebird, one of the earliest of our
migrants, with “the sky on its back and the earth on its

Fic. 383. — House wren (Troglodytes aédon).

breast.”
1 Fig. 386,

414 ZOOLOGY

Bird flight. — The difficulties which must be overcome in
order to fit birds for flight are, first, that of sustaining the heavy
body in a medium of such low specific gravity as the air; and,
secondly, that of progression in this medium. To diminish the
difficulty of sustaining the body, the specific gravity is reduced

a)
ve!

Fic. 384. — White-breasted nuthatch (Sitta Fig. 385. — Brown creeper
carolinensis). (Cerithia familiaris).
to a minimum by great air spaces in the body, which exist even
in the hollow bones. The body is kept from being overturned
in the air by the position of the wings, which are placed high up
on the trunk, while the digestive organs, breastbone, and breast
muscles are placed low. To aid locomotion, the general form
of the body is made conical, so as to offer little resistance to the
air, while, by varying the position of the head, wings, and tail,

THE ENGLISH SPARROW 415

the centre of gravity is quickly shifted. In starting to fly, the
bird gains an initial velocity, if on the ground, by springing into
the air, or if on a tree, by combining the velocity due to gravity
with a pushing from the limb; but aquatic birds strike the

Fig. 386. — Wood-thrush (Turdus mustelinus).

surface of the water with their wings. The best fliers have
relatively large, pointed wings. Three methods of flight are
employed by birds when once in the air: (a) stroking the air
with the wing; (b) gliding or skimming ; and (c) sailing or soar-
ing. Some birds can use all three methods, and all good fliers
use the first two. In the stroke the wing moves downward and
forward, backward and upward, so that the tip of the wing

416 ZOOLOGY

describes a © ; and since the bones of the wing — its most
rigid part —are at its front edge, the hinder edge tends to
lag behind the front edge, so that the wing as a whole hits the
air in a plane which is not perpendicular but oblique to the
direction of impact. Consequently on both the up and the
down stroke one component pushes backward and tends to
drive the bird forward (Fig. 387). In gliding, the wings are
spread, but are not flapped; progression depends upon an
acquired velocity, as in
aeroplanes, or upon the
wind. In soaring, the
wings remain motion-
less, and the bird does
not lose its velocity nor
tend to fall. The way

Fig. 387. — Diagram showing resolution of
forces (A) on down and on up strokes of the
wing; the component B, in both cases exerts jpn which the bird is
a backward pressure that drives the bird :
forward; while the component C’ keeps the supported and carried

bird up. along is uncertain. It

seems to depend upon certain favorable currents in the air.

Birds, like insects, have the closest economic relations with
man. A few of them, chiefly belonging to the orders of swim-
mers and grouse, are very important as human food; but
most of them concern man on account of their feeding habits,
which are either favorable to man, as when noxious insects are
destroyed, or injurious, as when grain-fields are ravaged or
other birds are preyed upon. Unquestionably the vast ma-
jority of birds are commercially advantageous to man. The
Raptores are only partially so, for they feed entirely upon
animal food, chiefly birds and small (usually destructive)
mammals. The bobolink and the American crow, to be sure,
together annually destroy millions of dollars’ worth of grain,

THE ENGLISH SPARROW 417

yet during the breeding season they both feed much upon
insects. Outside of the group Raptores, there are few, if any,
completely noxious birds, and even many of the hawks are
efficient destroyers of insects. Legislation directed toward
the destruction of any kind of birds, excepting the English
sparrow, the Cooper’s and sharp-shinned hawks, and perhaps
the crow, is quite as apt to do harm as good.

Bird Protection. — Travellers in certain parts of Europe,
where the poverty and ignorance of the people have led them
to prey upon birds, have remarked on the desolation of a bird-
less country. The natural enemies of insects being destroyed,
there is no adequate check to the destruction of vegetation by
insects, and the beauty of a forest landscape is missing. North
America has been richly provided with a native bird fauna; but
within the last few years it has become plain that most of our
species are undergoing reduction, and many are near extermi-
nation. Careful inquiries recently made indicate that during
the past fifteen years the number of our common song-birds
has been reduced one-half, and the number of certain birds
prized as food or ornament has been reduced to one-fourth. At
the present rate, extermination of many species will occur dur-
ing the lives of most of us. The causes of this destruction of
birds are numerous. The most efficient cause is the shotgun
in the hands of boys and thoughtless men and of those who
gather bird skins to meet the demand for bonnet “ ornaments.”’
Very great destruction is also caused by egg-collectors, who
annually gather scores of thousands of eggs, often of rare birds.
The disastrous results of killing birds need only to be appre-
ciated in order to put a stop to this destructiveness. No
species, once exterminated, can ever be replaced, and the world

cannot afford to lose any of the objects of beauty and utility.
25

418 ZOOLOGY

Extinct Birds. — The destruction of species of birds goes on
fast enough without the more efficient aid of man. We know
of species which have become extinct within recent times
through the introduction of new enemies among them. Such

Fig. 388. — Hesperornis regalis. The restored skeleton. After Marsh.

was the fate of the dodo and of the great auk of Labrador.
The remains of species which lived in very remote periods
have been preserved to us in the rocks. The oldest known
fossil bird, Archzeopteryx, of the Jurassic age, has a long tail
like a lizard; but feathers, which are only modified scales,

THE ENGLISH SPARROW 419

were present even in this oldest known bird. In the Creta-
ceous rock deposits of the Great Plains there have been found
fossil birds with teeth set in sockets or grooves, precisely as
they are to-day in reptiles (Fig. 388). These remains show
us in the clearest manner that birds have been derived from
reptiles or both from a common source. Indeed, the two
groups are closely related anatomically, and are often united
under the name Sauropsida, or lizard-like animals.

CHAPTER XXVI

THE MOUSE: A STUDY OF THE EVOLUTION OF
DOMESTIC ANIMALS

Man loves company, not only of his own kind but also that of
other animals, and many other animals similarly enjoy society.
The dog is one of these. In the wild state it goes in packs and
when alone gladly attaches itself to man. Such a mutual,
social instinct was probably the earliest impulse to associations
between man and other animals such as dogs and cats. More-
over, man found that certain other animals, which might not
share his fireside, could nevertheless be trained to stay about
his tent or hut, where they could be utilized for food, for
clothing, or for burden-bearing. Thus man came to domesti-
cate cattle, goats, sheep, and horses. A list of the more fa-
miliar domesticated animals is as follows:

Hairy animals (Mammalia): cat, dog, rabbits, guinea-pig,
mouse and rats, pig, horse (including the ass), cattle, llama,
camels, sheep, goats, and elephants.

Birds: canary bird and various finches, paraquets, poultry,
pheasants, ducks and geese, guinea-fowl, turkey, and ostrich.

Fishes: goldfish. Insects: bee, silkworm.

Some of these domestic animals deserve a fuller description.

The cat is a solitary animal with a strong homing instinct.
There are several domestic races, such as long-haired, short-
haired, and tailless (or Manx). In each of these races there
white, black, tortoise-shell, tiger, and

420

are various color types,

THE MOUSE 421

1. The Manx or tuailless cat. 2. The Siamese cat.

3. Short-haired cats. Black 4. A white long-haired Angora
and white, and tiger marked. cat.

Fic. 389. — A group of domestic cats, illustrating the results of domes-
tication.

439 ZOOLOGY

maltese. Cats are carnivorous. Since they are sly, noiseless
of tread, and quick of movement, they are the most effi-
cient check upon the multiplication of house mice and rats
(Fig. 389).

The dog belongs to a species that hunts in the wild state
in bands or packs. It becomes attached to man, and readily
removes with him to live in a new locality. Numerous races
are recognized, varying in size and proportions of parts. The
mastiffs and great Danes are breeds of large size, while the
Japanese bulldogs and the toy spaniels are very small. The
hair of dogs, like that of cats, is either long or short. It may
be either straight, or curled as in the setters. In color it is
white, black, red, and piebald, that is to say, a mixture of
all three colors. Races of dogs differ in their mental as well
as their physical attributes. Some dogs, like the collies, are
gentle, while others, notably the bulldog, are very pugnacious.
The dog was probably one of the first animals to be domesti-
cated by man, although economically less useful to him than
other races later acquired (Fig. 390).

Cattle are easily maintained in confinement, and furnish
milk, meat, and hides. They originated from some unknown
Asiatic species and have been domesticated for over 6000 years.
The races differ in size and in the quality and quantity of milk.
The large Holstein produces the greatest amount of milk, while
the small Jersey produces milk which contains a large percen-
tage of butter-making fat, and the Hereford and Angus breeds
produce large animals for beef.

Horses were domesticated for purposes of transportation
and general work. It is believed that two species have been
combined to make our common carriage horse. One is the
small Siberian pony that was early brought into central and

. 390. — Types of races of domestic dogs: a, rough-coated St. Bernard ;
old English sheep dogs; c,d, small pet dogs; e, English setter;
bull dog.

424 ZOOLOGY

western Europe; the other is the large, more gracefully molded
Arabian horse. The horse of the ancient Gauls was so small
that it was rarely used for horseback riding, but only for draw-
ing chariots. Later it was much improved by crossing with
the Roman horses, which had much Arabian blood. Horses
range in size from great truck and draft horses of the Per-
cheron type to the little Shetland pony. In color they are
white, black, chestnut, and red, or bay, or the colors may be
mottled and dappled. The gait of the horse also varies from
running to pacing and trotting.

Sheep and goats have been domesticated both for their flesh
and for their wool or hair. Goat’s milk is especially prized
in hospitals as an excellent food for young children and invalids,
and from it cheese is made. The different races of sheep are
characterized by various qualities. Thus, while most breeds
are hornless, the Dorsets are horned. The merinos have very
abundant wool, which is of good quality as well. The South-
downs have black faces and feet and are prized for the qual-
ity of their mutton. Of the goats, the two principal domesti-
cated varieties are the short-haired and the long-haired, or
Angora. The hair of the latter (mohair) is used in the manu-
facture of a cloth to cover furniture and buttons, and is em-
ployed for other purposes where great resistance to wear is
essential.

Domestic rabbits depart little from the wild type although
they have long been kept in captivity and bred for food and for
their hair which is used in the manufacture of felt. Both long-
and short-haired varieties are known. The ears of some varie-
ties are short, while others have ears so long (lop-ears) that
they drag upon the ground. Guinea-pigs occur in races that
vary in color and length of ears.

THE MOUSE 425

Of the domesticated birds the poultry are the most impor-
tant. Under the term “poultry”’ are included the common fowl
of the barnyard, ducks, geese, turkeys, guinea-fowl, and pea-
cocks. The common fowl is one of the main sources of animal
food in the United States. The annual value of eggs produced
and poultry sold is estimated to amount to about half a billion
dollars. A hen may lay eight times her weight in eggs in a
single year at an average total valuation of $3 for the year.
The principal kinds of fowls are the game breeds,’ which are
most like the wild fowl of the jungle; the Mediterranean breeds,?
which are prolific layers, but do not, as a rule, incubate their
eges; and the Asiatic fowls,’? which are valuable for their great
size and because they make excellent mothers. Combinations
of these three groups have been made in profusion. Fowls
have been kept under domestication in China for over 2000
years. They are not mentioned in the Old Testament, and
hence probably reached Syria only shortly before our era
began.

Pigeons have been derived from a blue, wild, rock pigeon
having two black bars on the wings. From this ancestral
form over a score of well-marked varieties have been produced
by the fanciers. The pouters, fantails, and the tumblers are
familiar examples. Not only are pigeons interesting to bird
lovers, but they have considerable economic value, since the
young birds, known as squabs, are highly esteemed as food
because of their gamy flavor.

Of the fishes only the goldfish can be regarded as domesti-
cated. It has been cultivated by the Chinese and Japanese in
a great variety of colors and with extraordinary modifications
of the fins.

. 1 Fig. 391,c. 2Fig. 391,a. *Fig. 391, d.

Oonniitio aeF Wie Z
OF BELIAALE POULTREJOURRAL

Fic. 391. — Types of domestic fowl :
Rock; c¢, English game bantams;
bantams.

a, rose-comb white leghorn; b, barred Plymouth

d, dark Brahmas, male and female; e, seabright

THE MOUSE 427

Among insects bees have been domesticated from early
times. The habits of the tame bees differ little from those in
the wild state. In place of a hollow tree a box is provided
which is so arranged that an excess of honey may be withdrawn
without jeopardizing the life of the colony. The different races
of domesticated bees differ much in color and in amiability.
Perhaps of greater economic importance than bees are the silk
moths, which manufacture silk threads in the construction of
their cocoons. By proper treatment in hot water the threads
are unwound from the cocoon. A number of these fine threads
are spun together into stouter threads suitable for use in the
manufacture of silk cloths.

This review of domestic animals shows that species that are
under the care of man are much more variable than wild species.
Why is this? Because man controls the breeding of domesti-
cated animals. He carefully observes the young produced
each year, and selects those that best conform to his ideal, or
which possess some striking peculiarity which may be of eco-
nomic importance. Any such peculiarity of an individual will
be transmitted to its offspring. Thus a race may be improved
or a new one founded. In the formation of perfected races,
two processes are involved. First, an individual must appear
with some new, some peculiar characteristic. Second, there
must be a selection, a preservation, of the most perfect de-
scendants of this individual. By such means the race is im-
proved. Charles Darwin,’ to whom is due the present accept-
ance by naturalists of the theory of evolution, came to the
conclusion that nature works with species in the same way that
man does. Of the vast number of individuals produced in
each generation in the wild state only a few survive, and these,

1 Tig. 392,

42s ZOOLOGY

in the long run, will be the most perfectly fitted to their environ-
ment. Darwin, however, did not sufficiently appreciate the
process in nature that corresponds to the breeder’s preserva-
tion of a new peculiarity. The Dutch naturalist De Vries
has shown that in nature peculiarities, mutations, frequently
suddenly occur and these may
| constitute the beginnings of new
species. These two processes,
the occurrence of variations and
the inheritance of them, are
sufficient to bring about those
great changes in organisms which
constitute evolution.

As a concrete illustration of

the evolution of a domestic race,
the fancy mice may he taken.
Fancy mice have been derived
from the house mouse. The
house mouse is of an ashy gray
color. When its hairs are care-
fully examined, it will be found that they are black at the base
and reddish yellow near the tip. Wild mice, like all other ani-

Fic. 392. — Charles Darwin.

mals belonging to the class of mammals (including man), some-
times produce individuals without pigment in the skin, hair, and
even the eyes. Such individuals are called albinos, and the
peculiarity is designated as albinism. Albino or white mice with
pink eyes have this peculiarity, that when bred together they
produce only white mice. But when a white mouse is bred with
a house mouse, none of the offspring are white. However, when
the gray descendants of white and house mice are bred together,
one-fourth of their offspring will be white. This statement

THE MOUSE 429

holds true not only for the inheritance of the color of mice but
of most other animals. Indeed, many other characteristics
of both plants and animals are inherited in these same propor-
tions. The reason for this law is as follows: when the parents
differ greatly in that one has and the other lacks a character-
istic, the differences in the parents do not blend in the offspring,
but all of the offspring show the characteristic. This pres-
ence of a characteristic is said to be “dominant” over its
absence. The absence of the character — the recessive condi-
tion — is, however, not lost but exists in the reproductive cells
of the offspring; half of the reproductive cells possess the
characteristic and half lack it. Now if two individuals with
an equal number of germ cells of the dominant and the recessive
types are crossed, their germ cells meet in pairs, and it can be
shown that, in the long run, the following four combinations
of the two types are equally apt to occur. In the following
formula the letter d stands for the dominant condition, the
letter r for the recessive, the sign ¢ for the germ cells from
the male parent, and the sign ? for the germ cells from the
female parent.
$édedsderéreadsérer.

Whenever the combination contains the dominant character,
the body of the fully grown offspring will show only the domi-
nant character. It is easy to see that three-fourths of the
offspring will be dominant, and one-fourth recessive. The fore-
going law and its explanation were discovered forty years ago
by a monk, Gregor Mendel, in his monastery garden in Aus-
tria.'_ The law is important because it enables us to predict
what proportion of the grandchildren will show the domi-
nant character of their grandparents or its absence. Men-

1 Fig. 393.

430 ZOOLOGY

del’s law thus affords a sort of explanation of why a child
often resembles a grandparent rather than a parent. Fora
recessive condition that appears in only one grandparent
on each side cannot appear in the following generation, but
only in the grandchildren.

In addition to albinos breeders have obtained mice without
the black pigment in the hair; the result is a golden yellow.
By reducing the yellow at the
tips of the hair, the color be-
comes chocolate. When the red
and yellow are both absent from
the tips, a black race is produced.
In addition, some mice move in
circles, producing the race known
as waltzing mice.

Mice are of interest not only
on account of the evolution of the
fancy races, but also on account

of the rapidity with which they
as well as their allies, the rats,

Fic: 803) —Gievor Johann have spread over the world. The

Mendel. house mouse was originally lim-
ited in its distribution to Asia. It made its way into
Europe. By hiding in the cargoes of vessels, it has made
its way over the whole world. America originally had not
a single representative of the genus Mus to which rats
and mice belong. Both rats and mice were imported to
America by the early explorers. Of the rats the roof rat
seems to have been imported by the early Spanish discoverers
to the Southern States, where it still persists. It originated
in Egypt. The second was the black rat, believed to have

THE MOUSE 43

been imported to America about 1544. It has existed from
time immemorial in Europe; it has a mild disposition, and
from it the white rats we keep as pets have been derived.

The brown, or Norway, rat has been the latest importation.
The history of its migrations has been written. Probably
originating in central Asia, it crossed the Volga in great troops
in 1727, occupied Russia in 1730, France in 1750, and Denmark
about 1810. Before the advance of this powerful and aggres-
sive foe, the black rat of Europe gave way and became well-
nigh exterminated, although of late it is said to be reasserting
itself in Germany. The brown rat was introduced into Amer-
ica in 1775, has spread over the whole country, reaching the
Pacific coast about 1855 and, as in Europe, has nearly exter-
minated the black rat except in inland towns remote from rail-
roads.

The habits of rats and mice are well known. They inhabit
our buildings, gnaw our doors and furniture, destroy our pro-
visions, kill poultry, and aid in spreading disease. They shun
the light, living in holes during the day, run with great agility,
and are capable of making long leaps. Owing to their instinct
to go into holes, they are easily trapped by a funnel-shaped
opening leading into a closed box. Despite the ease of trapping
and their destruction by cats, they maintain themselves by
virtue of a great fecundity, for, if no deaths occur, more than
a hundred young may, in one year, descend from a single pair.

The food of mice is very varied. They naturally thrive
best on a vegetable diet ; oats especially are recommended for
tame mice, and hard-shelled nuts are useful because the mice
keep their teeth sharp by gnawing the sheils. If the teeth
are not kept worn off, they soon become inconveniently long,
owing to the fact that they grow continuously throughout

432 ZOOLOGY

life, and are not formed, once for all, like our teeth. In addition
to plant materials, rats and mice eat a certain amount of ani-
mal food.

Rats and mice belong to the class Mammalia! characterized
by having milk glands for the nourishment of the young.
Most mammals have also hair, although in the case of por-
poises and whales the hair is nearly or quite absent.

Fic. 394.— The rabbit. Lateral view of skeleton enclosed in outline of
body. From Parker and Haswell.

The structure of the mammalia may be illustrated by a
study of the rabbit.

General Form of the Body. — The body consists of head,
trunk, and tail, the latter in a rudimentary condition (Fig. 394).
The head is connected to the trunk by a relatively narrow neck
to insure mobility. Its large size results from the fact that it
bears the strong teeth, brain, sense organs, and their supporting
and protecting skull. Nearly the entire body is covered with
hairs which develop in the skin. At the base of each hair is
usually a gland that secretes an oily substance — sebaceous

1 From mammals, belonging to the breast.

THE MOUSE 433

gland. Along the under side of the body, best developed in
the female, are two rows of milk glands. Each milk gland
is an aggregation of sebaceous glands whose secretion is modi-
fied to furnish a nutritive fluid for the young mammal.

Two pairs of appendages are present, the hinder pair func-
tioning the more vigorously in locomotion. The entire hand or
foot does not lie flat on the ground as the sole of the human foot
does, but the wrist and heel are slightly elevated, while in the
horse the wrist and heel are elevated far from the ground, since
it stands on the tip of a single finger. In the rabbit the hand
has five digits, but the foot shows a reduction to four.

Skeleton. — The vertebral column of the rabbit, as of other
mammals, is divisible into five regions: (1) The neck, or
cervical vertebrze ; (2) the chest, or thoracic vertebre ; (3) the
waist, or lumbar vertebre ; (4) the pelvic, or sacral vertebre ;
(5) the tail, or caudal vertebra. Of the neck vertebrz there
are seven, as in all other mammals whether the neck is short,
as in the whale, or long, as in the giraffe; but the number of
the other vertebrae is variable. Each vertebra bears a spine
and processes for the attachment of muscles and ligaments.
The thoracic vertebre bear ribs. The anterior ribs abut
ventrally upon a long rod, the breastbone, or sternum. The
skull is heavier than that of the bird; the huge bone for the
lower jaw — the quadrate —is a part of the brain case or
cranium. A separate cheek-bone protects the eye cavity
below.

The shoulder girdle consists on each side of two bones, forming
a V, which embraces between its arms half of the thorax, and
the skeleton of the appendages is fastened to the apex of the V.
The dorsal arm of the V is the shoulder-blade (scapula) ; this

is broad, and has a high ridge for the attachment of the muscles
2F

454 ZOOLOGY

of the arm. The ventral arm of the V runs down to the sternum,
which affords it a firm support — this is the collar-bone. The
skeleton of the fore limb consists of the same parts as that of
man. They permit of a large amount of bending and rotation
of the appendages. The pelvic girdle forms a complete ring
surrounding the viscera of the posterior part of the abdomen.
It consists on each side of three pieces, fused into one in the
adult, which radiate from a centre as spokes from a hub, where
the skeleton of the leg impinges. One of these pieces passes
dorso-anteriorly and is fastened to the sacrum; it is called the
ileum ; the other two pass ventrally, each to unite with its fellow
of the opposite side in the mid-ventral line. Indeed, all four
bones are tied together here. The anterior pair of these bones
is called the pubis, the posterior pair the ischium — being the
bone which supports us when we sit. The rigidity and size
of the pelvis is necessary because it has to support the whole
body when the animal sits up on its hind legs. The skeleton
of the hind limbs of the rabbit differs little from that of man
except in having only four toes instead of five.

Organs and Function of Digestion. — The teeth show an
advance over those of reptiles in reduction of number, in
specialization of form, and in being each lodged in a special
socket. The number of dentitions has become reduced to two,
the milk teeth and the permanent teeth, in contrast to the croc-
odiles, where the dentitions are changed throughout life. In
the permanent dentition the front pair of teeth are called cut-
ting teeth, or incisors. In rabbits the two middle incisors of the
upper jaw continue to grow throughout life and, as the front
edge only has a thick layer of hard enamel, the teeth keep a
sharp, chisel-shaped edge very useful for cutting. The per-
sistent growth of the teeth keeps them from wearing off com-

TUE MOUSE 435

pletely as a result of persistent use in gnawing hard vegetable
fibre. The rabbit has no canine teeth, as in man and carniv-
orous animals, where they are used for tearing flesh; and an

Fic. 395. — Ventral view of skull of rabbit. Bones named are as follows:
p.max, premaxilla; pal.p.mazx, palatine process of premaxilla; mac,
maxilla; pal.mar, palatine plate of maxilla; pal, palatine bone; vo,
vomer; b.sph, basisphenoid; b.oc, basioccipital; s.oc, supraoccipital ;
zyg.max, zygotic process of maxilla; ju, jugular; ty.bul, tympanic bulla;
aud.me, external ear opening; par.oc, paroccipital process. From Par-
ker and Haswell.

empty space in the jaw is followed by a series of chewing teeth,

or molars (Fig. 395).

The food passes first into the mouth cavity, where, by the
help of the tongue, it is ground by the molars and at the same
time moistened and acted on chemically by the secretions of the

salivary glands. Then the food passes through a gullet to the

436 ZOOLOGY

stomach, where it is well churned and subjected to pepsin and
hydrochloric acid. Thence the food goes to the first part of the
small intestines (duodenum), where it is treated to the action
of the bile and the pancreatic juice. The food, now digested,
passes slowly down the long, small intestine, which is richly
supplied with lymph and blood-vessels, into which the food
passes to be carried away to the tissues. Further absorption
takes place in the large intestine, and finally the unabsorbed
remains collect in the rectum.

Organs of Circulation. — The circulation in general resembles
that of birds. The heart is divided into two separate halves,
each with its auricle and ventricle. The right auricle receives
a pair of large veins from the fore limbs and head and a single
vein coming from the posterior part of the body. The blood
thus collected in the right auricle passes to the right ventricle,
and thence is pumped to the right and left lungs. From the
lungs it returns to the left auricle, to be pumped by the left
ventricle into the aorta. The aorta gives off arteries to the
fore limbs and head, and then passes on the left (instead of the
right, as in birds) of the gullet to form the dorsal artery, which
supplies the hinder part of the body and the viscera. While the
blood from the tail, hind legs, germ glands, and kidneys goes
directly back to the heart, the blood from the food-canal flows
first to the liver to deliver its load of food there, and then passes
on to the right auricle.

Organs of Respiration. — The air that enters through the
nostrils crosses the back of the mouth and enters into the upper
part of the windpipe or larynx, through a slit that is guarded
from the entrance of food by a fold —the epiglottis. The
wall of the larynx contains certain large cartilages which sup-
port and control the vocal cords; these are represented in

THE MOUSE 437

man by the ‘“ Adam’s apple.” The wall of the windpipe
(trachea) contains small rings of cartilage which serve to sup-
port it and prevent its collapse on exhalation of the breath.
Below, the trachea divides into two tubes (bronchi), one of
which goes to each lung. Here it divides repeatedly, and
finally the smallest branches open into a thin-walled air vesi-
cle called a lobule of the lung. The wall of the lobule is cov-
ered with a network of blood capillaries, and here oxygen
passes from the air to the blood.

Organs of Excretion. — The kidneys are a pair of oval, bean-
shaped bodies lying close to the dorsal wall of the abdominal
cavity. As in the pigeon, the kidney is a mass of tubules each
associated with a capillary network where the waste products
pass from the blood to the cavity of the tubules, whence they
are collected in the central cavity of the kidney, and thence
conducted by the ureters to a single urinary bladder, which is
periodically emptied.

Organs of Reproduction. — The male and female germ glands
— testes and ovary — are small organs lying in young animals
in the dorsal part of the abdominal cavity. The products are
carried by special tubes to the exterior — the sperm ducts
and the oviducts. The eggs are of small size and not sur-
rounded with albuminous and limy covering, as in birds, nor is
there much food yolk. The reason for the difference is that,
whereas the eggs of birds, developing independently of the
mother, must be supplied with a protective covering and a
supply of food-stuff, the egg of the rabbit is not only fertilized
in but develops in the oviduct, is protected by the maternal
body, and is supplied with food from the maternal blood-
vessels. Only after the embryonic rabbit has become well
developed, has gained its coat of hair, and is almost ready to

438 ZOOLOGY

run about, is it expelled from the oviduct (born) to live its
separate existence.

Muscular System. — The muscles of mammals are developed
in close relation with the skeleton. On the head, besides a thin
sheet of skin muscles, the largest development is that of the
jaws. On the trunk is a general skin musculature and a pow-
erful dorsal musculature usec! in jumping. Then there is a
rudimentary set of muscles uniting the ribs, and a muscular

fb. hb.

i ii ithe NA Vay St sai
Fie. 396.— Brain of the rabbit seen from the right side: h.o, olfactory

lobe; fb, cerebrum; A.b, cerebellum and its median lobe, ¢)’; md,

medulla oblongata; p.c, the “pons” or bridge of transverse fibres; (—rv7,

cranial nerves. After Wiedersheim.
membrane (or diaphragm) completely dividing the body cavity
into an anterior and a posterior portion. Both the rib muscles
and diaphragm are used in breathing. The musculature of
the appendages is the most powerful, but so complex as to
be beyond the limits of such a book as this.

Nervous System. — The central nervous system consists,
as In the pigeon, of a brain and spinal cord. The chief advance
in the brain is shown by the enlarged cerebrum, showing traces
of the foldings of its surface which become more marked in the
higher mammals and are associated with intelligence.

THE MOUSE 439

Sense-organs. — In acldition to certain diffuse senses, such
as touch and heat and cold, the rabbit has complex organs of
taste and smell, hearing and sight. The organs of taste and
smell lie in the delicate lining of the mouth and nose—as small,
diffuse sense cells. The ear is essentially like that of man, and
differs from that of birds in the greater development of the
cochlea, which, in the rabbit, forms a close spiral of two and
one-half turns. The eye lacks the pecten, and is more nearly

fia. 397. — The duckhill, Ornithorhynchus anatinus. After Vogt and Specht.

spherical in shape. There are two eyelids; and the nictating
membrane, so prominent in birds, is rudimentary.

Mammals are divided into three main groups. The division
depends upon the condition in which the young are born.
The lowest group is called monotremes. The milk glands are
inalowstate of development, and eggs are laid in the shell, as
in reptiles and birds. There are two principal types, — the
“ Duckbill ” (Fig. 397), with aquatic habits, and the “ Spiny
Ant-eaters”’ (Echidna, Fig. 398), inhabiting rocky places.
Both types are confined to Australia and neighboring islands.

440 ZOOLOGY

In many ways this group seems to connect the mammalia with
reptiles.

The second group is known as Marsupalia, because the
mothers are provided with a marsupium,'! or pouch, in which
the young are carried. The young are born very imperfectly
developed. Immediately after birth they are placed in the

Fic. 398.— The spiny ant-eater, Echidna aculeata. After Vogt and Specht.

marsupium, where they become attached to the mammary
glands which lie within the pouch. In this situation the young
complete their development. All marsupials are confined to
Australia and adjacent islands, excepting the family of opos-
sums (Fig. 399), found only in the Americas. There is thus
a great discontinuity in the distribution of marsupials. This
is accounted for by the evidence that formerly the whole world
contained marsupials, so that those living to-day are the sepa-
rated remnants of that once universal race. The opossums are

1 marsupium, a pouch.

THE MOUSE 441

most numerous in the tropics, but the Virginian opossum
ranges north to New York.

The third division of the Mammalia includes all of its re-
maining orders. These orders will be briefly considered in the
following paragraphs.

The sloths and allies constitute a group that either have
no teeth or imperfect ones. Here are associated with the

Fic. 399.—The opossum, Didelphys virginiana. After Vogt and Specht.

sloths the hairy ant-eaters, armadillos, scaly ant-eaters, and
African ant-eaters. The three first-named families inhabit
South America; the two latter, Asia and Africa. Here
again, the discontinuity of the group indicates, what fossils
prove, that the Edentata! (as this group is named) have
been killed off from the connecting continents. The sloths
have cutting teeth, live in trees, and eat leaves (Fig. 400).

le, without ; dens, dentis, tooth.

442 ZOOLOGY

The armadillos are protected by strong plates developed in
the skin; they are chiefly nocturnal and omnivorous animals,
and burrow rapidly. The other three families feed on ants and

Fic. 400.— Two-toed sloth, Choleepus. After Vogt and Specht.

termites, usually lack complete teeth, and either live in trees
or burrow in the ground.

The whales and allies (Cetacea '!) have taken to an aquatic
life, for it is certain that their ancestors were land animals.
The sea-cows (manatees °), found in rivers in various parts of

1 cetus, whale. 2 From a native name.

THE MOUSE 443

the world, seem ! to show a transition to the marine forms, such
as the dolphins, the toothed whales (Fig. 401), and the tooth-
less or whalebone whales. The largest of these whales —
the Greenland whale — reaches an extreme length of twenty-
two to twenty-four metres, and a weight of over 100,000 kilo-
grammes. It is, indeed, the largest living animal. Although

whales in general are partly adapted to an aquatic life, they
still retain the essential mammalian qualities. They breathe
air which passes to the lungs and is expelled again through the

nostrils, which are placed high up on the head. The “ blow-
ing” of the whale is the forcible expiration of moisture-laden
air, which becomes visible by condensation, just as our own
breath does on a cold day. The young are necessarily born in
the water, but the breeding habits are poorly known. The
various Cetacea have diverse feeding habits. All are preda-
ceous. The toothed whales feed on larger animals, the whale-
tone whales on floating fish, crustaceans, medusz, and squids ;

1 The relation to Cetacea is not close.

444 ZOOLOGY

their whalebone is, indeed, merely a strainer to let the water
pass out of the mouth while the solid masses are retained.
The order of hoofed mammals includes a large number of
animals, almost all of which are closely related and have never
more than four functional toes, excepting in the allied groups of

Fig. 402.—Stone’s Alaskan black sheep. Photo. of a group in the Field
Columbian Museum.

elephants and certain small animals allied to the “ coney ” of
Scripture, where there are typically five. Of the true hoofed
mammals we distinguish the even-toed and the odd-toed, which
we may consider further.

The even-toed hoofed mammals include the hippopotamus
and other pigs and the peccaries, the camels and Hamas, the
deer, the giraffes, and the antelopes, sheep (Fig. 402), and oxen.

THE MOUSE 445

Excepting the pigs, most of these feed exclusively on plants.
The giraffes and antelopes are characteristic of Africa; but
the “mountain goat” of our highest ranges may be placed
with the antelopes, as may also the chamois of Europe. The
prong-horn of our southwestern plains is remarkable in having
hollow horns like the antelopes, which are, however, shed like
those of the deer.

The odd-toed hoofed mammals include the horses, tapirs,
and rhinoceroses. The horses are remarkable in that they
all the other
digits being rudimentary or absent. While fossil remains of
horses are found in all continents, the living species have come

stand upon the toenail of the middle digit

from Asia and Africa. The African species are striped (zebras).
The tapirs are found living to-day only in South America
and southeastern Asia. They frequent the depths of forests
near watercourses, and feed on leaves and shoots of shrubbery.
The rhinoceroses of Africa, of India, of Java, and of the Malay
Archipelago, are quite distinct. All are large, stupid, and fero-
cious when attacked, feed on herbage, and wallow in pools.

The elephants are distinguished by their long trunks, great
incisors (tusks), and huge, complex grinding teeth. The
Indian and African types are quite distinct. Elephants are
intelligent, tractable, and capable of doing much work for
man. Their diet is vegetable, consisting especially of the
leaves and young branches of forest trees, which they gather
with their proboscis.

The moles and shrews are small mammals and chiefly ter-
restrial. One of our common families includes the moles which
burrow in the ground, have smail eyes and broad, shovel-
shaped fore feet, used for digging their tunnels. They feed
chiefly on earthworms. The other common family is that of

446 ZOOLOGY

the shrews, which are mouse-like, live chiefly on the surface
and in the woods, and feed on insects and small crustaceans.

The flesh-eaters (Carnivora ') include both land and marine
forms. To the first group (Fig. 403) belong the cats (including
tigers, lions, leopards, lynx, etc.); the civet-cats, mongoose,
etc.; the hyenas; the dogs (including jackals, wolves, and
foxes); the bears; the raccoons; and the great fur-bearers, —

Fria. 403. — The cheetah, or hunting leopard, Felis jubata. Photo. of a
group in the Field Columbian Museum.

martens, minks, weasels, badgers and otters, and skunks.
Marine Carnivora comprise the seals (Fig. 404), walruses,
and sea-lions, the more valuable of which are disappearing
as a result of man’s lack of foresight. Altogether, the Car-
nivora comprise the most agile, the most intelligent, the most
dreadful, and some of the commercially most important of
fellow-animals.

The gnawing mammals include our types, the mouse and the
rabbit, and also the squirrels and marmots, beavers, jumping
mice and gophers, and poreupines. The order contains no

learo, carnis, flesh; vorare, to devour.

THE MOUSE 447

very large animals, as befits a group of burrowers— true con-
tact lovers. The typical squirrels are, however, arboreal, and
run over trees and from tree to tree; nevertheless, even they,
by preference, make their nests in holes of trees. Our common-
est squirrels are the gray, the little red, the striped or chip-
munks, and the spermophiles of the Western States. On the
whole, excepting perhaps the red squirrel, they are useful ani-
mals and deserve to be protected rather than slaughtered.
It is shameful to see grown men shoot the harmless and com-

Fic. 404. — The harbor seal, Phoca vitulina. From Parker and Haswell,
““Manual of Zoology.”
one of the friendliest of the wild
animals. Closely related to the squirrel are the prairie dogs
and woodchucks, of which the former make extensive villages
in the Great Plains regions, and the latter lives in solitary
burrows throughout our northeastern States. The beavers
are now almost exterminated. They were the leading engi-
neers among animals, building dams across streams in order to
make deep ponds for their protection. Near the middle of the
pond a great house of mud and sticks was reared; the inner
chamber lay above the level of the pond, but the entrance to it
was under water. The pocket gophers (Fig. 405) are invet-

panionable gray squirrel

448 ZOOLOGY

erate tunnellers; their cheek pouches enable them to carry an
extra supply of seeds and vegetables. The porcupine of our

Fic. 405. -— Geomys tuza, the Georgia gopher. One-half nat. size. After
V. Bailey.

northern country is remarkable for its modified hairs, which

form spines, many of which are hollow quills. These are for-

midable organs of defence. Finally, the hares and rabbits are

characterized by their great ears, short tails, and swift flight ;

Fie. 406. — An insectivorous bat, Synotus. After Vogt and Specht.

in these respects the hares have developed further than the
rabbits.

The bats (Fig. 406) are extraordinarily modified mammals

THE MOUSE 449

which, like the birds, seem to have penetrated into the air to
prey on the flying insects. Not all bats are insectivorous,
however, for certain Old-world bats feed on fruits. Our
commonest species are the little brown bats (with a nearly

Fig. 407. — Simia satyrus, the orang-utan, in breadfruit tree. From a
photograph of a group in the Field Columbian Museum.
furless wing), and the red bats (with patches of fur on the wing
membrane).
The Primates! are of interest because we ourselves are
placed in this category, together with certain other animals
that have attained a less lofty station. The lowest Primates

1 primus, the first.

2G

450 ZOOLOGY

are the lemurs, found chiefly in Madagascar. These have an
arboreal habit, and feed on fruits, leaves, and small birds and
insects. Next higher come the American marmosets, the
howling monkeys, and the flat-nosed, prehensile-tailed Amer-
ican apes; still higher are the small-nosed, nonprehensile-
tailed apes, including the baboons, mandrills, and macaques.
Finally, come the tailless, manlike apes, found exclusively in
the Old World —the gibbons, orangs (Fig. 407), chimpanzee,
and the gorilla. The two latter are nearest to man, but one
cannot say which is the nearer. For, while the chimpanzee
approaches man more closely in facial appearance and in
intelligence, the gorilla is more manlike in the size and com-
plexity of the brain and in its habit of walking on the ground.
There is no reason to doubt that man’s species came off from
the anthropoid apes; the discovery in Java of a fossil form
(Pithecanthropus erectus) intermediate between man and the
manlike apes is a strong additional piece of evidence.
This differentiation of man’s species probably began in late
Tertiary times.

CHAPTER XXVII

THE DEVELOPMENT OF THE FROG’S EGG

ALL living matter has the capacity of increasing itself under
proper conditions to an almost unlimited extent, the food which
animals devour being the material out of which the new living
substance is made. This living substance exists in isolated
particles, or masses, which we call individual animals or plants.
The animal or plant has also at any stage a definite form which
is not exactly alike in any two individuals, but is roughly alike
within the “ species.”” Now the number of individuals of any
species ' tends constantly to diminish through death. It is
actually maintained by reproduction, by a piece of the parent
individual being cut off to form a new individual. This piece
may be at first almost shapeless or approximately spherical.
But as it grows larger it assumes more and more the form and
complex structure of the adult. This process of growing into
the adult form is development. In most of the more familiar
cases development begins with an approximately spherical egg.

In the case of the frog, the egg is between one and two mil-
limetres in diameter. The eggs, which are numerous, are laid
in a common jelly, and during development float near the sur-
face of the water in which they are laid. The first visible
changes are furrows running across the surface of the egg, as
a result of which the egg becomes divided into small areas
which correspond to a division of the whole egg into “ cells.”
This stage of development is called cleavage.2 Toward the end

1 See also Chapter XVIII. 2 Wig, 408 A-F,
451

452 ZOOLOGY

of the cleavage stage the white or volk side of the egg becomes
enveloped by the black dividing cells, excepting for a small
white plug edged by a sharp groove. This is where cells have

G H |

Fic. 408. — Cleavage of frog’s egg, A-G; H, beginning of gastrulation;
I, the white plug. From Morgan, ‘‘ Development of the Frog’s Egg.”

THE DEVELOPMENT OF THE FROGS EGG 455

rolled in to form the beginnings of the food canal (Fig. 407 H).
Next, on the future dorsal side of the embryo, two ridges arise
with a furrow between them; they are the beginnings of the
brain and spinal cord (Fig. 409). When the furrow is closed
by the ridges folding over it, the central nerve tube is formed
and begins to sink into the body. Later the trunk elongates,
nerves and muscles are formed, gills sprout out, and the tad-
pole is formed (Fig. 410).

Fic. 409. — Two stages in the development of the frog while the brain and
spinal cord are arising. From Morgan, ‘Development of the Frog’s
Egg.”

Effect of Heat and Light on Development. — Eggs devel-
oping in normal environments in nature arrive at nearly the
same end-result, even when the environments are not identical.
We gain, in consequence, an impression that development
proceeds unaffected by any changes in the outside world.
But thisis not true. For one thing, the rate at which the devel-
opment of frogs’ eggs proceeds depends closely upon the tem-
perature of the water. They develop most rapidly at about
30-32° C. If the temperature is elevated above this point,
the rate of development is retarded, and finally ceases at about
40° C. So, likewise, as the temperature is lowered, the devel-
opment is retarded, until at the temperature of freezing water

454 ZOOLOGY

it ceases (Fig. 411). If the temperature is too high, develop-
ment may be abnormal, so that a monstrosity is produced.

Light has a less striking effect on the development of the
frog. If light is excluded from the developing eggs, they will
develop more slowly. The acceleration of development by
rather high temperature and by daylight is probably due
to a chemical effect of these agents. It indicates that devel-
opment is a complex chemical process.

Healing and Regeneration. — If the egg of a frog be pricked
slightly, there will be a loss of substance, and the resulting

Bese en oO BE Pe es

Fic. 410. — Young tadpole of the frog. From Morgan, ‘Development
of the Frog's Egg.”

embryo will be at first abnormal. Later, however, this abnor-
mality will become smoothed over by appropriate develop-
ment. So, also, if the tail of the developing larva is mutilated,
the wound will heal and the missing parts will be re-formed.
This capacity of the living organism to restore the normal
form after mutilation is seen also inman. For if some of the
skin be cut away, or even if parts of internal organs are removed
the wounds will not merely heal, but the lost part will regen-
erate. The remarkable thing is that in regeneration almost
exactly that is produced which was lost. Both regeneration
and healing in the adult are a survival of the same capacity for
development which we see in the egg.

THE DEVELOPMENT OF TUE FROGS EGG 455

Postembryonic Development of the Frog. — After reaching
a certain stage of development, the embryo frog, called tadpole,

MEAN. FEMPERATURE

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Fie. 411. — A chart showing the correlation between the stage of develop-
ment of the frog on successive days and the temperature at which it has
developed. From Higgenbottom.

begins to develop legs. The hind legs first appear, afterward
the fore legs sprout out, and finally the tail begins to wither
away, until the form of the four-legged tailless frog (anuran)
is fully developed. In the leopard frog, as in the toad, this

456 ZOOLOGY

change of form (metamorphosis) is completed during the first
summer, but in case of the bullfrog and green frog the tadpole
passes through the winter in the immature state, and does not
complete its metamorphosis until the second summer. Conse-
quently, it is not uncommon to find quantities of large tadpoles
in ponds at the time the ice breaks up in the spring.

Since Amblystoma and Necturus do not lose their tails,
the metamorphosis which they undergo is less profound than
that of the frog. In Amblystoma, as stated in Chapter XVII.,
the gills and the fin on the tail of the tadpole are lost in the
metamorphosis. Necturus, on the contrary, retains gills and
tail-fin, so that its acquisition of legs is almost the sole indi-
cation of metamorphcsis.

General Laws of Development.— Development consists
of an unfolding of potentialities wrapped up in the germ; an
awakening in orderly succession of processes lying dormant
there. But the causes which control development, the causes
which determine when this process and that shall awaken, are
still too obscure for us to attempt to picture them in detail.
This much is certain, that the causes of development from the
egg are the same as those of budding of leaves on a tree, the
regeneration of the parts of a Hydra, or the healing of a cut in
our skin. In the case of most of the higher plants and animals,
the ripe egg will not develop until it is “ fertilized,” that is,
until a gerra from another individual has fused with the ripe
egg. But the ripe egg of many of the lower plants and animals
requires no fertilization for development, and the meaning of
the fertilization process is quite obscure.

The developing eggs of all the higher animals pass through
much the same sort of early stages. The egg “ cleaves ” into
a number of cleavage spheres, each of which is destined to give

THE DEVELOPMENT OF THE FROGS EGG 457

rise to a particular part of the organism. By repeated division,
a mass of small cells, constituting the morula stage, is formed.
Usually a cavity arises in the middle of the morula, and into this
some of the surface cells are pushed to form an internal sac —
the food canal. This is necessarily an early step, as all food
is taken into the interior of the body. The process by which
external cells are pushed in is known as gastrulation. Very
early the body is seen to be composed mostly of layers, or
membranes and cavities. It is by the folding and union
and breaking through of these membranes that most of the
organs of the adult arise. Development of the individual is,
on the whole, accompanied by increase in complexity. The
evolution of animals in the animal kingdom is likewise, on the
whole, accompanied by increase in complexity of organization.
Thus both the embryonic development of the individual and
the evolution of the species proceed from simple to complex,
and since they start from about the same point and reach the
same goal, we are not surprised to find that the individual de-
velopment of any species often goes through stages markedly
like the stages in the evolution of the species. The parallelism
of development and evolution was early noticed, and is often
called ‘Von Baer’s law,” after a naturalist who lived in the
middle of the nineteenth century and very clearly formulated
this parallelism.

CHAPTER XXVIII
A BRIEF HISTORY OF THE SCIENCE OF ZOOLOGY

A SCIENCE is the recorded body of facts and general ideas on
some subject-matter, especially after they have been arranged
under general laws. Zoology as a science, therefore, had its
beginning when a man wrote out for public use some observa-
tions he had made on animals, while unwritten observations
constitute personal knowledge or at best “ folklore.” The
development of the science is traced by books, by special re-
ports, and by the proceedings of scientific societies, which
have appeared in ever increasing volume since the invention
of printing.

Who first definitely recorded observations on animals it
would be hard to say. Nascent man evolved in the company
of other animals, and the dog was doubtless one of his earliest
companions. Primitive language, in so far as it contains the
names of animals, gives the first record of his observations, and
these names show his appreciation of the fact that there are
different kinds of animals. Later arise the oral traditions or
folklore, with their animal stories, fables, superstitions con-
nected with animals, and even a mass of fairly accurate obser-
vation. As time goes on, observation is sharpened, language
is enriched with a constantly increasing number of names of
animals and, eventually, as students and philosophers appear,
critical studies are made on animals. Such studies, we find,
were first made by the Greeks. While there were not lacking

458

BRIEF HISTORY OF THE SCIENCE OF ZOOLOGY 459

those who thought about and even dissected animals as early
as the sixth century before Christ, yet so relatively vast were
the observations and records make by Aristotle (334-322 B.c.)
that he is commonly accepted as the father of zoology. Living
near the mild waters of the Mediterranean Sea, which swarm
with living beings, he was led to make studies on marine as
well as terrestrial organisms. He made observations on snails,
muscles, hermit crabs, sea-urchins, tunicates, and sea-anemones.
His studies on nesting habits,
care of young, and general eco-
nomics of bees and wasps are
extensive and valuable. While
his observations lacked the
thoroughness which is expected
in modern zoological work, and
his generalizations seem crude
in view of established facts, yet
we can only admire his ideal of

making independent observa-
: : x : Fie. 412.— Aristotle. From Locy,
tions and his aim of finding a “Biology and its Makers,” New
general law in nature, the law York, Henry Holt and Company.
of fitness or “ adaptation.” He clearly saw also the principles
of division of labor, and that the process of development in an
organism is a progress from the simple and general to the
complex and special. If Aristotle did not enter to any im-
portant extent into the speculations of the Greeks as to the
origin and evolution of the universe, it is clear that he conceived
a progressive development of the animal kingdom out of the
simplest beings.

After Aristotle there was a decline in the intellectual life of
Greece, and with the spread of Roman influence and ideas in

460 ZOOLOGY

which politics and the social organization dominated, science
slumbered. The intellectual centre was transferred to Alex-
andria and here medicine, with its stimulus to careful stuclies
in human anatomy and physiology, flourished. The most
famous of the anatomists who studied at Alexandria was Galen
(second century of our era), who

made numerous dissections on man,
monkeys, ruminants, rats, and even
many kinds of birds, snakes, and fish
His anatomy was for eleven or twelve
centuries the most esteemed work on
the subject, being by some apparently
regarded as more reliable than nature
itself. During the Middle Ages of
Europe, the age of constant strife,
central and northern Europe gradually

Fi CS | acquired the culture of thesouth. At
Se CALENVS,

°) this time all science languished, but
Be 2399 dst’ ae : : = :
with the Renaissance, whose opening
Fic. 413.— Galen. From

Locy, “Biology and its May be put at the discovery of
Makers,” New York, America, we note the first stirrings of
Henry Helt and Company.
areturn to nature. The epoch from
1500 to the present time may be divided into four periods, as
follows: the Encyclopedic period, 1500 to 1650; the System-
atic period, 1650 to 1800; the Morphological period, 1800 to
1890; the Dynamic period, 1890 to the present.
The eneyclop:edic period is opened by Gesner (born in Zu-

rich, 1516), who had the aim of collecting all facts concerning
animals, of examining them critically, and of writing a compen-
dium that would show the position of the science and obviate
the necessity of consulting the older authors. His book was

BRIEF HISTORY OF THE SCIENCE OF ZOOLOGY 461

the great zoological text-book of
the new era, as Pliny’s was of
the Roman era. Gesner’s text-
book appeared between 1551 and
1558 in four huge quarto volumes
bound in parchment. He never
completed this work, which is
not strange, since he busied him-
self with many other great un-

dertakings. He was the first to
establish a museum and a botani-

Fie. 414. — Gesner. From Locy,

cal garden. _Gesner’s work was — “Biology and its Makers,” New
imitated and extended some York, Henry Holt and Company.
years later by Aldrovandi (b. 1522 in Bologna, d. 1605).
Such works, which had many successors, characterized the

Fie. 415. — Andreas Vesalius.
From Foster, ‘‘Lectures on the
History of Physiology,”’ by per-
mission,

encyclopedic period.

But the encyclopedic period
was one of original scientific in-
vestigation as well as of codifica-
tion. The bonds of authority
which held naturalists to the
writings of Aristotle and Galen
were at last broken by Vesalius
(b. 1512, d. 1564). Born into a
noted family of physicians, Vesa-
lius early showed a strong taste
for anatomy, and was well edu-
cated at different universities.
He applied himself to careful per-
sonal dissections of the human
body, and in 1543 published his

462 ZOOLOGY

d

memorable work, ‘‘ Structure of the Human Body.” This great
work in anatomy created a revolution in the science, and
scholars flocked to him at Bologna, Pisa, and Louvain. From
among these arose nearly all the prominent anatomists of the
latter part of the sixteenth century, many of whom extended
their anatomical studies to the lower animals. Indeed, the
scientific activity
started by Vesalius
has continued un-
broken to the present
time, and has re-
sulted in the zoologi-
cal sub-sciences of
comparative an-
atomy and physi-
ology.

In consequence of
the construction of
encyclopedic works
on zoology, a search

Fic. 416. — John Ray. From Ray Society was made for new
pe species in order to
make the books as complete as possible. New countries were
visited for the purpose of collecting new animals, the seashore
and ponds were fished, and even the new world opened by the
compound microscope at the beginning of the seventeenth cen-
tury was utilized. The increase of species made necessary the
invention of names for them. Gradually the necessity of recog-
nizing subdivisions of the primitive groups of quadrupeds,
birds, etc., became apparent, and this necessity led to the sys-
tematic period. This period is opened by the English natural-

BRIEF HISTORY OF THE SCIENCE OF ZOOLOGY 463

ist, John Ray. He saw the importance of recognizing in ani-
mals categories of successively diminishing rank in the various
classes of the animal kingdom. But it was left to Linnzeus
(b. in Sweden 1707, d. 1778) to perfect the system by estab-
lishing categories. The animal kingdom was divided by him
into classes, the classes into orders, each order into genera, and
each genus into species. He in-
vented the binomial nomencla-
ture that is still in use for both
plants and animals. The first
name is a sort of surname and
indicates the genus; the second
name gives the particular species.
Thus, Felts catus is the particular
name of the cat, Felis leo of the
lion, Felis tigris of the tiger, and
so on. Finally, Linneus intro-

duced the method of brief de-
scription of the characteristic Fic. 417.— Marcellus Malpighi.
x x From Locy, ‘Biology and its
points of each group in place of — yyakers,” New York, Henry Holt
the wordy, ill-ordered descrip- and Company.
tions of his predecessors. The brilliancy of Linnzeus’s work
attracted many investigators, and the interest in collecting and
classifying species remains to this day. Such work, although
often fascinating, is not the highest type of scientific work.
The foundations of modern morphological or anatomical
zoology were laid in part by men whose original interest was
medical and in part by a new school of naturalists who studied
the structure and behavior of the lower animals. As early as
the middle of the seventeenth century we find Malpighi, pro-
fessor of medicine at Bologna, publishing his investigations

464 ZOOLOGY

upon the internal anatomy of the silk-moth, which afforded
not only an extended but also the first insight into insect
anatomy. The Dutchman Swammerdam (b. 1637, d. 1680)
made even wider studies in the same field. His observations
were published in a book entitled “ Bible of Nature.”

The newly discovered and

gradually much improved com-
pound microscope lured many to
J) | a study of the structure and be-
| havior of microscopic species
and permitted the beginning of
new sciences dealing with the
tissues of organs (histology) and
with the cell (cytology). The
first to employ the compound
microscope to serious work in
zoology were the Italian Mal-
pighi and the Dutchman
Leeuwenhoek. The work of

Fie. 417 a. —Swammerdam. ered '
From Loey, “Biology and its Malpighi upon insects has al-
Makers,’ New York, Henry

Fini sake Compares ready been referred to. Not less

important are his histological
studies on higher animals. He first saw and described the
circulation of the capillaries, observing it in the lung of the frog.
He first gave a detailed account of the series of stages in the
development of the chick, and was thus one of the founders of
embryology. He studied thoroughly the structure of various
tissues of the higher animals, and may be said to be the founder
of histology.
Unlike Malpighi, who used the microscope as an incidental
aid to his researches, Leeuwenhoek used the microscope to study

BRIEF HISTORY OF THE SCIENVE OF ZOOLOGY 465

small things just because they were small. He first saw the red
corpuscles, the cross striations of muscle fibres, the tubules in
teeth, the dry cells of the outer skin. He first studied under
the microscope numerous small animals, such as fleas, flies,
various small beetles, and the compound eyes of insects. He
discovered the parthenogenesis of the plant lice and the bud-
ding of Hydra. Also he dis-
covered the rotifers and various
Protozoa. It is rare that an
opportunity arises to study, by
the aid of a new invention, a
wholly new world of organ-
isms without leaving home,
and Leeuwenhoek took full
advantage of his unique
opportunity.

The end of the seventeenth
and the beginning of the eigh-
teenth century was a period of

: m ‘ rae i Fic. 418. — Leeuwenhoek. From
immense scientific activity in Locy, ‘Biology and its Makers,”

many directions. Numerous New York, Henry Holt and
Company.

learned societies or academies

were started in England, Germany, France, Italy, Austria, and
Russia, and their publications served as repositories for the
new discoveries. In consequence of the great collections of
animals and plants that were being made, museums were
founded, frequently by the academies, to care for them and
to encourage further collecting. Zoological gardens were es-
tablished to keep alive the new and strange animals that ex-
plorers brought back from newly discovered lands. All of

these things must have stimulated the love of nature innate
24H

466 ZOOLOGY

in normal young people, and were responsible for the creation
of many zoological investigators.

As the eighteenth century drew to a close, a more philo-
sophical tendency appeared in zoology — particularly in the
French school. Buffon (1707-1788) began a great popular

encyclopedic work on the nat-

= ural history of animals, but it
was never completed by him.
The work was finished by other
hands. It is, however, on his
theoretical opinions, particularly
his recognition of the evolution
of species, and his protest
against Linneus’s view of im-
mutability, that Buffon’s great-
est claim to recognition rests.
But it is Lamarck (1744-1829)
who has made most famous this

French school of philosophical

Fie. 419.— Lamarck. From
“Lamarek, his Life and his
Work,” by permission of the are not immutable, but alter
publishers, Messrs. Longmans,
Green, and Company.

zoologists. He held that species

under changing environment,
and that there has been an up-
ward progression in the animal kingdom. He argued that
changes in environment bring about changes in habits, and that
new habits involve the use of new parts, resulting in modifying
them. Such modifications are inherited, and thus are perpet-
uated as new specific characters. Rudimentary structures like
the eyes of moles or cave animals result from this use. Webbed
fect of birds, on the other hand, result from stretching the web
by extending the toes to swim more effectively. The neck of

BRIEF HISTORY OF THE SCIENCE OF ZOOLOGY 467

the giraffe became elongated from the constant effort to reach
the foliage higher up on the trees. Use and disuse, effort and
habit, lie at the basis of Lamarck’s theory of progressive evolu-
tion.

The French school contributed not only to general theory
but also to the solid facts of zoology. Lamarck described hun-
dreds of new species of invert-
ebrates, and proposed a sub-
division of invertebrates which
was amarked advance over any-
thing that had hitherto existed.
In fact the division of animals
into Vertebrata and Inverte-
brata was Lamarck’s own sug-
gestion. But the fame of
Lamarck as a student and de-
scriber of animals was over-
shadowed by his colleague and
opponent, Cuvier (1769-1832).
As the greatest comparative

3 < Fie. 420.— George Cuvier. From
anatomist of his age, he at- ~ Tocy, “Biology and its Makers,”

tracted to Paris many pupils. New York, Henry Holt and Com-
pany.

His anatomical studies em-
braced ccelenterates, mollusks, arthropods, and vertebrates,
and he recognized that fossil forms belong as truly to the do-
minion of zoology as do those that have not been so long dead.
In his two great comprehensive works, “‘ The Animal IXtingdom
classified on the Basis of Organization’ and ‘‘ Lessons in Com-
parative Anatomy,” he introduced for the first time internal
as well as external anatomy as the proper basis for classification.
He also established the theory of distinct types of animal struc-

468 ZOOLOGY

ture which were independent and parallel and did not all fall
into one series leading from Protozoa to man. Cuvier opposed
the theory of evolution, and so great was his influence in France
that the ideas of Lamarck were neglected and almost forgotten
in the supremacy of the view of the immutability of species.

The science of embryology had its beginnings in Aristotle’s
studies on the hen’s egg, and in the revival of biological studies in
the seventeenth century there were not wanting those who, like
Malpighi, made some superficial studies on developing chicks;
but it was not until the middle of the eighteenth century that
serious embryological studies were made. At this time there
was raging a discussion as to thenature of development. On
the one hand it was maintained that in the egg lay the embryo
as we see it when the chick is hatched, only it is of very small
size. Development consists in the growing of the different
parts until they become visible. On the other hand, it was
asserted that the sperm-cell contains the young creature and
that it finds in the egg food for growth. One day a teacher in
Germany remarked to a brilliant pupil, Caspar Friedrich Wolff;
that many things of value would be got from a careful study
of the development of the hen’s egg. Wolff set to work and
succeeded in proving that the egg is at first without the organs
of the adult, and that these are gradually formed in it. These
conclusions, based on careful study, were combated by Haller,
the eminent physiologist, and on account of his great authority
he crushed, for a time, the truth; but at the beginning of the
nineteenth century new studies were made by Carl Ernst von
Baer, who confirmed Wolff’s observations, and in 1832 estab-
lished embryology as a separate science. During the re-
mainder of the century embryology almost overshadowed the
other sub-sciences of zoology. In England were Huxley and

BRIEF HISTORY OF THE SCIENCE OF ZOOLOGY 469

Balfour and their numerous pupils. In Germany, Russia,
and France the workers were even more abundant, and
America includes as its share the work of Agassiz and of men
still active.

Cytology. — When thin sections of plant tissues were first
looked at with a microscope, they were seen to be made up of
spaces surrounded by thick walls, and these were called “ cells.”
Similar cells were seen in animal tissues also. But it was not
until 1838-1839 that the botanist Schleiden and the zoologist
Schwann raised these isolated facts to a theory by declaring
that the whole body of organisms is made up of such cells and
their products. It was, however, left to Schultze to bring out
the more fundamental idea that the body is made up of a living
substance — protoplasm — which is divided for physiological
purposes into more elementary parts called cells. Later it was
discovered that the activity of each cell is controlled by a central
body, or nucleus, and for the last three or four decades the
behavior of the nucleus in cell division and in heredity has
been the object of extensive investigation.

The Evolution Theory. — We have seen how the Greeks
regarded the evolution of the organic world as a part of cosmic
philosophy. Through a narrow interpretation of the Mosaic
account of creation, the Christian church was led away from
those broad views, and in this attitude it was supported by Lin-
neeus and others. We have seen that a French school of evolu-
tion arose, but its explanation of the method of evolution was
not acceptable, and the school was crushed by the authority of
Cuvier. In England there were not wanting those who accepted
or promulgated the theory with a very slight basis of fact.
It was the great service of Charles Darwin to offer such a
theory, accompanied by proofs so numerous and presented in a

470 ZOOLOGY

fashion so judicial as to win acceptance by all. Charles Dar-
win was born in Shrewsbury, England, in 1809; his uncle,
Erasmus Darwin, had written a theory of evolution in metric
form. After having studied in Edinburgh and Cambridge,
Charles Darwin, at the age of 22, accompanied the ship

Beagle on a five years’ scientific
expedition around the world.
On this trip he made studies on
the distribution of animals in
space and time, and published
a fascinating book on them.
These studies led him, on his
return, to collect facts which
might bear on the origin of
species. In 1859 Darwin pub-
lished his book entitled ‘ The
Origin of Species through Nat-
ural Selection.” Besides the

ies, sets = tageneae Wes: general argument for evolution,
he proposes the special hypothe-

sis of selection to account for it. In every species many
more individuals are produced in each generation than
can survive. In this weeding-out process those individuals
that in any way peculiarly fit the conditions of life will
be more apt to survive than the less fit; thus the fact of
adaptation is accounted for, and, whenever the environment
changes, a change in the species tends to occur. Darwin was
inclined to believe that the changes in successive generations
would be always slight, but the experiments and observations
of the Dutchman De Vries (‘The Mutation Theory ”’ 1901-
1903) make it seem probable that the progressive steps are

BRIEF HISTORY OF THE SCIENCE OF ZOOLOGY 471

usually new characters which breed true from their start.
We find ourselves thus in the twentieth century with the
theory of evolution generally accepted, but with the method
of evolution incompletely worked out. There thus remains
plenty of work on this theory to be done in the future.

Zoological expeditions. — We have seen that the work of the
encyclopzedists led men to add to the number of known species
by exploring new countries. The great systematic works of
Linneus and the others had a similar effect. One of the
greatest of the early expeditions was undertaken by Pallas
(b. at Berlin 1741, d. 1811), who travelled through Siberia
and as far south as the Caspian Sea. He also investigated the
fauna of eastern and southern Russia in Europe, and published
the results of his studies in extensive books.

During the early part of the nineteenth century a great
interest was revived in the study of marine animals, and
many expeditions were sent around the world. Of these the
Challenger Expedition is the most noteworthy. Its results
are published in fifty fine quarto volumes. In this country
the expedition under Wilkes, which opened Japan to Western
civilization, and those of Alexander Agassiz in the Blake
and the Albatross are the most noteworthy. Despite all of
this activity, much of the land and of the sea remains to be
explored.

APPENDIX I

A LIST OF BOOKS DEALING CHIEFLY WITH
ECOLOGICAL AND SYSTEMATIC ZOOLOGY
OF AMERICAN ANIMALS

A. GENERAL SYNOPTIC WORKS:

Leunis, J.— Synopsis der Thierkunde. Dritte Auflage von H.
Ludwig. 2Bande. Hannover. 1883-86.
This is the nearest approach to a systematic manual, taking the place
in Zoology which Gray’s and Coulter’s Manuals do in Botany. It deals
chiefly with European species, and has not been translated.

Thomson, J. A. — Outlines of Zoology. 3d edition, with 332 illus-
trations. New York: D. Appleton & Co. 1899. 819 pp.

An excellent condensed compendium; in which, however, the struc-
tural side predominates.

Riverside [formerly Standard] Natural History, edited by J. S. Kings-
ley. 6 vols., large Svo. Boston and New York: Houghton,
Mifflin & Co. Price $30.

The most important large compendium written by American authors,
somewhat after the plan of Brehm’s Thierleben.

Cambridge Natural History, edited by S. F. Harmer and A. E.
Shipley. New York: The Macmillan Company. 1894-1908.

An English work of surpassing merit.

Klassen und Ordnungen des Thierreiches, edited (originally) by
Bronn. Leipzig u. Heidelberg: C. F. Winter.

An extensive and thorough work. Although the whole work is not
yet completed, some of the volumes are out of date. The most recent
and important are the volumes on Protozoa, Porifera, Coelenterata,
Vermes, Echinodermata, Crustacea, Mollusca, Reptilia, and Birds.

473,

474 APPENDIX

Das Tierreich. Eine Zusammenstellung und Kennzeichnung der
rezenten Tierformen. General redacteur: F. E. Schulze.
Berlin; R. Friedlander und Sohn. 1896—

A systematic account of every known species, with keys for their
determination. An ambitious enterprise which will hardly be finished
during one generation.

B. WORKS RELATING TO ANIMALS OF A
PARTICULAR HABITAT

Verrill, A. E. (and S. I. Smith). — Report upon the Invertebrate
Animals of Vineyard Sound and the Adjacent Waters, in Report
(of U. S. Fish Commission) on the Condition of the Sea Fisheries
of the South Coast of New England in 1871 and 1872. (1873.)
pp. 295-778.
An indispensable accompaniment of the zoologist at the Eastern sea-
shore; separate copies can be purchased of dealers in scientific books.
Emerton, J. H. — Life on the Seashore. [For sale by Bradlee Whid-
den, Boston.]
Mayer, A. G. — Seashore Life. New York Zoological Society.

C. GENERAL WORKS ON HABITS, ECOLOGY, AND

DISTRIBUTION
Verworn, M. — General Physiology. An Outline of the Science of

Life. New York: The Macmillan Company. 1899. 615 pp.
Price $4.00.

Morgan, C. L. — Animal Life and Intelligence. New York: Ed-
ward Arnold. 1891. 503 pp.

Morgan, C. L. — Habit and Instinet. New York: Edward Arnold.
1896. 351 pp.

The two best books on the topics considered.

Lubbock, J. — On the Senses, Instinct, and Intelligence of Animals,
with special reference to Insects. International Scientific
Series, Vol. LXIV. New York: D. Appleton & Co. 1888.

APPENDIX 475

Poulton, E. B. — The Colors of Animals. The International Scien-
tific Series, Vel. LXVII. New York: D. Appleton & Co. 1890.

Semper, K. — Animal Life as affected hy the Natural Conditions of
existence. International Scientific Series, XXX. New York:
D. Appleton & Co. 1881.

Even to-day the best book on Animal Ecology.

Wallace, A. R.— Tropical Nature. London and New York:
Maemillan & Co. 1895.

Wallace, A. R. — Geographical Distribution of Animals. 2 vols.
London: Macmillan & Co. 1879.

Beddard, F. E. — Text-book of Zoogeography. Cambridge (Eng.)
Scientific Series. 1895.

D. WORKS DEALING CHIEFLY WITH ANATOMY AND
EMBRYOLOGY

Parker, T. J., and W. A. Haswell. — Text-book of Zoology. 2 vols.
Many illustrations. New York: The Macmillan Co. 1897.

Parker, T. J., and W. A. Haswell. — Manual of Zoology. Adapted
for use of American Schools and Colleges. 563 pp. 327 figs.
New York: The Macmillan Co. 1900.

Rolleston, G., and W. H. Jackson.— Forms of Animal Life. 1888.
Lang, A. — Text-book of Comparative Anatomy. Translated by
Bernard. 2vols. New York: The Macmillan Co. 1896.
Brooks, W. K. — Handbook of Invertebrate Zoology. For labora-
tories and seaside work. Boston: 8. E. Cassino. 1882. [May

be purchased of Bradlee Whidden, Boston. ]

Korschelt, E., and K. Heider. — Text-hook of the Embryology of
Invertebrates. 3 vols. New York: The Macmillan Co.
1899.

Balfour, F. M. — A Treatise on Comparative Embryology. In 2
vols. London: Macmillan & Co. 1880-81.

Although decidedly out of date, yet gives the best general discussion
in English of the subject.

Hertwig, O. — Text-book of the Embryology of Man and Mammals.
Translated by E. L. Mark. New York: Macmillan, 1892.

476 APPENDIX

Wilson, E. B. — The Cell in Development and Inheritance. New
York: The Macmillan Co. 1900.

E. WORKS ON SPECIAL GROUPS
I. INSECTS IN GENERAL

The Cambridge Natural History. Vols. V and VI. Macmillan.
1895 and 1899. [Especially ecological.]

Comstock, J. H. and A. B. — Manual for Study of Insects. Com-
stock Publishing Co. 1899. Price $3.75. [Excellent syste-
matic treatise.]

Comstock, J. H.—Insect Life. D. Appleton. 1897. Price
$2.25.

Folsom, J. W.— Entomology with Special Reference to its Bio-
logical and Economic Aspects. Blakiston. 1906. [Excellent
in its field.]

Smith, J. B.— Economic Entomology. Lippincott. 1896. Price
$2.50.

Packard, A. S.— Fifth Report of United States Entomological
Commission, U.8. Dept. of Agriculture. Washington: Govern-
ment Printing Office. 1890. [Extensive treatise.]

Miall, E. C. — Natural History of Aquatic Insects. Macmillan.
1895. Price $1.75.

Needham, J. G., and C. Betten. — Aquatic Insects in the Adiron-
dacks. University of State of New York, Albany. 1901.
Price $0.45.

Needham, J. G., and others. — Aquatic Insects of New York
State. University of State of New York, Albany. 1903.
Price $0.80.

Needham, J. G., K. J. Morton, O. A. Johannsen. — Mayflies and
Midges of New York. University of State of New York,
Albany. 1905. Price $0.80.

Needham, J. G. — Report of Entomologie Field Station conducted
at Old Forge, N.Y. University of State of New York, Albany.
1908.

Lubbock, J. — Origin and Metamorphoses of Insects. Macmillan.
1895,

APPENDIX 477

Howard, L. O. — The Insect Book. Doubleday, Page & Co. 1901.

Smith, J. B. — Insects of New Jersey. (Franklin Dye, Secretary,
Trenton, N.J.) [Excellent local list.]

Banks, N.— List of Works on North American Entomology.
Washington : Government Printing Office. 1910.

Riley, C. V. — Directions for Collecting and Preserving Insects.
Smithsonian Institution, Washington. 1892. Price $0.25.

II. ORTHOPTERA, NEUROPTERA, HEMIPTERA, ETC.

Guthrie, J. E.—Collembola of Minnesota. Geological and Natural
History Survey of Minnesota. 1903.

Scudder, S. H. — Guide to the Genera and Classification of the
North American Orthoptera found north of Mexico. Cam-
bridge, Mass. 1897.

Lugger, O.— Orthoptera of Minnesota. State Experiment Station.
1898.

Morse, A. P.— Researches on North America Acridiidae. Car-
negie Institute of Washington. 1904.

Miall, L. G., and A. Denny.— Structure and Life History of the
Cockroach. London: Loweil, Reeves & Co. 1886.

Calvert, P. P. — Catalogue of the Odonata (Dragon Flies) of the
vicinity of Philadelphia. Transactions Entomological Society,
Philadelphia. Price $1.00.

Williamson, E. B. — Dragonflies of Indiana. 24th Annual Report
Department Geological and Natural Resources, Indiana. 1899.

Hagen, H. — Synopsis of Neuroptera of North America. Smith-
sonian Collections. 1861.

Banks, N. — Catalogue of Neuropteroid Insects of United States.
Secretary, American Entomological Society, Philadelphia. 1907.

Summers, H. E.— True Bugs, or Heteroptera, of Tennessee.
Bulletin Tennessee Agricultural Experiment Station. 1891.

III. LEPIDOPTERA AND HYMENOPTERA

French, G. H. — Butterflies Eastern United States. Lippincott,
Philadelphia, 1886.

478 APPENDIX

Scudder, S. H.— Butterflies of Eastern United States and Canada,
3 vols. Cambridge, Mass. Privately printed. 1889.

Scudder, S. H. — Brief Guide to Commoner Butterflies of Northern
United States and Canada. Holt. 1893. Price $1.25.

Edwards, W. H.— Butterflies of North America. Houghton,
Mifflin & Co.

Holland, W. J. — Butterfly Book. Doubleday, Page & Co. 1898.

Holland, W. J. — Moth Book. Doubleday, Page & Co. 1903.

Knobel, E. — Day Butterflies and Dusk Fliers of New England ;
how to find and know them (1895); also Night Moths of
New England; how to determine them readily. Boston:
Bradlee Whidden. 1895.

Wright, W. G.— Butterflies of West Coast of United States,
San Francisco. 1905.

Cresson. E. T. — Synopsis of Families and Genera of the Hymenop-
tera, North of Mexico. Secretary, American Entomological
Society, Philadelphia. 1887. Price $3.00.

Lubbock, J. — Ants, Bees, and Wasps. D. Appleton. 1882.

Wheeler, W. M.— Ants, their Structure, Development, and Be.-
havior. Macmillan. 1910.

IV. COLEOPTERA

Le Conte, J. L., and G. H. Horn. Classification of the Coleoptera
of North America. Secretary, American Entomological Society.
1883. Price $2.50.

Ulke, H. — List of Beetles of the District of Columbia, Proceedings
United States Natural Museum, 25, pp. 57. Government
Printing Office. 1902.

Knobel, E. — Beetles of New England; a guide to know them
readily. Boston: Bradlee Whidden. 1895.

V. DIPTERA

Williston, S. W.— Manual of North American Diptera. 3d ed.
New Haven. 1908.

Giles, G. M.— A Handbook of Gnats or Mosquitoes. London:
John Bale Sons & Danielsson. 1902.

APPENDIX 479

Howard, L. O. — Mosquitoes. Doubleday, Page & Co. 1901.
Knobel, E.— Beetles of New England. Boston: Bradlee Whidden,
1895.
VI. MYRIAPODA

Bollman, C. H.— Myriapoda of North America, Bulletin 46,
United States National Museum. Government Printing Office.
1893.

Wood, H. C., Jr. — Myriapoda of North America. Transactions
American Philosophical Society, 13. 1865.

VII. ARACHNIDA

Emerton, J. H.— Common Spiders of the United States. Ginn.
1902.

Comstock, J. H.— Classification of North American Spiders. Com-
stock Publishing Co. 1993.

McCook, H. C.
3 vols., 4to. Secretary, Academy Natural Science, Philadelphia.
1889-93.

Peckham, G. W. and E. G.—North American Spiders of the
Family Attide. Transactions Wisconsin Academy of Science,
Vol. 7. 1888.

Kraepelin, K.—Scorpiones und Pedipalpi. Das Tierreich, 8. Lief-
erung. Berlin: R. Friedlander. 1899.

Banks, N. — Synopsis of the Phalangida, American Naturalist, Vol.
XXXV. 1901.

Banks, N.—A Treatise on the Acarina or Mites. Proceedings of
United States National Museum, 28. United States Govern-
ment Printing Office. 1904.

American Spiders and their Spinning Work.

VIII. CRUSTACEA

Rathbun, R. — Natural History of Economie Crustaceans. Bulle-
tin U. S. Fish Commission for 1889. Government Printing
Office. 1893.

Huxley, G. H. — The Crayfish: an Introduction to the Study of
Zoology. D. Appleton. 1880.

480 APPENDIX

Hay, W. P.— Synopsis of Astacide of North America. American
Naturalist, Vol. XX XIII. 1899.

IX. MALACOSTRACA AND GEOGRAPHICAL
DISTRIBUTION

Stebbing, T. R. R. — A History of Crustacea, Recent Malacostraca.
D. Appleton. 1893.

Faxon, W.— Revision of the Astacide. Memoirs Museum Comp.
Zool., Cambridge, Mass., Vol. X. 1885.

Herrick, F. H. — American Lobster, Bulletin U. S. Fish Commis-
sion, Vol. XV. 1896.

Kingsley, J. S. — Synopses of Caridea and Astacoid and Thalas-
sinoid Crustacea. American Naturalist, Vol. XX XIII. 1899.

Rathbun, M. J. —Synopses of Crabs, American Naturalist, Vol.
XXXIV. 1900.

Wallace, A. R. — Geographical Distribution of Animals. 2 vols.
Macmillan. 1876.

Heilprin, A. — Geographical and Geological Distribution of Ani-
mals. D. Appleton. 1887.

X. ENTOMOSTRACA

Richardson, H. — Monograph on the Isopods of North America,
Government Printing Office. 1905.

Holmes, S. J. —Synopsis of Amphipoda. American Naturalist,
Vol. XXXVII. 1903.

Wheeler, W. M.—Free-swimming Copepods of the Woods Hole
region. Government Printing Office. 1900.

Marsh, C. D.— Revision of the New York Species of Cyclops.
Transactions Wisconsin Academy. 1910.

Hay, W. P. — Ostracoda of North America, American Naturalist,
Vol. XXXIIT. 1899.

XI. WORMS

Cambridge Natural History. Vol. Il. Macmillan. 1896.
Delage, Y., and E. Hérouard.— Les Vermidiens, in Traité de
Zoologie coneréte, Tome V. Schleicher fréres. 1897.

APPENDIX 481

XII. OLIGOCHATA, LEECHES, BRYOZOA, AND
BRACHIOPODA

Michaelsen, W.— Oligochexta, in Das Tierreich, 10 Lief. Berlin:
R. Friedlinder & Sohn. 1900.

Darwin, C. — Formation of Vegetable Mold through the Action
of Worms. D. Appleton. 1881.

Moore, J. P. — Hirudinea of [linois, Bulletin Illinois State Labora-
tory of Natural History, Vol. V. 1901.

Davenport, C. B. — Fresh-water Bryozoa. American Naturalist,
Vol. XXXIII. 1899.

XIII. POLYCHZATA AND LOWER WORMS

Verrill, A. E.— New England Annelida. Transactions Connecticut
Academy, Vol. IV. 1880.

Andrews, E. A.— Report on Annelida Polycheta of Beaufort.
Proceedings U. 8. National Museum, Vol. XIV. Government
Printing Office. 1891.

Johnson, H. P.— Preliminary Account of Marine Annelids of
Pacific Coast. Proceedings California Academy of Sciences,
Vol. I. 1897.

Pratt, H. S. — Synopsis of the Trematodes. American Naturalist,
Nos. 404, 432. 1900, 1902.
Coe, W. R. — Synopsis of the Nemerteans. American Naturalist,

No. 463. 1905.

Montgomery, T. H.—Synopsis of the Gordiacea. American
Naturalist, Vol. 33. 1899.

Ward, H. B. — Parasitic Worms of Man and the Domestic Ani-
mals, in Report for 1894 of Nebraska State Board of Agricul-
ture. 1895.

XIV. MOLLUSCA

Cooke, A. H. — Mollusea in Cambridge Natural History. Mac-
millan. 1896.
Tryon, Gen., Jr. — Structural and Systematic Conchology. S. R.
Roberts. 1882, 1884. Price $6.00.
21

482 APPENDIX

Gould, A. A. — Report on Invertebrata of Massachusetts. 2d ed.
Binney. 1870. [Mollusca and Tunicata.]

Apgar, A. C. — Molluses of the Atlantic Coast of the United States.
A.C. Apgar, 511 E. State St., Trenton. 1891. [Compact, ex-
cellent keys.]

Dall, W. H. — Shell-bearing Marine Molluses and Brachiopods of
the Southeast Coast of United States. Government Printing
Office. 1903. [Numerous figures.]

Baker, F. C. — Mollusca of Chicago Area. Chicago Academy of
Science. 1898-1902.

Ingersoll, E., and J. A. Ryder. — Natural History of Economie Mol-
luses of the United States, in Bull. U. S. Fish Commission for
1889. Government Printing Office. 1893.

XV. GASTROPODS AND CEPHALOPODS, AND ANIMAL
BEHAVIOR

Simpson, G. B. — Anatomy and Physiology of Polygyra albolabris
and Limax maximus, ete. New York State Educational Depart-
ment. 1901. Price $0.25.

Verrill, A. E. — Report on the Cephalopods of the Northeastern
Coast of America. Report of U.S. Fish Commission for 1879.
Government Printing Office. 1882.

Thorndike, E. L. Animal Intelligence, in Psychological Review,
No. 8. Macmillan. 1898.

Jennings, H. S. — Contributions to the Study of the Behavior of
Lower Organisms. Carnegie Institution of Washington. 1904.

Walter, H. E. — Behavior of the Pond Snail. Cold Spring Harbor
Monographs, VI. 1906.

See also Section C.

XVI. LAMELLIBRANCHS AND RIVER FAUNAS

Drew, G. A. — Habits, Anatomy, and Embryology of the Proto-
branchia [Yoldia, Nucula]. Anatomischer Anzeiger. G. Fischer,
Jena. 1899.

Drew, G. A. — Habits and Movements of the Razor Clam. Bio-
logical Bulletin, Vol. XII. 1907.

APPENDIX 483

Kellogg, J. L. — Observations on the Life History of the Common
Clam, Mya arenaria. Bulletin of U. 8. Fish Commission for
1899. Government Printing Office. 1900.

Simpson, G. B.— Anatomy and Physiology of Anodonta fluvia-
tilus. 35th Annual Report N.Y. State Museum of Natural
History. 1884.

C. A. Kofoid. — Plankton of the Illinois River, 1894-1899. Bulle-
tin Illinois State Laboratory of Natural History, Vol. VI, 1903 ;
Vol. VIII., 1908.

XVII and XVIII. ECHINODERMS

Agassiz, A.— North American Starfishes. Memoirs Museum Com-
par. Zoology, Vol. V. 1877.

Azassiz, A. — Revision of the Echini, Illustrated Catalogue of Mu-
seum Compar. Zoology, Vol. VII. 1872-73.

Clark, H. L. — Synopsis of the Holothuroidea of North America,
American Naturalist, Vol. XXXV. 1901.

Brooks, W. K.— Handbook of Invertebrate Zoology. Boston:
Cassino. 1882. [Excellent chapter on the development of
Echinoderms. ]

XIX. CCELENTERATES

Trembley, A. — Mémoires pour servir & l’histoire d’un genre de
polypes d’eau douce & bras en forme de cornes. Leyden. 1744.
[Remarkable first study of Hydra.]

Agassiz, L. — Acalephs, Ctenophore, Discophore, Hydroide, in
Contributions to the Natural History of the United States.
1860, 1862.

Hargitt, C. W. — Synopsis of the Hydromeduse of North America,
American Naturalist, Vol. XXXV. 1901.

Parker, G. H.— Synopsis of the Actinaria of North America,
American Naturalist, Vol. XXXIV. 1900.

Hyatt, A. — Guides for Science Teaching: JII, Commercial and
Other Sponges. Heath & Co., Boston. 1893.

Potts, E. — Synopsis of American Fresh-water Sponges, Proceed-
ings Academy of Natural Science of Philadelphia. 1887.

484 APPENDIX

XX. PROTOZOA

Calkins, G. N. — Protozoa. Macmillan.

Briitschli, O. — Protozoa, in Bronn’s Tierreich. 1889.

Leidy, J. — Fresh-water Rhizopods of North America. Govern-
ment Printing Office. 1879.

Conn, H. W.— Protozoa of Fresh Water of Connecticut. Bulle-
tin Geological and Natural History Survey of Connecticut.
1905.

XXI. VERTEBRATES

Jordan, D. S.— Manual of the Vertebrates of the Northern U. 8S.
Chicago: McClurg.

Kingsley, J. S. — Text-book of Vertebrate Zoology. Holt. 1899.

Parker, T. J.,and W. A. Haswell. — Text-book of Zoology, Vol. II.
Maemillan. 1897.

XXII. FISHES

Jordan, D. S., and B. W. Evermann. — The Fishes of North and
Middle America, Bulletin U. S. National Museum, No. 47.
Government Printing Office. 1898. [Very valuable; with
much biological data and keys.]

Goode, G. B.— American Fishes. New York: Standard Book Co.
1888.

XXIII. AMPHIBIA

Mivart, S. and G. — The Common Frog. Maemillan. 1881.

Dickerson, Mary E. — Frog Book. Doubleday, Page & Co.

Sherwood, W. L. — Frogs and Toads in Vicinity of New York.
Proe. Linn. Soe. of N. Y., No. 10. 1898.

Gage, S. H. — Life History of Newt. American Naturalist, Decem-
ber, 1891.
Ritter, W. E. — Life History of Habits of the Pacific Coast Newt.
Proceedings California Academy of Science, Vol. I. 1897.
Wilder, H. H. — Desmognathus fusca and Spelerpes bilineatus,
American Naturalist, Vol. XN XIII. 1899.

Kirkland, A. H. — Habits, Food and Economie Value of the Ameri-
ean Toad. Hatch Experiment Bulletin No. 46. Amherst,
Mass. 1897.

APPENDIX 485

XXIV. REPTILIA

Agassiz, L. — North American Testudinata and Embryology of the
Turtle, in Contributions to the Natural History of the U. 8.
Little, Brown & Co. 1857.

XXV. BIRDS

Newton, A., and Hans Gadow. — Dictionary of Birds. A. & C.
Black, Edinburgh. 1893-96.

Cowes, E.— Key to North American Birds. 1896.

Ridgeway, R. — Manual of North American Birds. Lippincott.
1896.

Chapman, F. M. — Bird Life. D. Appleton. 1897.

Parkhurst, H. E. — How to name the Birds. C. Seribner.

Wright, Mabel O., and E. Cones. Macmillan. 1898.

Walter, H. E. and A. H. — Wild Birds in City Parks.

Besides these there are dozens of good books on American birds

and guides to their study ; see any good bhook-store.

XXVI. MAMMALIA AND DOMESTIC ANIMALS

Flower, W. H., and R. Lydekker. — Introduction to the Study of
Mammals, Living and Extinct. A. & C. Black. 1891.
Lydekker, R. — Geographical History of Mammals. Macmillan.

1886.
Mivart, S. and G. — The Cat. Seribners. 1881.
Darwin, C.— The Variation of Animals and Plants under Do-

mestication. 2d ed. D. Appleton. 1870.
Bateson, W. — Mendel’s Principles of Heredity. Macmillan. 1909.

XXVII. DEVELOPMENT OF THE FROG’S EGG

Morgan, T. H.— Development of the Frog’s Egg. Macmillan.
1897.

XXVIII. HISTORY OF ZOOLOGY
Locy, W. A. — Biology and its Makers. Holt. 1908.

APPENDIX II

SYNOPSIS OF THE ANIMAL KINGDOM

GROUPS OF ANIMALS ARRANGED APPROXIMATELY
IN AN ASCENDING SERIES; WITH REFERENCES TO
EVERY FAMILY MENTIONED IN THE MAIN TEXT;
AND WITH DEFINITIONS OF THE CLASSES AND
ORDERS

Nore. — Owing to the method employed in the text of proceeding from a
type to the allied groups, the systematic relations of the organisms considered
are often obscured. This synopsis is intended to make these relations clearer.
It can also be used as a systematic index of the book. Moreover, the student
can use it in reviewing his knowledge of the text, and as a key for the deter-
mination of the class in which a specimen falls. The teacher can employ it as
a guide to collecting illustrative material; for every family mentioned should,
as far as possible, be illustrated by specimens or good figures.

In the synopsis group-names printed in full-face are phyla; in
LARGE CAPITALS, classes; in Smatu CapiTats, orders; in
italics, families. Subphyla, subclasses, and suborders are indicated
by bracketing. Thus [CILIATA] is a subclass. Numbers in
parentheses refer to pages of the text.

PROTOZOA

Animals composed of a single cell; or, if of several cells, these are
of one kind.

RHIZOPODA. Protozoa with retractile pseudopodia: Amceha
(284).

SPOROZOA. Protozoa without appendages; internal parasites
(285).

FLAGELLATA. Protozoa without cilia, but with one or more
flagella (286).

486

APPENDIX 487

INFUSORIA. Protozoa with cilia or sucking tentacles (286).
[CILIATA]. Locomotor, with cilia: Houorricua (Parame-
cium, 287); Hererorricua (287); Prrirricua: Vorticella (288).
{[SUCTORIA]. Sessile, with sucking tentacles (288).

C@LENTERATA

Animals of radial structure whose digestive cavity is lined by the
body-wall (262).

[SPONGIARIA]

Ceelenterata whose body-wall is perforated by incurrent pores
(262).

[CNIDARIA]

Ceelenterata whose body-wall is not perforated by incurrent pores,
and which have nettling organs of some sort (264).

HYDROZOA. Cnidaria whose body is composed of more than
two rays and contains a simple cavity. Hypromepusa#, attached
Hydrozoa in hydroid stage; medusa simple: Hydroide (265);
Hydrocorallide (267); Tubularide (267); Campanularide (267) ;
Trachomeduse (Zygodactyla, 271). SripHonopHorA, a free swim-
ming colony of Hydrozoa (271).

SCYPHOZOA. Cnidaria with many radii, and with radial parti-
tions in cavity of body (273).

CTENOPHORA. Cnidaria with only two radii, and rows of
cilia-plates (275).

SCOLECIDA

Animals of worm-like form, with bilateral, unsegmented hody.

PLATYHELMINTHES. Bilaterally symmetrical, soft-bodied
animals, without true segmentation of the body; flattened in a
dorso-ventral direction, and having body-cavity filled with a loose
meshwork of cells. Tursevvarta, free-living flatworms whose body
is covered by cilia; alimentary tract with only one opening to the
exterior: Planaria (191). Tremaropa, parasitic, without cilia in
the adult; the mouth leads into a forked food-canal without anus:
Distomum (193). Crsropa, elongated tape-like intestinal parasites,

488 APPENDIX

without mouth or food-canal: Tzenia (195). NEMERTINI, body more
or less flattened; food-canal with mouth and anus; a separate pro-
trusible proboscis (190).

NEMATHELMINTHES. Bilateral, unsegmented, round-
worms; usually with alimentary tract, mouth, and anus: Ascaris
(191).

ROTIFERA. Small aquatic Scolecida, with ciliated band
around mouth, and a special organ for attachment, the foot; wheel-
animalcules.

BRYOZOA. Scolecida in which the ciliated band is carried out
on a series of tentacles surrounding the mouth; form colonies by
budding. ENpoprocta, Bryozoa with head and stalk, and crown
of tentacles surrounding both mouth and anus (177). Ecroprocta,
with anus outside tentacular corona (177).

BRACHIOPODA. — Shelled, with long, tentaculiferous arms;
lamp-shells (180).

MOLLUSCA !

Animals with unsegmented body and without jointed appen-
dages. Usually with a shell and with a muscular organ of locomo-
tion, the foot.

LAMELLIBRANCHIATA. Mollusca with nearly symmet-
rical here leaf-like gills, and a shell composed of two valves.
Ledide (236); Arcide (234); Mylilide Sadak Aviculide (235);
Pectinida ae Ostreid@ (236); Unionidae (228); Cycladide (230) ;
Mactride (231); Veneride (232); Myide (231); Solenide (231);
Pholadide (230); Teredidew (230).

tASTROPODA. Mollusca with head, feelers, and eyes, an un-
paired foot, and a shell that is univalve when present. AmPHI-
NeuRA, with strict bilateral symmetry, no externally visible gills,
and usually a shell composed of eight pieces: Chiton (220). Proso-
BRANCHIATA, With gills in front, shelled and operculate: Acmaide
(219); Patellide (219); Pissurellide (219); Naticide (217); Ca-
lyptraide (Crepidula, 218); Liltorinida (216); Muricide (Urosal-
pinx, 218); Fasciolariide (Fulgur, 217). OpistTHoBRANCHIATA,

‘This classification, unlike that of the text, follows Cooke in his ‘“ Mol-
lusca.”’

APPENDIX 489

with gills behind heart; if shelled, without operculum; olidiide
(220). Puumonara, breathing by means of lungs, no operculum :
Auriculide (214); Limn@wide (214); Limacide (211); Helicide
(213); Pupide (214).

CEPHALOPODA. Mollusca with large head, mouth sur-
rounded by a circle of arms, and funnel-shaped foot. Argonaulide
(221); Spirulide (221); Loliginide (221); Naulilide (221).

ECHINODERMATA

Animals of a prevailingly radial structure, with intestinal wall dis-
tinct from body-wall and with calcareous plates in the skin (192).

CRINOIDEA. Sessile Echinodermata, having a cup-shaped
body (258).

ASTEROIDEA. Star-shaped Echinodermata, with a furrow
along the under side of the arms (251).

OPHIUROIDEA. Star-shaped Echinodermata, with ungrooved
arms (253).

ECHINOIDEA. With armless, globular, or cake-shaped body
(254).

HOLOTHUROIDEA. Worm-like, with tentacles around mouth
(256).

ANNELIDA

Bilateral, segmented worms without jointed legs.

POLYCHATA. Annelida possessing parapodia on one or more
segments, and with many bristles on parapodia. Erranrta, free-
swimming Polycheta: Autolytus (187), Lepidonotus (187), Nereis
(185). Sepentaria, Polycheta which live in tubes composed of
mud, sand, or lime: Amphitrite (189), Polycirrus (189), Cistenides
(189), Clymenella (188), Serpula (189).

OLIGOCH-ETA. Annelida without parapodia and with few
sete; living in fresh water or in the ground. LimicoL», aquatic:
Nais (173); Dero (172); Tubifex (172). Trrricou®, earth-inhab-
iting: Allolobophora, Lumbricus (169).

GEPHYREA. Annelida having sessile habits and consequently
without external segmentation in the adult, sete sometimes present.
Phascolosoma (176), Echiurus (177).

490 APPENDIX

HIRUDINEA. Annelida with short rings or none at all and with
a ventral sucker; ‘‘bloodsuckers.’’ Clepsine (175) ; Nephelis (175).

ARTHROPODA

Symmetrical, segmented animals, with jointed appendages.

CRUSTACEA. Typically, aquatic and gill-bearing Arthropoda.
Two pairs of antenne, except in Gigantostraca.

(ENTOMOSTRACA]. Crustacea with varied number of
pairs of appendages; usually of small size. BraNcHiopopa, man-
dibles without palps, numerous legs (156). TrrtLosira, fossil (160).
CxLapocera, mandibles palpless, few legs (157). Ostrracopa, palp
on mandible, only two pairs of legs (157). Coprpopa, elongated
Crustacea, with only one pair of maxille; females with external
ovisacs (158). Currripepia, attached Crustacea (barnacles, 158).

[MALACOSTRACA]. Crustacea with nineteen pairs of ap-
pendages. Ampuipopa (146). Isopopa (145). Stomatropopa (144).
PopopaTHatmata: [Macrural], large-tailed Podophthalmata : Cari-
dide (138); Astacide (131); Thalassinid@w (138); Paguride (138) ;
Hippide (140). [Bracuyura], crabs: Oxyrhyncha (140); Cyclo-
metopa (141); Catometopa (143).

(GIGANTOSTRACA]. Crustacea with five pairs of appen-
dages on cephalo-thorax, abdomen without feet ; body ends in a long
telson, Limulus (146).

ARACHNOIDEA. Air-breathing Arthropoda without antenne.
AcariIna, mites (117). Pycnoconipa, sea-spiders (119). ARE-
NEINA, spiders: Saltigrade (110); Citigrade (109); Laterigrade
(109); Tubitelarie (105); Retitelarie (106); Orbitelarie (106);
Territelarie (105). PHauanoina, harvest-men (117). ArtTHRo-
GASTRA, scorpions (116).

TRACHEATA. Air-breathing Arthropoda, with one pair of
antenne.

(PROTRACHEATA]. Tracheata with worm-like body.
Each segment of the trunk bears a short, stout appendage. Peri-
patus (101).

[MYRIAPODA]. Tracheata with distinct head and abdo-
men, all the segments of the abdomen bearing appendages. Cut-

APPENDIX 491

LOPODA, centipedes: Scutigeride (98); Lithobiide (98); Scolopen-
dride (99) ; Geophilide (100). DipLopopa, millipedes: Julide (100) ;
Polydésmide (100). SympuyLa: Scolopendrella (101), Pauropus
(101).

[HEXAPODA]. Tracheata with only three pairs of legs, con-
fined to thorax. Orruoprera, Hexapoda with two pairs of wings,
masticating mouth-parts, incomplete metamorphosis: Forficulide
(17); Blatttde (17); Mantide (17); Phasmide (18); Acridide (13);
Locustide (19); Grillide (20). NeuroprerRa, Hexapoda with two
pairs of net-veined wings; biting mouth-parts, metamorphosis com-
plete or incomplete: Odonata (24); Ephemeride (24); Termitide
(26); Sialide, Corydalis (28). Hrmiprera, Hexapoda with two
pairs of wings or none, sucking and piercing mouth-parts, incom-
plete metamorphosis. [Hrrrroprrera], upper wings leathery:
Redwiide (23); Pentatomide (22). [Homorrera], wings alike:
Cicada (23); [here, also, plant lice and animal lice]. Diprera:
Hexapoda with (typically) one pair wings; piercing and sucking
mouth-parts; complete metamorphosis. [ApHANIpTrERA], fleas (88).
{(Pupipara]: Hippoboscide. [BracHycrra], true flies: Muscidae
(80); stride (81); Syrphide (82); Asilide (82); Tabanide (82);
Simuliide (83). [Nematocgrra], gnats: Cecidomyide (83); Culicide
(84); Tipulide (87). CoLnoprERra, Hexapoda whose fore wings are
modified into wing covers; hind wings folded when not in use: Coc-
cinellide (73); Chrysomelide (72); Cerambycide (72); Curculionide
(71); Scolyttde (71); Lampyride (70); Elateride (70); Buprestide
(70); Lamellicornia (69); Lucanide (68); Dermestide (68); Sil-
phide (67); Staphylinide (66); Hydrophilide (65); Gyrinide (65) ;
Dytiscide (65); Carabide (64); Cicindelide (63). LeprpoprEera,
Hexapoda with two pairs of scale-covered wings, sucking mouth-parts,
complete metamorphosis: Tineide (47); Tortricide (47); Geometride
(47); Noctuide (45); Bombycide (42); Arcttide (42); Xylotropide
(42); Sphingide (47); Papilionide (40). Hymenoprrera, Hexapoda
with two pairs of membranous wings; biting and licking mouth-
parts; complete metamorphosis: [PHytopHacal], plant-eating (59).
[ENTOMOPHAGA] insect parasites (58). [AcuLEATA] stinging: Formi-
cide (52); Fossoria (52); Vespide (51); Apide (49).

492 APPENDIX

CHORDATA

Animals which possess, at some time of life, throat slits and a
dorsal supporting rod or chorda.

(HEMICHORDA]

Animals of worm-like form, showing gill-slits like fishes. Balano-
glossus (293).

[TUNICATA]

Usually sessile Chordata, often forming colonies (290).

[VERTEBRATA-ACRANIA]

Free-living fish-like Chordata, but without skull, paired fins, or
heart, and with colorless blood. Amphioxus (294).

(VERTEBRATA-CRANIATA]

Free-living Chordata, with skull and complex brain, and red
blood.

CYCLOSTOMI. Eel-like vertebrates without lower jaw, and
living a parasitic life (322).

PISCES. Aquatic vertebrates with gills, without lungs, and
with paired fins instead of legs. Spiacuu, skeleton cartilaginous, no
operculum, spiral valve (322). Ganorpe1, skeleton either cartilagi-
nous or bony, spiral valve and operculum present : sturgeons (323) ;
spoon-bill (324); garpike (324); bowfin (324). TrLerosrer, skele-
ton bony, no spiral valve. [AcanTHopTeErt], dorsal, anal, and ven-
tral fins with spines, pharyngeal bones distinet: perches (312);
darters (311); sunfishes (313); toadfishes (313); seulpins (313);
silversides (314); sticklebacks (315). [PHaryncoGnarui], fins with
spines, pharyngeal bones united. [ANacanTuini], fins without
spines, ventral fins far forward: codfishes (310); flatfishes (316).
[Puysostomyi], fins without spines, ventral fin placed far backward:
smelts (309); trouts (310); whitefishes (316); catfishes (317);
suckers (317); minnows (318); pikes (319); shads (319); eels

APPENDLY 493

(320). [PLecroenarui], intermaxillaries and maxillaries united.
{(LopHosrancui], body covered with bony plates: pipefishes (321).
Dipwnot, lung-fishes (324).

AMPHIBIA (= Batrachia). Vertebrata having no lateral fins
(but instead, legs); functional external gills during a part of their
life. Uropsva. Amphibia which retain the tail permanently:
Strenide (255); Proteide (339); Amphiumidw (339); Crypto-
branchide (339); Amblystomida (340); Plethodontide (342); Des-
mognathide (342). ANura, Amphibia which lose the tail in the
adult stage: Pipide (345); Hylide (345); Bufonide (347); Ranide
(347). Gymnopuiona, Amphibia which have no limbs nor tails;
body worm-like (329).

REPTILIA. Vertebrata which breathe exclusively by lungs
and whose skin contains horny epidermal scales or bony plates.
CHELONIA, trunk enclosed ina bony case: Chelonide (362); Trio-
nychide (363); Testudinide (363). Sauria, shoulder-girdle and
sternum present, usually with eyelids: Chamealeonide (360); Iguan-
ide (857); Varanide (858); Lacertide (359); Helodermide (359) ;
Anguide (360). Oputpia, footless scaled reptiles with no shoulder-
girdle, sternum, nor movable eyelids: Colubridw (365); Elapide
(366); Crotalide (366). Crocopiuina, large reptiles, with longitu-
dinal vent (368).

AVES. Feathered Vertebrates. Cursorres, Aves with keelless
sternum (391). NaratTores, swimming birds (392). GRranua-
ToRES, wading birds (393). Gains, large ground birds with
strong, perching feet and flat nails (394). Co LumBin 4, short cloven
feet and compressed nails (396). Coccyagrs, birds with powerful
beak and feet adapted for climbing (399). Picr, woodpeckers (400).
Macrocuires, long-winged birds, without cere or scales on meta-
tarsus (401). Passrres, birds whose metatarsus is covered with
lamine or scales, usually with singing apparatus: Tyrannide (402) ;
Alaudide (404); Corvide (404); Icteride (405); Fringillide (406) ;
Tanagride (407); Hirudinide (408); Ampclide (409); Laniide
(409); Vireonide (409); Mniotilide (410); Troglodyltide (410);
Certhiide (413); Paride (413); Turdide (413). Raprorss, birds
with cere, hooked bill, and strong, hooked claws (396). Psrrract,
birds with cere, high, hooked beak, and fleshy tongue (parrots, 397).

494 APPENDIX

MAMMALIA. Vertebrates which nourish the young by means
of milk, and are usually covered with hair. MonorTremata, ovipa-
rous mammals (439). Marsupauia, provided with a marsupium
(440). Epenrara, teeth either absent, rudimentary, or without
enamel (441). Crracea, marine hairless mammals, hind limbs
absent (442). Unauxuata, hoofed mammals: even-toed ungulates
(444); odd-toed ungulates (445); elephants (445). Ropgntia,
canines absent, incisors grow continuously through life (446.) Car-
NIVORA, canines large (446). Insectivora, small, terrestrial, car-
nivorous mammals, with small canines (445). CHEIROPTERA,
mammals with flying membrane between elongated digits (448).
PrimMATES, with hands (449).

INDEX

A

Abdomen, 3, 120.

Abnormalities in Crustacea, 151.

Aboral, 238.

‘Academies established, 465.

Acarina, 117.

Acartia, 158.

Acmea, 219.

Admiral, 40.

Agassiz, Alexander, 471.

Agassiz, Louis, 469.

Agricultural ant of Texas, 55.

Air-bladder, 305.

Albino mice, 430.

Aldrovandi, 461.

Alternation of generation, 269.

Alligator Snapper, 363.

Alligators, 351, 369.

Amblyopsis, 94.

Amblystoma, 343, 456.

Amblystomide, 340.

Ameiurus catus, 317.

Amia, 323, 324.

Ammonites, 222.

Amceeba, 284.

eb 328; metamorphosis of,
343.

Amphioxus 294.

Amphipoda, 145.

Amphitrite, 188.

Amphiumide, 339.

Anatomical Zoology, 463.

Anatomy, 2; of Amphibia, 329; of
Annelids, 161; of birds, 376; of
Crustacea, 120; Echinoderms, 238 ;
insects, 1; mammals, 432; Mol-
lusea, 199; turtle, 352.

Ancestry of Vertebrates, 289, 296.

Angle-wings, 40.

Animal architecture, 102.

Animal behavior, A study of, 208.

Animalcula, 282.

Annelids, 161, 172; anatomy of,
161; circulatory system of, 164;
excretory organs of, 166; general
form of body, 161; musculature of,

167; organs of nutrition, 163;
phy: siology of, 161; respiration in,
164; reproductiv e organs of, 166;
sense-organs of, 167.

Anodonta, 228.

pcr hee 86.

Anophthalmus, 95.

Ant-eater, 441.

Antelopes, 444, 445.

Antenne, 4, 13, 31

Anterior, 2.

Ant-lions, 28.

Ants, 52; armies, 55; colonies, 53,

5; language, 54; leaf-cutting, 56.

Anura, 329, 344.

Apes, 450.

Aphids, 24.

Aphrodite,

Apidee, 49.

Aplysia, 212.

Appendages, 3;
of Annelids,
of Crustacea,
mammals, 434.

Apteryx, 391.

Aquatic pulmonates, 214.

Arabian horse, 424.

Arachnida, 114.

Araneina, 104.

Arbacia, 256.

Arca pexata, 234.

Archeopteryx, 418.

Arcidex, 230, 234.

Arctiide, 42.

Argiope, 107.

Argonauta, 221.

Arion, 212.

Aristotle, 459.

Arks, 234.

Armadillo, 441.

Army-worm, 45.

Arthrobranch, 123.

Arthropods, 114.

Ascaris, 191.

Asiphonata, 227.

Assassin-bug, 22.

186.

of Amphibia, 331;
163; of birds, 382;
120; insects, 3;

495

496

Astacus, 130; food, 133;
distribution, 130;

Asteris

Atoll, 27

Attached animals, a study of, 260.

Attidee, 110.

Auriculidie, 214.

Autolytus, LS7.

Aviculide, 230, 235.

geograph

B

Baboon, 450.
Bacteria, 76.

Badger, 446.
Balanoglossus, 293.
Balfour, 469.
Baltimore pa 405.
Bark-borers, 71.
Barnacles, ,

Be: aker animals, DETs
Bears, 446.
Beaver, 446.

93

Bedbug, 23

ical |
organs of, 123.

Bees, 49; domestication of, 427;
honey, 50; social, 49; swarming,
50.

Beetles, 60; development of, 62;
economic importance of, 74, 75;
food of, 61; geographical range of,
ee habitats of, 61; larval habits

Hehiwon animal, 2
Bell-anime alcule, 26
Bell-hydroids, 2
Bilateral sy mmetry,
Binomial nomenclature,
Birds, 420; classes of, :
ticated, 425; extinction of, 4
flight of, 414; migration of, 3
migration routes of,
system of, 3: nervous
of, 389; organs of, 383-33
prey, 396; protection of,
sense-organs of, 389;
370; teeth of, 419.
Bivalve Entomostraca,
Bivalves, 227.
Blackbirds, 405.
Black-flies, 83.
Black rat, 430
Black snake, 36!
Black Sw: ee -tail, 40.
Blattide
Blind cray fash, 92, 97.

oF

290.
463.
)

4
study

157.

domes-

18;
Bl:

372; muse cul ir

LZ:
of,

INDEX

Blindworm, 360.
Blister beetle, 75.
(See also Circulation.)

Blood-vessels, 2.

Bluebird, 413.

Blue crab, 142; economic importance
of, 146.

Bobolink, 406.
Boll-worm, 45.
Bombus, 49.
Bombycicke,

Bombyx, 42.

Bony fishe Ss, +
Boring Mollusca,

39, 42.

230.

269.

Bougainvillia,

Bowfin, 324.
Box-tortoise,
Brachiopoda,

363.
1s0.

Brachycera, SO.
Brachyura, 140.
Brain coral, 275.

308.
160.

Brain, divisions of,
Branchiopod, 156
pues star, 253.
Brook sue kers, oleh.
Brown creeper, 413.
Brown rat, 431.
Brown-tail moth, 47.
Bruchids, 62.
Bryozoa, 177;
Buck beetle, 72
Budding in corals, 277.
Buffalo-bug, 61, 63.
Buffalo-gnat, SS.
Buffon, 466.
Bufonide, 347.
Bugula, 178.
Bullfrog, 348.
Bullhead, 317.
Bumblebees, 49.
Bupestide, 70.
Burrowing habits, 168.
Buthus, 116.

of estuaries, 225.

Butterfy, 29; broods of, 34; devel-
opment of. habits and food. of,

polymorphism,
35;

32; mimicry, 35;

34; protective resemblance,

types of, 40; wings of, 33.
Byssus, 229.

Cc

Cabbage butterflies, 34, 40.
Callinectes, 142.

Calosoma, 64.

Cambarus, 132, 143.

INDEX 497

Camels, 444. Chordates, 289; relationship to in-
Campanularide, 267. vertebrates, 290.

Camponotus, 53. Chrysomelidie, 72.

Canada grouse, 395. Chrysops, 83.

Cancer, 142. Cicada, 23.

Canker-worm, 47. Cicindelide, 63.

Capillaries, circulation in, 464. Cilia, 276, 286.

Carabidee, 64, 95. Ciona, 293.

Carapace, 363; of lobster, 123. Circulation, organs of, in Annelids,
Carboniferous age, 12. 164; in birds, 386; insects, 7; in

Carchesium, 287. fish, 307; in frog, 333; in lobster,
Cardinal Grosbeak, 407. 24; in mammals, 436; in turtles,
Carnivora, 446. 353.
Carnivorous, 17. Cirri, 189.
Carolina paroquet, 398. Cistenides, 189.
Carpenter ant, 53. Citheronia, 44.
Carrion beetles, 67. Civet-cats, 446.
Case-bearers, 48. Cladocera, 157.
Cassowary, 391. Clams, fresh-water, 227; marine, 231.
Cat, 420, 446. Cleavage, 456; of frog’s egg, 451.
Caterpillar, 30, 31. Clepsine, 175.
Catfish, 317. Click-beetles, 70.
Catocala, 35, 45. Chsiocampa, 45.
Cattle, 422. Clothes-moth, 32, 48.
Caudina, 258, 259. Clymenella, 188.
Cave beetles, 95. Cnidaria, 275.
Cave crickets, 95. Cobra, 366.
Cobweb spiders, 106.
Cecropia moth, 44. Coccinellide, 73.
Cedar waxwing, 410. Coccyges, 399.
Cells, 469. Cockatoos, 397.
Centipedes, 97. Cockroaches, 17.
Cephalopoda, 198, 220. Cocoon, 31; of spider, 109.
Cephalothorax, 104. Codfish, 316.
Cerambycid, 62, 72. Codling-moth, 47.
Ceryle, 400. Ceelenterata, 262.
Cetacea, 442. Colaptes, 400.
Ceuthophilus, 95. Coleoptera, 60.
Cheetie, 163. Colonies, in ants, 53; in bees, 49; in
Cheetopod, 163. enidaria, 277; wasp, 51.
Chameleon, 357, 360. Colorado potato-beetle, 73.
Cheetah, 446. Colubride, 365.
Chelicerze, 105. Columbine, 396.
Chelonia, 351, 362. Condor, 396.
Chestnut-sided warbler, 410. Congo snake, 339.
Chewink, 407. Contact lovers, 447.
Chickadee, 413. Contour feathers, 376.
Chigger, 119. Conurus, 398.
Chilopoda, 97. Cooper’s hawk, 396.
Chimney swift, 402. Copepoda, 158.
Chimpanzee, 450. Copperhead, 368.
Chinch-bugs, 22. Coppers, 41.
Chipping-sparrow, 407. Copris, 69. :
Chitin, 201. Coral, brain, 275; formation of
Chiton, 220. colonies of, 277; organ-pipe, 267;
Cholera, 281. reefs, 276.
Cholcepus, 442. Cordylophora, 265.
Chorda, 289, 294. Coregonus, 311.

2k

498 INDEX

Corvide, 404. Deer, 444.
Cotton-worm, 45. Dermestide, 68.
Cow-bird, 406. Dero, 172.

Crab, burrowing, 142; spider, 109;
swimming, 142.

Crab-spiders, 109.

Crane, 393.

Crane-flies, 87.

Crayfish, 128; distribution, 130.

Creeper, 413.

Crepidula, 218.

Cribella, 252.

Cricket, 1, 20; cave, 20; external
structure, 3; general form, 2;
mole, 21.

Cricket- ar assheDpens 20.

Crinoids, ‘

Crocodiles, 351, “368.

Crop, of birds, 383;
of Mollusca, 202.

Crossbill, 406.

Crotalide, 366.

Croton bug, 17.

Crow, 404.

Crow blackbird, 405.

Crustacea, 134, 281; abnormalities
in, 151; anatomy of, 120; phys-
jology of, 120; regeneration of
lost parts of, 149.

Cryptobranchide, 339.

Ctenophora, 275.

Cuckoos, 399.

Cucumaria, 258.

Culicide, 84.

Curculionide,

of cricket, 6;

ral

Currant-worm, 59.
Cursores, 391.
Cuticula, 3, 4, 30.
Cuttlefish, 220.
Cut-worm, 46.
Cuvier, 467,

469.

rate of reproduction,

Cyclostomi, 322.
Cynthia moth, 43.
Cytology, 469.

D

Daddy-long-legs, 117.

Danaide, 37.

Daphnia, 134, 153, 157.

Darters, 312.

Darwin, Charles, 469, 470.

Darwin, Erasmus, 470.

Darwinism, 37, 470.

Decapods, economic importance
145.

of,

Desmognathide, 342.
Desmognathus, 326, 342.

Development, beetle, 62; crayfish,
148; effect of heat on, 453; of
light on, 453; frog’s egg, 451;
fly, 78; general laws of, 456;
grasshopper, 15; Lepidoptera, 29;
lobster, 146; mammals, 437;
postembryonic, of frog, 455; star-

fishes, 247; Urodela, 343.
Devonian age, 12.
De Vries, 428, 470.
Diapheromera, 19.
Didelphys, 441.
Digestion (see Nutrition).
Digger wasps, 52.
Dimorphism, sexual, 113.
Diplopoda, 100.
Dipnoi, 303, 324.
Diptera, 76-89.
Discontinuous genera, 132
Disease-producing animals, 76.
Distomum, 196.
Diver-beetle, 65.
Division of labor, physiological, in
Cnidaria, 278; in Crustacea, 151.
Dodo, 396, 418.
Dog, 422, 446.
Dolphins, 443.
Domestic animals, evolution of, 420.
Dominant characters, 429.
Dorsal, 2.
Downy woodpec ker, 401.
Dragon- flies
Dryness-lovers, 349.
Duckbill, 439.
Duckbill catfish, 324.
Dytiscidee, 61, 65.

E

Eagle, 396.

Earthworm, 168; economics of, 171;
food of, 170; regeneration in, 170;
source of diseases, 172.

Earwig, 17.

Echidna, 439.

Echinoderms, 238 ;
musculature — of,
system of, 245; organs of circula-
tion, 243; excretion, 244; repro-
duction, 244; respiration, Dad's
phy siology of, 238; sense-organs
oie 245; water- vascular system cf,

anatomy of, 238;
244; nervous

INDEX

Echinoids, 254.
Echiurus, 177.

Ecology, beetles, 60; birds, 416;
butterflies, 32; grasshopper, 13.
Economies of, beetles, 61; birds, 416;

earthworms, 171; fishes, 298 ; grass
hopper, 13; Lepidoptera, 3
; parasitic worms, 195
309 | slugs, 211;
Ectoderm, 262.
Ectoprocta, 179.
Edentata, 441.
Edible crab, 141.
Eel, 320 ; lamprey,
Effect of heat and light on the devel-
opment of the egg, 453.

smelts,
spider webs, 112.

Egg, fertilization of, 247, 307, 335,
437.

Egrets, extermination of, 394.

Elupide, 366.

Elateride, 70.

Elephants, 445.

Elytra, 60, 66.

Embryology, definition of, 247;
history of, 468; study of, 246.

Encyclopedic zoology, 462.
Endoprocta, 177

Enemies of the lobster, 136.

English sparrow, 370; body covering,

379; food of, 375; form of body,
376; spread of, in America, 374.

Engraver beetle, 71.

Ensis, 231.

Entoderm, 262.

Entomostraca, 134, 153, 281; bi-
valve, 157; distribution of, 155;

volume of, 153.

Eolis, 220.

Ephemerida, 24.

Euglena, ae

Eupagurus, 139.

Even-toed hoote d mammals, 444.

Evolution, of domestic animals,
of species, 466; theory of, 469.

420;

Excretion (see Excretory organs).

Excretory ducts, 2.

Excretory organs, annelids, 166; |
birds, 387; cricket, 7; fish, 307; |
frog, 334; lizards, 354; lobster,
125; mammals, 437.

Exhalent opening, 291.

Exotic species, increase of, 375.
Extinct birds, 418.

Eyespot, 295.

F

Fairy shrimp, 156.
Falcon, 396.

499

Fertilization, 9.
Femur, 5.
Fiddler-crahbs, 143.

Filaria, 86.

Fireflies, 61, 70.

Fish, 420; armored, 303; bony, 302;
cartilaginous, 302; cl ification
of, 302; culture of, 301; domes-

ticated, 425; general form of body,
303; musculature of, 308; ner-
vous system of, 308; organs of
circulation, 307; excretion, 307;
nutrition, 305; reproduction, 307;
respiration in, 307; study of the
food of, 153; sense-organs of, 308°
use of, by man,
Fisheries, value of,
Fissurella, 219
Flagellata, 286.
Flatfish, 316.
Flatworm, 191.
Flea, 88.
Flesh-eaters, 446.
Flight of birds, 414.
Flower-flies, $2.

\
299,

Fly, 76; ae ‘generate, 87; develop-
ment, 7 Seanaie import: ice of,
ss, SO hae mimicry in, 52

parasitic, eae
Flycatchers, 402.
Food-canal, 294.

Food of beetles, 61; butterflies, 32;
earthworm, 170; fishes, 153; flies,
78; fresh-water mussels, 228;

hydra, 2 lobster, 12 nerc

186; mice, 4381; sparrow, 375 5:
whale, 443.

Food supply, a study of, 298.

Forficulid, 17.

Form of body, frog, 329; mammalia,
432; turtle, 352.

Formicide, 52.

Fossil brachiopods, 180; birds, 418;
cephalopods, 222; lizards, 361;
man, 450.

Fowl, domestic, 425, 426.

Fox, 446.

Fox-sparrow, 407.

Fresh-water hydroids, 265; mussels,
228; sponges, origin of, 225;
turtles, 363.

Fringillidee, 406.
Fringing reefs,
Fritillar 40.
Frog, 325, 347; general form of body,
329; muscular system of,
nervous tem of, > organ
circulation, 333; exeretion,

277.

n

500

reproduction,
sen
329,

nutrition, 331;

re spiration, 333 ;
skeleton of,
mace s egg, deve re nt of, 451.

Fulgur, 217.
Fundulus, 319.

G
Gadus, 316.

epee the anatomist, 460.
100.

Galley-worm,
Gall-gnats, 83.
Gall-wasp, 58.
Galline, 394.
Galls, S4.
Gallus, 395.
Ganglia, 9.
Ganoidei, 323.
Ganoids, 303.
Garpikes, | 324.
Garter paaake i

rasteropoda, 210.
usteropods, 19
organs of res
asterosteus, 315.
astrolith, 137.
astrulation, 457.
425.

Cu form of body,

5 202s

G
G
G
Geese,
Gelasimus, 143.
Genera, discontinuous, 133.
Generations, alternation of,
Geographical distribution
fish, 128.
Geometride,
Geomys, 448.
Geophilus, 100.
Gephyrea, 176.
Germ-cell, 8, 246.
Germ theory of disease, 283.
Gesner, 460.
Gibbon, 450.
Gila monster, 359
Gills,
Gill-slits,
Giraffe,

Glass-snake,

of

47.

2:

294,

295,
444, 445.

2bO-

360.

Glochidium, 229.
Glossina, SI.
Glow-worm, 71.

Cat, 83.
Gnawing mammals,
Goats, 424.
Goat-suckers, 401.
Goldfish, 319.
Gopher, 446.
Gorilla, 450.
Crallatores,

446.

393.

organs

269.

INDEX

334;
of,

198 ;

cray-

| Grapta, 40.

| Grasshopper, 11; allies of,
cricket, 20; long-horned, 19.

Gray-veined White Butterfly, 34

Great auk, 418.

Great northern shrike, 411.

16;

Green frog, 348.
Green turtle, 362.
Gregarious, 13 3.

Ground- bee tles, 64.
Grouse, 395
Grylhide, 20.
CGryllotalpa, 21.
Guinea-fowl, 395.
Guinea- -pigs, domesticated, 424.
Gull,
iene 329.
Gypsy moth, 46.
Gyrinidie, 65.

yee
Habitat: aerial, 12,371; cave, 92-97;
darkness, 90, 91; desert, 349;
or, 223; land, 325; river,
shore, 182; sessile, 260;
25s terre sstrial, 168.
Hemal, 297.

Hair-streaks, 41.

Hairy ant-eater, 441.
Hairy antelope, 401.
Hard-shelled clams, 232.
Hare, 448.

Harvester ant, 55.
Harvestmen, 117.
Hawk, 396.

Hawk-bill turtle, 363.
Hawk-moths, 41.

Head, 3.
Healing,
Heart
Heat,

45-4.
(see Circulation).
effect on development of egg,

453.
Helix, 213; variability of, 214.
Hellbender, 341.
Helodermic
Hemiptera, 22.
Hemocyanin, 204.
Hen clams, 231.

Hermaphrodite, 160.
Hermit-crabs, 138.
Heron, 393.
Hesperornis, 418.
Hessian-fly, 83.
Heteroptera,
Heterotrichia,
Hexapoda, 12.
| Hippide, 140.

287.

INDEX 501
Hippopotamus, 444. Jellyfish, 270; of fresh water, 266;

History of Science of Zoology, 458.
Holothurians, 240, 244, 256.
Holotrichia, 2
Homarus, disnibinion of, 134.
Homoptera, 22, 23.

Honey bees, 50.

Hoofed mammals, 444.
Horn-fly, 88.

Horn-pout, 317.

Horned Corydalis, 28.
Horned toad,
Hornet, | 51.

357.

House wren, 412.
Humming-birds, 401.
Huxley, 468.
Hydra, 260, 262,
of budding in,

264, 275; discov
Hae -like anin

of estuaries, 225; regeneration
279.

Hydrachnids, 117.

Hydractinia, 266.

Hydranth, 267,
Hy drocor allidie,
Hydroids, bell,
265; tubularian, 267.
Hydromeduse, 271.
Hydrophilide, 65.
Hydrozoa, 271.
Hyenas, 446.
Hylide, 345.
Hymenoptera, 48 ;
eating, 59; stinging,

Ot], 273%
VE

67
267; fresh-wa

4s.

Ichneumon, 58.
Icteride, 405.
Iguanidse, 357.
Imago, 24, 32, 337
Increase of exotic species,
Indigo bird, 407.
Infusoria, 282, 286.
Inhalent ope nings, 291.
Insects, disse ae aoe of disease,
domesticate ad, 42
Intelligence of Lite 53
Intestine of cricket, 6
Isabella caterpillar, 42.
Tsopoda, 145.
Isoptera, 26.

375.

Jackals, 446.
Jay, 404.

ery
tals
in,

ter,

boring, 48; plant-

of Diptera, 75.

282

Jigeer,
Joint-snake,
Julus, 100.
Jumping spiders, 110;
June-bugs, 69.

life-history of, 268.

119.

360.

446.

mice,

Kk

Kallima, 36.
Katydids, 19.

Kidney tubules, 295.
Killer whale, 443.
Killifish, 318.
Kingbird, 403.
Kingfishers, 400.
Kitchen-middens, 237.

L

Labium, 4.
Lacertidx, 359.
Lachnosterna, 63.
Ladybird beetle, 73.
Lady-crab, 142.
Lamarck, 466, 467.
Lamellibranchs, 198.
Lamellicorn bectles, 68
Lamprey eels, 302, +
Lamp-shells, 180.
Lampyride, 70.
Land life, origin of, 325.
Land-locked fishes, 309.
Land tortoises, 363.
Language of ants, 54.
Lantern of Aristotle,
Larks, 404.
cea, 291.
Larvee, of amphibia,
tera, 62; of Diptera,
Lepidoptera, 32; of lobster,
Larval stage,

242.

342; of Coleop-
78; of
148.
30.
Lash animalcules, 286.
Laws of development, 456.
Leaf-cutting ants, 56.
Leaf-eating beetles, 72;
69.
Leaf-hopper, 24.
Leaf-insects, 18.
Leaf-miner, 47.
Leaf-roller, 47
Learned societies,
465.
Ledidie, 230, 236.
Leeches, 174.
Leeuwenhoek, 464.
Lemur, +450.

lamellicorns,

establishment of,

502

Leopard, 446.

Leopard frog, 34
Lepidonotus, 186
Le ae ia ee

Limnea, DUA,
Limpet, 219.
Limulus, ‘

Linnzeus, 463, 4
Liobunum, 115.
Lions, 446.

8.
d.

106.

36.

Lithobius, 90, 97, 98
littoria, spread of,
rudis, 217.

Littorina, 216;
217, 379; palli

Liver of frog,
pigeon,

Liver-fluke,

ata, 217 ;

e -conomics of,

331; lobster,

5; smelt, 305.

93.
Lizards, 349, 356, 357;

dr

nas,

ee 120;
development of, 146;
of, 134; economic importance

145; enemies

125; molting of, 136;

yness lov

circulation

of, 136;

INDEX

39;

1223

common,

ers,

in,

of, 125; nervous system of,

nutrition in, 122; protection of, 1

reproductive ¢
tion in, 122;

Locomotion, of bird, 415 ;

349;

124;

distribution

of,

excretion in,
musculature

126;

ysrgans, 125; respira-
sense-organs of, 126.

Locust borer, 74.
9

Locustidee,
Locusts,
Loligo, 221.

Long-horned beetles, 72;

grasshoppers,

Louse-flies,

Tosi: 109.
Lynx, 446.

Macaques, 450.
Macrura, 140.

19.

Long-winged ap pirds, 401.

M

flies,

of snail, 200.

82;

Mactra, 232.

Mactridie, 230, 231.

Madreporite, 240.

Maggots, S80.

Malacostraca, 134, 144.

Malaria, 251, 285; causes of, 85.

Malpighi, 463, 464, 46s.

Mammalia, 420, 432, 441.

Mammals, even-toed, hoofed, 444;
form of body of, 432; function of
digestion, 434; gnawing, 446;
hoofed, 444; muscular system of,
438; nervous system of, 435;
odd-toed, hoofed, 445; organs of
circulation, 436; digestion, 454;
excretion, 437; reproduction, 437 ;
respiration, 436; sense organs of,
439; skeleton of, 433; structure
of, 482.

Manatees, 442.

Mandrills, 450.

Mantide, 17.

Mantis shrimp, 144.

Mantle of Mollusca, 198, 199, 210.

Manx cat, 420.

Marmosct, 450.

Marmot, 446.

Marsupialia, 440.

Martens, 446.

Maryland yellow-throat, 410.

Maxillee, 4.

May flies, 24, 26.

Meadow grasshopper, 20.

Meadow-lark, 406.

Meal-beetles, 61.

Mealy bugs, 24.

Me asuring worms, 35, 47.

Meduse, 259.

Melampus, 214.

Membranes, 1.

Mendel, 429.

Mendel’s law, 429.

Metallic wood-borers, 70.

3; Amphibia, 343,
456; Coleoptera, 6 Diptera, 80;
Echinodermata, a Lepidoptera,
31; Tunicata, 292

Metridium,

Mice, domestic: ation of, 428; food of,
431; habits of, 431; rapid distri-
bution of, 430.

Microhydra, 266.

Migration routes, of birds, 372; of
redstart, 373; study of, 370.

Milk-snake, 5.

Millipedes, 97, 100.

Mimicry, 35, 37, 82.

Minks, 446.

S)

INDEX 503

Minnows, 318.

Mites, 117.

Moceasin snake, 366.

Mocking-bird, 412.

Mole, 445.

Mole-crabs, 140.

Mole-cricket, 21

Mollusca, 210; anatomy of, 198 ; mus-
culature of, 206; nervous system
of, 206; organs of circulation, 203;
excretion, 204; nutrition, 200;
reproduction, 204; physiology of,
198; sense-organs of, 206.

Molt, 16; of lobsters, 136.

Monarch, 37, 40.

Mongoose, 446.

Monkeys, 450.

Monotremes, 439.

Morone, 311.

Morphological Zoology, 463.

Morula, 457.

Mosquitoes,

Moth, 29.

Mother-of-pearl, 236.

Mourning-cloak, 40.

Mouse, 420, 446.

Mud-eel, 338.

Mud-puppy, 339.

Mud-snail, 218.

Mud-wasps, 52.

Mus, 430.

Muscidex, 80.

Muscles, 2.

Musculature, of annelids, 167;
388; cricket, 9;

$4.

birds,

echinoderms, 244 ;
fish, 308; frog, 335; gasteropods,
206; lobster, 125; mammals, 438;
turtles, 355.

Muskallunge, 319.

Musk-turtle, 364.

Mussels, 234; pearl, 235.

Mutation theory, 470.

Mutations, 42S.

Mya arenaria, 231

Myide, 230, 231.

Myriapoda, 92, 97.

Mytilide, 230, 234.

N

Nais, 173.

Nassa, 218.
Natatores, 392.
Natica, 217.

Natural selection, 37.
Nautilus, pearly, 221.
Necturus, 339, 456.
Nematocera, 82.

Nemertini, 190.

Nephelis, 175.

Nereis, 162, 164, 182; food of, 186

Nerve, 2; chord, 289.

Nervous system, of birds, 389;
cricket, 9; echinoderms, 245;
fish, 308; frog, 336; lobster, 126;
mammals, 439; mollusca, 206;
lizard, 3

Nest, of barn swallow, 409; of chim-
ney swift, 402; of pewee, 403.

Nettle animals, 264.

Neuroptera, 27.

Newt, 326, 342; transformation,
326.

Nighthawk, 402.

Noctuids, 45.

Norway rat, migrations of, 431.
Nucleus, 288, 469.

Nuthatch, 413.

Nutrition, functions and organs of, 5;

in echinoderms, 241; fish, 305;
frog, 331; lobster, 122; lizard,
352; mammals, 434.

Nymphs, 40.

O

Obelia, 267, 278.

Odd- toed, hoofed mammals, 445.
Odonata, 25.
Oligochets, 172;
Omnivorous, 17.
Oniscus, 145.
Operculum, annelids, 190; fishes, 304.
Ophidia, 351, 365.
Ophiuoridea, 253.
Opisthobranchs, 212
Opossum, 441.

Oral, 238.
Orang-utan, 449, 450.

Orb-weavers, 106.

Orb-web, structure, 107.

Orbitelarie, 106.

Orca, 443.

Orchard oriole, 405.

Origin of land life, 325.

Organ-pipe coral, 267.

Organs, of circulation, in echinoderms,

terrestrial, 174.

, 220.

243; fish, 307; frog, 333; Mol-
lusea, 203; lizard, 353; excretion,
in birds, 387; echinoderms, 244;
fish, 307; Mollusca, 204; lizard,
354; lobster, 122; nutrition, in
birds, 383; echinoderms, 241;
fish, 305; Mollusca, 200; lizard,
352; respiration, in birds, 385;
echinoderms, 242; zastéropods,

504 INDEX

202; lizard, 354; reproduction, in | Petrel, 395.

birds, 387; fish, 307; Mollusca, ; Petromyzon, 322.

204; lizard, 354. Pewee, 403.
Ornithorhynchus, 439. Phalangidea, 117.
Orthoptera, 15. Pharynx, 295.

Osmerus, 3 Phascolosoma, 176.
Ostracoda, 157. Phasmide, 18.
Ostrea, 237 Pheasants, 394.
Ostreidie, 230, 236. Phoca, 447.
Ostrich, ah Phabe, 40:
Otocyst of lobster, 127. Pholadid:
Otter, 446. Photuri ‘
Ovipositor, 9, 57 Phrynosoma, 357.
Owlet moths, 45. Phy lum, 289.
Owls, 396.
Oxen, 444. sd 272.
Oy -crab, 143. Phy Siplocic ‘al division of labor in
Oyster-drill, 218. Crustacea, 151.
Oysters, 236. Physiology of annelids, 161; Crus-
tacea, 120; Insecta, 1; Mollusea,
Pp 198.
Pici, 400.
Paddle-fish, 324. Pickerel, 319.
Paguridie, 1: 38, Pieris, 40.
Painted turtle, 364. Pigeons, domesticated, 425.
Palsemonetes, 138. Pigs, 444, 445.
Pallene, 119. Pike, 319.
Palm-erab, 140. Pine. Sherer ie
Pandorus, 41. | Pineal gh ind,
Panopeus, 142. | Pipe -fish 21.
Papilio, 40; ajax, 34; asterias, 40; Pipidse 345.

turnus, 40. c es: 450.

Paramecium, 280, 283, 284, 286. , 191, 194.

Parapodia, 188.
Parasitic Hymenopt
281;

era,

57
vertebrates, 322

economic importance of,

Parrot, 397.

Parthenogenctic, 158.

Partridges, 394.

Pate la, 219.
Pauropus, 101.
Pearl-fishing, 235.
Pearl mu

Pecten, 5.
Peectinidee, 230,
Pedicellina, 177.
Pedipalps, 105.
Pelican, 393.
Pelopus, 52.
Perch, 312.
Perchers, 402.
Peripatus, 101.

236.

nger pigeon, 395.
Pe 4

worms,

195.

anar
Planonki
; protista, | Plant- eating Hymenoptera, 59.

215.

| Plant-lice, 24.
| Plastron, 363.
Plethodon, 342.
Plethodontide, 342.
Pleurobranch, 123.
; Pleuron, 123.
| Plovers, 393.
| Plumatella, 178.
Podobranch, 123.
Pogonomyrmex, 55.
, Poisonous spiders, 113.

Polistes, 51.
| Polycheta, circulatory system in,
| 164; respiration in, 164; seden-
| tary, 188.

189.
100.
3b.

Polycirrus,
Polydesmus,
Polymorphism,
Polyp, 273, 275.
Polyphemus moth, 43.
Pond snail, 214.
Porcupine, 446, 448.
| Portuguese man-of-war, 271.

INDEN

Postembryonic
frog, 455.
Posterior, 2.
Potato beetle, 61.
Potato ‘worm,’ 41.
Poultry, domesticated, 425.
Prairie dog, 447.
Prawns, 138.
Praying mantises, 17.
Primates, Be
Proboscis, 32, 293.
Prong-horn, 445,
Promethia moth, 43.
Protection of birds, 417 ;
Protective resemblance,
Protista, 280; cause of dis
parasitic, 281,
Protophyta, 280.
Protoplasm, 1, 469.

development of the

lobster, 135.
Boy Oly Ob:
ases, 281;

Protozoa, 280; discovery of, 282,
465; origin of, 282; reproduction
in, 282.

Psittaci, 397.

Pulmonata 210, 213; aquatic, 214.

Pumpkin-seed sunfish, 313.

Pupa, 31, 32, 214.

Purple grackle, 405.

Q
Quadrate, 304.
Quail, 395.
Quedius, 95.
Queen bee, 50.

R

Rabbits, 424, 446, 448.

Raccoons, 446.

Radii of echinoderms, 239.

Radula, 201.

Rail, 393.

Ranide, 347.

Raptores, 396.

Rat, distribution of, 430; habits of,
431; systematic position of, 432.
Rattlesnakes, 366, 367.

Ray, John, 462.

Rays, 322.

Razor-clams, 231.

Recessive, 429.

Red-eyed vireo, 409.

Red-headed woodpecker, 401.

Redstart, 410; migration of, 373.

Red-winged blackbird, 406.

Reefs, barrier, 277; coral,
fringing, 277.

Regeneration, 454;

QE

earthworms, 170;

505

lost

nhemer-

flatworms, 191; hydra,
parts in Crustacea, 149;
teans, 190.

Reproduction by transverse — divi-
sion, 173; in the cricket, %;
in me immals, 387; in Protozoa,
283.

Reproductive ducts, 2.

Reproductive organs,
166; of birds, 387; of
dermis, 244; of fish, 307;
334; of lobster, 125; of
mals, 437; of lizard, 354.

Reptiles, 350.

Respiration, in annelids, 164 ;

279;

of annelids,
echino-
of frog,

mam-

cricket,

6; fish, 305; lobster, 122; organs
of, in frog, 332; mammals, 456;
lizard, 354.

Rhea, 391.

Rhinoceros, 445.
Rhizopods,
Rice-bird, 406.

Riv er faunas, origin of, 225;
io3e

River mollusks, 225
Robber-flies, 82.

Robin, 413.

Rock eel, 314.

Rodentia, 447.

Roof rat, 430

Rose-breasted grosbeak, 407.
Rose-bug, 70.

Rotifers, discovery of, 465.
Round worms, 191.
Ruby-throated humming-bird, 401.
Running beetles, 62.

Running birds, 391.

Running spiders, 109.

study of,

S

Salamander, 93, 340.
Salmon, 304, 310.
Salmonidee, 309.
Sand-dollars, 2
Sandpipers, 393.
Sandworm, 185.
Sauria, 351, 356.
Sawflies, 59.
Scale, 29.
Scale-bugs, 24.
Scaled- -worms, 187.
Scallop, 235.
Scaly ant-eater,
Searabide, 69.
Scarlet tanager, 408.
Schleiden, 469.

441.

Schultze, 469.

506

Schwann, 469.
Scolopendra, 99.
Scolopendrella, 101.
Scolytide, 71.
Scorpions, 116.
Scratchers, 394.
Screech owl, 397.
Sculpin, 313.
Scutigera, 98.
Scyphozoa, 27:
Sea-anemones,
Sea-cows, 442.
Sea-cucumber, 258.
Sea-lilies, 258.
Sea-lion, 446.
Sea-mouse, 186, 187.
Sea-spiders, 119
Sea-urchins, .
Sea walnuts,
Seal, 446.
Searcher, 64.
Segmentation, of body
162.
Segmented animals, 290.
Selachians, 322.

INDEX

of annclids,

Sense-organs of — annelids, 167;

birds, 389; crickets,

oderms, 245: fish, 308;

lobster,

hee o
; Mollusca, 2

mals, 4
Serpent, *
Serpent-st ars, 253.
Serpula, 18
Sertularia, 268, 278.
Sexton beetles, 67.
Sexual dimorphism, 113.

10; echin-
frog, 338;
126; mam-
06.

Shad, 319; fishing, value of, 320.

Sharks, 322,

Sharp- shinned hawk, 397.
Shell, rudimentary, in cephalopods,

221.
Sheep, 424, 444.
Sheep-tic k, Ss.

Short-horned Diptera, 80.
Short-horned grasshoppers, 13.

Short-winged beetles, 66.
Shrews, 445.
Shrikes, 409.

Shrimps, 138; burrowing, 138.

39, 42; cultu

Silphide,
Silverside: ‘Ss, 314.
Simia, 449.
Siphonata, 227.
Siphonophore, 271.
Siren, 338.
Skeleton,

1; birds, 380;
lizard, 352; mammals,

re of, 43.

frog, 329;
433.

Skunk, 446.

Skylark, 404.

Sloth, 441.

Slow-worms, 360.

Slug, 208, 210; apparent absence of
shell of, 211; economical impor-
tance of, 211: food of, 211; habi-
tat of, 211.

Smallest organisms, a study of, 280.

Smelt, 298, 309; economic impor-
tance of, 309.

Snail, 198; form of body, 198; mus-
culature of, 206.

Snake, 365.

Snapping-turtle, 364.

Snipe, 394.

Snowbird, 407.

Snowy owl, 397.

Social bees, 49.

Social life of ants, 55.

Soft-shelled clams, ie

Soft-shelled turtle, 363.

Solenide, 230, 231.

Somites, 3, 4.

Song-sparrow, 407.

Song thrush, 413.

Sow-bugs, 145.

Spanish fly, 75.

Sparrow, 406; English, 370.

Sparrow ‘hawk, 396.

Spelerpes, 93, 344.

Sphingide, 41.

Spider, 102, 104; cave, 96; position
of in zoological system, 114; webs,
economic importance of, 112.

Spider-crabs, 140.

Spinnerets, 104.

Spinning instinct, uses of, 110;
methods of, in spiders, 112.

Spiny ant-eater, 439.

Spiracles, 3; of cricket, 6.

Sponges, 262.

Spontaneous generation, theory of,
989.

Spoonbill, 324.

Spore animalcules,

Sporozoa, 285;
285.

Spotted sandpiper, 393.

Spreading adder, 365

Spread of English sparrow in Amer-
ica, 374.

Spring azures, 34, 41.

Spring-tails, 92, 96.

Squash- bugs, 22:

Squids, 220.

Squirrel, 446, 447.

Stag-beetles, 68.

of malaria,

INDEX 507
Staggers of sheep, 82. Tibia, 5.
Staphylinide, 66. Ticks, 117.

Starfish, 246; abnormalities of, 251;
development, 247; distribution,
251; habitat, 251; serpent-stars,
253; study of embryology, 246;
systematic position of, 251.

Stegomyia, 86.

Stentor, 287.

Sterna, 392.

Stickleback, 315.

Sting of scorpions, 116,

Stink-bugs 2

Stolons, 279.

Stomach of crickets, 6.

Stomapoda, 144.

Storks, 393.

Strongylocentrotus, 256.

Sturgeons, 323.

Stylactis, 266.

Subterrestrial organisms, 168.

Suckers, 317.

Suctoria, 288.

Sunfish, 313.

Swallow, 407.

Swallow-tails, 40.

Swammerdam, 464.

Swarming of bees, 50.

Swifts, 401.

Swimming birds, 392.

Sycon, 263.

Synapta, 259.

Syrphide, 82.

Tabanus, 83.

Teenia, 197.

Talorchestia, 146.

Tanagers, 407.

Tapeworm, 195, 197.

Tapirs, 445.

Tarantula, 113.

Tarsus, 5.

Teeth, amphibia, 331; birds, 419;
echinoderms, 242; fish, 304, 305;
mammals, 435.

Tentacles, 271.

Tent-caterpillar, 44-46.

Teredide, 230.

. Termites, 26, 52.

Tern, 392.

Testudinide, 363.

Thalassinide, 138.

Theclas, 41.

Theory of evolution, 469.

Thomisus, 112.

Thorax, 3.

Thrushes, 413,

Tiger, 446.

Tiger-beetles, 61, 63.

Tiger-moths, 42.

Tiger swallow-tails, 40.

Tineids, 47.

Tipulide, 87.

Titmice, 413.

Toad, 347.

Toadfish, 313.

Tomato worm, 35, 41.

Tortricids, 47.

Toucans, 399.

Trachea, 13, 80; of cricket, 6.

Tree-hopper, 24.

Tree-sparrow, 407.

Tree-toad, 345.

Trichina, 191.

Trilobite, 160.

Trionyx, 363.

Trochilus, 401.

Troglodytes, 413.

Trout, 310.

True bugs, 22.

Trunk, 3.

Tsetse-fly, 80.

Tube-weavers, 105.

Tubifex, 172.

Tubularian hydroids, 267.

Tubularide, 267.

Tumble-bugs, 69.

Tunicates, 290.

Tunnel-weavers, 105.

Turdus, 415.

Turkey, 395.

Turkey-buzzard, 396.

Turtles, 351, 362; general form of
body, 352; marine, 362; muscular
system of, 355; nervous system
of, 355; organs of circulation, 353 ;
excretion, 354; nutrition, 352; re-
production, 354; respiration, 354;
sense-organs, 355; skeleton, 352.

Tussock moth, 46.

Twin-spotted sphinx, 41.

Tyrannid, 402.

U

Unionide, 228.

Unios, 228; development of, 229;
economic value of, 229; spawning
season, 229.

Urodela, 328,
ment of, 343.

Urosalpinx, 218.

Uses of spinning instinct, 110,

338; early develop-

008
y

Varanidee, 358.
Variability of Helix, 214.

Veneridwe, 230, 232.

Ventral, 2.

Venus, 53:

Vertebr: ates s, 302; ancestry
296.

Vesalius, 461.

Vespa, 51.

Ves arrow, 407.

Viceroy, 37, 40.
Vinegar eel, 191.
Vireos, 409.
Volvox, 286

Vultures

W
Waders, 393.
Walking-stick, 18.
Walrus, 446.

Wampum, 234.
Wandering spiders,
Warbler, 410.
Wasps, 51.
Water-boatman, 22.
Water-flea, 157.
Water-lizard, 358.
Water scavenger- beetle, 65.
Water- -scorpion,
Water snake, 365
Water-striders, 22.
Water-vascular system
derms, 240.
Waste products, 7
Waxwings, 409,
Ve

109.

in

Jeevils,
‘Whales,
Ww hippoorwill, 402.
Whirligig beetles, 65.

£95, 443.

INDEX

of, 289,

echino-

| White ant, 26
| White

sh, 310.
White-throated sparrow,
Wigglers, 85.

Wing, butterfly, 33.

Wing-cells, 5.

Wing-veins, 5.

Wineless birds,
17;

Wireworms,

Wolf, 446.

Wolff, 468.

Wolf spiders, 109.

Woodcock, 394.

Wood-feeders, 42.

Wood-lice, 145.

Woodpeckers, 400.

Wood-warbler, 410.

Wool-bectle, 68.

Worker bee, 50.

Worm, earth, 169-172;
190-195; ringed, 161;
sealed, 187; stomach,
195.

Wren, 410.

407.

391; cockroaches,

70.

parasitic,
sand, 185;
191; tape,

xX
Xylotropids, 42.

¥:

Yellow fever, 281.
Yellow warbler, 410.
Yoldia, 235.

Z

Zebra, 445.
Zebra swallow-tail, 34.
ZLooids, 271, 279, 291.
Zoological expeditions, 471;
465.
Zoology, 458 ;

gardens,
anatom-

463;
phil )-

foundation of,
ical, 463; morphological,
history of science of, 458;
sophical, 466.

Zygodactyla, 271.

HIGH SCHOOL COURSE
IN LATIN COMPOSITION

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