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ELEMENTARY ZOOLOGY

BY

VERNON? L. KELLOGG, M.S.

Professor of Entomology, Leland Stanjord Junior University

SECOND EDITION, REVISED

NEW YORK
HENRY HOLT AND COMPANY

1902

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THE LIBRARY OF
CONGRESS,
Two Copies REceiveo

JUN. 11 1902 |

COPYRIGHT ENTRY

Copyright, roor,

BY
HENRY HOLT & CO.

PREFACE

IT seems to the author that three kinds of work should
be included in the elementary study of zoology. These
three kinds are: (2) observations in the field covering
the habits and behavior of animals and their relations
to their physical surroundings, to plants, and to each
other ; (4) work in the laboratory, consisting of the study
of animal structure by dissection and the observation of
live specimens in cages and aquaria; and (c) work in the
recitation- or lecture-room, where the significance and
general application of the observed facts are considered
and some of the elementary facts relating to the classifi-
cation and distribution of animals are learned.

These three kinds of work are represented in the course
of study outlined in this book. The sequence and extent
of the study in laboratory and recitation-room are defi-
nitely set forth, but the references to field-work consist
chiefly of suggestions to teacher and student regarding
the character of the work and the opportunities for it.
Not because the author would give to the field-work the
least important place, —he would not,—but because of the
utter impracticability of attempting to direct the field-
work of students scattered widely over the United States.
The differences in season and natural conditions in vari-
ous parts of the country with the corresponding differences

in the ‘‘seasons’’ and course of the life-history of the
lil

1V PREFACE

animals of the various regions make it impossible to in-
clude in a book intended for general use specific direc-
tions for field-work. Further, the amount of time for
field-work at the disposal of teacher and class and the
opportunities afforded by the topographic character of the
region in which the schools are located vary much. The
initiation and direction of this must therefore always de-
pend on theteacher. On the other hand, the work of the
other two phases of study can to a large extent be made
pretty uniform throughout the country. For dissection,
specimens properly killed and preserved are about as
good as fresh material, and by modifying the suggested
sequence of work a little to suit special conditions or con-
veniences, the examination of live specimens in the
laboratory can in most cases be accomplished.

The author believes that elementary zoological study
should not be limited to the examination of the struc-
ture of several types. Ihe student should” lear by
observation something of the functions of animals and
something of their life-history and habits, and should be
given a glimpse of the significance of his particular ob-
servations and of their general relation to animal life as a
whole. The drill of the laboratory is perhaps the most
valuable part of the work, but as a matter of fact the high
school is trying to teach elementary zoology, an ele-
mentary knowledge of animals and their life, and dissec-
tion alone cannot give the pupil this knowledge. On the
other hand, without a personal acquaintance with animals,
based on careful actual observations of their life-history
and habits and on the study of the structural characters of
the animal body by personally made dissections, the
pupil can never really appreciate and understand the life
of animals. Reading and recitation alone can never
give the student any real knowledge of it.

The book is divided into three parts, of which Part I

PREFACE v

should be™* first undertaken. This is an introduction to
an elementary knowledge of animal structure, function,
and development. It consists of practical exercises in
the laboratory, each followed by a recitation in which the
significance of the facts already observed is pointed out.
The general principles of zoology are thus defined on a
basis of observed facts.

Part II is devoted to a consideration of the principal
branches of the animal kingdom; it deals with t system-
atic zoology. In each branch one or more examples
are chosen to serve as types. The most important struc-
tural features of these examples are studied, by dissection,
in the laboratory. The directions for these dissections
consist of technical instructions for dissecting, the calling
attention to and naming of principal parts, together with
questions and demands intended to call for independent
work on the part of the student. The directions follow
the actual course of the dissection instead of being ar-
ranged according to systems of organs, and are intended
for the orientation of the student and not to be in them-
selves expositions of the anatomy of the types. The
condensation of these directions is made more feasible by
the presence of anatomical plates (drawn directly from
dissections). Following the account of the dissection of
the type are brief notes on its life-history and habits.

* This is true if a strictly logical treatment of the subject is held to. As
a matter of fact, it is often of advantage to begin with, or at least to take up
from the beginning in connection with the indoor work, some field-work,
such as the collecting and classifying of insects and the observation of
their metamorphosis. As most schools begin work in the fall, advantage
must be taken of the favorable opportunities for field-work at the beginning
of the year. These opportunities are of course much less favorable in the
winter.

+ The classification of animals used in this book is that adopted in
Parker and Haswell’s ‘‘ Text-book of Zoology ” (2 vols., 1897, Macmillan
Co.). Exception is made in the case of the worms, which are considered
as a single branch, Vermes, instead of as several distinct branches.

vl PREFACE

Then follows a general account of the branch to which
the example dissected belongs and brief accemmes of
some of the more interesting members of the branch. In
these accounts technical directions are given for brief
comparative examinations and for the study of the life-
history and habits of some of the more accessible of
these forms. ; |

It will not be possible, of course, to undertake with any
thoroughness the consideration of all of the branches of
animals in a single year. But all are treated in the book,
so that the choice of those to be studied may rest with the
teacher. This choice will of necessity depend largely on
the opportunities afforded by the situation of the school,
as, for example, whether on the seashore or in the interior
near a lake or river, or on the dry plains, and on the re-
lation of the school-terms to the seasons of the year.
The branches are arranged in the book so that the sim-
plest animals are first considered, the slightly complex
ones next, and lastly the most highly organized forms.
But if in order to obtain examples for study it is necessary
to take up branches irregularly, that need not prove con-
fusing. The author would suggest that whatever other
branches are studied, the insects and birds, which are
readily available in all parts of the country, be certainly
selected, and with this selection in view has given them
special attention. Indeed some teachers may find these
two branches to offer quite sufficient work in classificatory
and ecological lines.

Part III is devoted to a necessarily brief consideration
of certain of the more conspicuous and interesting
features of animal ecology. It has in it the suggestion
for much interesting field-work. The work of this part
should be taken up in connection with that of Part II, as,
for example, the consideration of social and communal
life in connection with the insects, parasitism in connec-

PREFACE Vil

tion with the worms, and also with the insects, distribu-
tion in connection with the birds, perhaps, and so on.

In appendices there are added some suggestions for
the outfitting of the laboratory, and a list of the equip-
ment each student should have. Here, also, is appended
a list of a few good authoritative reference books which
should be accessible to students and to which specific
references are made in the course of this book. Some
practical directions for the collecting and preserving of
specimens are also given. (Suggestions for the obtaining
of material for the various laboratory exercises outlined
imethe beok are ‘to be found in “‘ technical notes
Gucded m the directions for each exercise.) The author
believes that the building up of a single school-collection

ey

wis

in which all the pupils have a common interest and to
which all contribute is to be encouraged rather than the
making of separate collections by the pupils. Waste of
life is checked by this, and in time, with the contributions
of succeeding classes, a really good and effective collec-
fon. may be built. up.- The ‘‘ collecting interest.”” can
be taken advantage of just as well in connection with a
school-collection as with individual collections.

The plates illustrating the dissections have all been
drawn originally for the book from actual dissections.
Most of the other figures are original, either drawn or
photographed directly from nature, or from preserved
Specimens. Credit is given in ‘each case for figures not
original. The drawings for all of the figures of dis-
sections and for all original figures not otherwise accred-
ited were made by Miss Mary H. Wellman, to whom the
author expresses his obligations. The thanks of the
sminen are due to Mr. George Otis Mitchell, San Fran-
cisco, who kindly made the photo-micrographs of insect
structure from. the author’s slides; to Professor Mark V.
Slingerland, Cornell University, for electros of his photo-

Vill PREFACE

graphs of insects; to Dr. L. O. Howard, U. S. Entomol-
ogist,. for electros of figs. 45, $2, $6, GS, ssa, a)
84, 87,90, and 92; to Professor L. L. Dyche, University
of Kansas, for photographs of his mounted groups of
mammals; to Mrs. Elizabeth Grinnell, Pasadena, Calif. ,
for photographs of birds; to Mr. J. O. Snyder, Stanford
University, for photographs of snakes; to Mr.- Frank
Chapman, editor of ‘‘ Bird-lore,’’ for electros of photo-
eraphs of birds; to Mr. G. O. Shields, editor of ‘‘ Recrea-
tion,’’ for an electro of the photograph of a bird; to the
American Society of Civil Engineers for electros of photo-
graphs of boring marine worms; to Cassell & Co., for
electros of three photographs from nature; to Geo. A.
Clark, secretary Fur Seal Commission for photographs of
seals; and to the Whitaker and Ray Co., Sam Pf ¢anecisco;
for: electros.of figs. 46, 59). 60, 61, 64, 65,°63, 04,07 G5,
99, 100, 102, II9, and 166 to 172, published originally in
Jenkins & Kellogg’s ‘‘ Lessons in Nature Study.’’ The
origin of each of these pictures is specifically indicated in
connection with its use in the book.

The author.s sincere thanks are also due to Mrs. David
Starr Jordan and to Mr. J. C. Brown, graduate student in
zoology in Stanford University, for their assistance in the
correction of the MS., and in the preparation of the lab-
oratory exercises respectively. The chapters-of Part i
relating to the vertebrates were read in MS. by President
David Starr Jordan, whose aid and courtesy are gratefully
acknowledged. Similar acknowledgments are due Pro-
fessors Harold Heath and R. E. Snodgrass for read-
ing the proofs of the directions for the laboratory ex-
ercises.

VERNON LYMAN KELLOGG.

STANFORD UNIVERSITY, May, 1901.

CONTENTS

PARF |

See weTORE, FUNCTIONS, AND DEVELOPMENT OF
ANIMALS

L=THE STUDY OF ANIMALS AND THEIR LIFE.

Our familiar knowledge of animals and their life, 1.—Zoology and its
divisions, 2.—A first course in Zoology, 3.

Il.— THE GARDEN TOAD (Buro LENTIGINOosUS).

[Laboratory exercise], 5.—External structure, 5.—Internal structure, 7.

Iil.—-THE STRUCTURE AND FUNCTIONS OF THE ANIMAL BODY.

Organs and functions, 14.—The animal body a machine, 14.—-The essen-
tial functions or life-processes, 15.

IV.—THE CRAYFISH (CaMBARUS SP.).

| Laboratory exercise], 17. External structure, 17.—Internal structure, 21.

V.—THE MODIFICATION OF ORGANS AND FUNCTIONS.

Difference between crayfish and toad, 26.—Resemblances between cray-
_ fish and toad, 27.—Modification of functions and structure to fit the animal
to the special conditions of its life, 29. — Vertebrate and invertebrate, 30.

VI.—AM@BA AND PARAM(:CIUM.

[Laboratory exercise], 31.—Ameeba, 31.—The slipper-animalcule (PARA-
MCECIUM SP.), 34.
1X

x CONTENTS

VIIl.—THE SINGLE-CELLED ANIMAL BODY; PROTOPLASM
AND) PE Ceres

The single-celled animal body, 36.—The cell, 37.—Protoplasm, 39.

VIl.—CELLULAR STRUCTURE OF THE TOAD (OR FROG).

[Laboratory exercise], 40.—The blood, 40.—The skin, 40.—The liver.
41.—The muscles, 41.

IX.--THE MANY-CELLED ANIMAL BODY; DIFFERENTIATION
OF a Cpirie

The many-celled animal body, 43.—Differentiation of the cell, 43.

X.—HYDRA.
[Laboratory exercise], 46.

XI.—THE SIMPLEST MANY-CELLED ANIMALS.

Cell-differentiation and body-organization in Hydra, 52.—Degrees in
cell-differentiation and body-organization, 54.

XI.— DEVELOPMENT OF THE TOAD:
[ Field and laboratory exercise], 55.

XII.—MULTIPLICATION AND DEVELOPMENT.

Multiplication, 57.—Spontaneous generation, 58.—Simplest multiplica-
tion and development, 59.—-Birth and hatching, 61.—Life-history, 62.

Pa Al
SYSTEMATIC .ZOOLOGY

XIV.—THE CLASSIFICATION OF ANIMALS.

[Laboratory exercise and recitation], 65.—Basis and significance of
classification, 65.—Importance of development in determining classification,
67.—Scientific names, 68.—An example of classification, 68.—Species,
69.— Genus, 70.—Fanmuly,. 72.— Order, 72.—Class and braneh)72:

XV.—BRANCH PROTOZOA: THE ONE-CELEED Anis:

EXAMPLE: THE BELL ANIMALCULE (VORTICELLA SP.) [Laboratory
exercise), 75.

OTHER PROTOZOA.

Form of body, 78.—Marine Protozoa, 890,

CON FEN TS x1

7k BRANCH PORTFERA:; THE SPONGES.

EXAMPLE: THE FRESH-WATER SPONGE (SPONGILLA SP.) [Laboratory
exercise], 84.

EXAMPLE: A CALCAREOUS OCEAN-SPONGE (GRANTIA Sp.) [Laboratory
exercise], 85.

EXAMPLE: A COMMERCIAL SPONGE [Laboratory exercise], 86.

OTHER SPONGES.

Form: and size, 87.—Skeleton, 88.——Structure of body, 88.—Feeding
habits, 88.—Development and life-history, 89.—The sponges of commerce,
90.—Classification, 9I.

mvt —_ BRANCH CCELENTERATA: THE-POLYPS, SEA-
mmEMONES, CORALS, AND JELEVFISHES.

POLYPS, SEA-ANEMONES, CORALS, AND JELLYFISHES.

General form and organization of body, 93.—Structure, 94.—Skeleton,
95.—-Development and life-history, 95.—Classification, 96.—The polyps,
colonial jellyfishes, etc. (Hydrozoa), 97.—The large jellyfishes, etc.
(Scyphozoa), 101.—The sea-anemones and corals (Actinozoa), 102.—The
Ctenophora, 107.

tt BRANCH ECHINODERMATA: -THE STARFISHES, “SEA:
WRCHENS. SEA CUCUMBERS, ELE.

EXAMPLE: STARFISH (ASTERIAS Sp.) [Laboratory exercise ].—External.
structure, 108.— Internal structure, 110.—Life-history and habits, 113.

EXAMPLE: SEA-URCHIN (STRONGYLOCENTRUS SP.) [Laboratory exercise].
-—External structure, 113.

OTHER STARFISHES, SEA-URCHINS, SEA-CUCUMBERS, ETC.

Shape and organization of body, 116.—Structure and organs, 117.—De-
velopment and life-history, I119.—Classification, 120.—Starfishes (Asteroi-
dea), 121.—-Brittle stars (Ophiuroidea), 122.—Sea-urchins (Echinoidea),
123.—Sea-cucumbers (Holothuroidea), 124.—Feather-stars (Crinoidea), 125.

XIX.—BRANCH VERMES: THE WORMS.

EXAMPLE: THE EARTHWORM ‘LuMBRICUuS sP.) [Laboratory exercise].—
External structure, 127.—Internal structure, 129.—Life-history and habits,
F223:

OTHER Worms.

Classification, 135.—Earthworms and leeches (Oligochete, 136.—Flat
worms (Platyhelminthes). £37.—Round worms (Nemathelminthes), 140,—~—
Wheel-animalcules (Rotifera), 142.

x11 CONTENTS

XX.—BRANCH ARTHROPODA: THE CRUSTACEANS, CEN-
TIPEDS, INSECTS, AND SPIDERS.

Crass CRUSTACEA: CRAYFISHES, CRABS, LOBSTERS, ETC.

EXAMPLE; THE CRAYFISH (CAMBARUS SP.). Structure, 146.—Life-his-
tory and habits, 146.

OTHER CRUSTACEANS.

Body form and structure, 147.—-Water-fleas (Cyclops), 148.—Wood-lwe
(lsopoda), 150.—Lobsters, shrimps, and crabs (Decapoda), 151.—-Barnacles,

155.

XXI.—BRANCH ARTHROPODA (CONTINUED),

Ciass INSECTA: THE INSECTS.

EXAMPLE: THE RED-LEGGED LOCUST (MELANOPLUS FEMUR-RUBRUM),
[Laboratory exereise]. External structure, 157.—Life-history and habits,
161.

EXAMPLE: THE WATER-SCAVENGER BEETLE (HYDROPHILUS Sp.) [Labo-
ratory exercise]. External structure, 163.—Internal structure, 166.—Life-
history and habits, 169. |

EXAMPLE: THE MONARCH BUTTERFLY (ANOSIA PLEXIPPUS) [Laboratory
exercise]. External structure, 171.—Life-history and habits, 175.

EXAMPLE: LARVA OF MONARCH BUTTERFLY [Laboratory exercise].
Structure; 177.

OTHER INSECTs. ,

Body form and structure, 181.—Development and life-history, 188. —
Classification, I91.—Locusts, cockroaches, crickets. etc. (Orthoptera), 192.
—The dragon-flies and May-flies (Odonata and Ephemerida), 194.—The
sucking-bugs (Hemiptera), 197.—The flies (Diptera), 201.—The butterflies
and moths (Lepidoptera), 205.—-The beetles (Coleoptera), 206.—The
ichneumon flies, ants, wasps, and bees (Hymenoptera), 212.

Crass MyRIAPOoDA: THE CENTIPEDS AND MILLIPEDS.

CLass ARACHNIDA: THE SCORPIONS, SPIDERS, MITES, AND TICS.

XXIL=-BRANCH MOLLUSCA: THE MOELUSe=:

EXAMPLE: THE FRESH-WATER MUSSEL (UNIo sp.) [Laboratory exercise].
Structure, 239.—Life-history and habits, 243.

OTHER MOoL.Luscs,

Body form and structure, 245.—Development, 246.—Classification, 246.
—Clams, scallops, and oysters (Pelecypoda), 246.—Snails, slugs, nudi-
branchs, and ‘‘sea-shells’’ (Gastropoda), 252.—Squids, cuttlefishes, and
octopi (Cephalopoda), 255.

CONTENTS X1ll

XXIII.—BRANCH CHORDATA: THE ASCIDIANS, VERTE-
BRATES, ETC.

Structure of the vertebrates, 259.—Classification of the Chordata, 260.—
The ascidians, 261.

XXIV.—BRANCH CHORDATA (CONTINUED).

Crass Pisces: THE FIsHEs.

EXAMPLE: THE GOLDEN SUNFISH -EUPOMOTIS GIBBOsUS) [Laboratory
exercise]. External structure, 263.— Internal structure, 265.—Life-history
and habits, 270.

OTHER FISHES.

Body form and structure, 271.—Development and life-history, 276.—
Classification, 277.—The lancelets (Leptocardii), 277.—The lampreys and
hag-fishes (Cyclostomata), 278.—The true fishes (Pisces), 279. —The sharks,
skates, etc. (Elasmobranchii), 279.—The bony fishes (Teleostomi), 281.—
Habits and adaptations, 285. —Food-fishes and fish-hatcheries, 288.

XXV.—BRANCH CHORDATA (CONTINUED).

CLAss BATRACHIA: THE BATRACHIANS.

Body form and organization, 292.— Structure, 293.—Life-history and
habits, 295.—Classification, 297.— Mud-puppies, salamanders, etc. (Uro-
dela), 297.—Frogs and toads (Anura), 299.—Ccecilians (Gymnophiona),
302.

XXVI.—BRANCH CHORDATA (CONTINUED).

CLASS REPTILIA: THE SNAKES, LIZARDS, TURTLES, CROCODILES, ETC.

EXAMPLE: THE GARTER SNAKE (THAMNOPHIS SP.) [Laboratory exer-
cise]. Structure, 303.—Life-history and habits, 308.

OTHER REPTILES.

Body form and organization, 310.—Structure, 311.—Life-history and
habits, 312.—-Classification, 313.—Tortoises and turtles (Chelonia\, 314.—
Snakes and lizards (Squamata’, 317.—Crocodiles and alligators (Croco-
dilia), 325.

XXVII.—BRANCH CHORDATA (CONTINUED).

Cxiass AVES: THE BirpDs.

EXAMPLE: THE ENGLISH SPARROW (PASSER DOMESTICUS) [Laboratory
exercise]. External structure, 327.—Internal structure [Laboratory exer-
cise], 329.—Life history and havits, 335.

OTHER BIRDs.

Body form and siruciure, 336.— Development and life-history, 339.—-
Classification. 340.— The ostriches, cassowaries, etc. (Ratitz), 341.—The

XIV CONTENTS

loons, grebes, auks, etc. (Pygopodes), 343.—The gulls, terns, petrels, and
albatrosses (Longipennes), 345.—The cormorants, pelicans, etc. (Stegano-
podes), 346.—The ducks, geese, and swans (Anseres), 347.—The ibises,
herons, and bitterns (Herodiones), 347.—The cranes, rails, and coots (Palu-
dicolee), 348.—The snipes, sand-pipers, plovers, etc. (Limicolz), 349.—
The grouse, quail, pheasants, turkeys, etc. (Gallinz), 358.—The doves and
pigeons (Columbe), 351.— The eagles, hawks, owls, and vultures (Raptores),
351.—The parrots (Psittaci), 353.—The cookoos and kingfishers (Coccyges),
354.—The woodpeckers (Pici), 354.—-The whippoorwills, chimney-swifts,
and humming-birds (Macrochires), 356.—The perchers (Passeres), 357. —
Determining and studying the birds of a locality, 359.—Bills and feet, 362.
—F light and songs, 364.—Nestling and care of the young, 366.—Local dis-
tribution and migration, 367.—-Feeding habits, economics, and protection of
birds370:

XX VIIL—BRANCH CHORDATA (CONTINUED

Ciass MAMMALIA: THE MAMMALS. |

EXAMPLE : THE Mouse (Mus MuscuLus) [Laboratory exercise]. Struc-
ture, 373.—Life-history and habits, 379.

OTHER MAMMALS.

Body form and structure, 381.—Development and life-history, 337.—
Habits, instincts, and reason, 387.— Classification, 388.—The opossums
(Marsupialia), 389.—The rodents or gnawers (Glires), 390.—The shrews
and moles (Insectivora), 391.—The bats (Chiroptera), 391.—The dolphins,
porpoises, and whales (Cete), 393.—The hoofed mammals (Ungulata), 394.
—The carnivores (Ferz), 396.—The man-like mammals (Primates), 398.

PART a
ANIMAL ECOLOGY

XXIX.—THE STRUGGLE FOR EXISTENCE, Aaa ain:
AND SPECIES-FORMING.

The multiplication and crowding of animals, 404.—The struggle for
existence, 406.—Variation and natural selection, 406.—Adaptation and
adjustment to surroundings, 407.— Species forming, 408.—Artificial selec-
tion, 409.

XXX.—-SOCIAL AND: COMMUNAL LIFE, COMMENS eism” AND
PARASITISM.

Social life and gregariousness, 410.—Communal life, 411.—Commen-

salism 413.—Parasitism, 415.

CONTENTS XV

XXXI.—COLOR AND PROTECTIVE RESEMBLANCES.

Use of color, 424. —General, variable, and special protective resemblance,
426.—Warning colors, terrifying appearances, and mimicry, 430.—Alluring
coloration, 433.

XXXII.—THE DISTRIBUTION OF ANIMALS.

Geographical distribution, 435.—Laws of distribution, 437.—Modes of
migration and distribution, 437.—Barriers to distribution, 438.— Faun
and zoogeographic areas, 440.—Habitat and species, 441.—Species-extin-
guishing and species-forming, 442.

ee EN DICES
EQUIPMENT AND METHODS

APPENDIX 1.—EQUIPMENT AND NOTES OF PUPILS.
Equipment of pupils, 447.—\-Laboratory drawings and notes, 447.—Field
observations and notes, 448.

APPENDIX II.—LABORATORY EQUIPMENT AND METHODS.

Equipment of laboratory, 450.—Collecting and preparing material for use
in the laboratory, 451.—Obtaining marine animals, microscopic prepara-
tions, etc., 453.—Reference-books, 454.

APPENDIX JIJI.—REARING ANIMALS AND MAKING COLLEC-
TIONS.

Live cages and aquaria, 457.— Making collections, 461.—Collecting and
preserving insects, 463.—Collecting and preserving birds, 466.—Collecting
and preserving mammals, 470.—Collecting and preserving other animals,

472.

PART |

STRUCTURE, FUNCTIONS, AND DEVELOP-
MENT OF ANIMALS

CHAPFER 1
Pees sew Y OF ANIMALS AND THEIR LIFE

Our familiar knowledge of animals and their life.—
We are familiarly acquainted with dogs and cats; less
familiarly probably with toads and crayfishes, and we
have little more than a bare knowledge of the existence
of such animals as seals and starfishes and reindeer. But
what real knowledge of dogs and toads does our familiar
acquaintanceship with them give? Certain habits of the
dog are knotyn to us: it eats, and eats certain kinds of
food; it runs about; it responds to our calls or even to
the mere sight of us; it evidently feels pain when struck,
and shows fear when threatened. Another class of
attributes of the dog includes those things that we know
of its bodily make-up: its possession of a head with eyes
and ears, nose and mouth; its four legs with toes and
claws; its covering of hair. We know, too, that it was
born alive as a very small helpless puppy which lived for
a while on food furnished by the mother, and that it has
grown and developed from this young state to a fully
srown, fully developed dog. We know also that our
_ dog is a certain kind of dog, a spaniel, perhaps, while

2 ELEMENTARY ZOOLOGY

our neighbor's dog is of another kind, a greyhound, it
may be. We know accordingly that there are different
kinds of tame dogs, and we may know that wolves
are so much like dogs that they might indeed be
called wild dogs, or dogs called a kind of tame wolf.
But how little we really know about the dog’s body and
its life is apparent at a moment’s thought. We see only
the outside of the dog, but what an intricate complex of
parts really composes this animal! We see it eat and
breathe and run; of what is done with the food and air
inside its body, and of the series of muscle contractions
-and mechanical processes which cause its running, we have
but the. slightest conception. “We see that the pup gets
larger, that is, grows; that it changes gradually in appear-
ance, that is, develops; but of the real processes and
changes that take place in growth and development how
little we know! We know that there are other kinds of
dogs; that wolves and foxes are relatives of the dog; and
we have heard that cats and tigers are relatives also,
although more distant ones. We know, too, that all the
backboned animals, some of them very unlike dogs, are
believed to be related to each other, but of the thousands of
these animals and of their relationships our knowledge is
scanty. Finally, of the relations of the dog, and of other
animals, to the outside world, and of the wonderful man-
ner in which the dog’s make-up and behavior fit it to live
in its place in the world under the conditions that surround
it, we have probably least knowledge of all.

Zoology and its divisions.—What things we do know
about the dog, however, and about its relatives, and
what things others know, can be classified into several
groups, namely, things or facts about what the dog does,
or its behavior, things about the make-up of its body,
things about its growth and development, things about
the kind of dog it is and the kinds of relatives it has, and

GHEo STUDY. OF ANIMALS. AND: THEIR~ LIFE 3

things about its relations to the outer world, and its special
fitness for life.

All that is known of these different kinds of facts about
the dog constitutes our knowledge of the dog and its life.
All that is known by scientific men and others of these
different kinds of facts about all the 500,000 or more kinds
of living animals, constitutes our knowledge of animals and
is the science zoology.* Names have been given to these
different groups of facts about animals. The facts about
the bodily make-up or structure of animals constitute that
part of zoology called animal azatomy or morphology, the
facts about the things animals do, or the functions of
animals, compose animal physiology, the facts about the
development of animals from young to adult condition are
the facts of animal development; the knowledge of the
different kinds of animals and their relationships to each
other is called systematic zoology or animal classification;
and finally the knowledge of the relations of animals to
their external surroundings, including the inorganic world,
plants and other animals, is called animal ecology.

Any study of animals and their life, that is, of zoology,
may include all or any of these parts of zoology. Most
zoologists do, indeed, devote their principal attention to
some one group of facts about animals and are accordingly
spoken of as anatomists, or physiologists, systematists,
and soon. Sut such a specialization of study should be
made only after the zoologist has acquired a knowledge
of the principal or fundamental facts in all the other
branches of zoology.

A first course in zoology.—The first ‘‘course,’’ then,
in the study of animals should include the fundamental
facts in all these branches or parts of zoology. That is
what the course outlined in this book tries to cover.

* Zoology is formed from two Greek words: zoom, meaning animal, and
Jogos, meaning discourse.

4 ELEMENTARY ZOOLOGY

But no text-book of zoology can really give the student
the knowledge he seeks. He must find out most of it for
himself; a text-book, based on the experiences of others,
is chiefly valuable for telling him how to work most
effectively to get this knowledge for himself. And the
best students always find out things which are not in books.
Especially can the beginning student find out things not
known before, ‘‘new to science,’’ as we say, about the
behavior and habits of animals, and their relations to their
surroundings. The life-history of comparatively few kinds
of animals is exactly known; the instincts and habits of
comparatively few have been studied in any detail. The
kinds of food demanded, the feeding habits, nest-building,
care of the young, cunning concealment of nest and self,
time of egg-laying or of producing young, duration of the
immature stages and the habits and behavior of the young
animals—a host, indeed, of observations on the actual life
of animals, remain to be made by the “ teld naturalich
Any beginning student can be a ‘‘field naturalist ’’ and
can find out new things about animals, that is, can add
to the science of zoology.

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CHAPTER 41

THE GARDEN TOAD (8x0 lentiginosus)

LABORATORY EXERCISE

TECHNICAL NOTE.—Although this description is written for the
toad it will fit for the dissection of the frog. It will be found, after
casting aside a few ungrounded prejudices, that the toad is the
better for class dissection. Toads are best collected about dusk,
when they can be picked up in almost any garden in town or in the
country. During the spring many can be found in the ponds where
they are breeding. To kill the toad place it in an air-tight vessel
with a piece of cotton or cloth saturated in chloroform or ether.
When the toad is dead, wash off the specimen and put in a dissect-
ing pan for study. Severai specimens should be placed in a nitric
acid solution for a day or so (for directions for preparing, see
p. 12) to be used later for the stuay of the nervous system. Also
several specimens should be injected for the better study of the
circulatory system. With an injecting mass made as directed on
p. 451 wmtroduce through a small canula into the ventricle of the
heart. This will inject the arterial system, and with increased
pressure the injecting mass may be forced through the valves of the
heart, thus passing into the auricles and throughout the venous
system. After injecting use the specimen fresh or after it has been
preserved in 4% formalin.

External structure.— Note that the body of the toad
is divided into several principal regions or parts, as is the
human body, namely, a head, upper limbs, trunk, and
lower limbs. As you look at the toad note the similarity
of the parts on one side to those of the other, as right leg
corresponding to left leg, right eye to left eye, etc. This
arrangement of the body in similar halves among animals
is known as dzlateral symmetry. Asa rule animals which
show bilateral symmetry move in a definite direction.

The part that moves forward is the azterzor end, while
5

6 ELEMENTARY ZOOLOGY

the opposite extremity is the posterior end. In most
animals we note two other views or aspects; that which
is called the ‘‘back’’ and with most animals is, under
ordinary conditions, uppermost is the dorsum or dorsal
aspect, while that which lies below is the venter or ventral
aspect. When referring to a view from one side we speak
of it asa right or left /ateral aspect. These terms hold
good for most of the animals that we shall study.

Note at the anterior end of the toad a wide transverse
slit, the south. What other openings are on the anterior
end? Note the two large eyes, the organs of sight. Just
back of each eye note an elliptical, smooth membrane.
This is the tympanum of the outer cav, and through this
membrane the vibrations produced by sound-waves are
transferred to the inner ear, which receives sensations and
transmits them to the brain. Open the mouth by drawing
down the lower jaw. Note just within the angle of the
lower jaw the tongue. How is it attached to the wall of
the mouth? On the tongue are a great many fine papille
in which is located the sense of taste. It has now been
seen that most of the special senses of the toad have their
seat in the head. Pass a straw or bristle into one of the
nostrils. “Where does it come out?. hese mipemal
openings to the nose are the zazner nares. Note in the
roof of the mouth just posterior to each of the eyeballs an
opening. These are the internal openings to the wide
Eustachian tubes, which lead to the mouth from the
chamber of the ear behind the tympanum.

Note far back in the mouth an opening through which
food passes. This is the wsophagus or gullet. Note just
below this gullet an elevation in which is a perpendicular
slit, the @/ottzs. This is the upper end of the laryngo-
tracheal chamber, and the flaps within on either side of
the slit are the vocal cords. ;

Note at the posterior end of the body in the median

THE GARDEN TOAD 7

line an opening. This is the azal opening or anus. Note
the general make-up of the toad. How do its arms com-
pare with our own? How do its fore feet (hands) differ
from its hind feet? Note that the body is covered by a
tough enveloping membrane, the sézz. In the skin are
many glands which by their excretion keep it soft and
moist.

Internal structure.—TrcunicaL Nore.—With a fine pair of
scissors make a longitudinal median cut through the skin of the
venter from the anal opening to the angle of the lower jaw. Spread
the cut edges apart and pin back in the dissecting-pan.

Note the complex system of muscles which govern the
movements of the tongue. Observe a number of pairs of
muscles overlying the bones which support the arms.
These are attached to the pectoral or shoulder-girdle.
Mote, tie darce sheet of muscles covering the ventral
aspect of the toad. These are the abdominal muscles,
which consist of two sets, an outer and an inner layer.
Note that posteriorly the abdominal muscles are attached
to a bone. This is the pudzc bone of the pelvic girdle
which supports the hind legs.

TECHNICAL NOTE.—With the scissors cut through the muscles of
the body wall at the pubic bone and pass the points forward to the
shoulder-girdle. Separate the bones of the shoulder-girdle and pin

out the flaps of skin and muscle to right and left in the dissecting-
pan (see fig. 1). Cover the dissection with clear water or weak

alcohol.

Note two large conspicuous soft brown lobes of tissue.
These form the ver, an organ which produces a secretion
that assists in the process of digestion. Note just anterior
to the liver and extending between its two lobes a pear -
shaped organ, the “eart, which may yet be pulsating.
Are these pulsations regular? How many occur in a
minute? The lower end or apex of the heart, ventricle,
undergoes a contraction, forcing blood out into the d/00d-

8 ELEMENTARY ZOOLOGY

vessels. This is followed by a relaxation of the apex and
a contraction of the basal portion, the aurzcle. The heart
is surrounded by a delicate semi-transparent sac, the
pericardium. The pericardium is filled with a watery
fluid, dody-lymph, which bathes the heart. Note between
the lobes of the liver a small bladder-shaped transparent -
organ of a pinkish color. This is the gad/-cyst, or gall-
bladder, a reservoir for the dz/e, the secretion from the
liver. Separate the lobes of the liver and note, beneath,
the long convoluted tube which fills most of the body-
cavity. This is part of the almentary canal. 1s the
alimentary canal of uniform character ? The most anterior
portion of the canal, the gullet or wsophagus, leads to a
large U-shaped enlargement, the stomach. From the lower
end ef the stemach there extends a long; slender, very.
much convoluted tube, the small intestine, which is fol-
lowed by a much larger one, the /arge intestine. This large
intestine after one or two turns passes directly back into
the rectum, which opens at last to the exterior through the
anus. Note just ventral to the rectum a large thin-walled
membranous sac. This is the wrzzary bladder which acts
as a reservoir for the secretion from the Azduzeys. Notice
a many-branched yellow structure with a glistening
appearance, the fat-body (corpus adiposum). Now push
liver and intestine to one side and note the pinkish sac-like
bodies (perhaps filled with air), the 4wzgs. The lungs are
paired bodies which open into the laryngo-tracheal cham-
ber. The toad takes air into its mouth through its
nostrils, and then forces it, by a kind of swallowing action,
through the laryngo-tracheal chamber into the lungs.
Now lift the stomach and note in the loop between its
lower end and the small intestine a thin transparent tissue.
This is a part of the mesentery, which will be found to
suspend the whole alimentary canal and its attached
organs to the dorsal wall of the body. Note in the loop

THE GARDEN TOAD 9

of the stomach in the mesentery an irregular pinkish
glandular structure which leads by a small duct into the
intestine. This gland is the pancreas, and the duct is
the pancreatic duct. From it comes a secretion which
aids in the digestion of food. Near the upper end of the
pancreas note a round nodular structure, generally dark
red. This is the spleen, a ductless gland, the use of
which is not altogether known.

Make a drawing which will show as many of the organs
noted as possible. |

TECHNICAL NOTE.—Pass two pieces of thread under the rectum
near the pubic bone. Tie these threads tightly a short distance
apart and then cut the rectum in two between the threads. Now
carefully lift up the alimentary canal with attached organs (liver,
etc.), and cut it off near the region of the heart.

How is the heart situated with regard to the lungs?
The Zear¢ consists of a lower chamber with thick muscular
walls, the tip, called the ventrzcle, and two upper thin-
walled chambers, the rzgh¢t and left auricles. Can you
make out these three chambers? The purified blood from
the lungs flows into the left auricle, while the venous
blood from all over the body laden with its carbon dioxide
enters the right auricle. From these two chambers the
blood enters the ventricle. Here the pure and impure
blood are mixed. From the ventricle the blood enters a
large muscular tube on the ventral side of the heart. This
is the conus arteriosus, which gives off three branches on
each side; the anterior ones, the carotid arteries, supply
the head, the next ones, the systemic artertes, or aorte,
carry blood to the rest of the body, while the posterior
vessels, the pulmonary arteries, go directly to the lungs
and there break up into fine vessels (cafz/larzes) where
the carbon dioxide is given off and oxygen is taken from
the air. From the lungs the blood returns through the
pulmonary vein to the left auricle. Meanwhile the blood

1 Ke) ELEMENTARY ZOOLOGY

which has passed through the systemic arteries and body
capillaries is collected again into other vessels going back
to the heart; these are the vezws, which empty into a large
thin-walled reservoir, the szzuws venosus, which in turn
connects with the right auricle of the heart. Three large
veins enter the sinus venosus, namely, two pre-caval veins
at the anterior end, and a single post-caval vein at the
posterior end. ‘Trace out the larger arteries and veins
from the heart to their division into or origin from the
smaller vessels.

TECHNICAL NOTE,—Carefully remove the heart together with
thelungs. The lungs may be inflated by blowing into them through
the laryngo-tracheal chamber with a quill and tying them tightly,
after which they should be left for several days to dry. When
perfectly dry, sections may be cut through them in various places
with a sharp knife, and by this means a very good idea of the
simple lung structure of the lower backboned animals can be ob-
tained. With a sharp knife cut the heart open, beginning at the
tip (ventricle) and cutting up through the conus arteriosus and

the two auricles. Note the valves in the heart which separate
the different compartments.

Note on either side of the median line in the dorsal
region a pair of reddish glandular bodies (the kidneys).
From each kidney trace a tube (ureter) posteriorly toward
the region of the anus. The kidneys are the principal
excretory organs of the body. The blood which flows
through the delicate blood-vessels in the kidney gives up
there much of its waste products. These pass out through
small tubules of the kidneys into the ureters, which carry
the wastes toward the anus. Along one side of each
kidney may be seen a yellowish glistening mass, the
adrenal body.

In some of the specimens studied, the body cavity may
be filled with thousands of little black spherical bodies.
These are undeveloped eggs. They are deposited by the
mother toad in the water in long strings of transparent
jelly, which are usually wound around sticks or plant-

THE GARDEN TOAD II

stems at the bottom of the pond near the shure. From

these eggs the young toads hatch as tadpoles and in their
nasal

palatines, ee. spheno-ethmoid

x

_— maxillary m

Ox
ox; ~carpals
)

i radio-ulna

/
calcar yi

tibio-fAibula

astragalus
Fic, 2.—Skeleton of the garden toad.

life-history pass through an interesting metamorphosis.

p-ee Chapter X11.)

12 ELEMENTARY ZOOLOGY

TECHNICAL NOTE.—The teacher should be provided with several
well-cleaned skeletons of the toad in order that the bones may be
carefully studied. Boil in a soap solution a toad trom which most
of the muscles and skin have been removed (see p. 452). Leave in
this solution until the muscles are quite soft and then pick off all
bits of muscles and tissue trom the bones. If this is carefully done,
the ligaments which bind the bones will be left intact and the
skeleton will hold together. |

Note that the skeleton (fig. 2) consists of a head portion
which is composed of many bones joined together to form
a bony box, the skull; of a series of small segments, the
vertebre, forming the vertebral column, which with the
skull forms the axzal skeleton; and of the appendicular
skeleton, consisting of the bones of the fore and hind limbs.
Note that the skull is composed of many bones joined
together, some by satures, while others are fused.. Do
the. limbs attach direethy to the axial sleletem-. “ihe
anterior limbs (arms) articulate with the jpectoral or
shoulder-girdle. The arms will be seen to be made up
of a number of bofes placed end te ent More miar tue
uppermost, the umerus, 1s attached to the pectoral
girdle, while at its lower end it articulates with the
radio-ulna. At the lower end of the radio-ulna is a small
series of carpal bones which afford attachments for the
slender finger-bones, the phalanges or digital bones. The
bones of the leg are articulated with a closely fused set
of bones, the pelvic girdle. The leg-bones, proceeding
from the pelvic girdle, are named femur, t1b20-fibula,
tarsal bones, and phalanges or digits. “To what bones of
the arm do thésé é€orrespond? Detémnine tie other
principal bones of the skeleton by reference to figure 2.

TECHNICAL NOTE.—In a specimen which has been macerated
for sorne time in 20% nitric acid dissect out the nervous system.
Place the specimen in a pan ventral side uppermost and pin out.
Carefully pick away the vertebrae and the roof of the mouth-cavity,
thereby exposing the central nervous system, which will appear
light yellow,

THE GARDEN TOAD 13

Examine the évazz. In front of the true brain are the
olfactory lobes, the nervous centre for the sense of smell.
Wee otam itseli..is composed of several parts. The
anterior portion consists of two elongated parts, the
cerebral hemispheres; just back of these are the optic lobes
or midbraim, consisting of two short lobes, which are fol-
lowed by the small cerebeMum, which in turn is followed
by a long part, the medulla oblongata, which runs imper-
ceptibly into the long dorsal nerve, the spzzal cord. Note
the large optic nerves running out to each eye. How far
backward does the spinal cord extend? Note the many
pairs of nerves given off from the brain and spinal cord.
These nerves branch and subdivide until they end in very
fine fibres. Some end in the muscle-fibres, and through
them the central nervous system innervates the muscles.
These are motor endings. Still others pass to the surface
and receive impressions from the outside. These last are
sensory endings. Note that the spzval nerves arise from
the spinal cord by two roots, an anterior or ventral, and
a posterior or dorsal root. ‘Trace the principal spinal
nerves to the body-parts innervated by them. These
nerves are numbered as first, second, etc., according to
the number of the vertebre (counting from the head back-
ward) from behind which they arise.

CHAPTER =i

THE STRUCTURE AND ‘FUNCTIONS Glee
ANIMAL BODY

Organs and functions.—The body of the toad is com-
posed of various parts, such as the lungs, the heart, the
muscles, the eyes, the stomach, and others. The life of
the toad consists of the performance by it of various
processes, such as breathing, digesting food, circulating
blood, .moving,. seeing, and ‘others, These wanieus
processes are performed by the various parts of the body.
The parts of the body are called organs, and the processes
(or work) they perform are called their fuszctzons. The
lungs are the principal organs for the function of breath-
ing; the heart, arteries and veins are the organs which
have for their function the circulation of the blood; the
principal organ concerned in the digestion of food is the
alimentary canal, the function of seeing is performed by
the organs of sight, the eyes, and so one might continue
the catalogue of all the organs of the body and of all the
functions performed by the animal.

The animal body a machine.—The whole body of the
toad is a machine composed of various parts, each part
with its special work or business to do, but all depending
on cne another and all co-operating to accomplish the total
work of living. The locomotive engine is a machine
similarly composed of various parts, each part with its
special work or function, and all the parts depending on
one another and so working together as to perform satis-

14

STRUCTURE AND FUNCTIONS OF THE ANIMAL BODY 15

factorily the work for which the locomotive engine is
intended. An important difference between the locomo-
tive engine and the toad’s body is that one is a lifeless
machine and the other a living machine. But there is a
real similarity between the two in that both are composed
of special parts, each part performing a special kind of
work or function, and all the parts and functions so fitted
together as to form a complex machine which successfully
accomplishes the work for which it is intended. And this
similarity is one which should help make plain the funda-
mental fact of animal structure and physiology, namely,
the division of the body into numerous parts or organs,
and the division of the total work of living into various
processes which are the special work or functions of the
various organs.

The essential functions or life-processes.—The toad
has a great many different special parts in its body. Its
body is very complex. It performs a great many differ-
ent functions, that is, does a great many different things
in its living. And the structure and life of most of the
other animals with which we are familiar are similarly
complex: a fish, or a rabbit, or a bird has a body com-
posed of many different parts, and is capable of doing
many different things. Are all animals similarly complex
in structure, and capable of doing such a great variety of
things? We shall find that the answer to this question
is No. There are many animals in which the body is
composed of but a few parts, and whose life includes the
performance of fewer functions or processes than in the
case of the toad. There are many animals which have
no eyes nor ears nor other organs of special sense.
There are animals without legs or other special organs of
locomotion; some animals have no blood and hence no
heart nor arteries and veins. But in the life of every
animal there are certain processes which must be per-

16 ELEMENTARY ZOOLOGY

formed, and the body must be so arranged or composed
as to be capable of performing these necessary life-
processes. All animals take food, digest it, and assimi-
late it, that is, convert it into new body substance; all
animals take in oxygen and give off carbonic acid gas;
all animals have the power of movement or motion (not
necessarily locomotion); all animals have the power of
sensation, that is, can feel; all animals can reproduce
themselves, that is, produce young. These are the
necessary life-processes. It is evident that the toad could
still live if it had no eyes.” Séecine isnot ome ser the
necessary functions or processes of life. Nor is hearing,
nor is leaping, nor are many of the things which the toad
can do; and animals can exist, and do exist, without any
of those organs which enable the toad to see and hear and
leap. But the body of any animal must be capable of
performing the few essential processes which are necessary
to animal life. How surprisingly simple such a body can
be will be later discovered. But in most animals the
body is a complicated object, and is able to do many
things which are accessory to the really essential life-
processes, and which make its life complex and elaborate.

CHARTER, IV
THE CRAYFISH (Caméarus sp.)

LABORATORY EXERCISE

TECHNICAL NOTE.—The crayfish, or crawfish, is found in most of
the fresh-water ponds and streams of the United States. (It is not
found east of the Hoosatonic River, Mass. In this region the lob-
ster may be used. On the Pacific coast the crayfishes belong to the
genus Asfacus.) Crayfishes may be taken by a net baited with dead
fish, or they may be caught in a trap made from a box with ends
which open in, and baited with dead fish or animal refuse of any
sort. This box should be placed in a pond or stream frequented
by crayfish. If possible the student should study the living animal
and observe its habits. Crayfish which are to be kept alive should be
placed in a moist chamber in a cool place. They will keep for a
longer time in a moist chamber than in water. Some fresh specimens
should be injected by the teacher for the study of the circulatory
system. A watery solution of coloring matter or, better, of an in-
jlecting mass of gelatine (See p. 451) is injected into the heart
through the needle of a hypodermic syringe. For the purpose of
injecting, a small bit of the shell may be removed from the cephalo-
thorax above the heart. Specimens which are to be kept for some
time should be placed in alcohol or 4% formalin.

External structure (fig. 3).—Place a specimen in a
pan for study. Note that the body, which of course differs
much in shape from that of the toad, is also unlike that of
the toad in being covered by a hard calcareous exoskeleton,
which acts as a covering for the soft parts and also asa
place of attachment for the muscles, just as the internal
skeleton does in the case of the toad. he body is com-
posed of an anterior part, the cephalothoraxr, and a
posterior part, the abdomen. The cephalothorax is covered
above and on the sides by the carapace, which is divided
into parts corresponding to the head and thorax of the

t7

18 ELEMENTARY ZOOLOG

antennule

antenna

----chela

4
thorax,

\
\

genital aperture

x
x
-
“es

"TE pleopods

¢
we ¢

a 19155) a rene SSeS

Fic. 3.—Ventral aspect of crayfish (Cambarus sp.), with the appendages of
one side disarticulated.

THE GRAYHSH 1g

toad by the transverse cervical suture. The abdomen
is composed of segments. How many? The flattened
terminal segment is called the ¢e/sox. Is the cephalo-
thorax composed of segments? Where is the mouth of
the crayfish? Where is the anal opening ?

At the anterior end of the cephalothorax note a sharp
projection, the rostrum. Where are the eyes? Remove
one of them and examine its outer surface with a micro-
scope. A bit of the outer wall should be torn off and
mounted on a glass slide. Note that it is made up ofa
great many little facets placed side by side. Each of
these facets is the external window of an eye element or
ommatidium. An eye composed in this way is called a
compound eye. In front of the eyes note two pairs of
slender many-segmented appendages. The shorter pair,
the aztennules, are two-branched. Remove one of them
and note at its base a small slit along the upper surface.
This slit opens into a small bag-like structure which con-
tains fine sand-grains. The bag is protected by a series
of fine bristles along the edge of the slit. This bag-like
structure is believed to be an auditory organ. The longer
pair of appendages are the aztenn@, and in the fine hair-
like projections upon the joints is believed to be located
the sense of smell. Thus it will be seen that the sense-
organs of the crayfish, like those of the toad, are located
on the head. Beneath the basal portion of each antenna
there is a flat plate-like projection, at the base of which
on the upper edge will be noted a small opening, the
exit of the kidney, or green gland.

Make a drawing of the surface of part of an eye; also
of an antennule; and of an antenna.

TECHNICAL NOTE.—Stick one point of the scissors under the
posterior end of the carapace on the right side, and cut forward,
thus exposing a large cavity, the gill-chamber. Remove all of the
mouth-parts, legs and abdominal appendages from the right side,
being careful to leave the fringe-like parts, the gills, attached to

20 ELEMENTARY ZOOLOGY

their respective legs. Place all of the appendages in order on a
piece of cardboard.

Examine the abdominal appendages, called pleopods,
or swimming feet. How many pairs are there? Each
is composed of a basal part, the profopodite, and two
terminal segments, an inner one, the exdopodite, and an
outer, the eropodite. In the males the first and second
pleopods of the abdomen are larger and less flexible than
the others... In the female the pleopods servesto carry
the eggs and the first two pairs are very small or absent.
Note the last set of abdominal appendages. These are
the wvopods, which together with the telson form the tail.

Make a drawing of the pleopods of one side.

Examine the appendages of the cephalothorax. Like
the appendages of the abdomen the typical composition
of each -includes a protopodite, an-exopedite=and an
endopodite, but some of these appendages are much
modified, and show a loss of one of these parts, or the
addition of an extra part. The cephalothoracic appen-
dages may be divided into three groups, an anterior group
of three pairs of mouth-parts (belonging to the head) of
which the first pair is the szandzbles and the others are the
maxille; asecond group of three pairs of foot-jaws or
maxillipeds, belonging to the thorax, and a third group of
five pairs of walking-legs. The mandibles, lying next to
the mouth-opening, are hard and Jaw-like and lack the
exopodite; the first maxilla are small and also lack the
exopodite; the second maxilla have a large paddle-like
structure which extends back over the gills on each side
within the space, the branchial chamber, above the gills.
It is by means of this paddle-like structure (the scaphog-
nathite) that currents of water are kept up through the
gill-chambers. The maxillipeds increase in size from
first to third pair. Each pair of walking-legs except the
last bears gz//s. These gills are the organs by which

THE CRAYFISE 21

the blood is purified. The blood of the crayfish flows into
the large vessels on the outer sides of the gill and thence
into the fine vessels in the little leaf-like lamella. At the
same time the air which is mixed with the water bathing
the gills passes freely through the thin membranous walls
of these lamellz and blood-vessels, and the blood gives
off its carbonic acid gas to the water and takes up oxygen
from the air in the water. Thus it will be seen that the
Gnaee por-aae oill is like that of the lung in: the . toad,
namely, to act as an organ for the elimination of carbonic
acid gas and the taking up of oxygen.

Note the pincer-like appendages of the first pair of legs.
These pincers are the che/@, with which food is torn into
bits and placed in the mouth. In the basal segment of
each of the last pair of legs of the male note the genztal
pore. In the female the gemztal pores are in the basal
segments of the next to last pair of legs. Is the crayfish
bilaterally symmetrical ? Note the repetition of parts in
the crayfish, that is, the recurrence of similar-parts in
successive segments. This serial repetition of parts among
animals is called metemerism.

Internal structure (fig. 4) TECHNICAL NOTE.—-With a pair
of scissors cut through the dorsal wall of the cephalothorax into the

body-cavity. Cut the body-wall away from both sides and remove
the middle portion.

At the anterior end of the cephalothorax note the large
membranous sac, the stomach. Attached to each end of
this are sets of muscles which control its movements.
To the right and left of the stomach notice attached to
the shell large muscles which connect by stout ligaments
at their lower ends with the mandibles. Note a yellow
fringe-like structure, the digestive gland, which fills most
of the region about the stomach. It connects by a pair
of small tubes, the 6z/e-ducts, with the alimentary canal.
Within the posterior portion of the cephalothorax note a

RY ZOOLOGY

ENTA

ELEM

22

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9unjadD porwab
2 fiwajan jpULajs
7

yinou

_.---- Snbnydosa0

—

Cee

SajISNM JDULIWOPAD

4 4s ¢ ' (ey AN ; \ .
fuano youmopgn yosuop ff BUBB FT A ‘ :
5 one ra w ot . / | \ ‘ YIDULODS ‘.
wnepspouad / 2409Y SUIS} SN \ ‘
ges f 1 \-yqaaj-yoomoys \
suasafap soa yoouojs oisojid \
: \ puvn)b waasb

haajan ovmpoyrydo

THE CRAYFISH 23

pentagonal sac, the ear¢t, contained within a delicate
membrane, the fericardium. Remove the pericardium
and note a pair of dorsal openings into the heart, called
ostta. (There are also two lateral pairs and a ventral
pair of ostia.) Note passing anteriorly from the heart
along the median line to the eyes a blood-vessel, the
ophthalmic artery. Arising from the anterior portion of
the heart are the anfennary arteries, running to the
antenne. Yet another pair running anteriorly from the
heart to the stomach and digestive glands are called the
hepatic arteries. From the posterior end of the heart
arises the dorsal abdominal artery, running back to -the
telson. Below this arises the sterva/ artery, which will
be seen later.

In the region below the heart are located the reproduc-
tive organs. They are whitish glandular masses from
each of which runs a tube which opens at the base of the
last pair of walking-legs in the male, and at the base of
the third pair of walking-legs in the female.

TECHNICAL NOTE.—Cut longitudinally through the dorsal wall
of the abdomen on either side of the median line and remove the
piece of shell.

Note the powerful szwsc/es within which flex and extend
the abdomen. By a rapid contraction of these muscles
the tail is brought beneath the body, propelling the animal
strongly backwards. When the crayfish crawls it gen-
erally goes forward, but in swimming it reverses this
direction.

Make a drawing showing, in their natural position, the
internal organs which have been studied.

Examine the alimentary canal for its whole length.
Note that the large bladder-shaped stomach is attached
to the mouth-opening by a short tube. What part of the
canal is this? From the posterior end of the stomach is
a short thick-walled part, the swa// intestine, followed by

24 ELEMENTARY ZOOLOGY

a long straight tube, the /arge intestine, which opens to
the exterior through the anus.

TECHNICAL NOTE.—Remove the alimentary canal, detaching it
from the anal end first, and working forward.

Cut the stomach open. Note an anterior portion, the
cardiac chamber, and a smaller posterior portion, the
pyloric chamber. ‘examine its inner surface. What do
you find here? This structure is called the gastrzc mill.
Food, which for the most part consists of any dead
organic matter, is chewed by the ‘‘stomach-teeth ’’ into
fine bits, and is then passed into the pyloric chamber. It
is here that the digestive glands empty their secretion into
the food. These glands have the same office as have the
liver and pancreas combined in the toad, and so they are
often called the “epato-pancreas. When the stomach has
been removed there will be noted in the anterior portion
of the body paired, flattened bodies, already mentioned,
which connect with openings at the base of each of the
antenne by means of wide thin-walled sacs, the ureters.
These organs are the Azdueys, or green glands. ‘Their
office is similar to that of the kidneys in the toad, namely,
the elimination of waste from the body.

TECHNICAL NOTE.—Carefully remove all of the alimentary canal,
digestive glands, and reproductive organs. This process will expose
the floor of the cephalothorax. Now cut away from either side the
horny floor or bridge at the bottom of the cephalothorax. If the
specimen has not already been immersed, place it in clear water for
further dissection.

The foregoing dissection will expose the central nervous
system. It extends as a series of paired gangha con-
nected by a double nerve-cord along the ventral median
line from the cesophagus to the last segment of the
abdomen. From what points do the lateral nerves arise ?
Anteriorly the double nerve-cord divides, the two parts

VAE CRAYFISH 25

passing upward on each side of the cesophagus, where they
again meet to form the supra-ewsophageal ganglion or
braim. “Where do the nerves run which rise from the
brain? What is the difference between the position of
the central nervous system in the crayfish and in the toad ?

Make a drawing of the nervous system.

Just beneath the nerve-cord note a blood-vessel ex-
tending the length of the body. This is the sternal
artery, which arises from the posterior end of the heart
and passes ventrally at one side of the alimentary canal
and between the nerve-cords. Here the sternal artery
divides into an anterior and a posterior branch, from
which lesser branches are given off to each one of the
appendages. The various arteries running to all parts of
the body finally pour out the blood into the body-cavity,
where it flows freely in the spaces among the various tissues
and organs. After the blood has bathed the body tissues
it flows to the gills on either side, passing up the outer
side of the gill through delicate thin-walled vessels, where
it is oxygenated as has already been described. From
the gills the purified blood flows back on the inner side
through a large chamber, szzws, into the pericardium,
through the ostia of the heart, whence it is driven into the
arteries once more. This sort of a circulatory system in
which the blood in places is not enclosed in a definite
vessel is known as an ofen system. In the toad we find
tee ploed-in a clos¢d sysiem, i.e., arteries leading into
capillaries which in turn lead into veins, in no case allow-
ing the blood to pass freely through the spaces of the
body.

CHAPTER V.

THE MODIFICATION OF ORGANS AND FUNC-
TIONS

Differences between crayfish and toad.—In the dis-
section of the crayfish one of the most important things in
the study of zoology has been learned. It is plain that
the crayfish has a body composed, like the toad’s, of
parts or organs, and that most of these organs, although
differing much in appearance and actual structure from
those of the toad, correspond to similarly named organs
of the toad, and perform the same functions or processes,
although with many striking differences, essentially in the
same way as in the toad. But the structure of the body
is very different in the two animals. The toad has an
internal body skeleton to which the muscles are attached,
and a soft, yielding, outer body-covering or skin; the
crayfish has no internal skeleton, but has its body covered
by a horny, firm body-wall to which the muscles are
attached. The toad has its main nervous chain lying just
beneath the dorsal wall of the body; the crayfish has its
main nervous chain lying just above the ventral wall of
the body. The toad has lungs and takes up oxygen from
the air of the atmosphere; the crayfish has gills and takes
up oxygen from the air which is mixed with the water.
The toad has a single pair of jaws; the crayfish has
several pairs of mouth-parts. The toad has four legs
fitted for leaping; the crayfish has numerous legs fitted

for crawling or swimming. The crayfish’s body is com-
26

THE MODIFICATION OF ORGANS AND FUNCTIONS — 27

posed of a series of body-rings or segments; the toad’s
body is a compact apparently unsegmented mass. The
toad has eyes each with a single large lens and capable
of moving in the head and of changing their shape and
hence their focus; the crayfish’s eyes are immovable and
have a fixed focus, and are composed of hundreds of tiny
eyes each with lens and special retina of its own. And
so a long list of differences might be gone through with.

Resemblances between toad and crayfish.—But on the
other hand there are many resemblances—resemblances
both in structure and life-processes or physiology. Both
toad and crayfish have organs for the prehension of food,
its digestion and its assimilation. And these organs, the
organs of the digestive system, while differing in details
are alike in being composed principally of a long tube,
the alimentary canal, running through the body, open
anteriorly for the taking in of food, and open posteriorly
for the discharge of indigestible useless matter. Both
alimentary canals are divided into various special regions
for the performance of the various special processes con-
nected with the digestion and assimilation of food. Each
is adapted for the special kind of food which it is the habit
of the particular animal to take. The two sets of organs
are essentially alike and have the same essential function
or life-process to perform. But this process differs in the
details of its performance, and the organs which perform
this function and which constitute the digestive system of
each are modified to suit the special habits or kind of life
of the animal.

Both toad and crayfish have a heart with blood-vessels
leading from it. In the case of the toad the heart is more
complex than in the crayfish, and the system of blood-
vessels is far more extensive and elaborate. But the heart
and blood-vessels in both animals subserve the same pur-
pose; their function is the circulation of the blood, this

28 ELEMENTARY ZOOLOG ©

being the means by which oxygen and food are carried
to all growing or working parts of the body, and by
which carbonic acid gas and other poisonous waste
products are brought away from these parts. But this
function differs somewhat in its performance in the two
animals, and the organs which perform the function are
correspondingly modified in structural condition.

Both toad and crayfish have organs for respiration, that
is, for breathing in oxygen and breathing out carbonic
acid, gas. . But the .toad takes its oxygen? ixem-the
atmosphere about it; its respiratory organs are the
lungs, the sac-like tube leading to the mouth, and
the external openings for the ingress and exit of the
gases. The crayfish, living mostly in the water, takes
its oxygen from the air which ts mechanically mixed
with, the water. Its. respiratory ofgams ape ie ills:
There is a great difference, apparently, im the stauretural
conditions of the organs of respiration in the two animals.
As a:matter of fact.the difference iS dessj@reauseeame at
first sight, appears to be the case. The lungs of the toad
are composed primarily of a thin membrane, in the form
of a sac, richly supplied with blood-vessels. Air is
brought to this thin respiratory membrane and by osmosis
the oxygen passes through the membrane and through
the thin walls of the fine blood-vessels, and is taken up
by the blood. At the same time the carbonic acid gas —
brought by the blood to the lungs from all parts of the
body is given up by it and passes through the membranes
in order to leave the body. Ihe air comes Gayeontact
with the respiratory membrane (which is situated inside
the body) by means of a system of external openings and
a conducting chamber, and by these same openings and
chamber the carbonic acid gas leaves the body. In the
crayfish the gills are nothing else than a large number of
small flattened sacs each composed of a thin membrane

Pete ODIFIGATION: OF, ORGANS AND FUNCTIONS. © 29

richly supplied with blood-vessels. This respiratory mem-
brane is not, in the crayfish, situated inside the body, but
on the outer surface, although protected by being in a sort
of pocket with a covering flap, and it comes into immediate
contact with the air held inthe water which freely bathes
the gills. By osmosis the oxygen of this air passes in
through the gill-membranes, while the carbonic acid gas
brought by the blood passes out through them. Exactly
the same exchange of gases is accomplished as in the
toad. But because of the great difference in the conditions
of life of the toad and crayfish, one living in water, the
other living out of water, the character of the performance
of the function of respiration, and correspondingly the
structural condition of the organs performing this function,
are strikingly different.

Modification of functions and structure to fit the
animal to special conditions of its life.—As has been
done with the organs of digestion, circulation, and
respiration, so we might compare the other organs of the
crayfish and the toad. There would be found not only
many very marked differences between organs which have
the same general function in the two animals, but we
should find also numerous organs in the toad which are
not present at all in the crayfish, and conversely; and this
means, of course, that the toad can do numerous things,
perform numerous functions, which the crayfish cannot,
and, conversely, that the crayfish does some things which
the toad cannot. But both of these animals agree in
possessing in common the capability of performing those
processes such as taking food, breathing, reproducing,
etc., to which attention has been called as being indis-
pensable to all animal life. These processes, however,
are performed by the two animals in different ways and
_ the organs for the performance of these processes, although
at very bottom essentially alike, are in outer and super-

39 ELEMENTARY ZOOLOGY

ficial details of position, appearance and general structure
markedly different. Animals are fitted to live in different
places amid different surroundings by having their bodies
modified and the performance of their life-processes modi-
fied to suit the special conditions of their life.

Vertebrate and invertebrate.—In selecting the toad
and the crayfish as the first animals to study and to com-
pare with each other, we have chosen representatives of
the two great groups into which the complexly organized
animals are divided, viz., the group of backboned or
vertebrate animals, and the group of backboneless or
invertebrate animals. To the vertebrates belong all those
which have an internal bony skeleton (and a few without
such a skeleton) and which have also an arrangement of
body-organs on the general plan of the toad’s body. A
conspicuous feature of this arrangement is the situation of
the spinal cord or main great nerve-trunk along the back
or dorsal wall of the animal, and inside of a backbone.
All the fishes, batrachians (frogs, toads, salamanders,
etc.), reptiles (snakes, lizards, alligators, etc.), birds, and
mammals (quadrupeds, whales, seals, etc.) belong to the
vertebrates. The backboneless or invertebrate animals
have no internal bony skeleton and have their main nerve-
trunk usually along the ventral wall of the body, some-
times in a circle around the mouth, but never in a back-
bone. To the invertebrates belong all insects, lobsters,
crabs, clams, squids, snails, worms, starfishes and sea-
urchins, corals and sponges, altogether a great host of
animals, mostly small.

CHAPTER V1

AMCEBA AND PARAMG@CIUM

LABORATORY EXERCISE

Amoeba.—TecunicaL NoTe.—Amebe are found in stagnant
pools of water on the dead leaves, sticks and slime at the bottom.
To obtain them, collect slime and water from various puddles in sepa-
rate bottles and take them to the laboratory. Place a small drop of
slime on a slide under a cover-glass. Examine under the low power
first and note any small transparent or opalescent objects in the
field. Examine these objects with the higher power and note that
some are mere granular jelly-like specks, which slowly (but con-
stantly) change their form. These are Amevdbe.

A teacher of zoclogy recommends the following method of obtain-
ing a large supply of dmwd@- ‘For rearing Am@dbe place two or
three inches of sand in a common tub, which is then filled with
water and placed some feet from a north window; three or four
opened mussels, with merest trace of the mud from the stream in
which they are taken, are partially buried in the sand and a hand-
ful of Wztella and a couple of crayfish cut in two are added; as
decomposition goes on a very gentle stream is allowed to flow into
the tub, and after from two to four weeks abundant Am@ebe are to
be found on the surface of the sand and in the scum on the sides of
the tub; small Ame@ebe appear at first, and later the large ones.”

Having found an Ame@bva (fig. 5) note its irregular
shape, and if it moves actively observe its method of mov-
ing. How is this accomplished? The viscous, jelly-like
substance which composes the whole body of an Amoeba
is called protoplasm. The little processes which stick
out in various directions are the ‘‘false feet ’’ (pseudo-
podia). Note that the outer portion, the ectosarc, of the
protoplasmic body is clear, while the inner, the ezdosarc,
is more or less granular in structure. Has Am@ba a
definite body-wall? Do the pseudopodia protrude only

31

32 FLEMENTARY ZOOLOGY

from certain parts of the body? Within the endosarc
note a ciear globular spot which contracts and expands,
or pulsates, more or less regularly. This is the contrac-
tile vacuole. Note the small granules which move about
within the endosarc. These are food-particles which

Fic. 5.—Ameba sp.; showing the forms assumed by a single individual in
four successive changes. (From life.)

have been taken in through the body-wall. Note how
pseudopodia flow about food-particles in the water and
how these are digested by the protoplasm. If an Amwba
comes into contact with a particle of sand, note how it at
once retreats. Note within the endosarc an oval trans-
parent body which shows no pulsations. This is the

AMCEBA AND PARAMCECIUM 33

nucleus, a very complex little structure of great impor-
tance in the make-up of Ameda.

Note that dmeba has no mouth or alimentary canal;
no nostrils or lungs, no heart or blood-vessels, no mus-
cles, no glands. It is an animal body not made up of
distinct organs and diverse tissues. Its whole body is a
simple minute speck of protoplasm, a single animal cell.
But it takes in food, it moves, it excretes waste matter
from the body, is sensitive to the touch of surrounding
objects, and, as we may be able to see, it can reproduce
itself, i.e., produce new Am@ebe. Ameba is the simplest
living animal.

It is only rarely that we can find an Amba actually
reproducing. The process, in its gross features, is very
simple. First the Amqedéa draws in all of its pseudopodia
and remains dormant for atime. Next, certain changes
take place in the nucleus, which divides into equal por-
tions, one part withdrawing to one end of the protoplasmic
body, the other to the opposite end. Soon the body pro-
toplasm itself begins to divide into two parts, each part
collecting about its own half of the nucleus. Finally the
two halves pull entirely away from each other and form
two new Amebe, each like the original, but only half as
large. This is the simplest kind of reproduction found
among animals.

Amebe continue to live and multiply as long as the
conditions surrounding them are favorable. But when
the pond dries up the Amwde@ in it would be exterminated
were it not for a careful provision of nature. When the
pond begins to dry up each Amwbda contracts its pseudo-
podia and the protoplasm secretes a horny capsule about
itself. It is now protected from dry weather and can be
blown by the winds from place to place until the rains
begin, when it expands, throws off the capsule and com-
mences active life again in some new pond,

34 ELEMENTARY ZOOLOGY

The Slipper Animalcule (Paramecium sp. )— TECHNICAL
NOTE.—/fParamecia can be secured in most pond water where
leaves or other vegetation are decaying. However, if specimens
are not readily secured place some hay or finely cut dry clover in a
glass dish, cover with water and leave in the sun for several days.
In this mixture specimens will develop by thousands. Place a drop
of water containing Paramecta on a slide with cover-glass over it.
Using a low power, note the many small animals darting hither and
thither in the field. Run a thin mixture of cherry gum in water
under the cover-glass. In this mixture they can be kept more quiet
and be better studied.

How does Paramecium (fig. 6) differ from Amada in
form and movement? MHas the body an anterior and a
posterior end? The delicate, short, thread-like processes,
on the surface of the body, which beat about very rapidly
in the water are called cz/za, and they are simply fine
prolongations of the body protoplasm. What is their
function? Note a fine cuticle covering the body. Note
also many minute oval sacs lying side by side in the
ectosarc. These are called ¢rzchocysts and from each a
fine thread can be thrust out.

Note on one side, beginning at the anterior end, the
buccal groove \eading into the interior through the gw//et.
Observe also that by the action of the cilia in the buccal
groove food-particles are swept into the gullet. Rejected
or waste particles are ejected from the body occasionally.
Where? Note about midway of the Paramecium an
ovoid body with a smaller oval one attached to its side,
the former being the macronucleus, the latter the szcro-
nucleus. Note that there are two contractile vacuoles in
the Paramecium; also that the food-vacuoles have a
definite course in their movement inside the endosarc.

Make a drawing of a Paramecium.

In comparing Paramecium with Ameéba it is apparent
that the body of the first is less simple than that of the
second. The definite opening for the ingress of food, the
two nuclei, the fixed cilia, and the definite cell-wall giving

AMCEBA AND PARAMCECIUM 35

a fixed shape to the body, are all specializations which
make Paramecium more complex than dmeba. But the
whole body is still composed of a single cell, and there
is, as in Ameda, no differentiation of the body-substance
into different tissues, and no arrangement of body-parts
as systems of organs.

Paramecium may occasionally be found reproducing.
This process takes place very
much asin Ameba. The animal
remains dormant for a while, the
micronucleus then divides, the
macronucleus elongates and
finally divides in two, the proto-
plasm of the body becomes con-
stricted into two parts, each part
massing itself about the withdrawn
halves of the macro- and micro-
nuclei, and lastly the whole breaks
into two smaller organisms which
exow «oO be like the original.
After multiplication or reproduc-
tion has gone on in this way for
numerous generations (about one
hundred), a fusion of two Para-
mecia seems necessary before
further divisions take place. This
process of fusion, called conjuga-
tion, may be noted at some sea-

: ., Fic. 6. — Paramecium sp. ;
sons. lwo Paramecza unite with puccal groove at right. (From
their buccal grooves together, — life-)
part of the macronucleus and micronucleus of each passes
over to the other, and the mixed elements fuse together
to form a new macro- and micronucleus in each half.
The conjugating Paramecia now separate, and each
divides to form two new individuals.

CHAPTER >-Val

THE SINGLE-CELLED ANIMAL BODY.—PRO-
POPLASM AND Tif sere

The single-celled body.—The study of Amada and
Paramecium has made us acquainted with an animal body
very different from that of the toad or the crayfish. These
extraordinarily minute animals have a body so simple in
its composition, compared with the toad’s, that if the
toad’s body be taken for the type of the animal body,
Ameba might readily be thought not to be an animal at
all. The body of Aseéa is not composed of organs, each
with a particular function or work to perform. Whatever
an Ameoa does is done, we may say, with its whole body.
But as we learn the things that this formless viscid speck
of matter does, we see that it is truly an animal; that it
really does those things which we have learned are the
necessary life-processes of an animal. Amada takes up
and digests food composed of organic particles; it has the
power of motion; it knows when its body comes in con-
tact with some external object, that is, it can feel or has
the power. of sensation. Amada takes in oxygen and
gives out carbonic acid gas, and it can produce new in-
dividuals like itself, that is, it has the power of reproduc-
tion. But for the performance of these various life-pro-
cesses or functions it has no special parts or organs, no
mouth or alimentary canal, no lungs or gills, no legs, no
special reproductive organs. We have here to do with one

of the ‘‘simplest animals.’’ With a minute, organless,
36

THE SINGLE-CELLED ANIMAL BODY 37

soft speck of viscous matter called protoplasm for a body,
the simplest structural condition to be found among living
beings, Amba nevertheless is capable of performing, in
the simplest way in which they may be performed, those
processes which are essential to animal life.

Paramecium has a body a little less simple than
Ameba. The food-particles are taken into the body
always at a certain spot; this might be spoken of as a
mouth. And the body has some special locomotory
organs, if they may be so called, in the presence of the
emia ine body, too, has a definite shape or form.
But, as in Ameéa, there is no alimentary canal, - nor
nervous system, nor respiratory system, nor reproductive
system. The whole body feels and breathes and takes
part in reproduction.

A long jump has been made from the toad and crayfish
to Ameba and Paramecium; from the complex to the
simplest animals. But, as will later be seen, the great
difference between the bodies of these simplest animals
and those of the highly complex ones is only a difference
of degree; there are animals of all grades and stages of
structural condition connecting the simplest with the most
complex. When animals are studied systematically, as
it is called, we begin with the simplest and proceed from
them to the slightly complex, from these to the more
gcomipiesx, and finally to the most complex. There are
hundreds of thousands of different kinds of animals, and
they represent all the degrees of complexity which lie
between the extremes we have so far studied.

The cell.— The characteristic thing about the body of
Ameba and Paramecium and the other ‘‘ simplest
animals '’—for there are many members of the group of
‘‘simplest animals,’’ or Protozoa—is that it is com-
posed, for the animal’s whole lifetime, of a single cell.
A cell is the structural unit of the animal body. As

38 ELEMENTARY ZOOLOGY

will be learned in the next exercise, the bodies of all
other animals except the Protozoa, the simplest animals,
are composed of many cells. These cells are of many
kinds, but the simplest kind of animal cell is that shown
by the body of an Ameéa, a tiny speck of viscous, nearly
colorless protoplasm without fixed form. The protoplasm
composing the cell is diferentiated to form two parts or
regions of the cell, an. inner denser: part, ealleas the
nucleus, and an outer clearer part, called the cytoplasm.
Sometimes, as in the Paramacium, the cell is enclosed by
a cell-wall which may be simply a denser outer layer of
the cytoplasm, or may be a thin membrane secreted by
the protoplasm. Thus the cell is not what its name
might lead us to expect, typically cellular in character;
that is, it is not (or only rarely is) a tiny sac or box of
symmetrical shape. While the cell is composed essen-
tially of protoplasm, yet it may contain certain so-called
cell-products, small quantities of various substances pro-
duced by the life-processes of the protoplasm. These
cell-products are held in the protoplasmic body-mass of
the cell, and may consist of droplets of water or oil or resin,
of tiny’ particles of starch or “pigment, ete: Wie cell
cannot be said to be composed of organs, because the
word organ, as it is commonly used in the study of an
animal, is understood to mean a part of the animal body —
which is composed of many cells. But the single cell.
can be somewhat differentiated into parts or special
regions, each part or special region being especially
associated with some one of the life-processes. In
Paramecium, for example, the food is always taken in
through the so-called mouth-opening; the fine proto-
plasmic cilia enable the cell to swim freely in the water,
the waste products of the body are always cast out through
a certain part, and so on. But this is a very simple sort
of differentiation, and the whole body is only one of those

THE SINGLE-CELLED ANIMAL BODY 39

structural units, the cells, of which so many are included
in the body of any one of the complex animals.

Protoplasm.—The protoplasm, which is the essential
substance of the typical animal cell and hence of the
whole animal body, is a substance of very complex
chemical and physical make-up. No chemist has yet
been able to determine its exact chemical constitution,
and the microscope has so far been unable to reveal
certainly its physical characters. The most important
thing known about the chemical constitution of proto-
plasm is that there are always present in it certain com-
plex albuminous substances which are never found in
inorganic bodies. And it is certain that it is on the
presence of these substances that the power possessed
by protoplasm of performing the fundamental life-pro-
cesses depends. Protoplasm is the primitive physical
basis of life, but it is the presence of the complex albu-
minous substances in it that makes it so.

The physical constitution of protoplasm seems to be
that of a viscous liquid containing many fine globules of a
liquid of different density and numerous larger globules
of a liquid of still other density. Some naturalists believe
the fine globules to be solid grains, while still others
believe that numerous fine threads of dense protoplasm
lie coiled and tangled in the clearer, viscous protoplasm.
But the little we know of the physical structure of proto-
plasm throws almost no light on the remarkable properties
of this fundamental life-substance.

CHAPTER. Vili

CELLULAR STRUCTURE OF THE TOAD (OR
FROG)

LABORATORY EXERCISE

The blood.—TecunicaL Nore.—The blood of a frog can be
studied as it flows through the small vessels in the membranes
between the toes while the animal is alive. Place a frog on a small
flat board which has’ had a hole cut near one jend™ sand) site a
piece of cloth bind it to the board. Spread the web between two
toes over the hole in the board and keep it in place with pins.
This done, examine the distended web under the compound micro-
scope first with low then with higher power, and observe the blood-
vessels and the blood circulating in them. For a further study of
the blood kill a toad or frog and place a drop of the blood on a
slide with a cover-glass over it.

Put the prepared slide under the microscope and note
that the blood, which as seen with the umaided seve
appears to be a red fluid, is made up of a great many
yellowish elliptical disks or cells, the dlood-corpuscles,
floating in a liquid, the dlood-plasma. Here and there
you may notice am@eboid blood-corpuscles. These are
irregular-shaped cells which move about by thrusting out
pseudopodia. They look like some of the unicellular
animals, as the Amwéa. Can you distinguish a nucleus
and cell-wall in the blood-cells ?

Make drawings of these blood-cells.

The skin.—Tecunicat Note.—Keep a live toad or frog in
water for some time and note if its skin becomes loose or begins to
slip away. If the outer skin, epidermis, comes off, take some of the
shed skin and wash it in water, then stain for three or four minutes
in a solution of methyl-green and acetic acid (see p. 451). Cut

40

GEELULAR STRUCTURE OF THE TOAD (OR FROG) 4!

the pieces of stained skin into small bits and examine one of these
under the microscope.

With the low power of the microscope you will note
that the skin is made up of a great many flat ce//s placed
edge to edge. Each one has its cell-wall and a central
darkly stained nucleus.

Make a drawing of a portion of the toad’s skin.

The liver.—TecunicaL Notr.—Cut through the fresh liver
of a toad, and with a knife-blade scrape from the cut surface some
of the liver-cells and place them on a slide with cover-glass.

Examine under the microscope and observe many
polygonal ce//s. Place some of the methyl-green acetic
stain under the cover-glass and note, after the cells are
stained, that they have definite boundaries and a central
nucleus.

Draw some of these scattered liver-cells.

The muscles.—TecunicaL Note.—Take a piece of intestine
from a freshly killed toad, wash it thoroughly and place it in a con-
centrated solution of salicylic acid in 70% alcohol for 24 hours,
then gradually heat until about the boiling-point, when the muscles
will fall to pieces. Transfer the preparation to a watch-crystal and
tease small bits of isolated muscle with dissecting-needles. Place
some of the teased muscle-fibres on a slide, cover with cover-glass,
and add a drop of the methyl-green acetic acid.

Note the small spindle-shaped muscle-fibres. Each
one of these fibres is a ce// possessing all of the structures
common to cells, namely, cell-wall, nucleus, etc.

Make a drawing of a few isolated fibres of muscle.

From this study of some of the tissues in a toad it will
be noted that in the first case we had in the blood
separate cells which moved about freely in the plasma.
In the second case, that of the epidermis, the cells are
fixed edge to edge, thus forming a thin tissue; while in
the third and fourth cases, that of the liver and muscle,
the cells are not only placed edge to edge, but aggregated

42 ELEMENTARY ZOOLOGY

into vast masses or bundles, in one case to form the liver
and in the other case a muscle. Jhe entire bedy ef the
toad is built up of a colony of simple units (cells) com-
bined in various forms to make all the various tissues and
organs.

CHAPTER .TX

THE MANY-CELLED ANIMAL BODY. — DIF-
hike WTLATION. OF THE CELL

The many-celled animal body.—In the study of cer-
tain of the tissues and organs of the toad we have learned
that the body of this animal is composed of many cells,
thousands and thousands of these microscopic structural
units being combined to form the whole toad. This
many-celled or multicellular condition of the body is true
of all the animals except the simplest, the unicellular
Pratezeasa. Corals, starfishes, worms, ‘clams, “crabs, «in-
sects, fishes, frogs, reptiles, birds, and mammals, all the
various kinds of animals in which the body is composed
of organs and tissues, agree in the multicellular character
of the body, and may be grouped together and called the
many-celled animals in contrast to the one-celled animals.
This division is one which is recognized by many syste-
matic zoologists as being more truly primary or funda-
mental than the division of animals into Vertebrates and
Invertebrates. The one-celled animals are called Pro-
tozoa, and the many-celled animals Metazoa.

Differentiation of the cell.—It is apparent at first
glance that the cells which compose the body of a many-
celled animal are not like the simple primitive cell which
makes up the body of the Aswba, nor are they like the
more complexly arranged cell of the Paramecium. Nor
are they all like each other. The cells in the toad’s blood
are of two kinds, the white blood-cells, which are very like

43

44 ELEMENTARY ZOOLOGY

the body of Ameéa, and the elliptical disk-like red blood-
cells. The cells composing the muscles are, moreover,
like neither kind of blood-cells, and the cells of which the
liver is composed are not like the cells of the muscles.
That is, there are many different kinds of cells in the body
of a many-celled animal. While the single cell which
composes the whole body of the Amwéa is able to do all
the things necessary to maintain life, the various cells in the
body of a complex animal are differentiated or specialized,
certain cells devoting themselves to a certain function or
special work, and others to other special functions. For
example, the cells which compose the organs of the
nervous system, the brain, ganglia, and nerves, devote
themselves almost exclusively to the function of sen-
sation, and they are especially modified for this purpose.
The highly specialized nerve-cells resemble very little the
primitive generalized body-cell of Amwba. The muscle-
cells of the complex animal body have developed to a
high degree that power of contraction which is possessed,
though in but slight degree, by Am@dba.. These muscle-
cells have for their special function this one of contraction,
and massed together in great numbers they form the
strongly contractile muscular tissue and muscles of the
body on which the animal’s power of motion depends.
The cells which line certain parts of the alimentary canal
are the ones on which the function of digestion chiefly
rests. “And so we might continue our Supvey on dhe
whole complex bedy. The point-of it all%s Guar the
thousands of cells which compose the many-celled animal
body are differentiated and specialized; that is, have
become changed or modified from the generalized primitive
amceboid condition, so that each kind of cell is devoted
to some special work or function and has a special struc-
tural character fitting it for its special function. In the
Protozoan body the single cell can perform and does per-

BIFFERENIIATION -OF THE CELL 45

form all the functions or processes necessary to the life of
the animal. Inthe Metazoan body each cell performs, in
co-operation with many other similar cells, some one
special function or process. The total work of all the
cells is the living of the animal.

CHAPT ERp 26

EAD Re

LABORATORY EXERCISE

TECHNICAL NOTE.—A/ydra lives in fresh water, attached to stones,
sticks, or decayed leaves. It can be found in most open fresh-water
ponds not too stagnant, often attached to Chara. There are two
species occurring commonly, /7. viridis, the green Ayan, and 77.
fuscus, the brown or flesh-colored /fydra. Both are very small
forms and have to be looked for carefully. Specimens should be
brought to the laboratory, put into a large dish of water and left
in the light. Aydra is best studied alive. Place a living specimen
attached to a bit of weed in a watch-crystal filled with water or on
a slide with plenty of water and examine with the low power of the
microscope. |

Note the cylindrical body (fig. 7, 245) wii ee lat
basal attachment and radzal tentacles (varying in number)
which crown the upper end and surround the centrally
located mouth. Note the movements of Hydra, its powers
of contraction, and method of taking in food.

TECHNICAL NOTE.-—To feed Hydra, place very small ‘“ water-
fleas” (DapfAnta sp.) in the water with it.

Observe the method by which ‘‘ water-fleas ’’ are taken
into the mouth. Food is caught on stinging cells (to be
studied later) and conveyed to the mouth by the tenta-
cles. Note that the cylindrical body encloses a cavity,
the digestive cavity. How.is this connected with the ex-
terior? If f/ydra captures prey too large ois no longer
hungry, the prey is released, :

46

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¢ “inhalas ud pores

Fic. 7 —A, Hydra fusca, with expanded body and a budding individual;
B, 4. fusca, contracted; C, H. fusca, part of outer surface of a tenta-
cle, greatly magnified. (A and B drawn from live specimens, C, froma
preparation ) D, Grantia sp. (a sponge}, three individuals; E, Grantia
sp., longitudinal section; F, Gvantza sp., spicules. (D, E, and F
drawn from preserved specimens. )

48 ELEMENTARY ZOOLOGY

TECHNICAL NOTE.—Place small slips of paper on the slide near
the Hydra, put cover-glass over the whole, and examine with the
low power of the microscope.

Note that the whole animal is made up of cells closely
joined. Are the cells in the tentacles all alike = Note
nodule-like projections above some of the cells; these are
stinging cells, or cnidoblasts. In some cases a small hair-
like process, the trigger hair or cuzdoczl, may be seen pro-
jecting above the surface of the cell. Note in some of the
tentacles dark-colored particles. These are food-particles
which have been taken through the mouth into the diges-
tive cavity and have passed thence into the tentacles.
The central digestive cavity communicates freely with the
cavities in the tentacles; for the tentacles ape. maierely.
evaginations of the body-wall.

Make drawings of the Hydra “ie and of the same
individual contracted.

TECHNICAL Note,—_From the preparation which you have under
the microscope pull out the slips of paper, thus letting the cover-
glass drop down on the specimen. With a small pipette put a
drop of anilin-acetic stain (see p. 451) on the slide at one side
of the cover-glass and with a piece of filter-paper draw the water
through from the other side of the cover-glass. When the Stain is
diffused press down the cover-glass gently. and examine the tentacles
first under a low power of the microscopé, then under a high one.

Note the distortion that the animal has undergone
through the action of the reagent. -Obseme mnie cnido-
blasts of the tentacles and note that many of them have
thrown out long whip-like processes (fig. 7, C). On
what parts of the body do the cnidoblasts occur? Care-
fully examine one of the cnidoblasts which has been dis-
charged and note a clear transparent bag-like structure
within, the zematocyst, to which is attached the long
whip-like process. In another cnidoblast cell which has
not been discharged note that the whip-like process 1s
coiled about inside of the bag-like structure. The whole

HYDRA 49

apparatus is like the inturned finger of a glove which can
be blown out by pressure from the inside. The mechan-
ism is simple. The cnidocil or trigger-hair is touched by
some animal, an impulse is conveyed to the delicate fibres
interspersed among the cells (nerve-cells) which stimulate
the cnidoblast cell, whereupon there is a contraction of
the contents and, the cnidoblast being compressed, the
inverted whip-like process turns wrong side out and im-
pales the animal on its points or barbs.

TECHNICAL NOTE.—The teacher should be provided with micro-
scopical sections, both transverse and longitudinal, of the Hydra
stained in some good general stain (hematoxylin or borax carmine).
If the teacher has no means of making such preparations, they may
be procured from dispensers of microscopical supplies.

From the cross-section of the Hydra make out the
general structure of the body. Note that it is a hollow
cylinder consisting of two well-defined layers of cells, an
outside ectoderm layer and an inner endoderm layer.
Between these two is yet another thin non-cellular layer
called the mesoglea.

Thus it will be seen that Hydra is made up of two
Evers of cells, the outer ectoderm or skin, which is
specialized to perform the office of capturing prey as well
as that of protection, and the inner endoderm, whch sur-
rounds the digestive cavity and performs the function of
digestion. The endoderm lines the body-cavity, particles
taken in as food being digested by certain digestive cells
which thrust out amceboid processes and ingest particles
of food. Other cells in the endoderm have long flagellate
processes which vibrate back and forth in the digestive
cavity, thereby creating currents in the water containing
food-particles.

Note, in a cross-section, that there are small ovoid or
cuboid cells at the bases of the large ectoderm cells.
These are the zuterstitial cells. Some of the interstitial

50 ELEMENTARY: ZOOLOGY

cells become modified and pushed up between the ecto-
derm cells to form cnidoblast cells: Manyeer the
endoderm as well as ectoderm cells have muscle-processes
which spread out from the base of the cell and which
serve to contract and expand the body.

TECHNICAL NOTE.—In the specimens which have been collected
perhaps two methods of reproduction will be observed. Place
healthy Hydre in a wide-mouthed jar in the sunlight with plenty
of water and food. Ina few days active budding will take place.

Observe the method of reproduction in Hydra. Com-
monly the parent produces small buds, which at first are
only evaginations of the body-wall, but which later
develop tentacles and a mouth of their own. Subse-
quently the bud becomes constricted at the base, separates
from the parent, and the young A/ydra begins a distinct
existence. |

Another mode of reproduction takes place which, in
distinction from the asexual method just mentioned, is
called sexual reproduction. This last is the method
common to most of the higher organisms. You may note
that in some AHydre@ there is a swelling or bulging of the
ectoderm of the body-wall in the region just below the
tentacles. These are the sferm-glands. Within these are
produced sperm-cells which break away in great clusters
to fertilize the ova, or eggs. Note a larger bulging of the
body-wall nearer the lower end of the body which, under
high power, has a granular appearance. This is the egg-
fland, in-which develops a single ovmm on2ze2, , Ihe
ovum breaks from its covering and is fertilized by sperm-
cells: from another individual. . In formise Mixes 7277,
where both sexes are represented in a single individual,
the organism is termed szonewcious cr hermaphroditic. In
connection with reproduction Chapter XIII should be
studied. 7

HYDRA 51
An instructive experiment can be performed by cutting

a Hydra into two or more parts, when (usually) each of
the various parts will develop into a complete Aydre.

This process may be called reproduction by fission, but it
rarely occurs naturally.

CHAPTER Xf
THE SIMPLEST. MANY-CELEER®D aii

Cell differentiation and body organization in Hydra.
—From the examination of Hydra we have learned that
there are true many-celled animals which are much less
complex in structure than the toad and crayfish. The
body of Hydra, like the body of the toad, is composed of
many cells, but these cells are of only a few different
kinds; that is, show but little differentiation. There is
relatively little division of the body into distinct organs.
Still, certain parts of the body devote themselves princi-
pally to certain particular functions. Thus all the food is
taken in through the single ‘‘mouth-opening’’ at the
apical frée end/ of the cylindrical body,” amd tiere are
certain organs, the tentacles, whose special business or
function it is to find and seize food and to convey it to the
mouth. After the food is taken into the cylindrical body-
cavity it is digested by special cells which line the cavity.
Some of these cells are unusually large, and each contains
one or more contractile vacuoles. From the free ends of
these cells, the ends which are next to the body-cavity,
project pseudopods or flagella. These protoplasmic
processes are constantly changing their form and number.
In addition to these large sub-amceboid cells there are, in
this inner layer of cells lining the pedy-casgm, = and
especially abundant near the base or bottom of the cavity,
many long, narrow, granular cells. These are gland-
cells which secrete a digestive fluid. The food captured
by the tentacles and taken in through the mouth-opening
disintegrates in the body-cavity, or digestive cavity as it

| te

THE SIMPLEST MANY-CELLED ANIMALS 53

meee called: [he digestive fluid secreted .by the
eland-cells acts upon it so that it becomes broken into
small parts. These particles are seized by the projecting
pseudopods of the sub-amceboid cells and taken into the
body-protoplasm of these cells. The cells of the outer
layer of the body do not take food directly, but receive
nourishment only by means of and through the cells of
the inner layer. The body-cavity of Hydra is a very
simple special organ of digestion.

In the outer layer of cells there are some specially
large cells whose inner ends are extended as narrow
pointed prolongations directed at right angles with the
rest of the cell. These processes are very contractile and
are called muscle-processes. Each one is simply a
specially contractile continuation of the protoplasm of the
cell-body. There are also in this layer some small cells
very irregular in shape and provided with unusually large
nuclei. ‘These cells are more irritable or sensitive than
the others and are called nerve-cells. We have thus in
Hydra the beginnings of muscular organs and of nerve- -
organs. But how simple and unformed compared with
the muscular and nervous systems of the toad and crayfish!
There is no circulatory system, nor are there any special
organs of respiration.

But Hydra is far in advance of Amba or Paramecium.
Its body is composed of thousands of distinct cells. Some
of these cells devote themselves especially to food-taking,
some especially to the digestion of food; some are
specially contractile. and on them the movements of the
body depend, while others are specially irritable or sensi-
tive, and on them the body depends for knowledge of the
contact of prey or enemies. In the cnidoblast cells, those
with the stinging threads, there is a very wide departure
from the simple primitive type of cells. There is in
Hydra a manifest differentiation of the cells into various

54 ELEMENTARY ZOOLOGY

kinds of cells. The beginnings of distinct tissues and
organs are indicated.

Degrees in cell differentiation and body organization.
—In the study of the cellular constitution of the tissues
and organs of the toad, we found to what a high degree
the differentiation of the cells may attain, and in the study
of the anatomy of the toad we found how thoroughly these
differentiated cells may be combined and organized into
body-parts or organs. The body of the toad is made up
of distinct organs, each composed of highly differentiated
or specialized cells. The body of Hydra is composed of
cells for the most part only slightly differentiated and
hardly recognizably grouped or combined into organs.
These two conditions are the extremes im tie mody-
structure of the many-celled animals. Between them
is a host of intermediate conditions of cell differentia-
tion and body organization. When we come to the
study of other’ members of the creat “braneh of simple
many-celled animals to which //ydra_ belongs (see
Chapter XVII), it will be found “that seme ar chem
show a slight advance in complexity beyond A/ydra.
Higher in the scale of animal life the forms will be found
still more and more complex, with ever-increasing differ-
entiation of the cells, with the combination of the differ-
entiated cells into distinct organs, and the co-ordination
of organs into systems of organs up to the extreme shown
by the birds and mammals. And hand in hand with this
increasing complexity of structure goes ever-increasing
complexity or specialization of function. Breathing is a
simple function. or process with /Yydra, where each body-
cell takes up oxygen for itself, but it is a complex business
with the toad, or with a bird or mammal, where certain
complex structures, the lungs and accessory parts, and
the heart, blood-vessels and blood all work together . to
distribute oxygen to all parts of the body.

CHAPTER -Xit

Pryor MeENT: OF: THE ‘TOAD

PEL AND LABORATORY: EXERCISE

TECHNICAL NOTE.—As the work of this chapter, or some similar
work in getting acquainted with the postembryonic development
of a many-celled animal, should be done early in the course, and
as most schools open in the fall, it will perhaps be impossible to
make this first study of development from live specimens in the field.
In such case the examination of a series of prepared specimens,
previously obtained by the teacher, must be resorted to. In the
spring the development of several kinds of animals, including the
toad, can be studied from live specimens in the field or in breeding-
cages and aquaria in the laboratory. The eggs of the toad may be
found in April and May (the toads are heard trilling at egg-laying
time) in ponds. The eggs look like the heads of black pins, and are
in single rows in long strings of transparent jelly, which are usually
wound around sticks or plant-stems at the bottom of the pond near
the shore. Bring some of these strings into the schoolroom and
keep them in water in shallow dishes. Keep them in the light, but
not in direct sunlight. In the dishes put some small stones and
mud from the pond, arranging them ina slope, thus making different
depths of water. Stones with green algz on should be selected, for
algze are the food of the tadpoles. The eggs will hatch in two or
three days, and if too many tadpoles are not kept in the dish, and
the little aquarium be well cared for, the whole postembryonic de-
velopment of the toad can be well observed. For the study of the
development from prepared specimens the teacher should have a
- complete series of stages from egg to adult toad in alcohol. The
specimens may be examined by the students in connection with a
talk from the teacher on the life-history of the toad.

If the study is made from prepared specimens, make
drawings of egg-strings, and of a single egg magnified
and shaded to indicate its color. Draw each specimen of
the series of tadpoles, noting in the youngest the presence

Se eticeand tail and absence of legs and eyes; in the
of)

56 | ELEMENTARY ZCOLOGY

older the appearance of eyes, the shrivelliine vor pieseills,
shrinking of the tail and development of legs; in the still
older the characteristic shape, in miniature, of the adult
toad. |

In observing the course of development of the living
specimens there should be made, in addition to the draw-
ings, notes showing the duration of the egg stage, and
the time elapsing between all important changes (as seen
externally) in the body of the young. Observations and
notes on the general behavior of tadpoles should also be
made; note the swimming, the feeding, the gradual leav-
ine@ of the water cte-

In addition to the easily seen external changes in the
body, very important ones in the internal organs take
place during development. Perhaps the most important
of these concerns the lungs. The youne gilled? toad
breathes as a fish does, but gradually its gills are lost,
while at the same time lungs develop and the tadpole
comes to the surface to breathe air like any lunged aquatic
animal. The toad on leaving the water changes its diet
from vegetable to animal food; a tadpole feeds on aquatic
alow; a. toad. preys on insects. Cotelarees aii sec
change in habit, the intestine during development under-
goes some marked changes, becoming relatively dimin-
ished in length.

For an account’ of ‘the development of tie toad see
Gage's ‘Life-history of a Toad - or @iedec ae Wine
Common Toad.”

CHAP PER xt

MULTIPLICATION AND DEVELOPMENT.—MUL-
PieiCA TION: OF ONE-CELLED ANIMALS

Multiplication.—We know that any living animal has
parents; that is, has been produced by other animals
which may still be living or be now dead or, as with
Ameba, may have changed, by division, into new indi-
viduals. Individuals die, but before death, they produce
other individuals like themselves. If they did not, their
kind or species would die with them. This production
of new animals constantly going on is called the repro-
duction or multiplication of animals. The process is
well called multiplication, because each female animal
normally produces more than one new individual. She
may produce only one ata time, one a year, as many of
the sea-birds do or as the elephant does, but she lives
many years. Or she may produce hundreds, or thou-
sands, or even millions of young in a very short time.
Pemuwser lays 10,000’ eggs at a. time. Nearly nine
millions of eggs have been taken from the body of a
thirty-pound female codfish. As a matter of fact but
very, very few of these eggs produce new animals which
reach maturity. From the 10,000 eggs produced by the
lobster each year an average of but two new mature
lobsters is produced. There is always a struggle for food
and for place going on among animals, for many more
are produced than there are food and room for, and so of
all the new or young animals which are born the great

57

58 ELEMENTARY ZOOLOGY

majority are killed before they reach maturity. In a later
chapter more attention will be given to this great struggle
for life. |

In the preceding paragraph it has been stated that
‘‘we know that any living animal has parents; that is, has
been produced by other animals which may still be living
or be now dead.’ This is a statement, however, which
has found complete acceptance only in modern times.
It is a familiar fact that a new kitten comes into the world
only through being born; that it is the offspring of parents
of its kind. But we may not be personally familiar with
the fact that anew starfish comes into the world only as
the production of parent starfish, or that a new earth-
worm can be produced only by other earthworms. But
naturalists have proved these statements. . All life comes
from life; all organisms are produced by other organisms.
And new individuals are produced by other individuals of
the same kind: That. these’ statemrents are tic. al!
modern observations and investigations of the origin of
new individuals prove. But in the days of the earlier
naturalists the life of the microscopic organisms like
Ameba and Paramecium, and even that of many of the
larger but unfamiliar animals, was shrouded in mystery.
And various and strange beliefs were held regarding the
origin of new individuals.

Spontaneous generation.—The ancients believed that
many animals were spontaneously generated. The early
naturalists thought that flies arose by spontaneous genera-
tion from the decaying matter of dead animals. Frogs
and many insects were thought to be generated spontane-
ously from mud, and horse-hairs in water were thought
to change into water-snakes. But such beliefs were
easily shown to be based on error, and have been long
discarded by zoologists. But the belief that the micro-
scopic organisms, such as bacteria and infusoria, were —

MULTIPLICATION AND DEVELOPMENT 59

spontaneously generated in stagnant water or decaying
organic liquids was held by some naturalists until very
recent times. And it was not so easy to disprove the
assertions of such believers. If some water in which-
there are apparently no living organisms, however
minute, be allowed to stand for a few days, it will
come to swarm with microscopic plants and animals.
Any organic liquid, as a broth or a vegetable infusion,
exposed to the air for a short time becomes foul through
the presence of innumerable microsccpic organisms. But
it has been certainly proved that these organisms are not —
spontaneously produced in the water or organic fluid.
A few of them enter the water from the air, in which there
are always greater or less numbers of spores of micro-
scopic organisms. These spores germinate quickly when
they fall into water or some organic liquid, and the rapid
succession of generations soon gives rise to the hosts of
bacteria and one-celled animals which infest all standing
water. If all the active organisms and inactive spores in
a glass of water are killed by boiling the water, and this
sterilized water be put into a sterilized giass, and this
glass be so well closed that germs or spores cannot pass
from the air without into the sterilized liquid, no living
animals will ever appear in it. We know of no instance
of the spontaneous generation of animals, and all the
animals whose life-history we know are produced by other
animals of the same kind.

Simplest multiplication and development.—The sim-
plest method of multiplication and the simplest kind of
development shown among animals are exhibited by such
simple animals as Amwba and Paramecium. The pro-
duction of new individuals is accomplished in Amada by
a simple division or fission of its body (a single cell) into
two practically equivalent parts. An Asmeba which has
grown for some time contracts all of its finger-like

a ELEMENTARY ZOOLOGY

_ processes, the pseudopodia, and its body becomes con-
stricted. This constriction or fissure increases inwards
so that the body is soon divided fairly in two. There are
now two Amevve, each half the size of the original one;
each; indeed, actually one-half-of the ermemabomes. fhe
original dmeba was the parent; the two halves of it are
the young. Each of the young possesses all of the char-
acteristics and powers of the parent; each can move, eat,
feel, grow, and reproduce by fission. The only change
necessary for the young or new Amwba to become like its
parent, is that of simple growth to a size about twice its
present size. The development here as veduecdato: 2
minimum. Just as the simplest animals perform the other
life-processes, such as taking and digesting food, breath-
ing and feeling, in an extremely primitive simple way, so
do they perform the necessary life-process of reproduction
or multiplication in the simplest way shown among
animals.

In the case of Paramecium the process of multiplication
is slightly more complex than that of Amwéa in the fact
that sometimes before the simple fission of the body takes
place the interesting phenomenon of conjugation occurs.
Paramecium may reproduce itself for many generations
by simple fission, but a generation finally appears in which
conjugation takes place. Two individuals come together
and each exchanges with the other a part of its nucleus.
Then the two individuals separate and each divides into
two. - The result of the conjugation, or the coming
together, of two individuals with mutual interchange of
nuclear substance is to give to the new Paramecia pro-
duced by the conjugating individuals a body which
contains part of the body-substance of two distinct indi-
viduals. If the two conjugating individuals differ at all—
and they always do differ, because no two individual
animals, although belonging to the same species, are

MULTIPLICATION AND DEVELOPMENT 61

exactly alike—the new individual, made up of parts of
each of them, will differ slightly from both. Nature
seems intent on making every new individual differ slightly
from the individual which precedes it. And the method
of multiplication which Nature has adopted to produce
the result is the method which we have seen exhibited in
its simplest form in the case of Paramecium-—the method
of having two individuals take part in the production of
a new one. 3

he development of the new Paramewcza is a little more
complex than that of dmaba. Not only must the new
Paramecium grow to the size of the original one, but it
must develop those slight, but apparent, modifications of
the parts of its body which we can recognize in thie full-
crown, fully developed Paramecium individual. A new
mouth-opening must develop on the new _ individual
formed of the hinder half of the original Paramaczum and
new cilia must be developed. Thus there is a slight
advance in complexity of development, just as there is in
complexity of structure in Paramacium as compared with
Amaba. Inthe many-celled animals this complexity of
development is carried to an extreme.

Birth and hatching.—When a young animal is born
alive, it usually resembles in appearance and structure the
parent, although of course it is much smaller, and requires
always a certain time to complete its development and
become mature. A young kangaroo or opossum is
carried for some time after its birth in an external pouch
on the mother’s body and is a very helpless animal. A
young kitten is born with eyes not yet opened and must
be fed by the mother for several weeks. On the other
hand young Rocky Mountain sheep are able to run about
swiftly within a few hours after birth.

62 ELEMENTARY ZOOLOGY

Most animals appear first as eggs laid by the mother.
_ This-ts true of the birds, the reptiles, the fetes. the
insects, and most of the hosts of invertebrate animals.
This” ege smay. be. cared for iby thie parent as with the
birds, -or ‘simply deposited in a safe place as with most
insects, or perhaps dropped without care into the water as
with most marine invertebrates. The young animal which
issues from. the egg may at the time) of sto aaacenine
resemble the parent in appearance and structural character
(although always much smaller) as with the birds, some
of the insects, and many of the other animals. Or it may
issue in a so-called favval condition, in which it resembles
the parent but slightly or not at all, as is*thesease with
the gill-bearing, legless, tailed tadpole of the frog or the
crawling, wingless, wormlike caterpillar of the butterfly,
or the maggot of the house-fly.

Life-history.— Any animal which hatches from an egg
has undergone a longer or shorter period of development
within the egg-shell before hatching. The development
of an animal from first germ-cell to the time it leaves the
ego, for example, the development of the- crab elec
from the first cell to time of hatching, is, called its em-
bryonic development; and the development from then on,
for example, that of the chick to adult len ‘eg psoq@srer,
or that of tadpole to frog, is called the post-embryonic
development. Beginning students of animals cannot
study the embryonic development (emdryology) of animals
readily, but they can in many cases, easily follame tre
course of the post-embryonic development, and this study
will always be interesting and valuables | Wirem. the
‘« life-history ’’ of an animal is spoken of in this book, or
other elementary text-book of zoology, it is the history
of the life of the animal from the time ofits birth of
hatching to and through adult condition that is meant,
not the complete life-history from beginning single egg-

MULTIPLICATION AND DEVELOPMENT 623

Gellto the end: In all of the study of the different kinds
of animals to which the rest of this book is devoted,
attention will be paid to their life-history.

PART II
SYotiHMATiC - ZOOLOGY

CHAPTER XIV
fie ool PiCATION: OF. ANIMALS

Basis and significance of classification.—It is the
common knowledge of all of us that animals are classified:
that is, that the different kinds are arranged in the mind
of the zoologist and in the books of natural history, in
various groups, and that these various groups are of
different rank or degree of comprehensiveness. A group
of high rank or great comprehensiveness includes groups
of lower rank, and each of these includes groups of still
lower rank, and so on, for several degrees. For example,
we have already learned that the toad belongs to the
great group of back-boned animals, the Vertebrates, as
the group is called. So do the fishes and the birds, the
reptiles and the mammals or quadrupeds. But each of
these constitutes a lesser group, and each may in turn be
subdivided into still lesser groups.

In the early days of the study of animals and plants
their classification or division into groups was based on
the resemblances and the differences which the early
naturalists found among the organisms they knew. At
first all of the classifying was done by paying attention
to external resemblances and differences, but later when

naturalists began to dissect animals and to get acquainted
65

66 ELEMENTARY ZOOLOGY

with the structure of the whole body, the differences and
likenesses of inner parts, such as the skeleton and the
organs of circulation and respiration, were taken into ac-
count. At the present time and ever since the theory of
descent began to be accepted by naturalists (and there is
practically no one who does not now accept it), the classifi-
cation of animals, while still largely based on resemblances
and differences among them, tells more than the simple
fact that animals of the same group resemble each other
in certain structural characters. It means that the mem-
bers of a group are related to each other by deseend, that
is, genealogically. They are all the descemdamre soi a
common ancestor; they are all sprung from a common
stock. And this added meaning of classification explains
the older meaning; it explains why the animals are alike.
The members of a group resemble each other in structure
because they are actually blood relations. But as their
common ancestor lived ages ago, we can learn the history
of this descent, and find out these blood relationships
among animals only by the study of forms existing now,
or through the fragmentary remains of extinct animals
preserved in the rocks as, fossils: As "ap miaiercie a iach
we usually learn of the existence of this actual blood-
relationship, or the fact of common ancestry among
animals, by studying their structure and finding out the
resemblances and differences among them. If much alike
we believe them closely related; if less alike we believe
them. less closely related, and so on. So atteralli@eseuoh
the present-day classification means something more,
means a great deal more, in fact, than the classification
of the earlier naturalists means, it is largely based on
and determined by resemblances and differences Just as
was the old classification. Sometimes the fossil remains
of ancient animals tell us much about the ancestry and
descent of existing forms. For example, the present-day

THE OCLASSHICATION OF ANIMALS 67

one-toed horse has been clearly shown by series of fossils
to be descended from a small five-toed horse-like animal
which lived in the Tertiary age.

Importance of development in determining classifica-
tion.—A very important means of determining the
relationships among animals is by studying their develop-
ment. If two kinds of animals undergo very similar
development, that is, ifin their development and growth
from egg-cell to adult they pass through similar stages,
bacyeaie early telated. And by the correspondence or
lack of correspondence, by the similarity or dissimilarity
of the course of development of different animals much
regarding their relationship to each other is revealed.
Sometimes two kinds of animals which are really nearly
related come to differ very much in appearance in their
fully developed adult condition because of the widely differ-
ent life-habits the two may have. But if they are nearly
related their developmental stages will be closely similar
until the animals are almost fully developed. For exam-
ple, certain animals belonging to the group which includes
the crabs, lobsters, and crayfishes, have adopted a para-
sitic habit of life, and in their adult condition live attached
footed pocies of certain kinds of-true crabs. ~:As these
parasites have no need of moving about, being carried by
their hosts, they have lost their legs by degeneration, and
the body has come to be a mere sac-like pulsating mass,
attached to the host by slender root-like processes, and
not resembling at all the bodies of their relatives the
crabs and crayfishes. If we had to trust, in making out
our Classification, solely to structural resemblances and
differences, we should never classify the Sacculina (the
parasite) in the group Crustacea, which is the group in-
cluding the crabs and lobsters and crayfishes. But the
young Sacculina is an active free-swimming creature
resembling the young crabs and young shrimps. Bya

68 ELEMENTARY ZOOLOGY

study of the development of Sacculina we find that it is
more closely related to the crabs and crayfishes and the
other Crustaceans than to any other animals, although in
adult condition it does not at all, at least in external ap-
pearance, resemble a crab or lobster.

Scientific names.-—To classify animals then, is to deter-
mine their true relationships and to express these relation-
ships by a scheme of groups. To these groups proper
names are given tor convenience 4m felernine@seo, em:
These proper names are all Latin of tGfeck simply
because these classic languages are taught in the schools
and colleges of almost all the countries in the world, and
are thus intelligible to naturalists of all nationalities. In
the older, days, indeed, -all -the- sciemiiic. jawake sie
descriptions and accounts of animals and plants, were
written: in Latin,- and . now. most: ef ) fie) teenmical
words used in naming the parts of agile and
plants are. Latin. So that Latin aay oe sealed. thie
language of science. For most of the groups of animals
we have English names as well as Greek or Latin ones
and when talking with an English-speaking person we
can use these names. But when scientific men write of
animals they use the names which have been agreed on
by naturalists of all nationalities and which are understood
by ‘all of these naturalists. These, Latin; ama are
names of animals laughed at by non-scientific persons as
‘‘jaw-breakers,’’ are really a great convenience, and save
much circumlocution and misunderstanding.

>)

AN- EXAMPLE OF ‘CLASSIFICATION

TECHNICAL NOTE.—There should be provided a small set of bird-
skins which will serve just as well as freshly killed birds,and which
may be used for successive classes, thus doing away with the neces-
sity of shooting birds. The birds suggested for use are among the
commonest and most easily recognizable and obtainable. They may
be found in any locality at any time of the year. The skins can

THE CLASSIFICATION OF -ANIMALS 69

be made by some boy interested in birds and acquainted with
making skins, or by the teacher, or can be purchased from a natur-
alists’ supply store, or dealer in bird skins. The skins will cost
about 25 cents each. This example or lesson in classification can
be given just as well of course with other species of birds, or with
a set of some other kinds of animals, if the teacher prefers. Insects
are especially available, butterflies perhaps offering the most readily
appreciated resemblances and differences.

Species.—Examine specimens of two male downy
woodpeckers (the males have a scarlet band on the back
erecte ead) (In the western States uses Gardiner’s
downy woodpecker.) Note that the two birds are of the
same size, have the same colors and markings, and are
im) aul Gespects alike. They are of the satne kind; simply
two individuals of the same kind of animal. There are
hosts of other individuals of this kind of bird, all alike.
This one kind of animal is called a speczes. ‘The species
is the smallest * group recognized among animals. No at-
tempt is made to distinguish among the different individuals
of one kind or species of animal as we do in our own case.

Examine a specimen of the female downy wood-
Meee = tis like the male except that it does not have
the scarlet neck-band. But despite this difference we
know that it belongs to the same species as the male
downy because they mate together and produce young
woodpeckers, male and female, like themselves. There
are thus two sorts of individuals,t male and female, com-
prised in each species of animal. A speczes is a group of
animals comprising similar individuals which produce
new individuals of the same kind usually after the mating
together of individuals of two sexes which may differ
somewhat in appearance and structure.

* The lesser group called varzety, or subspecies, we may leave out of
consideration for the present.

+ Some species of animals are not represented by male individuals ; and
in some all the individuals are hermaphrodites, as explained in chapter
XIV.

70 ELEMENTARY ZOOLOGY

Examine a male hairy woodpecker anda female; (in
western States substitute a Harris’s hairy woodpecker).
Note the similarity in markings and structure to the
downy. Note the marked difference in size. Make notes
of measurements, colors and markings, and drawings of
bill and feet, showing the resemblances and the differ-
ences between the downy woodpecker and the hairy
woodpecker. ‘Lhese two kinds of woodpeckers are very
much alike, but the hairy woodpeckers are always much
larger (nearly a half) than the downy woodpeckers and
the two kinds never mate together. The hairy wood-
peckers constitute another species of bird.
Genus.—Examine now a flicker ‘the yellow-shafted
or golden-winged flicker in the East, the red-shafted
flicker in the West). Compare it with the downy wood-
pecker and the hairy woodpecker. Make notes referring
to the differences, also the resemblances. = iinewaicker
is very differently marked and colored and is also much
larger than the downy woodpecker, but its bill and feet
and general make-up are similar and it is obviously a
‘‘woodpecker.’’ Itis, however, evidently another species
of woodpecker, and a species which differs from either the
downy or the hairy woodpecker much more than these
two species differ from each other. There are two other
species of flickers in North America which, although
different from the yellow-shafted flicker, yet resemble it
much more than they do the downy and hairy wood-
peckers or any other woodpeckers. We can obviously
make two groups of our woodpeckers so far studied,
putting the downy and hairy woodpeckers (together with
half a dozen other species very much like them) into one
group and the three flickers together into another group.
Each of these groups is called a gexus, and genus is thus
the name of. the next group above the species, “2 aenus
usually includes ‘several; or if there be Such, “many,

tHe -OLASSIFICA TION OF” ANIMALS val

similar species. Sometimes it includes but a single known
species. That is, a species may not have any other
species resembling it sufficiently to group with it, and so
it constitutes a genus by itself. If later naturalists should
find other species resembling it they would put these new
species into the genus with the solitary species. Each
genus of animals is given a Greek or Latin name, of a
single word. Thus the genus including the hairy and
downy woodpeckers is called Dryobates,; and the genus
including the flickers is called Colaptes. But it is neces-
sary to distinguish the various species which compose the
genus Colaptes, and so each species is given a name which
is composed of two words, first the word which is the
name of the genus to which it belongs, and, second, a
word which may be called the species word. The species
word of the Yellow-shafted Flicker is auratus (the Latin
word for golden), so that its scientific name is Colaftes
auratus. ‘he natural question, Why not have a single
word for the name of each species ? may be answered thus:
@here are already known more than 500,000 distinct
species of living animals; it is certain that there are no
less than several millions of species of living animals;.
new species are being found, described and named con-
stantly; with all the possible ingenuity of the word-
makers it would be an extremely difficult task to find or
to build up enough words to give each of these species a
Eepatate mame. [his is not attempted... -The same
Species word 1s often used for several different species of
animals, but never for more than one species belonging
fea eiven fenus. And the names. ‘of the genera are
Hever. duplicated. (There are, of course, much fewer
genera than species, and the difficulty of finding words
for them is not so serious.) Thus the genus word in the
two-word name of a species indicates at once to just what
particular genus in the whole animal kingdom the species

72 ELEMENTARY ZOOLOGY

belongs, while the second or species word distinguishes it
from the few or many other species which are included in the
same genus. [his manner of naming species of animals
and plants (for plants are given their scientific names
according to the same plan) was devised by the great
Swedish naturalist Linnzeus in the mildle se) the
eighteenth century and has been in use ever since.

Family.—Examine a red-headed woodpecker (Wela-
nerpes erythrocephalus) and a sapsucker (Sphyrapicus
varius) and any other kinds of woodpeckers which can be
got. Find out in what ways the hairy and downy
woodpeckers (genus Dyryobates), the flickers (genus
Colapies) and the other woodpeckers resemble each other.
Examine especially the bill, feet, wings and tail. These
birds differ in size, color and markings, but they are
obviously all alike in certain important structural respects.
We recognize them all as woodpeckers. We can group
all the woodpeckers together, including several different
genera, to form a group which is called a family. A
family is a group of genera which have a considerable
number of common structural features. Each family is
given a proper name consisting of a single word. The
family of woodpeckers is named Piczde.

We have already learned that resemblances between
animals indicate (usually) relationship, and that classify-
ing animals is simply expressing or indicating these
relationships. When we group several species together
to form a genus we indicate that these species are closely
related. And similarly a family is a group of related
genera.

Order.—There are other groups* higher or more com-

* Each of these higher groups has a proper name composed of a single
word. In the case of no-group except the species is a name-word ever
duplicated. Each genus, family, order, or higher group has a name-word
peculiar to it, and belonging to it alone.

THE CLASSIFICATION OF ANIMALS 2

prehensive than families, but the principle on which they
are constituted is exactly the same as that already
explained. Thus a number of related families are grouped
together to form an order. All the fowl-like birds, in-
cluding the families of pheasants, turkeys, grouse and
quail, all obviously related, constitute the order of gal-
linaceous birds called Galiin@. ‘The families of vultures,
hawks and owls constitute the order of birds of prey,
bie tea 7io7¢es, -and the families of the thrushes, wrens,
warblers, sparrows, black-birds, and many others con-
stitute the great order of perching birds (including all the
singing birds) called the Passeres.

Class and branch.—But it is evident that all of these
orders, together with the other bird orders, ought to be
combined into a great group, which shall include all the
birds, as distinguished from all other animals, as the
momen, aasects, etc. Such a group of related: orders: is
allem earadss.--lhe class of birds is named Aves... Vhere
is a Class of fishes, Pzsces, and one of frogs and salaman-
ders, Latrachia, one of snakes and lizards called Reptzha,
and one of the quadrupeds which give milk to their young
called Mammala. Each of these classes is composed of
several orders, each of which includes several families and
so omcown. but these five classes of Pisces, Batrachia,
Reptilia, Aves and Mammals agree in being composed of
animals which have a backbone or a backbone-like struc-
ture, while there are many other animals which do not
Nawea backpone, such as the insects, the starfishes, etc.
Hence these five backboned classes may be brought
together into a higher group called a branch or phylum.
They compose the branch of backboned animals, the
branch Vertebrata; all the animals like the starfishes,
sea-urchins and sea-lilies which have the parts of their
body arranged in a radiate manner compose the branch
Echinodermata; all the animals like the insects and

TA ELEMENTARY ZOOLOGY

spiders and centipedes and crabs and crayfishes which
have the body composed of a series of segments or rings
and have legs or appendages each composed of a series
of joints or segments make up the branch Arthropoda.
And so might be enumerated all the great branches or
principal groups into which the animal kingdom is divided.
In the remainder of this book the classification of
animals is always kept in sight, and the student will see
the terms species, genus, family, order, ete:.. gracucally
used. In it all should be kept constantly imeaiind the
significance of classification, that is, the existence of actual
relationships among animals through descent.

CHAPTER XV

BRANCH PROTOZOA: THe ONE-CEELE D
ANIMALS

Of this group the structure and life-history of the
Amceba (Amada sp.) and the Slipper Animalcule (Para-
mectum sp.) have already been treated in Chapter VI.
Another example is the

BELL ANIMALCULE | Vorticella sp.)

TECHNICAL NOTE.—Specimens of Vorticella may usually be
found in the same water with Am@edba and Paramecium. The
individuals live together in colonies, a single colony appearing to
the naked eye as a tiny whitish mould-like tuft or spot on the
surface of some leaf or stem or root in the water. Touchsucha
spot with a needle, and if it is a Vorticellid colony it will contract
instantly. Bring bits of leaves, stems, etc., bearing Vorticellid
colonies into the laboratory and keep in a small stagnant-water
aquarium (a battery-jar of pond-water will do).

Examine a colony of Vortecella in a watch-glass of
water or in a drop of water ona glass slide under the
microscope. Note the stemmed bell-shaped bodies
which compose the colony. Each bell and stem together
form an individual Vortzcella (fig. 8.) How. are the
members of the colony fastened together ? Tap the slide
and note the sudden contraction of the animals; also the
details of contraction in the case of an individual. Watch
the colony expand; note the details of this movement in
the case of an individual.

Make drawings showing the colony expanded and con-
tracted.

With higher power examine a single individual. Note
73

70 ELEMENTARY ZOOLOGY

the thickened, bent-out, upper margin of the bell. This
margin is called the perzstome. With
what ts it fringed ? The free end of the
bell is nearly filled by a central disk,
the efzstome, with arched upper surface
and: a circlet of cia Between the
epistome and peristome is a groove,
the mouth or vestibule, which leads
into the body. “Study sae simecina!
structure of the ~“transparemr.= bell-
shaped body. Note the differentia-
tion of the protoplasm comprising the
body into an inner transparent color-
less exdosarc containing various dark-
colored granules, vacuoles, oil-drops,
etc., and an outer uniformly granular
ectosare not containing vacuoles. Is
the stalk formed of ettesare or en-
dosarc or of both ? ~ Note tae seurved
nucleus lying in the endosarc. (This
may be difficult to distinguish in some

specimens.) Note the numerous large
Rie 82 ey icela ep circular granules, the food vacuoles.

one individual with Note the contractile vesicle, larger and

stalk coiled, and one

with stalk. extended. Clearer than the toodamact@lee =) Whe

Crom: the thin cazzc/e lining the whole body
externally. A high magnification will show fine trans-
verse ridges or rows of dots on the cuticle.

Make a drawing showing the internal structure.

Observe a living specimen carefully for some time to
determine all of its movements. Note the contraction
and extension of the stalk, the movements of the cilia of
peristome and epistome, the flowing or streaming of the
fluid endosare (indicated by the movements of the. tood
vacuoles), the behavior of the contractile vesicle.

BRANCH PROTOZOA: THE ONE-CELLED ANIMALS 77

Make notes and drawings explaining these motions.

Specimens of Vortzcella may perhaps be found dividing,
or two bell-shaped bodies may be found on a single stem,
one of the bodies being sometimes smaller than the other.
These two bodies have been produced by the longitudinal
division or fission of a single body. In this process a
cleft first appears at the distal end of the bell-shaped
body, and gradually deepens until the original body is
divided quite in two. ‘The stalk divides for a very short
distance. One of the new bell-shaped bodies develops a
circlet of cilia near the stalked end. After a while it
breaks away and swims about by means of this basal
circlet of cilia. Later it settles down, becomes attached
by its basal end, loses its basal cilia and develops a stalk.
— occurs sometimes, but it is unlike the
conjugation of Paramceium in two important points:
Firstly, the conjugation is between two dissimilar forms;
an ordinary large-stalked form, and a much smaller free-
swimming form which has originated by repeated division
of a large form. Secondly, the union of the two is a
complete and permanent fusion, the smaller being
absorbed into the larger. This permanent fusion of a
small active cell with a relatively large fixed cell, followed
by division of the fused mass, presents a striking analogy

to the process of sexual reproduction occurring in higher
animals.’

OTHER PROTOZOA

Besides the Amwba, Paramecium, and Vorticella there
are thousands of other Protozoa. Most of them live in
water, but a few live in damp sand or moss, and some
live inside the bodies of other animals as parasites. Of
those which live in water some are marine, while others
are found only in fresh-water streams and lakes.

~8 ELEMENTARY ZOOLOGY

_ Form of body.—The Protozoa all agree in having the
body composed for its whole lifetime of a single cell,*
but they differ much in shape and appearance. Some of
them are of the general shape and character of Amwéa,
sending out and retracting blunt, finger-like pseudopodia,
the body-mass itself having no fixed form or outline but

Fic. 9.—Sun animalcule, a fresh-water protozoan with a siliceous skeleton,
and long thread-like protoplasmic prolongations. (From life.)

constantly changing. Others have the body of definite
form, spherical, elliptical, or flattened, enclosed by a thin
cuticle, and having a definite number of fine thread-like
or hair-like protoplasmic prolongations called flagella or

* In some Protozoa a number of similar cells temporarily unite to form a
colony, but each cell may still be regarded as an individual animal. |

BRANCH PROTOZOA: THE ONE-CELEED ANIMALS — 79

cilia. Many of the familiar Protozoa of the fresh-water
ponds always have two whiplash-like flagella projecting
from one end ofthe body. By means of the lashing of
these flagella in the water the tiny creature. swims about.
Others have many hundreds of fine short cilia scattered,
sometimes in regular rows, over the body-surface. The
Protozoan swims by the vibration of these cilia in the
water.

There is no stagnant pool, no water standing exposed
in watering-trough or bar-
rel which does not contain
thousands of individuals of
the one-celled animals.
And in any such stagnant
water there may always be
found several or many dif-
ferent kinds or species. A
drop of this water examined
with the compound micro-
scope will prove to be a
tiny world (all an ocean)
with most of its animals and
plants one-celled in struc-
ture. A few many-celled
animals will be found in it
preying on the one-celled
ones. There are sudden FIG. 10.—Stentor sp.; a protozoan

. which may be fixed, like Vortzcel/a,
and violent deaths here, and or free-swimming, at will, and

. e . which has the nucleus in the shape
births (by fission of the of a string or chain of bead-like

parent) and active locomo- bodies. ‘The figure shows a single

; . individual as it appeared when fixed,
tion and food-getting and with elongate, stalked body, and as

crowth and all of the busi- it appeared when swimming about,
3 : with contracted body. (From life.}
nesses and functions of life

which we are accustomed to see in the more familiar
world of larger animals.

$0; ELEMENTARY ZOOLOGY

Marine Protozoa.—One usually thinks of the ocean as
the home of the whales and the seals and the sea-lions, and
of the countless fishes, the cod, and the herring, and the
mackerel. Those who have been on the seashore will
recall the sea-urchins and starfishes and the sea-anemones
which live in the tide-pools. On the beach there are the
innumerable shells, too, each representing an animal
which has lived in the ocean. But more abundant than
all of these, and in one way more important than all,
are the myriads of the marine Protozoa.

Although the water at the surface of the ocean appears
clear and on superficial examination seems to contain no
animals, yet in certain parts of the ocean (especially in
the southern seas) a microscopical examination of this
water shows it to be swarming with Protozoa. And not
only is the water just at the surface inhabited by one-
celled animals, but they can be found in all the water from
the surface toa great depth below it. Ima pimp of this
ocean-water there may be millions of these minute
animals. In the oceans of the world the number of them
is inconceivable. And it is necessary that these Protozoa
exist in such great numbers, for they and the marine one-
celled plants (Protophyta) supply directly or indirectly
the food for all the other animals of the ocean.

Among all these ocean Protozoa none aregmore in-
teresting than those belonging to the two orders Forami-
nifera (fig. 11) and Radiolaria. ‘The many kinds belong-
ing to these orders .secrete a tiny shel (amgiate | in
the Foraminifera, of silica in the Radiolaria) which en-
closes most of the one-celled body. These minute shells
present a great variety of shape and pattern, many being
of the most exquisite symmetry and beauty. The shells
are perforated by many small holes through which project
long, delicate, protoplasmic pseudopodia. These fine
pseudopodia often interlace and fuse when they touch each

BRANCH PROTOZOA: THE ONE-CELLED ANIMALS 81

other, thus forming a sort of protoplasmic network outside
of the shell. In some cases there is a complete layer of
protoplasm — part of the body protoplasm of the Protozoan
—surrounding the cell externally.

When these tiny animals die their hard shells sink to
the bottom of the ocean, and accumulate slowly, in in-
conceivable numbers, until they form a thick bed on the
ocean floor. Large areas of the bottom of the Atlantic

Fic. 11.— Rosalina varians, a marine protozoan (Foraminifera) with calca-
reous shell. (After Schultze.)

Ocean are covered with this slimy ooze, called Forami-
nifera ooze or Radiolaria ooze, depending on the kinds of
animals which have formed it. Nor is it only in present
times that there has been a forming of such beds by the
marine Protozoa. All over the world there are thick
rock strata composed almost exclusively of the fossil shells
of these simplest animals. The chalk-beds and cliffs of
England, and of France, Greece, Spain, and America,
were made by Foraminifera. Where now is land were
once oceans the bottoms of which have been gradually

82 ELEMENTARY ZOOLOGY

lifted above the water’s surface. Similarly the rock
called Tripoli found in Sicily and the Barbadoes earth
from the island of Barbadoes are composed of the shells
of ancient Radiolaria. 7 :

It is thus evident that the Protozoa is an ancient group
of animals. As a matter of fact zoologists are certain
that it is the most ancient of all animal groups. All of
the animals of the ocean depend upon the marine Protozoa
and the marine Protophyta, one-celled plants, for food.
Kither they feed on them directly, or prey omeanmmals
which in turn prey on these simplest organisms. A well-
known zoologist has said: ‘‘ The food-supply of marine
animals consists of a few species of microscopic organisms
which are inexhaustible and the only source of food for all
the inhabitants of the ocean. The supply is primeval as
well as inexhaustible, and all the life of the ocean has —
gradually taken shape in direct dependence on it.’’ The
marine Protozoa are the only animals which live in-
dependently; they alone can live or could have lived in
earlier ages without depending on other animals. They
must therefore be the oldest of marine animals. By
oldest is meant that their kind appeared earliest in the
history of the world, and as it is certain that ocean life is
older than terrestrial life—that is, that the first animals
lived in the ocean—it is obvious that the marine Protozoa
are the most ancient of all animal groups. -

As already learned in the examination of examples of
one-celled animals, it is evident that life may be success-
fully maintained without a complex body composed of
many organs performing their functions in a specialized
way. The marine Protozoa illustrate this fact admirably.
Despite their lack of special organs and their primi-
tive way of performing the life-processes, that they live -
successfully is shown by their existence in such extraor-
dinary numbers. They outnumber all other animals.

4

BRANCE PROTOZOA: THE ONéE-CELLED ANIMALS 83

The conditions of life in the surface-waters of the ocean
are easy and constant, and a simple structure and simple
method of performing the necessary life-processes are
wholly adequate for successful life under these con-

ditions.

CHAPTER~XVI

BRANCH PORIFERA: PHE Seo.

THE FRESH-WATER SPONGE (Spongilla sp.)

TECHNICAL NOTE.—Fresh-water sponges may perhaps not be
readily found in the neighborhood of the school, but they occur
over most of the United States, and careful searching will usually
result in the finding of specimens. They are compact, solid-looking
masses, sometimes lobed, resting on and attached to rocks, logs,
timbers, etc.; in clear water’ in creeks, ponds, or bayousset ney
are creamy, yellowish-brown or even greenish in color and resemble
some cushion-like plant far more than any of the familiar animal
forms. They can be distinguished from plants, however, by the
fact that there are no leaves in the mass, nor long thread-like fibres
such as compose the masses of pond alge (pond scum). When
touched with the fingers a gritty feeling is noticeable, due to the
presence of many small stiff spicules. Sponges should be removed
entire from the substance they are attached to, and may be taken
alive to the laboratory. They die soon, however, and should be put
into alcohol before decay begins.

Note the form: of the sponge mass. Js if lobed: or
branched ? E.xamine-the surface for openings; @inese
are of two sizes; the larger are osteoles or exhalant open-
mgs, While the smaller and more numerous are ores or
inhalant openings. The sponge-flesh is called sarcode.
Examine a bit of sarcode under the microscope; note the
Spicwies.-~ blave: these spicules a regular arrangement?
Of what are they composed ? :

Draw the entire sponge, showing shape and openings;
draw some of the spicules.

Embedded in the body-substance, especially near the
base, note (if present) numerous small, yellowish, sub-

84

BRANCH PORIFERA: THE SPONGES 85

spherical or disk-like bodies, the gemmules. These are
reproductive bodies. Each gemmule is a sort of internal
bud. It is composed of an interior group of protoplasmic
cells, enclosed by a crust thickly covered with spicules.
In winter the sponge dies down and the gemmules are set
free in the water. . In spring the protoplasmic contents
issue through an aperture in the crust, called the szcro-
pyle or foraminal opening, and develop and grow into a
new sponge.

For a good account of the fresh-water sponge, see

’

Pott’s ‘‘ Fresh-water Sponges. ’

A CALCAREOUS OCEAN-SPONGE (Grantia sp.) (fig, 7, D, E, -F.)

TECHNICAL NOTE.—For inland schools, specimens preserved in
alcohol or formalin must be used. They may be obtained from
dealers in naturalists’ supplies (see. p. 453). Specimens of some
species of this genus can be obtained at almost any point on the
Atlantic or Pacific coasts of this country.

Examine the external structure of a specimen. Note
the elongate, sub-cylindrical form, the attached base, the
free end. Note the large exhalant opening, osteole or
osculum, at the free end; the numerous small inhalant
openings elsewhere on the surface (best seen in dried
specimens). Note the spzcaules covering the surface of the
body, and the longer ones surrounding the osculum. Cut
the sponge in two longitudinally and note the simple cylin-
drical body-cavity, the gastric cavity or cloaca. Note the
thickness of the body-wall; note the tubes running through
the body-wall from cloaca to external surface. Through
these tubes water laden with food enters the gastric cavity,
where the food is digested, the water and undigested
particles passing out through the osculum. Crush a bit of
Cried sponge, or boil a bit of soft sponge in caustic potash
and mount on a glass slide. Examine under a micro-
scope and note the abundance of spicules and the variety
in their form. Two kinds may always be found, and

86 ELEMENTARY ZOOLOGY

sometimes three. These spicules are composed of car-
bonate of lime and can be dissolved by pouring on to
them a drop of hydrochloric acid. .

Some of the sponges may have buds growing out from
them near the base. These buds are young sponges
developed asexually. If allowed to develop fully the
buds would have detached themselves from the parent
and each would have become a new sponge.

Make drawings showing the form of a whole sponge;
the appearance of the inner face of the sponge bisected
longitudinally; the shape of the spicules.

A. COMMERCIAL SPONGE

TECHNICAL NOTE.—For the study of the skeleton of an ocean-
sponge with more complex body buy several common small bath-
sponges without large holes running entirely through them. The
teacher should have also a few specimens of small marine sponges
preserved in alcohol or formalin. Such specimens should be part
of the laboratory equipment (see account of laboratory equipment,
my. 450), and can be readily and cheaply obtained from dealers in
naturalists’ supplies.

The bath-sponge or slate-sponge consists simply of the
hard parts or skeleton of a sponge animal. In life all of
the skeleton is enclosed or covered by a soft, tough mass
composed of layers of cells. Note the many openings on
the surface of the sponge. Crush a bit of the skeleton
and examine it under the microscope. Note that it is
composed of fine fibres of a tough, horny substance called

spongin, instead of tiny distinct calcareous spicules.

7c

OTHER SPONGES

The sponges are fixed, plant-like aquatic animals.
The members of a single family live in fresh water, being
found in lakes, rivers, and canals in all parts of the world.
All the other sponges, and there are several thousand
species known, live in the ocean. They are to be found
at all depths, some in shallow water near the shore and

BRANCH PORIFERA: THE SPONGES 84

others in deeper water, even to the deepest depths yet
explored. They are found in all seas, though especially
abundantly in the Atlantic Ocean and Mediterranean Sea.

Form and size.—The shape of the simplest sponges is
that of a tiny vase or nearly cylindrical cup, hollow and
attached at its base. At the free end there is a large
opening. But there is a great deal of variety in the form
and size of different sponges.

There is, indeed, much varia- |B 3
tion in the shape and general |
character of different individuals
of the same species. Unlike
most other animals, sponges are
fixed, and the character of the
surface to which a sponge is
attached has much _ influence
upon its shape. If this surface
is rough and uneven the sponge
may follow in its growth the
sinuosities of the surface and so
become uneven and distorted
in shape. At best, only a few
kinds of sponges have any very
even and symmetrical shape.
Most of them are very unsym-
metrical and grow more like a
low compact bushy plant than
like the animals we are familiar
with. The smallest sponges
are only I mm. (54 in.) high,

while the largest may be over F'G. 12. — The skeleton of a
‘‘glass”’ sponge (skeleton com-

a meter (39 in.) in height. In posed of siliceous spicules) from
color living sponges may be Japan. (From specimen. )
red, purple, orange, gray, and sometimes blue. Most
sponges have the whole body of one color.

838 ELEMENTARY: ZOOLOGY

Skeleton.— A very few sponges have no skeleton at
all. The others have a skeleton or hard parts composed
of interwoven fibres of the tough, horny substance called
spongin, or of hosts of fine needles or spicules of silica or
of carbonate of lime. The siliceous skeletons of some
of the so-called glass-sponges (fig. 12) are very beautiful.
The lime and siliceous sponge spicules exhibit a great
variety of outline, some being anchor-shaped, some cross-
shaped, and some resembling tiny spears or javelins.

Structure of body.—The skeleton of a sponge whether
composed of interlacing fibres or of short spicules is
always invisible from the outside when the sponge is alive.
It is embedded in, or clothed by, the soft, fleshy part of
the body. The soft part of the sponge is composed
simply of two layers of cells, one constituting the external
surface of the body, and the other lining the interior
cavities and canals of the body. Between these two cell-
layers there is a mass of soft gelatinous substance all
through which protoplasm ramifies, and in which are em-
bedded numerous scattered cells. There are, as seen in
‘the case of Spongilla and Grantia, no systems of organs
such as characterize the higher animals. No heart, lungs,
alimentary canal, nervous system, organs of locomotion,
eyes, ears, or other organs of special sense; the sponge
has none of these. It is simply an aggregate of cells,
arranged in two layers, and supported usually by a skele-
ton of horny fibres or calcareous or siliceous spicules. Its
body is usually shapeless, unsymmetrical and without
front or back, right-or left. It 1s not te be wome@erediat
that sponges were for a long time believed to be plants.

Feeding habits.—The sponges feed on minute bits of
animal or plant substance and on the microscopic unicel-
lular plants or animals which float in the water which
bathes their bodies. The water entering the spenge-
body through the various openings of the surface is moved

BRANCH PORIFERA : THE SPONGES 89

along by the waving or lashing of the flagella of the cells
which line the canals, and these currents of water bear
with them the tiny organisms which are taken up by these
same cells and digested. [he incoming currents of water
meet in the central cavity or cavities of the body and pass
out through the large opening called the osculum at the
free end of the vase-like body, or if the body is branched,
through the large openings at the tips of these branches.

The same currents of water bring also oxygen for the
sponge’s breathing and carry away the carbonic acid gas
given out by the body-cells.

As a German naturalist has said, the one necessary
condition for the life of a sponge is the streaming of water
through its body. All sponges have a system of canals
for this water-current and all have means, in the waving
flagella or cilia with which these canals are lined, for pro-
ducing these currents. When a live sponge is put into a
vessel of water, currents are immediately set up, and they
always flow into the body through the many fine openings
and out of the body through the osculum.

Development and life-history.—Although the sponge
in its adult condition is permanently attached by its base
to the sea-bottom or to some rock or shell, when it is first
born it is an active free-swimming creature. The sponges
reproduce in two ways, asexually and sexually. The
asexual mode of reproduction of the fresh-water sponge
by gemmules has already been described. The ocean
sponges also reproduce asexually either by forming
interior gemmules or external buds. In this latter
method a bud forms on the outer surface of the body
which increases in size and finally grows into a new
sponge individual. In some species this new sponge does
' not become separated from the body of the mother,
but remains attached to it like a branch to a tree-trunk.
By the continued production of such non-separating indi-

go ELEMENTARY ZOOLOGY

viduals, a colony of sponges is formed which has the
general appearance of a branching plant. In other
species the new sponge formed by the development and
growth of a bud falls off and becomes a distinct separate
individual. |

In the sexual mode of reproduction, male or sperm- —
cells and female or egg-cells are developed in the same
individual. The sperm-cells are motile and swim about
in the cavities and canals of the sponge-body until they
find egg-cells, which they fertilize. The fertilized eggs
begin to develop and pass through their first stages in the
sponge-body. Finally the embryo sponge, which 1s
usually a tiny oval or egg-shaped mass of cells, escapes
from the body of the parent into the water. The young
sponge has some of its outer cells provided with cilia, —
and by means of these it swims about. After a while
it comes to rest on the ocean-floor or on some rock
or shell, attaches itself, and begins to take on the form
and character of the parent. It leads hereafter a fixed
sedentary life. |

The sponges of commerce.—The sponge-skeletons
which are the ‘‘sponges ’’ that we use all belong to a few
species, not more than half a dozen. Most of the com-
mercial sponges come from the Mediterranean Sea, though
some come from the Bahama Islands, some from the Red
Sea, and a few from the coasts of Greece, Asm Mier,
and Africa. The commercial sponges do not live in very
deep water; they are usually found not deeper than 200
feet... The living sponges. are collected By divers, or are
dragged up by men in boats using long-poled hooks, or
dredges. “‘‘ When secured they are exposed to the ‘air
for a limited time, either in. the boats or on shore, and
then thrown in heaps into the water again in pens or
tanks built for the purpose. Decay thus takes place with
great rapidity, and when fully decayed they are fished up

MeaNel? Tt ORIPERA: > Take SPONGES QI

again, and the animal matter beaten, squeezed, or washed
out, leaving the cleaned skeleton ready for the market.
In this condition after being dried and sorted, they are
sold to the dealers, who have them trimmed, re-sorted
and put up in bales or on strings ready for exportation.
There are many modifications of these processes in differ-
ent places, but in a general way these are the essentia-
steps through which the sponge passes before it is con-
sidered suitable for domestic purposes. Bleaching-
powders or acids are sometimes used to lighten the color,
but these unless very delicately handled injure the dura-
bility of the fibres.’’ |
Classification.— The sponges are classified according
to the character of the skeleton. In one group are put
all those sponges which have a skeleton of calcareous
spicules, and this group is called the Calcarea. All other
sponges are grouped as Non-Calcarea, the members of
this group either having no skeleton at all, or having a
skeleton composed of siliceous spicules or of spongin
fibres. According to the absence or presence of a skele-
ton and the character of the skeleton when it exists the
Non-Calcarea are subdivided into smaller groups.

CHAPTER XV#t

BRANCH COCELENTERATA: THE PORYVPox cH A
ANEMONES, CORALS,. AND Eien

The structure and life-history of an example of the
polyps (the Fresh-water ‘Hydra, fya@7¢ Speiias. been
studied in Chapters X and XI.

OTHER POLYPS, SEA-ANEMONES, CORA S nae
JELLYFISHES
TECHNICAL NOTE.—The teacher should have, if possible, several
pieces of coral and a few specimens of Ccelenterates in alcohol or
formalin, which will show the external character, at least, of these
animals (see account of laboratory equipment, p. 450). If the

school is on the coast, the pupils should be shown the sea-anemones
of the tide-pools.

The animals which are included in the branch Ceelen-
terata are, at least in living condition, unfamiliar to most
of us. Like the sponges, they are almost all inhabitants
of the ocean; a few, like A/ydra, live tm “tester:
Like the sponges, too, most of the members of this
branch are fixed, and in their general appearance suggest
a plant rather than an animal. The name zoophytes, or
plant-animals, which is often applied to these animals is
based on this superficial resemblance. But many of the
Coelenterates lead an active free-swimming life. This is
true of the jellyfishes which float or swim about on or near
the surface of the ocean. Many of the zoophyres —oend
part of their life in an active free-swimming condition
before settling down, becoming attached and thereafter

Q2

meme CORLENTERALA: THE POLYPS, ETC. 93

remaining fixed. In localities near the seashore many
animals belonging to this great group can be readily
found and observed. The beautiful sea-anemones with
their slowly-waving tentacles, the fine many-branched
truly plant-like hydroids with their hosts of little buds,
and the soft colorless masses of jelly, the jellyfishes, which
are cast up on to the beaches by the waves are all animals
belonging to the branch Ccelenterata.

General form and organization of body.—The general
or typical plan of body-structure for the Ccelenterata,
these animals which come next to the sponges in degree
of complexity, can best be understood by imagining the
typical cylindrical or vase-like body of the simple sponges
to be modified in the following way: The middle one of
the three layers of the body-wall not to be composed of
scattered cells in a gelatinous matrix, but to be simply a
thin non-cellular membrane; the body-wall not to be
pierced by fine openings or pores, but connected with the
outside only by the single large opening at the free end,
and this opening to be surrounded by a circlet of arm-like
processes or tentacles, which are continuations of the
body-wall and similarly composed. Such a body-struc-
ture, which we saw well shown by A/ydra, is the funda-
mental one for all polyps, sea-anemones, corals, and
jellyhshes. The variety in shape of the body and the
superficial modifications of this type-plan are many and
striking, but after all the type-plan is recognizable through-
out the whole of this great group of animals.

The two chief body-shapes represented in the branch
are those of the polyps on the one hand, and the Jjelly-
fishes or medusz on the other. The polyp-shape is that
of a tube with a basal end blind or closed, attached to
some firm object in the water and with the free end with
an opening, the mouth-opening. At this mouth-end
there is a circlet of movable, very contractile tentacles.

\

~~

04 ELEMENTARY ZOOLOGY

The mouth may open directly into the interior of the body,
which interior may be called the digestive cavity, or it
may lead into a simple short tube produced by the in-
vagination or bending in of the body-wall, which may be
looked on as the simplest kind of cesophagus. This
cesophageal tube opens into the body-cavity or digestive
cavity. This cavity may be incompletely divided by
longitudinal partitions which project from the sides into
the cavity.

The jellyfish or medusoid body-form corresponds in
general to an umbrella or bell. Around the edge of this
umbrella are disposed numerous threads or tentacles
(corresponding to the circlet of tentacles in the polyp).
The mouth-opening is at the end of a longer or shorter
projection which hangs down from the middle of the
under side of the umbrella. The interior body-cavity or
digestive cavity extends out into the umbrella-shaped
part of the body, usually in the condition of canals radiat-
ing from the centre and a connecting canal running
around the margin of the umbrella.

Structure.— Although the Ccelenterata show little in-
dication of the complex composition of the body out of
organs, as it exists among the higher animals, yet they
do show an unimstakable advance on the simple, almost
organless body of the sponges. This is chiefly shown by
the differentiation among the cells which compose the
body. In the polyps and jellyfishes some of the cells are
specialized to be unmistakable muscle-cells, some to be °
nerve-cells and fibres, and so on. A very simple nervous
_ system consisting of small groups of nerve-cells connected
by nerve-fibres exists. Some very simple special sense-
organs may occur. The digestive system, although in
the simpler Ccelenterates consisting merely of the cylin-
drical body-cavity enclosed by the hody-wall and opening
by the single hole at the free end of the body, in some is

pane COPEENTIERATA:. THE: POLYPS, ETC. 95

rather complex and is composed of different parts. Those
Ccelenterates which are not fixed but lead an active, free-
swimming life, viz., the jellyfishes or medusz, are the
most highly organized.

The tentacles which surround the mouth-opening and
serve to grasp food and carry it into the mouth, and the
stinging or lasso threads with which these tentacles are
provided are special organs possessed by most of these
animals.

Skeleton.—Like the sponges, some of the Coelenterata
possess a hard skeleton. This skeleton is always com-
posed of calcium carbonate and is called coral. Those
polyps which form such a skeleton are called the corals.
Coral will be described in connection with the account of
the coral-polyps.

Development and life-history.—The polyps and jelly-
fishes reproduce both asexually and sexually. The
asexual mode is usually that of budding. On a polypa
bud is formed by a hollow outgrowth of the body-wall.
The bud grows, an opening appears at its distal end, a
circlet of tentacles arises about this mouth-opening and a
new polyp individual is formed. This individual may
separate from the parent or it may remain attached to it.
By the development of numerous buds, and the remaining
attached of all of the individuals developing from these
buds, a colony of polyp individuals may be formed, plant-
like in appearance. The various polyp individuals of a
colony may differ somewhat among themselves, and these
differences are correlated with a division of labor. Thus
some of the individuals may devote themselves to getting
food for the colony, and these have mouth and tentacles.
Others may be devoted to the production of new indi-
_ viduals by budding or by producing germ-cells, and may
not have any mouth-opening or any food-grasping
tentacles.

96 ELEMENTARY ZOOLOGY

In case of many polyps all or some of the new indi-
- viduals which arise by budding do not become polyps, but
develop into medusz or jellyfish, which separate from the
fixed polyp and swim off through the water. These
meduse or Jellyfish produce sperm-cells and egg-cells.
The sperm-cells fertilize the egg-cells and a new indi-
vidual develops from each fertilized egg. This new indi-
vidual is at first an active free-swimming larva called a
planula, which does not resemble either a medusa or polyp.
After a while it settles down, becomes fixed and develops
into a polyp. Thus a polyp may produce a medusa or
jellyfish which, however, produces not a new jellyfish, but
a polyp. This is called an alternation of generations,
and is not an uncommon phenomenon among the lower
animals. It results from such an alternation of genera-
tions that a single species of animal may have two distinct
forms. This having two different forms is called dzmor-
phism. SDometimes, indeed, a species may appear in
more than two different forms; such a condition is called
polymorphism.

Not all medusz or jellyfish are produced by polyp indi-
viduals, nor do jellyfish always produce polyps and not
jellyfishes. There are some jellyfishes (we might call
them the true jellyfishes) which always have the jellyfish
form, producing new jellyfishes either by budding or by
eggs, and there are some polyps which always have the
true polyp form, producing new individuals, either by
budding or by eggs, always of polyp form and never of
jellyfish form... That-is, some species of s@e@leaterata
exist only in polyp form, some species exist only in jelly-
fish form, while some species (those having an alternation
of generations) exist in both polyp and Jellyfish form,
these two forms appearing as alternate generations.

Classification.—The branch Ccelenterata is divided
into four classes: (1) the Hydrozoa, including the fresh-

BRANCH -“CCELENTERATA {RHE POLYPS, ETC. 97

water polyps, numer-
ous marine polyps,
many small jellyfishes
and a few corals; (2)
the Scyphozoa, includ-
ing most of the large
jellyfishes ; (3) the Ac-
tinozoa, including the
Sea-anemones and
most of the stony
corals; (4 dine “Cte= 7
nophora, including
certain peculiar jelly-
fishes.

The polyps, colonial
jellyfishes, etc. (Hy-
drozoa).—To the class
Hydrozoa belongs the
Flydraalready studied.
There are a few other
fresh-water polyps and
they all belong to this
class. The most in-
teresting members of
the class are the ‘‘co-
lonial jellyfishes,’’
constituting the order
Siphonophora. These

a wo .

PMac. 13.—The Portuguese Man-of-War (Pysalia sp.). (From specimen
from Atlantic Coast. )

Cre aia ELEMENTARY ZOOLOGY

colonial jellyfishes are floating or swimming colonies of
polypeid and medusoid individuals in which there is a
marked division of labor among the individuals, ac-
companied by marked differences in structural charac-
ter. The individuals are accordingly polymorphic,
that is, appear in various forms, although all belong
to the same species. Because these various individuals -
forming a colony have given up very largely their
individuality, combining together and acting together like
the organs of a complex animal, they are usually not
called individuals, nor on the other hand organs, but
gZootds, or animal-like structures. The beautiful ‘‘ Portu-
guese man-of-war ’’ (fig. 13) is one of these colonial jelly-
fishes. It appears asa delicate bladder-like float, brilliant
blue or orange in color, usually about six inches long,
and bearing on its upper surface which projects above the
water a raised parti-colored crest, and on its under surface
a tangle of various appendages, thread-like with grape-
like clusters of little bell- or pear-shaped bodies. Each
of these parts is a peculiarly modified polyp- or medusa-
zooid produced by budding from an original central zooid.
The Portuguese man-of-war is very common in tropical
oceans, and sometimes vast numbers swimming together
make the surface of the ocean look like a splendid flower-
garden.

Usually the central zooid in a Siphonophore to which
the other zooids are attached is not a bladder-like float,
but is an upright tube of greater’ or less lemeth iy the
Siphonophore shown in figure 14, the compound body is
composed of a long central hollow stem with hundreds
or thousands of variously shaped parts, each of which 1s
reducible to either a polyp or medusazooid, attached
around it. The upper end is enlarged to form an air-
filled chamber, a sac-like boat, by means of which the
whole colony is kept afloat. Around the upper end of the

BrANGH CGELENTERAT A THE POLYPS, -ETC. 99

central stem are many medusoid structures, the swimming-
bells, by means of
whose opening and
closing the whole col-
ony is made to swim
through the water.
Each swimming - bell
is a modified medusa-
zooid, without tenta-
cles, without digestive
or reproductive or-
gans, but exercising
the power of swim-
ming by contracting
and forcing the water
out of the hollow bell
just as is done by
the free medusz. Be-
low the swimming-
bells, at the lower end
of the central. stem,
are grouped many
structures presenting
at first sight a confu-
sion of variety and
complexity, but on
careful examination
revealing themselves
to be polyp- and me-
dusa-zooids modified
to form at least five :
kinds of particularly “ive

: : 14.—A colonial jellyfish (Siphonophora),.
functioning struc: (After Haeckel) P phora)

tures. There are many flattened scale-like parts whose
function is simply that of affording a passive protection,

pe ok C.

TOU ELEMENTARY ZOOLOGY

in times of danger, to the other structures. These pro-
tecting-scales are greatly modified medusa-zooids, each
consisting of a simple cartilage-like gelatinous mass
penetrated by a food-carrying canal. Under the broad
leaves of these protecting-zooids are a number of pear-
shaped bodies which have a wide octagonal mouth-open-
ing at their free end, and possess in their interior certain
digestive glands. Each one is provided with a very long
flexible tentacle which bears many fine stinging-threads.
The tentacle waves back -and forth in the water, and
on coming in contact with an enemy or with prey its
poisonous stinging-threads shoot out and paralyze or
wound the unfortunate animal. These pear-shaped bodies
are the feeding structures, each being a modified polyp-
zooid. Scattered among these dangerous structures are
many somewhat similarly shaped but wholly harmless
structures, the sense-structures. Each of these has a
pear-shaped body but without mouth-opening, and also
a long, very sensitive, tentacie-like process. The sense
of feeling is highly developed in these tentacles, and they
discover for the colony the presence of any strange body.
These sense-structures are modified polyp-zooids. Finally
there are two other kinds of structures, usually arranged
in groups like bunches of grapes, which are the repro-
ductive structures, male and female. Ihey are modiied
medusa-zooids grown together and without tentacles.
This whole colony, or this compound animal, floats or
swims about at the surface of the ocean, and performs all
of the necessary functions of life as a single animal com-
posed of organs might. Yet the Siphonophore is more
truly to be regarded as a community in which the hundreds
os thausands of animals, representing five or six kinds of
individuals, all of one species, are fastened together. Each
individual performs the particular duties devolving upon
its kind or class. Thus there are food-gathering indi-

Peel then) fied ft? THE POLY FS, EFC. io

viduals, locomotor individuals, sense individuals, and
reproductive individuals. The modifications of the various
Kinds cf individuals are more extreme than in the case of
the various kinds of individuals composing a bee-com-
munity, for example, but the holding together or fusing
of all into one body or corporation is a condition which
makes this greater modification necessary and not un-
expected. And there is no difficulty in seeing that each
of these parts is really, structurally considered, a modified
polyp or medusa. :

The large jellyfishes, etc. (Scyphozoa).—To the class

Scyphozoa belong most of the common large jellyfishes.

Fic. 15.—A jellyfish or medusa, Gon onema vertens, eating two small
fishes. (From specimen trom Atlantic Coast.)

When one walks along the sea-beach soon after a storm
one may find many shapeless masses of a clear jelly-like

ro2 ELEMENTARY ZOOLOGY

substance scattered here and there on the sand. These
are the bodies or parts of bodies of jellyfishes which have
been cast up by the waves. Exposed to the sun and
wind the jelly-like mass soon dries or evaporates away to
a small shrivelled mass. The body-substance of a jelly-
fish contains a very large proportion of water; in fact
there is hardly more than 1 per cent of solid matter in it.

The jellyfishes occur in great numbers on the surface of
the ocean and are familiar to sailors under the name of
‘““sea-bulbs.’’ Some live in the deeper Mwaters. 2 teow
specimens have been dredged up from depths of a mile
below the surface. They range in size from ‘‘ umbrellas ’’
or disks.a few millimeters in diameter te. digs on a
diameter of two meters (24 yards). They are all car-
nivorous, preying on other small ocean animals which
they catch by means of their tentacles provided with
stinging-threads. ‘The tentacles of some of the largest
jellyfishes ‘‘ reach the astonishing length of 40 meters, or
about 130 feet.’’ Many of the jellyfishes are beautifully
colored, although all are nearly transparent. Almost all
of them are phosphorescent, and when irritated some
emit a very strong light.

The sea-anemones and corals (Actinozoa).—AImost
everywhere along the seashore where there are rocks and
tide-pools a host of various kinds of sea-anemones can be
found. When the tide is out, exposing the dripping sea-
weed-covered rocks, and the little sand- or stone-floored
basins are left filled with clear sea-water, the brown and
green and purple ‘‘sea-flowers ’’ may be found fixed to
the rocks by the base with the mouth-opening and circlet
of slowly-moving tentacles hungrily ready for food
(fig. 16). Touch the fringe of tentacles with your finger-
tip and feel how they cling toit and see how they close in
so as to carry what they feel into the mouth-opening.. A
host of individuals there are, and scores of different kinds;

BRANCH CUGLENTERATA: THE POLYPS, ETC. 103

some small, some large, some with the body covered out-
side with tiny bits of stone and shell so that they are_
hardly to be distinguished from the rock to which they

FiG. 16.—Sea anemones, Bunodes californica, open and closed individuals.
The closed individuals in upper right-hand corner show the external
covering of small bits of rock and shell, characteristic of most individu-
als of this species. (From living specimens in a tide-pool on the Bay
of Monterey, California.)

cling; some of bright and showy colors. These are the

most familiar members of the class Actinozoa.

But in other oceans, along the coasts of other lands,

especially those of the tropics and sub-tropics, there are

104 “ELEMENTARY ZOOLOGY

some other members of the class which are of urusual
interest. They. are the corals; oreeral ype gua aac
know these animals chiefly by their skeletons iGliege 7):
The specimens of corals which one sees in collections, or
made into ornaments, are the calcareous skeletons of
various kinds of the coral polyps. Some of the corals
live together in enormous numbers, ferming branching
colonies fixed as closely together as possible, and secrete
while living a stony skeleton of carbonate of lime. These
skeletons persist after the death of the animals, and
because of their abundance and close massing form great
reefs or banks and islands. These coral reefs and islands
occur only in the warmer oceans. In the Atlantic they
are found along the coasts of Southern Florida, Brazil
and the West Indies; in the Pacificcana Tudiam Oceans
there are great coral reefs on the coast of Australia,
Madagascar and elsewhere, and certain large groups of in-
habited islands like the Fiji, Society, and Friendly Islands
are exclusively of coral formation. Coral islands have a
great variety of form, although the elongated, circular,
ring-shaped and crescent forms predominate. How such
islands are first formed is described as follows by a well-
known student of corals: 3 :
‘(A growing coral plantation, with its multitudinous
life, oftentimes arises from great depths of the ocean, and
the sea-bed upon which it rests is probably a submarine
bank or mountain, upon which have lodged and slowly
aggregated the hard skeletons of pelagic forms of life.
When, through various sources of increase, this submarine
bank approaches the depth of from one hundred to one
hundred and fifty feet from the surface of the water, there
begins on its top a most wonderful vital activity. Jt is
then within the bathymetric zone of the reef-building
corals. Of the many groups of marine life which then
take possession of the bank, corals are not the only

Breve CCELENTERATA: -THE POLYPS, ETC. 105

animals, but they are the most important, as far as its
subsequent history goes. As the bank slowly rises by
their growth, it at last approaches the surface of the
water, and at low tide the tips of the growing branches
of coral are exposed to the air. This, however, only
takes place in sheltered localities, for long before it has
reached this elevation it has begun to be more or less

Fic. 17.—Skeleton of a branching coral, Madrepora cervicormis. (From
specimen. )

changed and broken by the force of the waves. As the
submarine bank approaches the tide level, the delicate
branching forms have to meet a terrific wave-action.
Fragments of the branching corals are’ broken off from
the bank by force of the waves, and falling down into the
midst of the growing coral below fill up the interstices,

106 ELEMENTARY ZOOLOGY

and thus render the whole mass more compact. At the
same time larger fragments are broken and rolled about
by the waves and are eventually washed up into banks
upon the coral plantation, so that the island now appears
slightly elevated above the tides. This may be called a
first stage in the development of a coral island. It is,
however, little more than a low ridge of worn fragments
of coral washed by the high tides and swept by the larger
waves—a low, narrow island resting on a large submarine

bank. ~

When the coral island rises thus a little above the sur-
face of the water, the waves break up some of the coral
into fine sand, which fills in the interstices, and offers a
sort of soil in which may germinate seeds brought in the
dried . mud om the feet of ocean bitds or carmed by the —
ocean currents. With the beginning of vegetable growth
the soil is more firmly held, is fertilized and ready for the
seeds of plants which need a better soil than lime sand.
Flying insects find their way to the island, especially if
it be near the mainland, birds begin to nest on it, and
soon it may be the seat of a luxuriant plant and animal
life.

For an account of coral islands see Darwin’s ‘‘ The
Structure and Distribution of Coral Reefs.’’

There are over 2000 kinds of coral polyp known, and
their skeletons vary much in appearance. Because of the
appearance of the skeleton certain corals have received
common names, as the organ-pipe coral, brain coral, etc.
The red coral, of which jewelry is made, grows chiefly in
the Mediterranean. It is gathered especially on the
western coast of Italy, and on the coasts of Sicily and
Sardinia. Most of this coral is sent to Naples, where it is
cut into ornaments.

There are other interesting members of the class
Actinozoa like the beautiful sea-pens, sea-feathers and

meee? COPLENTERATA: THE POLYPS, ETC. IO7

sea-fans, delicate, branching, tree-like forms found all
over the world. |

Ctenophora.—The members of this class are mostly
small, peculiar jellyfishes which do not form colonies, and
are extremely delicate, being usually perfectly trans-
pecee ihey swim by means of cilia. Phey. never
appear in a polyp condition, but are always medusoid in
shape. |

CHAPTER “XV

BRANCH ECHINODERMATA: STARFISHES,.
SEA-URCHINS, SEA-CUCUMBERS |

STARFISH (Asterias sp.)

TECHNICAL NOTE.—The species of Astertas are widely dis-
tributed on both coasts of the United States and may be procured
on almost any rocky shore at low tide. Teachers in inland schools
can obtain preserved material from the dealers mentioned on p.
453. Most of the specimens should be placed in alcohol or 4%
formalin. If fresh material.can be had itis well ta place gileast
one specimen for each student in a 20% solution of nitric acid in
water for two or three hours, when all of the calcareous parts will
have been dissolved, and after a thorough washing the specimen
will be ready for use.

External structure (figs. 18 and 19.)—In a fresh
specimen or one which has been preserved in alcohol or
formalin note the raying out of parts of the body from a
common centre. This is characteristic of the body or-
ganization of all Echinoderms, and is known as radial
symmetry. The lower surface of the body is called the
oral (because the mouth is on this surface), while the
upper is called the adoral surface. The central part of
the body is called the dsk. Note on the aboral surface ~
of the disk a small striated calcareous plate, the madre-
porite. or madreporic plate. In the middle (or very
nearly in the middle) of this surface of the disk there is
a small pore, the azal opening. The entire aboral sur-
face as well as a greater part of the oralside is: thickly
studded with the calcareous osszcles of the body-wall.
These ossicles support numerous short stout spzves ar-

ranged in irregular rows. Note that some of the ossicles
108

BRANCH ECHINODERMATA: STARFISHES, ETC. Tog

support certain very small pincer-like processes, the peaz-

cellarig. Inthe interspaces between the calcareous plates
are soft fringe-like projections of the inner body-lining, the

muscles of the pyloric caeca

pyloric stomach

’

reproductive gland s.-7&m

anus-" ff

pyloric caecum

' = poz
muscles of the pyloric caeca Se a
Fic. 18.—Dissection of a starfish (Asterias sp.).

respiratory ceca. Note at the tip of each arm or raya

cluster of smnall calcareous ossicles and within each cluster
a small speck of red pigment, the eye-spot or ocel/us.

IIo ELEMENTARY ZOOLOGY

_ Make a drawing of the aboral surface showing all these
parts.

On the oral surface note the centrally-located mouth,
the ambulacral grooves, one running longitudinally along
each ray, and in each groove two double rows of soft
tubular bodies with sucker-like tips. These are called
the f¢ube-feet and are organs of locomotion. Make a
drawing of the oral surface. |

Internal structure (figs. 18 and 19).—TECHNICAL NOTE.—
Take a specimen which has been immersed for some time in the nitric
acid solution, and with a strong pair of scissors, or better, bone-
cutters, cut away all the aboral wall of the disk except that immedi-
ately around the madreporite and the anus. Now begin at the tip
of each ray and cut away the aboral wall of each, leaving, however,
a single arm intact. When the roof of each arm has been carefully
dissected away the specimen should appear as in fig. 18.

Note the large alimentary canal, which is divided into
several regions. Note the short esophagus leading from
the mouth on the oral surface directly into a large mem-
branous pouch, the cardiac portion of the stomach. By
a short constriction the cardiac portion is separated from
the part which lies just above, i.e., the pylorze portion of
the stomach. From the pyloric portion large, pointed,
paired glandular appendages extend into each ray.
These are the pyloric ceca. Yheir function is digestive,
and oftentimes they are spoken of as the digestive glands

)

or, ‘livers. The pyloric czeca, as well as the cardiac
portion of the stomach, are held in place by paired muscles
which extend into each arm. Note two sets of these
muscles, one set for thrusting the cardiac portion of the
stomach out through the mouth and another for pulling it
back, the protractor muscles and retractor muscles,
respectively. The starfish obtains its food by enclosing
it in its everted stomach and then withdrawing stomach
and food into the body. Note that the pyloric portion of

the stomach opens above into a short zu¢estione terminating

BRANCH ECHINODERMATA > STARFISHES, ETC. TSE

in the azus, and observe that there is attached to the in-
testine a convoluted many-branched tube, the zztestinal
cecum.

Carefully remove a pair of pyloric ceca from one of the
rays and note the short duct which connects them with
the pyloric chamber of the stomach. Note in the angle
of each two adjoining rays paired glandular masses which
empty by a common duct on the aboral surface. These
glands are the reproductive organs. Note the small bulb-
like bladders extending in two double rows on the floor
of each ray. These are the water-sacs or ampulle, and
each one is connected directly with one of the locomotor
organs, the tube-feet.

Make a drawing of the organs in the dissection which
have so far been studied.

TECHNICAL NOTE.—For a careful study of the locomotor organs
a fresh starfish should be injected. This can usually be accom-
plished by cutting one ray off squarely, and inserting the needle of
a hypodermic syringe (which has been previously filled with a
watery solution of carmine or Berlin blue), into the end of the
radial water-tube which runs along the floor of the ray. By

injecting here, the whole system of vessels, tube-feet, and ampulle
are filled.

Note a ring-shaped canal which passes around the
alimentary canal near the mouth from which radial vessels
run out beneath the floor of each ray and from which a
hard tube extends to the madreporite. This hard tube is
the stone canal, so called because its walls contain a series
of calcareous rings, while the circular tube is the rig
canal or circum-oral water-ring from which radiate the
yadial canals. In some species of starfish there are
bladder-like reservoirs, Poltan vesicles, which extend
interradially from the ring canal.

Note that the ampulle and tube-feet are all connected
with the radial canals. By a contraction of the delicate

Sigh? ELEMENTARY ZOOLOGY

_ muscles in the walls of the ampulla the fluid in the cavity
is compressed, thereby forcing the tube-feet out. By the
contraction of muscles in the tube-feet they are again
shortened while the small disk-like terminal sucker clings
to some firm object. In this way~the animal pulls itself

calcareous spine respiratory caeca
“
epithelium of the body
cavity~--- 2.
mesentery--- 7x ae

jambulacral ossicle lla
---ampu

ectodermal covering-

pedicellaria- dar /
-radial “canal ff

radial blood-vessel

Fic. I9.—Semi-diagrammatic figure of cross-section of the ray of a starfish,
Asterias sp.

J

along by successive ‘‘steps.’’ This entire system, called
the water-vascular system, is characteristic of the branch
Echinodermata. In addition to the fluid in the water-
vascular system there is yet another body-fluid, the fevz-
visceral fluid, which bathes all of the tissues and fills the
body-cavity. 3

TECHNICAL NOTE.—Take a drop of the perivisceral fluid from a

living starfish and examine under high power of microscope, noting
the amoeboid cells it contains.

The perivisceral fluid is aerated through outpocketings
ot the thin body-wall which extend outward between the
calcareous plates of the body. These outpocketings have

BRANCH ECHiNODERMATA: STARFISHES, ETC. 112

already been mentioned as the respiratory ceca (see
p. 109). Surrounding the stone canal is a thin mem-
branous tube, and within it and by the side of the stone
canal is a soft tubular sac. The function of these organs
is not certainly known.

Work out the nervous system, note, as its principal
parts, a nerve-ring about the mouth, and nerves running
from this ring beneath the radial canals along each arm.

Life-history and habits.—The starfishes are all marine
forms. They hatch from eggs, and in their early stages
are very different in appearance from the adults. At first
they are bilaterally symmetrical, their radial symmetry
being acquired later. Thousands of eggs and sperm-cells
are extruded into the sea-water, where fertilization and
development take place. The young swim freely in the
open sea, feeding on microscopic organisms, and then
undergo very radical changes in the course of their
development. The adults are for the most part carniv-
Prous, ieeamne on crabs, snails; and the like.~ The live
prey is surrounded by the extruded stomach which secretes
fluids that kill it, after which the soft parts are digested.
(See general account of the life-history of Echinoderms

OM. p. PkO..) -

THE SEA-URCHIN (Strongylocentrotus sp.)

External structure.—TercunicaL Note.—lIf fresh or alco-
holic specimens or even the dry “tests” of the sea-urchin (fig. 20)
are to be had, the general characteristics of the external structure
can be made out. |

How does the external surface of the sea-urchin differ
from that of the starfish? Can you find the very long
tube-feet ? \Nhere is the mouth-opening ? With what is
it surrounded ? Each tooth is enclosed in a calcareous
framework. The whole structure is known as ‘‘Avrzstotle’s
lantern.’’ |

T14 ELEMENTARY ZOOLG@GY

TECHNICAL Note.—Remove the spines from the underlying
shell or test (fig. 21) and wash the test until perfectly clean, or place
in a solution of lye for a short time and then wash.

Note the characteristic radial symmetry of the se// or
test: Note on the aboral’ aspect, diversine aimee rac
medial anal aperture, five double rows of pores. What
are these for? Each of the five divisions set with pores

Fic, 20,—A sea-urchin, Strongylocentrotus franciscanus. (From specimen
from Bay of Monterey, Calif.) .

is called an amdbulacral area, while the intervening seg-
ments which ‘support the long spines. are called™ the
interambulacral areas. Note on the aboral] surface, sur-
rounding the. median-placed anal aperture, a series of
small plates. Those which are located in the interambu-
lacral areas are the genital plates. Through these plates
the ducts from the reproductive organs open by small
pores. Note a very much enlarged plate with a striated
appearance. This is the madreporite, which, as in the
starfish, is the external opening of the stone canal and
water-vascular system. Note the small ocular plate at
the tip of each ambulacral area. The ocular plates con-

BRANCH ECHINODERMATA: STARFISHES, ETC. 15

tain small pigment-cells and communicate with the
nervous system.

From a general inspection of the sea-urchin’s shell the
Echinoderm characteristics, namely, radial symmetry and
the presence of the water-vascular system, are readily
seen. While at first glance there is apparent little
similarity between the starfish and sea-urchin, neverthe-
less careful examination shows that the two animals-are

Fic. 21.—‘‘ Test” of sea-urchin, Strongylocentrotus franciscanus, with
spines removed. (From specimen.)

alike in their fundamental structure. Both are radially
symmetrical. The position of the anal opening makes
both starfish and sea-urchin slightly asymmetrical. In
both the madreporite and anus are on the aboral side,
while the mouth is centrally located on the oral side.
In the starfish we noted five ambulacral areas, one on the
under side of each arm; similarly we find five in the sea-
urchin. In both cases also we find the ocular spots at
the tips of the ambulacral areas. The genital apertures
are situated interradially in the starfish. In the sea-
urchin they are similarly placed. The dissimilarity
between the two forms is largely due to the very much
developed outer spines and the dorso-ventral thickening
of the disk in the sea-urchin. ‘The starfish is carnivorous,
while the sea-urchin lives on vegetable matter consisting

116 ELEMENTARY ZOOLOGY

for the most part of green algz and the red sea-weeds.
Correlated with this difference in food-habits there are
certain differences in the structure of the internal organs.
For example, the alimentary canal in the sea-urchin winds
in about two and one-half turns within the body-cavity
before it reaches the anus.

OTHER STARFISHES, SEA-URCHINS, SEA-CUCUM Eis.
EDC:

Without exception all the Echinoderms, under which
term are included the starfishes, sea-urchins, brittle-stars,
feather-stars, and sea-cucumbers, live in the ocean. Some
of them, the starfishes and sea-urchins, are among the
most common and familiar animals of the seashore. Most
of them are not fixed, but can move about freely, though
slowly. Some of the feather-stars are Hxed; as thie
sponges and polyps are.

Shape and organization of body.—The body-shape of
the Echinoderm varies from the flat, rayed bodiof the
starfish to the thick, flattened egg-shape of the sea-urchin,
the melon-like sac of the sea-cucumber and the delicate
many-branched head of the sea-lily sometimes borne on
a slender stalk. But in all these shapes can be seen more
or less plainly a symmetrical, radiate arrangement of the
parts of the body. The Echinoderm body has a central
portion from which radiate separate arm or branch-like
parts, as in the starfishes and sea-lilies, or about which
are arranged radiately the internal body-parts, although
the external appearance may at first sight give no plain
indication of the radiate arrangement. This is the case
with the sea-urchins and sea-cucumbers, yet, as has been
seen in the sea-urchin, the radiate arrangement can be
readily perceived by closer examination of the surface of
the egg- or sac-like body. The radiating parts of the

BRANCH ECHINODERMATA : STARFISHES, ETC. tS Bei

body are usually five. In the body of an Echinoderm
can be usually recognized an upper or dorsal surface and
a lower or ventral surface. “The mouth is usually situated
on the ventral side and the anal opening on the dorsal.
Echinoderms agree also in having a calcareous outer
skeleton or body-wall usually in the condition of definitely-
shaped plates or spicules fitted either movably or rigidly
together. This outer body-wall or exoskeleton may bear
many tubercles or spines. These spines are sometimes
movable. The body-wall of the sea-urchin shows very
well the exoskeleton composed of plates on which are
borne movable strong spines.

Structure and organs.—As has been learned from the
dissection of the starfish, the Echinoderms have well-
developed systems of organs. The body-structure in its
complex organization presents a marked advance beyond
the structural condition of the polyps and jellyfishes.
There is a well-organized digestive system with mouth,
alimentary canal, and anal opening. The alimentary
canal is either a simple spiral or coiled tube, or it is a tube
in which can be recognized different parts, namely,
cesophagus, stomach, intestine, ceca, and special glands
secreting digestive fluids. This alimentary canal is not,
as in the polyps, simply the body-cavity, but it is an in-
closed tubular cavity lying within the general body-cavity.
At the mouth-opening there is in some Echinoderms,
notably the sea-urchins, a strong masticating apparatus
consisting of five pointed teeth which are arranged in a
circle about the opening. The nervous system consists
of a central ring around the cesophagus or mouth, from
which branches extend into the radiately arranged arms
er sesions of the body. Fherée is no brain as. tm the
higher animals, but the central nerve-ring is composed of
both nerve-cells and nerve-fibres as in the nerve-centres
of higher forms. Of organs of special sense there are

118 ELEMENTARY -2ZGOLOGY

special tactile or touch organs in all the Echinoderms,
and the starfishes have very simply composed eyes or
eye-like organs at the tips of the rays.

While some of the Echinoderms breathe simply through
the outer body-wall, taking up by osmosis the air mixed
with the water, some of them have special, though very
simple, gill-like respiratory organs. ‘These organs con-
sist of small membranous sacs which are either pushed
eut from the body into the water, or lie in=cawigies mathe
body to which the water has access. There is also a dis-
tinct circulatory system, but the ““bloed). iene is
carried by these organs and which fills the body-cavity
consists mainly of sea-water, although containing a
number of amoeboid corpuscles containing a brown pig-
ment. There 1s no organ really correspondiaa= a6. tac
“heart .of the higher animals.. There are *distmen encans
for the production of the germ or reproductive cells. The
sexes are distinct (except in a few species), each individual
producing only sperm-cells or egg-cells, but the organs
or glands which produce the germ-cells are very much
alike in both. sexes«x, There is no apparent ditewence
between male and female Echinoderms except in the
character or rather in the product of the germ-cell pro-
ducing organs. ~/\. few. species are. exceptions, ceneain
starfishes showing a difference in color between males and
females. j

As all of the Echinoderms except some of the feather-
stars can move about, they have organs of locomotion,
and well-defined muscles for the movement of the loco-
motory organs. The external organs of locomotion, the
tube-feet (in the sea-urchins the dermal spines aid also in
locomotion), are parts of a peculiar system of organs
characteristic of the Echinoderms, called the ambulacral
or the water-vascular system. This system is composed
of a series of radial tubular vessels which rise from a cen-

BRANCH ECHINODERMATA: STARFISHES, ETC. 119

tral circular or ring vessel and which give off branches to
each of the tube-feet. The water from the outside enters
the ambulacral system through a special opening, the
madreporic opening, and flowing to the tube-feet helps
extend them. The tube-feet usually have a tiny sucking
disk at the tip, and by means of them the [Echinoderm
can cling very firmly to rocks.

Development and life-history.— Differing from the
sponges and the polyps and Jeilyfishes, the reproduction
of the Echinoderms is always sexual; young or new indi-
viduals are never produced by budding, or in any other
asexual way. The new individual is always developed
from an egg produced by a female and fertilized by the
sperm of amale. The eggs are usually red or yellow,
are very small (about J, in. in diameter in certain
starfishes), and are fertilized by the sperm-cells of the
males after leaving the body of the female. That is, both
sperm-cells and unfertilized egg-cells are poured out into
the water by the adults, and the motile sperm-cells in
some way find and fertilize the egg-cells.

From the egg there hatches a tiny larva which does
not at all resemble the parent starfish or sea-urchin. It
is an active free-swimming creature, more or less ellip-
soidal in shape and provided with cilia for swimming.
Soon its body changes form and assumes a very curious
shape with prominent projections. The larve of the
various kinds of Echinoderms, as the starfishes, sea-
urchins, sea-cucumbers, etc., are of different characteristic
shapes. The naturalists who first discovered these odd
little animals did not associate them in their minds with
the very differently shaped starfishes and sea-urchins, but
believed them new kinds of fully developed marine
animals, and gave them names. Thus the larve of the
starfishes were called Bipinnaria, the larve of the sea-
urchins Pluteus, and so on. These names are still used

120 ELEMENTARY ZOOLOGY

to designate the larve, but with the knowledge that
Bipinnaria are simply young starfishes, and that a Pluteus
is simply a young sea-urchin. From these larval stages
the adult or fully developed starfish or sea-urchin develops
by very great changes or metamorphoses. The Echino-
derms have in their life-history a metamorphosis as strik-
ing as the butterflies and moths, which are crawling
worm-like caterpillars in their young or larval condition.

Most of the Echinoderms have the power of regenerat-
ing lost parts. That is, if a starfish loses an arm (ray)
through accident, a new ray will grow out to replace the
old. And this power of regeneration extends so far in
the case of some starfishes that if very badly mutilated
they can practically regenerate the whole body. This
amounts to a kind of asexual reproduction. Some
species, too, have the peculiar habit of self-mutilation.
‘Many brittle stars and some starfishes when removed
from the water, or when molested in any way, break off
portions of thetr arms piece by piece, until, it may be,
the whole of them are thrown off to the very bases,
leaving the central disc entirely bereft of arms. A centrai
disc thus partly or completely deprived of its arms is
capable in many cases of developing a new set; and a
separated arm is capable in many cases of developing a
new disc and a completed series of arms.’’ In some of
the sea-cucumbers ‘‘it is the internal organs, or rather
portions of them, that are capable of being thrown off and
replaced, the cesophagus . . . or the entire alimentary
canal, being ejected from the body by strong contrac-
tions of the muscular fibres of the body-wall, and in
some cases, at least, afterwards becoming completely
renewed. ’’ |

Classification.— The Echinodermata are divided into
five classes, viz., the Asteroidea or starfishes, ‘‘free
Echinoderms with star-shaped or pentagonal body, in

BRANCH ECHINODERMATA: STARFISHES, ETC. 121

which a central disc and usually five arms are more or
less readily distinguishable, the arms being hollow and
each containing a prolongation of the body-cavity and
contained organs’’; the Ophiuroidea, or brittle-stars,
‘‘star-shaped free Echinoderms, with a central disc and
five arms, which are more sharply marked off from the
disc than in the Asteroidea and which contain no spacious
-prolongations of the body-cavity’'; the Echinoidea, or
sea-urchins, ‘‘ free Echinoderms with globular, heart-
shaped, or disc-shaped body enclosed in a shell or corona
of close-fitting, firmly united calcareous plates’’; the
Holothuroidea, or sea-cucumbers, ‘‘ free Echinoderms
with elongated cylindrical or five-sided body, ... witha
circlet of large oral tentacles’’; and the Crinoidea, or
feather-stars, ‘‘ temporarily or permanently stalked Echi-
noderms with star-shaped body, consisting of a central disc,
and a series of five bifurcate or more completely branched
arms, bordered with pinnules.’’

Starfishes (Asteroidea).—The starfishes feed on other
marine animals, especially shell-fish and crabs. They
are also reputed to destroy young fish. By means of their
sucking-tubes, or tube-feet with sucker tips, they can
seize and hold their prey firmly. They do much injury
to oyster-beds by attacking and devouring the oysters.
When attacking prey too large to be taken into the mouth
the starfish everts its stomach over the prey and devours
it. The stomach is afterward drawn back into the body-
cavity by special muscles.

_Starfishes vary much in size, color and general appear-
ance, although all are readily recognizable as starfishes
(fig. 22). The number of arms or rays varies from five
to thirty or more in different species; some have the
interradial spaces filled out nearly to the tips of the rays,
making the animal simply a pentagonal disc. In size
starfishes vary from a fraction of an inch in diameter to

122 ELEMENTARY ZOOLOGY

three feet; in color they are yellow or red or brown or

- purple.

Brittle-stars (Ophiuroidea).—The brittle-stars, or ser-

i
AG o-

6, PRBEB IAB
£ OF ayy Me

Fic. 22.—A group of Echinoderms: the
upper one, a starfish, Asterina mineata,
the one at the right a starfish, Asterias
ocracia, at the left a brittlestar, spe-
cies unknown, and at bottom two sea-
urchins, Stvongylocentrotus franciscanus.
(From living specimens in a tide-pool on
the Bay of Monterey, California. )

pent-stars (fig. 22) as
they. are salsomeallied.
resemble the starfishes
in external appearance,
that is, they are flat and
composed of a central
disc with radiating arms.
(always five in number,
although ~~ eaeh== arm
may be several times

branched). The central

disc is always sharply distinguished from the arms, and
the arms are usually slender and more or less cylin-

BRANCH ECHINODERMATA: STARFISHES, ETC. 234

drical. Thedistinguishing difference between the brittle-
stars and the starfishes is that the body-cavity and the
stomach which extend out into the arms in the star-
fishes are in the brittle-stars limited to the central disc, or
fem aise-atid bases of the arms. The tube-feet also
Mave fo suckers at the tips. -More than 700 species of
brittle-stars are known. They feed on marine shell-fish,
crabs and worms. |

Sea-urchins (Echinoidea).—Thesea-urchins (figs. 20, 21
and 22) of which more than 300 species are known, have
no arms or rays, and they are usually not flat like the star-
fishes but globular, with poles more or less flattened. As
has been noted in the examination of the body-wall or
‘«shell,’’ the radiate character of the body is shown by the
five radiating zones of tube-feet. The mouth, with its five
Smon2 «weet, - 1s on: the ventral surface, and the anal
opening and madreporic opening are on the dorsal sur-
face. The calcareous plates (seen distinctly in a specimen
from which the spines have been removed) which consti-
tute the firm part of the body-wall, are more or less
pentagonal in shape and are usually firmly united at the
eqges:) the spines which aré so- characteristic of the
sea-urchins vary much in size and number and firmness,
Buteare present in.some:form on all of them.

While most of the sea-urchins live near the shore,
being very common in tide-pools, some live only on the
bottom of the ocean at great depths. Their food consists
of small marine animals and of bits of organic matter
which they collect from the sand and débris of the ocean
floor. Many of the sea-urchins are gregarious, living
fometner i Creat numbers. Some have the habit of
boring into the rocks of the shore between tide-lines. I
have seen thousands of small beautifully colored purple
sea-urchins lying each in a spherical pit or hole in hard
conglomerate rock on the California coast. How they

124 ELEMENTARY ZOOLOGY

are enabled to bore these holes is not yet known.
There is great variety in size and color among the sea-
urchins. The colors are brown, olive, purple red, greenish
blue,, etc.

A few kinds of sea-urchins have a flexible shell or test.
The Challenger expedition dredged up from sea-bottom
some sea-urchins, and when placed on the ship’s deck
‘‘the test moved and shrank from touch when handled,
and felt like a starfish.’’ The cake-urchins or sand-
dollars are sea-urchins having a very flat body with short
spines. They lie buried in the sand, and are often very
brightly colored. Their hollow bleached tests with the
spines all rubbed off are common on the sands of both
the Atlantic and Pacific coasts.

Sea-cucumbers (Holothuroidea).—The sea-cucumbers
(ig. 23) show at first glance little resemblance to the
other radiate animals. The body is an elongate, sub-
cylindrical sac, resembling a thick worm or sausage or
cucumber..in shape. .At one end it bears a Graup. of
branched tentacles which are set in a ring around the
mouth-opening. The body-wall is muscular and leathery,
but contains many small separated calcareous spicules.
There are usually five longitudinal rows of tube-feet. In
some species, however, tube feet are wholly wanting; in
others they are scattered over the surface.

Although there are known about five hundred species
of sea-cucumbers many of which live along the shores,
they are much less familiar to us than the starfishes and
sea-urchins. ‘Lhey usually rest buried in the sand by day,
feeding-at night.. Some of. them attain a large size. A
great orange-red species of the genus Cucumarza, Which
is found in the Bay of Monterey, California, is three feet
long.

The people of some nations use sea-cucumbers as food.
They are called ‘‘trepang’’ in the orient. Phe Gade of

BRANCH ECHINODERMATA: STARFISHES, ETC. 125

preparing the trepang is almost entirely in the hands of |
the Malays, and every year large fleets set sail from

Fic. 23.—A sea-cucumber, Pentacta frondosa. (After Emerton.)

Macassar and the Philippines to the south seas to catch
sea-cucumbers.

Feather-stars (Crinoidea).—The feather-stars or sea-
lilies or crinoids (fig. 24), as they are variously called, differ
from the other Echinoderms in having the mouth on the
upper side of the central disc, and in the fact that all of
the species are fixed, either permanently or for a part of
their life, being attached to rocks on the sea-bottom by
a longer or shorter stalk which is composed of a series of
iimes or Sseoments. Phe central.disc is small and the

126 ELEMENTARY ZOOLOGY

radiating arms are long, slender, sometimes repeatedly
branched, and all the branches bear fine lateral projec-
tions called pinnule. Most of the feather-stars live in
deep water and are thus only seen after being dredged

up. They: feed on small crab-lke animals ane en the
marine unicellular animals and plants.

eS
>

geet

es.

Bes DEPRESSOR Ss as

re

2

Fic, 24. — A crinoid or feather-star, Pentacrinus sp. (After Brehm.)

CHAPTER XIX
Bieewel VEKMES:* THE: WORMS

THE EARTHWORM (Luméricus sp.).

TECHNICAL NOTE.—ObDtain live earthworms of large size, killing
some in 30% alcohol and hardening and preserving them in 80% alco-
hol, and bringing others alive to the laboratory. The worms may
be found during the daytime by digging, or at night by searching
with a lantern. They often come above ground in the daytime
after a heavy rain.- Live specimens may be kept in the laboratory
in flower-pots filled with soil. ‘They may be fed on bits of raw
meat, preferably fat, bits of onion, celery, cabbage, etc., thrown on
the soil.”

External structure (fig. 25).—Examine the external
structure of liveanddead specimens. Which is the ventral
and which the dorsal surface ? Which the anterior and
which the posterior end? Note the segmented condition
of the body; the number of segments or somites, and their
relative size and shape. Note absence of appendages such
as limbs and the presence of /ocomotor sete (short bristles).
How many sete are there on each segment and what is
their disposition? The mouth is covered by a dorsal
projection called the prostomium. The anal opening is
situated in the posterior segment of the body. The broad
thickened ring or girdle including several segments near

* The author recognizes the untenability of the group Vermes as a group
co-ordinate with the other branches of the animal kingdom, and that
‘¢Vermes”’ has been discarded in modern text-books. But because of the
very scant consideration which can be given the various kinds of worm.like
animals the course of the older text-books will be followed. and all of the
worm-like animals, as far as referred to in this book, be considered under
the group name Vermes.

127

128 BLEMENTARKY ZOCLOGa

cerebral ganglion

. pharynz

gesophagus
retractor and protractor

muscles of the pharynx _-

. esophageal pouches.-
reproductive organs ==

reproductive organs 2---

~e.

anus .

CHOPS ss

nephridium--

gizzard--

entestine --

Fic. 25.—Dissection of the earthworm, Lumbrocus sp.

BRANCH VERMES: THE WORMS 129

the anterior end of the body is the clztel/um, a glandular
structure which secretes the cases in which the eggs are
laid. On the ventral surface. of the fourteenth and
fifteenth segments (in most species) are two pairs of small
pores; two other pairs of small openings (usually difficult
to find), one between segments 9 and 10, and one between
ements 80 and 11, are present... All these are the.
external openings of the reproductive organs.

Make drawings showing the external structure of the
earthworm.

Examine a live specimen placed on moist paper or
wood. Note the characteristics of its locomotion, and
the movements of its body-parts. How do the sete aid
in locomotion ?

Internal structure (figs. 25, 26 and 28).—TECHNICAL
NOTE.—With a fine-pointed pair of scissors make a dorsal median
incision, not too deep, behind the clitellum and cut forward as far
as the first segment. Put the specimen into dissecting-dish, care-
fully pin back the edges of the cut and cover with clear water or,
better, 50% alcohol.

Note the long body-cavity divided by the thin septa
which have been torn away for the most part by the
pinning process. Note the thin transparent covering of
the body, the cauzzcle. Just beneath this note a less trans-
parent layer, the efzdermis, and underneath this a layer
of muscles. The muscular layer is made up of two
clearly recognizable sets, an outer circular layer and an
inner longitudinal layer the fibres of which are continuous
with the septa.

Note, as the most conspicuous internal organ, the long
alimentary canal, of which a number of distinct parts may
be recognized. Most anteriorly is a muscular pharynx,
which is followed by a narrow wsophagus, leading directly
into the thin-walled crop; next comes the muscular

130 ELEMENTARY ZOOLOGY

— gizzard, and next the zzzestzne which opens externally in
the terminal segment through the azws. The anterior end
of the alimentary canal is more or less protrusible, while
the posterior portion is held more firmly in place by the
septa which act as mesenteries. Surrounding the narrow
cesophagus are the reproductive organs, three pairs of
large white bodies and two pairs of smaller sacs.

Note the dorsal blood-vessel lying along the dorsal
surface of the alimentary canal, from the anterior por-
tion of which arise several cercumasophageal rings or
‘hearts.’’ - These ‘hearts’ are contractile amen s-n1e 10
keep the blood in motion through the blood-vessels (see
later). In the most anterior of the body segments note
the pear-shaped drazz or cerebral ganglion.

TECHNICAL NOTE.—Lift carefuily to right and ieft the repro-
ductive organs, thus exposing the cesophagus.

Note three pairs of bag-like structures projecting from
the cesophagus. The front pair is the wsophageal pouches ;
the .next two pairs are the wsophageal or eaiejc7ous
glands. Yhey communicate with the alimentary canal,
and their secretion is a milky calcareous fluid. ;

Make a drawing that will show all the parts so far
studied. |

TECHNICAL NOTE.—Cut transversely through the alimentary
canal in the region of the clitellum and carefully dissect the anterior
portion of the canal away from the surrounding organs.

Note the dorsal fold of the intestine, typhlosole, ex-
tending into the lumen. This fold gives a greater surface
for digestion, and in it are a great many “epatic or special
digestive cells. ‘The entire alimentary canal is lined with
epithelium. Observe just beneath the alimentary canal
the ventral blood-vessel, and still beneath this blood-
vessel the ventral nerve-cord. There is a slight swelling
on the nerve-cord in each segment of the body. These

BRANCH VERMES: THE WORMS i3t

swellings are the gazglia. How many pairs of nerves
are given off from each ganglion ? Observe in each seg-
ment, posterior to the first three or four, the successive

_dorsal blood vessel

Pp
ze
en ts

nephridia

OOOO Do one a eRe

nephrostome / ‘ventral blood vessel

ventral nerve cofd
Fic. 26.—Dissection to show alimentary canal in section and nephridia
of earthworm.

pairs of convoluted tubes, the xephrzdza, or organs of
excretion. Each nephridium opens internally through a
ciliated funnel, the zephrostome, within the body-cavity,
while it opens externally by a small excretory pore
between the setz on the ventral surface of the segment
behind that in which the nephridium chiefly lies. The
function of the nephridia is to carry off waste matter
from the fluid which fills the body-cavity.

Trace the ventral nerve-cord forward to its connection
with the cerebral ganglion. Note the throat nerve-ring
or cercumesophageal collar connecting the ventral cord
with the brain.

Make a drawing of the nervous system showing its
relation to other organs.

Life-history and habits.— The earthworm lives in soft
moist soil which is rich in organic matter. Its food is

132 ELEMENTARY ZOOLOGY

taken into the mouth mixed with dirt and sand. As this
mixture passes through the long alimentary canal the
organic particles are taken up and digested. As we have
already seen, there are in each worm two sets of reproduc-
tive glands, namely, male “and temale “arama oc
earthworm produces both egg-cells and sperm-cells, but

nephridium dorsal blood vessel
hepatic cells : Le
‘ ‘ | longitudinal muscle
\ wi circular muscle fibres
: ———— / epidermis
= cuticle

\
1 \

\
‘
1
\
iY
‘

iyphlosole

s=7SelQe

\ nerve cord =

/
e te }
nephridipore | nephrostome

x z
ventral vessel

body cavity

Fic. 28.—Cross-section of earthworm.

the sperm-cells of one worm are not used to fertilize the
eggs of the individual producing them. When the eggs
are ready to be discharged from the body, the clitellum:
becomes very much swollen and its glands begin an active
secretion which hardens and forms a collar-like structure
about the body of the worm. As this collar moves
forward toward the anterior end of the body it collects the
eggs and also the sperm-cells previously received from

BRANCH VERMES: THE WORMS 035

another worm, and finally slips off the head end of the
animal. The entire structure with the contained eggs
and sperm-cells as it passes off from the body becomes
closed at both ends, thus forming a horny capsule which
lies in the earth until the young worms emerge. Onlya
part of the eggs develop in each capsule, the rest being
used as food for the growing young. The young earth-
worms, though of very small size, are fully formed before
they leave the egg-capsule. Earthworms are more or less
gregarious, large numbers often being found together.

For an interesting account of the habits of earthworms
sce Warwin s ‘‘ The Formation of Vegetable Mold.”’

OTHER:- WORMS:

The branch Vermes comprises so large a number of
‘kinds of animals presenting such great differences in struc-
ture and habit that it is impossible to give a brief state-
Mea eencral or summary terms of their, external
body-characters, of the structural and functional condition
of their various organs and systems of organs, and of the
course of their development and life-history as has been
domesior the preceding’ -branches, Many zoolosists,
indeed, do not include all the worms or worm-like animals
in one branch, but consider them to form several distinct
branches.

inmecitam very @eneral characters all of the animals
minienecompose the branch Vermes do agree. All, or
nearly all, have an elongate body which is bilaterally
symmetrical, that 1s, which could be cut by a median
longitudinal cutting in two similar halves. In most of
them also the body is composed of a number of successive
segments or somites which are more or less alike. . This
kind of segmented or articulated body is also possessed by

134 ELEMENTARY ZOOLOGY

the insects and crabs. Almost all of the worms have the

power of locomotion; usually that of crawling. For
_ this crawling they do not have legs composed of separate
segments or joints as do the higher articulated animals,

Fic. 29.—-A group of marine worms; at the left a gephyrean, Dendrostomum
cromphelmt, the upper right-hand one a nereid, /Verezs sp., the lower
right-hand one, Polynoe brevisetosa. ‘(From living specimens in a
tide-pool on the Bay of Monterey, California.)

the crabs and insects, but either have fleshy unjointed
legs, or various kinds of bristles or spines, or suckers, or
even no external organs of locomotion at all. As regards
their internal structure they have well-organized systems
of organs, which show great variety in character and
degree of complexity. The special sense-organs are
usually of simple character and low degree of functional
development. Reproduction occurs both sexually and
asexually; in some species the sexes are distinct, while
in others both sperm-cells and egg-cells are produced by
the same individual. Asexual reproduction is by budding
or by a kind of simple division or fission. The worms
live either:in salt or fresh water, or in moist, mamddy or
slimy places or as parasites in the bodies of other animals
or in plants. While most worms feed on animal sub-

BRANCH VERMES: THE WORMS 135

stance either living or dead, some feed on living or
decaying plant matter.

Classification. — There is great lack of agreement
among zoologists in the matter of the classification of the
worms. Not only are the various groups which by some
are called classes held by others to be distinct branches,
co-ordinate in rank with the Echinodermata, Ccelenterata,
etc., but the limits of these groups are also constantly
called in question. It will require a great deal better
knowledge of the structure and life-history of these diverse
animals before the matter of their classification is satisfac-
torily settled. We shall consider briefly four of the
various groups (which we may consider as classes) which
include worms either specially familiar to us or of special
interest or importance. One or two examples of each
group (the groups being selected primarily because of the
examples) will be described in some detail. By this
means we may get an idea of the extremely diverse char-
acter of the animals which are included in the heteroge-
neous branch Vermes. |

Earthworms and leeches (Oligochete).—The various
species of earthworms, an example of which has been
studied, are found in all parts of the world; they occur in
Siberia and south to the Kerguelen Islands. They are
absent from desert or arid regions, and some can live
indifferently either in soil or in water. Some near allies
of the earthworms are aquatic, living in fresh or brackish
water, some in salt water near the shore. In size earth-
worms vary from I mm. (5, in.) to 2 metres (2+ yds.) in
length. All show the distinct segmentation of the body
noticeable in the common earthworm already studied.

- The leeches, some of which are familiar animals, are
closely related to the earthworms, although at first glance
the similarity in structure is not very noticeable.

1 36 ELEMENTARY ZOOLOGY

TECHNICAL NOTE.—Some common water-leeches, alive or SS
served in alcohol, should be examined by the class. The animals
are not unfamiliar to boys who “go in swimming” in the small
streams of the country. The body of a leech should be examined
carefully, and drawings of it showing the external structural charac-
ters should be made. |

The body of a leech is flattened dorso-ventrally, instead
of being cylindrical as in the earthworm, and tapers at
both ends. In the live animal the body can be greatly
elongated and narrowed or much shortened and broad-
ened. It is composed of many segments (not as many
as there are cross-lines however; each segment is trans-
versely annulated), and bears at each end on the ventral
surface a sucker, the one at the posterior end being the
larger. These suckers enable the leech to Cita2anml y
to other animals. The mouth is at the tront endef ime
body on the ventral surface and is provided with sharp
jaws. Leeches live mostly on the blood of other animals
which they suck: from the body. The common deech
‘(fastens itself upon its victim by means of its suckers,
then cuts the skin, fastens its oral sucker over the wound
and pumps away until it has completely gorged itself with
blood, distending enormously its elastic body, when it
loosens its hold and drops off.’’ Its biting and sucking
cause very little pain, and in olden days physicians used
the leeches when they wanted to ‘‘bleed’’ a person. A
common European species of leech much used for this
purpose is known’ as the ‘‘ medicinal glecaies 3: ul
leeches are hermaphroditic, that is, the sexes are not dis-
tinct, but each individual produces both sperm-cells and
egg-cells. . Most of the leeches lay their eggs in small
packets or cocoons. This cocoon is dropped in soil on the
banks of a pond or stream so that the young may have a
moist but not too wet environment. The young issue
from the eggs in four or five weeks, but they grow very

BRANCH VERMES: THE WORMS 137

slowly and it is several years before they attain their full
size. Leeches are long-lived animals, some being said
to live for twenty years.

Flatworms NOGE.——
Collect some live fresh-water planarians “aes fig. 30), which are to be
found on the muddy bottom of most fresh-water ponds, and examine
them while alive in watch-glasses of water. Make drawings show-
ing the external appearance, and as much of the internal anatomy
as can be seen. The branching alimentary canal can be seen in
more or less detail, and with higher power of the microscope parts
of the nervous system can be seen also. Have also a tapeworm
preserved in alcohol or formalin to show the very flat and many-
segmented body.

The flatworms include a large number of forms which
vary much in shape and habits. They are all, however,

Fic. 30.—A fresh water planarian, //amvaria sp. (From a living specimen. )

characteristically flat; in some this condition is very
marked. Some are active free-living animals, as the
planarians (figs. 30 and 31), while many live as parasites
in the alimentary canal of other animals, as do the sheep-
fluke and the tapeworms.

The fresh-water planarians (fig. 30), which live com-
monly in the mud of the bottom of ponds, are small,
being less. than half an inch long. They are very thin
and rather broad, tapering from in front backwards. On
the upper surface near the front they have a pair of eyes;
the mouth is on the under surface a little behind the
middle of the body. The alimentary canal is composed
of three main branches, each with numerous small side
branches... One main branch runs forward from the
mouth, and the other two run backwards, one on each
side of the body. There is no anal opening, and the

138 ELEMENTARY ZOOLOGY

alimentary canal thus forms a system of fine branches
closed at the tips, and extending all through the body.
The nervous system is composed of a ganglion or brain
in the front end of the body from which two main branches
extend back throughout its whole length. From these
main longitudinal branches arise many fine lateral
branches.

Of the parasitic flatworms the tapeworms are the best
known. .There are numerous species of them, all of

Fic. 31.—A marine planarian, Leptoplauna californica. (From a living
specimen. )

which live in the bodies of vertebrate animals. In the
adult or fully developed stage the tapeworms live in the
alimentary canal, holding on to its inner surface by hook-
like clinging organs and being nourished by the already |
digested food by which they are bathed. In the young
or larval stage tapeworms live in other parts of the body
of the host, and usually, indeed, in other hosts not of the
same species as the host of the adult worm.

BRANCH VERMES: THE WCRMS 139

The common tapeworm of man, /@nza solium (there
are several other species of J/@nza_ which infest
man, but so/zwm is the common one), may serve as an
example of the group. Inthe adult condition its body,
which is found attached to the inner wall of the intestine,
is like a long narrow ribbon: it may be two or three
metres long. It is attached by one end, the head, which
is very small and provided with a score of fine hooks.
Behind the head the thin ribbon-like body grows wider.
The body is composed of many (about 850) joints called
proglottids. There is no mouth or alimentary canal, the
liquid food being simply taken in through the skin. Each
proglottid produces both sperm-cells and egg-cells; one
by one these proglottids or joints with their supply of
fertilized eggs break off and pass from the alimentary
canal with the excreta. If now one of these escaped
proglottids or the eggs from it are eaten bya pig, the
embryos issue from the eggs in the alimentary canal of
the pig, bore through the walls of the canal and lodge in
the muscles. Here they increase greatly in size and
develop into a sort of rounded sac filled with liquid. If
the flesh of the pig be eaten by a man, without its being
first cooked sufficiently to kill the larval sac-like tape-
worms, these young tapeworms lodge in the alimentary
canal of the man and develop and grow into the long
ribbon-like many-jointed adult stage.

The life-history of the other tapeworms which infest
the various vertebrate animals is of this general type.
There is almost always an alternation of hosts, the larval
tapeworm living in a so-called intermediate host, and the
adult in a final host. Of the domestic animals the dog
is the most frequently attacked. At least ten different
species of tapeworms have been found in the dog. The
intermediate hosts of these dog tapeworms include
rabbits, sheep, mice, etc. Some of the domestic fowl,

140 ELEMENTARY ZOOLOGY

ducks, geese and chickens, for instance, are also infested
by tapeworms, and the intermediate hosts in these cases
are usually insects or small aquatic crustaceans like the
familiar Cyclops.

Roundworms (Nemathelminthes).—Tercunicat Note.—
- Vinegar-eels from mouldy vinegar, and hair-worms from fresh-
water pools, can usuaily be readily obtained. They should be
examined, and drawings should be made of them, showing their
shape and simple external structural character. If a specimen of
trichinosed pork be obtained, the encysted stage of
the 7richina, described in the following account, can
be shown.

The roundworms are slender, smooth,
cylindrical worms pointed at both ends.
They are all very long in proportion to their
diameter, although their actual length may
be short. Some species are of microscopic
size; as the 77zchina worm, which is about
3, in. long; while the guinea-worm, one of
the worst parasites of man, may reach a
length: :of six feet. _Many of the femme
worms are parasites living in the various
organs of other animals. Some, however,
lead an independent free life in water or in
damp earth.

Familiar examples of roundworms are the
so-called vinegar-eels (Anuguzllula) (fig. 32)
to be found in weak vinegar, and other
species of this same genus which live in water
or moist ground or in the tissues of plants,
doing much injury. The hair-worms (Gor-

; : Fic. 32. —A
dius ) or horse-hair snakes, which are believed vinegar eel,
. Angutilula

by some people, to be horse-hairs dropped an cieoin
into water and turned into these animals, are a living
specimen. )

also familiar examples of roundworms. They
are often found abundantly in little pools after a rain, and

BRANCH VERMES: THE WORMS TAT

it is sometimes said that these worms come down with the
rain. They have in reality come from the bodies of insects
in which they pass their young or larval stages as parasites.
The hair-worms all live as parasites during their larval
stage, and as free independent animals in their adult stage.
Some of them require two distinct hosts for the comple-
tion of their larval life, living for a while in the body of
one, and later in the body of
another. The -first ~host is
usually a kind of insect which is
eaten by thesecond host. The
eggs are deposited by the free
adult female in slender strings
twisted around the stems of
water-plants. The young hair-
worm on hatching sinks to the
bottom-of thé pond, where. it
moves about hunting for a host
in which to take up its abode.
The terrible 77zchina spiralis
(fig. 33), which produces the
disease called trichinosis, is
another roundworm of which
much is*heard. “This is’a very
small worm which in its adult
condition lives in the intestine
of man as well as in the pig and
other mammals. The young,

Fic. 33.—7Zvrichina spiralis, en-
cysted in muscle of a pig. j
(From specimen. ) which are borne alive, burrow

through the walls of the intes-
Miaceade are either carried-by the blood, or force: their
way, all over the body, lodging usually in muscles.
Here they form for themselves little cells or cysts in
which they lie. The forming of these thousands of tiny
cysts injures the muscles and causes great pain, sometimes

142 ELEMENTARY ZOOLOGY

death, to the host. Such infested muscle or flesh is said
to be ‘‘trichinosed,’’ and the flesh of a trichinosed
human subject has been estimated to contain 100,000,000
encysted worms. To complete the development of the
encysted and sexless 7vzchine the infested flesh of the
host must be eaten by another animal in which the worm
can live, e.g. the flesh of man bya pig or rat, and that
of a pig by man. In sucha case the cysts are dissolved
by the digestive juices, the worms escape, develop repro-
ductive organs and produce young, which then migrate
into the muscles and induce trichinosis as before. But
however badly trichinosed a piece of pork may be,
thorough cooking of it will kill the encysted 77zchine@, so
that it may then be eaten with impunity. Some people,
however, are accustomed to eat ham, which is simply
smoked pork, without cooking it, and in such cases there
is always great danger of trichinosis.

Wheel animalcules (Rotifera).—TrcunicaL NoTe.— Live
specimens of Rotifers can be found in almost any stagnant water
Examine a drop of such water with the compound microscope, and
find in it afew small, active, transparent creatures, larger than the
Paramectum and other Protozoa in the water and which have the
appearance shown in fig. 34. They may be known by the constant
whirling, or rather vibrating, circlet or wheel of cilia at the larger
or head end of the body. These wheel animalcules may be studied
alive by the class. Although usually darting about, the animalcules
occasionally cease to move, when, because of their transparency,
almost the whole of their anatomy can be made out. Their feeding
habits can also be readily observed, and the food itself watched
as it moves through the body. Make drawings showing as much
of the anatomy as can be worked out. Note especially the ‘‘ mas-
tax’ or gizzard-like masticating apparatus in the alimentary canal.

The wheel animalcules (fig. 34) or Rotifers look little
like the other worms we have studied. But they are
nevertheless more nearly related to the worms than to
any other branch of animals. They are all small, about 4
mm. long, and have a compact body. They are aquatic
and feed on smaller animals and plants or on bits of or-

BRANCH VERMES: THE WORMS 143

ganic matter which they capture by means of the currents
produced by the vibrating cilia of the ‘‘ wheel.’’ Small as

Fic. 34. — A wheel animalcule,
Rotifer sp. (From living speci-
men, Stanford University.)

they are they have a complex
body-structure, with well-or-
ganized systems of organs.
For a long time, however,
they were classed by natural-
ists with the Protozoa on ac-
count of their size. They are
found all over the world,
mostly in fresh water; a few
are marine. More than. 700
species of them are known.
An interesting thing about
the Rotifers is their remark-
able power to withstand dry-
ing-up. When the water in
a pond or ditch evaporates
some of the Rotifers do not
die, but simply dry up and lie
in the dust, shrivelled and

apparently lifeless, yet really in a state of suspended
animation. On being put into water they will gradually
fill out to their fuil size and shape, and finally resume all
their normal activities. In this dried-up condition Rotifers
may persist for a long time, several years even, although
otherwise their natural life is short, being probably of not

over two weeks’ duration.

Certain other of the lower

animals have this same power of withstanding desiccation.

CHAPTER XX

BRANCH ARTHROPODA: CRUSTAGEA iN
TIPEDS, INSECTS, AND? Shipp

THE great branch Arthropoda includes a_ host. of
familiar animals. It contains more species than any other
branch of the animal kingdom. To it belong the cray-
fishes, shrimps, crabs, lobsters, water-fleas, and other ani-
mals which compose the class Crustacea; the centipeds
and thousand-legged worms which compose the class
Myriapoda; the true or six-footed insects forming the class
Insecta, which includes nearly two-thirds of all the known
species of ansmals; and the scorpions, mites, ticks, and
spiders which constitute the class Arachnida. There is
also a fifth class in the branch Arthropoda which includes
a few species of animals unfamiliar to us but of great
interest to zoologists.

All these varied kinds of animals have a body on the
annulate or segmented type-plan, like that shown by most
worms, but they differ from the worms in possessing
jointed appendages, used for locomotion or food taking.
There is typically or racially one pair of these jointed or
segmented appendages on each segment of the body, but
in all of the Arthropoda some of the segments have lost
their appendages. The body is covered by a firm cuticle
or outer body-wall called the exoskeleton. This exo-
skeleton serves not only to enclose and protect the soft
parts of the body but also for the attachment of the body

144

BRANCH ARTHROPODA : CRUSTACEANS 145

Mecetcs., It may be flexible as in the sutures between
the body-segments in most insects, or hard and rigid as
ieee sclerites of the seoments. The firmness is due
primarily, andin the insects usually solely, to a deposit in
the cuticle of c/ztzz, a substance probably secreted by the
underlying cells of the true skin, or it may be due chiefly,
ae tae crabs. to a calcareous deposit. - In such cases it
Mecomes a veritable armor. The internal organs of the
Arthropods show a more or less obvious segmentation
corresponding with the segmentation of the body-wall.
The alimentary canal runs longitudinally through the
Gente, of tae body from mouth to anal opening. The
Mervous system consists of a* brain lying above the
cesophagus and a double nerve-chain running backward
from beneath the cesophagus, along the median line of
the ventral wall, to the posterior extremity of the body.
This ventral nerve-chain consists of a pair of longitudinal
commissures or cords and a series of pairs of ganglia,
arranged segmentally. The two ganglia of each pair are
fused more or less nearly completely to form a single
ganglion, and the nerve-cords are partially fused, or at
letoutewerase together. In addition’ there is a smaller
sympathetic system composed of a few small ganglia and
certain nerves running from them to the viscera, this sys-
tem being connected with the main or central nervous
system. In this group the organs of special sense reach
(jeaieetitse time a high stage of development. Com-
pound eyes are peculiar to Arthropoda. The heart lies
above the alimentary canal. Respiration is carried on by
gills in the aquatic forms, and by a remarkable system of
air-tubes or tracheae in the land forms (insects). The
sexes are usually distinct, and reproduction is almost uni-
_versally sexual. Most of the species lay eggs.

The Arthropods are animals of a high degree of organ-
ization. The extremely diverse life-habits of the various

146 ELEMENTARY ZOOLOGY

kinds among them have led to much modification and to
great specialization of structure. The course of develop-
ment, too, is made very complicated. by the elaborate
metamorphosis undergone by many of the members of the
branch.

We shall study the Arthropoda by getting acquainted
with a few examples of each class and thus learning the
special class characteristics.

CLASS CRUSTACEA: CRAYFISHES, CRABS, LOBSTERS,
Ere:

THE CRAYFISH (Cambarus sp.)

Structure.—The structure of the crayfish has been ~
already studied (see Chapter IV and figs. 3 and 4).

Life-history and habits.—Crayfish frequent fresh-water
lakes, rivers, and springs in most parts of the United
States. Many of them perish whenever the small prairie
ponds dry up. But some burrow into the earth when the
dry season comes. There may be noticed in meadows
where water stands for certain seasons of the year many
scattered holes with slight elevations of mud about them.
These are mostly the burrows of crayfish. During the
dry season the crayfish digs down until it reaches water,
or at least a damp place, where it rests until wet weather
brings it to the surface once more. One of these burrows,
followed in digging a mining shaft, extended vertically
down to a distance of twenty-six feet, where the crayfish
was found tucked snugly away.

The eggs are carried by the female on her abdomina]
appendages. Previous to the laying of the eggs the
female rubs off all foreign matter from the appendages,
thus preparing them for the reception of the eggs. This
cleaning is done with the fifth pair of legs. When the

BRANCH ARTHROPODA : CRUSTACEANS 147

eggs are ready to be laid, which is during the last of
March or in April in the Central States, a sticky secretion
passes out of the openings at the base of the walking legs
and smears the pleopods of the abdomen. The eggs as
they pass out are fertilized and caught on the pleopods,
where they remain attached in clusters. After some
weeks the young crayfishes issue from the eggs. In
general appearance they are not very unlike the adults.
They grow very rapidly at this stage. As the animal is
enclosed in a hard shell, growth can only take place
during the period just following the molt, for the crayfish
casts its skin periodically, and it is while the new shell is
forming that the animal does its growing. The crayfish
when it molts casts not only the exoskeleton, but also the
lining of part of the alimentary canal. After the females
have hatched their young many die in the shallow pools,
in which places the dried-up skeletons are noticeable
during the summer months.

HtHER CRUSTACEANS.

Most of the crustaceans live in water, a few being found
in damp soil or in other moist places. Some are fresh-
water animals and some marine. They vary in size from
the tiny water-fleas, a millimeter long, to crabs two feet
across the shell or sixteen feet from tip to tip of legs.
They present great differences in form and general ap-
pearance of body, being adapted for various conditions
of life. Some crustaceans live as parasites on other
animals, in some cases on other crustaceans. Such
parasitic species have the body much modified and are
‘hardly to be recognized as members of the class.

Body form and structure. — In structural character and
body organization the Crustaceans show, of course, the
general characteristics already attributed to the Arthro-
poda, the branch to which they belong. The character-

148 ELEMENTARY ZOOLOGY

istics which distinguish them from other Arthropods are
the possession of gills for respiration (some insects have
gills, but of a very different kind as will be seen later),
and the bi-ramose condition of the body appendages, each
appendage (excepting the antennules) consisting of a
single basal segment from which arise two branches made
up of one or more segments. Of the form of the crus-
tacean body few generalizations can be made.

‘‘There is no [other] class in the animal amedom
which presents so wide a range of organization as the
Crustacea, or in which the deviations in structure from the
‘type form’ are so striking and so interesting from their
obvious adaptation to the mode of life.’’
no attempt will be made to discuss in general terms the
form of ther crustacean body, but brief accounts will be
given of a few of the more familiar kinds of Crustacea
which will serve to illustrate this remarkable diversity of
body form.

Similarly impossible is it also to give a general account
of the development of the crustaceans, ‘Witessexecs are
distinct in most Crustacea, and there is often great differ-
ence in form. between the male and femmles yacertain -
amount of metamorphosis takes place in the development
of all crustaceans; that is, the young when hatched from
the egg differs, often decidedly, in appearance and structure
from the parent, and in the course of its post-embryonic
development undergoes more or less striking change

For this reason

or metamorphosis. This metamorphosis is often very
marked.

Water-fleas (Cyclops).—Tercunicat Norre.—The water-
fleas are common in the water of ponds or of slow streams; they
may often be found in the school aquarium. They are, though
small (about 1 mm. long), readily seen with the unaided eye; they
are white, rather elongate, and have a rapid jerky movement. Ex-
amine specimens alive in water in a watch glass. Note the “split

”

pear” shape, broadest near the front, tapering posteriorly, flat be-

BRANCH ARTHROPODA : CRUSTACEANS 149

neath, convex above; note the forked stylets at tip of abdomen ; also
the two pairs of antenne, the single median eye, the mandibles, two
pairs of maxille, and five pairs of legs (last pair very small). There
are no gills. Some of the specimens, females, may have attached to
the first abdominal segment on either side an egg sac. Make
drawings showing all these structural details. Watch the Cyclops
capturing and feeding on Paramecium or other small animals.

The water-fleas (Cyclops) (ie. 35). are saimong « the
smallest of the Crustacea. They are extremely abundant,

Fic. 35.—A water-flea, Cyclops sp. Female with egg-masses.
(From living specimen. )

having great power of multiplication. ‘‘ An old Cyclops
mayuproduce forty or filty-eses at once, and may give
birth to eight or ten broods of children living five to six

roe ELEMENTARY ZOOLOGY

months. ‘As the young begin to reproduce at an early
age, the rate of multiplication is astonishing. The
descendants of one Cyclops may number in one year
nearly 4,500,000,000, or more than three times the total
population of the earth, provided that all the young reach
maturity and produce the full number of offspring.’’ The
Cyclops feed on smaller aquatic animals such as Protozoa,
Rotifera, etc. They in turn serve as tood fer mswes- and
because of their immense numbers and occurrence in all
except the swiftest fresh waters ‘‘ they form the main food
of most of our fresh-water fishes while young.’’ Many
aquatic insect larve feed almost exclusively on them.
Related to-the Cyclops are a host of omen ecameceor
minute Crustaceans. Among these the so-called fish-lice
are specially interesting because of their parasitic habits
and greatly modified and degenerate structure. There
are many kinds of these parasitic crustaceans infesting
fishes, whales, molluscs,and worms. ‘‘ As on land almost
every species of bird or mammal has its own parasitic
insects, so in the water almost every species of fish or
larger invertebrate has its parasitic crustaceans.’’ Some
of the most common of these parasites attach themselves
to the gills of fishes. Here they cling, sucking the blood
or animal juices from the host. In form of body they do
not at all resemble other Crustaceans, but are strangely
misshapen. They are often worm-like, or sac-like, with-
out legs or other locomotory appendages. As with other
parasites (see Chapter XXX) an inactive dependent life —
results in the atrophy and loss by degeneration of the
body-parts concerned with locomotion and orientation.

Wood lice (Isopoda).—TECHNICAL NOTE. —Specimens of
wood lice, pill bugs, or damp bugs, as they are variously called, may be
readily found in concealed moist places, as under stones or boards on
damp soil. They are often common in houses, near drains or in dark,
damp places. Examine some live wood lice, and some dead speci-
mens (killed by chloroform or in an insect-killing bottle).

BRANCH ARTHROPODA : CRUSTACEANS 16]

Note the division of the body into the head, thorax, and abdomen ;
find the eyes, the antennz and the mouthparts (mandibles and maxille
are usually pressed closely together). All the locomotory append-
ages are adapted for walking or running, not swimming. Note the

number of pairs of legs; the structure of a leg; find gills and gill-

covers. Some females may be found with eggs on the under side
of the thorax near the bases of the legs, the eggs being covered by
thin membranous plates. Make drawings showing the general
form and character of body and details of legs, gills, etc. Compare
with the crayfish and Cyclops.

The wood-lice (fig. 36) are among the few Crustacea
which have a wholly terrestrial life. They run about
quickly and feed chiefly on decaying
7vesetable matter: . Uhey. are meht
scavengers... [hey have the - body
oval and convex above, rather pur-
plish or grayish brown, and smooth.
Although they do not live in the
water they breathe partly at least by
means of gills (though they may
breathe partly through the skin).
It is therefore necessary for them to
rae te live in a damp atmosphere so that the
Fic. 36.—A damp bug, _.
Isopod, species not de. 811 membranes may be kept damp.
termined. (From speci- If not kept moist they could not
a" serve as osmotic membranes.

i 3 ®
A

.

|

a]

Lobsters, Shrimps and Crabs (Decapoda).—TrcunicaL
NoTE.—Teachers living near the sea-shore can get specimens of
live and dead lobsters, shrimps, and crabs in the markets. Schools
in the interior should have a few preserved specimens for examina-
tion. These specimens should be compared with the crayfish ;
although differences in shape of body are evident, the character
and arrangement of body parts will be found to be very similar.

The largest and most familiar Crustaceans, as the cray-
fishes, lobsters, shrimps, prawns and crabs, all belong
peortme order Decapoda, or ten-legged Crustacea: The
members of this order have, including the large claws,
ten walking feet; they all have eyes on movable stalks,

152 ELEMENTARY ZOOLOGY

-and the front portion of the body is covered by a horny
fold of the body-wall called the carapace.

The lobsters are large ocean-inhabiting crustaceans
which are very like the fresh-water crayfish in all struc-
tural characters. They live on the rocky or sandy ocean-
bottom at shallow depths. They feed largely on decaying
animal matter. They are caught in @reatemeiagecs> in
so-called ‘‘ lobster pots,’’ a kind of wooden trap baited
with refuse. ‘‘ The number thus taken upon the shores
of New England and Canada amounts to between twenty
and thirty million annually.’’ Live lobsters are brownish
or greenish with bluish mottling; they turn red when
boiled. A single female will lay several thousand eggs.
The eggs are greenish and are carried about by the mother
until the young hatch. The young are free-swimming
larve, until they reach a length of halt antimem

The shrimps and prawns are mostly marine, though
some species live in fresh water. Jey uaneesike the
lobsters, used for food. Some of the species are gregari-
ous in habit, occurring in great ‘‘ schools ’’ of individuals.
Like the lobsters they crawl about on the sea-bottom
feeding on decaying animal matter. Shrimps are very
abundant near-San Francisco, where extensivers samim>p
fishing ’’ is done by the Chinese.

The crabs (fig. 37) differ from the lobsters and cray-
fishes and shrimps in having the body short and broad,
instead of elongate. ‘This is due to the special widening
of the. carapace and -the marked. sherenimeset ie
abdomen. The abdomen, moreover, iS permanemily pent
underneath the body, so that but little of it is visible from
the dorsal aspect. The number of abdominal legs or
appendages is reduced. When the tide is out the rocks
and tide-pools of the ocean shore are alive with crabs.
They ‘‘scuttle ’’ about noisily over the rocks, withdraw-
ing into crevices or sinking to the bottom of the pools

BRANCH ARTHROPODA : CRUSTACEANS 153

when disturbed. They move as readily backward or
sidewise, ‘‘crab-fashion,’’ as forward. They are of
various colors and markings, often so patterned as to

Fic. 37.—Some crabs and barnacles of the Pacific coast; the short sessile
acorn barnacles in the upper left-hand corner belong to the genus Aa/-
anus, the stalked barnacles in the upper right-hand corner are of the
species Pollicipes polymenus; the largest crab (upper left-hand) is
Brachynotus nudus; the one in left-hand lower corner is a young rock-
crab, Cancer productus; the crab in the sea-weed at the right is a kelp-
crab, Apzaltus productus, while the two in snail-shelis in lower corner
are hermit-crabs, Pagurus samuelis. (From living specimens in a tide-
pool on the Bay of Monterey, California. )

harmonize very perfectly with the general color and ap-
pearance of the rocks and sea-weeds among which they

ieee ELEMENTARY ZOOLOGY

live. The spider-crabs are especially strange-looking crea-
tures with unusually long and slender legs and a com-
paratively small body-trunk. They include the J/acro-
cheira of Japan, the largest of the crustaceans. Specimens
of this crab are known measuring twelve to sixteen feet
from tip to tip of extended legs; the carapace is only as
many inches in width or length. The soft-shelled crab
is a species common along our Atlantic coast. It is
‘«soft-shelled ’’ only at the time of molting, and has to
be caught in the few days intervening between the shed-
ding of the old hard shell and the hardening of the new
body-wall. The little oyster-crabs (Pzunotheres) which
live with the live oyster in the cavity enclosed by the
oyster shell are well-known and interesting crabs. They
are not parasites preying on the body of the oyster, but
are simply messmates feeding on particles of food brought
into the shell by the currents of water created by the
oysters. :

Among the most interesting crabs are the hermit crabs
(fig. 37), familiar to all who know the seashore. There
are numerous species of these crabs, all of which have the
habit of carrying about with them, as a protective covering
into which to withdraw, the spiral shell of some gastropod
mollusc. The abdomen of the crab remains always in
the cavity of the shell; the head and thorax and Jess
project from the opening of the shell, to be withdrawn
into it.when the animal is alarmed of atemeseaes luc
abdomen being always in the shell and thus protected
loses the hard body-wall, and is soft, often curiously
shaped and twisted to correspond to the cavity of the
shell. It has on it no legs or appendages exeeptepair
for the hindmost segment which are modified into hooks
for holding fast to the interior of the shell sence
hermit crab grows it takes up its abode in larger and
‘arger shells, sometimes killing and removing piece-meal

BRANCH ARTHROPODA : CRUSTACEANS Leis

the original inhabitant. Some hermit crabs always have
attached to the shell certain kinds of sea-anemones. It
is believed that both crab and sea-anemone derive advan-
tage from this arrangement. The sea-anemone, which
otherwise cannot move, ts carried from place to place by
the crab and so may get a larger supply of food, while
the crab is protected from its enemies, the predaceous
fishes, by the stinging threads of the sea-anemone, and
also perhaps by the concealment of the shell its presence
affords. This living together by two kinds of animals to
their mutual advantage is called commensalism or sym-
biosis (see Chapter XXX). The hermit crabs are not true
crabs, but are more nearly related to the crayfishes and
shrimps than to the true broad-bodied, short-tailed crabs.

Barnacles.-—Trcunicat NoTe.—Specimens of barnacles may
be got readily from the tide rocks or from piles in a harbor. In-
terior schools should have, if possible, specimens preserved in
alcohol or formalin for examination. The ‘‘shells” of acorn (ses-
sile) barnacles may often be found on oyster shells (get at restau-
rants).

Crustaceans which at first glance are hardly recogniz-
able as such are the stalked or sessile barnacles (fig. 37)
which live fixed in great numbers on the rocks between
the tide lines, or on the piles supporting wharves, or on
the bottom of ships or even on the body-wall of whales
and other ocean animals. In the stalked forms the stalk
is a flexible stem or peduncle covered with a blackish
finely-wrinkled skin bearing at its free end the greatly
modified body of the barnacle. This body is enclosed in
a sort of bivalved shell or carapace formed by a fold of
the skin and stiffened by five calcareous plates. Within
this curious shell is the compact, rather worm-like body-
mass, showing little or no indication of segmentation.
The legs, of which there are usually six pairs, are much
modified, being long, feathery, and divided nearly to the

156 ELEMENTARY ZOOLOGY

base. These feathery feet project from the opened shell
when the animal is undisturbed, and waving about in the
water catch small animals which serve as the barnacle’s
food. When disturbed the barnacle withdraws its feet
and closes tightly its strong protecting shell. The acorn-
barnacles have no stalk, but look like a low bluntly-
pointed pyramid, this appearance being due to the
converging arrangement of six calcareous plates in its
body-wall.

The barnacles present several unusual conditions with
regard to the internal organs. They have no heart nor
any blood-vessels; most of the species are hermapnroditic ;
and there are other indications of a degenerate condition.
This degeneration of the barnacles is due to their fixed
life, the results of which are like those of a parasitic life.
The young barnacles when hatched from the egg are free-
swimming larve as with the other Crustacea. They
finally attach themselves and undergo the changes, some
of them of degenerative nature, which produce the body-
structure of the adult. It was long a belief among many
people that the barnacle produced the barnacle goose.
Pictures in ancient books show the young barnacle geese
issuing from the opened shell of the barnacle. ‘The early
naturalists believed barnacles, on account of the shell, to
be a kind of shell-fish or mollusc, but when their develop-
ment was thoroughly worked out, it became evident that
they belong to the Crustacea.

CHAPTER XXI

BRANCH ARTHROPODA (continued); CLASS IN-
pee tee THE INSECTS

_ THE LOCUST (Aelanoplus sp.)

TECHNICAL NOTE.—Locusts or grasshoppers are common and
familiar insects all over the country. The genus JJelanoplus in-
cludes numerous species, one or more of which are to be found in
almost any locality. The common red-legged locust (JZ femur-
rubrum) of the East, the Rocky Mountain migratory locust (JZ.
spretus), of the West, the large differential (JZ. differentials) and
two-striped (JZ. divittatus) locusts of the Southwest, are especially
common species. All the members of the genus have their hind
wings uncolored, and the front wings marked with a longitudinal
series of small dots more or less distinct, or with a longitudinal line.
There is a small blunt spine or process projecting from the ventral
aspect of the prothorax. If a species of J/e/anoplus cannot be
found, any other locust may be used, although there are some slight
Variations in the external structure of the various species. Fresh
specimens killed in a cyanide bottle (for preparing see p. 463) are
preferable in the study of the external structure, but specimens
preserved in alcohol will do.

External structure (fig. 38).—Note that the body of
the grass-hopper is composed of successive rings or seg-
ments grouped into three regions, the “ead (anterior),
thorax (median), and abdomen (posterior). In which
region of the body are the segments most readily distin-
guished ? Of how many segments does the head appear
to be composed? The thorax is composed of three
segments of which the most anterior, to which is attached
the front pair of legs, differs from the succeeding two,
_ being freely movable and bearing a large hood- or saddle-
shaped piece on its dorsal aspect. To the other two

thoracic segments the second and third pair of legs are
157

158 ELEMENTARY ZOOLOGY

attached, as are also the two pairs of wings. The re-
maining segments of the body compose the abdomen.

Note the smooth, rather firm and horny character of
antenne#

7.
ia Aa
de 7
ee

P

JF ;

SC <<< auditory organ
SF fi

g ocellus }

Jf ‘head compound eye!
- aa / 7 /

is oo !

Ff] Bod '
J Pronotum horas
ce Os ! f

~-ovtpositor

eo

\

-. ubdomen |

‘

femur

tibia”

\trochanter

RW spiracled
tarsal segments
Fic. 38.—The red-legged locust, A/elanoplus femur -ruérum, to show ex-
ternal structure,
the body. This is due to the fact that the skin is every-
where covered with a cuticle in which is deposited a
horny substance called chztzn. The cuticle is not uni-
formly firm over the body. At the junction of the body
segments in the abdomen, in the neck and between the
segments of the legs, in fact, wherever motion is desir-.
able, the cuticle is flexible, thus making bending of the
body-wall possible. Elsewhere, however, it is hard and
stiff, serving not only as a protective coat or armor over
the body, but also affording firm places for the attachment

of muscles.
Insects (and all other Arthropods) have no™* interna)
skeleton, but, in this firm cuticle, an exoskeleton.
Although the head is apparently a single segment, it |

* There are in many forms a few internal projections from the exterior
cuticle which act as internal skeletal pieces.

BRANCH ARTHROPODA; CLASS INSECTA: THE INSECTS 159

is really composed of six or seven body segments greatly
modined and firmly fused together. Note that it. bears
a pair of large compound eyes and three much smaller
simple eyes or ocellt.

TECHNICAL NOTE.—Strip off a bit of the outer covering of a
compound eye, mount on a glass slide and examine under the
MICrOSCOpe. .

Note that, as in the crayfish, each compound eye is
composed externally of many small hexagonal facets, the
outer covering, the cornea, being simply the cuticular cover-
ing of the body, in this place transparent and divided into
small facets. Besides the eyes, the head bears also several
movable appendages, namely the aztenne@, and the
mouth-parts. Note the number, place of insertion, and
segmented character of the antenne. These antenne are
sense-organs and are used for feeling, smelling, and, in
some insects, for hearing. Note that the mouth-parts
consist of an upper, broad, flap-like piece, the */adrum, of
a pair of brown, strongly chitinized, toothed jaws or
mandibles; of a second pair of jaw-like structures, the
maxtlle, each of which is composed of several parts; and
of an under, freely-movable flap, the /aézum, also com-
Posed, Gf several pieces. Itach maxilla bears. a slender
feeler or palpus composed of five segments. The labium
bears a pair of similar palpi, which are, however, only
three-segmented. The mandibles and maxilla, which
are the insect jaws, move laterally, not vertically as with
most animals.

Make drawings of the lateral aspect of the head; of a
bit of the cornea; of the dissected out mouth-parts.

Of the three segments of the thoracic region of the
body, the most anterior one is called the prothorax. It
is freely movable and has a large hood or saddle-shaped

* The labrum differs from the other mouth-parts in not being composed of
a pair of body anpendages ; it is simply a fold or flap of the skin of the head.

160 ELEMENTARY ZOOLOGY

piece, the pronotum, on its dorsal aspect, and a blunt-
pointed tubercle on the ventral aspect. The foremost
pair of legs is attached to the prothorax. The next
segment is the mesothorax, which is immovaly fused to
the next thoracic segment. What appendages does it
bear? The third segment. is the mefathovag= awhich
besides being fused with the mesetherax in airone is
similarly fused with the foremost abdominal segment
behind. What appendages does the metathorax bear ?

Examine one of the-fore legs and mote sine ise com-
posed of a series of unequal parts) ef segumcmmes he
segment nearest the body is sub-globular and is called
the coxa; the second segment is smaller than the coxa
and’ is called the ¢rochanter; the third Simewmeace tic
Jemur, is the largest of all; the fourth, zzéza, is long and
slender; and the next three, the last of which is the
terminal one and bears a pair of claws and between them
a little pad, the pulvzllus, are called the ¢arsal segments.
Most insects have five tarsal segments. Note the great
size of the hindmost or leaping legs. Determine the seg-
ments of the middle and hindmost legs. Make a draw-
its Of a tore lec.

Examine the wings. In what ways do the front wings
differ from-the hind wings? The front wings are known
as the wing covers or ¢egmina. Note how the hind wings
fold up like a fan, and are covered and protected by the
wing covers. Draw the wings.

The abdomen is composed of a number of segments
most of which resemble each other. The first seoment
(immediately behind the metathorax) has its dorsal and
ventral parts widely separated by the cavities for the in-
sertion of the hindmost legs. The ventral part of this
segment is dovetailed into the ventral part of the meta-
thorax and appears to be part of it. In the dorsal part
of this segment there is on each side a spot where the

BRANCH ARTHROPODA ; CLASS INSECTA: THE INSECTS 161

cuticle is only a thin membrane. At these places are
the auditory organs or ears of the locust. The thin
membranes are the ¢ympana. Only the various kinds of
locusts and those insects closely related to them have ears
of this kind. Most other insects are believed to have the
sense of hearing situated in the antenne.

The abdominal segments from second to eighth are ring-
like.in form and are without appendages. There is on
the side of each of these segments near its front margin a
tiny opening or pore called a spzracle. These spiracles
are the breathing pores of the locust, which does not take
in air through its mouth or any other opening in the head.
There is a spiracle near each ear in the first abdominal
segment, and one on each side of the mesothorax near
the insertion of the middle legs.

The terminal segments of the abdomen are provided
with certain processes which are different in male and
female. The female has at the tip of its abdomen two
pairs of strong, curved poirted pieces which compose the
ovipositor, or egg-laying organ. The opening of the
oviduct lies between the pieces. The male has a swollen
rounded abdominal tip, with three short inconspicuous
pieces on the dorsal surface.

Make a drawing of the lateral aspect of the abdomen
of a female locust; also, of a male.

For a more detailed account of the external anatomy of
a locust see Comstock and Kelloge’s ‘‘ Elements of In-
Beet mihatomy, chap. Il. .

The external structure of the grasshopper should be
carefully compared with that of the crayfish; pay special
attention to the mouth-parts and legs.

The teacher should point out the homologies and
‘modifications.

Life-history and habits.—-The eggs of the locust are
laid in the autumn in the ground in bare dry places,

162 ELEMENTARY ZOOLOGY

as roadsides, closely-grazed pastures, etc. The female
thrusts her strong ovipositor into the soil, and by opening
and shutting it, thus boring, pushes in the abdomen for
about two thirds its length. The eggs, about one hun-
dred, are then deposited in acapsule or pod. The young
locusts hatch in the following spring. When_ just
hatched they resemble the parent decust. i = semeral
appearance and structure except that they lack wings,
and are of course very small. The youne-tocusts are
gregarious, congregating in warm and sunny places.
They feed on green plants and travel about by walking
and hopping. At night they try to find shelter under
rubbish in the fields. They feed voraciously and grow
rapidly, reaching maturity in about two months. During
this post-embryonic development and growth they molt
(shed the chitinous exoskeleton) five times: 2=mer the
first molt indications of the wings appear in the shape of
small backward and downward prolongations of the pos-
terior margins of the dorsum of the mesothorax and
metathorax. With each succeeding molt these wing-
pads, or developing wings, are larger and more wing-like,
until after the last molting they appear fully developed.
With each molting, too, there is a marked increase in
size of the locust, the average length of the body just
before the first moult being 4.3 mm., before the second
6.8 mm., before the third © mm., before the fourca 14
mm., before the fifth 17 mm., and after the fifth (the full-
grown stage) about 26 mm.

The molting is an- interesting process, and can be
readily observed. The young locust ready for its last
molt crawls up some post, weed, grass stalk, or other
object, and clutches this object securely with the hind
feet. The head is generally downward. The locust
remains motionless in this position for several hours, when
the skin suddenly splits along the back from the middle

BRANCH ARTHROPODA ; CLASS INSECTA: THE INSECTS 163

of the head to the base of the abdomen. By steady
swelling and contracting and slight wriggling, lasting for
half an hour to three-fourths of an hour, the old skin is
completely shed, and the wings spread out. In an hour
the wings are dry and the new chitinized exoskeleton
firm enough for flying, or crawling about, and in another
hour the locust begins to eat.

The red-legged locust does considerable damage to
cultivated crops, but its injuries are insignificant compared
with the tremendous losses occasioned by a near relative,
the Rocky Mountain Locust (Welanoplus spretus). This
locust has its breeding-grounds on the high plateaus of
the Rocky Mountain region, but it sometimes migrates in
countless numbers southeast over the plains and into the
great grain-fields of the Mississippi valley. Such migra-
tions occurred in 1866, 1867, 1874 (in this year eighteen
hundred and forty two families in Kansas were reduced
to destitution by the utter wiping out of their crops by
the locusts) and 1876. With the settling-up of the
regions in which the Rocky Mountain locust breeds, there
seems to have come a change of conditions, so that no
great migrations have occurred since 1876.

THE GREAT WATER-SCAVENGER BEETLE (//ydrophilus sp.)

TECHNICAL NOTE.—The great water-scavenger beetles are
large, black, elliptical insects common in quiet pools where they
may be found swimming through the water, or crawling among the
plants growing on the bottom. They are an inch and a half long
and are readily distinguishable from all other water insects except
the predaceous diving beetles (Dyticus). The antenne of AHydro-
philus, however, are thickened (clavate) at the tip, while those of
Dyticus are thread-like for their whole length. The beetles may
be readily collected with a water-net, and kept alive in glass jars
or aquaria in water containing decaying vegetation.

External structure (fig. 39).—Is the body of the water-
beetle composed of segments ? Can you make out three
body-regions, ead, thorax and abdomen? As in the
locust the setathorax is fused with the first abdominal

164 ELEMENTARY ZOOLOGY

mouth-parts
f.--magillary palpi

labvim-=-
compound eye---

~“*prothorax
--mesothorax
metathorax

Fic. 39.—Ventral aspect of male great water-scavenger beetle,
Hydrophilus sp. .

meee ARTHROPODA; CLASS INSECTA: THE. INSECTS 165

segment and with the mesothorax, while the prothorax
is freely movable, and is covered above by a strong shield.
The chitin armor of the whole body is specially heavy
and strong, affording a great protection to the insect.

On the flattened head note the compound eyes and the
peculiarly-shaped nine-segmented antenne. Are there
any eeeliz? Wissect out the mouth-parts. ‘The beetle's
mouth is fitted for biting, the mouth-parts being in general
character like these of the locust, with distinct flap-like
labrum, dentate mandibles, jaw-like maxille with long,
slender, four-segmented falpz and lip-like /aézum with
three-segmented palfz. Make drawings of the antenne
and mouth-parts.

Mae me character of the thoracic segments: Ex-
amine the wings and legs. The fore wings are modified
into strong horny sheaths, or e/ytra, which completely
cover and protect the folded hind wings. ‘The hind wings
are large and membranous. How are they folded ? Note
the adaptation of the middle and hind legs for swimming.
Deere the various seoments of the legs, 1.e. coxa,
trochanter, femur, tibia and tarsus. Note the long longi-
tudinal median keel on the ventral aspect of the thorax.

The abdomen articulates with the metathorax by the
full width of the broad first abdominal segment. It is
composed of a series of segments without appendages, of
about equal length but decreasing in width from in front
backwards. Of how many segments does the abdomen
seem to be composed when viewed from the ventral
aspect ? From the dorsal ?

Make a drawing of the ventral aspect of the whole
body. :

TECHNICAL NOTE.—After examining the abdomen thus far, re-
move it from the rest of the body, and boil it in dilute potassium
hydrate (KOH) in a test-tube. This will soften and partially bleach
the body wall, 3

166 ELEMENTARY ZOOLOGY

Examine the softened specimen, and note that at least
two additional segments are to be found retracted or tele-
scoped into the apparently last segment. The character
of these terminal abdominal segments differs in male and
female individuals, and specimens of both sexes should be
examined. (The males can be distinguished from the
females by the peculiar pad-like expansion of the last
tarsal segment of the fore legs.) Pull out the retracted
segments, and note that they are unevenly chitinized,
parts of their surface being simply membranous. Project-
ing backwards are several long-pointed processes. The
female has but: one retracted Seomenteiinenem. tic
females of many insects possess more or less elaborately
developed egg-laying organs, this is not the case with the
beetles. . Look for spzracles near the lateral tassims of
the dorsal surface of the abdomen. How many pairs are
present ?

Internal structure (fig.40).—TECHNICAL NoTE.—If fresh speci-
mens are to be had, kill by dropping into the cyanide bottle (see p.
463). Specimens preserved in a 5% solution of chloral hydrate may
be used if necessary. “When putting specimens into this solution a
small slit should be cut through the body wall to allow the preserv-
ative-to enter the body cavity. When ready to dissect a specimen
cut off the elytra and wings close to the base, and carefully remove
all of the dorsal wall of the abdomen and thorax and the. median
portion of the dorsal wall of the head. Pin out, ventral side down,
under water in a dissecting-dish.

Note in the median dorsal line of the abdomen a pale
transparent longitudinal vessel, the Zeart or dorsal vessel.
Note on each side of it six prominent triangles or ‘‘ Vs’’
with apex of each directed laterally, the posteror three
smaller than the anterior three of each side. These tri-
angles are formed by respiratory tubes or ¢rachee. From
each spiracle or breathing-pore there extends into the
body a respiratory tube or trachea. These lateral trachez
join a main longitudinal trachea on each side, from which

BRANCH ARTHROPODA ; CLASS INSECTA: THE INSECTS 167

are given off branches, which in turn repeatedly subdivide,
until all parts of the body are ramified by trachee, large
and small, bringing air to all the tissues. The oxygen is

a ln

>_..LTOP

aie elytron

aa

<—
>=
>

viduct”** &99- ibe 5

eaee TD shlpig hia
accessory glands’ rectum '

tubules
=. receptaculum seminalis

Fic. 40.—Dissection of female great water-scavenger beetle, Mydrophilus
sp., the heart and trachez being cut away.

*: intestine

taken up from this air, and carbonic-acid gas is given up
to it, when it passes out of the body again through the
spiracles. Thus in the insects oxygen and carbonic-acid

168 ELEMENTARY. ZOOLOGY

gas are not carried by the blood but by special air-tubes.
The respiratory system of insects is —e different from
that of other animals.

Mount a bit of trachea in glycerine on a glass slide and
examine under the microscope. Note the fine spiral line
(looking like transverse annular striations) which is a
thickening of the chitinous inner wall of the tube and
which by its elasticity keeps the tracheal tubes open.

The heart, already noted, is composed of a longitudinal
series of very thin-walled chambers, each with a pair of
lateral openings into the body-cavity and with terminal
openings into the adjacent chambers. The blood, which
is colorless or greenish or yellowish, is sent forward
through the successive heart chambers by regular contrac-
tions until it finally pours from the most anterior chamber
freely into the body-cavity. Here it bathes the body-
tissues, flowing perhaps in regular paths, giving up food
to the tissues and taking up food from the alimentary
canal, until it finds its way through the lateral openings
into the heart chamber again. There are no arenes or
veins.

Note the large mass of muscles in the metaeworax.
Note, by attempting to remove it, that the anterior part
of the muscle mass is attached to a chitinous partition-wall
between the meso- and meta-thorax. Remove this parti-
tion-wall (and one between the metathorax and abdomen)
and note that certain muscles run deeply down into the
body. By pulling on the bits of chitti tommimich tie
muscles are attached, the muscles (if they have not been
cut) can be stretched to the length of three-quarters of an
inch. . When released they will contract. ~ (Wiis eteeten -
ing and contracting takes place only in fresh specimens. )
What are these large and numerous muscles of the thorax
for?

Remove the thin membrane stretching over the abdomen

Beene ARTHROPODA ; CLASS INSECTA: THE INSECTS 169

and in which the heart and tracheal ‘‘ Vs’’ lie, and note
immediately underneath it the large coiled zzfestzne with
a knot of greenish yellow threads in the centre. Carefully
uncoil and pin out the intestine, cutting away the tying
Eeaches, but being: careful not to cut other structures.
Work out the full length of the alimentary canal, noting
the wsophagus, the widened crop behind it, and the long
intestine. From the intestine arise several greenish
vellow threads, the Malpighian tubules. Vhese are the
excretory organs of the insect. What is the total length
of the alimentary canal ?

The reproductive organs, consisting of a pair of glands
(egg-glands or sperm-glands) with a pair of tubes which
unite before reaching ithe body-wall and have a common
external opening, may now be seen. [hese should be
removed, thus exposing the veutral nerve-chain in the
abdomen. To expose the chain in the thorax it will be
necessary to pick away carefully the muscles. As in the
crayfish, the central nervous system in the beetle consists
of a ventral nerve-chain, a dram or supra-ewsophageal
ganglion and a pair of corcum-wsophageal commissures
connecting the brain and the foremost ganghon (zz/ra-
@sopuacen/) in the ventral chain. .lhere are, in the
ventral chain, four ganglia in the thorax and four in the
abdomen. The large nerves running from the brain to .
the compound eyes and to the antenne can be traced.

Make a drawing showing the nervous system.

Life-history and habits.—The eggs, usually about
one hundred, are deposited in a silken sac or case which
is spun by the female, and either floats freely or is attached
to the under sides of the leaves of aquatic plants. This
ege-case is not wholly filled with eggs but has a consider-
able air-chamber in it, causing it to float. It is oval in
shape, and has a peculiar curved horn-like projection at
the upper end. In sixteen or eighteen days the young

170. ELEMENTARY ZOOLOGY

-water-scavenger beetles hatch as elongate, wingless,
active larve, provided with three pairs of legs and strong
jaws. They remain for a short time after hatching in the
egg-case, feeding on each other! After they issue from
the case they feed on flies or other insects which fall into
the water, and on snails. ‘They breathe through a pair
of spiracles situated at the posterior tip of the abdomen,
coming to the surface and thrusting this tip up so that the
spiracles are out of water. They grow rapidly, molting
three times before becoming full grown. They attain a
length of nearly three inches. When full grown they
leave the water, crawling out on the damp shore of the
pond or stream, and burrow into the soil for a few inches.
Here they molt again, or pupate as it is called, changing
to a non-feeding, quiescent stage called the pupal stage.
The pupa is the stage in which the great changes from
wingless, crawling and swimming, short-legged, long,
slender-bodied larva to winged, swimming and flying,
long-legged, compact, broad-bodied adult are completed.
Late in the summer or in the fall the pupal skin breaks
and the adult issues. It works its way to the surface of
the ground, and betakes itself to the nearest water.

The water-scavenger beetle shows in its post-embryonal
development a ‘‘ complete metamorphosis ’’ as contrasted
with the ‘‘incomplete metamorphosis ~-of the locust.
Wherever among insects similar changes occur, the young
issuing from eggs as larve only remotely resembling the
parent, and these active feeding larve changing finally
into more or less quiescent, strictly non-feeding pupe,
which finally change into the active adults, a complete
metamorphosis is said to exist. All the beetles, the
butterflies and moths, the two-winged flies, the ants, bees
and wasps, and certain other groups of insects undergo in
their post-embryonic development a complete metamor-
phosis. The crickets, katydids, the sucking bugs, the

BRANCH ARTHROPODA; CLASS INSECTA: THE INSECTS 171

May-flies, the white ants and numerous other insects
have, like the locust, an incomplete metamorphosis, that
is, the young when hatched resemble in most respects,
except in the absence of wings, their parents.

The adult water-scavenger beetle feeds chiefly on
decaying vegetation in the water, but instances of the
taking of other insects and of snails have been noted.
Although an aquatic insect the beetle, like its larva, has
no gills for breathing the air which is mixed with the
water, but has to come to the surface occasionally to
obtain air. This it does in an interesting way, which
should be carefully observed by the pupils. The air is
received and held by a covering of fine hairs on the ven-
tral surface of the body, so that a considerable supply may
be carried about by the beetle while underneath the sur-
face. The beetles often leave the water by night, flying
abroad to other ponds or streams. In winter the beetles
hibernate, burying themselves in the banks of the ponds
which they inhabit.

For a good account, with illustrations, of the water-
scavenger beetle’s life-history see Miall’s ‘‘ Natural His-
tory of Aquatic Insects,’’ pp. 61-87.

THE MONARCH BUTTERFLY (Azxosia plexippus)

TECHNICAL NOTE.—The Monarch or Milkweed butterfly is dis-
tributed ail over the country. It is large, and red-brown in color,
and lays its eggs on milk weeds where the greenish yellow and black-
banded larve (caterpillars) may be found feeding. The covering
of scales conceals the outlines of the various external parts, but
these scales may be easily removed with dissecting needle and a
small brush. In brushing the scales from the head care must be
taken not to break of the mouth-parts.

External structure (fig. 41).—Note the three body-
regions, head, thorax and abdomen. Is the body seg-
mented ? Note the dark color and firm character of the

chitinized cuticle.

172 ELEMENTARY ZOOLOGY

Note on the head the large compound eyes. Note the
tumid convex c/ypeus which composes most of the anterior

| aspect of the head. Are oce//i present? Compare the
antenne with those of the locust and water-beetle. Com-
pare also the mouth-parts and note that they differ radi-
cally from those of the locust and beetle. They are not
fitted for biting, but for sucking up liquid food (the nectar
of flowers). Note the absence of a movable flap-like
labrum (a minute narrow stiff piece, bearing at each lateral

compound eye,
.

antennz......$---.

prothorax, y

. metathoraxz “abdomen”

TS ~.\ mesothorax
: i coxa
“trochanter
femur

\ ip | :
‘. tarsal segments

a

Fic. 41.—Body of the monarch butterfly, Avosta plexippus, with scales re-
moved to show the external parts,

end a small group of fine brown hairs, represents the
labrum), the entire absence of mandzbles, and the absence
of a movable flap-like labium. The /abzum is a fixed
chitinized triangular piece forming part of the floor of the
head. Note the long slender prodosczs coiled up like a
watch-spring. (In fresh specimens this proboscis can be
uncoiled and will be found flexible. If dried or alcoholic
specimens are being studied, the head of the butterfly

BRANCH ARTHROPODA; CLASS INSECTA: THE INSECTS 173

should be removed and softened in warm water before the
mouth-parts are examined.) On either side of this
proboscis is a peculiar pointed process which rises from
the under side of the head. These processes are the
labial palpi and serve to protect the sucking proboscis.
The proboscis itself is composed of the two greatly modi-
fied maxille. Instead of being short, jaw-like and com-
posed of several pieces as in the locust, in the butterfly
each maxilla is a slender, flexible half tube applied against
its‘mate on the opposite side in such a way as to form a
perfect tube long enough to reach into the nectaries of
flowers when in use and capable of being compactly coiled
up at other times. Cut across the proboscis and note the
canal in the centre. Try to separate the two maxille
which compose it.

Make a drawing of the frontal aspect of the head with
the eyes and appendages.

Compare the thorax with that of the beetle and that of
the locust. The fprothorax is a freely movable narrow
ring or collar. The mesothorax and metathorax are fused
to form a large convex mass, of which fully five-sixths is
mesothorax and only one-sixth metathorax. Try to dis-
tinguish the boundaries of the two segments. Note the
three pairs of legs; the differences in size among them,
and the differences between them and the legs of the
inenst ane water-beetle. In one -of the legs determine
the coxa, trochanter, femur, tibta and tarsal segments.
Note the differences between the wings of the butterfly
and those of the locust and beetle. Note that the wings
are membranous, but are covered with many fine scales
(fig. 42), as is, indeed, the whole body. Rub off some of
these scales on a glass slide and examine; note shape,
little stem or pedicel of insertion, and longitudinal stria-
tions. Examine under microscope a bit of wing from which
some of the scales have been rubbed. How are the scales

174 ELEMENTARY ZOOLOGY

attached to the wing membranes? How are the scales
arrangéd ? Note that the wing is eolerlesss mien: inc
scales have been removed. All the colors and patterns
of the wings of butterflies are produced by the scales.

Make drawings of scales; of parts of denuded wings,
and of bit of wing covered with scales.

Remove all or nearly all the scales from a wing and
note the arrangement of the vezzs (venation). Compare
with venation in wings of locust.

Make drawing showing venation in the butterfly’s
wings.

The venation of insects’ wings is much used in insect
classitication...2m@ + the

\, fas various veins have been
) hit given names. hie
i\ vt) REN names of the veins in

SW | II oF in an é .
TA wh “n ‘a- (ay the butterfly’s wings are
D0 eae 4. «tt) oiven in fig. 43. When

S aos

t Bk &

=
———

hat, Pe y "| the veins in: the wanes
os | of all the various groups

——= = ei < = c— - = =
—_ = — 3

Kot 22a oan 0 4a 8 PSY OL INSCCESs Are StMmIea,. IL

4 a

is evident that the prin-

wy ey Af iy 7 cipal ones are the same
! rh } my i BN ALTA : 2
Rally ‘inkoe ‘ } in all @nsectssssoe tat

Fic. 42.—Bit of wing of monarch butterfly, the costa, sub-custa, ra-

Anosia plexippus, magnified to show the dius, media, cubitus and
scales; some scales removed to show the | : Cihestater
insertion-pits and their regular arrange- See he GE ee a
ment, (From specimen. ) fly’s wings can be com-
pared with the corresponding veins in the wings of a
beetle or wasp or fly. Noting the differences in the num-
ber and character of branching of these principal veins,
and the number and disposition of the cross-veins which
connect the longitudinal veins, the various kinds of insects
can be to a large extent properly grouped or classifed.

A detailed account of the wing-veins of insects is given

BRANCH ARTHROPODA ; CLASS INSECTA: THE INSECTS 175

in Comstock and Kellogg’s ‘‘ Elements of Insect Anat-
omy, chap. VII.

Of how many segments is the abdomen composed ?
The first or basal segment is depressed, while the others are
more or lesscompressed. The sfzracles are, as in the locust,
situated on the lateral aspects of the abdominal segments.
What segments bear spir-
acles ? The terminal seg-
ments of the abdomen
differ in the two species.
In the female the dorsal
part of the ‘apparently)
last segment is longer
than the ventral part and
is bent down over it form-
ing a sort of hood overa
space enclosed partly by
this hood, partly by a
bluntly-pointed projection
from the ventral surface,
and party by the lateral
margins of the segment.
In this chamber lies the

opening from which the Fic. 43.—Wings of monarch butterfly,
Bee, Tn the male Aare atone to chow venation:
there are several back- vein; cu, cubital vein; a, anal veins.
ward projecting, horny, {2,sition most insets haven, ven
thin processes, dial veins called the median vein.
Make a drawing of the lateral aspect of the whole body.
Life-history and habits.—The tiny, conical, yellowish-
ereen eggs of the monarch butterfly are deposited on the
under side of the leaves of milkweeds (Asclepzas) and
when examined under the microscope are seen to be very
beautiful little objects finely ribbed with longitudinal and
transverse strie. The eggs are laid in April and May
(depending on the latitude and season) by females which

176 FLEMENTARY ZOOLOGY

have hibernated in the adult condition. From the eggs
the minute, cylindrical, pale-green, black-headed larve
hatch in four or five days. As soon as hated) the
larva devours the eggshell from which it has escaped and
then feeds voraciously on the milkweed leaves. It grows
rapidly, and in three or four days a blackish band or ring
appears on each segment, and for the rest of its life it is
very conspicuously colored with its black rings on a
yellowish-green background. It molts three times, and
in from twelve to twenty days is ready to pupate;, or
change to a chrysalis.

When ready to pupate the larva usually leaves the
milkweed plant, and seeks some such protected place as
the under side of a fence-rail or jutting foe siete. it
attaches its posterior extremity by a smali silken web to
the rail or rock, and casting its larval skin appears as a
beautiful pale-green chrysalis with ivory black and golden
spots. It hangs motionless, and of course without taking
food, for from a week to two weeks (according to
season and temperature), when the pupal cuticle breaks
and the great red-brown butterfly (fig. 165) issues.

The butterfly feeds (as is indicated by the structure of
its mouth-parts) very differently from the larva; it sucks
up by means of its long tubular proboscis the nectar of
flowers, nor does it confine itself at all to the flowers of
milkweeds. It is a fine flyer and a great traveller. Many
thousands of these butterflies often make long flights or ~
migrations together. At other times tens of thousands
of these butterflies congregate in a certain lgmitedyanea:
clinging sometimes to the branches of a few trees in such
numbers and so closely together as to give the aree a
brown color. Such a ‘‘sembling’’ of monarch butterflies
occurs every year near the Point Pinos lighthouse on
the Bay of Monterey, Califorma. The ebjectaar this
assembling together is not understood. Both the larve
and adults of the monarch butterfly are distasteful to birds,

PRANGH. ARTHROPODA ; CLASS INSECTA: [HE INSECTS £77

by their possession of an acrid body-fluid. The species
is thus protected against the most dangerous enemies of
butterflies, a fact which chiefly accounts for the great
abundance and wide distribution of the monarch (see
p. 137). For a full account of the life-history of the
menaren butterily,:see “ Scudder’s Life of a Butterfly.”’

LARVA OF MONARCH BUTTERFLY (Anosia plexippus)

TECHNICAL NOTE.—For directions for finding and identifying the
larve of the monarch butterfly see p.171. If larve (caterpillars) of
Anosia cannot be found, those of any other butterfly or moth will
do. Use naked, smooth kinds like cutworms, cabbage worms and
the like, rather than hairy or spiny ones. Use large specimens.
Kill the caterpillar with ether or in a cyanide bottle.

Structure (fig. 44).—Aswe have learned from the study
of the life-history of the locust, water-beetle and butterfly,
some insects are hatched from the egg in a condition
resembling that of the parents in most structural charac-
ters. This is true of the locust. Other insects, as the
beetle and butterfly, are hatched in a form and condition
apparently very different from that of the parents. The
external appearance of a beetle or butterfly larva differs
much from that of the adult or imago of the same indi-
vidual. It wili be of interest to examine more particu-
larly the structural condition of one of these larve and to
compare it with the structure of the adult.

Is the body segmented? Is the body composed of
head, thorax and abdomen? Note the soft, flexible,
weakly-chitinized condition of the dody-wall. How many
Poor lees are there? Where are they situated? Is
tere any difference in the various legs? If so, what is
the difference ? Which of the legs of the larva correspond
with the legs of the butterfly? Why? The prothoracic
segment and the abdominal segments I to 8 each bear a
pair of sfzracles (small blackish spots on the sides). Are
both compound and simple eyes present ? How many eyes

ELEMENTARY ZOOLOGY

178

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J

saya}

jouns hanyuawmep

peeved? ARTHROPODA ; CLASS INSECTA: THE INSECTS 179

are there? Are there antenne? Dissect out the smouth-
parts. How do they differ from those of the butterfly ?
Are they more like the mouth-parts of the butterfly or
more like those of the locust?

With fine sharp-pointed scissors make a shallow longi-
tudinal incision along the whole length of the dorsal wall.
In a freshly-killed specimen a drop of pale greenish blood
will issue as the scissors’ point is first thrust through the
skin. Puta droplet of this blood ona glass slide, cover
with cover glass and examine with high power of the
microscope. Note that the blood is a fluid containing
numerous sub-circular or elliptical bodies, the dlo0d-
corpuscles. Note at least two kinds of corpuscles: most
abundant a granular, circular kind, the true blood-corpus-
cles; and rarer, a larger, clear, usually elliptical or oval,
but sometimes irregular and amcebiform kind, generally
spoken of as fat-cel/s.

Make a drawing of the corpuscles in the field of the
microscope.

After making the dorsal longitudinal incision pin out
the caterpillar in the dissecting-dish with dorsal aspect
uppermost. When the edges of the skin are pinned back,
the organs most conspicuous in the body-cavity will be
the flocculent masses of adipose tissue, the large, simple,
tubular alimentary canal usually dark or greenish because
of the color of its contents, and the numerous silvery
tracheal tubes. In those caterpillars which spin a silken
cocoon, the sz/k or spinniug-glands are usually long and
prominent. They lie on either side of the anterior part
of the alimentary canal, and open by a common duct on
the labium. Rising from behind the middle of the ali-
mentary canal may be found the long, whitish, folded and
twisted Malpighian tubules. By picking away the fat
masses, expose the full length of the alimentary canal.
Note its great size (large diameter). Is it divided into

180 ELEMENTARY ZOOLOGY

distinct regions such as crop, proventriculus, stomach,
intestine, etc. How is it held in place tiace the
principal longitudinal tracheal trunks. Find, if you can,
a pair of small compact bodies usually somewhat elongate,
one lying on each side of the posterior part of the alimen-
tary canal. These are the rudimentary reproductive
organs.

Remove the alimentary canal by cutting it off at its
posterior tip and also in the prothoracic segment. Work
out now the ventral nerve-cord and gangla, and the
supra-esophageal (brain) and infra-ewsophageal gangla
and the commissures in the head.

In the body of the caterpillar we have found the same
general disposition of organs as in the body of an adult
insect, but several differences are nevertheless noticeable,
viz., the presence of a large quantity of fatty tissue, the
great size and simple character of the alimentary canal,
and the undeveloped condition of the reproductive organs.

OTHER: INSECTS

The class Insecta includes those Arthropods which
have one pair of antenne (sense appendages), three pairs
of mouth-parts (oral appendages), and three pairs of legs
(locomotory appendages). The insects, in further con-
tradistinction to the crustaceans, are mostly land animals
and breathe by means of trachee or tracheal gills. They
are the most familiar of land invertebrates, and, as already
mentioned, include more species than are comprised in all
the other groups of animals taken together. Beetles.
moths and butterflies, flies, wasps and bees, dragonflies
and grasshoppers are familiar members of the class of
insects, but spiders, mites, scorpions, centipeds and
thousand-legged worms are not true insects and should

BRANCH ARTHROPODA ; CLASS INSECTA: THE INSECTS 181

not be so miscalled. These last belong to the branch
Arthropoda but to other classes than the class Insecta.
While insects are found living under most diverse condi-
tions on land, that is, on the ground, in the leaves, fruits
and stems of plants, in the trunks of trees or in dead
wood, in the soil, in decaying animal or plant matter, as
parasites on or in other animals, and in all fresh-water
ponds and streams, they do not live in ocean water. A
few species live habitually on the surface of the ocean, and
a few other forms are found habitually on the water-
drenched rocks and seaweeds between tide lines. The
varied habits of insects, their economic relations with
man. the beauty and grace of many of them, and the
readiness with which they may be collected, reared and
studied, renders them unusually fit animals for the special
attention of beginning students of zoology. |

Body form and structure.—The segments composing
the body of an insect
are grouped to form
three body-regions, the
head, thorax, and abdo-
mich? the head of an
adult insect appears to
be a single segment or
body-ring, but in reality
itis composed of several
segments, probably
seven, completely fused.

The head bears the eyes,
antenne and the mouth- ww
- Fic. 45.—A wingless insect; the American
parts. The thorax is spring-tail, Lepidocyrtus americanus,
made up of three seg- common in dwelling-houses. The short
| line at the right indicates the natural
ments, each segment size, (From Marlatt. )
bearing a pair of legs.
From the dorsal side of the hinder two thoracic segments

182 ELEMENTARY ZOOLOGY

arise the two pairs of wings which are the most striking
structural features of insects. Not all insects are winged,
(fig. 45), and of those which are a few have only one pair
of wings, but the great majority of them have two pairs of
well-developed wings (fig. 46), which give them, as com-
pared with the other animals we have studied, a new and
most effective means of locomotion. The great numbers

<<
———

Ss
AF

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“i

Vg = \
= =
S =a
—

——————_

pet

aoe

Fic. 46.—A four-winged insect; a stone fly, Per/a sp., common about
brooks. (From Jenkins and Kellogg.)

of insects and their preponderance among living animals
is undoubtedly largely due to the advantage derived from
their power of flight. The hindmost part of the body,
the abdomen, is composed of from seven to eleven seg-
ments, only the last one or two of which are ever provided
with appendages. When such posterior abdominal
appendages are present they form egg-laying or stinging
or clasping organs. | |

BRANCH ARTHROPODA; CLASS INSECTA: THE INSECTS 183

The body-wall is usually firm and rigid, with thinner
flexible places between the segments and body-parts for
the sake of motion. The body-wall is composed of a
cellular skin or hypoderm, and an outer non-cellular
cuticle in which is deposited a horny substance called
chitin. This chitinous cuticle or exoskeleton serves as
an armor or protective covering for the soft body within,
and also as a point of attachment for the many muscles
of the body.

Insects vary a great deal in regard to shape and ap-
pearance of the body, and certain of the external organs
are greatly modified in different insects to adapt them to
the varied conditions under which they live. Especially
interesting and important are the variations in the char-
acter of the mouth-parts and wings, the organs of food-
getting and locomotion. In our consideration later of
some of the more important groups of insects the modifica-
tion of these parts will be specially referred to. Despite
the great number of insects, however, and their varied
habits of life, a strong uniformity of body-structure is
neticeagic. all of them holding pretty closely to the
typical body-plan.

The most interesting feature of the internal anatomy of
the insect body is the respiratory system. Insects breathe
through tiny paired openings, called spiracles, in the sides
of the abdominal (and sometimes the thoracic) segments
(the number and disposition of the pairs of spiracles varying
much in different insects). These spiracles are the external
openings of an elaborate system of air-tubes or trachee
(fig. 47) which ramify throughout the whole body and carry
air to all the organs and tissues. The blood has apparently
nothing to do with respiration as it has in the vertebrate
animals, where it carries oxygen to all the body tissues.

The other systems of organs are well developed and in
many respects more complex and elaborate than those of

184 ELEMENTARY ZOOLOGY

any of the other invertebrates. The muscular system
comprises a large number of distinct mus-
cles, usually small and short, which are
disposed so as to make very effective the

various complex motions of antenne,
mouth-parts, legs, wings, and egg-laying
organs. The museles appear to be
very delicate, being almost colorless
when fresh, but they have a high
contractile power. The alimen-
tary canal is di-
vided into various

special re-
C10ms, ais
pharynx, cesopha-
HIG, 47-—-bicte ot us, Chop, fore
trachea (air-tube) “ 1 . d
from the larva of >LOMACHN OF E1zzarad,

the giant-crane- digesting stomach,

fly. (Photo-micro- :

graph by Geo. 0. and small and large in-

Mitchell. ) testine. From the canal
just at the point of union of the digesting
stomach (ventriculus) and the small in- -
testine rise the so-called Malpighian
tubules, which sare excretory organs:
They are long slender diverticula of the
alimentary canal, and are typically six
(three pairs) in number. The circula- FI. eee ea
‘ : Na Of a Carrion bee-
tory system is composed of a tubular te with the termi-
vessel running longitudinally through the we aeeae ee
body in the median line just under the tened, and bearing
dorsal wall. It is composed of a series ote mls
of chambers or segmental parts, which _ thus serving as an
Be aoe ae f G a : olfactory organ,
y ythmic contraction and expansion (photo. micrograph
propel the blood anteriorly and into a_ byGeo.O.Mitchell.)

short, narrow, unsegmented anterior portion of the vessel

&

BRANCH ARTHROPODA; CLASS INSECTA: THE INSECTS 18s

wimiememay be called the aorta. There are no other
arteries or veins, the blood simply pouring out of the
anterior end of the dorsal vessel into the body-cavity. It
bathes the body tissues, flowing usually in regular channels
without walls. It re-enters the dorsal vessel through
paired Jateral openings in the chambers.

The main or central nervous system consists of a large
ganglion, the ‘‘brain,’’ situated in the head above the

Fic. 49.—A section through the compound eye (in late pupal stage) of the
blow-fly, Calliphora romitoria. In the centre is the brain, with optic
lobe, and on the right-hand margin are the many ommatidia in longi-
tudinal section. (Photo-micrograph by Geo. O. Mitchell.)

cesophagus, which sends nerves to the antenne and eyes,

a ganglion in the head below the cesophagus connected

with the brain by a short commissure on each side of

the cesophagus, and sending nerves to the mouth-parts;

and a ventral nerve-chain composed of a pair of longitudinal

186 | ELEMENTARY ZOOLOGY

commissures lying close together and running from the
head to the next to the last abdominal segment, which
bears a series of segmentally disposed ganglia, each
canglion being composed of two ganglia more or less
nearly completely fused. There is, in addition, a lesser
system called the sympathetic system, which comprises a
few small ganglia and certain nerves which run from
them to the viscera. The function of the nervous system
of insects reaches a very high development among the
so-called ‘‘intelligent insects’’ and certain extraordi-
narily complex and interesting instincts are possessed by
many forms. The social or communal habits of the ants,
bees, and wasps and the habits connected with the deposi-
tion of the eggs and the care of the young exhibited by
the digger. wasps and other inse€ts” are @l extreme
specialization. The organs of special sense are highly
specialized, the sense of smell (fig. 48) reaching in par-
| ticular a high degree of perfec-
tion. One of the compound eyes
(figs. 49 and 50) may contain as
many as 30,000 distinct eye-
elements or ommatidia, but the
sight is probably in no insect
very sharp or clear. Among
insects there are organs of hear-
ing of two principal kinds. In
Fic. 5o.__Part of cornea, saow. ON€ kind the organ tem ig. up
ing facets, of the compound the sound-waves is a group of
eye ofahorse-fly (Zherioplec- : ; ;
tes sp.). (Photo-micrograph Vibratile hairs usually situated on
by Geo. O. Mitchell.) the antenne, as is the case with
the mosquito; in the other kind, it is a stretched mem-
brane or tympanum such as is found in the fore leg of a
cricket or katydid or on the first abdominal segment of
the locust (fig. 51). |
The sexes are distinct in insects, and there is often a

BRANCH ARTHROPODA ; CLASS INSECTA: THE INSECTS 187

marked sex dimorphism; in numerous species the males
are winged while the females are wingless, and in a few
Saees this condition is. reversed. Where there is a
difference in size between male and female, the females

Fic. 51.—The auditory organ of a locust (AZe/anoplus sp.). The large clear
part in centre of the figure is the thin tympanum, with the auditory
vesicle (small black pear-shaped spot) and auditory ganglion (at left of
vesicle and connected with it by a nerve) on its inner surface. (Photo-
micrograph by Geo. O. Mitchell.)

are usually the larger. Fertilization of the egg takes
place in the body of the female and, strangely, this fertil-
ization is effected after the eggshell has been formed. In
aliuMseck coos there is a minute opening in one pole of
the eggshell called the micropyle through which the
sperm-cells enter. In a few cases the young-are born
alive, but such a viviparous condition is exceptional. In

188 ELEMENTARY ZOOLOGY

a few species, too, young are produced parthenogeneti-
cally, that is, are produced from unfertilized eggs. And
in the case of a few insect species male individuals are
not known. |
Development and life-history.—The young insect
when just hatched from the egg either resembles, except
for the absence of wings, its parent in general appearance
as in the case of the locust, or it may, as in the butterfly,
emerge in a form very unlike the parent. In the first

case the young has simply to grow, that is, to increase

Fic. 52.—The young (at left) and adult (at right) of the bed-bug, Acanthta
lectularta, a wingless insect with incomplete metamorphosis. (After

Riley.)

in size, to develop wings, and to make some other not
very obvious developmental changes in order to become
fully grown. But in the case of the butterfly, and
similarly in the case of all other insects as the flies,
beetles, bees e¢ a/., whose young hatch in a larval condi-
tion differing markedly from the adult, some radical and
striking developmental changes occur before maturity is
reached. Such insects are said. to wadersoe seomplete
metamorphosis in their development, while those insects
like the locusts, the sucking-bugs, white ants,-and others,

BRANCH ARTHROPODA ; CLASS INSECTA: THE INSECTS 189

the just hatched young of which resemble their parents,
are said to have an incomplete metamorphosis (fig. 52).
In the case of insects with complete metamorphosis,
the young hatches as an active grub or worm-like feeding
larva which increases in size, casting its skin or molting
several times in its growth. Finally after the last larval
molt (fig. 53) called pupation the insect appears in a

Fic. 53.—The larva of the violet tip butterfly, Polygonia interragationis,
making its last molt, 1.e. pupating. (Photograph from life.)

quiescent non-feeding stage called the pupa (fig. 54), and
encased in an extra thick and firm chitinous exoskeleton.
The immovable pupa is sometimes concealed underground,
- sometimes enclosed in a silken cocoon spun by the larva
just before pupation, or is in some other way specially
protected -t is in this pupal condition that-the great
changes from wingless, often legless, worm-like larva to

190 ELEMENTARY ZOOLOGY

winged, six-legged, graceful imago of adult stage are
completed, and with the molting of the chitinous pupal
cuticle the metamorphosis or development of the insect
is completed. Asa matter of fact many of the special
organs of the adult, the legs and wings, for example,
begin to develop as little buds or groups of. cells in the
body of the larva, and when the larva is ready to pupate

Fic, 54.—Chrysalid (pupa) of the violet tip butterfly, Polygonia interraga-
tionts. From this chrysalid issues the full fledged butterfly. (Photo-
graph from life.)

these imaginal wings and legs are drawn out to the

external surface of the body, and may be readily recog-

nized as they lie on the ventral surface of the pupa folded
and closely pressed to the body surface. In recent years
the study of the post-embryonic development of insects
with complete metamorphosis has revealed some re-
markable changes of the internal organs which result in
a nearly complete disintegration or breaking down of

Beane ARTHROPODA ; CLASS INSECTA: THE INSECTS 191

most of the internal organs of the larva (fig. 55) and a
rebuilding of the organs of the adult from primitive be-
ginnings.

The habits of the larve of insects with complete meta-
morphosis and of the young of some insects with incom-
plete metamorphosis often differ markedly from the

oe

Fic. 55.—A cross-section of the body of the pupa of a honey-bee, showing
the body cavity filled with disintegrated tissues, and (at the bottom) a

budding pair of legs of the adult, the larva being wholly legless.

(Photo-micrograph by Geo. O. Mitchell. )

habits of the adults, and as the habits and instincts of
insects are remarkably specialized, the study of their be-
havior and of the structural and physiological modifica-
tion which their varied habits of life have brought about
is of much interest and significance. In later paragraphs
this phase of insect study will be again referred to.
Classification.— Much attention has been paid to the
classification of insects and the 300,000 (approximately)
known species have been variously grouped together into
orders by different entomologists. A subdivision of the
class Insecta into five orders was proposed by Linn-eus
about 1750 and was used until comparatively recently.
Since then, however, numerous other arrangements have
been proposed, all of them agreeing in increasing the

ye ELEMENTARY ZOOLOGY

number of orders by breaking up some of the old ones
into two or more new ones. The classification adopted
in the text-book* of zoology which we have made our
reference in classification is an 8-order system. The
latest Englisht text-book in entomology adopts a
g-order system, while the principal American ¢ text-book
on this subject divides the insects into nineteen orders.

The classification depends chiefly on the character of
the post-embryonic development, that is, on whether the
metamorphosis is complete or incomplete, and on the
structural character of the mouth-parts and wings. In
the following paragraphs a few of the larger insect orders,
with some special representatives of each, will be briefly
considered. |

The best American text-book of the classification and
habits of insects is Comstocks’ ‘*Manual-of Imseets.
For an account of the structure of the wings and mouth-
parts of various insects see Comstock and Kellogg’s
‘SEiements or brsect -wmatomy—-

Orthoptera: the locusts, cockroaches, crickets, katy-

dids, etc.— TEecunicaL. NoTE.—Obtain specimens of crickets or
katydids, and cockroaches, and compare the external body struc-
ture with that of the grasshopper; examine especially the wings,
mouth-parts, legs, and egg-laying organs. Note that the hindmost
legs of the cockroach are not fitted for leaping but for running. Note
the sound-making (stridulating) organs on the bases of the fore wings
of the male katydids and crickets. Note the auditory organs (tym-
pana) in the fore tibia of the katydids and crickets. Crickets can
be easily kept alive in breeding-cages in the laboratory and their
feeding habits and much of their life-history observed. The growth
of the young and the development of the wings can be noted, and
will be found to be essentially similar to the conditions already
found in the case of the locust.

The locust studied as one of the examples of the class
Insecta belongs to the order Orthoptera, which also in-
* A Text-book of Zoology, Parker & Haswell, 1897. |

+ The Cambridge Natural History, vol. V, 1895, vol. VI, 1899.
{ A Manual for the Study of Insects, J. H. and A. B. Comstock, 13897.

BRaNCH ARTHROP@QDA; CLASS INSECTA: THE INSECTS 293

cludes the cockroaches, crickets (fig. 56), katydids and
green grasshoppers, the walking-stick or twig insects, the
praying mantis and _ others.
The members of this order all
have an incomplete metamor-
phosis, and in all the mouth-
parts are fitted for biting and
the fore wings are more or
less thickened and modified to
serve aS covers or protecting
organs for the broad, plaited, -
membranous hind wings, which ° ; JW 4 4
are the true flight organs. The a ae ae
hind legs of locusts, grasshop- Fic. 56.—The house cricket,

pers, crickets, and katydids are ie ee ee

very large, and enable the in-

sects to leap; the legs of the cockroaches are fitted for
swift running; the fore legs of the praying mantis are
fitted for grasping other insects which serve as their food,
and the legs of the walking-stick (fig. 162) are long and
slender and fitted for slow walking. The shrill singing of
the crickets and katydids and the loud ‘‘clacking’’ of
the locusts are all made by stridulation, that is, by
rubbing two roughened parts of the body together. The
sounds of insects are not made by vocal cords in the
throat. The male crickets and katydids (for only the
males sing) have the veins of the fore wings modified so
that when the bases of the wings are rubbed together
(and when the cricket or katydid is at rest the base of
one fore wing overlaps the base of the other) a part of
one wing called the ‘‘scraper’’ rubs against a part of the
other called the ‘‘file’’ and the shrilling is produced.
The sounds of locusts are produced by the rubbing of
the inside of the hind leg against the outside of the fore
wing when the insect is at rest, or by striking the front

194 ELEMENTARY ZOOLOGY--

margin of each hind wing against the hind margin of each
fore wing when the locust is flying. For hearing the
Orthoptera are provided with auditory organs having the
character .of tympana or vibrating membranes. In the
locusts these ‘ears (fig. 51) are situated on the dorsal
surface of the first abdominal segment; in the katydids
and crickets they are im the tibiae
of the fore legs, ) Pitestoed of
locusts, crickets, and katydids is
vegetable, being usually green
leaves; the cockroaches eat either
plant or animal substances fresh
or dry, while the praying mantis
is predaceous, feeding on other
insects .which ‘#eatches “in cats
strong grasping: fore leesme ble
walking-stick or twig insect is an
excellent example of what is called
‘‘ protective resemblance ’’ among

animals. Indeed -most “om the
Hie. 57:~* bird louse, W7- Orthoptera alc emmalageameesn

mus prestans, from a tern,

Sternamaxima. Most birds” patterned as to be almost indistin-
are infested with small,
wingless, biting insects,
called bird-lice, which are ing- or feeding-grounds. Some
external parasites feeding

on the feathers of the bird of the tropical Orthoptera Carry
host. The bird louse to a marvelous degree this modi-
figured is about ;/, in. long. : 2 :

(Photo-micrograph by Geo. fication for the sake of protection.
ee liven (In this connection read Chapter

XX XI” referring to ‘* Protective Kesempinteeaae:

cuishable when on their usual rest-

Odonata and Ephemerida: the dragon-flies and May-

flies.— TrEcHNICAL NOTE.—Obtain specimens of adult and imma-
ture dragon-flies. The young dragon-flies (fig. 59) may be got by
raking out some of the slime and aquatic vegetation from the bottom
of asmall pond. Compare the external structure of the adult dragon-
flies with that of the grasshopper; note the large eyes, the narrow
nerve-veined wings, the biting mouth-parts, and the short antenne.

Beane ARTHROPODA ; CLASS INSECTA: THE INSECTS 1495

Compare the young dragon-flies with the adults; note the devel-
oping wings and the peculiar modification of the lower lip into a
protrusible, grasping organ which when at rest is folded like a mask
over the face. _Examine the interior of the. posterior. part of the
alimentary canal to find the rectal gills. Obtain specimens of adult
and young May-flies. The young may be found on the under side
of stones in a ‘‘riffle” in almost any stream. They live also in ponds.
They may be recognized by reference to fig. 61. Compare adult
May-flies with the dragon-flies ; note the weakly chitinized, delicate
body-wall, and the difference in size between fore and hind wings ;
note the biting mouth-parts of the young and their absence or
presence in vestigial condition only in the adults.

The young of both dragon-flies and May-flies may easily be kept
alive in the laboratory aquarium (fruit-jars or battery-jars with pond
water in), and their feeding habits, their swimming, their respiration,
and much of their development observed. The young May-flies
should be got from ponds, not running streams. Put one ot these
semi-transparent May-fly nymphs into a watch-glass of water, and
examine under the microscope. The movements of the gills, heart,
and alimentary canal, and much of the anatomy can be readily made
out. The emergence of the adult from the nymphal skin can be
seen if close watch is kept. The young dragon-flies may be seen to
capture and devour their prey. They may also transform into adults,
but for this it. will be necessary to obtain nymphs nearly ready for
transformation.

Among the most familiar and interesting insects are the
dragon-flies (fig. 58), sometimes called ‘‘ devil's darning-
needles.’’ They are commonly seen flying swiftly about
over ponds or streams catching other flying insects. The
dragon-flies are the insect-hawks; they are predaceous and
very voracious, and are probably the most expert flyers
of all insects. There are many species, and their bright
iridescent colors and striking wing-patterns make them
very beautiful. The young dragon-flies (fig. 59) are
aquatic, living in streams and ponds, where they feed
om tie other aquatic insects in their neighborhood.
@irey catch thei prey by lying-in wait until an insect
comes close enough to be reached by the extraordi-
narily developed protrusible grasping lower lip (fig. 60).
When at rest this lower lip lies folded on the face so as
to conceal the great jaws. The young dragon-flies breathe

196 ELEMENTARY ZOOLOGY

by means of gills which do not project from the outside
of the body, as do the gills of other aquatic insects, but
line the inner wall of the posterior or rectal part of the

CS Lag

Fic. 538. aK cineon i Take ‘um FIG. 59.-—The young fale is of the
tllotum, common in California. dragon-fly, Sympetrum tllotum.
(From life. ) (From Jenkins and Kellogg.)

alimentary canal. Water enters the canal through the
anal opening and bathes these gills, bringing oxygen to
them and taking away carbonic acid gas. The aquatic

Fic. 60.—Young (nymph) dragon-fly, showing lower lip folded and ex-
tended. (From Jenkins and Kellogg.)

immature life of the dragon-flies lasts from a few months
to two years. When ready to change to adult, the young
crawls out of the water and clinging to a rock or plant
makes its last molt.

Bereaved ARTHROPODA ; CLASS INSECTA): THE INSECTS 197

Other abundant and interesting pond and brook insects
are the May-flies. The young May-flies (fig. 61) are
aquatic, living in streams and
ponds and feeding on minute
organisms such as diatoms and

oemdee. The immature life 5 :
lasts a year, or even two or three \ G10 l
in some species, and then the SS
May-fly crawls out of the water ae
upon a plant-stem or projecting & ee NN

rock and, molting, appears as the
winged adult. The adult May-
fly, having its mouth-parts atro-
phied (a few May-flies have func-
tional mouth-parts),takes no food,
and lives only a few hours or at
most perhaps a few days. It has
the shortest life (in adult stage)
of all insects. The female drops
her eggs into the water. ec Neg a a

Hemiptera: the sucking-bugs. heal gills. (From Jenkins

—TECHNICAL NOTE.—Obtain speci- es

mens of water-striders (narrow elongate-bodied insects with long
spider-like legs which run quickly about on the surface of ponds
or quiet pools in streams), water-boatmen (mottled grayish insects
about half an inch long which swim and dive about in ponds and
stream-pools), back-swimmers (which are usually in company with
the water-boatmen, but which swim with back downwards and
are marked with purplish-black and creamy white patches), cicadas
(the dog-day locusts), and plant-lice (the “ green fly ” of rose-bushes
and other cultivated plants). Compare the external structure of
some of these Hemiptera with the other insects already examined ;
note especially the sucking beak, composed of the elongate tube-
like labium in which lie the greatly modified flexible needle-like
maxilla and mandibles, the whole forming an equipment for pierc-
ing and sucking. Obtain immature specimens of some of these
insects (distinguished by their smaller size and the wing-pads) ; note
that the metamorphosis is incomplete, the young resembling the
parents in general appearance. Both immature and adult specimens
of water-boatmen(Corvzsa), back-swimmers (/Vofonecta), and water- _

198 ELEMENTARY ZOOLOGY

striders (//ygrotrechus) can be easily kept in the laboratory aquaria-
and their swimming, breathing, and feeding habits observed. Note
especially the carrying of air down beneath the water.

The Hemiptera are characterized particularly by their
highly specialized sucking mouth-parts, no other of the
sucking insects having the proboscis composed in the

Fic. 62.—The female red orange scale Fic. 63.—The female rose-
insect, Aspidiotus aurantit, very injuri- scale, Diaspis rose, a
ous to orange-trees. It has no wings, pest of rose-bushes, with-
legs, nor eyes, but remains motionless out eyes, wings, or legs,
on a leaf, stem, or fruit, holding fast by but with slender sucking
its long slender beak, through which it proboscis. The male is
sucks up the plant-sap. The male is winged and_ without
winged, and has no mouth-parts, taking mouth-parts, (Photo-mi-
no food. (Photo-micrograph by Geo. crograph by Geo. O.
O. Mitchell.) : Mitchell.)

same manner. The palpi of both maxillz and labium
are wholly wanting in Hemiptera and the flexible needle-
like maxilla and mandibles are enclosed in the tubular
labium. This order is a large one and includes many
well-known injurious species, as the chinch-bug (Lizssus
leucopterus), which occurs in immense numbers in the
grain-fields of the Mississippi valley, sucking the juices
from the leaves of corn and wheat, the grape Phylloxera
(Phylloxera vastatrix), so destructive to the vines of
Europe and California, the scale insects (Cocczd@) (figs.

BRANCH ARTHROPODA ; CLASS INSECTA: THE INSECTS 199

62 and 63), the worst insect pests of oranges, the squash-
bugs and cabbage-bug and a host of others. Some of
the Hemiptera, for example, the lice and bed-bugs, are
predaceous, sucking the blood of other animals.

The water-striders (fig. 64) catch other insects, both
those that live inthe water
and those which fall on to
its surface,andholding the
prey with their seizing
fore legs they pierce its
body with their. sharp
beak and suck its blood.
They lay their eggs in the
spring glued fast to water-
plants. The young water-
striders are shorter and
stouter in shape than the
adults.

The water-boatmen Fic. 64.—A water-strider, Mygrotrechus

f . sp. (From Jenkins and Kellogg. )

(ig. 65) and back-swim-

mers swim and dive about in the water, coming more
or less frequently to the surface to get a supply of air.
This air they hold under the
wings, or on the sides and
under part of the body en-
tangled in the fine hairs on
the surface. +he--imsects
appear to have silvery spots
on the body, due to —the
presence of-thise air. 7, he
Fic. 65.—A water-boatman, Cortsa ‘* rowing is legs of the water-
sp. (From Jenkins and Kellogg.) Eat aes (Corsa) ee ae
hindmost pair; in the back-swimmers (/Votonecta) they
are the middle legs.

The cicadas (fig. 66) are the familiar insects of summer

200 ELEMENTARY ZOOLOGY

which sing so shrilly from the trees, the seventeen-year
cicada (Cicada septendecim) (oftentimes called locust)
3 . being the best known of
y “¢ this family. Its eggs
are laid in slits cut by
the female in live twigs.
The young, which hatch
in about six weeks, do
not feed. on the green
foliage, but fall to the
ground, burrow down to
the roots of the tree and
there live, sucking the
juices from the roots, for
Fic. 66.—The seventeen-year cicada, Ci- sixteen years and ten or
cada septendecim ; the specimen at left
showing sound-making organ, v. ~., ven- eleven months. When
tral plate; ¢, tympanum. (From speci- about to become adult,
ae the young cicada.crawls
up out of the ground and clinging to the tree-trunk molts
for the last time, and flies to the tree-tops.

The plant-lice (Aphidide@) are small soft-bodied
Hemiptera which have both winged and wingless indi-
viduals. In the early spring a wingless female hatches
from an egg which, laid in the preceding fall, has passed
the winter in slow development. This wingless female,
called the stem-mother, lays unfertilized eggs or more
often perhaps gives birth to live young, all of which are
similarly wingless females which reproduce partheno-
genetically. This reproduction goes on so rapidly that
the plant-lice become overcrowded on the food-plant and
then a generation of winged * individuals is produced from

* It has been shown by experiment that the winged individuals, which are
able to leave the old food-plant and scatter over new plants, do not appear
until the feod-supply begins to run short. At the insectary of Cornell Uni-
versity ninety-four successive generations of wingless individuals were bred,

BRANCH ARTHROPODA ; CLASS INSECTA: THE INSECTS 201

time to time. These winged plant-lice fly away to new
plants. In the autumn a generation of males and females
is produced; these individuals mate and each female lays
a single large egg which goes over the winter, and pro-
duces in the spring the wingless agamic stem-mother,
Plant-lice produce honey-dew, a sweetish substance much
liked by ants, and the lice are often visited, and sometimes
specially cared for, by the ants for the sake of this honey-
dew. Smallas they are, plant-lice occur in such numbers
as to do great damage to the plants on which they feed.
The apple-aphis, cherry-aphis, pear-aphis, cabbage-aphis
and others are well-known pests. The most notoriously
destructive plant-louse is the grape Phylloxera, which
lives on the roots and leaves of the grape-vine. Im-
mense losses have been caused by this pest, especially in
the wine-producing countries of southern Europe.

Diptera: the flies.—TecunicaLt Norr.—Obtain specimens
of the adult and young stages of the blowfly and the mosquito. All
the young stages of the blowfly may be obtained, and its life-history
studied, by exposing a piece of meat to decay in an open glass jar.
The larve of the mosquito are the familiar wrigglers of puddles
and ponds, and by collecting some of them and keeping them in a
glass jar of water covered with a bit of mosquito-netting, the life-
history of the mosquito is easily studied. If the eggs can be ob-
tained from the pond so much the better; they are in little black
masses floating on the surface of the water, and resemble at first
glance nothing so much as a floating bit of soot. The external
structure of the adult flies should be compared with that of the
other insects studied, noting especially the condition of mouth-parts
and wings, and the substitution of balancers for the hind wings.
The mouth-parts of the mosquito are in the form of a long proboscis
composed of six slender needle-like stylets lying in a tube narrowly
open along its dorsal surface. The tube is the labium, and the
Stylets are the two maxilla, two mandibles, and two other parts
known as the epipharynx and the hypopharynx. Two additional
thicker elongate segmented processes lying outside of and parallel
with the tube are the maxillary palpi. The male mosquito (distin-
guished from the female by the more hairy or bushier antenne) lacks

by taking care to provide a constantly abundant supply of food. This ex:
periment was continued for more than four years.

202 ELEMENTARY ZOOLOGY

the pair of needle-like mandibles. The mouth-parts of the blowfly
are composed almost exclusively of the thick fleshy proboscis-like
labium, which is expanded at the tip to form a rasping organ

The Diptera or true flies are readily distinguishable
from other insects by their having a single pair of wings.
instead of two pairs, the hind wings being. transformed
into small knob-headed pedicels called balancers or
halteres. The flies undergo complete metamorphosis,
and their mouth-parts are fitted for piercing and sucking
(as in the mosquito) or for rasping and lapping (as in the
blowfly). Nearly 50,000 species of flies are known, more
than 4,000 being known in North America alone.

The blowfly (Calliphora vomitoria) is common in
houses, but can be distinguished from the house-fly by its
larger size and its steel-blue abdomen. It lays its eggs
on decaying meat (or other organic matter) and the white
footless larve (maggots) hatch in about twenty-four |
hours. They feed voraciously and become full grown in
a few days. They then change into pupz which are
brown and seed-like, being completely enclosed in a uni-
form chitinized case which wholly conceals the form of the
developing fly. The house-fly has a life-history and im-
mature stages like the blowfly, but its eggs are deposited
on manure.

The mosquito (Culex sp.) (fig. 67) lays its eggs in a
sooty-black little boat-shaped mass which floats lightly on
the surface ofthe -~water.. Ina few days) the jai-- of
‘‘wrigglers,’’ issue and swim about vigorously by bend-
ing the body. The head end of the body is much broader
than the other, the thoracic segments being markedly
larger than the abdominal ones. ‘The head bears a pair
of vibrating tufts of hairs, which set up currents of air that
bring microscopic organic particles in the water into the
wriggler’s mouth. At the posterior tip of the body are
two projections, one the breathing-tube (the wriggler

BRANCH ARTHROPODA; CLASS INSECTA: THE INSECTS 293

coming often to the surface to breathe), and the other
the real tip of the abdomen. The wriggler, although
heavier than water, can hang suspended from the surface
film by the tip of its breathing-tube. It changes in a few

larve (long and slender, in water), pupa (large headed, at surface),
and adult (in air). (From living specimens. )

days into the pupa, which, instead of being quiescent as
with most flies, can swim about. It has a large bulbous
head end and the posterior end of the body bears a pair
of swimming-flaps. It takes no food. When ready to

204 ELEMENTARY ZOOLOGY

_ change to the adult mosquito the pupa (which, unlike the
wriggler, is lighter than water) floats at the surface of the
water, back uppermost. The chitinous cuticle splits
along the back and the delicate mosquito comes out, rests

Fic. 68.—The house-flea, Pulex trritans; a, larva; 6, pupa; c, adult.
(The fleas are probably more nearly related to the Diptera than to any
other order of insects. (After Beneden.)

on the floating pupal skin until its wings are dry, and
then flies away. Only the female mosquitoes suck blood.
If they cannot find animals, mosquitoes live on the juices
of plants. They are world-wide in their distribution,
being serious pests even in Arctic regions, where they are
often intolerably numerous and greedy. Recent investi-
gations have shown that the germs which cause malaria
in man live also in the bodies of mosquitoes, and are in-
troduced into the blood cf human beings by the biting

PRANCH ARTHROPODA; CLASS: INSECTA: THE INSECTS 205

(piercing) of the mosquitoes. It is probable also that the
germs of yellow fever are distributed by mosquitoes in the
same way. By pouring a little kerosene on the surface
of a puddle no mosquitoes will be able to escape from
the water.

Lepidoptera: the moths and butterflies.—Trcunicar
NOTE.—Obtain specimens of a few moths, and compare with the
butterfly already studied ; note especialiy the character of antenne.
Obtain miscellaneous specimens of larve, pupz, and cocoons of any
moths or butterflies. Note the variety in colors, markings, and
skin coverings of the larve; note the shape and markings of the
pupe. Rear trom eggs, larvae, or pupe in breeding-cages any
moths and butterflies obtainable (for directions for rearing moths
and butterflies see Chapter XXXIV), keeping note of the times of
molting and of the duration of the various immature stages. If
the eggs of silkworms can be obtained the whole life cycle of the
silkworm moth can be observed in the schoolroom. The larve
(worms) feed on mulberry or osage orange leaves, feeding vora-
ciously, growing rapidly and making no attempts to escape. The
molting of the larve can be observed, the spinning of the silken
cocoon, and the final. emergence of the moth. The moths after
emergence will not fly away, but if put on a bit of cloth will mate,
and lay their eggs on it. From these eggs, which should be kept
well aired and dry, larve will hatch in nine or ten months (if the
race is an “annual ”).

The Lepidoptera (figs. 69-74) include all those insects
familiarly known to us as moths and butterflies; they are
characterized by their scale-covered wings (fig. 69) and
long nectar-sucking proboscis composed of the two inter-
locking maxille. They undergo a complete metamorpho-
sis (fig. 70) and their larve are the familiar caterpillars of
garden and field. These larve have biting mouth-parts
and feed on vegetation, some of them being very injurious,
for example the army-worms, cut-worms, codlin moth
worms, etc. The adult moths and butterflies take only
liquid food, or no food at all, and are wholly harmless to
vegetation. The structure and life-history of a butterfly
has already been studied, and in the more general condi-

206 ELEMENTARY ZOOLOGY

tions of structure and life-history there is much similarity
in the many insects of this order. The eggs are usually
laid on the food-plant of the larva; the larva feeds on the

Fic. 69.—A small, partly denuded part, much magnified, of a wing of a
‘‘blue’”’ butterfly, Zycena sp., showing the wing,scales and the pits in
the wing-membrane, in which the tiny stems of the scales are inserted.
(Photo-micrograph by Geo, O. Mitchell. )

leaves of this plant, grows, molts several times, and
pupates either in the ground or in a silken cocoon or
simply attached to a: branch or Jeaf.’ Pheresasc ibout
six thousand species of moths and_ butterflies known
in North America, and they are our most beautiful in-
Sects. |

Coleoptera: the beetles.—TecunicaL NoTE.— Obtain
specimens of various beetles, among them some water-beetles and
June-beetles with their young stages, if possible; if not, then the
young stages and adults of any beetle common in the neighborhood
of the school. Of the swimming and diving water-beetles there are
three families, viz., the Gyrinidz or whirligig beetles, with four eyes
(each compound eye divided in two), the Hydrophilide, or water-
scavengers with two eyes and antenne with the terminal segments

BRANCH ARTHROPODA; CLASS INSECTA: THE INSECTS 207

thicker than the others, and the Dytiscide or predaceous water-
beetles with two eyes and slender thread-like antennae. Try to
find Dytiscidz, large, oval, shining black beetles ; the larve are
called water-tigers and are long, slim, active creatures with six legs

Fic. 70.—The forest tent-caterpillar moth, CZstocampa disstria, in its
various stages; mz, male moth; /, female moth; /, pupa; ¢, eggs (in a
ring) recently laid; g, eggs hatched; ¢, larva or caterpiliar. Moths
and caterpillar are natural size, eggs and pupa slightly enlarged.
(Photograph by M. V. Slingerland.)

and slender curving jaws (see fig. 76). The June-beetles are the
heavy brown buzzing ‘ June-bugs” and their larve are the common
“white grubs” found underground in lawns and pastures. Have
live water-tigers and predaceous water-beetles in the aquarium.
Note their feeding and breathing. Compare the external structure
of the beetles with that of the other insects, noting especially the
biting mouth-parts, and their thickened horny fore wings serving
as covers for the folded membranous hind wings.

208 ELEMENTARY ZOOLOGY

The Coleoptera is the largest insect order, probably
100,000 species of beetles being known, of which 10,000

Fic. 71.—A trio of apple tent-caterpillars, Cistocampa americana, natural

oh IS

size. These caterpillars make the large unsightly webs or *‘ tents © in
apple-trees, a colony of the caterpillars living ineach tent. (Photograph
from life by M. V. Slingerland.)

species are found in North America. They pass through
a complete metamorphosis (figs. 75 and 76), the larve of
the various kinds showing much variety in form and habit.

ean Gd: ARTHROPODA; CLASS: INSECTA: THE. INSECTS, 299

The pupz are quiescent and are mummy-like in appear-
ance, the legs and wings being folded and pressed to the
ventral surface of the body. Among the familiar beetles
are the lady-birds, which are beneficial insects feeding on
plant-lice and other noxious forms; the beautifully colored

Fic. 72..-A family of forest tent-caterpillars (C’@stocampa disstria , resting
during the day on the bark, about one-third natural size. (Photograph
from lite by M. V. Siingerland.)

tiger-beetles, predaceous in habit; the ‘‘tumblebugs ’’ and
carrion beetles, which feed on decaying organic matter;
the luminous fire-flies with their phosphorescent organs
on the ventral part of the abdomen; the striped Colorado
potato-beetle and the cucumber-beetles and numerous
other destructive leaf-eating kinds; the various weevils

ZO ELEMENTARY . ZOOLOGY

(ig. 78) that bore into fruits, nuts and grains, and the
many wood-boring beetles, destructive to fruit-trees as
well as to shade- and forest-trees. |

The predaceous water-beetles (Dytzcus sp.) are common
in ponds and quiet pools in streams. When at rest they
hang head downward with the tip of the abdomen just
projecting from the water. Air is taken under the tips of

Itc. 73 — Moths of the peach-tree borer, Savztnoidea exttiosa, natural size;
the upper one and the one at the right are females. (Photograph by
Me Wo Slingerland.)

the folded wing-covers (elytra) and accumulates so that
it can be breathed while the beetle swims and feeds under
water. When the air becomes impure the beetle rises to
the surface, forces it out, and accumulates a fresh supply.
The beetles are very voracious, feeding on other insects,
and even onsmall fish. The eggs are laid promiscuously in
the water, and the elongate spindle-form larve (fig. 77)

Army-worms, larve of the moth, Leucania unipuncta, on corn,
(Photograph by M. V. Slingerland.)

|i Conger fa

212 ELEMENTARY ZOOLOGY

called water-tigers are also predaceous. They suck the
blood from other insects through their sharp-pointed
sickle-shaped hollow
mandibles. When a larva
is fully grown it leaves
the “water,” burrows in
the ground, and makes a
round cell within which it
undergoes its transforma-
tions., “The “pupa state
lasts about three weeks
in summer, but the larve
that transform in autumn
remain in the pupa state
all winter.

The June-beetles (June-
bugs) (Lachnosterna sp.)
feed on >the telace of
trees. » | Them eaes are

Fic. 75.—-The quince-curculio (a beetle), j
Conotrachelus crategi, natural size and laid among the roots of
enlarged. @ (Phoweraph “by WE ON

Slingerland. ) grass 1n little hollow balls

of earth, and the fat slug-
eish white larve feed on the grass-roots. They some-
times occur in such numbers as to injure seriously lawns
and meadows. The larve live three years (probably)
before pupating. They pupate underground in an earthen
cell, from which the adult beetle crawls out and flies up
to the tree-tops.

5, Hymenoptera : the ichneumon flies, ants, wasps, and

bees.—TeEcHNIcCAL NotTE.—Obtain specimens of wasps, both
social (distinguished by having each wing folded longitudinally) and
solitary (wings not folded longitudinally), and if possible of both
queens (larger) and workers (smaller) of the social kinds; of ants
both winged (males or females) and wingless (workers) individ-
uals; also of honey-bees, including a queen, drones, and workers,
and some brood comb containing eggs, larva, and pupe. The bee

BRANCH ARTHROPODA; CLASS INSECTA: THE INSECTS 213

specimens can be got of a bee raiser. Compare the external struc-
ture of ants, bees, and wasps with that of other insects ; note the
pronounced division of the body into three regions (head, thorax,
abdomen) ; note the character of the mouth-parts having mandibles
fitted for biting (ants and wasps) or moulding wax (honey-bees) and
having the other parts adapted for taking both solid and liquid
food ; note the sting (possessed by the females and workers only).
Observe the behavior of bees in and about a hive; note the coming
and going of workers for food. Observe bees collecting pollen at
flowers ; observe them drinking nectar. Examine the honey-bee

Fic. 76.—Immature stages of the quince curculio, Conotrachelus crategi;
at the left, the larva natural size and enlarged; at the right, the pupa.
The beetle lays its eggs in pits on quinces, and the larva lives inside
the quince as a grub; the pupa lives in the ground. (Photograph by
M. V. Slingerland.)

in its various stages, egg, larva, pupa, adult. Note the special
structure of the adult worker fitting it to perform its various special
labors; the pollen-baskets on the hind legs; the wax-plates on the
ventral surface of the abdomen, the wax-shears between tibia and
tarsus of hind legs; the antenne-cleaners on the fore legs; the
hooks on front margin of hind wings, etc.

The Hymenoptera include the familiar ants, bees, and
wasps, and also a host of other four-winged, mostly
small, insects, many of which are parasites in their larval
stage on other insects. All Hymenoptera have a com-

2 TA ELEMENTARY ZOOLOGY

plete metamorphosis, and their habits and instincts are,
asa rule, very highly specialized. The parasitic Hymen-

Fic. 77.—Water-tiger, the
Jarva of the predaceous
water-beetle, Dytzcus sp.
(From specimen. )

optera such as the ichneumon flies,
chalcid flies, etc., are stingless but
have usually a piercing ovipositor
(the sting being only a modified
ovipositor). The general life-history
of these ichneumons is as follows:
the female ichneumon fly, finding
one of the caterpillars or fly or beetle
larvze which 1s tts Nest, sees om at
and either lays an egg or several
eggs on it,.of thrustime tate .ovi-
positor, lays the eses im the- weary.
the young ichneumon hatching as
a grub burrows into the body of its
caterpillar host, feeding on the body -
tissues, but not attacking the heart
or nervous system, so that the host
is not soon killed; the ichneumon
pupates. either inside thewie+t = or

crawls out and, spinning a little silken cocoon (fig. 160),
pupates on the surface of the

body or elsewhere.

Some of the stingless Hymen-
optera are not parasites, but are
gall-producers. The female with
its piercing ovipositor lays an

egg in the soft tissue of a leaf or Fic. 78.—The plum curculio,

Stem, and aiter the larva hatches

Conotrachelus nenuphar, a
beetle very injurious to plums.

the gall rapidly.forms... The — (Photograph by Mey solm-

larval insect lies in the plant-

land. )

tissue, having for food the sap which comes to the rapidly
erowing gall. It pupates in the gall, and when adult

eats its way out.

The ants, bees, and wasps are called the stinging
Hymenoptera, although the ants we have in North
America have their sting so reduced as to be no longer
Meagies) Among these Hymenoptera are the social or
communal insects, viz., all the ants, the bumblebees and
honey-bee, and the few social wasps, as the yellow-jacket

Fic. 79.—The currant-stem girdler, Yanus integer, a Hymenopteron at
work girdling a stem after having deposited an egg in the stem half an
inch lower down. (Photograph by M. V. Slingerland.)

and black hornet. There are many more species of non-
social or solitary bees and wasps than social ones, and
their habits and instincts are nearly as remarkable.

The solitary and digger wasps do not live in com-
munities as the hornets do, but each female makes a nest
or several nests of her own, lays eggs and provides for

216 ELEMENTARY ZOOLOGY

her own young. The nest is usually a short vertical or
inclined burrow in the ground, with the bottom enlarged
to form a cell or chamber. In this chamber a single egg
is laid, and some insects or spiders, captured and so stung
by the wasps as to be paralyzed but not killed, are put in
for food. The nest is then- closéd” up by the female,
and the larva hatching from the egg feeds on the enclosed
helpless insects until full grown, when it pupates in the cell
and the issuing adult gnaws and pushes its way out of the
ground. Each species of wasp has habits peculiar to itself,
making always the same kind of nest, and providing
always the same kind of food. Some of these wasps make
their nests in twigs of various plants, especially those with
pithy centres in the stems. [or interesting accounts of
the habits of several digger wasps see Peckham’s ‘‘ The
Solitary Wasps. ’’

The solitary bees, of which there are similarly many
kinds, are like the solitary wasps in general habit, only
they provision the nest with a mixture of pollen and nectar
got from flowers instead of with stung insects. Some-
times many individuals of a single species of solitary bee
will make their nests near together and thus form a sort
of community in which, however, each member has its
own nest and rears its own young. In the case of certain
small mining bees of the genus //a/ictus, a step farther
toward true communal life is taken by the common build-
ing and use by several females of a single vertical tunnel
or burrow from which each female makes an individual
lateral tunnel, at the end of which is a brood-chamber.
Perhaps half a dozen females will thus live together, each
independent except for the common use of the vertical
tunnel and exit:

The bumblebees (Lomdbus sp.) are truly communal in
habit. All the eggs are laid by a queen omtermewtemale,
which is the only member of the colony to live through

BRANCH ARTHROPODA; CLASS INSECTA: THE INSECTS 217

the winter. In the spring she finds a deserted mouse’s
nest or other hole in the ground, gathers a mass of pollen
and lays some eggs on it. The larve, hatching, feed on
the pollen, dig out irregular cells for themselves in it,
pupate, and soon issue as workers, or infertile females.
These workers gather more pollen, the queen lays more
eggs, and several successive broods of workers are pro-
duced. Finally late in the summer a brood containing
males (drones) and fertile females (queens) is produced,
mating takes place, and then before winter all the workers
and drones and some of the queens die, leaving a few
fertilized queens to hibernate and establish new communi-
ties in the spring.

The yellow-jackets and hornets (Vespide), the so-
called social wasps, have a life-history very like that of
the bumblebees. The communities of the social wasps
are larger and their nests are often made above ground,
being composed of several combs one above the other
and all enclosed in a many-layered covering sac open
only by a small hole at the bottom. This kind of nest
hangs from the branch of a tree and is built of wasp-paper,
which is a pulp made from bits of old wood chewed
by the workers. The brood-cells are provisioned with
killed and chewed insects, the larve of both solitary and
social wasps being given animal food, while the larve
of both solitary and social bees are fed flower-pollen and
honey. As in the bumblebees, all the members of the
community except a few fertilized females die in the
autumn, the surviving queens founding new colonies in
the spring. The queen builds a miniature ‘‘hornet’s
nest ’’ in the spring, lays an egg in each cell and stores
the cells with chewed insects. The first brood is com-
posed of workers, which enlarge the nest, get more food,
dudstedeve ane queen of all- labor. except that of-egg-
laying. More broods of workers follow until the fall

21S ELEMENTARY ZOOLOGY

brood of males and females appears, after which the
original process is repeated.

The honey-bees and ants show a highly spéeglived
communal: life, with a well-marked division of labor and
an individual sacrifice of independence and _ personal
advantage which is remarkable. Their communities are
large, including thousands of individuals, and the struc-
tural differences among the males, females, and workers
are readily recognizable. With the ants the workers may
be of two or more sorts, a distinction into large and smal!
workers or worker majors and worker minors being not
uncommon.

A honey-bee community, living in hollow tree or hive,
includes a queen or fertile female, a few hundred drones
or fertile males, and ten to forty thousand workers, in-
fertile: females (fig. 80): The number of dromesmand

Fic. 80.—The honey-bee, Apis mellifica ; A, queen, B, drone, C, worker.
(from specimens. )
workers varies, being smallest in winter. Each kind of
individual has a certain particular part of the work of the
whole community to do; the queen lays all the eggs, that
is, is the mother of the entire community; the drones act
simply as the royal consorts, fertilizing the eggs; while
the workers build the comb, produce the wax from
which the cells are constructed, bring in all the food con-

Bpeaven ARTHROPODA ; CLASS INSECTA: THE INSECTS 219

sisting of flower-pollen and nectar, care for the young
bees, fight.off intruders, and in fact perform all the many
labors and industries of the community except those of
reproduction. There isa certain not very well understood
and perhaps not very sharply defined division of these
labors among the worker individuals, the younger ones
acting specially as ‘‘nurses,’’ feeding and caring for the
young bees (larve and pupe), the older ones making the
food-gathering expeditions. The queen lays her eggs one
in each of many cells (fig. 81). These eggs hatch in three
days, and the young bee appears as a white, soft, footless,
helpless grub or larva that is fed at first by the nurses with

Fic. 81.—Worker brood and queen cells of honey-bee ; beginning at the
right end of upper row of cells and going to the left is a series of egg,
young larvee, old larvz, pupa, and. adult ready to issue; the large
curving cells below are queen cells. (From Benton.)

a highly nutritious substance called bee-jelly which the
nurses make in their stomachs and regurgitate for the
larva. After two or three days of this feeding the larve
are fed pollen and honey. After a few days a small mass
of this food. is put into the cell, which is then ‘‘ capped.’’
or covered with wax. The larva after using up this food-
supply pupates, and lies quiescent in the pupal stage for

220 ELEMENTARY ZOOLOGY

thirteen days, when the fully developed bee issues, and
breaking through the wax cap of the cell is ready for the
labors which are immediately assigned it. The bee with
the kind of life-history just described is a worker. It has
been demonstrated that the eggs which produce workers
and those which produce queens do not differ, but if the
workers desire to have a queen produced they tear down
two or three cells around some one cell, enlarging this
latter into a large vase-shaped cell. When the larva
hatches from the egg in this cell it 1s tedter acs wauele
larval life with bee-jelly. From the pupa into which this
larva transforms issues not a worker but a new queen.
The eggs which produce drones or males differ from those
which produce queens and workers in being unfertilized,
the queen having the power to lay either terelized or
unfertilized eggs. When anew queen appears or when
several appear at once there is great e€xeitemenpm, tne
community. If several appear they fight among them-
selves until only one survives. It is said that a queen
never uses its sting except against another-queen. — lite
old queen now leaves the hive accompanied by many of
the workers. She and her followers fly away together,
finally alighting on some tree-branch and massing there
ina dense swarm. This is the familiar act of ‘‘swarm-
ing. Scouts leave the swarm to find a new home, to
which they finally conduct the whole swarm. Thus is
founded a new colony. ‘‘ This swarming of the honey-
bee is essential to the continued ‘existence of te species:
for in social insects it is as necessary that the colonies be
multiplied as it is that there should be a reproduction of
individuals. Otherwise as the colonies were destroyed
the species would become extinct. With the social wasps
and with the bumblebees the old queen and the young
ones remain together peacefully in the nest; but at the
close of the season the nest is abandoned by all as an

res)

meee AR ITTROPODA; CLASS INSECTA: THE INSECTS: 221

unfit place for passing the winter, and in the following
spring each young queen founds a new colony. Thus
there is a tendency towards a great multiplication of
colonies. But with the honey-bee the habit of storing
food for winter, and the nature of the habitations of these
Meee render it possible for the colonies to exist -in-
definitely, and thus if the old and young queens remained
together peacefully there would be no multiplication of
colonies and the species would surely die out in time.

Fic. 82.—Honey-bees building comb. (From Benton.)

Mieeeee, ceacreiorc, that. what appears to. be merely
jealousy on the part of the queen honey-bee is an instinct
necessary to the continuance of the species.’’

For the special labors of gathering food, making wax,
building cells, etc., the workers are provided with special
structures, as the pollen-baskets on the outer surface
of the widened tibia of the hind legs, the wax-shears
between the tibia and first tarsal joint of the hind legs,
the wax-plates on the ventral surface of the abdomen,
etc. A great many interesting things connected with the

iS

in or food

Although

ELEMENTARY ZOOLOGY

J

The gathering of food from long distances, the details
of wax-making and comb-building, of homey-making (for

life and industries of a honey-bee community can be

learned by the student from observation, using for a guide
some book such as Cowan’s ‘‘ Natural History of the

Honey-bee.

222

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Sstetecaceges Soa8 ESRI a) —

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sageateaneensseageaseetse bases ©
ESET R DLO LS PSOE ony Ss. aie
aiseretusracsstesetstsessnitcetestesc

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seiestedcccessesscsstcrsers

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1 honey
(From Benton.

Bast linea

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ae

O59 S sassrioses

A ay DO ‘=,
eeesscatessrereneanessaas
Seevtesteteneue

. 9 fo
Tey estes

natural size.

Fic. 83. —Comb of the tiny

ers is made into honey by an interesting
g of food, how the community protects
Sees

bees in egg and tarval stage, and many other phenomena
of the life of the bee community present good opportuni-

ties for careful observation and field study.
viduals do not live longs; the workers Jaateneaeim enc

scarce by killing the useless drones and the immature
the community is a persistent or continuous one, the indi-
spring usually not more than two or three months, and

itself from starvation when winter

the nectar of flow
process), the storin

peered? ARTHROPODA; CLASS INSECTA: THE INSECTS 223

fese hatehed in the fall not more than six or eight
months. But new ones are hatching while the old ones
are dying and the community as a whole always persists.
A queen may live several years, perhaps as many as five.
She lays about one million eggs a year.

There are more than two thousand known species of
ants (fig. 84), all of which live in communities and show a
truly communal life. The ant workers are specially dis-
tinguished in structure from the males and females by
being wingless, and in numerous species there are two
sizes or kinds of workers known as worker majors and
worker minors. The life-history and communal habits of
ants are not so thoroughly known as are those of the
honey-bee, but they show even more remarkable speciali-
zations. Theant nest or formicary is with most species an
elaborate system of underground galleries and chambers,
special rooms being used exclusively for certain special
purposes, as nurse-rooms, food-storage rooms, etc. The
food of ants comprises many animal and vegetable sub-
stances, but the favorite food with many species is the
‘‘honey-dew "" secreted by the plant-lice (Aphidide)
and scale insects (Coccide). To obtain this food an ant
strokes one of the aphids with its antenne, when the fluid
is excreted by the insect and drunk bythe ant. In order
to have a certain supply of this food some species of ants
care for and defend these defenseless aphids, which have
poems eed the ‘cattle’ of the ants. In some cases
they are even taken into the ants’ nests and food provided
for them. ‘‘In the Mississippi Valley a certain kind of
plant-louse lives on the roots of corn. Its eggs are
deposited in the ground in the autumn and hatch the fol-
lowing spring before the corn is planted. Now the
common little brown ant (Laszus flavus) lives abundantly
in the cornfields, and is especially fond of the honey
secreted by the corn-root louse. So when the plant-lice

224 ELEMENTARY ZOOLOGY

hatch in the spring before there are corn-roots for them
-to.feed-on, the little brown ants with great solicitude
carefully place the plant-lice on the roots of a certain
kind of knot-weed which grows in the field and protect
them until the corn germinates. Then the ants remove
the plant-lice to the roots of the corn, their favorite food-

Fic: ST he little black ant, MWonomorium minutum; a, female, 6, female
with wings, ¢, male, @d, workers, e, pupa, /, larva, g, egg of worker,
all enlarged. (From Marlatt.)

plant. In the-arid lands of New Mexico and Arizona the
ants rear scale insects on the roots of cactus.’’

The ants: are «among the most warlike Vom amseets.
Battles between communities of different species are
numerous, and the victorious community takes possession
of the food-stores of the conquered. Some species of ants
live wholly by war and robbery. In the case of the

eee ARTHROPODA; . CLASS INSECTA: THE INSECTS 225

remarkable robber-ant (/czfom), found in tropical and sub-
tropical regions, most of the workers are soldiers, and no
longer do any work but fighting. The whole community
lives exclusively by pillage. Some kinds of ants go even
farther than mere robbery of food-stores: they make
slaves of the conquered ants. There are numerous species
@@eiese siave-makine ants. hey -attack a nest of
another species and carry into their own nest the eggs
and larve and pupz of the conquered community, and
when these come to maturity they act as slaves of the
victors, collecting food, building additions to the nest,
and caring for the young of the slave-makers.

As with the honey-bee the larval ants are helpless
grubs and are cared for and fed by nurses. The so-called
‘ants’ eggs,’’ the little white oval masses which we often
see being carried in the mouths of ants in and out of an
Mite dest are Not eggs, but are the pupz. which -are
being brought out to enjoy the warmth and light of the
sun or being taken back into the nest afterward.

There are in this country numerous species of ants
showing much variety of habit and offering excellent
opportunities for most interesting field observations. For
an account of several of the common species see Com-
stock s “Manual of Insects,’ pp. 633-643. Ants may
be readily kept in the schoolroom in an artificial nest or
formicary and their life-history and habits closely watched.
For full directions for making and keeping a simple and
imexmemsive formicary see Comstock’s ‘‘Insect Life,’’
Pa 7-251. Foran interesting account of some of fhe
habits of the social insects see Lubbock’s ‘‘ Ants, Bees,
and Wasps.’

226 ELEMENTARY ZOOE@GY

CLASS. MYRIAPODA : THE MYRIAPODS, OR CENTIPEDS
AND MILLIPEDS.

Belonging to the branch Arthropoda, with the classes
Crustacea, and Insecta, are three other classes, en which
one, the Onychophora, is represented by a single genus
oo oo (Fig. 85), of extremely interesting animals.
However, as these animals are not found
in the United States we canner study
them. The other.two classes are. sic
Myriapoda, including the centipeds and
millipeds or thousand-legged worms, and >
the Arachnida, including the scorpions,
spiders; mites, and “itekG 97 wimeamicse
animals are often spoken of as insects,
but though related to them they are not
true imSects.

TECHNICAL NOTE.—From under stones or
logs obtain specimens of millipeds, or thousand-
legged worms (large blackish, cylindrical, worm-
like animals with each body-segment back of the
fourth bearing two pairs of jointed legs); also
specimens of centipeds or hundred-legged worms
(flattened, usually brownish or pale worm-like
animals with the body-segments bearing only one
pair of legs each) in the same places. Examine
the external structure; note number of body-
rings; division into body-regions ; presence of
Fic. 85.—ferifatus antenne ; character and number of eyes; charac-

eisent (Mexico). ter of mouth-parts; character and arrangement

(From specimen.) of legs. In the centipeds the first pair of legs is
modified to form a pair of poison-fangs. They appear to belong to
the mouth-parts. The internal anatomy will be found to be, if
examined, much like that of insects and can be studied from the
account of the anatomy of the water-scavenger beetle and butterfly
larva. Compare the Myriapods with the Hexapods or true insects.
What are the points of resemblance? what are the points of differ-
ence!

The Myriapoda are land-animals breathing by means
of trachee like the insects. In them the body-segments

ERANCH ARTHRUPODA ; CLASS MYRIAPODA : MYRIAPODS 22]

are nearly uniform in character with the exception of the
head, which, as in the insects, bears the mouth-parts and
antenne. here is no grouping of the body-segments
into regions except as the head is opposed to the rest of.
the body. (In a few myriapods there are indications of |
a division of the hind body into thorax and abdomen.) |
ae meesence of truce legs on all the
Seoments of the hinder region of the
body and the lack of the three-region
division of the body are the _ principal
external structural characteristics which
distinguish myriapods from insects. The
internal anatomy corresponds in general
character with that of insects.

The most familiar myriapods are the
millipeds, and the lithobians and centi-
peds. The millipeds are cylindrical in
shape, have two pairs of legs on most
of the body-segments and are vegetable
feeders, though some may feed on dead
animal matter. The galley-worms at
(Julus) (fig. 86), large, blackish, cylin- Ba ea
drical millipeds found under stones and Fulus sp. (From
logs and leaves and in loose soil, are ae!
familiar forms. They crawl slowly and when disturbed
curl up and emit a malodorous fluid. They can easily be
' kept alive in shallow glass vessels with a layer of earth in
the bottom, and their habits and life-history may thus be
studied. They should be fed sliced apples, green leaves,
grass, strawberries, fresh ears of corn, etc. They are not
poisonous and may be handled with impunity. They lay
their eggs in little spherical cells or nests in the ground.
-An English species of which the life-history has been
studied lays from 60 to 100 ecoscai.a time, . Lhe exes
of this species hatch in about twelve days.

228 ELEMENTARY ZOOLOGY

The lithobians and centipeds are flattened and have

but a single pair of legs on each body-ring. They are
predaceous in habit, catching and killing insects, snails,
earthworms, etc. “They can
run rapidly, and have the first
pair of legs modified into a
pair of poison-claws, which
are bent forward so as to lie
near the mouth. The com-

ig

hic) 7377 Vhe- skemm + centi-
ped, Scutigera forceps, nat- ei
ural size, common in houses Fic. 88.—A centiped, Scolo-

and conservatories. (From pendra sp. (From speci-
Marlatt. ) men.)

mon ‘‘skein’’ centiped (Scutigera forceps) (fig. 87) is
yellowish and has fifteen pairs of legs, long 40-segmented
antennz, and nine large and six smaller dorsal segmental

BRANCH ARTHROPODA ; CLASS ARACHNIDA : SPIDERS 229

plates. The true centipeds (Scolopendra) (fig. 88) have
twenty-one to twenty-three body-rings, each with a pair
- of legs, and the antennez have seventeen to twenty joints.
They live in warm regions, some growing to be very
law, as lone as twelve inches or more. — The ‘bite *’-or
wound made by the poison-claws is fatal to insects and
geaer simall animals, their prey, and painful or even
dangerous to man. The popular notion that a centiped
‘“stings ’ with all of its feet is fallacious. It is recorded
by Humboldt that centipeds are eaten by some of the
South American Indians.

CLASS ARACHNIDA: THE SCORPIONS, SPIDERS, MITES,
AND? Dicks:

TECHNICAL NOTE.—Obtain specimens of various spiders; the
running or hunting spiders may be found on the ground, especially
under stones. and boards, the web-makers on their snares. Get
also spiders’ ‘‘cocoons ” (egg- sacs). Examine the external structure
of the spider ; note the two body-regions ; the number and character
of legs ; the absence of antenne ; the number and arrangement of
the eyes (which are simple, not compound); the mouth-parts, espe-
cially the large mandibles ; the spinnerets at the tip of the abdomen
(examine a cut off spinneret under the microscope to see the spin-
ning-tubes) ; note the breathing openings or spiracles on under side
of abdomen. Obtain also a scorpion if possible, and some ticks and
mites. Compare with the spiders and note that in the scorpion
the body is plainly seen (especially in the abdomen) to be composed
of segments. Note the extreme fusion of the segments and body-
regions in the mites and ticks. The common red spider of hot-
houses and gardens is a mite; ticks may sometimes be found on
dogs. Observe various kinds of spider-webs, and try to observe
the process of web-making (this can be observed early in the morn-
ing or about dusk) by one of the orb-weaving garden-spiders.
Live spiders can be kept in the schoolroom and their feeding
habits and perhaps web-making habits observed.

The class Arachnida is composed of Arthropods whose
body-segments are grouped into two regions, a cephalo-
thorax bearing the mouth-parts, eyes, and legs, and an
abdomen. The segments composing these two parts are

230 ELEMENTARY ZOOLOGY

so fused that, except in the scorpions, they am megelly

Fic. 89.—A scorpion Cen-
trurus sp., from Cali-
fornia. (From specimen. )

and tieks--anG the /vraileiia, (of

spiders.

The scorpions (fig. 89) have

indistinguishable. There are no
antennz, the eyes are >sumple tie
mouth-parts fitted for biting, and
there are four !pairs “ok atesse in
their internal anatomy the arach-
nids show in some forms a pecu-
liar modification of the respiratory
organs, the tracheze bee fat and
leaf-like and massed together in a
few groups rather than being tubular
and ramifying through the body.
The dorsal vessel or heart usu-
ally has a few blood-vessels or
arteriesrunning fromit. This class
is divided. into three “orders, one
Arthrogastra, or scorpions, the
JaWGeh aie Fe
O-Tactaites

the posterior six segments of
the abdomen much narrower
than the seven anterior -seg=
ments and forming a tail which
bears at its tip a poison-fang or
sting. This sting is used to kill
prey, insects and other small
animals. The tail can be darted
forwards over the body to strike
prey which has been previously
seized by the large pincer-like
maxillary palpi. Scorpions are

Fic. 90.—The cheese-mite, 77-
roglyphus stro, greatly en-

larged.

(After Berleses)

common in warm regions, about twenty species being

BRANCH ARTHROPODA ; CLASS ARACHNIDA e SE LDERS 32:38

known in southern North America. Their sting though
painful is not dangerous to man. The young are born
alive and are carried about by the mother for some time
after birth.

Owe mites (figs. 90 and 91) and ticks (fig. 92) are
mostly small obscure animals, which live more or less
parasitically. The common red spider of house-plants
as well as the sugar- and cheese-mites, the dreaded

V, /
Fic. 91.—Bird mite, species undetermined, from the gnome-owl, Glauci-
dium gnomus. (Photo-micrograph by Geo. O. Mitchell.)

itch-mite and the chigger are familiar examples of these
degraded arachnids, and the wood-ticks, dog- and
chicken-ticks are common examples of the larger blood-
sucking forms. The body in both mites and ticks is very
compact, the two body-regions, cephalothorax and ab-
domen, being closely fused.

The spiders have the abdomen distinctly set off from the
cephalothorax. The eyes (fig. 93) vary in number and
arrangement, the mandibles are large, each being com-
posed of two parts, a basal hair-covered part, the falx, and
a terminal smooth, shining, slender, sharp-pointed part,

232

ELEMENTARY ‘ZOQOEOGM

the fang, which is movably articulated with the falx
(fig. 93’. In the falx is a poison-sac. from which poison

Fic. 92.—The dog or wood tick, Dermacentor americanus male, the most
common tick in the Northern States. (After Osborn. )

flows through the hollow fang and out at ats 7tip. iive
legs Maby in relative length in different spiders, and each

Rie oee—— ine
eyes and jaws,
showing falx
and fang of a
spider. (From
Jenkins and
Kellogg.)

is made up of seven joints. The spinnerets
(fig. 94), which are situated at the tip of the
abdomen, are six in number (a few spiders
have only four), and are like Werleshort
fingers. “They have at their tps: aaamy ane
little spinning-tubes from each of which a
fine silken thread issues when the spider is
spinning. These many fine threads fuse as
they issue to form a single strong eable or
sometimes. a flat rather broad bands] Phe

spinnerets are movable, and by their manipulation the
desired kind of line is produced. The silk comes irom

BRANCH ARTHROPODA ; CLASS ARACHNIDA : SPIDERS 233

many silk-glands in the abdomen, from each of which a
fine duct runs to a spinning-tube.

The spiders may be divided into two groups according
to their habits, viz., the wandering or hunting spiders,

Fic. 94.— The six spinner-
ets (below) of a spider,
with one spinneret en-
larged (above) to show 4
the spinning ‘‘ spools”’ Fic. 95.—A long-legged spider,
or tubes. (From Jenkins Tetragnatha sp., on its web.
and Kellogg. ) (From life. )

which do not spin webs to catch their prey, and the
sedentary or web-weaving spiders, which spin snares to
catch their prey. The wandering spiders can spin silk,
however, and often do soto. line their burrows, to make
nests, or to make egg-sacs.

The hairy tarantulas and the trap-door spiders of
similar appearance are among the most interesting of

234 ELEMENTARY ZOOLOGY

the hunting spiders. They live in vertical burrows or
tunnels in the ground which are lined with silk, and which
in the case of the trap-door spider are covered with a door
or lid made of silk and soil. The top of this door is

Fic. 96.—A running spider (Lycoside’. (From life.)

always covered with soil or bits of leaves or twigs so that
it is nearly indistinguishable from the surface of the
ground about it. When the nest is in ground covered
with moss the spider covers the door with moss. The

Fic. 97.—A female running spider (Lycosidz) carrying its egg-sac about
attached to its spinnerets. (From Jenkins and Kellogg.)

tarantulas hunt at night and rest in the burrow in the
daytime. They are very large, sometimes’ having an
expanse of legs of 6 inches.

The common, rather large swift black spiders found

BRANCH ARTHROPODA ; CLASS ARACHNIDA: SPIDERS 235

under stones and boards are hunting spiders, belonging
to the family Lycosidz and are called the running spiders
(fig. 96). They live in burrows in the ground, coming
out to stalk and chase their prey. The eggs are laid in
slobular egg-sacs which are often carried about, attached
to the spinnerets, by the female (fg. 97). The young
spiderlings after hatching, in some species, climb on to
the mother’s back and are carried by her for some time.
Other kinds of wandering or hunting spiders are the crab-
spiders (Thomisidz) (fig. 98), which run sidewise or back-
ward as well as forward, and the black and red, fierce-

Fic. 98. — A crab-spider (Thomi- Fic. 99.—A jumping spider (Atti-
sidz). (From Jenkins and Kellogg.) dz.) (From Jenkinsand Kellogg

eyed, stout-bodied little jumping spiders (Attidz) (fig. 99),
which leap on their prey.

The sedentary or web-weaving spiders are of various
kinds. They may be grouped according to their spinning
habits into cobweb weavers (Theridide), small slim-
legged spiders which make the familiar unsymmetrical
cobwebs of houses and outbuildings; funnel-web weavers
(Agalenide), larger long-legged pies of meadow and
field which spin a flat or concave horizontal web in the
grass with a silken tube leading down to the ground;
the curled-thread weavers (Dictynidez), which use in addi-
tion to the usual lines peculiar broad lines made of waved
or curled threads in their irregular webs made in fence-

236 ELEMENTARY ZOOLOGY

corners and on plants; and finally orb-weavers (Epeiridz)
(fg. 100), the host of variously colored and patterned
stout-bodied garden-spiders which spin the beautiful sym-
metrical circular webs familiar to all (fig. 101). If a
complete uninjured orb web be examined it will be found
to consist of a small central hub either open or closed,
from which run radii to the outer edges of the web.
Around the hub is an open or free zone, and farther out
a spiral zone, so called because a line running in close

Fic. 100.—Argiope sp., a large orb-weaver (Epeiride). (From Jenkins
and Kellogg.)

spiral turns fills in the space between the radii. This is
the real prey-catching part of the snare, and the silken
line here is sticky, while the radii and some other parts
of the web -are made of silk. that is net Smekys. Iie
web is supported by strong foundation-lines, attached to
leaves, stems, or whatever is firm in the neighborhood of
the web. The spider either rests on the web, usually in
the centre, or lies concealed in a nest or tent near at hand
from which a special path-line runs to the centre of the
web. The building of one of these orb webs is a great

BRANCH ARTHRCPCDA ; CLASS ARACHNIDA : SPIDERS 237

work, and is done with extraordinary nicety of manipula-
tion by the use of feet and spinnerets. For account of

Fic. 101.—Spider and its web in a rose-bush. (Photograph from life by
Cherry Kearton; from ‘‘ Wild Life at Home,”’ by permission of Cassell

& Co.).

web-making, etc., see McCook’s ‘‘ American Spiders and
their Spinning Work.’’

The habits and instincts of spiders in connection with
the care of the young, the building of webs and nests,
ballooning by means of silken lines, the active stalking
and catching of prey, etc., are very interesting and offer

238 ELEMENTARY ZGOLOGY

a good field for independent observation and study by the

student.

Frc. 102.—The triangle spider, Wyptzotes sp. (California), with its web; the
spider rests on the taut guy-line, with a loop of the line held between
its fore and hind legs; when an insect gets into the web the spider
loosens the hold of its hind feet on the guy-line, thus allowing the web .
to spring forward sharply and further entangle the prey. (From

Jenkins and Kellogg.)

CHA PEER Dox

MOLLUSCA: THE MOLLUSCS

THE FRESH-WATER MUSSEL (C20 sp.)

Structure (fig. 103).—TECHNICAL NOTE.—The fresh-water or
river mussel lives commonly in the streams and lakes or ponds in
the United States. It frequents muddy or sandy bottoms. Speci-
mens can often be secured with a long-handled rake from the shore
or picked up in shallow streams with the hand. If possible to keep
the animals alive until ready for use, some of their habits may be
observed. Place them in a tub or trough with water and mud ;
when they have settled themselves put some powdered carmine,
starch, or similar substance in the water near them, and note the
water-currents.

Living mussels which have been placed in a dish with
mud several inches deep and covered with water will be
seen to travel in a definite direction. The end which is
in front is the head end. Note the process of thrusting
out and retracting the fleshy foot which extends between
the two valves of the shell. Note that the two valves are
held together along the upper, or dorsal, surface by a
horny structure, the Azzge-ligament. Note near the hinge-
line a prominence (a0) in each valve from which ex-
tends a series of concentric lines of growth. The umbo
is the oldest part of the valve. Note at the lower edge
of the valves a soft membrane with a fringe along its free
border. This is the edge of the mantle-lobes, flaps of the
body-wall which cover the body and which aid in the
functions of respiration and nutrition,

239

240 ELEMENTARY ZOOL@GH

TECHNICAL NOTE.—Specimens which are to be dissected should
be killed by dropping them for a few seconds into warm water, when
the muscles will relax enough so that a chip may be thrust between
the valves. -If specimens are to be kept for some time before dis-
secting they should be preserved in alcohol or 4% formalin. In a
dead specimen carefully remove the left valve. This is accomplished
by slipping in a thin knife-blade close to the inner edge of the left
valve and carefully cutting the two large adductor muscles which
bind the valves together. The dissection should be made under
water.

Before the removal of the valve, as just described,
notice a portion of the mantle adhering to the inner face
of the valve, along a line of attachment indicated by a
crease. Jhisis the pallial line. After; the ler wae has
been removed, the mantle being carefully separated from
it, note the large conical projections from the valves, the
hinge teeth, which fit into each other. Note the large
muscle impression just in front of the hinge-teeth; this is
the point of attachment of the azterior adductor muscle,
while just behind and adjoining it is the impression of the
anterior retractor muscle. Note posterior to the adductor
and below the retractor a small impression which affords
attachment for the protractor muscles of the foot. At
the other end of the valve, note the large impression of the
posterior adductor muscle with the impression of the small
posterior retractor muscle just above it.

TECHNICAL Nore.—Lift back the left mantle-lobe, thus exposing
the body parts underneath.

Note the projecting muscular foot, the movements of
_which,.are governed by the retractor and Spremeactor
muscles attached to the impressions Just mentioned.
Note a pair of flattened plate-like structures composed of
thin, ribbed, membranous folds. ‘These are tes 27/75
Note just beneath the anterior adductor muscle a small
opening leading into the soft vzsceral mass of the body.
This is the mouth. Note near the mouth two pairs of
plate-like structures much smaller than the gills. These

MGOELUSCA: THE MOLLUSCS 241

are the /abzal palpi, and it is by their action that food-
particles which have been brought in with the water are
conveyed to the mouth. Note at the posterior part of
each mantle-lobe a fringed portion which, together with
a corresponding part on the other side, forms the zzhalant
siphon. Vhe cilia of the fringes carry water and food-
particles into the space enclosed by the mantle-lobes;
this space is the mantle-cavity. After the food has been
taken out and the water has passed through the finely
striated gills it is collected in a common cavity which
extends above the two sets of gills on each side. This
space is called the supra-branchial cavity. This cavity
is continuous posteriorly with a space between the right
and left mantle-lobes, which is connected with the
exterior by an opening above the inhalant siphon called
the exrhalant siphon. The function of the gills is partly
to produce currents of water carrying the food to the
mouth, and partly respiratory. The mantle is an impor-
tant organ of respiration.

Make a drawing showing the organs described.

TECHNICAL NOTE.—Carefully cut away the mantle and gills

from the leftside, and also the labial palpi, being careful not to dis-
turb the visceral mass.

Note two openings along the line where the gills and
foot come together. The uppermost is the opening of the
ureter giving exit to the excretion from the kidneys; the
lower is the opening of the duct from the reproductive
organs and is called the genital aperture. ‘The products
from both of these organs are carried out through the
exhalant siphon.

Note that the mouth leads by a short tube (wsophagus
or gullet) into a large cavity, the stomach, which is sur-
rounded by a greenish mass, the digestive gland.

TECHNICAL NOTE.—Carefully cut the delicate covering of the
dorsal portion of the visceral mass and expose a cavity.

242 ELEMENTARY ZOOLOGY

The cavity thus exposed is the perzcardium. Note
within the pericardium a long tube extending through it.
This is a portion of the alimentary canal, the rectum,
which opens posteriorly through the azuzs into the supra-
branchial chamber. Note a muscular sac about the
rectunn midway of its course through the pericardium.
This is the unpaired ventricle of the heart. Attached to
each side of the ventricle are thin-walled sacs, the rzght
and left auricles, which are entered by fine blood-vessels,
the efferent branchial veins, from the right and left gills.
The blood brought through these blood-vessels from the
gills flows into the auricles and from them into the un-
paired muscular ventricle, from which it is forced anteriorly
and posteriorly through two main arteries, the azterzor
and posterior aortas, to all parts of the body. After
bathing the bady-tissues the blood is collected into a
median longitudinal vein beneath the pericardium called
the vena cava. From the vena cava the blood passes
through the kidneys and gills to be returned at last to the
heart. The mantle acts as an organ for the aeration of
the blood, and the blood it receives or at least part of it
passes directly back to the heart without passing through
the kidneys and gills.

Note the delicate membranous dark-colored sac on the
floor of the pericardium, the kzdueys or nephridia. These
are paired structures which appear as two U-shaped tubes
lying side by side. Each consists of a lower portion with
thick folded walls, the kidney proper, and an upper thin-
walled portion, the wre/er. The kidneys open internally
through a pair of reno-pericardial openings into the peri-
cardium, while the ureters communicate with the mantle-
cavity by an opening on the side of the body beneath the
gills as already mentioned. ‘Vhe kidneys are profusely
supplied with fine blood-vessels and carry off the waste
matter from the blood.

MOLLUSCA: THE MOLLUSCS 243

Beneath the posterior adductor muscles note a small
white spider-shaped body, the more or less united vzsceral
ganglia of the nervous system. Posteriorly these ganglia
give off nerves to the mantle and gills, while anteriorly
there proceed two nerves, the cerebro-visceral connectives,
running forward, one on either side of the foot close to
the visceral mass, to the cerebro-pleural gangla, paired
ganglia lying near the mouth. A delicate commissure
running over the gullet connects these ganglia.

TECHNICAL NOTE.—Cut away the skin and outer muscular layer
from the left side of the foot.

Note the large stomach-cavity, surrounded by the
digestive gland. Trace the convolutions of the alimentary
canal through the foot to the anal exit. Note in the
anterior portion of the foot a fused pair of ganglia similar
to the visceral ganglia. [hese are the pedal ganglia,
which are connected by a pair of delicate commissures,
the cerebro-pedal connectives, with the cerebro-pleural
ganglia. Note the glandular tissue which fills the cavity
of the foot and surrounds the loops of the alimentary
canal. This is the reproductive organ, which has its exit
teneath the gills on each side of the foot. The sexes of
the mussel are separate, but the reproductive organs are
very similar.

Life-history and habits.—The eggs (ova) of the female
pass first into the supra-branchial chamber, whence, after
being fertilized, they drop into the outer pair of gill-
chambers. These outer gills serve as brood-pouches, and
here it is that the embryonic stages are passed through.
The embryo when ready to issue has a soft body enclosed
in two triangular valves. At this stage it is called a
glochidium. The glochidium on being discharged through
the exhalant siphon of the parent falls to the bottom,
where it remains for a time, when it attaches itself to some

244 ELEMENTARY ZOOLOGY

fish by the lower hook-like projections of the valves and
leads a truly parasitic life for two months, after which it
undergoes a metamorphosis and falls to the bottom again,
there to begin an independent existence. Mussels often
congregate in favorite mud or sand banks. Uhem tood
consists primarily of small organisms, both plants and
animals, which are taken from the water entering the
mantle-cavity. Mussels move about slowly over the
muddy bottom of the stream by means of the muscular
foot. |

OTHER MOLEUSES:

The branch Mollusca includes the fresh-water mussels,
the clams, oysters, snails, and slugs, the cuttlefishes, and
all that host of animals we call ‘‘ shells’’ or shell-fish, which
we know familiarly only by the shell which they make,
live in, and leave at death to tell-the tale ar their Gxast-
ence. Not all the molluscs, however, form shells, that
is, external shells which serve as houses. The familiar
slugs do not, nor do a number of ocean forms called
nudibranchs, which are somewhat like the land-slugs, only
much prettier and more attractive. All the cuttlefishes
and octopi are also without the hard calcareous shell.
But most of the molluscs are shell-bearing animals. The
shell may be bivalved, as in the mussel and clam, or uni-
valved, that is, composed of a single piece which may be
spirally twisted, as with the snail, or otherwise curiously
shaped. The variety in the form, colors, and markings
of the shells indicates the great diversity among molluscs.
Molluscs live on land, in fresh water and in the ocean.
No depths. of the ocean abysses are too %g@reatsionr tite
octopi, no coast but has its many shells, hardly a pond
or stream is without its mussels and pond-snails, and in
all regions the land-snails and slugs abound.

MOLLUSCA : THE MOLLUSCS 245

Body form and structure.—The molluscs are not to
be mistaken for any other of the lower animals; they
have a structure peculiarly their own. In them the body
is not articulated or segmented as with the worms and
arthropods, nor radiate as in the echinoderms, nor plant-
like as with the sponges and polyps. Where the typical
molluscan body is well developed it is composed of four
principal parts: a head, with the mouth, feelers, eyes, and
other organs of special sense; a trunk containing the
internal organs; a foot which is a thick muscular mass not
at all foot- or leg-like in shape, but which is the organ
of locomotion by means of which the mollusc crawls; and
a mantle which is a fold of the skin enclosing most of the
body and which produces the shell. Such a typical
molluscan body is possessed by most of the snails. But
in most of the other molluscs one or more of these four
body-regions are so fused with some other region as to
be indistinguishable. In the mussels and clams the head
is not at all set off from the rest of the body, the cuttle-
fishes and octopi have no foot, the slugs have no shell. In
the case of some ofthe molluscs without external shell there
are inside the body the rudiments or vestiges of a shell.

With regard to the internal organs we note the constant
presence of three pairs of ganglia, viz., the brain, lying
above the pharynx, which sends nerves to the feelers,
eyes, and auditory organs; the pedal ganglion, which sends
nerves to the foot, and the visceral ganglion, which sends
nerves to the viscera. This is a condition of the nervous
system characteristic of all molluscs. The heart is a well-
developed pulsating sac in the upper part of the body
composed of either two or three chambers, and there is a
well-defined closed system of arteries and veins, specially
complete in the cuttlefishes and octopi. This highly
developed condition of the circulatory system also distin-
guishes the molluscs from the other invertebrates.

246 ELEMENTARY ZOOLOGY

Development.—Reproduction among the molluscs is
always sexual. Multiplication by budding or by the
parthenogenetic production of eggs is not known to occur.
The eggs are usually laid ina mass held together by a
gelatinous substance. In most species the young mollusc
on hatching from the egg does not resemble its parent,
but is a free-swimming larva called a veliger. It is
provided with cilia for organs of locomotion. It must
undergo a radical change in order to reach the adult
stage. Thus metamorphosis occurs in this branch as well
as among the Arthropods and Echinoderms. In the
development of some molluscs, however, there is little or
no metamorphosis, the young being hatched in a condi-
tion much resembling, except in size, the parent.

Some of the special characteristics of structure, life-
history, and habits of the molluscs will be noted in our
consideration of the various kinds.

Classification.—The branch Mollusca is divided into
five classes, three of which include the more familiar
kinds. ‘These three classes are the Pelecypoda, including
the mussels, cockles, clams, scallops, oysters, etc., mol-
luscs with a shell composed of two pieces, one on each
side of the body and hinged together; the Gastropoda,
including the snails, slugs, periwinkles, whelks, and a host
of other univalved shell-fish, that is, molluscs which have
a shell composed of a single piece; and the Cephalopoda,
including the squids, cuttlefishes, octopi, and the pearly
nautilus.

Clams, scallops, and oysters (Pelecypoda).—Tecunicat
NOTE.——Shells of scallops, oysters, and sea-mussels should be had for
examination ; also specimens of Z7evedo or Pholas in alcohol or for-
malin, and pieces of pile bored by Zeredo. Make drawings of vari-
ous bivalve shells, and of Zeredo.

The fresh-water mussel which we have studied is an
example of the bivalve molluscs. The members of this

hinge ligam

right auricle
anterior aorta

reno-pericardial aperture . :
renal aperture.

genital aperture ~..

stomach~---------
digestive gland.2.. 2-9. 4g

gullet------ -4 ;
cerebro-pleural ganglion - 422

antestine~

a
typhlosole”

gonad

Fic. 103.—Dissection of

ventricle

: pericardium

_-_—-«
mw ew owe ee

rectum
kidney
, _--- dorsal pallial aperture

--- posterior aorta

------7- post. retractor

--------- post adductor

wee eee --- -----~ ANUS

ee ae ee visceral ganglion

exhalant siphon

“-~" super branchial chamber

Se nee ge ey ame ee

Gees 2 gat Gull

sf AYRE ee -inhalant siphor

pallial groove

\
mantle

\
mantle cavity

sh-water mussel, Uo sp.

MOLLUSCA : THE MOLLUSCS 247

class show a range in size from the little fresh-water
Cyclas about I cm. long to the giant clam of the Indian
and Pacific islands ‘‘ which is sometimes 60 cm. (2 feet)
in length and 500 pounds in weight.’’ They show also
some variety in the form and appearance of the shell, but
not anything like the degree of variety shown by the
shells of the Gastropods.

The edible clams are of several different species. The
hard-shell clam (Venus mercenaria), or ‘‘ quohog’’ as it
is often called, is found along the Atlantic coast from
Texas to Cape Cod. It is ‘‘common on sandy shores,
living chiefly on the sandy and muddy plots, just beyond
low-water mark. ... It also inhabits estuaries, where it
most abounds. It burrows a short distance below the
surface, but is frequently found crawling at the surface
with the shell partly exposed.’’ ‘The shells of this edible
clam are white. The soft-shell clam (J/ya arenaria),
‘“‘the clam par excellence, which figures so largely in the
celebrated New England clam-bake, is found in all the
northern seas of the world. . . . All along the coasts of
the eastern States, every sandy shore, every mud fiat, is
full of them, and from every village and hamlet the clam-
digger goes forth at low tide to dig these esculent
bivalves. The clams live in deep burrows in the firm
mud or sand, the shells sometimes being a foot or fifteen
inches beneath the surface. When the flats are covered
with water his clamship extends his long siphons up
through the burrow to the surface of the sand, and
through one of these tubes the water and its myriads of
animalcules is drawn down into the shell, furnishing the
gills with oxygen and the mouth with food, and then the
water charged with carbonic acid and fcecal refuse is
forced out of the other siphon. When the tide ebbs the
siphons are closed and partly withdrawn.’’ Ocean clams
and mussels have furnished food for man for ages, and

248 ELEMENTARY ZOOLOGY ~

along coasts are found here and there great mounds
made of heaps of clam-shells which have become covered
over with soil and vegetation. Such mounds are the old
feasting-places of the early coast inhabitants, and the
archeologist often finds in these ‘‘ kitchen-middens,’’ as

Fic. 104.—A group of marine Pacific Coast molluscs; in upper left-hand
corner, Purpura saxicola; next to the right, Lalavima scuiulaia;
farthest to right, limpets, Acmara spectrum; left-hand lower corner,
Mytilus californianus; in right-hand lower corner the black shells just
above the large clam-shell, Ch/lorostomum funebrale. (From living
specimens in a tide pool in the Bay of Monterey, California.)

they are called, various relics of the early natives of the
continent.

Even more widely known that the clams are the oysters
(Ostrea virginiana), also members of this class of mol-
luscs. The oyster is carefully cultivated by man in many
countries. It has its two shells or two shell-halves dis-
similar, one valve being hollowed out to receive the body,
while the other is nearly flat. The oysteris 2iacmed to
the sea-bottom by the outside of the hollowed-out valve.
When first hatched the young oyster swims freely by
means of its cilia; after a few days it attaches itself to

MOLEUSC A: THE” MOLLUSCS 249

some solid object and grows truly oyster-like. Much care
has to be taken in cultivating oysters to furnish proper
conditions for growth and development. The young
oysters when first attached are called ‘‘spat’’; when a
iene older this <‘spat, now. called ‘‘seed,’’ may be
transplanted to new beds, which are stocked in this way.
In fact some beds have constantly to be thus restocked,
the young oysters produced on them not finding good
places to attach themselves, and so swimming away.
Sometimes pieces of slate, pottery, etc., are strewed about
tee seyerer-oeds to serve as ‘‘collectors,’’ that is, as
places for the attachment of the young oysters. The

Fic. 105.—Dacty/us sp., a mollusc, excavating granite. (Photograph by
C. H. Snow; permission of Amer. Soc. Civil Engineers. )

extent of the acreage of the American oyster-beds is
reer than that of any other country. ‘‘ The Baltimore
oyster-beds on the Chesapeake River and its tributaries
cover 3,000 acres, and produce an annual crop of 25,000, -
ooo bushels.’’

The ‘‘ pearl-oyster ’’ is not a true oyster, that is, nota
member of the family to which the edible oysters belong,

250 ELEMENTARY ZOOLOGY

but it is a member of the same class, that is, it is a bivalve
mollusc. Pearls are obtained from a number of different
‘‘pearl-oysters,’’ but the finest pearls and mother-of-pearl
come from the tropical species Weleagrina margaritifera.
This pearl-oyster ‘‘has an extensive distribution, being
found in Madagascar, the Persian Gulf, Ceylon, Australia,
Philippine Islands, South Sea Islands, Panama, West
Indies, etc.’’ Mother-of-pearl is simply the inner lining
of the shell, which is composed of numerous thin layers of
carbonate of lime so arranged that the edges of the suc-
cessive layers produce many fine striz very close together.
The beautiful iridescence of this inner shell-lining is
caused by the complicated diffraction and reflection (inter-
ference effects) of the light by the fine ;sijasame the
translucent superposed thin plates of shell material.
Pearls are simply isolated deposits of shell material usually
around some particle of foreign substance which has found

Fic. 106.—Pholas sp., a mollusc, burrowing in sandstone. (Photograph
by C. H. Snow; permission of Amer. Soc. Civil Engineers. )

lodging in the mantle-cavity. Sometimes small objects
are purposely introduced into the shell in order to stimu-
late the formation of pearls. The pearl-fishers go out in
boats and dive to the bottom, filling baskets with pearl-
oysters. These are piled up in a bin and left to die and

MOLLUSCA : THE MOLLUSCS 257

decompose. ‘‘ When the flesh is pretty thoroughly dis-
integrated, it is washed away with water, great care being
taken that none of the pearls loose in the flesh are lost.
When the washing is concluded the shells themselves are
examined for pearls which may be attached to the interior
The principal pearl-fishery is that on the

2 i)

of the valves.
coast of Ceylon; pearl-fishing has been carried on here
for over 2000 years. |

The ship-worm (Zeredo) is an interesting member of
this class of bivalve molluscs, because of its unusual

Fic. 107._-Martesia xylophaga, a Pholad, in Panama mahogany. (Photo-
graph by C. H. Snow; permission of Amer. Soc. Civil Engineers. )

habits, and strangely modified body form. The teredo
is long and worm-like in general appearance, with a small
bivalve shell at one end and two elongated siphons at the
other. The young teredo is a free-swimming ciliated
embryo like the young of the other bivalve molluscs, but
it soon settles on a piece of submerged wood, usually the
pile of a wharf, or the bottom of a ship, and burrows into
this wood. As it grows it enlarges and deepens its tube-
like burrow, and lines it with a calcareous deposit. The
burrow may be a foot long or longer, and when thousands
of teredos attack a pile or the bottom of a ship, the wood
soon becomes riddled with holes. These boring molluscs

252 ELEMENTARY ZOOLOGY

do great damage to wharves and ships. In Holland
where they were first discovered they caused such injuries
to the piles and other submerged wood which supported

Fic. 108.—The giant yellow slug of California, Aviolimax californica.
This slug reaches a length when outstretched of 12 inches. (From
living specimen. )

the dikes and sea-walls that they seriously threatened the
safety of the country. :

Snails, slugs, nudibranchs and ‘‘ sea-shells’’ (Gas-

tropoda). Pond-snails can be readily found
clinging to submerged stems, lenmen or pieces of wood in almost
any pond. Collect some and carry alive, in a jar of water, to the
schoolroom. Observe the habits of these live snails in the school aqua-
rium. Note the movements, the coming to the surface to breathe,
the eating (by scraping the surface of the leaves with the “ radula ”
or tongue ; provide fresh bits of cabbage or lettuce-leaves), the use
of the feelers. . Make drawings illustrating these habits. Examine
the shell; "mete that at is univalved, that is, composed of one piece.
Do the ober of all the shells turn the same way? Make a draw-
ing of the shell, naming such parts as the apex, spire (all the whorls
taken together), the aperture, the columella (the axis of the spire),
the lip (outer edge of the aperture), the lines of growth (parallel to
the tip), the suture (the spiral groove on the outside). Examine the
snail; note the character of the foot ; note the protrusible tentacles
or feelers, the eyes (dark spots at bases of the tentacles), the mouth,
the respiratory opening (on right side of body in the edge of the
mantle which protrudes beneath the lip when the snail’s body is ex-
tended), the radula or ribbon-hke tongue with fine teeth. Compare
with the body of the mussel.

Slugs may be found during the day concealed under boards or
elsewhere ; they are nocturnal in habit. If specimens can be ob-
tained, compare with the pond-snails, noting the absence of a shell,
and the fleshy mantle on the dorsal surface near the head ; note the
presence of two pairs of tentacles (the eyes being at the tips of the

MOLLUSCA : THE MOLLUSCS 253

second or hinder pair), and the respiratory pore. Note the streak
of mucus left by the slugs in crawling about.

Some sea-shells can be got from private collections of ‘ curios”
to illustrate the variety of form of the univalve shells.

Perhaps one-half of all the known species of molluscs
are snails and slugs (fig. 108). Snails are either aquatic or
terrestrial in habit, but in either case they (the true pulmo-
nate snails) breathe not by means of gills, as do most of
the other molluscs, but by means of a so-called ‘‘lung.’’
This lung is a sac with an external opening on the right
side of the body and with its inner surface richly furnished
with fine blood-vessels. The exchange of gases between
the blood and the outer air takes place through the thin
wails of the blood-vessels. Most snails which live in the
water, as the pond-snails and the river-snails, have to
come occasionally to the surface to breathe. These fresh-
water and land-molluscs which possess a lung-sac instead
of gills constitute the order Pulmonata. The pulmonate
pond- and land-snails and slugs are vegetable feeders and
where they occur in large numbers do much injury to
vegetation. While the common pond-snails have but
one pair of feelers, at the base of which are found the
eyes, most of the land-snails and slugs have two pairs of
‘‘horns,’’ the eyes being on the tips of the second pair.
The lung-sac, besides serving as a breathing organ, also
enables the snail to rise or sink according as the animal
varies the size of the sac and consequently the amount of
air in it. AJl the Pulmonata are hermaphroditic, each
individual producing both sperm- and egg-cells. The
eggs of the pond-snail ‘‘are laid in gelatinous transparent
capsules, half an inch to an inch in length, flattened and
linear or oblong i in outline. After a few snails have been
kept a short time in a small vessel of water with their
appropriate food, these egg-capsules may be looked for
on the bottom and sides of the vessel or closely adherent

254 ELEMENTARY ZOOLOGY

to the stems or leaves of plants placed in the water.
They are so transparent as to be easily overlooked.’’
Young snails may be reared from these eggs. |

There are other snails common in ponds, also called,
like the pulmonate forms, pond-snails, which have gills
and no lung-sac. ‘These pond-snails belong to a different
order of molluscs, and live on the bottom of the pond,
crawling about in the soft mud and feeding on animal
instead of vegetable food.

The shells of the various kinds of snails vary much.
In many of the land-snails the spiral is not spire-shaped
or conical, but is flat. In some the whorls of the spiral
run from left to right (dextral) when the shell is looked
at with apex held toward one, while in others the whorls
run from right to left (sinistral).

Of the hosts of marine Gastropods we can notice only
a few kinds. The nudibranchs (fig. 109) are a group of

Fic. 109.—Three Pacific Coast nudibranchs; Doris tuberculata (in lower
left-hand corner), Echinodoris sp. (upper one), and Z77zopha modesta
(at right). (From living specimens in a tide-pool on the Bay of Mon-
terey, California.)

beautiful forms in which the shell is wholly wanting and

the mantle is usually absent. The gills are thus exposed

and are usually in the shape of delicate freely projecting

MOLILISCA: THE MOLLUSCS 255

tufts arranged in rows along the back. The body is often
strikingly and variedly colored. These soft, naked ‘‘ sea-
slugs’’ live near the shore, creeping about among the
rocks and seaweeds. About a thousand species of nudi-
branchs are known.

Among the shell-forming marine Gastropods there is
great variety in the size and shape and coloring of the
shells. Many are beautifully colored and patterned;
others are oddly and fantastically shaped. The cowries,
or porcelain shells, familiar in collections of ocean curiosi-
ties, have a large body whorl and a very short flat spire,
and the brightly colored shell looks as if enamelled.
Some of the coast tribes of Africa once used, and perhaps
still use to some extent, cowries as money. The limpets
(fig. 104) are among the most abundant of the seashore
molluscs, their low, broadly conical shells being plenti-
fully scattered over the rocks between tide-lines. The
‘‘oyster-drills ’’ are Gastropods with odd spiny shells which
do much harm in oyster-beds by settling down on the
oysters, boring holes through the shells and eating the
soft parts within. The helmet-shells, from which shell
cameos are cut, are composed of layers of shell material
of different colors. Among the specially beautiful shells
are the cone-shells, the olive-shells, the ivory-shells, etc.

Squids, cuttlefishes, and octopi (Cephalopoda).—
TECHNICAL NOTE.—Small squids preserved in alcohol or formalin
can be had of all dealers in biological supplies (see p. 453), and
specimens should be examined.

The squids (fig. 110), cuttlefishes, octopi or ‘‘devil-
fishes,’’ and the three living species of Vazzz/us constitut-
ing the class Cephalopoda are very different from the other
molluscs in appearance, and are in fact different in im-
portant structural characters. They can move swiftly,
have strangely modified organs of prehension, strong biting
mouth-parts, and eyes of very complex organization.

256 ELEMENTARY ZOOLOGY

‘They are the most highly organized molluscan forms, and
their predaceous habits and the great size to which some
of them attain have given them distinction among the
frerce and dangerous creatures ‘of ‘the seay @ Mitegene-all
strictly marine in habitat, and are all carnivorous. Most
of them have no shell, or where the shell is present it is
internal in all’ but “a very few forms. “Whe; femeaclealce
arms or feet surrounding the mouth which occur in all the
Cephalopods are provided with sucking organs or suckers,
in some cases with a horny toothed rim. These long,
powerful, grasping, tentacular feet, with the suckers and
five hooks, are very effective means of securing prey, and
the pair of strong, sharp, cutting mandibles or beaks are
equally effective in’ tearing to piecesie7s Wie wey camel tie
Cephalopods are almost as highly developed as those of
the vertebrates. They are unusually large and staring,
and add much to the terrifying appearance of the ‘‘ devil-
’ Cephalopods have the power of quickly chang-
ing color, because of the presence in the skin of many
pigment-cells which can expand so as nearly to touch
each other, thus producing a uniform tint over the whole
body, or which can contract so as to destroy this uniformity

fisies.

of color. There are several sets of these color-carrying
cells or chromatophores, each set of a color different from
the others. The purpose of this change of color is pro-
tective, the animal being thereby able to make its color
so harmonize with that of its immediate surroundings as
to become indistinguishable.

There are two principal groups of Cephalopods, viz.,
the Decapods and the Octopods. The Decapods, as their
name indicates, have ten feet or arms surrounding the
mouth, and in them the body is usually elongate, con-
taining a horny “‘pen.”’ or calcareous: {teeme seer his
group includes the cuttlefishes or sepias, from which are
obtained sepia ink and the cuttlefish bone used to feed

MOLLOUSCA: THE MOLLUSCS 257

canary birds. The ink is a secretion which the cuttlefish
discharges when attacked to create a cioud in the water
and thus escape unperceived. ‘The squids (Lolzgo) com-
monly used as bait by fishermen belong to the Decapoda.
The two extra feet or arms which the Decapods have in
addition to the eight possessed by the Octopods, differ
from the others in being longer and slenderer and having
suckers only on the distal extremities which are expanded
imbo “clubs ’’- (fig. 110).

The Octopods have a short, sac-like, sub-spherical body
and neither external nor internal shell. To this group

Fic. 110.—The giant squid, Ommatostrephes californica, (From specimen
with body (exclusive of tentacles) four feet long, thrown by waves on
shore of the Bay of Monterey, California. )

belong the famous devil-fishes (Octopus), whose strange
and terrifying appearance combined with their frequently
great size has furnished the basis for many a weird tale of
the sea. Octopi have been killed having tentacles more
meats ieet. ty tenoth.* The Jateest members= of < thc
class, however, are probably the giant squids (belonging
to the Decapoda) specimens of which have been captured
with a body-length of twenty feet, and arms thirty-five
feet long.

The beautiful paper sailor or argonaut (dr,gouauta argo),

268 ‘ELEMENTARY ZOOLOGY

which secretes a thin shell (not homologous with the
shell of the other molluscs) to protect her eggs, is a mem-
ber of the Octopod group. In fine weather the argonauts
sail in fleets on the surface of the ocean.

The pearly nautilus (Vautzlus pompilius) is a Cephalo-
pod with four gills instead of two, as with the Decapoda
and Octopoda, and is the only existing member of what
was in the earlier times of the earth’s history a large
group of animals. The nautili live in rather shallow
water usually creeping over the bottom feeding on small
marine animals. They make a many-chambered spiral
shell with its inner surface lined with beautiful pearly
nacre.

CHAPTER XXTHI

BReaNCH CHORDATA: THE VERTEBRATES,
ASCIDIANS, REC:

THE branch Chordata includes all the backboned
animals or vertebrates, comprising the fishes, salamanders,
frogs and toads, lizards, crocodiles, turtles and snakes,
birds, and all the quadrupeds or mammals, and includes
also a few small unfamiliar ocean animals which do not
look at all like the backboned animals, but which agree
with them in possessing a peculiar structure called the
notochord. This notochord consists of a series or cord of
cells extending longitudinally through the body from head
to tail, above the alimentary canal and below the spinal
nerve-cord. In all the vertebrates excepting a few low
forms, the notochord while present in the young, is re-
placed in the adult by a segmented bony or cartilaginous
axis, the spinal or vertebral column. But in the ascidians
or sea-squirts (called also tunicates) it persists throughout
life. In addition to this characteristic notochord, nearly
all the Chordata are marked by the presence, either in
embryonic or larval stages only, or else persisting through-
out life, of a number of slits or clefts in the walls of the
pharynx which serve for breathing, and which are called
cill-slits.

Structure of the vertebrates.—As the backboned or
vertebrate animals make up almost the whole of the
branch Chordata, and as the few other chordates are
animals the special structures of which we shall not under-
take to study in this book, we may note here some of the
other more obvious structural characteristics of the true

259

260 ELEMENTARY ZOOLOGY

vertebrates. The possession of a backbone or bony
(sometimes cartilaginous) spinal column is the character-
istic by which we distinguish them from the invertebrate
or backboneless animals. Furthermore, all of the verte:
brates possess an internal skeleton which is in most cases
composed of bone, and is firm and strong. In some of the
lower fishes, as the sharks and sturgeons, the skeleton is
made up of cartilage, tough but not hard. The vertebrate
skeleton consists typically of an axial portion comprising
the spinal column and head, and of two pairs of append-
ages or limbs, variously developed as fins, wings, legs
and arms. In some vertebrates these limbs are repre-
sented by mere rudiments, and in the lowest fish-like
forms, the lancelets and lampreys, there is mot the
slightest trace of limbs. A part of the central nervous
system, the spinal cord, runs longitudinally through the
body on the dorsal side of the alimentary canal; the cir-
culatory system is closed, the blood being always confined
in the heart and in vessels called arteries, veins, and capil-
laries, and the blood is red in color owing to the presence
of numerous red corpuscles or blood-cells. The nervous
system is highly developed, with a large brain in all the
typical forms, and with complex and usually highly
efficient special sense-organs. Respiration is carried on
by means of external gills, or by internal lungs which
communicate with the outside through the mouth and
nostrils. To the lungs and gills the blood is brought to
be “purithed,’’ i.e., to “give up its carbonic-acid eas-and
to take up oxygen.

Classification.—The Chordata are variously divided
by zoologists into eight or ten classes, of which (in the
eight-class system) the five classes* Pisces (fishes),

* The animals included by some zoologists in the single class Pisces, are

held by other zoologists to constitute three distinct classes, thus making a
subdivision of the branch into ten classes.

BietNCH CHORDATA: THE VERTEBRATES, ETG.. 261

Batrachia (batrachians), Reptilia (reptiles), Aves (birds),
and Mammalia (mammals), belong to the true vertebrates.
These classes will be considered in the five following
chapters.

The remaining three classes include a number of strange
marine forms which until recent years were considered as
worms, but which are now known to be the nearest living
allies of the earliest or primitive vertebrates. The rela-
tionship of these forms to early types is manifest, not in
the appearance or structure of the adult stage, but only
during embryonic or larval stages.

The ascidians.—The sea-Squirts, or Ascidians, com-
mon on the seashore, compose one class of these primitive

Fic. 111.—An ascidian or sea-squirt from the coast of California, (After
Jordan and Kellogg.)

chordate animals. They possess a simple, sac-like body |
(fig. 111), fastened to the rocks by one end, the other being

262 ELEMENTARY ZOOLOGY

provided with two openings, one for the ingress and the
other for the exit of water, a strong current of which flows
constantly through the body. By means of this current
the ascidian obtains food. Usually sea-squirts live
together in large colonies, and in some cases a number of
individuals enclose themselves in a common gelatinous
mass, forming what is called a compound ascidian.

The ascidian when born is a tiny, free-swimming, tad-
pole-like creature with a slender finned tail. It swims
about freely for only a few hours, however, soon attach-
ing itself to a rock, and in its further development becom-
ing degenerate. It loses its tail and with # the short
notochord possessed by the larva; the eye and the auditory
organ are lost, and the nervous system and alimentary
canal become much reduced and simplified. Sea-squirts
in their adult stage are very simple degenerate animals,
with low functional development, yet their embryonic and
larval conditions show a considerable degree of structural
specialization, and the presence of the notochord in these
early stages reveals their affinity with the backboned
animals.

CHAPTER XXIV

BRANCH CHORDATA (Continued): CLASS PISCES
(lIHE FISHES)

THE GOLDEN SUNFISH OR PUMPKIN SEED (Afomotis sp.)

TECHNICAL NOTE.—The species of sunfish named, or some closely
related species, can be obtained in any brook or stream in the
United States. Gzddosus lives in all streams north of Dubuque,
Chicago, Pittsburg, and along the eastern coast north of Charleston.
Closely allied species live in all the other parts of the countn
except in the higher Rocky Mountains west of Bismarck, Pueblo,
and Santa Fe. One species is found in the streams of California,
but none occurs in Washington or Oregon. In the few places
where a sunfish cannot be had, any species of bass or perch may
be used. Sunfish live in ponds and sluggish streams in deep holes
under a log or at the foot of a stump. They take eagerly a hook
baited with a worm, or they may be caught in nets. When sun-
fish cannot be kept fresh for study in class, specimens may be
preserved in alcohol or 4% formalin. But if possible to keep some
alive for a time in a jar or tub with plenty of fresh water, the colors
of the living fish, together with its manner of swimming and mode
of breathing, can be observed.

External structure * (fig. 112).—-Examine the general
configuration and make-up of the body. Note the deep,
laterally flattened trunk and paddle-like faz/. The head
is Closely fitted to the trunk without any neck. Note that

* The author wishes to call the attention of teacher and student to the
plan (referred to in the Preface, page v) adopted in writing the directions
for the dissections. The sequence of the references to the various organs
depends on the actual course of the dissection, and not upon the association
of organs in systems. And the directions are so much condensed that they
are hardly more than a means of orienting the student, leaving him to work
out independently, or by the aid of more detailed accounts (sometimes
specifically referred to), the details of the dissection.

| 263

204 ELEMENTARY ZOOLOGY

the body is thickly covered with firm, hard sca/es, arranged
like the shingles on a roof. Remove one of these scales
and examine it under a hand lens. What sort of an edge
has it? Such a scale is said to be cfenord.

The body of the sunfish terminates behind a the
caudal fin, a series of cartilaginous rays connected by thin
skin and attached to a bony plate at the end of the back-
bone. Along the median dorsal line will be noted another
fin composed anteriorly of spines and posteriorly of soft
rays jointed and branched. This is the dorsal fin. How
many spines has it? Anterior to the caudal am on tic
ventral surface is a median unpaired anal fin. How many
spines has it? Anterior to the anal fin are the ventral
jins, while on the sides of the body back of the head in
a line with the mouth are found the pectoral fins. -The
ventral fins, attached to a rudimentary pelvis, correspond
to the hind legs of the other vertebrates. The pectoral
fins, attached to the shoulder girdle, correspond to the
arms. In front of the anal fin note a small pit-like open-
ing, the opening from the kidneys and reproductive organs,
and just anterior to this a large aperture, the azws. Atthe
anterior end of the head note the broad 7zou¢h, surrounded
by a complicated system of bones. Note the large eyes
surrounded by a series of small bones, the ordztal chaztn.
Just anterior to the eyes are two pairs of openings, one
pair of each side opening into a closed sac. What are
these openings? Note the presence of various bones on
the sideof the head, each: covered with asthmdaycs o:
skin. These are membrane bones, characteristic of fishes.
Are there any external ears.in the fish? Examine pein
side of the mouth. Is there a Zongue ? If so, of what char-
acter’? “Are there ¢ecti 7 Vf so, where are tney stsuaeed +

Note along each side.extending to the basejof the tail
a line of moditied scales, on each scale a little mucous
tube, the whole series constituting the /ateral line. Vhese

BRANCH CHORDATA; CLASS PISCES: THE FISHES 265

scales are intimately associated with a large nerve (the
vagus), and probably serve an important part, not yet
clearly understood, in the life of the fish.

Lift up the flap in front of one of the pectoral fins.
This is the opercular flap which covers the gills that lie
beneath. Bend this forward and find four ¢7/l-arches,
each with its double fringe of ez//s. Note the gz//-rakers,
short and blunt, on the first gill-arch. Note also on the
under side of the flaps turned back, delicate red gill-like
structures covered by a membrane. These are the false
gills or pseudo-branchie, \arger in most fishes than in the
sunfish. The gills in the fish subserve the same function
as the gills of the crayfish, that of purifying the blood
by eliminating carbonic-acid gas from it and taking up
oxygen from the air mixed with or dissolved in the water.
Organs subserving the same purposes in different kinds of
animals as, for example, the gills in fish and in crayfish,
are called analogous structures. But there is an important
morphological difference between the fish’s gills and the
gills of the crayfish. In the latter animal they are out-
growths of the basal segments of the walking-legs; in the
fish they are outgrowths from the alimentary canal. The
internal gills of the young toad (tadpole) arise in the same
way as those ofa fish. Structures which are identical in
their origin, like the gills of tadpole and fish, are called
homologous structures.

Make a drawing of the sunfish from a lateral aspect,
showing the external parts named.

Internal structure.—TrcunicaL NotTe.—Insert one point
of the scissors a little to one side of the anus and cut dorsally on the
left side of the body to the backbone. Now cut anteriorly from the
anus along the ventral wall to where the jaws unite, and cut, also
anteriorly, along the dorsal wall until the left side of the body can
be removed. Bend the opercular flap backward over the eye and
pin the entire fish, uncut side down, to the bottom of the dissecting-
pan, covering it with water.

266 ELEMENTARY ZOOLOGY

The above operation will have severed the large power-
ful muscles forming the body-wall and extending along
the sides. Note a membranous sac completely filling a
large dorsal cavity. This is the swzm-bladder, a float.
filled with air which tends to give the fish the same weight |
as the water it displaces. It arises as a diverticulum from
the alimentary canal, but soon becomes permanently shut
off from it. Beneath the swim-bladder is a large cavity
filled with various organs, collectively known as the
viscera. In vertebrate animals the cavity which contains
the viscera is generally called the perztoneal cavity. It is
lined by the ferztoneum, a delicate membrane, part of
which is deflected as the mesentery over the alimentary
canal and the other organs, thus suspending them all from
the dorsal wall. Note in the anterior end of the peritoneal
cavity a large bi-lobed gland, the “ver, red in fresh,
yellowish in alcoholic specimens. Its function, like that
of the liver of the toad, is to store up nutriment for the
blood and to secrete a digestive fluid called dz/e. Behind
the liver note a long, convoluted tube. What is this tube ?
Unfold this tube, separating it from its enveloping mem-
brane, the mesentery. Thrust a probe down the throat
and note that it passes into a thick-walled sac, the
stomach. Yhe mouth and gill-slts open into the front
part of the alimentary canal called the pharynx, which
leads by a short tube, the wsophagus, into the stomach.
Note the large, thickened portion of the alimentary canal
leading from the stomach. This is the pylorus, and to its
walls are attached a number of finger-like projections, the
pyloric ceca. The pyloric ceca secrete a fluid which is
poured into the alimentary canal and which assists in the
process of digestion somewhat as does the secretion from
the pancreas of the toad. From the pylorus, passing
backwards in one or two loops, is the s#zall intestine.
Trace this to its exit. Lying within the mesentery near

meee CHORDATA > CLASS PISCES :, THE FISHES 2067

the posterior end of the body-cavity note a small red
glandular mass, the spleen.

At the anterior end of the body in front of the liver
and between the sets of gills note the small perzcardial
cavity within which is contained the “eart. The peri-
cardial cavity is separated from the peritoneal cavity by
a thick muscular wall against which the liver abuts. The
heart consists of four parts. The posterior part is a thin-
walled reservoir, the szzus venosus, into which blood
enters through the jugular vein from the head and through
the cardinal vein from the kidney. From the sinus
venosus it passes forward into a large chamber, the
auricle. Next it flows into the wventrzcle, where, by the
contraction of the walls, rhythmical pulsations force it into
the conus arteriosus, thence into the ventral aorta, and
lastly into the gills, where it is purified. After passing
through the capillaries in the fine gill-flaments it is again
collected, now pure, by paired arteries from each pair of
gills, which arteries unite to form the dorsal aorta ex-
tending backward just below the backbone to the end of
the tail. From the dorsal aorta a pair of arteries, the
subclavian, are given off to the pectoral fins. At this
point two other arteries branch off ventrally, the first being
the cardiac artery, which distributes blood to the stomach
and pyloric ceca. The second divides into several long
mesenteric arteries supplying blood to all parts of the in-
testine and spleen. In the caudal region blood is taken
up through the caudal vem and carried forward to the
kidneys. These strain out the impurities arising from
waste of tissues, after which the blood is carried back to
the sinus venosus through the cardinal vein. From the
intestine it is gathered into the large portal vein as in the
toad. The portal vein carries blood to the liver, where
nutriment may be stored up, and from thence it flows back

268 ELEMENTARY ZOOLOGY

to the sinus venosus through a very short thin-walled
vessel, the “epatic sinus.

The £zdneys, more or less united in one mass, lie in the
posterior part of the body-cavity along the dorsal wall.
Note running from each side of the kidney a wreter which
unites with its fellow and opens into a small urinary
bladder which discharges through a small opening im-
mediately back of the anus.

The reproductive organs lie below the swim-bladder
near the posterior end of the body-cavity. Ifthe fish are
caught in the spring, the greater part of the body-cavity
of the female is found to be filled with smalleggs. When
mature, these eggs are deposited by the mother fish in the
gravel of the stream-bed where they are fertilized by the
sperm-cells poured over them by the male and left float-
ing in the water.

The nervous system of fishes is best studied in a speci-
men treated with nitric acid. Carefully remove the roof
of the skull, thereby exposing the brain. Most anteriorly
make out, as in the toad, the paired -of/adory doves.
These are attached by long stalks to the cerebrum or
forebrain, which is followed by two large hollow lobes,
the mzdbrain or optic lobes. Behind the midbrain is the
cerebellum. Following the cerebellum is. the elongate
medulla oblongata, which tapers backward into the spzzal
cord. How far backward does the spinal cord extend ?
On each side of the brain-case about opposite the cerebel-
lum are located the auditory organs, each consisting of
three semzcircular canals which lie in different planes, and
of the vestzbule. ‘These parts are filled with liquid, and
suspended in the liquid in the vestibule are small calcareous
bodies called ofoliths or ear-stones. Running out beneath
from the midbrain are the offic nerves, which cross, the
left one connected with the right eye, the right one with
the left eye. From each side of the medulla oblongata

BeaNCH CHORDATA; CLASS PISCES: THE FISHES 269

there is given off a large nerve, the vagus, which sends
branches to the lateral line organs on either side, and
extends backward to the stomach and viscera.

For further study of the nervous system see Parker's
Pe footomy, pp. 122-130.

Make a drawing of the nervous system as worked out.

TECHNICAL NOTE.—To make a good skeleton immerse a fresh
or preserved specimen for some time in a hot soap solution. When

the muscles have commenced to soften remnrve the body from the
solution, pick the flesh away, and leave to dry.

Note that the main axis of the sfelefon is composed of
vertebre placed end to end. How many vertebre are
teres Whaat vertebra bear +205? Ihe ribless ones
beyond the body-cavity are called caudal vertebrae. Note
the zuterspinal bones which support the fins, with large
muscles on either side to control their action. Note that
the group of bones supporting the pectoral fin is attached
to the back of the brain-case and makes up the shoulder
girdle. The ventral fins are attached to a rudimentary
pelvic girdle, attached in front to the shoulder girdle, as
the shoulder girdle is in turn attached to the skull. It
will be seen that the sunfish has no neck and we may say,
also, no back. Its skeleton consists only of a tail attached
to the skull. ‘The brain-case is made up of a number of
bones closely joined together. From it is suspended the
lower jaw, which comprises a number of bones but loosely
attached to each other. Overlying these is the system
of membrane bones already mentioned, including the
opercle or gill-cover. |

For a detailed study of the fish-skeleton see Parker’s
Pi eeromy. pp. o0—101, .-or yParker*+ and ~Haswell’s
we weleey:. vol..11. pp. -183=195:-

Life-history and habits.—The sunfish or ‘‘ pumpkin-
Eccd.) lives iy quiet corners. of the brooks and rivers,
preferably under a log or at the root of an old stump. It

27° ELEMENTARY ZOOLOGY

is a beautiful fish, shining ‘‘like a coin fresh from the
mint.’” Its body is mottled gelden, orange anit blue,
with metallic lustre, darker above, pale or yellowish
below. Its fins are of the same color. The up of its
opercle is prolonged like an ear and jet black in color,
with a dash of bright scarlet along its lower edge. Nearly
all the thirty species of sunfish found in the United States
have this black ear, but some have it long, some short,
and in some it is trimmed with yellow or blue instead of
scarlet.

The sunfish lays its eggs in the spring in a rude nest it
scoops in the gravel, over which it stands guard with its
bright fins spread, looking as big and dangerous as
possible. When thus employed it takes the hook savagely,
perhaps regarding the worm asa dangerous enemy. The
young fishes soon hatch, looking very much like their
parents, although more transparent and not so brightly
colored. They grow rapidly, feeding on insects and
other small creatures, and reach their growth in two or
three years. They do not wander far and never willingly
migrate. Students should verify this account on the
different species. A more exact study of the nests of the
different species and the fishes’ defence of them would be
a valuable addition to our knowledge. The most striking
traits of the habits of this fish are its vivacity and courage;
it reveals its great muscular strength when captured.
The sexes are similar in appearance and both defend the
nest alike.

OTHER FISHES:

Fishes constitute the largest class of vertebrate animals
and are to be found everywhere in ponds, streams, or
ocean. About 15,000 species of fish are known, of which
3,000 live in North America. ‘The largest of all fishes is
the basking shark (Cetorhinus), which reaches a length

gill-rakers

gall bladder

nostrils

pericardial cavity

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FIG. 112.—Dissectio:

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peel. CHORDAT a4; ‘CLASS’ PISCES: THE FISHES. -271

Bereity Six icet. The smallest is the dwarf: goby
(Wistichthys), \ess than half an inch long, found in Luzon,
one of the Philippine Islands. Between these extremes
is every variety in size, form, and relative proportions.
The body, for example, may be greatly elongated and
almost cylindrical as in the eels; or long and flattened
from side to side as in the ribbon-fishes; or the head may
be very large, wider and higher than the rest of the body
gs im tie aieliers, of May lave a ereat beak ds in ‘the
sword-fish.

Body form and structure.— When we consider the fish
as a whole, we find first a body formed for progression in
the water, the typical fish being pointed at each end (the
shorter point in front), and having the sides flattened, the
back and belly rather narrow, and the motive power
located in the fin onthe tail. From this typical form
diverge all conceivable variations, adaptations to every
sort of fish life.

Most fishes have the body covered with scales, although
many have the skin naked or covered with small scales
so hidden in the skin as to be hardly visible. The scales
are small horny or bony plates which fit into small pockets
or folds of the skin, and are usually arranged shingle-
fashion, overlapping each other. They are of various
shapes, mostly classified as of three kinds, namely, squarish
enamelled scales called ganoid, roundish smooth-edged
called cycloid, and roundish tooth-edged called ctenoid.

ee -keleton of the fish is relatively comptex.. Its
bones are comparatively soft, having little lime in thern,
Meco in maiy cases: they are mere. cattilace. The
vertebral column is made of twenty-four vertebrz in the
typical fishes, the number in the others being variously
increased, or sometimes diminished. These vertebre are
of two classes, abdominal or body, and caudal or tail
wertemre. “ihe former have a neural arch which encicses -

Rae. | ELEMENTARY ZOOLOGY

‘the spinal cord and from which projects a spine. Below,
the processes spread apart, surrounding the kidneys and
partly enclosing the air-bladder.. To these processes ribs
are loosely attached. The caudal vertebrze have no ribs
and leave no room below for viscera. Their lower arch
(hemal), similar to the dorsal (neural) arch, surrounds a
blood-vessel. The fins of a fish are composed of bony
rods or rays joined by membrane. Some of these rays
may be unbranched and unjointed, being then known as
spines, and usually occupy the. front part of the fin.
Other rays are made up of little joints and are usually
branched, toward their tip. Such owes age sealiee same
rays. Soft rays make up the greatest part of most fins.
The vertical fins-are on the middle lme ot the fody.
These are the dorsal above, anal below, and caudal form-
ing the end of the tail. The paired pectoral and ventral
fins are ranged one on each side corresponding to the
arms and legs of higher animals. The pectoral fin or
arm is fastened toa series of bones called the shoulder
girdle. These bones do not correspond to those in the
shoulder girdle of the higher animals, and the various
parts in the two structures are differently named. The
uppermost bone of the shoulder girdle is usually attached
to the skull. To the lowermost is attached the rudimen-
tary pelvis, which supports the hinder limb or ventral fin.
Usually the pelvis is farther back and loose in the flesh,
but sometimes it is placed far forward, being occasional! ,
attached at the chin.

The head contains the various bones of the cranium,
usually closely wedged together and not easily distin-
guished. The jaws are each made of several pieces; the
lower one is suspended from the skull by a chain of three
flat bones. The jaws may bear any one of a great variety
of forms of teeth or no teeth at all, and any of the bones
of the mouth-cavity and throat may have teeth as well.

BRANCH CHORDATA; CLASS ISCES Te IJASAES 273

On the outside of the head are numerous bones called
membrane bones, because they are made up of ossified
membrane. The most important of these is the opercle
or gill-cover. Within are the tongue with the five gill-
arches attached to it below and to the floor of the skull
above, the last arch being usually modified to form the
pharyngeal jaw.

The stomach may be a blind sac with entrance and exit
close together, or it may have the form of a tube or
siphon. At its end are often found the large glandular
tubes called pyloric ceca which secrete a digestive fluid ;
and to its right side is attached the red spleen. The liver
is large, having usually, but not always, a gall-bladder ;
it pours its secretion into the upper intestine. In fishes
which feed on plants the intestine is long, but it 1s short
in those which eat flesh, because flesh is digested in the
stomach, not in the intestines. The kidney is usually a
long slender forked gland showing little variation. The
egg-elands differ greatly in different sorts of fishes, the size
and number of eggs varying equally. The air-bladder is
a lung which has lost both lung structure and respiratory
function, being simply a sac filled with gas secreted from
the blood, and lying in the upper part of the abdominal
cavity. It is subject to many variations. In the gar
pike, bow-fin and the lung-fishes of the tropics, the air-
bladder is a true lung used for breathing and connected
by a sort of glottis with the cesophagus. In others it is
rudimentary or even wholly wanting, while in still others
its function as an air-sac is especially pronounced, and in
many it is joined through the modified bones of the neck
to the organ cf hearing.

The blood of the fish is purified by circulation through
its gills. These are a series of slender filaments attached |
to bony arches. Among them the blood flows in and out,
coming in contact with the water which the fish takes in

274 ELEMENTARY ZOOLOGY

through its mouth and which passes across the gills to be
expelled through the gill-openings. The blood is received
from the body into the first chamber of the heart, a mus-
cular sac called the auricle. From here it passes into the
ventricle, a chamber with thicker walls, the contraction
of which sends it to the gills, thence without return to the
heart it passes over the body. The circulation of blood
in fishes is slow, and the blood, which receives relatively
little oxygen, is cold, being but little warmer than the
water in which the individual fish lives.

Inside the cranium or brain-case is the brain, small and
composed of ganglia which are smooth at the surface and
contain little gray matter. At the posterior end of the
brain is the thickened end of the spinal cord, called the
medulla oblongata. Next overlapping this is the cere-
bellum, always single. Before this lie the largest pair of
ganglia, the optic lobes or midbrain, round, smooth, and
hollow. From the under side of these, nerves run to the
eyes with or without a chiasma or crossing. In front of
the optic lobes and smailer than them is the cerebrum or
forebrain, usually of two ganglia but sometimes (in the
sharks) united into one. “In front of these are the small
olfactory lobes which send nerves to the nostrils.

The sense organs are well developed. The sense of
touch has in some fishes special organs for its better
effectiveness. For instance certain fin-rays in some
fishes, or, as in the catfish, slender, fleshy, whip-like
processes on the head, are developed as feelers or special
tactile organs. Other fishes, the sucker and loach for
example, have specially sensitive lips and noses with
which they explore their surroundings. The sense of
taste does not seem to be well developed in this group.
_ Taste-papille are often present in small numbers on the
tongue or on the palate. The sense of smell is good.
The olfactory organs, one on each side of the head, are

BRANCH CHORDATA; CLASS PISCES: THE FISHES 275

hollow sac-like depressions, closed at the rear. In most
cases each sac has two openings or nostrils. The sense
of hearing is not very keen. The ears are fluid-filled sacs
buried in the skull, and without external or (except ina
few cases) internal opening. Fishes are far more sensi-
tive to sudden jars or sudden movements than to any
sound. They possess what is generally believed to be a
special sense organ not found in other animals. This is
the lateral line which extends along the sides of the body
and which consists of a series of modified scales (each orie
with a mucous channel) richly supplied with nerves. The
eyes are usually large and conspicuous. They differ
mainly from the eyes of other vertebrates in their myopic
spherical crystalline lens, made necessary by the density
of the medium in which fishes live. There are usually no
eyelids, the skin of the body being continuous but trans-
parent over the eyes. Being near-sighted, fishes do not
discriminate readily among forms, their special senses
fitting them in general to distinguish motions of their
enemies or prey rather than to ascertain exactly the
nature of particular things.

The colors of fishes are in general appearance protec-
tive. Thus most individuals are white on the belly,
mimicking the color of the sky to the enemy which
pursues them from below. Seen from above most of them
are greenish, like the water, or brownish gray and
mottled, like the bottom. Those that live on sand are
sand-colored, those on lava black, and those among rose-
red sea-weeds bright red. In many cases, especially
among kinds that are protected by their activity, brilliant
colors and showy markings are developed. This is
especially true among fishes of the coral reefs, though
species scarcely less brilliant are found among the darters
of our American brooks.

Among fresh-water fishes bright colors, crimson,

276 ELEMENTARY ZOOLOGY

scarlet, blue, creamy white, are developed in the breeding
season, the then vigorous males being the most highly
colored. Many of the feeble minnows even become very
brilliant in the nuptial season of May and June. Color in
fishes is formed by minute oil-sacs on the scales, and it
often changes quickly with changes in the nervous condi-
tion of the individuals.

Development and life-history.—The breeding habits
of fishes are extremely varied. Most fishes do not pair,
but in some cases pairing takes place as among higher
animals. Ordinarily fishes lay their eggs on the bottom in
shallow water, either in brooks, lakes, orin the sea. The
eggs of fishes are commonly called spawn, and egg-laying
is referred to as spawning. The spawn of some fishes is
esteemed a special food delicacy. Spring is the usual time
of spawning, though some fishes spawn in summer and
some even in winter; generaily they move from their usual
haunts for the purpose. The eggs of the different species
vary much in size, ranging from an inch and a half in
diameter (barn-door skate) down to the tiniest dots, like
those of the herring. The number of eggs laid also varies
greatly. «The trout lays. from 500 to 1,;0@0, Thexsaiman
about 10,000, the herring 30,000 to’ 40,006, aneesome
Species of river fish .500;000,- while certain founders,
sturgeons, and others each lay several millions of eggs.
The adults rarely pay any attention to the eggs, which are
hatched directly by the heat of the sun or by heat absorbed
from the water. The length of incubation varies much.
When the young fish leaves the egg-shell it carries, in the
case of most species, a part of the yolk still hanging to
its body. Its eyes are very large, and its fimseanemnepre—
sented by thin strips of membrane. It usually undergoes
no great changes in development from the first, resembling
the adult except in size,. But some of the o¢eagemsces

-

BRANCH CHORDATA; CLASS PISCES: THE FISHES 277

show a metamorphosis almost as striking as that of insects
or toads or frogs.

Some fishes build nests. Sticklebacks build elaborate
nests in the brooks and defend them with spirit. Sun-
fishes do the same, but the nests are clumsier and not
so well cared for.

The salmon is the type of fishes which run up from the
sea to lay their eggs in fresh water.. The king salmon of
the Columbia River, for example, leaves the sea in the
high waters of March and ascends without feeding for over |
a thousand miles, depositing its spawn in some small
brook in the fall. After making this long journey to lay
the eggs, the salmon become much exhausted, battered
and worn, and are often attacked by parasitic fungi. They
soon die, probably none of them ever surviving to lay eggs
a second time. 3

Classification.— A fish is an aquatic vertebrate, fitted
to breathe the air contained in water, and never develop-
in@ fingers and toes. Accepting this broad general
definition we find at once that there are very great differ-
ences among fishes. Some differ more from others than
the ordinary forms differ from rabbits or birds. So
although we have entitled this chapter as if all fishes
belonged to the class Pisces, we cannot arrange them
satisfactorily in less than three classes.

The lancelets (Leptocardii).— The lowest class of fish-
ise aoanals is that of the lancelets, the Leptocardii.
These little creatures, translucent, buried in the sand, of
the size and form of a small toothpick, are fishes reduced
to their lowest terms. They have the form, life, and ways
of a fish, but no differentiated skull, brain, heart, or eyes.
Moreover they have no limbs, no Jaws, no teeth, no
scales. The few parts they do have are arranged as ina
fish, and they show something in common with the fish

278 ELEMENTARY ZOOLOGY

embryo. Lacking a distinct head, the lancelets are put
by some zoologists in a group called the Acrania, as
opposed to the Craniata, which includes ali the other
vertebrates. Lancelets have been found in the North
Atlantic and Mediterranean, on the west coast of North
America, on the east coast of South America and on the
coasts of Japan, Australia, New Zealand, the East Indies
and Malayan Islands. The best-known members of the
group belong to the genus Amphzorus. There are but
one to two other genera in the class.

The lampreys and hag-fishes (Cyclostomata).—The

next class of fish-like animals is that of the lampreys (fig.

Fic. 113.—A lamprey, Petromvzon marinus. (After Goode.)

113) and hag-fishes, the Cyclostomata. The lampreys
and hags are easily distinguished from the true fishes by
their sucking mouth without jaws, their single median
nostril, their eel-like shape and lack of lateral appendages
or paired fins. The hag-fishes (A/yxime), which are
marine, attach themselves by means of a sucker-like mouth
to living fishes (the cod particularly), gradually scraping
and eating their way into the abdominal cavity of the fish.
These hags or ‘‘borers’’ ‘‘approach most nearly to the
condition of an internal parasite of any vertebrate.’’ The
lampreys, or lamprey-eels as they are often called because
of their superficial resemblance to true eels, are both
marine and fresh-water in their habitat, and most of them
attach themselves to live fishes and suck their blood.
They also feed on crustacea, insects, and worms. The

BRANCH CHORDATA; CLASS PISCES: THE FISHES 279

brook-lamprey, Lampetra wildert, is never parasitic. It
reaches its full size in larval life and transforms simply
for spawning. The sea- and lake-lampreys ascend small
fresh-water streams when ready to lay their eggs, few
living to return. Sometimes small piles of stones are
made for nests. The young undergo a considerable
metamorphosis in their development. The largest sea-
lampreys reach a length of three feet. The common
brook-lampreys are from eight to twelve inches long only,

The true fishes (Pisces).— All the other fish-like ani-
mals are grouped in the class Pisces. They are charac-
terized, when compared with the lower fish-like forms just
referred to, by the presence of jaws, shoulder girdle, and
pelvic girdle. The class includes both the cartilaginous
and bony fishes, and is divided into three sub-classes,
namely, the Elasmobranchu, including the sharks, rays,
skates, torpedoes, etc., the Holocephali, including the
chimeras (a few strange-bodied forms), and the Teleos-
tomi, including all the other fishes, as the trout, catfishes,
darters, bass, herring, cod, mackerel, sturgeons, etc., etc.

The sharks, skates, etc. (Elasmobranchii). — The
sharks and skates are characterized by the possession of
a skeleton composed of cartilage and not bone, as in
the bony fishes; they have no operculum; their teeth
are distinct, often large and highly specialized, and their
eggs are few and very large. There are two principal
eroups among Elasmobranchi, viz., the sharks, which
usually have an elongate body, and always have the gill-
openings on the sides, and the rays or skates, which have a
broad flattened body with the gill-openings always on the
under side. All the members of both groups are marine.
The sharks are active, fierce, usually large fishes, which
live in the surface-waters of the ocean and make war on
other marine animals, all of the species except half a
dozen being fish-eaters. The shark's mouth is on the

280 . ELEMENTARY ZOOLOGY

under side of the usually conical head, and the animal
often turns over on its back in order to seize its prey.
The largest American sharks, and the largest of all fishes,
are the great basking-sharks (Cetorfinus), which reach a
length of nearly forty feet. They get their name from
their habit of gathering in numbers and floating motion-
less on the surface. They feed chiefly on fishes.

The hammer-headed sharks (Sphyrnua) are odd sharks
which have the head mallet or kidney shaped, twice as wide
as long, the eyes being situated on the ends of the lateral
expansions of the head. The man-eating or great white
sharks (Carcharodon) are nearly as large as the basking-
sharks, and are extremely voracious. They will follow
ships for long distances for the refuse thrown overboard.
They do not-hesitate to attack man? amengeune morc
familiar smaller sharks are the dog-fishes and sand-sharks
of our Atlantic coast. 3

The rays and skates are also carnivorous, but are with
few exceptions sluggish, lying at the bottom of shallow
shore-waters. They feed on crabs, molluscs, and bottom-
fishes. The-small common skates, ‘‘ tobacco-boxes ’’
(Raja erinacea) (fig. 114), about twenty inches long, and
the larger ‘‘barn-door skates’’ (A. /evzs), are numer-
ous along the Atlantic coast from Virginia northward.
specially interesting members of this group, because of
the peculiar character of the injuries produced by them,
are the sting-rays and torpedoes or electric-rays. The
sting-rays (Dasyatis) have spines near the base of the tail
which cause very painful wounds. The torpedoes (Varczne)
have two large electrical organs, one on each side of the
body just behind the head, with which they can give a
strong electric shock. ‘‘ The discharge from a large in-
dividual is sufficient to temporarily disable a man, and
were these animals at all numerous they would prove

dangerous to bathers.’’ Very different from the typical

BRANCH CHORDATA; CLASS PISCES: THE FISHES 281

rays in external appearance are the saw-fishes (Prst7s
pectinatis), which belong to this group. The body is
elongate and shark-like, and has a long saw-like snout.
This saw, which in large individuals may reach a length
of six feet and a breadth of twelve inches, makes its
owner formidable among the small sardines and herring-

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Fic. 114.—The common skate, Raya erinacea. (From Kingsley.)

like fishes on which it feeds. The saw-fishes live in tropi-
cal rivers, descending to the sea.

The bony fishes (Teleostomi).—The bony or true fishes
are distinguished from the lampreys and sharks and rays
by having in general the skeleton bony, not cartilaginous,
the skull provided with membrane bones, and the eggs
small and many. In this group are included all the
fishes of our fresh-water lakes, ponds, and streams as well
as most of the marine forms. Fish life, being spent under

282 ELEMENTARY ZOOLOGY

water, is not familiar to most of us, and beginning students
are rarely helped enough in getting acquainted with the
different kinds and the interesting habits of fishes. But
they offer a field of study which is really of unusual interest
and profit. We can refer in the following paragraphs to
but few of the numerous common and readily found kinds,
and to these but briefly.

Closely related to the sunfish, studied as example of
the bony fishes, are the various kinds of bass, as the
‘crappie’ (Pomoxts annularis), the calico bass (P. sepa-
rowdes), the rock-bass (Ambloplites rupestris) and the
large-mouthed and small-mouthed black bass (Ucropterus
salmoides and M. dolomieu respectively). All the mem-
bers of this sunfish and bass family are carnivorous fishes
especially characteristic of the Mississippi valley.

Another family of many species especially common in
the clear, swift, and strong Eastern rivers is that of the
darters and perches. The darters are little slender-bodied
fishes which he motionless on the bottom, moving like a
flash when disturbed and slipping under stones out of sight
of their enemies. Some are most brilliantly colored, sur-
passing in this respect all other fresh-water fishes.

Unlike the sunfishes and darters are the catfishes,
composing a ‘great family, the-Siluridze. Wwe eattich
(Ameiurus) gets its name from the long feelers about its
mouth; from these feelers also come its other names of
herned pout, or bull-head. It has no scales, but its spines
are sharp and often barbed or jagged and capable of mak-

ing a severe wound.

Kemotely allied to the catfish are the suckers, min-
nows, and chubs, with smooth scales, soft fins and soft
bodies and the flesh full of small bones. ‘These little fish
are very numerous in species, some kinds swarming in
all fresh water in America, Europe, and Asia. They
usually swim in the open water, the prey of every carniv-

Beane CHORDATA: CLASS PISCES: THE FISHES 283

orous fish, making up by their fecundity and their insig-
nificance for their lack of defensive armature. In some
species the male is adorned in the spring with bright
pigment, red, black, blue, or milk-white. In some cases,
too, it has bony warts or horns on its head or body. Such
forms are known to the boys as horned dace.

Most interesting to the angler are the fishes of the
salmon and trout (fig. 115) family, because they are gamy,

Fic. 115.—The rainbow-trout, Salmo trt.ens. (From specimen.)

beautiful, excellent as food and above all perhaps because
they live in the swiftest and clearest waters in the most
charming forests. The salmon live in the ocean most of
their life, but ascend the rivers from the sea to deposit
their eggs. The king salmon (Oxcorhynchus tschawy-
tscha) of the Columbia goes up the great river more than
a thousand miles, taking the whole summer for it, and
never feeding while in fresh water. Besides the different
kinds of salmon, the black-spotted or true trout, the charr
or red-spotted trout of various species, the whitefish
(Coregonus), the grayling (Thymallus signifer) and the
famous ayu of Japan belong to this family.

In the sea are multitudes of fish forms arranged in many
families. The myriad species of eels agree in having no
ventral fins and in having the long flexible body of the
snake. Most of them live in the sea, but the single

284 ELEMENTARY ZOOLOGY

genus (Anguilla) or true eel which ascends the rivers is
exceedingly abundant and widely distributed. Most eels
are extremely voracious, but some of them have mouths
that would barely admit a pin-head. The codfish (Gadus
callarias) is a creature of little beauty but of great useful-
ness, swarming in all arctic and subarctic seas. The

¢

ae:

Fic. 116.—The winter flounder, Pseudopleuronectes americanus.
(After Goode. )

herring (Clupea harengus), soft and weak in body, are
more numerous in individuals than any other fishes. The

flounders (fig. 116) of many kinds lie flat on the sea-
bottom. They have the head so twisted that the two

eyes occur both together -on.the ‘uppermost side. Ee
members of the great mackerel tribe swim in the open
sea, often in great schools. Largest and swiftest of these
is the sword-fish (Azpizas gladius), in which the whole
upper Jaw is grown together to form a long bony sword,
a weapon of offence that can pierce the wooden bottom
of a boat.

Many of the ocean fishes are of strange form and ap-
pearance. The sea-horses (//zppocampus sp.) (fig. 117)
are odd fishes covered with a bony shell and with the
head having the physiognomy of that of a horse. They
are little fishes. rarely a foot.long, and clingey phe:

BRANCH CHORDATA > CLASS PISCES: THE FISHES 285

curved tails to floating seaweed. The pipefish (Syz-
gnathus fuscum) is a sea-horse straizhtened out, The
porcupine-fishes and swellfishes (Tetraodontide) have the
power of filling the stomach
with air which they gulp from
the surface. They then escape
from their pursuers by floating
asea sound. spiny ball on:-the
surface. The flying-fishes (£-r0-
cvtus) leap out of the water and
sail for long distances through
the air, like grasshoppers. [hey
cannot flap their long pectoral
fae aace- do not truly, fly;
nevertheless they move swiftly
through the air and thus escape
thet, pursuers. In its structure
a flying-fish differs little from a
pike or other ordinary fish.

For an account of the fishes
er , Neri America .see Jor-
dan’s ‘‘ Manual of Vertebrates, ’’
eighth edition, pp. 5-173, and ——_ |
Jordan and Evermann’s ‘‘ Fishes Ss Rr os res a aie
of North and Middle America,’’ Goode.)
where the 3.127 species known from our continent are
described in detail with illustrative figures.

Habits and adaptations.—The chief part of a fish’s life
isea@eveiecd to eatinc, and as most fishes feed on other

fishes, all are equally considerably occupied in providing
for their own escape.

In general the provisions for seizing prey are confined
to sharp teeth and the strong muscles which propel the
ecaudal- tn: § But in some cases special contrivances
appear. In one large group known collectively as the

286 ELEMENTARY ZOOLOGY

‘‘anglers’’ the first spine of the dorsal fin hangs over the
mouth. It has at its tip a fleshy appendage which serves ©
as a bait. Little fishes nibble at this, the mouth opens,
and they are gone. In the deep seas, many fishes are
provided with phosphorescent spots or lanterns which
light up the dark waters, and enable them to see their
prey. In storms these lantern-fishes sometimes lose their
bearings and are thrown upward to the surface.

In general the more predatory in its habits any fish is
the sharper its teeth, and the broader its mouth. Among
brook-fishes the pickerel has the largest mouth and the
sharpest teeth. It has been called a ‘‘mere machine for
the assimilation of other organisms.’’ The trout has a
large mouth and sharpteeth. It is a swift, voracious, and
predatory fish, feeding even on its own kind. The sunfish
is less greedy and its mouth and teeth are smaller, though
it too eats other fish.

As means of escape, most fishes depend on their speed
in swimming. But some hide among rocks and weeds,
disguising themselves by a change in color to match their
surroundings. Others, like the flounders and skates, lie
flat on the bottom. Still others retreat to the shallows
or the depths or the rock-pools or to any place safer than
the open sea. Some are protected by spines which they
erect when attacked. Some erect these spines only after
they have been swallowed, tearing the stomach of their
enemy and killing it, but too late to save themselves.
Again in some species the spines are armed with poison
which benumbs the enemy. Sometimes an electric battery
about the head or on the sides gives the biting fish a
severe shock and drives him away. Such batteries are
found in the electric rays or torpedo, in the electric eel
of Paraguay, the electric catfish of the Nile, the electric
stargazer and other fishes.

Some fishes are protected by their poor and bitter 2.4,

BRANCH CHORDATA; CLASS PISCES: THE FISHES - 287

Some have bony coats of mail and sometimes the coat of
mail is covered with thorns, as in the porcupine-fish.
This fish and various of its relatives have the habit of filling
the stomach with air when disturbed, then floating belly
upward, the thorny back only within reach of its enemies.

Many species (cling fishes) attach themselves to the
rocks by a fleshy sucking-disk. Some (Remora) (fig. 118)
cling to larger fishes by a strange sucking-disk on the head,
a transformed dorsal fin, being thus shielded from the

Fic. 118.—The remora, or cling fish, Remoropsts brachyptera. Note sucker
on top of head. (After Goode.)

attacks of fish smaller than their protectors. Some small
fishes seek the shelter of the floating jellyfishes, lurking
among their poisoned tentacles. Others creep into the
masses of floating gulf-weed. Some creep into the shell

of clams and snails. In the open channel of a sponge,
the mouth of a tunicate and in similar cavities of various

animals, little fishes may be found. <A few fishes (hag-
fishes) are parasitic on others, boring their way into the
body and devouring the muscles with their rasp-like
teeth.

Some fishes are provided with peculiar modifications of
the gills which enable them to breathe for a time out of
water. Such fish have the pectoral fins modified for a
rather poor kind of locomotion on land, thus enabling
them to move from nond to pond or from stream to stream.
In cold climates the fishes must either migrate to warmer
latitudes in winter, as some do, or withstand variously the
cold, often freezing weather. Some fish can be frozen

288 ELEMENTARY ZOOLOGY

solid, and yet thaw out and resume active living. Some
lie at the bottoms of deep pools through the colder periods,
while many others, such as the minnows, chubs, and
other kinds common in small streams, bury themselves in
the mud, and lie dormant or asleep through the whole
winter. On the other hand in countries where the long
intense rainless summers dry up the pools, some fishes
have the habit of burying themselves in the mud, which,
with slime from the body, forms about them a sort of tight
cement ball in which they lie dormant until the rains
come.. ‘‘ Thus a lung-fish (called Protopterus), found in
Asia and Africa, so completely slimes a ball of mud
around it that it may live for more than one season, per-
haps many; it has been dug up and sent to England, still
enclosed in its round mud-case, and when it was placed
in warm water it awoke as well as ever.’’

Food-fishes and fish-hatcheries.— Most fishes are suit-
able for food, though not all. Some are too small to be
worth catching or too bony to be worth eating. Some
of the larger ones, especially the sharks, are tough and
rank. .A-few are bitter and in the tropics a mmmsce o1
species feed on poisonous coelenterates about the coral
reefs, becoming themselves poisonous inturn. Buta fish is
rarely poisonous or unwholesome unless it takes poisonous
food. Where fishes of a kind specially used for food gather
in great numbers at certain seasons of the year, fishing is
carried on extensively and with an elaborate equipment.
Such fisheries, some of which have been long known, are
scattered all over the world. Along the sheres of the
Mediterranean Sea, and on the coasts of Norway, France,
the British Isles and Japan are numerous great fishing-
places. But ‘‘nowhere are there found such large fisheries
as those along the northern Atlantic coasts of our own
continent, extending from Massachusetts to Labrador.
Especially on the banks of Newfoundland are codfish,

Beemer CHORDATA: CLASS PISCES: THE FISHES 2809

herring, and mackerel caught.’’ Among our fresh-water
fisheries the great salmon fisheries of the Penobscot and
Columbia rivers and of the Karluk and other rivers of
Alaska are the best known. The whitefish of our Great
Lakes is also one of the important food-fishes of the world.

In many places fishes are raised in so-called hatcheries,
not usually for immediate consumption but for the purpose
of stocking ponds and streams either in the neighborhood
of the hatchery or in distant waters which the special
species cultivated has not been able naturally to reach.
The eggs of some fishes are large and non-adherent, two
features which greatly favor artificial impregnation and
hatching. In the hatcheries the eggs are put first into
warm water, where development begins; they are then
removed into cool water, which arrests development with
out injury, making shipment possible. The eggs of
salmon and trout in particular can be sent long distances
to suitable streams or ponds. The eggs of the shad have
been thus carried from the East to the streams of Cali-
fornia and trout have been distributed to many streams in
our country which by themselves they could never have
reached.

The salmon is a conspicuous example of those fishes
which can be artificially propagated. The eggs of the
salmon are large, firm, and separate from each other. If
the female fish be caught when the eggs are ripe and
her body be pressed over a pan of water the eggs will
flow out into the water. Bya similar process the milt or
male sperm-cells can be procured and poured over the
eggs to fertilize them. The young after hatching are kept
for a few days or weeks in artificial pools, till the yolk-
~sacs are absorbed and they can take care of themselves.
They are then turned into the stream, where they drift tail
foremost with the current and pass downward to the sea.
All trout may be treated in similar fashion, but there are

290 ELEMENTARY ZOOLOGY

many food-fishes which cannot be handled in this way.
In some the eggs are small or soft, or viscid and adhering
in bunches. In others the life-habits make artificial fer-
tilization impossible. Such species are artificially reared
only by catching the young and taking them from one
stream to another. To this type belong the black bass,
the sunfish, the catfish and other familiar forms.

CHAPTER “XXV

PrmeAaNCH CHORDATA. (Contznued).. CLASS BA-
TimeACHIA: THE BATRACHIANS

THE structure, life-history, and habits of the garden-
toad (ufo lentiginosus) have already been studied (see
Chapter II and Chapter XII).

GTHER BATRACHIANS.

The class Batrachia includes the animals familiarly
known as ccecilians, sirens, mud-puppies, salamanders,
toads, and frogs. Although differing plainly from fishes
in appearance and habits, the batrachians are really closelv
related to them, resembling them in all but a few essential
Giatacters. | -umone ‘the distinctive ‘characters. of ba-
trachians may be noted the absence of fins supported
by fin-rays, the presence usually of well-developed legs
for walking or leaping, and the absence or reduction of
certain bones of the head connected with the gills and
lower jaw and which are well developed in the fishes.
The batrachians stand in somewhat intermediate position
between the fishes and the reptiles, showing some of the
Siatacters of both. They are, like fishes and reptiles,
cold-blooded. In their adult condition some are terres-
trial and some aquatic as to habitat, but all have an aquatic
larval life. The water-inhabiting young breathe at first
_ by means of gills, later lungs begin to develop, and for a
time both gills and lungs are used in respiration. Finally

in the adult condition in almost all of the forms the gills
291

292 ELEMENTARY ZOOLOGY

are wholly lost and breathing is done by the lungs and
skin solely. Correlated with the change of habits from
larval to adult stage there is usually a well-marked meta-
morphosis in post-embryonic development. This meta-
morphosis is specially striking among the frogs and toads.
None of the aquatic forms is marine, salt water always
killing eggs, larve or adults. Batrachians are found all
over. the world, although there are"few in twee esareme
North. They are most abundant in warm and tropical
lands.

Body form and organization.— The body varies from
a long and slender, truly snake-like form as in the tropical
coecilians through the usual salamander (fig. 119) shape,
where it is more robust but still elongate and tailed, to
the heavy, squat, tailless condition of the toads. Legs,

. sei ei | ie
Cae aia we ae
: ae Ons NS et any rN
Senn i ait rae Ve
vey

Fic. 119.—The tiger salamander. (From Jenkins and Kellogg.)

with five digits, are usually present, and are used for
swimming, walking, or leaping. The legs are longest
and best developed in the short tailless frog and toad
forms which are mostly terrestrial, and are short and weak
in the tailed salamander forms, many of which are aquatic.
The skin is almost always naked, showing a marked differ-
ence from the scaled condition of reptiles and most of the
fishes, and its cells secrete a slimy, sticky, usually whitish
fluid, which in some cases is irritating, or even poisonous.

BRANCH CHORDATA: CLASS BATRACHIA 293

The skin is sometimes thrown up into folds or ridges, and
in some species is elevated to form a kind of fin on the
tail or back. This unpaired fin differs from the dorsal fin
(and other fins) of fishes in not being supported by rayed
processes of the skeleton. There are in some batrachians
traces of an exoskeleton in the presence of scale-like
structures in the skin or in the horny nails on the digits,
but these cases are rare. The skin contains pigment-cells
and many of the batrachians are brilliantly colored and
patterned; some of the pigment is carried by special con-
tractile or expansile cells, the chromatophores (see
account of chromatophores of the Cephalopoda, p. 256),
so that the animal can change its tint and markings more
or less rapidly. All the batrachians possess external gills
in their aquatic larval stage, and in a few forms, as the
sirens and mud-puppies, gills are retained all through life.
These gills are branched folds of the skin abundantly
supplied with blood-vessels.

In the organization of the batrachian body the usual
vertebrate characters appear, the body-organs being
arranged with reference to a supporting and protecting
internal bony skeleton. The head is plainly set off from
the rest of the body and bears the mouth and the organs
of hearing and sight. Certain so-called lateral sense
organs, the function of which is not exactly known, occur
arranged in three lines on each side of the body of some
of the forms. Both pairs of limbs are present and func-
tional in almost all of the species. In the ccecilians the
limbs are wholly wanting; in the sirens only the fore legs
are present.

Structure.—The most obvious skeletal differences
among batrachians are those due to variations in external
form. While there are as many as 100 vertebrz in some
of the elongate long-tailed salamanders (even 250 in the
strange snake-like coecilians), there are but 10 (the last

204 ELEMENTARY ZOOLOGY

or tenth being the rod-shaped bone called the urostyle)
in the short, tailless frogs and toads. To any of the
vertebra except the first (the single cervical vertebra) and
the last, ribs may be attached and the ceecilians have
about as many pairs of ribs as vertebre. In the frogs
and toads, however, the ribs are lost. In any case they
are never fastened by their lower ends to the breast-bone. |

The alimentary canal is usually not much longer than
the body and is plainly divided into mouth, pharynx,
cesophagus, small intestine, large intestine or rectum,
and anal opening. The teeth when present occur on both
the jaws and the palate. They are small, sharp, point
backward and are~-fused to the bones. They are wholly
wanting in the toad and in some other allied forms. The
tongue may be wanting, or may be immovably fixed to
the floor of the mouth, or as in the frogs, fastened at its
front end but free behind, so that the hinder end can be
protruded far from the mouth for the purpose of catching
insects.

The organs of respiration are gills, external and in-
ternal, lungs, trachea or windpipe, and the skin. In the
earliest larval stages all batrachians have gills; later, in
most cases, the gills become reduced and disappear, while
at the same time lungs are developing. In some sala-
manders the lungs never develop, but the animals, in their
adult stage, breathe wholly by means of the skin. Ina
few cases, as in the siren and mud-puppies, gills are
retained through the whole life, although lungs are also
present in the adult stage. The lungs are two in number,
a right and a left lung, and are simple sacs with the walls
more or less folded or thrown into ridges and richly sup-
plied with blood-vessels. The front end of the lungs
opens directly into the pharynx or, in the more elongate
batrachians, is connected with it by a tubular trachea or
windpipe. In the frogs and toads there are vocal cords

BRANCH CHORDATA: CLASS BATRACHIA 295

stretched across the short windpipe; the vibration of
these cords produces the croaking.

The heart is always three-chambered, consisting of the
right and left auricles and a single ventricle. The circu-
lation of the more generalized salamanders like the mud-
puppies is essentially like that of a fish. In the frogs and
toads there is a distinct advance beyond this condition.
The red corpuscles of the blood are oval in shape and are
the largest found among any of the vertebrates.

In the nervous system the small size of the hindbrain
or cerebellum is noticeable. The sense organs are fairly
well developed. The skin of the whole body is provided
with tactile nerve-endings. There are special taste organs
on the lining membrane of the tongue and mouth-cavity.
The eyes have no lids in some of the lower forms; most
of the frogs and toads have an upper lid but no under one,
although a thin membrane, called the nictitating mem-
brane, arises from the lower margin of the eye and can be
drawn up over it. The ears have no external parts, other
than the thin tympanic membranes. The nostrils of frogs
and toads can be closed by the contracticn of certain
special muscles.

Life-history and habits.—The sexes are distinct, and in
most cases the young hatch from eggs. <A few of the sala-
manders give birth to free young. The eggs are usually in
strings or chains enclosed in a clear gelatinous substance ;
these chains of eggs are either simply dropped into the
water or are fastened to water-plants. The young, called
tadpoles (fig. 120), in their earlier larval stages are ex-
tremely fish-like in character, long-bodied, tailed, swim-
ming freely about by means of the fin-like flattened tail, and
breathing by means of external gills. Nor do they show
any sign of legs. As the tadpoles grow and develop the
legs begin to appear, the hind legs first in the frogs and
toads, the fore legs first in the salamanders; lungs develop

296 ELEMENTARY ZOOLOGY

and the gills disappear (except in the cases of the few forms
which retain gills through life). The tail shortens and
finally disappears in the frogs and toads; with the salaman-
ders the tail-fin only is lost. Atthe same time the change
from water to land is made. Further growth is very

Fic. 120.—Tadpoles. (Photograph from life by Cherry Kearton; per-
mission of Cassel & Co.)

slow; frogs are not really adult, that is, capable of pro-
ducing young, until they are five years old, and they may
continue to increase in size until they are ten years old.
The food of the adult batrachians is almost exclusively
small animals, particularly insects and worms. Crus-
taceans, snails, and young fish are also eaten. The tad-
poles also eat vegetable matter. Almost all batrachians
are nocturnal in habit, remaining concealed by day. In
the zones in which cold winters occur they hibernate or
pass the winter in a torpid condition, or state of ‘‘ sus-
pended animation,’’ or, as it is said, they sleep through
the winter. Frogs burrow into the mud at the bottom of
ponds at the approach of winter and come forth early in

BRANCH CHORDATA: CLASS BATRACHIA 297

the spring to lay their eggs. Most batrachians are very
tenacious of life, being able to withstand long periods of
fasting and serious mutilation, and most of them can
regenerate certain lost parts, such as the tail or legs.

Classification, —The living Batrachia are divided into
three orders, viz., the Urodela, including the sirens, mud-
puppies, salamanders, and newts, batrachians which retain
the tail throughout life, having generally two pairs of limbs
of approximately equal size, and sometimes possessing
gills or gill-slits in the adult condition; the Anura, or
frogs and toads, with no tail in the adult condition, with
short and broad trunk, with hind limbs greatly exceeding
the fore limbs in size, and never with gills or gill-slits
in the adult stage; and the Gymnphiona, or ccecilians,
snake-like batrachians having neither limbs nor tail, with
a dermal exoskeleton and without gills or gill-slits in the
adult.

Mud-puppies, salamanders, etc. (Urodela).— Trcuni-
CAL NOTE.—If possible obtain specimens of mud-eels (.S77e7), com-
mon in the South, or mud-puppies (Vecfurus), common in the cen-
tral North, as examples of batrachians with gills persisting in the
adult stage. One or more species of Amdlystoma may be found in
almost any part of the country, and larve of large size may be found
with the external gills. Foran example of the general long-tailed
or Urodelous type of batrachian any salamander or newt occurring
in the vicinity of the school may be used. The little green triton or
eft (Diemyctylus viridiscens) of the eastern States, or its larger
brown-backed congener of the Pacific coast (LD. forosus) is common
in water, while another eft, the little red-backed salamander,
(Plethodon) is common in the woods under logs and stones. The
external characters of the body should be compared with those of
the toad. The skeleton should be prepared by macerating away
the flesh (for directions, see p. 452), and the presence of the many
caudal vertebree and the ribs, the equality in size of the legs, and
other points should be noted. Compare with skeleton of toad.
Make drawings. It will be well, also, to dissect out and examine
the various internal organs of the salamander, comparing them with
the same organs in the toad. The salamander, indeed, is in many
ways better than the toad as an example of the class. Its body is
less adaptively modified and shows the essentially fish-like charac-
ter of the batrachian structure,

298 ELEMENTARY ZOOLOGY

The batrachians which retain external gills in the adult
stage are the members of two families of which the
American representatives are known as mud-eels (Szren)
and mud-puppies or water-dogs (WVecturus). The mud-
eels, which are found ‘‘in the ditches in the swamps of
the southern States from South Carolina to the Rio Grande
of Texas and up the Mississippi as high as Alton, Il]linois,’’
are blackish in color, have no hind legs and are long and
slender, with the tail shorter than the rest of the body.
They reach a length of nearly three fech> “the mud-
puppies, found in the Great Lakes and in the rivers of the
upper Mississippi valley, are brown with colored spots,
and are about two feet long when full grown. They have
both fore and hind legs.

A few salamanders, while not possessing external gills
when adult, have a spiracle or small circular opening in
the side of the neck which leads into the tireae = 4 We
best-known American salamander of this kind is the
large heavy-bodied blackish water-dog or ‘‘ hellbender ”’
(Cryptobranchus) of the Ohio River. It is about two feet
long, and is ‘‘a very unprepossessing but harmiess
’ It has a conspicuous longitudinal fold of skin
along each side of the body. The largest known ba-
trachian, the giant salamander of Japan (/egalobatrachus\,
reaching a length of three feet, is related to the water-
dog.

Of all the salamanders the most interesting are the
blunt-nosed salamanders (Ambdblystoma). A dozen or

creature.’

more species of Amdlystoma occur in North America, of
which ¢2grz2num, a dark-brown species with many irregular
yellow blotches sometimes arranged in cross-bands, is the
most widespread. The larve of some Ambdlystoma retain
their gills until they have reached a large size, and in one
or two species the usual metamorphosis is very long
delayed and the salamanders produce young while in the

BRANCH CHORDATA: CLASS BATRACHIA 299

larval condition, that is, while retaining the gills and a
compressed fin-like tail. In the case of a certain Mexican
species (A. maculatum) it is believed that the final meta-
morphosis never occurs. The Mexicans call these gilled
larval Amdlystoma axolotls, and use them for food. For

Fic, 121.—The Western brown eft, or salamander, Diemyctylus torosus.
(From living specimen. )

a long time naturalists supposed the Amélystoma larve
which produce young to be the adults of a species of sala-
manders which retained their gills through life, like the
sirens and mud-puppies, and classified them in a distinct
genus.

Of the various common salamanders or newts some are
found in streams, ponds, and ditches, and some under
logs and stones in the woods. ‘The aquatic forms have
the tail compressed (flattened from side to side), while
the land forms have the tail cylindrical, tapering to a
point. Most of the land-salamanders produce their young
alive, while the water forms lay eggs which are usually
attached to a submerged plant-stem. The salamanders
are, almost without exception, found only in the northern
hemisphere. |

Frogs and toads (Anura).—There are about a dozen
Spcetes of frogs in the United States. The largest of
these, and indeed the largest of all the frogs, is the well-
known bullfrog (Rana catesbtana), which reaches a length
(head to posterior end of body) of eight inches. It is
found in ponds and sluggish streams all over eastern

3200 ETEMENTARY ZOOLOGY

United States and in the Mississippi valley. It is green-
ish in color with the head usually bright pale green. Its
croaking is very deep and sonorous. The pickerel-frog
(R. palustris), which is bright brown on the back with two
rows of large oblong square blotches of dark brown on
the back, is found in the mountains of eastern United
States. The little pale reddish-brown wood-frog (R. sy/-
vatica) with arms and legs barred above is common in
damp woods and is ‘**an almest silent (toa 2!) ic
peculiar and infrequently seen frogs known as the ‘‘ spade-
foots ’’ (Scaphiopus) are subterranean in habit and usually
live in dry fields or even on arid plains and deserts.
They pass through their development and metamorphosis
very rapidly, appearing immediately after a rain and lay-
ing their eggs in temporary pools. Att this time of egg-
laying they utter extraordinarily loud and strange cries.
"ome frogs in other parts of the world live in trees, and
the eggs of one species are deposited on the Jeaves of
trees, leaves which overhang the water being selected so
that the issuing young may drop into it.

- The true tree-frogs or tree-toads (Hylidz) constitute a
family especially well represented in tropical America.
They have little disk- or pad-like swellings on the tips of
their toes to enable them to hold firmly to the branches
of the trees in which they live. Some, like the swam
tree-frog and the cricket-frog, are not arboreal in habit,
remaining almost always on the ground. The common
tree-frog of the eastern States (//y/la versicolor) is green,
gray, or brown above with irregular dark blotches, and
yellow below. It croaks or trills, especially at evening
and in, damp weather. . Pickering s tieethesaq 77
pickeringit) makes the “first note of spring) smegene
eastern States. This tree-frog is the one most frequently
heard in the autumn too, but ‘‘its voice is less vivacious

than in the spring and its lonely pipe in dry woodlands is

BRANCH CHORDATA: CLASS BATRACHIA 301

always associated with goldenrods and asters and falling
The tree-frogs of North America lay their eggs

9)

leaves.
in the water on some fixed object as an aquatic plant, in
smaller packets than those of the true frogs, and not in
strings as do the toads.

The toads (Bufonide) differ from the true frogs in
having no teeth and in not having, as the frogs do, a
cartilaginous process uniting the shoulder-bones of the
two sides of the’ body. The absence of this uniting
process makes the thoracic region capable of great expan-
sion. There are only a few species of toads in North
America, but one of these species, the common American
toad (Bufo lentiginosus), is very abundant and wide-_
spread. It appears also in two or three varieties, the
common toad of the southern States differing in several
particulars from that of the northern. The toad is a
familiar inhabitant of gardens, and does much good by
feeding on noxious insects. It is most active at twilight.
Its eggs are laid in a single line in the centre of a long
slender gelatinous string or rope, which is nearly always
tangled and wound round some water-plant or stick near
bie stere.on the bottom of-a pond. “The ‘eggs are jet
black and when freshly laid are nearly spherical. At the
time of egg-laying the toads croak or call, making a sort
of whistling sound and at the same time pronouncing deep
in the throat ‘‘bu-rr-r-r-r.’’ The toad does not open its
mouth when croaking, but expands a large sac or resonator
in its throat. The toad-tadpoles are blacker than those
of frogs or salamanders, and undergo their metamorphosis
while of smaller size than those of frogs. When they
leave the water they travel for long distances, hopping
along so vigorously that in a few days they may be as far
as a mile from the pond where they were hatched. They
conceal themselves by day, but will appear after a warm
shower; this sudden appearance of many small toads

ao2 ELEMENTARY ZOOLOGY

sometimes gives rise to the false notion that they have
fallen with the rain. |

Ceecilians (Gymnophiona).—The third order of ba-
trachians, the ceecilians, includes about twenty species of
slender worm- or snake-like limbless forms which are
confined to the tropics. Some of them are wholly blind
and the others have only rudimentary eyes. In them the
skin is folded at regular intervals so that the body appears
to be rigid or segmented, and in some species there are
small concealed horny scales in the skin.

CHAP EER: XXXVI

DRANG CHORDATA (Continued. CLASS REP-
Sweet CHE. SNAKES, LIZARDS; TURTLES,
See CcoumLtks, ETC.

THE GARTER SNAKE (7kzamnophis sp.)

TECHNICAL NOTE.—Garter snakes may be found almost any-
where during the spring and summer months. If possible each
student should have a specimen, but in case it is difficult to get
enough snakes two students can use a single specimen. If garter
snakes are rare, take any other snake. Snakes will live a long time
without feeding and specimens should be kept alive until ready to
use. Kill with chloroform as directed for the toad (p. 5). After
completing the study of the external characters place each specimen
in a dissecting-pan and with a pair of scissors cut through the scales
on the ventral side, passing backwards from the eighteenth to the
fortieth. Pin back the edges of the cut and thus expose the heart.
Through its lower end, the ventricle, insert a large canula; inject
with a fairly large syringe the glue mass which is described on
p. 452. This injection will fill the entire arterial system. To inject
the venous system make another cut through the ventral scales, cut-
ting forward from the anal scale through about forty of them. Note
the injected mass in some of the vessels already filled. Take one
of the large vessels still containing blood and pass two ligatures
beneath it. Get ready a small canula and cut a slit in the vessel,
elevating the head so that the blood will run out as much as possi-
ble. Now wash the blood off, insert the canula in the slit and tie
one ligature about the vessel containing the canula ; have the other
ready to tie after the vein has been injected. Use a new color for
the venous system. Leave specimen in cold water fora time until
the injection is hard. Then continue the cut from the anal plate
forward to the lower jaw and pin out the edges of the cut on both
sides in the dissecting-pan.

Structure (fig. 122).—Note that the snake is covered

with horny scales somewhat as the fish is. How do these

scales differ from those of the fish ? In snakes the scales
3203

304 ELEMENTARY -ZOOLGGy,

are not bony, but are true skin structures. Note the modi-
fication of the scales on the head, back: and yvewtmal sur
face. Those on the dorsal surface often have minute
ridges, the £ee/s. How do the ventral scales differ from the
dorsal ones and others? By a system of muscles these
ventral scales are rhythmically moved and as their posterior
edges are pushed back against some resisting object the
body glides forward. On the head note the pair of eves.
Are there eyelids? In front of each eye note an opening.
What are these openings? Thrust a bristle into the —
opening and see where it enters the mouth-cavity through
the zxzfernal nares. Does the-snake havevemtermaliears ©
Observe the very long jaws and note that they are loosely
hinged. Examine the inside of thie moag7= = wc pncre
teeth? If so where are they situated, and how arranged?
Note that all of the teeth point backwards. Food is not
chewed. When some object of prey, a frog, or mouse,
for example, is seized, the teeth hold 1tdast to tae roo: of
the mouth and by a backward and forward movement of
the lower jaws it is gradually drawn into the large
cesophagus. What is the character and situation of the
tongue? Just behind the tongue note the narrow slit,
glottis, opening into the wzenudpipe, or trachea. Back of
the trachea opens the wsophagus. | |
When the snake is laid open the elongate sear¢ will
be conspicuous in the anterior third of the body. Insert
a blowpipe or quill into the glottis just back of the tongue,
and inflate the /wzg, which is a long, thin-walled bag
extending from the region of the heart posteriorly for
two-thirds of the length of the body. There is but one
developed lung, the right; note at the anterior end of the
lung a small mass of tissue, the atrophied left lung.
Running forward from the lung is a long tube composed
of incomplete cartilaginous rings, connected by mem-
brane, the ¢vachea. Note the long straight ahmentary

BRANCH: CHORDATA: CLASS REPTILIA 305

canal. Distinguish the wsophagus, stomach, intestine,
vectum and the anus.

In the region of the lung is an elongated dark-red
glandular mass, the “ver. The secretion from the liver
passes down through the long hepatic duct to the oval-
shaped green gall-bladder and into the intestine.

TECHNICAL NOTE.—The bile-duct may be injected through the
gall-bladder with some colored injecting mass.

Note that the duct running off from the gall-bladder to
the intestine passes through a pink glandular organ, the
pancreas. At the anterior end of the pancreas is a dark-
red nodular structure, the sp/eex. The alimentary canal,
the liver and the spleen are all suspended from the dorsal
wall of the body-cavity by a delicate sheet of tissue.
What is this? This condition we have alsu noted in the
toad and fish.

Toward the posterior end of the body cavity are two
long, dark-red glands, the Azdueys, which are the prin-
G@ipal excretory organs of the body. Through a long,
slender tube (the wref¢er) each of the kidneys passes off its
wastes, Where do the ureters open ?

Anterior to the kidneys are the reproductive organs.
Hite esos. produced by the female snake, after being
fertilized, pass backward through the egg-tubes. During
the breeding season these tubes are much distended.
Eeiieetsaue to the presence of the developing eggs, for
the young snakes are hatched in the egg-tubes.

A successful injection as directed in the first technical
note will have filled both arterial and venous systems.
How does the general shape of the snake’s Zear¢ compare
with that of the toad? The heart consists of two ven-
tricles, incompletely separated, and ¢wo auricles. In the
snake the conus arteriosus is very much shortened and is
not visible. Note two large vessels arising from the

306 ELEMENTARY ZOOLOGY

median portion of the ventricle. The one on the left side
is the left aortic artery or left aortic arch, while the right
gives off two branches. Where does the anterior one of
these run?) The main branch, or rzght aortic arch, passes
back to meet its fellow, the left aortic artery, forming with
it the dorsal aorta, which runs posteriorly to the end of the
tail. Note the various branches given off by the dorsal
aorta and trace some of them. Arising from the ventricles
beneath the two aortic arches is the pulmonary artery,
which goes to the lung. There the blood is purified, after
which it is taken up by the pulmonary vein and carried
back to the left auricle, whence it passes into the ventricle
to be mixed with the impure blood from the right auricle.
From the arteries the blood flows to all parts of the body -
through fine capzllaries, bathing the tissues, giving off
oxygen and taking up the carbonic acid gas. From these
capillaries it passes into veins and so back to the heart;
from the anterior end of the body through the jugular
veins and from the posterior portion of the body through
the postcaval vein. Flowing forward from the tail in the
caudal vein, the blood enters the capillaries of the kidneys,
where the waste matter is taken from it. This part of the
circulatory system is known as thereza/-portalcirculation.
From the kidneys the blood flows through the postcaval
vein anteriorly to the heart.

The blood which passes out from the dorsal aorta to all
parts of the alimentary canal is again collected into veins
which unite to form the mesenteric ver. ‘This vein runs
to the liver, where it breaks up into capillaries. Thence
the blood is carried into the postcaval vein, which leads
directly to the heart. This part of the circulatory system
which collects blood from the alimentary canal and carries
it to the liver is called the hepfatic-portal system.

Just in front of the heart will be noted a nodular struc-
ture, the ¢hyrotd gland, while a little in advance of the

BRANCH CHORDATA: CLASS REPTILIA 307

thyroid may be seen a long glandular mass, the ¢hymus
gland. The functions of these glands are not certainly
understood. |

Remove the alimentary canal and muscles from a part
of the body and note that the azzal skeleton, like that of
the other vertebrates studied, consists of a series of verfe-
bre placed end to end. Are there arms or legs? Are
shoulder and pelvic girdles present? How many of the
vertebrz bear 7z6s 2? The ribs connect at their lower ends
with the ventral scales. Note the great number of the
vertebre and ribs as compared with those of the toad or
fish. What are those vertebrz called which bear no ap-
pendages or ribs ? Examine carefully the elongated sku//
of the snake, especially the modified jaws. A detailed
study of the skeleton may be made by referring to
pic account of the skeleton.of the lizard in Parker's
‘‘ Zootomy,’’ pp. 130 ef seq.

The nervous system may be worked out in a specimen
which has been imniersed in 20 per cent nitric acid. The
description of the nervous system of the toad (see pp. 12—
13) will suffice for a guide to the study of the nervous
system of the snake. The special sense organs, as eyes
and ears, should be examined and compared with those
of the fish and toad.

Life-history and habits.— The garter snakes are more
or less aquatic in habit and are good swimmers. They
are often found far from water, but in greatest abundance
where the cat-tails and rushes grow thickest. They feed
on frogs, salamanders, and field-mice, which they swallow
mweie. All the carter snakes ‘are ovoviviparous, i.e.,

hatch eggs within the body-cavity. The eggs, often as
- many as eighteen or twenty, are enclosed within widened
portions of the oviducts during embryonic existence; when
the young are born they are able to shift for themselves,
During cold weather the garter snake hibernates, hiding

308 - ELEMENTARY ZOOLOGY

then in some gopher-hole, or, in the warmer climates,
under some log or stone, there to lie dormant until the
warm days of spring come, when it resumes activity.

The garter snake sheds its skin at least once a year,
sometimes oftener. This process may be observed in
snakes kept in confinement. For some time before molt-
ing the animal remains torpid, the eyes become milky,
and the skin loses its lustre. After a few days it conceals
itself, the skin about the lips and snout pulls away and the
animal slips out of its entire skin. The snake not only
sheds the skin of the body but also the covering of the
eyes. onakes have no eyelids, as we have already noted,
that which represents the eyelid being a transparent
membrane which covers the eyeball. |

No species of the garter snake group is poisonous.
Sometimes a garter snake may appear to be vicious, but
its teeth are very short and at best it can only make a
small scratch scarcely piercing the skin.

OFEE Ry ACE Pa ieee

The class Reptilia includes the lizards, snakes, tortoises,
turtles, crocodiles, and alligators. Although popularly
associated in the common mind with the batrachians, the
reptiles. are really more nearly related to the mds than
to the salamanders and frogs. In general shape they
more nearly resemble the batrachians, but in the structural
condition of the internal body organs they are more like
the birds: They are cold-blooded, and breathe sexelu—
sively by means of lungs, the forms which live in water
coming to the surface to breathe. They are covered with
horny scales or plates, which with the entire absence of
gills after hatching readily distinguish them from all the
batrachians. While most reptiles hve on land, some in-
habit fresh water and some the ocean. As the young

BRANCH CHORDATA: CLASS REPTILIA 309

have the same habitat and general habits as the adult,
there is no such metamorphosis in their life-history as ts
shown by the batrachians. The reptiles are widespread
geographically, occurring, however, in greatest abund-
ance in tropical regions, and being wholly absent from the
Arctic zone. They are not capable of such migrations
as are accomplished by the birds and many mammals,
but withstand severely hot or cold seasons by passing into
a state of suspended animation or seasonal sleep or torpor.

Fic. 123.—A lizard in the grass. (Photograph from life by Cherry Kear-
ton; permission of Cassell & Co.)

Body form and organization.—The chief variations in
body form among the reptiles are manifest when a turtle,
lizard, and snake are compared. In the turtles, the body
is short, flattened, and heavy, and provided always with
four limbs, each terminating in a five-toed foot; in the
lizards the body is more elongate and with usually four
legs, but sometimes with two only, or even none at all;
while in the snakes the long, slender, cylindrical body is
legless or at most has mere rudiments of the hinder limbs.
With the reptiles locomotion is as often effected by the
bending or serpentine movements of the trunk as by the
use of legs. Among lizards and snakes the body 1s
covered with horny epidermal scales or plates, while

a0 ELEMENTARY ZOOLOGY

among the turtles and crocodiles there may be, in addition
to the epidermal plates, a real deposit of bone in the skin
whereby the effectiveness of the armor is increased. The
epidermal covering of snakes and lizards is periodically
molted, or, as we say, the skin is shed. The bright colors
and patterns of snakes and of many lizards are due to the
presence and arrangement of pigment-cells in the skin.
Among some reptiles, notably the chameleons, the colors
and markings can be quickly and radically changed by
an automatic change in the tension of the skin.
Structure.—In reptiles, <as in battachiansseeme. chict
variations in the body skeleton are correlated with differ-
ences in external body form. In the short compact body
of the turtles and tortoises the number of vertebre is much
smaller than in the snakes. Some turtles have only 34
vertebrz; certain snakes as many as 400. _ The reptilian
skull, in the number and disposition of its parts and in the
manner of its attachment to the spinal column, resembles
that of the birds, although the cranial bones remain sep-
arate, not fusing as in the birds. -In the snake the two
halves of the lower jaw °are not fused in front but are
united by elastic hgaments, which condition, together
with the extremely mobile articulation of the base of the
jaws, allows the snakes to open their mouths so as to take
in bodies of. great size. All of the reptiles eee pee
turtles, are provided with small teeth which serve, gen-
erally, for seizing or holding prey and not for mastication.
The poisonous snakes have one or more long, sharp, and
erooved or hollow fangs (fig. 131). In the legless reptiles
both shoulder and pelvic girdles may be wholly lacking;
in the limbed forms both girdles are more or less well
developed.
The tongue of many reptiles, notably the snakes, is
bifid or forked, and is an extremely mobile and sensitive
organ. The cesophagus is long and in the snakes can be

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BRANCH CHORDATA: CLASS REPTILIA gil

stretched very wide so as to permit the swallowing of
large animals whole. Reptiles breathe solely by lungs,
of which there is a pair They are simple and sac-like,
the left lung being often much smaller than the other.
In turtles and crocodiles the lungs are divided internally
by septa into a number of chambers. Because of the
rigidity of the carapace or ‘‘ box ’’ of turtles the air cannot
be taken in the ordinary way by the use of the ribs and
rib-muscles, but has to be swallowed. The reptilian heart
consists of two distinct auricles and of two ventricles,
which in most reptiles are only incompletely divided, the
division into right and left ventricles being complete only
among the crocodiles and alligators, the most highly
organized of living reptiles.

The organs of the nervous system reach a considerable
degree of development in the animals of this class. The
brain in size and complexity is plainly superior to the
batrachian brain and resembles quite closely that of birds.
Of the organs of special sense those of touch are limited
to special papillz in the skin of certain snakes and many
lizards. ‘Taste seems to be little developed, but olfactory
organs of considerable complexity are present in most
forms, and consist of a pair of nostrils with olfactory
papillz on their inner surfaces. The ears vary much in
degree of organization, crocodiles and alligators being the
only reptiles with a well-defined outer ear. This consists
of a dermal flap covering atympanum. Eyes are always
present and are highly developed. ‘They resemble the
eyes of birds in many particulars. All reptiles, excepting
the snakes and a few lizards, have movable eyelids, in-
cluding a nictitating membrane like that of the birds.
_ With the snakes the eye is protected by the outer skin,
which remains intact over it, but is transparent and
thickened to form a lens just over the inner eye. ‘Turtles
and lizards have a ring of bony plates surrounding the

312s ELEMENTARY ZOOLOGY

eyes similar to that of the birds. In addition to the usual
eyes there is in many lizards a remarkable eye-like organ,
the so-called pineal eye. which is situated in the roof of
the cranium, and is believed to be the vestige of a true
third eve, which in ancient eS was probably a well-
developed organ.

Life-history and habits.—Most reptiles lay eggs from
which the young hatch after a longer or shorter period of
incubation. Usually the eggs are simply dropped on the
ground in suitable places (although certain turtles dig
holes in which to deposit them), where they are incubated
by the general warmth of the air and ground. However,
some of the giant snakes, the pythons for instance, hold
the eggs in the folds of the body. o) lt thevexse ot comic
snakes -and lizards the eggs are retained in the body of
the mother until the young hatch; such reptiles are said’
to be ovoviviparous, because the young, although born
alive, are in reality enclosed injan ese uni@P tie mement
of birth... Among reptiles. the newly Nateheas youne
resemble the parents in most respects.emeepemm size. vet
striking differences in coloration and pattern are not rare.
But there is in this class no metamorphosis such as
characterizes the post-embryonic development~ of the
batrachians.

The food of reptiles consists almost exclusively of
animal substance, although some species, notably the
green turtles and certain land-tortoises, are vegetable-
feeders. The animal-feeders are mostly predaceous, the
smaller species catching worms and insects, while the
larger forms capture fishes, frogs, birds, and their eggs,
small mammals, and other reptiles.

Classification.—The living Reptilia are divided into
four orders, of which one includes only a single genus,
Hatterta, a peculiar lizard found in New Zealand. The
other three are the Squamata, which includes the lizards

BRANCH CHORDATA: CLASS REPTILIA 313

and snakes,* distinguished by the scaly covering of the
body, the Chelonia, which includes the tortoises and
turtles, distinguished by the shell of bony plates which
encloses the body, and the Crocodilia, which includes the
crocodiles and alligators, whose bodies are covered with
rows of sculptured bony scutes.

Tortoises and turtles (Chelonia).—Tercunica, Notr.—
Obtain specimens of some pond- or land-turtle common in the
vicinity of the school. The red-bellied and yellow-bellied terrapins
(Pseudemys) or the painted or mud-turtles (Chrysemys) are com-
mon over most of the United States. (Pseudemys is found south of
the Ohio River and Chrysemys north of it.) They may be raked
up from creek-bottoms or fished for with strong hook and line,
using meat as bait. They will live through the winter if kept in a
cool place, without food or special care of any kind. Observe their
swimming and diving, the retraction of head and limbs into the
shell, the use of the third eyelid (nictitating memorane), and the
swallowing of air.

Examine the external structure of a dead specimen (kill by
thrusting a bit of cotton soaked with chloroform or ether into the
windpipe ; see opening just at base of tongue). Note shell consist-
ing of a dorsal plate, the carapace, and ventral plate, the plastron,
and the lateral uniting parts, the bridge. Note legs, and head with
horny beak but no teeth. Compare with snake. The examination
of the internal structure of the turtle can be readily made by saw-
ing through the bridge on either side and removing the plastron.
Note the ligaments which attach the plastron to the shoulder and
pelvic girdles. Note muscles covering these bones. Note just
behind the shoulder girdle the heart (perhaps still pulsating) and
the dark liver on each side of it. Work out the alimentary canal,
the trachea and lungs, and other principal organs, comparing them
with those of the snake. The skeleton can be studied by dissecting
and boiling and brushing away the flesh which still adheres to the
bones. The comparison of the skeleton of the turtle with that of
the snake is very instructive ; marked differences in the skeletons of
the two kinds of reptiles are obviously correlated with the differ-
ences in habits and shape of body. Note in the skeleton of the
turtle especially the shoulder and pelvic girdles and limbs (absent in
the snake) and smal] number of vertebre and ribs.

Among the common turtles and tortoises of the United
States are several species of soft-shelled turtles (Trio-

* By many zoologists the lizards and snakes are held to form two distinct
orders, Lacertilia and Ophidia.

314 ELEMENTARY ZOOLOGY

nychidz) with carapace not completely ossified and both
carapace and plastron covered by a thick leathery skin
which is flexible at the margins; the snapping-turtle
(Chelydra serpentina), cominon in streams and ponds, with
shell high in front and low behind and head and tail long
and not capable of being withdrawn into the shell; the
red-bellied and yellow-bellied terrapins (Pseudemys), red
and yellow, with greenish-brown and black markings,
common on the ground in woods and among rocks and
also near water and sometimes in it; the pond- or muc-
turtle (CArysemys), also brightly colored and usually con-
fined to ponds and pond-shores; and the box-tortoise
(Czstudo carolina), common in woods and upland pastures ©
and readily recognizable by its ability to enclose itself
completely in its shell by the closing down of the lids
of the plastron. All of these fresh-water and land-turtles
except the soft-shelled turtles belong to one family, the
Emydidz, but have somewhat diverse habits. Most of
them are carnivorous, but few catch any very active
prey. While some are strictly aquatic, others are as
strictly terrestrial, never entering the water. The eggs
of all are oblong and are deposited in hollows, sometimes
covered in sand. The newly hatched young are usually
circular in shape, and vary in color and pattern from the
parents.

The ‘‘diamond-back terrapin’’ (Walaclemmys palus-
trzs), used for food, is a salt-water form ‘‘inhabiting the
marshes along the Atlantic coast from Massachusetts to
Texas. About Charleston [and Baltimore] they are
very abundant and are captured in large numbers for
market, especially at the breeding season wien dhe
females are full of eggs: ~ Further north. they ame duc
from the salt mud early in their hibernation<=and are
sreatly esteemed, being fat and savory.’’

Strongly contrasting with the usually small land- and

BRANCH CHORDATA: CLASS REPTILIA 325

fresh-water turtles are the great sea-turtles, such as the
leather-back, the loggerhead and the green turtles. Some
of these animals reach a length of six feet and more and
a weight of nine hundred pounds, and have the feet com-
pressed and fin-shaped for swimming. They live in the
open ocean, coming on land only to lay their eggs, which
are buried in the sand of ocean islands. These egg-laying,
visits are almost always made at night, and the turtles

Fic. 124.—The giant land-tortoise of the Galapagos Islands, 7estudo sp.
These tortoises reach a length of four feet. (Photograph from life by
Geo, Coleman.) 3

are then often caught by ‘‘turtlers.’’ The flesh of most
of the sea-turtles is used for food, and from the shell of
certain species, notably the ‘‘hawk-bill’’ (Eretmochelys
embricata) the beautiful ‘‘ tortoise-shell ’’ used for making
combs and other articles is obtained. The common green
turtle (Chelonia mydas) of the Atlantic coast is the species
most prized for food. It is a vegetarian, feeding on the
roots of Zostera, the plant known in New England as
eel-grass, though farther south it is called turtle-grass.

316 ELEMENTARY ZOOLOGY

When grazing the turtles eat only the roots, the tops thus
rising to the surface, where they indicate to the turtler the
animal’s whereabouts. The turtler, armed with a strong
steel barb attached to a rope and loosely fitted to the end
of a pole, carefully rows up to the unsuspecting animal,
and with a strong thrust plunges the barb through its
shell, withdraws the pole, and, grasping the rope, now
lirmly attached to the turtle’s back, lifts the animal to the
surface. Here, with assistance, he tumns 1 tipo tac podt.
where it is rendered helpless by being thrown on its back
and by having its flippers tied. ~~ liese gurhies ane. 41s0
caught on their breeding-gounds, being found on the sand
at night: by the turtler, turned over, om theme backs, and
left thus securely caught until assistance comes to help
get them into the boats.

Snakes and lizards (Squamata).—TrcunicaL NoTE.—A
snake has already been dissected and studied. It will be instructive
to compare the external structures, at least, of a lizard with that o.
the snake. Specimens of some species of the common swift (Scedo-
porus) are obtainable almost anywhere in the United States. The
‘‘pine-lizards ” of the east belong to this genus. Lizards may be
sought for in woods, along fences, and especially on warm rocks.

2

Fic. 125.—The blue-tailed skink, Lameces skeltonianus. (From living
specimen. )

The group of lizards is a very large one, about 1,500
species being known, but it is represented in the United
States by comparatively few species. Lizards are espe-
cially abundant in the tropics of South America. atic
strange and fantastic appearance presented by some of
them has made certain species the object of much interest

BRANCH CHORDATA: CLASS REPTILIA ane

and often fear on the part of the natives of tropical lands.
In those regions are current extraordinary stories and
beliefs regarding the habits and attributes of certain lizards
like the basilisk and chameleon. Lizards are all more or
less elongate and some are truly snake-like in form. The
legs, though usually present and functional, are in many
cases much reduced, and in some forms, as the glass-
snake, either one or both pairs are so rudimentary as to
have no external projection whatever. Although lizards

Fic. 126.—The Gila monster, Ae/oderma horridum, the only poisonous
lizard. (Photograph from life by J. O. Snyder.

are often regarded as being poisonous, only one genus,
FH[eloderma, the Gila Monster, is really so. All others
are perfectly harmless as far as poison is concerned, and
most of them are unusually timid. They vary in size from
a few inches to six feet in length. Most of them are ter-
restrial, some arboreal, and some aquatic.

_ Among the lizards of this country the swifts and ground-
lizards are familiar everywhere. In certain regions the
elass-snake or joint-snake (Opheosaurus ventralis) 1s
common. This animal, popularly considered to be a
snake, has no external limbs,.and its tail is so brittle, the
vertebra composing it being very fragile, that part of it
may break off at the slightest blow. In time a new tail
is regenerated. It Jives in the central and northern part
of the United States, and burrows in dry places. In the
western part of the country horned toads (Phrynosoma)
are common, about ten different species being known.
These are lizards with shortened and depressed body and
well-developed legs. The body is covered with protec-

318 ELEMENTARY ZOOLOGY

tive spiny protuberances, and in individual color and
pattern resembles closely the soil, rocks, and cactus among
which the particular horned toad lives. All the species
of Phrynosoma are viviparous, seven or eight young being
born alive at a time.

In New Mexico, Arizona, and northern Mexico the only
existing poisonous lizards, the Gila Monster (/feloderma)
(fig. 126) is found. This is a heavy, deep-black, orange-
mottled lizard about sixteen inches long. There is much
variance of belief among people regarding the Gila Mon-
ster, but recent experiments have proved the poisonous
nature of the animal. The poison which is secreted by
elands in the lower jaw flows along the grooved teeth into
the wound. A beautiful and interesting little lizard found
in the South is the green chameleon (dxolts principalts).
Its body is about three inches long with a slender tail of
five or six inches. The normal color of the chameleon is
grass-green, but it may ‘‘ assume almost instantly shades
varying from a beautiful emerald to a dark and iridescent
brenmze color, -

In the tropics many of the lizards reach great size and
are of strange shape and patterns. The flying dragons
(Draco) have a sort of parachute on each side of the body
composed of a fold of skin supported by five or six false
posterior ribs. -Ihese lizards live in the trees of the Bast
Indiesand “fly ’“or sail from tree fo tree 3 slain. anc
very beautifully colored. The iguanas (/gwana) of the
tropics of South America are commonly used for food.
They live. mostly in trees, and reach a length of twe or
six feet. The monitor (Varanus niloticus) is a great
water-lizard that lives in the Nile, and feeds on crocodiles’
eggs, of which it destroys great numbers. It is the prin-
cipal enemy of the crocodile. When full grown it reaches
a length of six feet.or even more:

About 1,000 living species of snakes areyaonn-

rs |
BRANCH CHORDATA: CLASS REPTILIA 319

Usually they have the body regularly cylindrical, and
without distinct division into body regions. Legs are
wanting, locomotion being effected by the help of the
scales and the ribs. No snake can move forward on a
perfectly smooth surface and no snake can leap. In some
forms, such as the pythons, external rudiments of the hind
limbs are present, but do not aid in locomotion. The
mouth is large and distensible so that prey of considerably
greater size than the normal diameter of the snake’s body
is frequently swallowed whole. ‘The sense of taste is very
little if at all developed, as the food is swallowed without
mastication. The tongue, which ts protrusible and usually
red or blue-black, serves as a special organ of touch.
Hearing is poor, the ears being very little developed.
The sense of sight is also probably not at all keen.
Snakes rely chiefly on the sense of smell for finding their
prey and their mates. The colors of snakes are often
brilliant, and in many cases serve to produce an effective
protective resemblance by harmonizing with the usual
surroundings of the animal. The food of snakes consists
almost exclusively of other animals, which are caught
alive. Some of the poisonous snakes kill their prey before
swallowing it, as do some of the constrictors. While most
snakes live on the ground, some are semi-arboreal and
others spend part or all of their time in water. Cold-
region snakes spend the winter ina state of suspended
animation; in the tropics, on the contrary, the hottest part
of the year is spent by some species in a similar ‘‘ sleep.’’

There are so many common snakes in the United States
that only a few of the more familiar forms can be men-
tioned. The non-poisonous species of America belong
to the family Colubridz, while all but one of the poisonous
species belong to the family Crotalidze, characterized by
the presence of a pair of erectile poison-fangs on the upper
jaw. Among the commonest of the Colubride are the

220 ELEMENTARY ZOOL@G

garter snakes (7hamnophts) (fig. 127), always striped and
not more than three feet long. The most widespread
species is Zhamunophis sirtalts, rather dully coiored with
three series of small dark spots along each side. The

Fic. 127.—A garter snake, Zhamnophis parietalis. (Photograph from life
by J. ©: Snyder.)
common water-snake (Vatrzx sipedon) is brownish with
back and sides each with a series of about 80 large square
dark blotches alternating with each other. It feeds on
fishes and frogs, and although ‘‘ unpleasant and ill-tem-
pered’’ is harmless. One of the prettiest and most gentle
of snakes is the familiar little greensnake (Cyclophis
@stivus), common in the East and South in moist
meadows and in bushes near the water. It feeds on in-
sects and. can be easily kept alive im ‘comtutemment 7 x
familiar larger snake is the blacksnake or blue racer (Las-
caniom constrictor), ‘‘\ustrous pitch black, general color
greenish below and with white throat.’’ It is ‘‘ often
found in the neighborhood of water, and is particularly
partial to thickets of alders, where it can hunt for toads,
mice, and birds, and being an excellent climber it is often
seen among the branches of small trees and _ bushes,
hunting for young birds in the nest.’’ The chain-snake
(Lampropeltts getulus) of the southeast and the king-
snake (also a Lampropeltis) (fig. 128) of the central

BRANCH CHORDATA? -CLASS REPTILIA 221

States are beautiful lustrous black-and-yellow spotted
snakes which feed not only on lizards, salamanders,
small birds and mice but also on other snakes. The
king-snake should be protected in regions infested by
‘“‘rattlers.’. The spreading adder or blowing viper
(Heterodon platirhinos), a common snake in the eastern
States, brownish or reddish with dark dorsal and lateral
blotches, depresses and expands the head when angry,
hissing and threatening. Despite the popular belief in its
poisonous nature this ugly reptile is quite harmless. It
specially infests dry sandy places.

With the exception of the coral or beadsnake (Laps
fulvius), arather small jet-black snake with seventeen
broad yellow-bordered crimson rings, found in _ the
southern States, the only poisonous snakes of the United
States are the rattlesnakes and their immediate relatives,
the copperhead and water-moccasin. These snakes all
have a large triangular head, and the posterior tip of the
body is, in the rattlesnakes, provided with a ‘‘rattle’’

Fic. 128.—A king-snake, Lampropeltis boyfii. (Photograph from life by
J. O. Snyder.)

composed of a series of partly overlapping thin horny

capsules or cones of shape as shown in figure 130. These

horny pieces are simply the somewhat modified succes-

sively formed epidermal coverings of the tip of the body,

322 ELEMENTARY ZOOLOGY

which instead of being entirely molted as the rest of the
skinis, are, because of their peculiar shape, loosely attached
to one another, and by the basal one to the body of the
snake. The number of rattles does not correspond to the
snake’s years for several reasons, partly because more
than one rattle can be added to the tail moa year and
especially because rattles are easily and often broken off.
As many as thirty rattles have been found on one snake.
There are two species of ground-rattlesnakes or massa-

_

FIG. 129.—The gopher-snake, P7twophis beliona. (Photograph from life
by J. O. Snyder.)

saugas (Szs¢rurus) in the United States and ten species of
the true rattlesnakes (Crotalus). Vhe centre of distribu-
tion of the rattlesnakes is the dry tablelands of the south-
west in New Mexico, Arizona, and lexas. but there are
few localities in the United States cutside the high moun-
tains in which, ‘‘rattlers ~ do not occur or dia mer eccun

before they were exterminated by man. The copperhead
(Agkistrodon contortix) is light chestnut in color, with
inverted Y-shaped darker blotches on the sides, and

BRANCH CHORDATA: CLASS KEPTILIA 323

seldom exceeds three feet in length. It occurs in the
eastern and middle United States from Pennsylvania and
Nebraska southward. It is a vicious and dangerous
snake, striking without warning. The water-moccasin
(Agkistrodon prscivorous) is dark chestnut-brown with
darker markings. The head is purplish black above.
It is found along the Atlantic and Gulf coasts from North
Carolina to Mexico, extending also some distance up the
Mississippi valley. It is distinctively a water-snake, being
found in damp swampy places or actually in water. It
reaches a length of over four feet and is a very venomous
snake, striking on the slightest provocation. The com-
mon harmless water-snake is often called water-moccasin
in the southern States, being popularly confounded with
this most dangerous of our serpents. The poison of all of
these snakes is a rather yellowish, transparent, sticky fluid
secreted by glands in the head, from which it flows through

Fic. 130.—The rattles of the rattlesnake; the lower figure shows a longi-
tudinal section of the rattle.

the hollow maxillary fangs. The character and position
of the fangs are shown in figure 131. kemedial measures
for the bite of poisonous snakes are, first, to stop, if possi-
ble, the flow of blood from the wound to the heart, by

224 ELEMENTARY ZOOLOGY

-compressing the veins between the wound and heart, then
to suck (if the lips are unbroken) the poison from the
wound, next to introduce by hypodermic injection per-
manganate of potash, bichloride of mercury or chromic
acid into the wound, and finally perhaps to take some
strong stimulant as brandy or whiskey.

Of the kinds of snakes not found in this country perhaps
the most interesting are the gigantic boa constrictors,
anacondas, and pythons. Pythons are found in India,
the islands of the Malay archipelago, and Australia, while
the boas and anacondas live in the tropics of America.
The largest pythons reach a length of thirty feet and some
of the boas are nearly as large. These snakes feed on

Fic. 131.—Dissection of head of rattlesnake; 7, poison-fangs; £, poison-sac.

small mammals such as fawns, kids, water-rats, etc., and
birds. The prey is swallowed whole, being first encircled
and crushed to death in folds of the body. After a meal
the python or boa lies in a sort of torpor for some time.
A famous snake is the deadly cobra-da-capello of India.
These snakes are so abundant and the bite is so nearly -
certainly fatal that thousands of persons are killed each
year in India by it. Other extremely poisonous snakes
are the vipers (Vipera cerastes), which live in the hot
deserts of northern Africa. Over each eye there is a scaly

BRANCH CHORDATA: CLASS REPTILIA SIS.

spine or horn, from which the name horned viper is
derived. The most poisonous snake of South Africa is
the large and ugly puff-adder, which puffs itself up when
irritated. An interesting group of snakes is that of the
Hydrophidz or sea-snakes, which swim on the surface of
the ocean by means of their flattened and oar-like tails.
These forms live in the tropical portions of the Indian and
Pacific oceans, ranging as far north as the Gulf of Cali-
fornia, and spend their whole life in the water, ‘‘ out of
which they appear to be blind and soon die.’’ They are
extremely venomous, but are all of small size, rarely two
feet long.

Crocodiles and alligators (Crocodilia).— The crocodiles
and alligators are reptiles familiar by name and appear-
ance, though seen in nature only by inhabitants or visitors
in tropical and semitropical lands. In the United States
there are two species of these great reptiles, the American
crocodile (Crocodilus americanus), living in the West
Indies and South America and occasionally found in
Florida, and the American alligator (A/igator missts-
sippiensts), common in the morasses and stagnant pools
of the southern States. The alligator differs from the
crocodiles in having a broader snout. It is rarely more
than twelve feet long. The best-known crocodile is the
Nile crocodile, which is not limited to the Nile, but is
found throughout Africa. In the Ganges of India is
found another member of this group of reptiles called the
gavial. It is among the largest of the order, reaching a
fcuern, of twenty feet. [he crocodiles, alligators, and
gavials comprise not more than a score of species
altogether, but because of their wide distribution, great
size, and carnivorous habits they are among the most
conspicuous of the larger living animals. They live mostly
in the water, going on land to sun themselves or to lay
their eggs. They move very quickly and swiftly in water

326 ELEMENTARY ZOOLOGY

but are awkward on land. Fish, aquatic mammals and
other animals which occasionally visit the water are their
prey. The gavial and Nile crocodile are both known to
attack and devour human beings, and these species
annually cause a considerable loss of life. But few such
fatalities, however, are accredited to the American alli-
gator. |

CHAPTER XXVit

BRANCH CHORDATA (Continued). CLASS AVES:
EEE aS

THE ENGLISH SPARROW (Lasser domesticus)

TECHNICAL NOTE.—The English sparrow may be found now in
cities and villages all over the United States. It has become a
veritable pest, and the killing of the few needed for the laboratory
may be looked on as desirable rather than deplorable, as is the
killing of birds in almost all other cases. The males have a black
throat, with the other head-markings strong and contrasting (black,
brown, and white), while the females have a uniform grayish and
brownish coloration on the head.

Specimens are best taken alive, as shooting usually injures them
for dissection. One can rely on the ingenuity of the boys of the
class to procure a sufficient number of specimens. Observations
on the habits of the birds should be made by the pupils as they go
to and from school. For dissection use fresh specimens if possible.
If desirable a pigeon or dove may be used in place of the sparrow.

External structure.—Note in the sparrow the same
general arrangement of body parts as in the toad, the
body being divided into head, upper limbs, trunk, and
lower limbs. In the toad, however, all of the limbs are
fitted for walking and jumping, whereas in the sparrow the
anterior pair of appendages, the wzuzgs, are modified to
be organs of flight, and the posterior limbs are specially
adapted for perching. Note that the sparrow is covered
with feathers, some long, some short, in some places thick
-and in others thin, but all fitting together to form a com-
plete covering for the body. Note also that the anterior

end of the head is prolonged into a hard bony structure,
327

328 ELEMENTARY ZOOLOGY

the z//, covered with horny substance. This horny sub-
stance together with the feathers and horny covering of
the feet are modified portions of the skin. Note the long
guill-feathers attached to the posterior edge of the wing.
By these the bird sustains its flight. Other long quill-
feathers are attached to the posterior end of the body,
forming the ¢az/. By a system of muscles connected with
these feathers they act together, serving as a rudder during
fight and as a balancing contrivance when perching.
Note just above the bill two openings protected by tufts
of feathers. What are these openings? How are they
connected with the mouth 2? Note the large eyes, and at
the inner angle of each the delicate mzctztating membrane
which can be drawn over the ball. Does the bird have
external cars? Lift the feathers just above the tail (the
upper tail-coverts) and note a small median gland, the
owl-gland, from which the bird derives the oil with which
it oils its feathers. . Beneath the tail, mote the, opening
from the alimentary canal and from the kidneys and
reproductive organs. This is called the cloacal opening.
Examine in detail some of the feathers. In one of the
quill-feathers note the central stem or shaft composed of
two parts, a basal hollow gzaz//, which bears no web and
by which the feather is inserted in the skin, and a longer,
terminal, four-sided portion, the vachzs, which bears on
either side a web or vane. Each vane is composed of
many narrow linear plates, the dards, from which rise
(like miniature vanes) many Jéarbules. Each barbule
bears many fine Jarbicels and hamiul or hooklets. The
barbs of the feather are interlocked. How is this effected ?
The feathers which overlie the whole body and bear the
color pattern are called contour-feathers. How do they
differ from or correspond with the quill-feathers in struc-
ture? Soft feathers called down-feathers, or plumules,
cover the body more or less completely, being, however,

BRANCH CHORDATA; CLASS AVES: THE BIRDS 329

mostly hidden by the contour-feathers; the barbs of these
are sometimes not borne on a rachis, but arise as a tuft
from the end of the quill. Certain other feathers which
have an extremely slender stem and usually no vane,
except a small terminal tuft of barbs, are called ¢/read-
feathers, or filoplumules. ‘Yhey are rather long, but are
mostly hidden by the contour-feathers. In certain birds
they stand out conspicuously, as the vzdrzss@ about the
nostrils.

In the determination of birds by the use of a classifica-
try ey (see p. 359 it is necessary to be familiar
with the names applied to the various external regions of
the body and plumage, and with the terms used to denote
the special varying conditions of these parts. By refer-
ence to figure 133 the names of the regions or parts most
eenmnonly referred to may be learned. A full account
of all of the external characters with definitions of the
various terms used in referring to them may be found in
Coues’s ‘‘ Key to North American Birds.’’

TECHNICAL NOTE.—-Pull the feathers from the body, being care-
ful not to tear the skin.

In the fish and toad, already studied, the head is closely
joined to the trunk. How is it with the bird? Observe
that the kuee of the sparrow is covered by feathers and
that it is the azkle which extends down as the bare un-
feathered part to the adzgzts. How many digits have the
feet of the bird? How are they arranged ?

Internal structure (fig. 132).—TrcHNnicaL NoTE—With a
pair of scissors cut just beneath the skin anteriorly from the cloacal
opening to the angle of the lower jaw. Pin the sparrow on its back
by the wings, feet, and bill. Push back the skin from both sides
~ and pin out.

Note the large powerful pectoral muscles. Note a hard
median projection of bone, the sterzum, which is a large

ELEMENTARY ZOOLOGY

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BRANCH CHORDATA, CLASS’ AVES: THE BIRDS 331

keel-shaped bone with lateral expansions to which are
geracacd the 7z0s. Where are the largest and most
powerful muscles of the toad located? Where are they
in the fish? In the bird the most powerful muscles are
these pectoral muscles, which move the wings in flight.
TECHNICAL NOTE.—Cut the pectoral muscles from the left side
of the sternum, push back and pin to one side. With a strong pair
of scissors cut through the ribs on the left side of the sternum and
through the overlying bones. Lift the whole sternum, with the
right pectoral muscle attached, to the left side of the pan and pin it

down. Cut through the membrane which covers the viscera and
cover the dissection with water.

In this operation note the V-shaped wzskédone in front
of the sternum. It is composed of the two clavicles with
their inner ends fused. Note the stout coracotd bones
extending from the anterior end of the sternum to the
shoulder.

Note near the middle of the body the eart with the
large blood-vessels proceeding from it. Behind the heart
lies the large reddish-brown /zzer, and on the left side
below the liver is the large gzzzard or muscular stomach.
‘Note the wzscera folded over themselves in the body-
cavity. Push them temporarily aside and note in the
dorsal region under the heart large pinkish spongy sacs,
the dumgs. Uhese are attached by short tubes, the
bronchi, to the long cartilaginous ¢frachea. At the union
of the bronchi with the trachea is a small expansion with
cartilaginous walls, within which are stretched small bands
of muscles. This organ is the syrzzx, the song- or voice-
apparatus of the bird. It should be cut open and carefully
examined. Trace the trachea forward to its anterior end.
It opens by a glottzs into the larynx, a slightly swollen
- chamber with cartilaginous walls. Note the U-shaped
hyowd bone surrounding the front of the glottis. Through
a blowpipe or quill inserted into the glottis blow air into
the trachea and observe the inflation of the lungs and of

332 ELEMENTARY ZOOLOGY

certain large azr-sacs in the abdomen, which communicate
with them. ;

Beneath the trachea note the long wsophagus. Inflate
the cesophagus with a blowpipe and note how distensible
is its lower end near the breast. This distensible portion
is called the crop. If the alimentary canal be drawn out
straight the cesophagus will be found to run as an almost
straight tube down the left side of the body to the gizzard.
This latter organ has very thick muscular walls and in it
the food is ground up among the small bits of gravel it
contains. Extending from the gizzard near tae eutrance
of the cesophagus note the long pyloric loop of the intes-
tine called duodenum. Within this loop is a long pinkish
gland, the pancreas, which empties by a duct into the
duodenum. Into the duodenum also the overlying liver
empties its secretion of bile from the median-placed ¢a/-
bladder. From the duodenum the small intestine or tleum
extends with many convolutions to its exit through the
cloacal aperture. On the intestine near the cloacal open-
ine note a pair of glandular structures; the ea) Phe
short part of intestine between the czca and cloaca is
called the rectum. On the left side of the body beneath
the gizzard note a dark glandular structure, the spleen.

Make a drawing of the dissection as so far worked out.

TECHNICAL NOTE —Remove the alimentary canal, cutting it free
posteriorly atthe ceca and anteriorly just above the muscular gizzard.

Cut open the gizzard and note its structure. The contained sand
and gravel grains are picked up by the bird as it eats.

On either side of the throat note the well-defined ¢thyrozd
gland, in young sparrows will be noted on each side cf
the neck a mass of tissue, the remains of the ¢hymus
gland, which disappears in the adult.

Cut transversely through the lower end of the heart and
note that the ventricles are wholly distinct, whereas in the
toad and snake they are incompletely separated In the

Beamwed CHORDATA; CLASS AVES: THE BIRDS” (333

bird there is a complete double circulation. Its blood 1s
not mixed, the pure with the impure, as in the toad and
snake. Blood passing through the rzght auricle and ven-
tricle goes to the lungs; on its return to the heart purified,
it enters the /eft auricle and left ventricle, thence to pass
out over the body through the arteries.

Note the large corta given off from the left ventricle.
Note the two large branches, the zznominate arteries,
given off by it near its origin. Each innominate divides
into three smaller arteries, a carotid, branchial, and fpec-
toral. The aorta itself turns toward the back and con-
tinues posteriorly through the body as the dorsal aorta.
To the right auricle come three large veins, the rz¢/¢ and
left precave and the postcava. Each precava is formed
by three veins, the juwgu/ar from the head, the dranchial
from the wing, and the pectoral from the pectoral muscles.
Miie2poestcava comes from the liver. From the -right
ventricle go the short vzght and left pulmonary arteries
to the lungs, and from the lungs the blood is brought to
the left auricle through the rz¢/z and left pulmonary veins.

TECHNICAL NOTE.—-For a detailed study of the circulation of
the bird the teacher should inject the blood system of some larger
bird, as a pigeon or fowl, for a class-demonstration. (Fora guide,

use Parker’s ‘‘Zootomy,” p. 209, or Martin and Moale’s ‘‘ How to
Dissect a Bird,” pp. 135-140 and pp. 148, 149.)

In the posterior dorsal region of the body-cavity will
be found large three-lobed organs fitting into the spaces be-
tween the bones of the back on either side. These are the
kidneys, and from their outer margins on each side a ureter
runs posteriorly into the cloaca. Overlying the anterior
ends of the kidneys are the reproductive organs. In the
_male these glands consist of firm, whitish, glandular
bodies. From each runs a long convoluted vas deferens,
which enters the cloaca. This tube corresponds to the

egg-duct of the female. In the female the right egg-

334 ELEMENTARY ZOOLOGY

gland and eg g-duct or oviduct are wanting. The ft egg-
gland appears as a glandular mass; during the breeding
season yellow ova or cggs in various stages of develop-
ment project from its surface. The oviduct opens by a
funnel-shaped mouth near the egg-g/and and runs thence
to the cloaca. The eggs pass from the egg-gland into the
body-cavity, where they are caught in the upper end of
the oviduct and carried down and out through the cloacal
opening. It is in the oviduct that the egg derives its
accessory covering, which consists of a white or albumin-
ous portion, together with several enveloping membranes
and the hard shell enclosing all.

Remove the top of the skull and note the large drazn.
What portions of the brain make up the greater part of
it? Note the cifferences between this brain and that of
the toad. Trace the principal cranzal nerves. Work out
the spinal cord and principal spfzzal nerves. For an
account of the nervous system of the sparrow see Martin
and Moale’s. ‘* How to Dissect a Bird,” pp nae:

TECHNICAL NOTE.—For a study of the skeleton of the sparrow
a specimen should be cleaned by boiling in a soap-solution (see p. -
452).

In the sparrow’s skeleton note the compactness of the
skull and the fusion of its bones, Observe wie lone
cervical vertebre which support the skull, also the
thoracic vertebre bearing the ribs and sternum. How
many of each of these kinds of vertebrz are there? The
vertebrze posterior to the thorax are more or less fused
together to form the sacrum, which, with the pelvic girdle,
supports the /eg-bones. The bones of the tail consist of
a number of very small vertebra, some of which are fused
together. Note the correspondence between the bones
of the leg and those of the wing. What are the names
of each of the bones of each limb, and what are the corre-
sponding bones in the two limbs? The wings and legs

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Mantas CHORDATA: CLASS, AVES-:: THE BIRDS — 335

being modified for different uses, their various bones have
assumed different relations to each other and to the body,
for they are bent at directly opposite angles and the
attachment of muscles is different. Compare the skeleton
of the bird with that of the toad. (For a detailed account
meee Skeleton of the bird see Parker's -*Zootomy,'’
pp. 182-209, or Martin and Moale’s ‘‘ How to Dissect a
Bird,’’ pp. 102-125.)

Life-history and habits.—The English sparrow was
first introduced into the United States in 1850, and since
that time has rapidly populated most of the cities and
towns of the country. On account of its extreme adapt-
ability to surroundings, its omnivorous food-habits and its
fecundity it survives where other birds would die out.
It also crowds out and has caused the disappearance or
death of other birds more attractive and more useful.
The sparrow annually rears five or six broods of young,
laying from six to ten eggs ateach sitting. Had it no
enemies a single pair of sparrows would multiply to a
most astonishing number. The sparrow has, however, a
number of enemies, most common among them perhaps
being the ‘‘small boy,’’ but birds and mammals play the
chief part in the destruction. The smaller hawks prey
upon them, and rats and mice destroy great numbers of
their young and of their eggs whenever the nests can be
reached. The sparrow is omnivorous and when driven
to it is a loathsome scavenger, though at other times its
tastes are for dainty fruits. Its senses of perception are
of the keenest; it can determine friend or foe at long
range. The nesting habits are simple, the nests being
roughly made of any sort of twigs and stems mixed with
Bat, and feathers and placed in ‘cornices or trees. A
maple-tree in a small Missouri town contained at one time
thirty-seven of these nests.

336 ELEMENTARY ZOOLOGY

OTHER: BIRDS.

Birds are readily and unmistakably distinguishable from
all other kinds of animals by their feathers. They are
further distinguished from the reptiles on one hand by
their possession of a complete double circulation and by
their warm blood (normally of a temperature of from
100-112” F.), and from the mammals on tie errer by
the absence of milk-glands. There are about 10,000
known species of living birds; they occur in all countries,
being most numerous and varied in the tropics. Birds
are exceptionally available animals for the special atten-
tion of beginning students, because of their abundance and
conspicuousness and the readiness with which their varied
and interesting habits may be observed. The bright
colors and characteristic manners which make the identifi-
cation of the different kinds easy, the songs and flight,
and the feeding, nesting and general domestic habits of
birds are all excellent subjects for personal field-studies
by the students. We shall therefore devote more atten-
tion to the birds than to the other classes of vertebrates,
just as we selected the insects among the invertebrates for
special consideration.

Body form and structure.—The general body form
and external appearance of a bird are too familiar to need
description. The covering of feathers, the modification
of the fore limbs into wings, and the toothless, beaked
mouth are characteristic and distinguishing external
features. The feathers, although covering the whole of
the surface of the body, are not uniformly distributed, but
are grouped in tracts called pleryle, separated by bare or
downy spaces called apterza. ‘They are of several kinds,
the short soft plumules or down-feathers, the large stiffer
contour-feathers, whose ends form the outermost covering
of the body, the quill-feathers of the wings and tail, and

meee? CHORDATA, CLASS AVES: THE BIRDS. 337

the fine bristles or vibrisse about the eyes and nostrils
called thread-feathers. The fore limbs are modified to
serve as wings, which are well developed in almost all
bass: -dowever, the strange Kiwi or Apteryx of New
Zealand with hair-like feathers is almost wingless, and the
penguins have the wings so reduced as to be incapable of
- flight, but serving as flippers to aid in swimming under-
neath the water. The ostriches and cassowaries also
have only rudimentary wings and are not able to fly.
Legs are present and functional in all birds, varying in
Poem ieneth, shape of feet, etc., to suit the special
perching, running, wading, or swimming habits of the
various kinds. Living birds are toothless, although
certain extinct forms, known through fossils, had large
teeth set in sockets on both jaws. The place of teeth is
taken, as far as may be, by the bill or beak formed of the
two jaws, projecting forward and tapering more or less
abruptly to a point. In most birds the jaws or mandibles
are covered bya horny sheath. In some water and shore
forms the mandibular covering is soft and leathery. The
range in size of birds is indicated by comparing a humming-
bird with an ostrich.

Many of the bones of birds are hollow and contain air.
The air-spaces in them connect with air-sacs in the body,
which connect in turn with the lungs. Thus a bird’s
body contains a large amount of air, a condition helpful
of course in flight. The breast-bone is usually provided
with a marked ridge or keel for the attachment of the
large and powerful muscles that move the wings, but in
those birds like the ostriches, which do not fly and have
only rudimentary wings, this keel is greatly reduced or
wholly wanting. The fore limbs or wings are terminated
by three ‘‘fingers’’ only; the legs have usually four,
although a few birds have only three toes and the ostriches
but two.

338 ELEMENTARY ZOOLOGY

As birds have no teeth with which to masticate their
food, a special region of the alimentary canal, the gizzard,
is provided with strong muscles and a hard and rough
inner surface by means of which the food is crushed.
Seed-eating birds have the gizzard especially well devel-
oped, and some birds take small stones into the gizzard
to assist in the grinding. The lungs of birds are more
complex than those of batrachians and reptiles, being
divided into small spaces by numerous membranous par-
titions. They are not lobed as in mammals, and do not
lie free in the body-cavity, but are fixed to the inner dorsal
region of the body. Connected with the lyngs are the
air-sacs already referred to, which are in turn connected
with the air-spaces in the hollow bones. By this arrange-
ment the bird can fill with air not only its lungs but all
the special air-sacs and spaces and thus greatly lower its
specific gravity. The vocal utterances of birds are pro-
duced by the vocal cords of the syrinx or lower larynx,
situated at the lower end of the trachea just warere it
divides into the two bronchial tubes, the tracheal rings
being here modified so as to produce a voice-box con-
taining two vocal cords controlled by five or six pairs
of muscles. The air passing through the voice-box strikes,
against the vocal cords, the tension of which can be varied
by the muscles. In mammals the voice-organ is at the
upper or throat end of the trachea.

The heart of birds is composed of four distinct cham-
bers, the septum between the two ventricles, incomplete
‘in the Reptilia, being in this group complete 4 lmere1s
thus no mixing of arterial and venous blood in the heart.
The systemic blood-circulation being completely separated
from the pulmonic, the circulation is said to be double.
The circulation of birds is active and intense; they have
the hottest blood and the quickest pulse of all animals.
In them the brain is compact and large, and more highly

Beaved CHORDATA; CEASS AVES: THE BIRDS.* » 339

developed than in batrachians and reptiles, but the cere-
brum has no. convolutions as inthe mammals. Of the
special senses the organs of touch and taste are apparently
not keen; those of smell, hearing, and sight are well
developed. The optic lobes of the brain are of great size,
relatively, compared with those of other vertebrate brains,
and there is no doubt that the sight of birds is keen and
effective. The power of accommodation or of quickly
Pin@eme tie jocus of the eye is highly perfected.. The
structure of the ear is comparatively simple, there being
ordinarily no external ear, other than a simple opening.
The organs of the inner ear, however, are well developed,
fad tes wmcdoubtedly have excellent: hearing. The
nostrils open upon the beak, and the nasal chambers are
not at all complex, the smelling surface being not very
extensive. It is probable that the sense of smell is not,
as a rule, especially keen.

Development and life-history.— All birds are hatched
from eggs, which undergo a longer or shorter period of
incubation outside the body of the mother, and which are,
in most cases, laid in a nest and incubated by the parents.
The eggs are fertilized within the body of the female, the
mating time of most birds being in the spring or early
summer. Some kinds, the English sparrow, for example,
rear numerous broods each year, but most species have
only one or at most two. The eggs vary greatly in size
and color-markings, and in number from one, as with
many of the Arctic ocean birds, to six or ten, as with most
of the familiar song-birds, or from ten to twenty, as with
some of the pheasants and grouse. ‘The duration of in-
cubation (outside the body) varies from ten to thirty days
- among the more familiar birds, to nearly fifty among the
ostriches. The temperature necessary for incubation is
pom ae 10e;; ff). Among polygamous birds
(species in which a male mates with several or many

340 ELEMENTARY ZOOLOGY

females) the males take no part in the incubation and little
or none in the care of the hatched young; among most
monogamous birds, however, the male helps to build the
nest, takes his turn at sitting on the eggs, and is active in
bringing food for the young, and in defending them from
enemies. The young, when ready to hatch) break the
egg-shell with the ‘‘egg-tooth,’’ a horny pointed projec-
tion on the upper mandible, and emerge either blind and

Fic. 134.—The nest and eggs of the black phcebe, Sayornds nigricans.
(Photograph by J. O. Snyder.)

almost naked, dependent upon the parents for food until
able to fly (altricial young), or with eyes open and with
body covered with down, and able in a few hours to feed
themselves (precocial young). |
More details regarding the eggs, nest, and young of
birds will be given later in this chapter.
Classification.—The class Aves is usually divided into
numerous orders, the number and limits of these as pub-
lished in zoological manuals varying according to the

mRAaNCH CHORDATA; CEASS AVES: THE BIRDS. . 341

opinions of various zoologists. The rank of an order in
this group is far lower than in most other classes. In
other words, the orders are very much alike and are
recognized mainly for the convenience in breaking up the
vast assemblage of species. In North America practically
all the ornithologists have agreed upon a scheme of
classification, which will therefore be adopted in this book.
According to this classification the eight hundred (approxi-
mately) known species of North American birds represent
seventeen orders. Certain recognized orders, for example,
the ostriches, are not represented naturally in North
America at all. As birds can usually be readily identi-
fied, the species being easily distinguished by general
Exbenial appearance, and. as there are many excellent
book-guides to their classification, the beginning student
can specially well begin with them his study of systematic
zoology, which concerns the identification and classifica-
tion of species. Ina later paragraph are given therefore
some suggestions for field and laboratory work in the
determination of local bird-faunz. In the following para-
graphs each of the American orders is briefly discussed, as
is also the foreign order of ostriches.

The ostriches, cassowaries, etc. (Ratite).—The os-
triches, familiar to all from pictures and to some from
live individuals in zoological gardens and menageries,
or stuffed specimens in museums, together with a few
other similar large species, are distinguished from all
other birds by having the breast-bone flat instead of
keeled. There are about a score of species of ostriches
and ostrich-like birds all confined to the southern hemi-
sphere. In them the wings are so reduced that flight is
impossible, but the legs are long and strong, and they can
run as swiftly as a galloping horse. They are said to have
a stride of over twenty teet. They use their legs also as
weapons, kicking viciously when angered. The true

342 ELEMENTARY ZOOLOGY

ostriches (Struthzo camelus) (fig. 135) live in Africa. They
are the largest living birds, reaching a height of nearly
seven feet and weighing as much as two hundred pounds.
They are hunted for their feathers, and are now kept in
captivity and bred in South Africa and California for
the same purpose. About five million dollars’ worth of

Fic. 135.—Ostriches on ostrich farm at Pasadena, California. (Photo-
graph from life.)

ostrich-feathers are used each year. The eggs, which are
from five to six inches long and nearly five inches thick,
are laid in shallow hollows scooped out in the sand of the
desert. The male undertakes most of the incubation,
although when the sun is hot no brooding is necessary.

BRANCH CHORDATA; CLASS AVES: THE BIRDS — 343

The young (fig. 136) hatch in from seven to eight weeks,
and can run about immediately.

The rheas, found in South America, and the cassowaries
of Australia are the only other living ostrich-like birds.

Fic. 136.—Young ostriches just from egg; on ostrich farm at Pasadena,
California. (Photograph from life.)

Their feathers are of much less value than those of the
true ostrich.

The loons, grebes, auks, etc. (Pygopodes).—The
loons, grebes, and auks are aquatic birds, living in both
ocean and fresh waters. Their feet are webbed or lobed,
and their legs set so far back that walking is very difficult
and awkward. But all the birds of this order are excel-
lent swimmers and divers. They are distinctively the
diving birds. They have short wings and almost no tail.
The dab-chick or pied-billed grebe (Podilymbus podiceps)

is common in ponds over all the country. Its eggs are

- laid in a floating nest of pond vegetation and are often

covered with decaying plants. The horned grebe
(Colymbus auritus) is common west of the Mississippi in
lakes and ponds. The loon or great northern diver

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BRANCH CHORDATA; CLASS AVES: THE BIRDS 345

(Gavia timber), found all over the United States in winter,
is the largest of this group, reaching a length (from bill to
tip of tail) of three feet. It is black above with many
small white spots, and with a patch of white streaks on
each side of the neck and on the throat; it is white on
breast and belly. The female is duller, being brownish
instead of black.

The auks, guillemots, puffins, and murres (fig. 137)
are ocean birds which gather, in the breeding season, in
countless numbers on the bleak rocks and inaccessible
cliffs of the northern oceans. Each female lays a single
egg (in some cases two or at most three) on the bare rock
or in acrevice or sort of burrow. These birds mostly fly
well, but are especially at home in the water, feeding ex-
clusively on animal substances found there. A famous
species is the great auk (diéca impennis), which has
become extinct in historical times. The last living speci-
men was seen in 1844.

The gulls, terns, petrels, and albatrosses (Longi-
pennes).-— The Longipennes are water-birds, mostly
maritime, with webbed feet and very long and pointed
wings. They are all strong flyers, and most of them
are beautiful birds. Their prevailing colors are white,
slaty or lead-blue, black, and, in the young, mottled
brownish. They subsist chiefly on fish, but any animal
substance will be eagerly picked up from the water; some
of the gulls forage inland. Occasionally great flocks may
be seen following a plow near the shore and feeding on
the grubs and worms exposed in the freshly-turned soil.
Some of the gulls, like the great black-backed gull (Larus
marinus), attain a length of two and one-half feet. The
terns (Szerva) are mostly smaller than the gulls, have a
bill not so heavy and not hooked, and have the tail
forked.

The fulmars, shearwaters, petrels, and albatrosses are

SAN So ELEMENTARY ZOOLOGY

strictly maritime. The albatrosses are ver daree. the
largest being three feet long with a spread of wing of
seven. feet. They are often found fying casiywever tie
open ocean at great distances from land. Like the auks
and puffins, the fulmars and shearwaters gather in extra-
ordinary numbers on rocky ocean islets or cliffs of the
coast to breed.

The cormorants, pelicans, etc. (Steganopodes).— The
Steganopodes are water-birds with full-webbed feet, and
prominent gular pouch, swimmers rather than flyers like
the Longipennes. The cormorants (Phalacrocorax) in-
habit rocky coasts and are green-eyed, large, heavy,
black birds with greenish-purple and violet iridescence;
they are among the most familiar of seashore birds. They
feed chiefly on fish and dive and swim under water with
great ability. Cormorants are rather gregarious, keeping
together in small groups when fishing, migrating often in
great flocks, and in the breeding season gathering in
immense numbers on certain rocky cliffs or islets. They
build their nests of sticks and sea-weed; the eggs are
three or four, and usually bluish green with white, chalky
covering substance.

The pelicans are large, long-winged, short-legged
water-birds with enormous bill and large gular sac which
is used as a dip-net to catch fish. There are three species
in North America, the white pelican (Pelecanus erythro-
rhynchus) occurring over most of the United States, the
brown pelican (P. fuscus) of the Gulf of Mexico, and
the California brown pelican (P. calzfornicus) of the Pacific
coast. 7 .

An interesting member of this order is the famous
- frigate or man-of-war bird (/regata aquzla), with very long
wines and tail and feet extraordinarily smile ne
frigates have the greatest command of wing of all the
birds. They cannot dive and can scarcely swim or walk.

bene CHORDATA: CLASS AVES: THE BIRDS. 347

The ducks, geese, and swans (Anseres).—The familiar
wild ducks, of which there are forty species in North
American fresh and salt waters; the geese, of which there
are sixteen species, and the three species of wild swans
Bensemute the order Anseres.-. The. bill.in these-birds is
more or less flattened and is also lamellate, i.e. furnished
along each cutting-edge with a regular series of tooth-like
processes; the feet are webbed, and the body is heavy
and flattened beneath. Of the fresh-water. or inland
ducks, the more familiar are the mallard (Azas doschas),
a large duck with head (male) and upper neck rich glossy
green; the blue-winged teal (Querquedula discors) and
green-winged teal (/Vettzon carolinense); the shoveller
(Spatula clypeata) with spoon-shaped bill; the beautiful
crested wood-duck (Azx sfonsa); the expert diver, the
plump little ruddy duck (Avzsmatura rubtda), and others.
Of the coastwise ducks, the canvas-back (Aythya val-
fisnerta) is famous because of its fine flavor, while among
the strictly maritime ducks the eiders (Somaterza), which
live in Arctic regions, are well known for their fine down.
Of the geese, the commonest is the well-known Canada
goose (Lranta canadensts), while the pure-white snow-
goose (Chen hyperborea), with black wing-feathers and
red bill, is not unfamiliar. The wild swans (O/or) are the
largest birds of the order, and are less familiar than the
ducks and geese.

The ibises, herons, and bitterns (Herodiones).—The
tall, long-necked, long-legged, wading birds, known as
herons and ibises, compose a small order, the Herodiones,
of which but few representatives are at all familiar.
Perhaps the most abundant species is the green heron
(Ardea virescens) or ‘‘fly-up-the-creek,’’ one of the
smaller members of the order. The crown, back, and
wings are green, the neck purplish cinnamon, and the
throat and fore neck white-striped. This bird is com-

348 ELEMENTARY ZOOLOGY

monly seen perching on an overhanging limb, or flying
slowly up or down some small stream. The great blue
heron (Ardea herodias) is common over the whole
country. It is four feet long and grayish blue, marked
with black and white. It may be seen standing alone in
wet meadows or pastures, or flying heavily, with head
drawn back and long legs outstretched. It breeds
singly, but oftener in great heronries, in trees or bushes.
Its large bulky nests contain three to six dull, greenish-
blue eggs about two and one-half inches long. The white
egrets of the Southern States are shot for their plumes and
have been locally exterminated in some places. The
night-herons (Vyctzcorax) differ from the other forms in
having both the neck and legs-short. The bittern
(Botaurus lentiginosus), Indian hen, stake-driver, or
thunder-pumper, as it is variously called, is a familiar
member of the order, found in marshes and wet pastures,
and known by its extraordinary call, sounding like the
‘<strokes of a mallet ona stake.’’ In color it is brownish,
freckled and streaked with tawny whitish and blackish.
Its nest ts made on the ground; its eggs, from three to
five in number, are brownish drab and about two inches
long. | .

The cranes, rails, and coots (Paludicola). —The cranes,
of which three species are known in North America, are
large birds with long legs and neck, part of the head being
naked or with hair-like feathers. The rare whooping
crane (Grus americana) is pure white with black on the
wings, and is fifty inches long from tip of bill to tip of
tail. The sand-hill crane (G. mexicana) is slaty gray or
brownish in color, never white, and although rare in the
East is quite common in the South and West. Cranes
build nests on the ground, and lay but two eggs, about
four inches long, brownish drab in color with large irreg-
ular spots of dull chocolate-brown.

BRANCH CHORDATA; CLASS AVES: THE BIRDS 349

The rails are smaller than the cranes, with short wings
and very short tail. They live in marshes and swamps,
and in flying let the legs hang down. Their legs are
strong, and for escape they trust more to speed in running
than to flight. They are hunted for food. The most
aaneent fail is the -‘‘Carolina. crake’’.or ‘‘sora’’
(Porzana carolina), small and olive-brown with numerous
sharp white streaks and specks. Many of these birds are
shot each year during migration in the reedy swamps of
the Atlantic States. The American coot or mud-hen
(Fulica americana), dark slate-color with white bill, is one
of the most familiar pond-birds over all temperate North
America. Its nest consists of a mass of broken reeds

esting on the water; the eggs number about a dozen,
and are clay-color with pin-head dots of dark brown.

The snipes, sandpipers, plover, etc. (Limicole).—The
large order Limicole, the shore-birds, includes the
slender-legged, slender-billed, round-headed, rather
small wading birds of shores and marshes familiar to
us as snipes, plovers, sandpipers, curlews, yellow-legs,
sandpeeps, turnstones, etc. Most of them are game-
birds, such. forms.as the woodcock and Wilson’s or
English snipe being much hunted. The food of these
birds consists of worms and other small animals, which
are chiefly obtained by probing with the rather flexible,
sensitive, and usually long bill in the mud or sand. The
killdeer (4 gvalitts voctfera), familiar to all in its range
by its peculiar call and handsome markings, the upland
or field plover (Lartramza longicauda), with its long legs
and melodious quavering whistle, the tall, yellow-shanked
‘‘telltale ’’ or yellow-legs (Zotanus melanoleucus) of the
marshes and wet pastures, are among the most wide-
spread and familiar species of the order. On the seashore
the dense flocks of white-winged, whisking sandpipers
and the quickly running groups of plump ring-necked

359 ELEMENTARY ZOOLOGY

plover are familiar’ sights. One of-the largest birds of
this order is the long-billed curlew (Wumenzus longirostrts)
of the upland pastures. The bill of the curlew is long
and curved downwards. The nests of these shore-birds
are made on the ground and are usually littie more than
shallow depressions in which the few spotted eggs (four
is a common number) are laid. The young are precocial.

The grouse, quail, pheasants, turkeys, etc. (Galline).
—The Galline include most of the domestic fowls, as the
hen, turkey, peacock, guinea-fowls, and pheasants, and
the grouse, quail, partridges, and wild turkeys. The
chief game-birds of most countries belong to this order.
They have the: bill short, heavy, convex ausscony,
adapted for picking up and crushing seeds and grains
which compose their principal food. Their legs are strong
and usually not long, and are often feathered very low
down. The Galline are mostly terrestrial in habit and
are sometimes known as the Rasores or ‘“scratchers.
Among the more familiar wild gallinaceous birds are the
quail or ‘‘ Bob white "’ (Colzmus virginianus), abundant in
eastern and* central- United States? tae “tutied™ rouse
(Bonasa umbellus) of the Eastern woods, and the prairie-
chicken (Zympanuchus americanus) of the Western prairies.
The sage-hen (Centrocercus urophastanus), the largest of
the American grouse, reaching a length of two and one-
half feet, is an interesting inhabitant of the sterile sage-
brush plains of the West. The ptarmigan (Lagopus) or
snow-grouse, represented by several species, are found
either among the rocks and snow-banks above timber
line on high «mountains, or in the Arctic regions: In
summer their plumage is brown and white; in winter they
turn pure white to harmonize with the uniform snow-
covering: On -the Pacific coast are “Severdlapecies of
quail, all differing much from those of the Hast. Iiese
Western species have beautiful crests of a few or several

mete CHORDATA: CLASS AVES: THE BIRDS». 351

long plume-feathers, the body-plumage being also un-
usually beautiful. The eggs of all the Galline are numer-
ous and are laid in a rude nest or simply in a depression
on the ground. In many of the species polygamy is the
tale. The young are precocial.

The doves and pigeons (Columbz).—The doves and
pigeons constitute a small order, the Columbz, closely
related to the Galline. A distinguishing characteristic
of the Columbz lies in the bill, which is covered at the
base with a soft swollen membrane or cere in which the
nostrils open. The members of this order feed on fruits,
seeds, and grains. Our most familiar wild species is the
mourning-dove or turtle-dove (Zenatdura macroura) found
abundantly all over the country. It lays two eggs ina
ieeccrciieina, nest in a low tree or on-the ground: . The
beautiful wild or passenger pigeon (Ecfopistes migratorius)
was once extremely abundant in this country, moving
abouy ia tremencous. flocks-in the: Eastern and: Central
States. But it has been so relentlessly hunted that the
species is apparently becoming extinct. In the Rocky
and Sierra Nevada mountains is a rather large dove, the
band-tailed pigeon (Columta fasciata), which subsists ,
chiefly on acorns. The domestic pigeon represented by
numerous varieties, pouters, carriers, ruff-necks, fan-tails,
etc., is the artificially selected descendant of the rock-dove
(Columba livia). Vhe young of all pigeons are altricial.

The eagles, owls, and vultures (Raptores).—The
Bites or prey. Compose one of the larger orders, the
members of which are readily recognizable. In all the
bill is heavy, powerful, and strongly hooked at the tip.
The feet are strong, with long, curved claws (small in the —
vultures) and are fitted for seizing and holding living
prey, such as smaller birds, fish, reptiles, and mammals
which constitute the principal food of the true raptorial
species. Ihe vultures feed on carrion. The turkey

Sp ELEMENTARY ZOOLOGY

buzzard (Cathartes aura) is the most familiar of the three
species of carrion-feeding Raptores found in the United
States. The buzzard nests on the ground or in hollow
stumps or logs, and lays two white eggs (sometimes only
one) blotched with brown and purplish. The largest
North American vulture is the California condor (Pseudo-
oryphus californianus), which attains a length of four and
one-half feet, with a spread of wing of nine and one-half

Fic. 138.—Screech-owl, J/egascops asio. (Photograph by A. L, Princetor
permission of Macmillan Co.)
feet. Of the eagles, the most widespread and commonest
is the bald eagle (laletus leucocephalus). It is three
feet long and when adult has the head and neck white.
The golden eagle (Aguzla chrysetos) has the neck and
head tawny brown. Of the many species of hawks, the
marsh harrier (C7zrcus hudsonius), abundant all over the
country and readily known by its white rump, is one of

Peer. CHORDATA = CLASS: AVES: THE -BIRDS _ 353

the most familiar. The name ‘‘chicken-hawk’’ is given
to two or three different species of large broad-winged
hawks of the genus Auzeo. The stout little sparrow-hawk
(Falco sparvertus), common over the whole country, is
familiar and readily recognizable by its pronounced bluish
and black wings and black-and-white banded chestnut
fark ltesether fifty species of hawks and eagles are
found in this country. Of the owls, the barn-owl (S¢rzx
pratincola) with its long triangular face and handsome
mottled and spotted tawny coat is more or less familiar.
the great horned owl (8x60 virginianus), the snowy ow]
(Vyctea nyctea), and the great gray owl (Scotzapter
cinerea) are the common large species, while the red
screech-owl (Wegascops asto) (fig. 138), the most abundant
owl in the country, and the strange burrowing owl
(Spevtyto cunicularia), which lives in the holes of prairie-
dogs and ground-squirrels in the West, are familiar smaller
ones. . [Thirty-two species of owls are recorded from
North America.

The parrots (Psittaci).—The parrots, of which only
one species is native in the United States, constitute an
interesting order of birds, the Psittaci. They are abun-
@ant im tropical, America. They have a very thick
strongly hooked bill, with a thick and fleshy tongue.
The feet have two toes pointing forward and two back-
ward. The plumage is usually brightly and gaudily
colored. The natural voice is harsh and discordant, but
many of the species can imitate with surprising cleverness
the speech of man. Parrots are long-lived and usually
@oeitc, and are much kept'as pets. The single native
species, the Carolina paroquet (Conurus carolinensis), is
about a foot in length, is green, with yellow head and
neck and orange-red face. Its range once extended from
the Gulf of Mexico north to the Great Lakes, but it has
been nearly exterminated in all the States but Florida.

354 _ ELEMENTARY ZOOLOGY

The cuckoos and kingfishers (Coccyges). — The
cuckoos and kingfishers are regarded as constituting an
order, Coccyges, a small group whose members are with-
out any definite bond of union. Only ten species of North
American birds belong to this order. The yellow-billed
and black-billed cuckoos (Coccyzus) or ‘‘ rain-crows ’’ are
long-tailed, slender, lustrous drab birds, which lay their
eggs in the nests of others. They are notable for their
peculiar rolling call. On the plains and hills of California.
and the southwest lives the road-runner or chaparral cock
(Geococcyx caltfornianus), a strange bird belonging to the
cuckoo family. It is nearly two feet long, of which length
the tail makes half. These birds run so rapidly that a
horse is little more than able to keep up with them. They
feed on fruits, various reptiles, insects, creme one
common kingfisher of this country, the belted kingfisher
(Ceryle alcyon), a thick-set, heavy-billed, ashy blue-and-
white bird, is familiar along streams. As it flies swiftly
alone it gives its rattling cry. It nests in deep holes in
the stream-banks, and lays six or eight crystal-white
spheroidal eggs.

The woodpeckers (Pici).—The familiar woodpeckers
and sap-suckers compose a well-defined order, Pici, which
is represented in North America by twenty-five species.
The bill of the woodpecker is stout and strong, usually
straight, fitted for driving or boring into wood; the tongue
is long, sharp-pointed, and barbed, fitted for spearing
insects. The feet have two toes turned forward and two
backward; the tail-feathers are stiff and sharp-pointed
and help support the bird as it clings to the vertical side
of a tree-trunk or branch (fig. 139). The food of most
woodpeckers consists chiefly of insects, usually wood-
boring larvae (grubs). These birds do much good by
destroying many noxious insect pests of trees: A few
species, the true sap-suckers, probably feed on the sap of

BeaNeH CHORDATA; CLASS AVES: THE BIRDS .355

trees. Their nests are made in holes in trees, and the
eggs are pure white and rounded. The harsh and shrill
cries of the woodpeckers are familiar to all.

The largest and one of the most interesting wood-
peckers is the ivory-billed (Campephilus principalis),
twenty inches long, glossy blue-black, with a high head-

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crest which is scarlet in the male. This bird lives in the

heavily wooded swamps of the Southern States. Among

the more abundant and widespread, and hence better

known, woodpeckers are the yellow-hammers (fig. 139)

356 ELEMENTARY ZLOCE@Gr

or flickers (Colaptes auratus in the East, C. cafer in the
West), the red-headed woodpecker (Welanerpes erythro-
cephalus), with its crimson head and neck and pure-white
‘vest’; and the black-and-white downy (Dryobatcs
pubescens) and hairy (DY. villosus) woodpeckers or ‘‘sap-
suckers.’’ The California woodpecker (VW. formicivorus),
a near relative of the red-headed woodpecker, has the
curious habit of boring small holes in the bark of oak- or
pine-trees and sticking acorns into these holes. Some-
times thousands of acorns are put into the bark of one
tree, to which the birds come occasionally to break open
some acorns and feed on the grubs inside.

The whippoorwills, chimney-swifts and humming-
birds (Macrochires).—All the birds of this order are
remarkable for their power of flight. They have long and
pointed wings; their feet are small and weak and used
only for perching or clinging. All feed on insects, which
are caught on the wing by the short-beaked, wide-
mouthed swifts and whippoorwills and extracted from
flower-cups by the humming-birds with their long and
slender bills. The whippoorwill (Axtrostomus voctferus)
is common in the woods of the East and is readily known
by its call. Its two brown-blotched white eggs are laid
loose on the ground or on a log or stump. The night-
hawk (Chordetles virginianus), common over the whole
country, is seen at twilight flying vigorously about in
its search for insects. Its nesting habits are like those
of the whippoorwill. The sooty-brown chimney-swifts
(Chetura pelagica), popularly confused with the swallows,
are the common inhabitants of old chimneys, in which they
build their curious saucer-shaped open-work nests. ‘Their
egos are pure white and number four or fme>) OF the
humming-birds but one species, the ruby-throat (7rochzlus
colubris), is to be found in the Eastern Statesyeeume in the
western and especially southwestern parts of the country

Beane CHORDATA. GLASS AVES: THE BIRDS. 357

several other species occur.

have been found in the
Haired States. The nests
(fig. 140) of the hummers
are very dainty little cups
lined with hair or wool or
‘che
throat lays two tiny pure-
white eggs.

The perchers (Passeres).
"Nearly one-half.of the
birds of North America be-
long to the great order Pas-

plant - down. ruby-

seres, and of all the known
birds of the world more than
half are included init. The
Passeres or perching birds
include the familiar song-
birds and a great majority
of the birds of the garden,
the forest, the roadside, and
twe tera. — the feet of these
birds always have four toes
and are fitted for perching.
The syrinx or musical ap-
paratus 1s,

in most, well

developed. The nesting
and other domestic habits
are various, but the young
are: always hatched in a
helpless condition and have
to be fed and otherwise
cared for by the parents for

a longer or shorter time.

Pies

In all seventeen species

a ea a
140.—Nest and eggs of ruby-
throat humming bird, Zvochilus
colubris, seen from above, in apple-
tree. (Photograph by E. G. Tabor;
permission of Macmillan Co.)

The North American species of this order are grouped into

358 ELEMENTARY ZOOLOGY

eighteen families, as the fly-catcher family (Tyrannide),
the crow family (Corvide), the sparrows and finches
(Fringillide), the swallows (Hirundinide), the warblers
(Mniotiltida), the wrens (Troglodytide), the thrushes,
robins and bluebirds (Turdida), -ete: 7 Tig) tae hook
nothing can be said of the various species which belong
to this order. However, as the passerine birds are

Fic. 141.—Horned larks, Ofocoris alpestris, and snowflakes, Plectrophenax
nivalis. (Photograph from life by H. W. Menke; permission of Mac-
millan Co.)

those which most immediately surround us and which, by
their familiar songs and nesting habits, most interest us,
the.out-door study of birds by beginning students will be
devoted chiefly to the members of this order sagdimany
species will soon be got acquainted with. The robin and
bluebird will introduce us to the shyer and less familiar
song-thrushes; the study of the kingbird or bee-martin

BeANCH CHORDATA; CEASS AVES: THE BIRDS 359

will interest us in some of the other fly-catchers; from the
familiar chipping sparrow and tree-sparrow we shall be
led to look for their cousins the swamp-sparrows and
song-sparrows, and the larger grosbeaks and cross-bills,
and so on through the order.

Determining and studying the birds of a locality.—
To identify the various species of birds in the locality of
the school it will be necessary to have some book giving
the descriptions of ail or most of the species of the region,
with tables and keys for tracing out the different forms.
Such manuals or keys are numerous now; the study of
birds is one of the most popular lines of nature study, and
a host of bird books has been published in the last few
Meese ie est ceneral manual is Coues s.‘‘ Key to the
Birds of North America,’’ which includes not only keys
for tracing and descriptions of all the known species of
birds on this continent, but also accounts of the distribu-
tion, of the nesting and eggs, and of the plumage of the
young birds, besides a thorough introduction to the
anatomy and physiology of birds, and directions for col-
lecting and preserving them. Jordan's ‘‘Manual of
Vertebrates '’ gives keys and short descriptions of the
birds found east of the Missouri River; Chapman’s
‘« Handbook of the Birds of Eastern North America ’’ is
excellent. To be able to use.these manuals it is neces-
sary to have the bird’s body in hand; and that means
usually death for the bird. Recently there have been
published several bird-keys which attempt to make it
possible to determine species, the commoner ones at any
rate, without such close examination. The birds in these
books are usually grouped wholly artificially (without any
reference to their natural relationships) according to such
salient characteristics as color, markings, size, habit of
perching, or running, or flying, etc. These characteris-
tics are such as can presumably be made out in the living

360 ELEMENTARY ZOOLOGY

bird by aid of an opera-glass or often with the unaided eye.
Such books make no pretence to be scientific manuals nor
to include any but the more usual and strongly marked
species. They are usually limited 467 espe ofa
restricted region. Such books are readily obtainable.
There are several popular illustrated ‘+ bird-magazines ”’
devoted to accounts of the life and habits of birds. Of
these +: Bird-lore ’’ is the organ of the Audubon Society
for the Protection of Birds.

Fic. 142.—Western chipping sparrow, Sfizella socialis arizonae. (Photo-
graph from life by Eliz. and Jos. Grinnell.)

In trying to become acquainted with the birds of a
locality it must be borne in mind that the bird-fauna of
any region varies with the season. Some birds live ina
certain region all the year through; these are called vesz-
dents. Some spend only the summer or breeding season
in the locality, coming up from the South in spring and
flying back in autumn; these are summer residents. Some
spend only the winter in the locality, coming down from

BRANCH CHORDATA; CLASS AVES: THE BIRDS 361

the severer North at the beginning of winter and going
back with the coming of spring; these are wzzter rest-
dents. Some are to be found in the locality only in spring
and autumn as they are migrating north and south
between their tropical winter quarters and their northern
summer or breeding home; these are mzgrants. And
finally an occasional representative of certain bird species
whose normal habitat does not include the given locality
at all will appear now and then blown aside from its
regular path of migration or otherwise astray; these are
visittants. As to the relative importance, numerically,
of these various categories among the birds which may be
found in a certain region and thus form its bird-fauna we
may illustrate by reference to a definite region. Of the
351 species of birds which have been found in the State
of Kansas (a region without distinct natural boundaries
and fairly representative of any Mississippi valley region
Or similar extent), 51 are all-year. residents; 125 are
amuamicr fresients; 36 are winter: residents;- 104 are
migrants, and 35 are rare visitants.

It must also be kept in mind in using bird-keys and
descriptions to determine species that the descriptions and
keys refer to adult birds, and in ordinary plumage.
Among numerous birds the young of the year, old enough
to fly and as large as the adults, still differ considerably
in plumage from the latter; males differ from females,
and finally both males and females may change their
plumage (hence color and markings) with the season.
The seasonal changes of plumage accomplished by molt-
ing may be marked or hardly noticeable. ++ All birds
get new suits at least once a year, changing in the fall.
' Some change in the spring also, either partially or wholly,
while others have as many as three changes—perhaps, to
a slight extent, a few more. . . . It is claimed by some
that now all new colors are acquired by molt, and by

362 ELEMENTARY ZOOLOGY

others that in some instances (young hawks) an infusion
or loss, as the case may be, of pigment takes place as the
feather forms, and continues so long as it grows.”’

There is much lack and uncertainty of knowledge con-
cerning the molting and change of plumage by birds, and
careful observations by bird-students should be made on
the subject.

In connection with learning the different kinds of birds
in a-locality, together. with their manses; ossemjaions
should be made, and: notes of them recorded, on their
habits and on the relation or adaptation of structure and
habit to the life of the bird. Some of the special subjects
for such observation are pointed out in the following
paragraphs. A suggestive book, treating of the adapt-
ive. structure: and the life of birds is Baskets e.-9 The
Story ol ther binds. ~

Bills and feet.—-The interesting adaptation of struc-
ture to special use is admirably shown in the varying
character of the bills and feet of birds:. The varieusteed- |
ing habits and uses of the feet of different birds are readily
observed, and the accompanying modification of bills
and feet can be readily seen in birds either freshly killed
or preserved as ‘* bird-skins. Such skins may be made
as directed on p. 467, or may be bought cheaply of
taxidermists. A set of such skins, properly named, will
be of great help in studying birds, and should be in the
high-school collection. In some cases the general struc-
ture of feet and bills may be seen in the live birds by the
use of an epera-glass.. The characters om biliseamd tect
are much used in the classification of birds, so that any
knowledge of them gained primarily in the study of
adaptations will have a secondary use in classification work.

Note the foot of the robin, bluebird, catbird, wrens,
warblers and other passerine or perching birds. It has
three unwebbed toes in front, and a long hind toe per-

yy}

BeevGH CHORDATA; GLASS AVES: THE BIRDS 362

fectly opposable to the middle front one. This is the
perching foot. Note the so-called zygodacty/ foot of the
woodpecker, with two toes projecting in front and partly
yoked together, and two similarly yoked projecting
behind. Note the webbed swimming foot of the aquatic
birds; note the different degrees of webbing, from the
totipalmate, where al] four toes are completely webbed,
palmate, where the three front toes only are bound

Fic. 143.—Russet-backed thrush, Zurdus ustulatus.. (Photograph from
life by Eliz. and Jos. Grinnell.)

together but the web runs out to the claws, to the semz-
balmate, where the web runs out only about half way.
Note the /obate foot of the coots and phalaropes. Note
the long slender wading legs of the sandpipers, snipe
and other shore birds; the short heavy strong leg of the
divers; the small weak leg of the swifts and humming
birds, almost always on the wing; the stout heavily nailed
foot of the scratchers, as the hens, grouse, and turkeys;
and the strong grasping talons, with their sharp long

364 ELEMENTARY ZOOLOGY

curving nails, of the hawks and owls and other birds of
prey. In all these cases the fitness of the structure of the
foot to the special habits of the bird is apparent.

Similarly the shape and structural character of the bill
should be noted, as related to its use, this being chiefly con-
cerned of course with the feeding habits. Note the strong
hooked and dentate bill of the birds of prey; they tear
their prey. Note the long slender sensitive bill of the
sandpipers; they probe the wet sand for worms. Note
the short weak bill and wide mouth of the night-hawk
and whippoorwwill and of the swifts and swallows; they
catch insects in this wide mouth while on the wing. Note
the flat lamellate bill of the ducks; they scoop up mud
and water and strain their food from it. Note the firm
chisel-like bill of the woodpeckers; they bore into hard
wood for insects. Note the peculiarly crossed mandibles
of the cross-bills; they tear open pine-cones for seeds.
Note the long sharp slender bill of the humming-birds;
they get insects from the bottom of flower-cups. Note
the bill and foot of any bird you examine, and see if they
are specially adapted to the habits of the bird.

The tongues and tails of birds are two other structures
the modifications and special uses of which may be readily
observed and studied. Note the structure and special use
of the-tongue and tail of the woodpeckesss mere the
tongue of the humming-bird; the tail of the grackles.

Flight and songs.—The most casual observation of
birds reveals differences in the flight of different kinds, so
characteristic and distinctive as to give much aid in
determining the identity of birds im natusé=ie=Note- the
flight of the woodpeckers; it identifies them unmistakably
in the air. Note the rapid beating of the wings of quail
and grouse; also of wild ducks; the slow heavy flapping
of the larger hawks and owls and of the crows; and the
splendid soaring of the turkey-buzzard and of the gulls.

BRANCH CHORDATA; CLASS AVES: THE BIRDS — 365

This soaring has been the subject of much observation
and study but is still imperfectly understood. The soaring
bird evidently takes advantage of horizontal air-currents,
and some observers maintain that upward currents also
must be present. The principal hopes for the invention
of a successful flying-machine rest on the power of soaring
possessed by birds. The speed of flight of some birds 1s
enormous, the passenger-pigeon having been estimated

Fic. 144.—Oriole’s nest with skeleton of blue jay suspended from it; the
blue jay probably came to the nest to eat. the eggs, became entangled
in the strings composing the nest, and died by hanging. (Photograph
by 5. J. Hunter.)

to attain a speed of one hundred miles an hour. The
long distances covered in a single continuous flight by
certain birds are also extraordinary, as is also the total
distance covered by some of the migrants. ‘‘It is said
that some plovers that nest in Labrador winter in Pata-
gonia, their long wings easily carrying them this great
distance.’’

366 ELEMENTARY ZOOLOGY

Varying even more than the manner and power of
flight among different birds are the vocal utterances, the
cries and calls and singing. By their calls and songs
alone many birds may be identified although they remain
unseen. The field-student of birds comes to know them
by their songs; knows what birds they are; knows what
they are doing or not doing; knows what time in their
life-season it is, whether they are mating, or brooding, or
preparing to migrate; knows whether they are frightened,
or self-confident, whether in distress or happy. Little
urging and suggestion are needed to induce the student
to attend to the songs. But the naturalist should not
only hear and enjoy them, but by observation and the
recording of repeated observations, he should come to
understand the significance of the calls and songs.

As to how these sounds are made, attention has already
been called (see p. 338) to the voice-organ or syrinx.
The condition of this organ varies much in birds, as
would be expected from the differing character of vocal
utterances. Dissections will make these differences
apparent.

Nesting and care of young.—Among the birds’ most
interesting instincts and habits are those domestic ones
which include mating, nest-building, and care of the
young. Birds’ eggs and birds’ nests are always attrac-
tive objects of search and collection for boys, and most
boys have a considerable personal knowledge of the
domestic habits of the commoner summer birds of their
region. With this interest and unsystematized knowledge
as a basis the teacher should be able to get from the class
much excellent field-work and personal observation. The
first thing to undertake in this study is the gathering of
data regarding the character of the mests en seailercnt
species, their situation, the time of nesting, the participa-
tion or non-participation of the male in nest-building,

BRANCH CHORDATA; CLASS AVES: THE BIRDS 367

etc.; also the number of eggs, their size and color mark-
ings, the length cf incubation, the help or lack of help of
female im brooding, etc. .In-connection with this
gathering of data in the field by note-taking, sketching,
and photographing, nests and eggs can be collected (see
directions on page 469). Let only one clutch of eggs cf
each species be taken for the common high-school collec-
tion, and if more than one nest is desired take used and
deserted nests. When the nestlings are hatched, the
bringing of food, the defence of the home, and the teach-
ing of the young to fly should all be observed and noted.

Some attempt should be made to systematize the mis-
cellaneous data obtained. Do all the members of a group
have similar nesting habits? Note the early nesting of
birds of prey; note the nests of the woodpeckers in holes
in trees; note the nesting of the various swallows. Is
there any significance in the colors and markings of eggs ?
Observe the protective coloration obvious in some (see
Chap. XXXI). Are there differences in the condition of
the newly hatched nestlings? Note the helpless altricia]
young of the robin; the independent precocial young of
the quail.

The strong influence of the mating passion will be
made plain by observations on the fighting, love-making,
singing, and general behavior of the birds in the mating
season. ihe expression of the mental and.. emotional
traits, the psychic phenomena of birds, are most empha-
sized at this time, and reveal the possession among
animals lower than man of many characteristics which are
too commonly ascribed as the exclusive attributes cf the
human species. ,

Local distribution and migration.— As explained in
Chapter XXXII, the geographical distribution of animals
is a subject of much importance, and offers good oppor-
tunities in its more local features for student field-work.

368 ELEMENTARY ZOOLOGY

The field-study of the birds of a given locality will comprise
much observation bearing directly on zoogeography or
the distribution of animals. Certain birds will be found
to be limited to certain parts of even a small region, the
swimmers will be found in ponds and streams and the
long-legged shore-birds on the pond- or stream-banks, or
in the marshes and wet meadows, although a few like the

S

Fic. 145.—Western robin, Merula migratoria propingua. (Photograph from
life by Eliz. and Jos. Grinnell.)

upland plover, curlews, and godwits are common on the
dry upland pastures. Distinguish the ground-birds from
the birds of the shrubs and hedge-rows and these again
from the strictly forest-birds. Find the special haunts of
swallows and kingfshers. Which are the shy birds
driven constantly deeper into the wild places or being
exterminated by the advance of man; which birds do not

BRANCH CHORDATA ; CLASS AVES: THE BIRDS 369

retreat but even find an advantage in man's seizure of the
land, obtaining food from his fields and gardens °

Make a map on large scale of the locality of the school,
showing on it the topographic features of the region, such
as streams, ponds, marshes, hills, woods, springs, wild
pastures, etc., also roads and paths, and such landmarks
as schoolhouses, county churches, etc. On this map in-
dicate the local distribution of the birds, as determined
by the data gradually gathered; mark favorite nesting-
places of various species, roosting-places of crows and
blackbirds, feeding-places, and bathing- and drinking-
places of certain kinds, the exact spots of finding rare
mittwesnate nests, etc:, etc. Ihe making of such a
zoogeographical map will be a source of great interest
and profit to the students.

As already mentioned, many of the birds of a locality
are ‘“‘migrants, that is, they breed farther north, but
spend the winter in more southern latitudes. These
migrants pass through the locality twice each year, going
north in the spring and south in the autumn. They are
much more likely to be observed during the spring migra -
tion than in the fall, as the flight south is usually more
hurried. The observation of the migration of birds is
very interesting, and much can be done by beginning
students. Notes should be made recording the first time
each spring a migrating species is seen, the time when it
is most abundant and the last time it is seen the same
spring. Similar records should be made showing the
imemcmetts @t the birds in ‘the fall:> A series of such
records covering a few years will show which are the
earliest species to appear, which the later, and which the
last. Such records of appearance and disappearance
should also be kept for the summer residents, those birds
goat come from the South in the spring, brééd in the
locality, and then depart for the South again in the

37° ELEMENTARY ZOOLOGY

autumn. Notes on the kinds of days, as stormy, clear,
cold, warm, etc., on which the migration seems to be
most active; on the greater prevalence of migratory flights
by day or by night; on the height from the earth at which
the migrants fly, etc., are all worth while. The Division
of Biological Survey, U. 5. Department of Agriculture,
keeps records of notes on migration sent in by voluntary
observers and furnishes blanks to be filled out by each
observer. A suggestive book about migration, and one
giving the records for many species at many points in the
Mississippi valley is Cooke's ‘: Bird Migration in the
Mississippi Valley.’’ Migration is discussed in most bird-
books.

Feeding habits, economics, and protection of birds. —
The feeding habits of birds are not only interesting, but
their determination decides the economic relation of birds ©
to man, that is, whether a particular bird species is harm-
ful or beneficial to man. Casual observation shows that
birds eat worms, grains, seeds, fruits, insects. A single

») 9)

species often is both fruit-eating and insect-eating. Do
fruits or do insects compose the chief food-supply of the
species ? To determine this more than casual observation
is necessary. Ihe birds must be watched when feeding
at different seasons. ‘The most effective way of determin-
ing the kind of food which the bird takes is to examine
the stomachs of many individuals taken at various times
and localities. Much work of this kind has been done,
especially by the investigators connected with the Division
of Biological Survey of the U. S: Departmenter 2encenl=
ture, and pamphlets giving the results of these investiga-
tions can be had from the Division. It has been distinctly
shown that a great majority of birds are chiefly beneficial
to man by eating noxious insects and the seeds of weeds.
Many birds commonly reputed to be harmful, and for that
reason shot by farmers and fruit-growers, have been

uneend ClIORII I A CLASS. AVES > THE BIRDS” ‘371

proved to do much more good than harm. Some few
birds have been proved to be, on the whole, harmful.
An investigation of the food habits of the crow, a bird of
ill-repute among farmers, based on an examination of 909
stomachs shows that about 29 per cent of the food for the

Fic, 146.—Sickle-billed thrasher, Harporhynchus redevivus. (Photograph
from life by Eliz. and Jos. Grinnell.)

year consists of grain, of which corn constitutes something
more than 21 per cent, the greatest quantity being eaten
in the three winter months. All of this must be either
waste grain picked up in fields and roads, or corn stolen
from cribs and shocks. May, the month of sprouting corn,

372 ELEMENTARY ZOOLOGY

shows a slight increase over the other spring and summer
months. On the other hand the loss of grain is offset by
the destruction of insects. These constitute more than
23 per cent of the crow’s yearly diet, and the larger part
of them are noxious.- The remainder of the crow’s food
consists of wild fruit, seeds and various animal substances
which may on the whole be considered neutral.

The slaughter of birds for millinery purposes has
become so fearful and apparent in recent years that a
strong movement for their protection has been inaugu-
rated. Rapacious egg-collecting, legislation against
birds wrongly thought to be harmful to grains and fruit,
and the selfish wholesale killing of birds by professional
and amateur hunters, help in the work of destruction.
Apart from the brutality of such slaughter, and the ex-
termination of the most beautiful and enjoyable of our
animal companions, this destruction* works strongly
against our material interests. Birde Saree saaeune!
enemies of insect pests, and the destroying of the birds
means the rapid increase and spread, and the enhanced
destructive power of the pests. It is asserted by investi-
gators that during the past fifteen years the number of our
common song-birds has been reduced to one-fourth. At
the present rate, says one author, extermination of many
species will occur during the lives of most of us. Already
the passenger-pigeon and Carolina paroquet, only a few

years ago abundant, are practically exterminated. Protect
the birds!

* One of the most unfortunate and conspicuous examples of this slaughter
is the partial extermination of the song-birds of Japan in the interests of
European milliners. To meet their demands the country people used bird-
lime throughout the woods with disastrous effectiveness, as shown in the
present exceeding scarcity of birds and the abundance of insect pests.

GiiLAURaARS XOCVA It

Peoeeit CHORDATA (Continued). CLASS MAM-
Mea A > te MAAMALS

THE MOUSE (Mus musculus)

TECHNICAL NOTE.—It is best to catch specimens alive in a good
trap. A live trap well baited and placed in some old granary
should furnish plenty for class use. White mice can often be ob-
tained at ‘‘ bird-stores.” When mice are not procurable, use rats.
A rat is perhaps preferable on account of its size, but all essential
structures can readily be made out in the mouse. Specimens
should be killed by chloroform as described for the toad, p. 5.

Structure (fig. 147).— Compare the external characters
of the mouse with those of the toad and sparrow. The
mouse, unlike the other vertebrates so far studied, is thickly
covered with /azr all over its body except on the tip of
the nose and the soles of the feet. Where are the zosfrz/ls
placed ? What are the large leaf-like expansions called
Vimencieoated just back of the eyes? Pull open the
mouth and note the large zuczsor teeth on the upper and
inven emiaws. Cut one corner of the mouth back and
observe the large flat-topped szvlar teeth on both jaws.
How does the attachment of the large fleshy Zongue differ
from the condition in the toad? The toad’s tongue is for
snapping up insects, whereas in the mouse this organ
serves to move food about in the mouth. On the tongue
are numerous small ¢aste-papille. Notice the long hairs,
ieclens, on each side of the nose. Note the similarity
between the front paws and our own hands; each has
four fingers with a small rudimentary thumb on the inner

313

374 ELEMENTARY ZOOLOGY

side of the paw. How does the hind foot of the mouse
differ from the foot of man? Posteriorly the body is
terminated by a long zaz/. At the reoteor ties is a
small aperture, the azuws, and just below, or ventral to it,
is the opening from the kidneys and reproductive organs.

TECHNICAL NOTE.—Place the mouse on its back in a dissecting-
pan and cut through the skin from anus to the lower jaw. Extend
the legs, pin down each foot and pin out the cut edges of the
skin. Now carefully cut forward through the body-wall from the
anal region and on through the breast-bones and ribs. Pin each
side out.

Near the hindmost pair of zs note a sheet of muscles,
the diaphragm, which extends across the body-cavity,
dividing it into an anterior portion, the thoracic cavity,
and a posterior, the abdominal cavity. What are the most
conspicuous organs in the thoracic cavity? Leading
anteriorly to the mouth-cavity is a long tube, the ¢rachea,
composed of a series of cartilaginous parts of rings placed
end-to-end. Note at. its anterior, end the 72 and
epiglottis. Insert a blowpipe into the glottis and inflate
the /uzgs, which will fill all the otherwise unfilled space
in the thoracic cavity. The abdominal cavity contains
the wzscera suspended in a fold of the lining membrane, as
in the other vertebrates studied. Note lying against the
diaphragm a large, red, glandular structure, the “ver.
Separate the two large lobes of the liver and expose the
opalescent ga/l-bladder. By passing a canula into this
and ligaturing, the cystic duct may be injected. Beneath
the liver is a large loop-shaped expansion of the alimen-
tary canal, the stomach. Arising from the right end of
the stomach is the narrow duodenum, which gradually
merges into the very much convoluted small intestine, or
zleum, which is followed by the large intestine, or colon,
the last part of which is a straight tube, the rectum. The
small intestine occupies most of the space in the peri-

BRANCH CHORDATA; CLASS MAMMALIA Sie)

toneal cavity. Within the loop of the pylorus will be
found an irregular pinkish mass of tissue, the pancreas.
Beneath the stomach on the left side of the body lesa
very dark glandular mass not much unlike the liver but
altogether detached from it. This structure is the sp/een,
a ductless gland.

Note dorsally of the trachea a long gabe passing through
the diaphragm and connecting the mouth with the
stomach. Whatis thistube? Note the Eustachian tubes
extending from the mouth to the ears. [he median part
of the roof of the mouth is the palate, hard in front, soft
behind. A pair of small bodies at the sides of the soft
palate near its hinder end are the fonsz/s. At the pos-
terior angle of the lower jaw are glandular bodies, the szd-
maxillary glands, which lead by a short duct anteriorly
to open on the floor of the mouth. On the sides of the
neck just below the ears are pink or yellowish bodies, the
parotid glands, opening anteriorly in the sides of the
mouth-cavity. These two sets of glands are collectively
known as the sa/ivary glands, the function of which is to
secrete the saliva. Push apart the sub-maxillary glands
and note below them overlying the trachea on either side
two dark-red lobes connected by a band of tissue. These
constitute the ‘hyro7d glazd, another of the so-called
ductless glands. Within the thoracic cavity anterior to
the heart note a mass of pinkish tissue, the thymus e¢land.
Observe the large masseter muscles, which cover the Jaws.
What is their function? On either side of the neck les a
large blood-vessel, the external jugular vein, which col-
lects blood from the head and carries it down to the heart.
Note the large pectoral muscles which cover the breast and
extend out into the arms, and which are so strong and
highly developed in the sparrow. ‘The head is supported
by large muscles which run down the back of the neck
to the ribs. Others are attached to the ribs, which they

376 ELEMENTARY ZOOLOGY

raise and lower. These movements, together with the
contraction of the diaphragm, cause the expansion and
contraction of the thoracic cavity
whereby the lungs are regularly filled
and emptied. Note that the abdomen
is covered by a double layer of mus-
cular tissue, the outer part made up

of the external oblique muscles, the
inner by the zxzternal oblique muscles.
Examine the heart. How many

yyyyptl Le

5
Ye 7

auricles has it? Pine yyag77 aes ia
the mouse, as in the bird, are entirely
separated, forming two complete
compartments, a vzght and a /eft
ventricle. The blood flowing from
the veins of the body is collected in
the right auricle, thence it passes into
= the right ventricle, whence it is con-
Fic. 148.—Diagram of veyed tothe lungs; returning it flows

ne ee through the left auricle into the left

auricles; 7, lung; 4, ventricle, whence it is forced through

iver, 2. por’ von the arteries of tue bady. 3. or .a

bringing blood from the
intestine; v, ventricles; study of the circulatory system in

ee ok Bees mammals (fig. 148), a rat or a rabbit

the shaded vessels should be injected by the teacher and

carry venous blood, the

others arterial blood. an advanced text-poole, acme anker s

om dangsley-) ‘*Zootomy ’’ or Marshall and Hurst’s
‘Practical Zoology,;*. used as.a guide. “2 siteeppesheant
‘is very good to cut open for a class demonstration.

Make a drawing of the organs observed thus far in the
dissection.

The szdncys in the mouse are situated in the dorsal
region next to the backbone. They consist of two bean-
shaped smooth glands. From them a pair of ducts, the

ureters, can be traced dewn to a median thin-walled

BRANCH CHORDATA: CLASS MAMMALIA 377

muscular sac, the d/adder. The bladder opens to the
exterior of the body by means of a short tube, the
urethra. Cut open a kidney longitudinally and examine
the cut surfaces.

The two egg-glands of the female mouse lie in the
median portion of the abdominal cavity, somewhat below
the kidneys, and from the vicinity of each runs an egg-
tube. These tubes meet below the bladder, and open to
the exterior of the body through the aperture noted below
the anus. Inthe posterior parts of these tubes lie until
birth the developing embryos.

TECHNICAL NOTE.—-For a study of the nervous system place the
specimen ventral side down and cut through the skull with the bone-
cutters or heavy scissors, exposing the brain and spinal cord.

Note the large drazz (fig. 149), composed of small cffic
lobes, large cerebrum, cerebellum, and medulla oblongata,
followed by the long spznal cord. Note the nerves aris-
ing from the brain and spinal cord.

For a careful dissection of the mammalian nervous
system a larger mammal, such as a cat or dog or rabbit,
should be used. For guide use a text-book such as, for
the dog, Howell’s ‘: Dissection of the Dog ’’; for the cat,

Reighard and Jennings’ ‘‘ Anatomy of the Cat ’’; and for
the rabbit, Parker’s ‘‘ Zootomy ’’ or Marshall and Hurst's
Sunfish Toad Snake Sparrow Mouse

Fic. 149. —Diagram of brains of vertebrates: O/f. Z., olfactory lobes: Cér.,
cerebrum ; A/d. Br., midbrain (optic lobes) ; CéZ., cerebellum; Jed.
O6., medulla oblongata; Sf. Cd., spinal cord. (From specimens. )

378 ELEMENTARY ZOOLOGY

‘“Practical Zoology.’’ Make a good preparation of the
brain and preserve it for future use in some fluid like
Fischer’s fluid (see page 453).

TECHNICAL NOTE.—Prepare a well-cleaned skeleton by boiling a
specimen in a soap solution and thoroughly cleansing it (See p. 452).

Note the very compact skeleton of the mouse. Note
the closely sutured skull. How many cervical or neck
vertebre are there? ‘The rzds are attached to the thoracic
vertebrae. How many pairs of ribs? The bony thorax
supports the shoulder-girdle and bones of the fore legs.
The thorax is followed by a series of ribless vertebre, the
lumbar vertebre, which in the posterior region of the body
fuse with the pelvic girdle supporting the hind limbs.
Fhe body vertebra are succeeded bythe wer. aimeli
smaller caudal vertebre. Compare the skeleton of the
mouse with that of the bird; also with that of the toad.
For directions for a detailed study of the skeleton see in
Palen, ss “Zootomy. . aneve=
count or tie skeletom of the
rabiit, pp: 262-280.

TECHNICAL NOTE. — For the
study of the eye (fig. 150)" the (7
teacher should obtain the eye of [A
some large mammal, as the ox or [+
sheep, with which to make a class
demonstration. The eye: ot a
rap DItLOL Cam can On EOUTSesmie
used. Foranaccount ofthe verte-
brate eye see Parker and Haswell’s
“ Text-book of Zoology,” Vol. II.
pp. 103-107. For a study of the
ear use, a, bird o~ mammal and
see pp. 107-110 of the same book. Fy¢, 150.—Diagram of vertebrate

eye:.¢, chorotd= 2 anisse7 lems--77,

Life-history and habits. optic nerve; 7, retina; s, sclerotic.
(From Kingsley.)

s

Z

A
£
‘
3°” ae ‘7
nL. <a ns
W ne

=F
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=
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— The house-mouse is nota
native of North America, but was introduced into this
country from Europe, to which, in turn, it came from Asia,

BRANCH CHORDATA: CLASS MAMMALIA 379

its original habitat. The mouse came to this country in
the vessels of early explorers. Similarly the brown and
black rats, new so abundant all over North America, and
members of the same genus as the mouse, were intro-
duced from Europe. Accompanying man in his travels
the mouse has spread from Asia until it is now to be
found over the whole world.

The habits of mice are well known; their fondness for
living in our homes and outbuildings makes them familiar
acquaintaices. Their food is varied; they seem to thrive
best, however, on a vegetable diet. Grains and nuts are
favorite foods. The house-cat is their greatest enemy,
but man takes advantage of their instinct to go into holes
by constructing traps with funnel or tunnel entrances
which, baited with cheese or other favorite food, are
fatally attractive. In climbing, mice are aided by the
tail. Their strong hind legs enable them to stand erect,
and even to take several steps in this posture. They can
swim readily, although naturally they rarely take to
water. Their special senses are keen, the senses of hear-
ing and taste being unusually well developed. Their
‘“singing,’’ which has been the subject of much discussion,
seems to be actually a voluntary and normal performance
which, however, hardly deserves to be called singing, but
rather a slightly varied peeping or whistling.

The mouse is a prolific mammal, producing from four
to six times a vear broods of from four to eight young.
The mouse makes a cosy nest of straw, bits of paper,
feathers, wool or other soft materials, and in this the
young are born. The newly born mice are very small
and are blind and helpless. They are odd little creatures,
being naked and almost transparent. They grow rapidly,
being covered with hair in a week, although not opening
their eyes for about two weeks. A day or two after their
eyes are open they begin to leave the nest, and hunt for
feod for themselves.

g°° ELEMENTARY ZOOLOGY

OTHER MAMMALS

The mammals constitute the highest group of animals,
including man, the monkeys and apes, the quadrupeds,
the bird-like bats and fish-like seals and whales; in all
about 2500 species. They are found everywhere except
on a few small South Sea islands. Only a few species,
however, have a world-wide distribution. The name
Mammalia is derived from the mammary or milk glands
with which the females are provided and by the secretion
of which the young of this class, born free in all but a
few of the lowest forms, are nourished for some time after
birth. In size mammals range from the tiny pigmy-shrew >
and harvest mouse, which can climb a stem of wheat, to
the great sulphur-bottom whale of the Pacific Ocean, which
attains a length of a hundred feet and a weight of many
tons. Mammals differ from fishes and batrachians and
agree with reptiles and birds in never having external
cills; they differ from reptiles and agree with birds in being
warm-blooded and in having a heart with two distinct
ventricles and a complete double circulation; finally, they
differ from both reptiles and birds in having the skin more
or less clothed with hair, the lungs freely suspended in a
thoracic cavity separated from the abdominal by a mus-
cular partition, the diaphragm, and in the possession by
the females of mammary glands. In economic uses to
man mammals are the most important of all animals.
They furnish the greater portion of the animal food of many
-buman races, likewise a large amount of their clothing.
Horses, asses,. oxen, camels, reindeer, elephants. and
llamas are beasts of burden and draught; swine, sheep,
cattle, and goats furnish flesh, and the two latter milk for
food; the wool of sheep, the furs of the carnivores, and
the leather of cattle, horses, and others are used for cloth-
ing, while the bones and horns of various mammals serve
various purposes.

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BRANCH CHORDATA: CLASS MAMMALIA 381

Body form and structure.—The mammalian body
varies greatly. Its variety of form and general organiza-
tion is explained by the facts that, although most of the
species live on the surface of the earth, some are burrowers
in the ground, some flyers in the air, and some swimmers
in the water. Mammals never have more than two pairs
of limbs; in most cases both pairs are well developed and
adapted for terrestrial progression. In the aerial bats the
fore limbs are modified into organs of flight; among the
aquatic seals, sea-lions, walruses, and whales both sets are
modified to be swimming flippers or paddles. In many
of these aquatic forms the hind limbs are greatly reduced
or even completely wanting.

Most mammals are externally clothed with hair, which
is a peculiarly modified epidermal process. [Each hair,
usually cylindrical, is composed of two parts, a central pith
containing air, and an outer more solid cortex; each hair
rises from a short papilla sunk at the bottom of a follicle
lying in the true skin. In some mammals the hairs
assume the form of spines or ‘‘ quills,’’ asin the porcupine.
The hairy coat is virtually wanting in whales and is very
sparse in certain other forms, the elephant, for exaimple,
which has its skin greatly thickened. The claws of beasts
of prey, the hooves of the hoofed mammals, and the outer
horny sheaths of the hollow-horned ruminants are all
epidermal structures.

The bones of mammals are firmer than those of other
vertebrates, containing a larger proportion of salts of lime.
Among the different forms the spinal column varies largely
in the number of vertebre, this variation being chiefly
due to differences in length of tail. Apart from the —
caudal vertebre their usual number is about thirty. The
mammalian skull is very firm and rigid, all the bones
composing it, excepting the lower jaw, the tiny auditory
ossicles, and the slender bones of the hyoid arch, being

382 ELEMENTARY ZOOLOGY

immovably articulated together. The correspondence
between the bones of the two sets of limbs is very ap-
parent. The number of digits varies in different mammals,
and also in the fore and hind limbs of a single species.
Among the Ungulates the reduction in the number of
digits is especially noticeable; the forefoot of a pig has
four digits, that of the cow two, and that of the horse one.
The two short ‘‘splint’’ bones in the horse are remnants
of lost digits. The teeth are important structures in
mammals, being used not only for tearing and masticat-
ing food, but as weapons of offence and defence. <A tooth
consists of an inner soft pulp (in old teeth the pulp may
become converted into bone-like material) surrounded by
hard white dentine or ivory, which is covered by a thin
layer of enamel, the hardest tissue known in the animal
body. A hard cement sometimes: covers as a thin layer
the outer surface of the root, “and may alse stem the
enamel of the crown. The teeth im mest formssare of
three groups: (a) the incisors, with sharp cutting edges
and simple roots, situated in the centre of the jaw; (d) the
canines, often conical and sharp-pointed, next to the
incisors; (c) next the molars, broad and flat-topped for
grinding, and divided into premolars and true molars.
There is great variety in the character and arrangement
of these structures in mammals, their variations being
much:used in classification. The number and arrange-
ment of the teeth is expressed by a dental formula, as, for
example, in the case of man

2 2 a ee ee

Z ee LOS ite eee UL =a
Deo a. ae 3-- 3 3

The mouth is bounded by fleshy lips. On the floor of
the mouth is the tongue, which bears the taste-buds or
papilla, the organs of taste. The cesophagus is always
a simple straight tube, but the stomach. varies greatly,

BRANCH CHORDATA: CLASS MAMMALIA 383

Fic. 151.—A group of Rocky Mountain sheep, or ‘‘big horns,’’ Ovzs cana-
densts, including males, females and young. (Photograph by E. Willis
from specimens mounted by Prof. L. L. Dyche, University of Kansas.)

384 ELEMENTARY ZOOLOGY

being usually simple, but sometimes, as in the ruminants
and whales, divided into several distinct chambers. The
intestine in vegetarian mammals is very long, being ina
cow twenty times the length of the body. In the carni-
vores it is comparatively short—in a tiger, for example,
but two or three times the length of the body.

The blood of mammals is warm, having a temperature
of from 35° ©. to 40° €. (95° PF. to ea. eee red
in color, owing to the reddish-yellow, circular, non-
nucleated blood-corpuscles. The circulation is double,
the heart being composed of two distinct auricles and two
distinct ventricles. Air is taken in through the nostrils
or mouth and carried through the windpipe (trachea) and
a pair of bronchi to the lungs, where it gives up its oxygen
to the blood, from which it takes up carbonic-acid gas in
turn. At the upper end of the trachea 1s the ldarynx or
voice-box, consisting of several cartilages attaching by
one end to the vocal cords and by the other to muscles.
By the alteration of the relative position of these cartilages
the cords can be tightened or relaxed, brought together
or moved apart, as required to modulate the tone and
volume of the voice.

The kidneys of mammals are more compact and definite
in form than those of other vertebrates. In all mammals
except the Monotremes they discharge their product
through the paired ureters into a bladder, whence the
urine passes from the body by a single median vrethra.
Mammary glands, secreting the milk by which the young
are nourished during the first period of @em-ceesrence
after birth,. are present in both sexes in all mammals,
though usually functional in the female only.

The nervous system and the organs of special sense
reach their ‘highest development in the mammei-, in
them the brain is distinguished by its large size, and by
the special preponderance of the forebrain or cerebral

CLASS MAMMALIA

.
.

BRANCH CHORDATA

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386 | ELEMENTARY ZOOLOGY |

hemispheres over the mid- and hind-brain. Man’s brain
is many times larger than that of all other known mam-
mals of equal bulk of body, and three times as large as
that of the largest-brained ape. In man and the higher
mammals the surface of the forebrain is thrown into many
convolutions; among the lowest the surface is smooth.
Of the organs of special sense, those of touch consist of
free nerve-endings or minute tactile corpuscles in the skin.
The tactile sense is especially acute in certain regions, as
the lips and end of the snout in animals like hogs, the
fingers in man, and the under surface of the tail in certain
monkeys. All the other sense-organs are situated on the
head. The organs of taste are certain so-called taste-
buds located in the mucous membrane covering certain |
papille.on: the surface of the toneue: “(me aon. of
smell, absent only in certain whales, consists of a ramifi-
cation of the olfactory nerves over a moist mucous mem-
brane in the nose. The ears of mammals are more highly
developed than those of other vertebrates both in respect
to the greater complexity of the inner part and the size
of the outer-part... A large outer ear for collectine the
sound-waves is present in all but a few mammals. A
tympanic membrane separates it from the middle ear in
which is a chain of three tiny bones leading from the
tympanum to the inner ear, composed of the three semi-
circular canals and the spiral cochlea. The eyes (fig. 150)
have the structure characteristic of the vertebrate eye, con-
sisting of a movable eyeball composed of parts through
_which the rays of light are admitted, regulated, and con-
centrated upon the sensitive expansion, retina, of the optic
nerve lining the posterior part of the ball. The eye is pro-
tected by two movable lids. In almost all mammals below
the Primates there is a third lid, the nictitating membrane.
In some burrowing rodents and others the eye is quite
vestigial and even concealed beneath the skin.

BRANCH CHORDATA: CLASS MAMMALIA 387

Development and life-history.—All mammals except
the Monotremes give birth to free young. The two
genera of Monotremes produce their young from eggs
hatched outside the body; Zachyglossus lays one egg
which it carries in an external pouch, while Oruzthorhyn-
chus deposits two eggs in its burrow. The embryo of
other mammals develops in the lower portion of the egg-
lube, to the walls of which it is intimately connected by
a membrane called the placenta. (In the kangaroos and
opossums, Marsupialia, there is no placenta.) Through
this placenta blood-vessels extend from the body of the
mother to the embryo, the young developing mammal
thus deriving its nourishment directly from the parent.

They duration of cestation (embryonic or prenatal
development in the mother’s body) varies from three
weeks with the mouse, eight weeks with-the cat, nine
months with the stag, to twenty months with the elephant.
Like the birds, the young of some mammals, the carni-
vores for example, are helpless at birth, while those of
others, as the hoofed mammals, are very soon able to run
about. But all are nourished for a longer or shorter time
by the milk secreted by the mammary gland of the
mother.

Habits, instinct, and reason.
examples of instinct and intelligence shown by many

Despite the wonderful

insects and by the other vertebrates, especially the birds,
it is among mammals that we find the highest develop-
ment of these qualities and of reason. In the wary and
patient hunting for prey by the carnivora, in the gregarious
and altruistic habits of the herding hoofed mammals, in
the highly developed and affectionate care of the young
shown by most mammals, and in the loyal friendship and
self-sacrifice of dogs and horses in their relations to man,
we see the culmination among animals of the development
of the functions of the nervous system. Jn the character-

383 ELEMENTARY, ZOCEOCGY

istics of intelligence and reason man of.course stands
immensely superior to all other animals, but both intelli-
gence .and reason are too often shown by many of the
other mammals not to make us aware that man’s mental
powers differ only in degree, not in kind, from those of
other animals. :

Pure instinct is hereditary, and purely instinctive actions
are common to all the individuals of a species. Those
actions which the individual could not learn by teaching,
imitation, or experience are instinetive 7) ine eecurace
pecking at food by chicks just hatched from an incubator
is purely instinctive. Purely instinctive also is the laying
of eggs by a butterfly on a certain species of plant which
may have to be sought for over wide acres, so that the
caterpillars when hatched shall find themselves on their
own special food-plant. Yet the butterfly never ate of
this plant and will never see its young. Such elaborate
instincts as these have been developed from the simplest
manifestations of sensation and nervous function, Just as
the complex structures of the body have been developed
from simple structures (see Chapter X XIX).

The feeding and domestic habits and the whole general
behavior of animals are extremely interesting subjects of
observation and study. And such observation intelli-
gently pursued will be of much value. The point to be
kept ever in mind is that all animal habits are connected
with certain conditions of life; that in every case there is
an answer to the question ‘‘why.’’ This answer may
not be found; in many cases it is extremely difficult to
get at, but often it is simple and obvious amd can be
found by the veriest beginner.

Classification. — The mammals of North America repre-
sent eight orders. “Vhree additional mammalaa orders
namely, the Monotremata, including the extraordinary
duck-bills (Ornzthorhynchus) and a species of Tachyglossus

BRANCH CHORDATA: CLASS MAMMALIA 389

in Australia and Tasmania; the Edentata, including the
sloths, armadillos, and ant-eaters found in tropical regions;
and the Sirenia, including the marine manatees and
dugongs, are not represented (except by a single man-
atee) in North America. In the following paragraphs
some of the more familiar mammals representing each of
the eight orders represented in North America are
referred to.

The opossums (Marsupialia).—The opossum (Dzde/-
phys virginiana) is the only North American representa-
tive of the order Marsupialia, the other members of which
are limited exclusively to Australia and certain neighbor-
ing islands. The kangaroos are the best known of
the foreign marsupials. After birth the young are trans-
ferred to an external pouch, the marsupium, on the
ventral surface of the mother, in which they are carried
about and fed. The opossum lives in trees, is about the
size of a common cat, and has a dirty-yellowish woolly
fur. _ Its tail is long and scaly, like a rat’s. Its food
consists chiefly of insects, although small reptiles, birds,
and bira’s eggs are eaten. When ready to bear young
the opossum makes a nest of dried grass in the hollow of
a tree, and produces about thirteen very small (half an
inch long) helpless creatures. These are then placed by
the mother in her pouch. Here they remain until two
months or more after birth. Probably all the North
American opossums found from New York to California
and especially common in the Southern States belong to
a single species, but there is much variety among the
individuals.

The rodents or gnawers (Glires).— The rabbits, porcu-
pines, gophers, chipmunks, beavers, squirrels, and rats
and mice compose the largest order among the mammals.
They are called the rodents or gnawers (Glires) because
of their well-known gnawing powers and _proclivities.

390 ELEMENTARY ZOOLOGY

The special arrangement and character voi tie ees are
characteristic of this order: - There? are: mesgami@es a
toothless space being left between the incisors and molars
on-each side. There are only two incisor tectivanm each
jaw (rarely four in the upper jaw), and these teeth grow
continuously and are kept sharp and of uniform length by
the gnawing on hard substances and the constant rubbing
on. each other. The food of rodents 1s chieiyevegers ile:

Of the hares and rabbits the cottontail (Lepus nuttal/: )
and the common jack-rabbit (L. campestris) are the best
known. The cottontail is found all over the United
States, but shows some variation in the different regions.
There are several species of jack-rabbits, all limited to the
plains and mountain regions west of the Mississippi River.
The food of rabbits is strictly vegetable, consisting of suc-
culent roots; branches, or leaves: Rabbitt. wry
prolific and yearly rear from three to six broods of from
three to six young each. There are two North American
species of porcupines, an Eastern one, Arethizon dorsatus,
and a Western one, &. epixanthus. The quills in both
these species are short, being only an inch or two in
length, and are barbed. In some foreign porcupines they
are a foot long. They are loosely attached im the skin
and may be readily pulled out, but they cannot be shot
out by the porcupine, as is. popularly told) Tie little
cuinea-pigs (Cavia), kept as pets, are South American —
animals related to the porcupines.

The pocket gophers, of which there are several species
mostly inhabiting the central plains, are rodents found
only in -North America. They all live undereround,
making extensive galleries and feeding chiefly on bulbous
roots. The mice and rats constitute a laree sammy, o1
which the house-mice and rats, the various field-mice, the
wood-rat (Veotoma pennsylvanica) and the muskrat (472ber
ztbethicus) are familiar representatives. The common

BRANCH CHORDATA: CLASS MAMMALIA oo2

brown rat (Mus decumanus) was introduced into this
country from Europe about 1775, and has now nearly
wholly supplanted the black rat (JZ. rattus), also a
European species, introduced about 1544. The beaver
(Castor canadensis) is the largest rodent. It seems to be
doomed to extermination through the relentless hunting
of it for its fur. The woodchuck or ground-hog (dArctomys
monax) is another familiar rodent larger than most mem-
bers of the order. The chipmunks and ground-squirrrels
are commonly known rodents found all over the country.
They are the terrestrial members of the squirrel family,
the best known arboreal members of which are the red
squirrel (Sczurus hudsonicus), the fox-squirrrel (S. ludo-
victanus), and the gray or black squirrel (S. carolinensis).
The little flying squirrel (Sczuropterus volans) is abundant
in the Eastern States.

The shrews and moles (Insectivora).—The shrews
and moles are all small carnivorous animals, which,
because oftheir size, confine their attacks chiefly to insects.
The shrews are small and mouse-like; certain kinds of
them lead a semi-aquatic life. There are nearly a score
of species in North America. Of the moles, of which there
are but few species, the common mole (Scalops aquaticus)
is well known, while the star-nosed mole (Condylura
cristata) is recognizable by the peculiar rosette of about
twenty cartilaginous rays at the tip of its snout. Moles
live underground and have the fore feet wide and shovel-
like for digging. The pores Beene are members
Sis order ...-

The bats (Chiroptera). —The bats (fig. 153), order Chi-
roptera, differ from all other mammals in having the fore
‘limbs modified for flight by the elongation of the forearms
and especially of four of the fingers, all of which are con-
nected by a thin leathery membrane which includes also
the hind feet and usually the tail. Bats are chiefly noc-

392 ELEMENTARY ZOOLOGY

turnal, hanging head downward by their hind claws in
caves, hollow trees, or dark rooms through the day. They
feed chiefly on insects, although some foreign kinds live
on fruits. There are a dozen or more species of bats in
North America, the most abundant kinds in the Eastern
States being the little brown bat (JZyotzs subulatus), about
three inches long with small fox-like face, high slender
ears, and a uniform dull olive-brown color, and the red
bat (Laszurus borealis), nearly four inches long, covered

Fic. 153.—The hoary bat, Lasiurus cinereus. (Photograph from life
by2J.-O- Snyder.)

with long, silky, reddish-brown fur, mostly white at tips
of the hairs.

The dolphins, porpoises, and whales (Cete).—The
dolphins, porpoises, and whales (Cete) compose an order
of more or less fish-like aquatic mammals, among which

BRANCH CHORDATA: CLASS MAMMALIA 393

are the largest of living animals. In all the posterior limbs.
are wanting, and the fore limbs are developed as broad
flattened paddles without distinct fingers or nails. The
tail ends in a broad horizontal fin or paddle. The Cete
are all predaceous, fish, pelagic crustaceans, and especially
squids and cuttlefishes forming their principal food. Most
of the species are gregarious, the individuals swimming
together in ‘‘schools.’’ The dolphins and porpoises
compose a family (Delphinide) including the smaller
and many of the most active and voracious of the Cete.
The whales compose two families, the sperm-whales
(Physeterida) with numerous teeth (in the lower jaw
only) and the whalebone whales (Balenide) without
teeth, their place being taken in the upper jaw by an array
of parallel plates with fringed edges known as ‘‘ whale-
bone.’’ The great sperm-whales or cachalots (Physeter
macrocephalus) found in southern oceans reach a length
(males) of eighty feet, of which the head forms nearly
one-third. Of the whalebone whales, the sulphur-bottom
(Balenoptera sulfurea) of the Pacific Ocean, reaching a
length of nearly one hundred feet, is the largest, and hence
the largest of all living animals. The common large
whale of the Eastern coast and North Atiantic is the right
whale (Salena glactalis); a near relative is the great
bowhead (8. mysticetus) of the Arctic seas, the most
valuable of all whales to man. Whales are hunted for
their whalebone and the oil yielded by their fat or blubber.
The story of whale-fishing is an extremely interesting
one, the great size and strength of the ‘‘game’’ making
the ‘‘fishing ’’ a hazardous business.

The hoofed mammals (Ungulata).—The order Ungu-
lata includes some of the most familiar mammal forms.
Most of the domestic animals, as the horse, cow, hog,
sheep, and goat, belong to this order, as well as the
familiar deer, antelope, and buffalo of our own land and

394 ELEMENTARY ZOOLOGY

the elephant, rhinoceros, hippopotamus, giraffe, camel,
zebra, etc., familiar in zoological gardens and menageries.
The order is a large one, its members being characterized
by the presence of from one to four hooves, which are the
enlarged and thickened claws of the toes. The Ungulates
are all herbivorous, and have their molar teeth fitted for

ax

Fic. 154.--Male elk or wapiti, Cervus canadensis. (Photograph by E.
Wiilis from specimen mounted by Prof. L. L. Dyche, University of

Kansas. )

srinding, the canines being absent or small. The order
is divided into the Perissodactyla or odd-toed forms, like
the horse, zebra, tapir, and rhinocerus, and the Artio-
dactyla or even-toed forms, like the oxen, sheep, deer,

BRANCH CHORDATA: CLASS MAMMALIA 395

camels, pigs, and hippopotami. The Artiodactyls com-
prise two groups, the RKuminants and Non-ruminants.
All of the native Ungulata of our Northern States belong
to the Ruminants, so called because of their habit of

chewing a cud. A ruminant first presses its food into a
ball, swallows it into a particular one of the divisions of
its four-chambered stomach, and later regurgitates it into

)

(Photograph by

-rof. L. L. Dyche, University of Kansas.)

Willis from specimens mounted by |

155. — Antelope, male, female, and young, Antilocapra americana.
4

Fic.

396 ELEMENTARY ZOOLOGY

the mouth, thoroughly masticates it, and swallows it
again, but into another stomach-chamber. From this it
passes through the other two into the intestine.

The deer family (Cervidz) comprises the familiar Vir-
ginia or red deer (Odocetlcus americanus) of the Eastern
and Central States and the white-tailed, black-tailed, and
mule deers of the West, the great-antlered ell or wapiti
(Cervus canadensis) (fig. 154), the great moose {(A/cz
americana) (fig. 152), largest of the deer family, and the
American reindeer or caribou (Rangifer caribou). All
species of the Cervide have solid horns, more or less
branched, which are shed annually. Only the males (ex-
cept with the reindeer) have horns. The antelope (Az/-
locapra americana) (fig. 155) common on the Western
plains also sheds its horns, which, however, are not solid
and do not break off at the base as in the deer, but are
composed of an inner bony core and an outer horny
sheath, the outer sheath only beine Shed Pacey
Bovide includes the once abundant buffalo or bison (Lzson
bison) (frontispiece), the big-horn or Rocky Mountain
sheep (Ovzs canadensis) (fig. 151), and the strange pure-
white Rocky Mountain goat (Oreamnos montanus). The
buffalo was once abundant on the Western plains, travelling
in enormous herds. But so relentlessly has this fine animal
been hunted for its skin and flesh that it is now practically
exterminated (fig. 156). A small herd is still to be found
in Yellowstone Park, and a few individuals live in parks
and zoological gardens. In all of the Bovide the horns
are simple, hollow,. and permanent, each enclesmia a
bony core.

The carnivorous mammals (Fere).—The order Fere
includes all those mammals usually called the carnivora,
such as the lions, tigers, cats, wolves, dogs, Bears,
panthers, foxes, weasels, seals, etc. All of them feed
chiefly on animal substance and are predatory, pursuing

BRANCH CHORDATA: CLASS MAMMALIA 397

and killing their prey. They are mostly fur-covered and
many are hunted for their skin. They have never less
than four toes, which are provided with strong claws that
are frequently more or less retractile. The canine teeth
are usually large, curved, and pointed.

While most of the Ferz live on land, some are strictly
aquatic. he true seals, fur-seals, sea-lions, and walruses
comprise the aquatic forms, all being inhabitants of the
ocean. The true seals, of which the common harbor seal
(Phoca vitulina) is our most familiar representative, have

Fic. 156.—A buffalo, Bison bzson, killed for its skin and tongue, on the
plains of Western Kansas thirty years ago. (Photograph by J. Lee
Knight.) 3

the limbs so thoroughly modified for swimming that they

are useless on land. The fur-seals, sea-lions, and walruses

use the hind legs to scramble about on the rocks or

398 ELEMENTARY ZOOLOGY

beaches of the shore. ‘The fur-seals (fig. 157) live gre-
gariously in great rookeries on the Pribilof or Fur Seal
Islands, and the Commander Islands in Bering Sea.

The bears are represented in our country by the wide-
spread brown, black, or cinnamon bear (Ursus americanus)
and the huge grizzly bear (U. horribilts) of the West. The
great polar bear (7halarctos maritimus) lives in arctic
regions. The otters, skunks, badgers, wolverines, sables,
minks, and weasels compose the family Mustelide, which
includes most of the valuable fur-bearing animals. Some
of the members of this family lead a semi-aquatic or even
strictly aquatic life and have webbed feet. The wolves,
foxes, and dogs belong to the family Canidze. The coyote
(Cants latrans), the gray wolf (C. nudzlus), and the red
fox (Vulpes pennsylvanicus) are the most familiar repre-
sentatives of this family, 1n addition to the dog (C. fam-
liarvis), whichis closely allied “te> the Welk lose
carnivorous of the carnivora, formed to devour, with every
offensive weapon specialized to its utmost, the Felidae,
whether large or small, are, relatively to tem cize* tlie
fiercest, strongest, and most terrible som peace. = | he
Felidz or cat family includes: the Nens,:tieessesmaycnas,
leopards, jaguars, panthers, wildcats, and lynxes. In this
country the most formidable of the Felidz is the American
panther. or puma (Fels concolor). W teaches=a leneth
from nose to root of tail of over four feet 2 ies tail is
long. The wildcat (Lyn+ rufus) is much smaller and
has a short tail.

. The man-like mammals (Primates).—The Primates,
the highest order of mammals, includes the lemurs,
monkeys, baboons, apes, and men. Man (/Jomo sapiens)
is the only native representative of this order in our
country. All the races and kinds of men known, although
really showing much variety in appearance and body
structure, are commonly included in one species. The

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BRANCH CHORDATA

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400 ELEMENTARY ZOOLOGY

chief structural characteristics which distinguish man from
the other members of this order are the great development
of his brain and the non-opposability cf his great toe.
Despite the similarity in general structure between him

Fic. 158.—‘‘ Bob Jordan,” a monkey of the genus Cercopithecus.
(Photograph from life by D. 5S. Jordan.)
and the anthropoid apes of the Old World, in particular

the chimpanzee and orang-outang, the disparity in size of
brain 1s enormous.

The lowest Primates are the lemurs found in Madagas-
car, in which island they include about one-half of all
the mammalian species found there. The brain is much

BRANCH CHORDATA: CLASS MAMMALIA 401

less developed in the lemurs than in any of the other
monkeys. The monkeys and apes may be divided into
two groups, the lower, platyrrhine monkeys, found in the
New World, and the higher, catarrhine forms, limited to
the Old World. The platyrrhine monkeys have wide noses
in which the nostrils are separated by a broad septum and
with the openings directed laterally. These monkeys are
mostly smaller and weaker than the Old: World forms and
are always long-tailed, the tail being frequently prehen-
sile. They include the howling, squirrel, spider, and
capuchin monkeys common in the forests of tropical South
America. The catarrhine monkeys have the nose-septum
narrow and the openings of the nostrils directed forwards,
and the tail is wanting in numerous members of the group.
They include the baboons, gorillas, orang-outangs, and
chimpanzees. These apes have a dentition approaching
that of man, and in all ways are the animals which most
nearly resemble man in physical character.

PART Ill
ANIMAL ECOLOGY

CHA PALER! SOX

fee st VGGLE FOR EXISTENCE, ADAPTA-
TION, AND SPECIES-FORMING

TECHNICAL NOTE.— Multiplication, or increase by geometric
_ratio, among animals can be illustrated by noting the many eggs
laid by a single female moth or beetle or fly or mosquito or any
other common insect (or almost any other non-mammalian animal).
The production of many live young by each female rose aphid can
be readily seen; the number of young in a litter of kittens or pups
or rabbits is a good illustration. From this geometric increase it is
obvious that there must be a great crowding of animals and a strug-
gle among them for existence. This struggle and the downfall of
the many and success of the victorious few can be observed by
rearing in a small jar of water all the young of a single brood of
water-tigers (larva of Dyficus) or other aquatic predaceous insect.
The strongest young will live by killing and eating the weaker of
their own kind. Ina spider’s egg-sac the young after hatching do
not immediately leave the sac, but remain in it for several days.
During this time they live on each other, the strongest feeding on
the weaker. Thus out of many spiderlings hatched in each sac com-
paratively few issue. This can be readily observed. Open several
egg-sacs and count the eggs in them. Let the spiderlings hatch
and tssue from some other egg-sacs belonging to the same species
ofspider. The number of issuing spiderlings will always be much
less than that of the eggs. The actual working of natural selection
and the forming of new species can of course be seen only in re-
sults, and not in process. The great variety of adaptation, the fit-
ness of adaptive structures, can be readily illustrated among the
commonest animals. Animals showing certain striking and unusual
adaptations will perhaps make the matter more obvious. To all
teachers will occur numerous opportunities of illustrating, by refer-

403

404 | ELEMENT ARY -ZOCLOGR4

ence to actual processes or to obvious resale the pigs of this
chapter.

The multiplication and crowding of animals.—In the
reproduction or multiplication of animals the production
of young proceeds in geometric ratio, that is, it is truly a
multiplication. Any species of animal, if its multiplica-
tion proceeded unchecked, would soomer or-iater be
sufficiently numerous to populate exclusively the whole
world. The elephant is reckoned the slowest breeder of
all known animals. It begins breeding when thirty years
old and goes on breeding until ninety years old, bringing
forth six young in the interval, and surviving until-a
hundred years old. Thus after about eight hundred years
there would be, if all the individuals lived to their normal
age limit, 19,000,000 elephants alive descended from the
first pair. A few years more of unchecked multiplication
of the elephant and every foot of land on the earth would
be covered by them. But the rate of multiplieamed of
other animals varies from a little to very much greater
than that of the elephant.. It has been Shown tar aetuc
normal rate in increase in English sparrows, if none were
to die save of old age, it would take but twenty years to
give one sparrow to every square inch in the State of
Indiana. The rate of increase of an animal, each pair
producing ten pairs annually and each animal living ten
years, is shown in the following table:

gy Cars: Pairs produced. | Pairs alive at end of year.
I IO Bi
Z IIO 12k
3 2 1@ P32 1
A e310 14,641
5 146,410 [6145051
10 OSB. 25,937,424,600

AG eet Ces 700,000,000,000,000,000,000

THE STRUGGLE FOR EXISTENCE 405

Some animals produce vast numbers of eggs or young;
for example, the herring, 20,000; a certain eel, several
millions; and the oyster from 500,000 to 16,000,0CO.
Supposing we start with one oyster and let it produce one
million of eggs. Let each egg produce an oyster which
in turn produces* one million of eggs, and let these go
on increasing at the same rate. In the second generation
there would be one million million of oysters, and in the
fourth, i.e. the great great grandchildren of the first oyster,
there would be one million million million million of
oysters. The shells of these oysters would just about
make a mass the size of the earth.

But it is obvious that all the new individuals of any
animal produced do not live their normal duration of life.
All animals produce far more young than can survive.
As a matter of fact, which we may verify by observation,
. the number of individuals of animals in a state of nature is,
in general, about stationary. There are about as many
squirrels in the forest one vear as another, about as many
butterflies in the field, about as many frogs in the pond.
Some species increase in numbers, as for example, the
rabbit in Australia, which was introduced there in 1860
and in fifteen years had become so abundant as to be a
great pest. Other species decrease, as the buffaloes, which
once roamed our great plains in enormous herds and are
now represented by a total of a few hundred individuals,
and the passenger-pigeon, whose migrating flocks ten years
ago darkened the air for hours in parts of the Mississippi
valley, where now itis a rare bird. But the hand of man
is the agent which has helped to increase or to check the
multiplication of these animals. In nature such quick
changes rarely occur.

* Oysters are hermaphroditic, each individual producing both sperm- and
egg-cells.

406 ELEMENTARY ZOOLOGY

The struggle for existence.—The numbers of animals
are stationary because of the tremendous mortality occa~-
sioned by the constant preying on eggs and young and
adults by other animals, because of strenuous and destruc-
tive climatic and meteorological conditions, and because
there is not space and food for all born, not even, indeed,
for all of a single species, let alone all of the hundreds of
thousands of species which now inhabit the earth. There
is thus constantly going on among animals a fearful
struggle for existence. In the case of any individual this
struggle is threefold: (1) with the other individuals of his
own species for food and space; (2) with the individuals
of other species, which prey on him, or serve as his prey,
or for food and space; and (3) finally with the conditions
of life, as with the cold of winter, the heat of summer, or
drouth and flood. Sometimes one of these struggles is
the severer, sometimes another. With the communal
animals the struggle among individuals is lessened—they
help each other; but when the struggle with the condi-
tions .of life;are easiest, as in the tropics or im thesocean,
the struggle among individuals becomes intensified. Each
strives to feed itself, to save its own life, to produce and
safeguard its young. But in spite of all their efforts only
a few individuals out of the hosts preduced = iine ito
maturity. . The great majority are destroyedsim me o>
or in adolescence.

Variation and natural selection.—What individuals
survive of the many which are born? Those best fitted
for life; those which are a little stronger, a litte suafter,
a. little hardier; a little less readily préeceived@ ay, wack
enemies, than the others. They are the winners in the
struggle for existence; they are the survivors: = e.m@e.tiis
survival of the fittest, as it is called, is practically a process
of selection by Nature. Nature selects the fittest to live
and to perpetuate the species. lheir progenyeacam

THE: SIROGGLE FOR EXISTENCE 407

undergo the struggle and the selecting process, and again
the fittest live. And so on until adjustment or harmoniz-
ing of animals’ bodies and habits with the conditions of
life, with their environment, comes to be extremely fine
and nearly perfect.

It is evident, of course, that such a natural selection or
survival of the fittest and consequent adaptation to en-
vironment presupposes differences among the individuals
of a species. And this is an observed fact. No two
individuals, although of the same brood, are exactly alike
at birth; there always exist slight variations in structure
and performance of functions. And these slight variations
are the differences which determine the fate of the indi-
vidual. One individual is a little larger or stronger or
swifter or hardier than its mates. The existence of this
variation we know from our observation of the young
kittens or puppies of a brood. So it is with all animals.
Thus natural selection depends upon two factors, namely,
the excess in the production of new individuals and the
consequent struggle for existence among them, and the
existence of variations which give certain individuals
slight advantages in this struggle.

Adaptation and adjustment to surroundings.—The
action of natural selection obviously must, and does,
result in a fine adaptation and adjustment of the structure
and habits of animals to their surroundings. If a certain
species or group of individuals cannot adapt itself to its
environment, it will be crowded out by others that can.
A slight advantageous variation comes in time by the
continuously selective process to be a_ well-developed
adaptation.

The diverse forms and habits possessed by animals are
chiefly adaptations to their special conditions of life.
The talons and beak of the eagle, the fishing-pouch of the
pelican, the piercing chisel-like bill of the woodpecker,

408 ELEMENTARY ZOOLOGY

and the sensitive probing-bill of the snipe are adaptations
connected with the special feeding habits of these birds.
The quills of the porcupine, the poison-fangs of the rattle-
snake, the sting of the yellow-jacket, and the antlers of
the deer are adaptations for self-defence. The fins and
gills of fishes, the shovel-like fore feet of the mole, the
wings of birds and insects and bats, the toe-pads of the
tree-toad, the leaping-legs of the grasshopper, all these
are adaptations concerned with the. special life- surround-
ings of these animals.

Adaptations may relate to habits and behavior as well
as to structure. Plainly adaptive are such habits as the
migration of birds and some other animals, most of the
habits connected with food-getting, and especially striking
and interesting those connected with the production and
care of the young, including nest-making and home-
building.

Species-forming.—It is evident that through the cumu-
lative action of natural selection, animals of a structural
type considerably (even unlimitedly) different from any
original type may in time be produced by the gradual
modification of the original type under new conditions.
If, for example, a few individuals of a mainland species
should come to be thrown as waifs of wave and storm
upon an island, and if these should be able to maintain
themselves there and produce young, increasing so as to
occupy the new territory, there would be produced in time
a new type of individual conforming or adapted to the
conditions obtaining in the island, these conditions being,
of course, almost certainly different from those of the
mainland. Thus as an offshoot or derivation from the
original type still existing on the mainland we should
have the new island-inhabiting type. Now when these
island individuals come to differ so much, structurally and
physiologically, from the mainland type that they cannot,

foe STRUGGLE FOR: EXISTENCE 409

even if opportunity offers, successfully mate or interbreed
with mainland individuals the island type constitutes a
new species. That is, our distinction between species
rests not only on structural differences, but on the impossi-
bility of interbreeding (at least for the production of fertile
young). Such a combination of the action of natural
selection and the condition of isolation (as illustrated by
the case of island animals), is probably the most potent
factor in the production of new species of animals (and
plants). |

For accounts of the struggle for existence, variations,
adaptations, natural selection and species-forming see
Barwin s“*@rioin of Species,’’ Wallace's ‘‘ Island Life,’’
and Romanes ‘‘ Darwin and After Darwin,’ I.

Artificial selection.— When a selection among the
individuals of a species, that is, the choosing and preserv-
ing of individuals which show a certain trait or traits and
the destroying of those individuals not possessing this
trait, 15 done by man, it 1s called artificial selection. To
artificial selection we chiefly owe all the many races or
varieties of our domesticated animals and plants. For
example, from the ancestral jungle fowl have been devel-
oped by artificial selection (and by cross-breeding) all our
kinds of domestic fowl, as Brahmas, black Spanish,
bantams, game-cocks, etc. ; from the wild rock-dove have
been developed our various fancy pigeons, as carriers,
pouters, fantails, etc.

For an account of artificial selection see Darwin’s
feeianes and -Animals under. Domestication,’ and
Romanes’ ‘‘ Darwin and After Darwin,’’ I.

CHAPTER XXX

SOCIAL AND COMMUNAL iF. COMMER:
SALISM AND PARASITISM

Social life and gregariousness.—TrcunicaL NorTr. —
Students should refer to examples of gregariousness from their own
observations of animals. The roosting together of crows and of black-
birds ; the gathering of swallows preparatory to migration; the
flocking of geese and ducks, with leaders, in their migratory flights,
all can be readily observed. From observation or general reading
students will be more or less familiar with prairie-dog villages,
beaver-dams and marshes, the one-time great herds of bison, etc.

The struggle for existence is always operative; but in
some cases one or more phases of it may be ameliorated.
For example, the amelioration of the struggle among
individuals of one species obtains in a lesser or greater
degree in the case of those animals which exhibit a soczal
fife, of which mutual aid and mutual dependence are the
basis. The honey-bee and the ants are familiar examples
of animals which show a high degree of social life. They
live, indeed, a truly communal life, where the fate of the
individual is bound up in the fate of the community.
But there are many animals which show a much lower
- degree of mutual aid and a far less colterent ‘society.
The simplest form of social life exists among those animals
in which many individuals of one species keep together,
forming a great. band or herd. In this’ case there i ner
nearly so much mutual aid or mutual dependence as in
that of the honey-bee, and the safety of the individual is

\ot_ wholly ‘bourid up: in the fate of the Memes = such
410

SOCIAL AND COMMUNAL LIFE AII

animals are said to be gregarious in habit, and this gre-
gariousness is undoubtedly advantageous to the individuals
of the band. The great herds of reindeer in the North,
and of the bison or buffalo which once ranged over the
Western American plains are examples of a gregarious-
ness in which mutual protection from enemies, like wolves,
seems to be the principal advantage gained. The bands
of wolves which hunted the buffalo show the advantage
of mutual help in aggression as well as in protection.
Prairie-dogs live in great villages or communities which
spread over many acres. By shrill cries they tell each
other of the approach of enemies, and they seem to visit
each other and to enjoy each other’s society a great deal,
although that they are thus afforded much actual active
help is not apparent. The beavers furnish a well-known
and very interesting example of mutual help; they exhibit
a communal life although a simple one. They live in
villages or communities, all helping to build the dam
across the stream which is necessary to form the marsh
or pool in which the nests or houses are built.

Communal life.—Trcunicat Note.—See technical notes,
pp. 212 ef seg, for directions for work in connection with the study
of the communal life of ants, bees, and wasps.

When many individuals of a species live together in a
community in which the different kinds of work are divided
more or less distinctly among the different members and
where each individual works primarily for the whole and
not for himself; where there is, in other words, a thorough
mutual help and mutual dependence among the members
of the community accompanied by a division of labor, the
life of the species is truly communal. Those animals
which show the most elaborate and specialized communal
fife are the termites or white ants, the social bees and
wasps, and the true ants. Of these the ants and honey-

412 ELEMENTARY ZOOLOGY

bees stand first. As already explained (see pp. 220 ef seq), ©
there are among these communal insects several different
kinds of individuals in each species. With most animals
there are two kinds only, males and females, which may
or may not show differences in color, form, etc., so that
they are readily distinguishable. Among all the com-
munal insects, however, there are always three kinds of
individuals, males, females, and workers, these last being
infertile individuals. With the social wasps and social
bees the workers are all infertile females and are smaller
than the. fertile forms; with the tepaieceme gene sacc
besides the fertile males and females, which are winged,
workers which are wingless, and also peculiar wingless
individuals called soldiers which have very large jaws and
whose business it is to fight off attacking enemies of
the community. Among the ants the workers are also
wingless, while the males and females are winged. The
worker ants in many species are of two kinds, so-called
worker majors and worker minors, differing markedly in
size. All the ant workers are good soldiers, but with
some the fighting is done almost wholly by certain
especially large-headed and large-jawed ones which may
be called soldier-workers.

Thus among all strictly communal animals there is a
specialization or differentiation of individuals accompany-
ing the division of labor. Special individuals have a
certain part of the work of the community to do, and they
are specially modified in structure to do this work. This
structural modification may make them incapable of per-
forming certain other labor or work which is necessary
for their living and which must be done for them, therefore,
by others. Thus the mutual interdependence of the in-
dividuals composing a colony is very real. The worker
honey-bees cannot perpetuate the species; honey-bees
would die out were it not for the males and females. But

SOCIAL AND COMMUNAL LIFE | 4t3

the males and females have given up the functions of food-
getting and of caring for their young; did not the workers
do these things for them, the community would die out
quite as soon.

The advantages of communal or social life, of co-opera-
tion and mutual aid are real. Those animals that have
adopted such a life are among the most successful of all
ieee stucelc. for existence: The termite worker is
one of the most defenseless and for those animals that
prey on insects one of the most toothsome insects, and
yet the termite is one of the most abundant and success-
folly Aevine insect kinds in all the tropics... Ants are
everywhere and are everywhere successful. The honey-
Bee is) a popular type of successful- life. .The artificial
protection afforded it by man may aid it in its struggle
for existence, but it gains this protection because of certain
features of its communal life, and in nature the honey-bee
takes care of itself well. Co-operation and mutual aid
are among the most important factors which help in the
struggle for existence.

Commensalism.—TecunicaL Note.—Examine ants’ nests
to find myrmecophilous insects. If on the seashore search for hermit-

crabs with sea-anemones on shell. If inland, try to have some pre-
served specimens showing the crabs and sea-anemones.

The phases of living together and mutual help just dis-
cussed concerned in each instance a single species of
animal. 2? All the members: of a ‘pack of wolves or of a
honey-bee community belong to a single species. But
there are numerous instances known of the mutually
advantageous association of individuals of two different
species. Such an association is called commensalism or
symbtosts.

The hermit-crabs live, as has been learned (p. 154), in
the shells of molluscs, most of the body of the crab being
concealed within the shell, only the head and the grasping

AI4 ELEMENTARY ZOOLOGY

and walking legs protruding. In some species of hermit-
crabs there is always to be found on the shell near the
opening a sea-anemone. ‘‘ This sea-anemone is carried
from place to place by the crab, and in this way is much
aided in obtaining food. On the other hand, the crab is
protected from its enemies by the well-armed and dan-
serous tentacles of its companion. On the tentacles there
are many thousand long slender stinging threads, and the
fish that would eat the hermit-crab must first deal with
the stinging anemone.’’ If the sea-anemione be torn
away from the shell the crab will wander about seeking
another anemone. When he finds one, he struggles to
loosen it from the rock to which it is attached, and does
not rest until he has torn it loose and placed it on his
shell.

In the case of the hermit-crab and the sea-anemone
there is no doubt of the mutual advantage derived from
their communal life. But this mutual advantage is not
so obvious in some cases of commensalism, where indeed
most or all of the advantage often seems to lie with one
of the animals, while the other derives little or none, but
on the other hand suffers no injury. For example,
‘‘small fish of the genus Vomeus may often be found
accompanying the beautiful Portuguese man-of-war
(Physalia) as it sails slowly about on the ocean's surface.
These little fish lurk underneath the float among the
various hanging thread-like parts of the man-of-war which
are provided with stinging cells. They are protected
from their enemies by their proximity to these stinging
threads, but of what advantage to the man-of-war their

presence is is not understood.’’ Similarly in the nests of
the various species of ants and termites many different
kmds of other msects have been found. ‘‘ Some of these

are harmful to their hosts, in that they feed on the food-
stores gathered by the industrious and provident ant, but

SOCIAL AND COMMUNAL LIFE 41s

others appear to feed only on refuse or useless substances
in the nest. Some may be of help to their hosts by
acting as scavengers. Over one thousand species of these
myrmecophilous (ant-loving) and termitophilous (termite-
loving) insects have been recorded by collectors as living
habitually in the nests of ants and termites.’’

Parasitism.—TecunicaL NoTE.—As examples of temporary
external parasites find and examine fleas and ticks on dogs and cats,
red mites on house-flies and grasshoppers (at the bases of the
wings), etc. As examples of permanent external parasites find
bird-lice on pigeons or domestic fowls or on other birds. Note the
absence of wings and the peculiarly modified body shape of these
parasites. Examine a bird-louse under the microscope ; note the ab-
sence of compound eyes (it has simple eyes) and absence of wings;
note bits of feathers, its food, in stomach, showing through the
body. Find, as examples of internal parasites, intestinal worms or
flukes. Examine trichinized pork to see 7yzchin@ in muscles. Ex-
amine preserved specimens of tapeworms. Collect pupz of some
common butterfly or moth and keep them in the schoolroom until
either the butterflies or ichneumon flies issue. Some will surely be
parasitized, and yield ichneumon flies (parasites) instead of a butter-
fly. As examples of degeneration by quiescence examine barnacles
(found on outer rocks of seashore at low tide; easily obtained as
preserved specimens by inland schools) and the females of scale-
insects. These insects may be found on oleanders (the black scale,
Lecantum ole@) or fruit-trees (the San Jose scale, Asfidiotus per-
niciosus). Note the great degeneration of the adult female of the
San ‘Jose scale; it has no eyes, antennz, wings, or legs. The
young may be found crawling about at certain times of the year ;
they have eyes, antenne, and legs.

In addition to the various ways of living together among
animals, already described, namely, the social and com-
munal life of individuals of a single species and the com-
mensal and symbiotic life of individuals of different species,
there is another and very common kind of association
among animals. This is the association of parasite and
host; the association between two sorts of animals whereby
one, the parasite, lives on or in the other, the host, and at
the expense of the host. In this association the parasite
gains advantages great or small, sometimes even obtain-
ing all the necessities of life, while the host gains nothing,

416 ELEMENTARY ZOOLOGY

- but suffers corresponding disadvantage, often even the loss
of life itself. Parasztzsm is a phenomenon common in
all the large groups of animals, though the parasites
themselves are mostly invertebrates. There are parasitic
Protozoa, worms, crustaceans, insects, and molluscs, and
a few vertebrates.

Some parasites, like the fleas and lice, live on the sur-
face of the body of the host. These are called external
parasites. Others, as the tapeworms, live exclusively
inside the body; such are called zzternal parasites.
Again, some, as the bird-lice, which are external parasites
feeding on the feathers of birds, spend their whole life-
time on the host; they are called permanent parasites.
Others, as a flea, which leaps on or off its host as caprice
directs, or like certain parasites which as young live free
and active lives, finally attaching themselves to some host
and remaining fixed there for the rest of them Miges) ane
called temporary parasites. Such a grouping is purely
arbitrary and exists simply for the sake of convenience.
It is not rigid, nor does it class parasites in their proper
natural groups.

When various parasites are examined it will be noted
that practically in all cases the body of a parasite is
simpler in structure than the body of other animals closely
related to it; that-is, species which live parasitically,
obtaining their food from and being carried about by a
host, have simpler bodies than related forms that live free
active lives, competing for food with other animals about
them. This simplicity is not primitive, but results from
the loss or atrophy of the structures which the special
mode of life of the parasite renders useless. Many para-
sites are attached firmly by hooks or suckers to their host,
and do not move about independently of it. They have
no need of the power of locomotion, and accordingly are
usually without wings, legs, or other locomotory organs.

SOCIAL AND COMMUNAL LIFE ye |

Because they have no need of locomotion they have no
need of organs of orientation, those special sense organs
like the eyes, ears, and feelers which serve to guide and
direct the moving animal; and most fixed parasites will
be found to have no eyes, or any of those organs acces-
sory to locomotion, and which serve for the detection of
igod) ei 61 enemies. Because’ these important organs,
which depend for their successful activity on a well-organ-
ized nervous system, are lacking, the nervous system of
parasites is usually very simple. Again, because the
parasite usually feeds on the already digested food or the
blood of its host, most parasites have a very simple ali-
iiet@katy canal, or even-none at all. Finally, as the fixed
parasite leads a wholly sedentary and inactive life, the
breaking down and rebuilding of tissue in its body goes
on very slowly and in minimum degree, so that there is
little need of highly developed respiratory and circulatory
systems; and most fixed and internal parasites have these
systems of organs decidedly simplified. Altogether the
body of a fixed permanent parasite is so simplified and so
wanting in all those special structures which characterize
the active, complex animals that it often presents a very
different appearance from those forms with which we know
it to be nearly related. This, simplicity due to loss or
reduction of parts is called degeneration. Such simplicity
of body-structure due to degeneration is, however, essen-
tially different in its origin from the simplicity of the lower
simpler animals. In them the simplicity of body is prim-
itive; they are generalized animals; the simplicity of
degeneration is acquired; it is really an adaptation, or
specialization. _

An excellent example of body degeneration due to the
adoption of a parasitic habit is that of Sacculina (fig. 159),
a crustacean parasitic on other crustaceans, namely, crabs.
The young Sacculina is an active, free-swimming larva

Ane ELEMENTARY ZOOLOGY

essentially like a young prawn or crab. After a short
period of independent existence it attaches itself to the
abdomen of a crab, and lives as a parasite. It completes
its development under the influence of this parasitic life,
and when adult bears absolutely no resemblance to such

Fic, 159.—Sacculina, a parasitic crustacean; A, attached to a crab, the
root-like processes of the parasite penetrating the body of the host; 4,
the active larval condition; C, the adult removed from its host. (After
Haeckel.)

a typical crustacean as acrab or crayfish. Its body ex-
ternal to the host crab is simply a pulsating tumor-like
sac, with no mouth-parts, no legs, and internally hardly
any well-developed organs except those of reproduction.
Degeneration here is carried very far.

SOCIAL AND COMMUNAL LIFE 419

Various parasites have been referred to in Part II under
their proper branch and class. The worms include an
unusually large number of them, such as the tape-
worms, trichine and other intestinal forms, all of which
live as internal parasites in the alimentary canal or in
other organs of higher animals, especially the vertebrates.
Many crustaceans are parasitic, usually living, like the
fish-lice, as fixed external parasites on fishes, other crus-
taceans, etc., but with a free and active larval stage.
Among: the insects, on the contrary, many of the parasitic
forms (as the ichneumon flies) are free and active in the
adult stage, but live as internal grubs or maggots in the
larval stage. The ichneumon flies (of the order Hymen-
optera) are four-winged, slender-bodied insects which
lay their eggs either on or in (by means of a sharp pierc-
ing ovipositor) some caterpillar or beetle grub, into the
body of which the young grub-like ichneumon larve
burrow on hatching. The parasites feed on the body-
tissues of the host, not attacking, however, such organs
as the heart or nervous system, which would produce the
immediate death of the host. The caterpillar lives with
the tchneumon grubs within it usually until nearly time
for its pupation. Often, indeed, it pupates with the para-
site still in its body. But it never comes to maturity.
The larval ichneumons pupate either within the body of
its host, or in a tiny silken cocoons outside of its body
(fig. 160). From the cocoons the winged adult ichneu-
mons issue; and after mating the females find another
caterpillar on whose body to lay their eggs.

Degeneration can be produced by other causes than
parasitism. It is evident that if for any other reason an
animal should adopt an inactive fixed life it would degen-
erate. The barnacles (see fig. 37) are excellent examples
of degeneration through quiescence. They are crustaceans
related most nearly to the crabs and shrimps. The

420 ELEMENTARY ZOOLOGY

young barnacle just from the egg is a six-legged, free-
swimming larva (nauplius) with a single eye, greatly like
a young prawn or crab. It develops during its independ-
ent life two compound eyes and two large antenne. But
soon it attaches itself to some
stone or shell, or pile or ship’s
bottom, giving up its power of
locomotion, and its further de-
velopment is adegeneration. It
loses its compound eyes and an-
tenne, and acquires a protecting
shell. Its swimming feet become
modified into grasping organs,
and it loses most of its outward
resemblance to the typical mem-
bers of its. class: hes (iimicata
or ascidians compose a whole
group of animals which are fixed
in their adult condition and have
thus become desenerate. “1 hey
have been likemed?toBa se =amere
rooted bag with a double neck.’’
In their youne stagemthey are
free-swimming, active, tadpole-
like or fish-like larve, possessing

Fic. 160.—Larva of a sphinx-
moth, with cocoons of a para-
sitic ichneumon fly. (From organs much like those of the

ea adult simplest fish or fish-like
animals: -Their larval structure reveals, however) tie
relationships of the ascidians to the vertebrates, a rela-
tionship which is not at all apparent in the degenerate
adults. Certain insects live sedentary or fixed lives. All
the members of one large family, the Coccide, or scale-
insects (figs. 62 and 63), have females which as adults are
wingless and in some cases have no legs, eyes, or antennae,
while the males are all winged and have legs and the

SOCIAL AND: COMMUNAL LIFE 421

special sense organs. The males lead a free active life,
but the females have nearly or quite given up the power
of locomotion, attaching themselves by means of their
sucking beak to some plant, where they obtain a suffi-
cient food-supply (plant-sap) and lay their eggs. In both
males and females the larve are little active crawling six-
legged creatures with legs, eyes, and antenne.

We are accustomed perhaps to think of degeneration
as necessarily implying a disadvantage in life. It is true
that a blind, footless, degenerate animal could not cope
with the active, keen-sighted, highly organized non-
degenerate in free competition. But free competition is
exactly what the degenerate animal has nothing to do
with. Certainly the Sacculizna and the scale-insects live
well; they are admirably adapted to the kind of life they
lead. A parasite enjoys certain obvious advantages in life,
and even extreme degeneration is no drawback (except as
we shall see later), but gives ita body which demands less
food and care. As long as the host is successful in elud-
ing its enemies and avoiding accident and injury the para-
Site is safe. Its life is easy as long as the host lives.
‘But the disadvantages of parasitism and degeneration are
nevertheless obvious. The fate of the parasite is bound
Woewiemerte tate of. the host. “When the enemy of the
host crab prevails, the Sacculzna goes down without a
chance to struggle in its own defence. But far more im-
portant than the disadvantage in such particular or indi-
vidual cases is the fact that the parasite cannot adapt itself
in any considerable degree to new conditions. It has
become so modified, so specialized to adapt itself to the
very special conditions under which it now lives, it has
gone so far in giving up organs and functions, that if
present conditions change and new ones come to exist
the parasite cannot adapt itself to them. The independ-
ent free-living animal holds itself, one may say, able and

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ELEMENTARY ZOOLOGY

2

SOCIAL AND COMMUNAL LIFE 4223

ready to adapt itself to any new conditions of life. The
parasite has risked everything for the sake of a sure and
easy life under the present existing conditions. Change
of conditions means its extinction.’’

For an elementary account of commensalism and para-
sitism see Jordan and Kellogg’s ‘‘ Animal Life,’’ pp. 172-
2e@- fhe account here given is based on the author’s
previously written account in ‘‘ Animal Life.’’ ‘See also

Van Beneden’s ‘‘ Animal Parasites and Messmates.

>)

CHAPTER XXXI
COLOR AND PROTECTIVE RESEMBELANEGES

TECHNICAL NOTE.—For an appreciation of the reality of pro-
tective resemblances observations must be made in the field. Ex-
amples are easily found. Locusts, katydids, green caterpillars,
lizards, crouching rabbits, and brooding birds are readily observed
instances of general protective resemblance. For examples of
variable resemblance examine specimens of a single locust species
taken from different localities ; the individuals of the various species
of the genus 7rimerotropis show much variation to harmonize
with their surroundings. Collect a number of larvae (caterpillars) of
one of the swallow-tail butterflies (/afz/i0), and when ready to
pupate put them separately into pasteboard boxes lined inside with
differently colored paper. The chrysalids will show in their colora-
tion the influence of the different colors of the lining paper, their
immediate environment. As examples of special protective resem-
blance observe inch- or span-worms (larvae of Geometrid moths).
The walking-stick 1s not uncommon; many spiders that inhabit
flower-cups show striking protective color patterns; and the
Graptas or comma-butterflies which resemble dead leaves may be
examined.

To illustrate warning colors, find, if possible, the larvz (cater-
pillars) of the common milkweed or monarch butterfly (Anosza
plexippus), and offer them to birds, at the same time offering other
caterpillars, and note the results. For terrifying or threatening
appearance find specimens of the large green tobacco- or tomato-
worm (larva of the five-spotted sphinx-moth, Phlegethontius caro-
fina), or other sphingid larve.

The butterflies illustrating the striking example of mimicry, de-
scribed on. p. 432, can be found: in most pants of thiemeomntry.
Syrphid and other flies which mimic bees and wasps can readily
se found on flowers.

Fach student should search for himself for examples of pro-
tective resemblance.

Use of color.—The prevalence of color and the often-
times striking and intricate coloration patterns of animals
424

COLOR AND PROTECTIVE. RESEMBLANCES 425

demand some explanation. As naturalists are accustomed
to find the frequently bizarre and seemingly inexplicable
shapes and general structure of animals readily explained
by the principle of adaptation, that is, special modification
of body-structure to fit special conditions of life, so they
look to use as the chief explanation of color and markings.
Some uses are obvious; bright colors and striking patterns
may serve to attract mates or to avail as recognition
marks by which individuals of a kind may readily recog-
nize each other. The white color of arctic animals prob-
ably serves to help keep them warm by preventing
radiation of heat from the body; on the other hand dark
color may also help to keep animals warm by absorbing
heat. ‘‘ But by far‘the most widespread use of color is
for another purpose, that of assisting the animal in escap-
ing from its enemies or in capturing its prey.’

It is common knowledge that the young and old, too,
of many kinds of ground-inhabiting animals, when startled
by an enemy will not run, but crouching close to the
ground remain immovable, trusting to remain unper-
ceived. But a blue or crimson rabbit, however still it
might keep, would be easily seen by its enemy and killed.
Rabbits, however, which are good examples of animals
having this habit of lying close, are neither blue nor green
nor red, but are colored very much like the ground on
which they crouch. This harmonious coloration is as
necessary to the success of this habit as is the keeping
still. A grasshopper flying or leaping in the air is con-
spicuous; when it alights how inconspicuous it is! Unless
one has followed it closely in its flight and has kept the
eye fixed on it after alighting it is usually impossible to
distinguish it from its surroundings. And this is greatly
to the advantage of the grasshopper in its efforts to
escape its enemies, that is, in its struggle for existence.
On the other hand a green katydid would be very con-

426 ELEMENTARY ZOOLOGY

spicuous in a dusty road. But dusty roads are precisely
where katydids do not rest. They alight among the
ereen leaves of a tree or shrub. The animals that live in
deserts are almost all obscurely mottled with gray and
brownish and sand-color so as to harmonize in color with
their habitual environment. The arctic hares and foxes
and grouse which live in regions of perpetual snow are
pure white instead of red or brown or gray like their
cousins of temperate and warm regions.

These cases of an animal’s color and markings har-
monizing with the usual environment are called instances
of protective resemblance ; that is, they are resemblances
for a purpose, that purpose being to render the animal in-
distinguishable from its surroundings and thus to aid it in
escaping its enemies. Such protective resemblances are
obviously of great value to animals, and, like other
advantageous modifications, have been produced by the
action of natural selection. Those individuals of a species
most conspicuous and hence most readily perceived by
enemies are the first (under ordinary circumstances) to
be captured and eaten. The less conspicuous live and
produce young like themselves. Of these young the least
conspicuous are again saved and so over and over again
through thousands of generations until this natural select-
ing of the protectively colored results in the production
of the wonderfully specialized examples of resemblance
to which attention is called in the following paragraphs.

General, variable, and special protective resemblance.
—In the brooks most fishes are dark olive or greenish
~above and white below. To the birds and other enemies
which look down on them they are colored like the
bottom. To their fish-enemies which look up from below
they are like the white light above them in color and their
forms are not clearly seen. The green tree-frogs and
tree-snakes which live habitually among green foliage;

COLOR AND PROTECTIVE RESEMBLANCES 427

the mottled gray and tawny lizards and birds and smal]
mammals of the plains and deserts, and the white hares and

foxes and owls and ptar-
migan of the snowy arctic
regions—all show a gener-
al protective resemblance.

Sometimes an animal
changes color when its sur-
roundings change. Certain
hares and grouse of north-
ern latitudes are white in
winter when the snow
covers all the ground, but
in summer when much of
the snow melts, revealing
the brown and gray rocks
and withered leaves, they
put. oma. grayish and

prownisw coat -of hair or

feathers. A small insect
called the toad-bug (Gal/-
gulus) lives abundantly on
the banks of a pond on the
campus of Stanford Uni-
versity. The shores of
this pond are covered in
some places with bits of
bluish rock, in others with
bits of reddish rock, and
in still others with sand.
Specimens of the toad-bug
collected from the blue

Fic. 162.—-The twig or walking-stick
insect, Diapheromera femorata.
(From specimen. )

rocks are bluish or leaden in color, those from the red rocks
are reddish, and those from the sand are sand-colored.
Changes of color to suit the surroundings can be quickly

428 ELEMENTARY ZOOLOGY

- made by some animals. The chameleons of the tropics
change momentarily from green to brown, blackish, or
golden. There is a little fish (Olzgocottus snydert) com-
mon in the tide-pools of the Bay of Monterey in California
whose color changes quickly to harmonize with the rocks
it happens to rest above. Such changing coloration to
suit the surroundings may be called warzable protective
resemblance.

Very striking are those cases of protective resemblance
in which the animal resembles in color and shape, some-
times in extraordinary detail, some particular object or
part of its usual environment. This may be called speczal
protective resemblance. The larve of the Geometrid
moths called inch-worms or span-worms are twig-like in
appearance, and have the habit, when disturbed, of stand-
ing out stiffly from the twig or branch on which they rest,
so as to resemble in attitude as well as color and mark-
ings a short or broken twig. To increase this simulation
the body of the larva often has a few irregular spots or
humps resembling the scars left by fallen leaves, and it
also lacks the middle prop-legs of the body common to
other lepidopterous larva, which would tend to destroy
the illusion so successfully carried out by it. The common
twig-insect or walking-stick (fg. 162) with its wingless,
creatly elongate, brown or greenish body and legs is when
at rest quite indistinguishable from the twigs on which it
lies. - Another excellent example of special protective
resemblance is furnished by the famous green-leaf insect
(Phyllum) of the tropics, which has broad leaf-like wings
and body of a bright green color with markings which
imitate the leaf-veins, and small irregular yellowish spots
which simulate decaying or stained or fungus-covered
spots in the leaf. Most striking of all, however, is the
large dead-leaf butterfly Kalima (fig. 163) of the East
Indian region. The upper sides of the wing are dark

COLOR AND PROTECTIVE RESEMBLANCES 429

ce
b
4
4
4

Fic. 163.—The dead-leaf butterfly, Aa//ima sp., a remarkable case of
special protective resemblance. (From specimen. )

430 ELEMENTARY ZOOLOGY

with purplish and orange markings not at all resembling
a dead leaf. But the butterflies when at rest hold their
wings together over the back, so that only the under sides
of them-are ‘exposed. - These are exactly thearer of a
dry dead leaf with markings mimicking midrib and
oblique veins, and, most remarkable of all, what are
apparently two holes like those made in leaves by insects,
but in the butterfly imitated by two small circular spots
free from scales and hence clear and transparent. When
Kaliima alights it holds the wings in such position that the
combination of all four produces with remarkable fidelity
the simulation of a dead leaf still attached to the twig by
a short pedicel or leaf-stalk (imitated by a short ‘tail ”’
on the hind wings). The head and legs of the butterfly
are concealed beneath the wings.

Warning colors, terrifying appearances, and mimicry.
—While many animals are so colored as to harmonize
with their habitual or usual environment, others on the
contrary are very brightly colored and marked in such
bizarre and striking pattern as to be conspicuous. There
is no attempt at concealment; it is obvious that conspicu-
ousness is the object sought or at least produced by the
coloration. Animals like these, we shall find, are in
almost all cases specially protected by special weapons of
deferice such as stings or poison-fangs, or by the secretion
of an acrid, ill-tasting fluid in the body. Many cater-
pillars have been found, by observation in nature and by
experiment, to be distasteful to insectivorous birds. Now
it is obvious that it would be advantageous to these cater-
pillars to be readily recogmized by birds], Atter 2 icw
trials the bird learns by experience to let these distasteful
larve alone; their conspicuous markings serve as waruing
colors. Yhe black-and-yellow-banded caterpillar of the
common milkweed or monarch butterfly (Axzosza plexip-
pus) is a good example of such protection by a combina-

COLOR AND PROTECTIVE RESEMBLANCES 431

tion of distastefulness and warning coloration. The little
lady-bird beetles are mostly distasteful to birds; they are
brightly and conspicuously marked. Certain little Nica-
raguan frogs have a bright livery of red and blue, in strong

Fic. 164.—The larva of the pen-marked sphinx-moth, Sphinx chersts,
showing terrifying attitude. (After Comstock.)

contrast to the dull concealing colors of other frogs in
their region. By offering these little blue and red frogs
to hens and ducks the naturalist Belt found that they are
distasteful to the birds.

Certain animals which are without special means of
defence and are not distasteful are yet so marked or
shaped and so behave as to present a threatening or
terrifying appearance. The large green caterpillars of
the sphinx-moths, the tomato- and tobacco-worms, are

432 ELEMENTARY ZOOLOGY

familiar examples, each larva having a sharp horn on the
back of the next to last body-segment (fig. 164). When
disturbed the caterpillar assumes a threatening attitude,
and the horn seems to be an effective weapon of defence.
As a matter of fact it is not at all a weapon of defence,
being weak, not provided with poison, and altogether
harmless.

But it would plainly be to the uae of a defence-
less animal, one without poison-fangs or sting and without
an ill-tasting substance in its body, to be so marked and
shaped as to mimic some other specially defended or
inedible animal sufficiently to be mistaken for it and thus
to escape attack. Such cases have been noted, especially
among insects. This kind of protective resemblance may
be called mzmecry. A most striking case is that presented
by the familiar monarch and viceroy butterflies (fig. 165).
The monarch (Anosia plexippus) is perhaps the most
abundant and widespread butterfly of our country. It is
a fact well known to entomologists that it is distasteful to
birds and is let alone by them. It is conspicuous, being
large and chiefly red-brown in color, The viceroy
(Lastlarchia archippus), also red-brown and patterned
almost exactly like the monarch, is not, as its appearance
would seem to indicate, a very near relation of the latter,
but ‘on the contrary it belongs to a genus pf Burveriics
all of which, except the viceroy and one other, are black
and white in color and of different pattern from the
monarch. The viceroy is not distasteful to birds, but by
its extraordinary simulation or mimicking of the monarch
it is not distinguished from it and so is not molested. In
the tropics there have been discovered numerous examples |
of mimicry among insects. The members of two large
families of butterflies (Danaidz and Heliconidz) are dis-
tasteful to birds and are mimicked by members of other
butterfly families (especially the Pieridz).

COLOR AND PROTECTIVE RESEMBLANCES ASS

A few animals show what is

Alluring coloration.
called alluring coloration; that is, they display a color
pattern so arranged as to resemble or mimic a flower or
other lure, and thus entice to them other animals, their

—

-

Frc. 165.—The monarch butterfly, Avosia plexippus (above), distasteful to
birds, and the viceroy, Baszlarchia archippus (below), which mimics it.
From specimens. )

natural prey. Certain Brazilian fly-catching birds have a

brilliantly colored crest which can be displayed in the

shape of a flower-cup. The insects attracted by the false
flower furnish the bird with food. In the tribe of fishes
called the ‘‘anglers’’ or ‘‘ fishing frogs,’’ the front rays
of the dorsal fin are prolonged in the shape of long slender
filaments, the foremost and longest of which has a flat-
tened and divided extremity. The angler conceals itself
in the mud or in the cavities of a coral reef, and waves
the filament back and forth. Small fish are attracted

434 ELEMENTARY ZOOLOGY

by the lure, mistaking it for worms writhing about. When
they approach they are engulfed in the mouth of the
angler, which in some species is of enormous size. One
of these angler species is known to fishermen as the
‘all-mouth. ”’

For a fuller account of protective resemblances and
mimicry see Jordan and Kelloge’s ““Amiinalieeie =pp.
201-223. - For still more extended accounts See, Poenlton s
‘*Colours of Animals,’’ and Beddard’s ‘‘ Animal Colora-
tion.”

CHAPTER XXXII
Gee Dist RIBUTION-OF ANIMALS

TECHNICAL NOTE.—The larger aspects or phenomena of the dis-
tribution of animals over the earth on land and in sea cannot be
studied personally in the field by the student, but many local fea-
tures of distribution can be so observed and studied. The restric-
tion of certain kinds of animals to certain kinds of habitat, the
presence and character and effectiveness of barriers, some of the
modes of distribution, the presence and successful life of introduced
foreign species such as the black and brown rats, the English
sparrow, the German and Asiatic cockroaches, the gradual change
of range or distribution of certain kinds of animals through the in-
fluence of a change in environment (caused by man in cutting off
forests, cultivating heretofore wild pastures, etc.) all offer favorable
and profitable opportunities for personal observation.

An excellent and feasible piece of field-work in distribution is the
making of a zoological survey of the locality in which the school is
situated. A map of the locality should be made on a generous
scale, which should include all prominent physical features of the
region, such as streams, ponds, hills, woodlands, marshes, etc.,
and on this map should be indicated the places where the various
animals of the local fauna occur. Some of the animal species will
have a limited range, and the limits of this range should be shown.
This map and faunal list can be added to and perfected by succes-
sive classes. For fuller discussions of the geographical distribution
of animals see Jordan and Kellogg's ‘‘ Animal Life,” Beddard’s “ Zoo-
geography,’ Heilprin’s ‘ The Distribution of Animals,” and Wallace’s
‘Geographical Distribution.”

Geographical distribution.—It is a matter of common
knowledge with all of us that there are no wild lions or
camels or kangaroos or monkeys or ostriches or night-
ingales in North America. Ostriches are found only in
Africa and South America, kangaroos only in Australia,

435

s

436 ELEMENTARY ZOOLOGY

lions only in Asia and Africa. On the other hand there
are no opossums in Europe or grizzly bears or rattlesnakes
anywhere else in the world than in this country. That
is, certain kinds of animals have a certain limited range of
occurrence or distribution. It is obvious, too, that certain
animals live only on land, while others live only in water,
and of these latter some are restricted to the ocean, while
others live only in fresh water. All of the tacts meaarcd-
ing the dispersion or diffusion of animals on land and in
water make up the science of the geographical distribution
of animals, or, as it is sometimes called, soogeography.
Under this subject are included not only the facte at the
present actual distribution or occurrence of animals over
the world, but the facts concerning the reasons for this
distribution, the modes of travel and dispersion, the char-
acter and influence of barriers to the spread, “and the
results, in the adaptation of old forms and the production
of new forms, of the phenomena of distribution.

Just as maps are made to show graphically the facts of
political geography, which concerns the position and
extent of the various powers and States which claim
the allesiance of the’ people, and the met crap sical
geography, which concerns the physical character of the
earth’s surface, so maps are made to show the geograph-
ical distribution of animals. Because of the great numbers
of animal species no one map can show the distribution
of all species, but a series of maps of the world or of a
continent or of a State or county or more limited region
could be made (and many such have been made) showing
the distribution of selected species. In a map of a limited
locality, say of a few square miles, the occurremee and
distribution of most of the commoner and more familiar
animals can be shown, and each high school should
possess such a map (see technical note at beginning of
this chapter).

THE DISTRIBUTION OF ANIMALS 437

Laws of distribution.—The laws governing the distri-
bution of animals over the earth’s surface have been
recently * expressed in a simple statement as follows:
Every species of animal is found in every part of the earth
unless (a) its individuals have been unable to reach this
region on account of barriers of some sort; or (4) having
reached it, the species is unable to maintain itself, through
lack of capacity for adaptation, through severity of com-
petition with other forms, or through destructive conditions
of environment; or (¢c) having entered and maintained
itself it has become so altered in the process of adaptation
as to become a species distinct from the original type.

Modes of migration and distribution.—That animals
should be continually trying to extend their range is
obvious from what we know of their rapid increase by
multiplication. In a region which can provide food for
but one thousand wolves, there is a production each year
of several times one thousand. These new wolves must
struggle among themselves for food, or migrate, if possi-
ble, to new regions as yet not inhabited by wolves. The
wolf's mode of migration or distribution is walking or
running, and so with other mammals except the bats and
aquatic forms. Birds and bats can fly, and can thus
migrate more swiftly, farther, and over barriers which
would stop mammals. Most insects can fly. Worms
can only crawl and very slowly at that. Fishes can swim,
but if they are in a landlocked sheet of water, they cannct
go beyond its confines. Marine animals can migrate
from ocean to ocean, and land animals from continent to
continent unless checked by barriers (see next para-
graph).

But besides such voluntary and independent modes of
distribution long journeyings may be made involuntarily,
or by a passive migration as it may be called. Parasites,

* Jordan and Kellogg’s ‘‘ Animal Life,” 1900, p. 274.

438 | ELEMENTARY ZOOLOGY

for example, are carried by their hosts in all their travels;
the tiny Tardigrada and Rotifera, which can be desiccated
and yet restored to active life by coming again into water,
are carried in the dried mud on the feet of birds or. other
animals. On floating objects in rivers or in ocean cur-
rents land-animals may be carried long distances. Man,
the greatest traveller of all, is responsible for the widened
distribution of many animals. ‘Thus have come to us in
ships from Europe the black and brown rats, the English
sparrow, the Hessian fly, the commonest cockroaches of
our houses and many other forms. And these animals
have been carried involuntarily all over the United States
in railway-cars and wagons.

Barriers to distribution.—<As is indicated in the para-
graph on the modes of migration, a considerable sheet of
water is obviously a barrier to the further travelling of a
walking or crawling land-animal, although no barrier to
a winged form. Similarly a strip of land is a barrier to a
strictly aquatic animal as ‘a fish. Or a ie@h tp am the
stream may serve as an insuperable barrier, making it im-
possible for any fish below the fall to reach the upper
part of the.stream. Numerous cases of this danmd= are
known in the Rocky Mountains and Sierra Nevada, where
a stream may be well supplied with trout below a fall,
and--quite : bare of these fish abeve the siali amas rnc
Yosemite Valley in California trout live in the Merced
River below the great Vernal and Nevada falls, but above
these falls the Merced contains no trout. To fresh-water
swimming animals salt water may be a barrier; thus some
kinds of fresh-water fishes are limited to one of two
near-by streams although the mouths of these streams
empty near each other into the ocean. The amphibious
batrachians, .at home in fresh water andvom sland are
killed by contact with sea-water. Earthworms also are
killed by salt water. Thus the narrowest ocean strait is

THE DISTRIBUTION OF ANIMALS 439

as effective a barrier to these animals as a whole sea.
High mountain ranges and broad deserts are barriers to
many land-animals, partly because of the physical ob-
stacles, partly because of the differences in temperature
and in food-supply.

Temperature and climate (as distinct from temperature)
and the ocean are the three great barriers when we con-
sider the animal kingdom as a whole, and look for the
causes which determine the chief zoogeographical divisions
of the earth’s surface. Most of the tropical animals
cannot endure frost, hence the isothermal line of frost is
a line across which few tropical animals venture. Most
arctic animals are enfeebled by heat, and the isothermal
line which marks off the region in which frost occurs the
year round is another great zoogeographical boundary.
But while these lines are limits for localized species, some
animals, as birds, especially, keep within a relatively
uniform temperature by migrations across these lines. It
should be borne in mind that the gradual decrease in
temperature met with in going north or south from the
tropics is also met in the ascent of high mountains. The
summits of lofty peaks, even in the tropics, are truly
acetic wm) character; they are snow-covered, and. the
animals and plants on them are truly arctic. Thus in the
ascent of a single mountain a whole series of life-zones
from tropical to arctic can be traversed.

Climate, as distinct from temperature, establishes limits
of distribution. The animals of Eastern North America
accustomed to a humid atmosphere cannot live in the dry
plains and deserts of the West. Closely associated with
climate is the nature of the plant-growth covering the
land; here are forests and luxuriant meadows, there are
sparse tough grasses of the dry plateau. The limits of a
special kind of plant-growth often are the limits of distri-
bution of certain animals.

440 ELEMENTARY ZOOLOGY

The third great barrier, the ocean, is perhaps tiie most
obvious of all in its influence. It is only in rare cases
that any land-animal can independently cross a great
ocean. Thus the land-animals of Australia differ from
those of all other countries, and those of Africa and South
America have developed almost independently of one
another. The ocean is, as already mentioned, also 2
barrier for fresh-water aquatic animals, and even marine
fishes which live normally in shallow waters along the
shore rarely venture across the great depths of mid-ocean.

The obstacles or barriers met with determine the limits
of a species. Each species broadens its range as far as it
can. It attempts unwittingly, through natural processes
of increase, to overcome the obstacles of ocean or river,
of mountain or plain, of woodland or prairie or desert, of
cold or heat, of lack of food or abundance of enemies—_
whatever the barriers may be. The degree of hindrance
offered by any barrier differs with the nature of the animal
trying to pass it. That which forms an impassable
obstacle to one species may be a great aid to the spread
of another. ‘‘ The river which blocks the monkey or the
cat is the highway of the fish and turtle. The waterfall
which limits the ascent of the trout is the chosen home of
the ouzel.”’

Faune and zoogeographic areas.—The term fauna is
applied to the animals of any region considered collect-
ively. Thus the fauna of Illinois includes the entire list
of animals found naturally in that State. The fauna of a
schoolyard comprises all the animals found living naturally
in the yard. The fauna of a pond includes all the animal
inhabitants of the pond. (//7ora is used similarly of all
the plants in a given region.) The relation of one fauna
to another depends on the character and effectiveness of
the barriers between, and the physical character of the
two regions. Thus the fauna of Illinois differs but little

THE DISTRIBUTION OF ANIMALS 441

from that of Indiana or Iowa, because there are no barriers
between the States, and they are alike physically. On
the other hand the fauna of California differs much from
that of the Eastern States because of the great barriers
(the desert and the Sierra Nevada Mountains) which lie
between it and these States, and because of the great
differences in the physical and climatic conditions of the
two regions.

The land-surface of the earth has been divided by
zoogeographers into seven great realms of animal life,
based on the distributional characters shown by these
various regions. These realms are separated by barriers
of which the chief are the presence of the sea and the
occurrence of frost. These realms are named, from their
geographical region, the Arctic, the North Temperate,
the South American, the Indo-African, the Madagascar,
the Patagonian, and the Australian. Of these the
Australian alone is sharply defined. Most of the others
are surrounded by a broad fringe of debatable ground
that forms a transition to some other zone.

Habitat and species.—The habitat of a species of
animal is the region in which it is found in a state of
nature. It is currently believed that the habitat of any
animal is the whole of that region for which it is best
adapted. But this is not necessarily true. In fact in
most cases itis not true. The trout naturally debarred
from the rivers in Yellowstone Park by the waterfalls
could live there well if the barrier could be passed. In
the case of one stream it has been passed and the trout
flourish above the fall. The success of the black and
brown rats and the English sparrow in America, of the
rabbit in Australia, of bumblebees and house-flies in New
Zealand, all of which animals had a natural habitat not
including these regions, but by artificial means have been
carried over the barriers and into che new territory, prove

442 ELEMENTARY ZOOLOGY

that ‘‘habitat’’ is not necessarily coincident with ‘‘ only
fit region.’’ Shad, striped bass, and catfish from the
Potomac River have been introduced into and now thrive
in the Sacramento River in California. In fact the whole
work of the introduction and diffusion of valuable food-
animals in territory not naturally included in the habitat
of the species is based on our knowledge that the habitat
of a species is often determined by physical barriers rather
than by exclusive fitness of environment. Within the
natural habitat the environment zs fit for the species’
existence, outside of it the environment may be fit.

But there occur numerous instances where a species
successful in leaving its orignal habitat is unsuccessful in
attempting to maintain itself on new ground. Man has
introduced various animals from one country to another.
The English sparrow (naturally debarred from this country
by the ocean barrier), brought to America from Europe,
has covered its new territory rapidly and maintains itself
with brilliant success. But the nightingale, the starling
and skylark which have been repeatedly introduced and
set free are unable to maintain themselves here.

Species-extinguishing and species-forming.— Accom-
panying the constant slow migrating of species into new
habitats and the constant slow changing of environment
and conditions everywhere is to be seen a constant modi-
fication of the fauna of any region due to the inability of
some species to maintain their ground, the predominating
increase of others, and the modifying or adaptive chang-
ing of others into new forms. In 1544 the black rat of
Europe was introduced into America and it soon crowded
out the native rats, being in its turn crowded out by the
European brown rat (the present common rat in buildings),
introduced about 1775. Here we have the original native
species unable to maintain itself in competition with in-
troduced forms.

THE DISTRIBUTION OF ANIMALS 443

With a change of environing conditions, certain species
are unable to maintain themselves. With the destruction
of the forests going on in parts of our country the great
host of wood-creatures, the bears, squirrels, the wood-
birds and insects, can no longer maintain themselves, and
grow rare and disappear. Man often also influences the
status of a species by checking its increase either by
actual slaughter, as with the bison and passenger-pigeon,
or by making adverse changes in its environment, as by
destroying forests, or putting the plains under cultivation.

In the discussion of ‘‘ species-forming ’’ (see p. 408) it
was shown that adaptation may lead to the altering of
species, and to the formation of new ones (under the in-
fluence of natural selection). With the gradual change of
conditions, or with the facing of new conditions because
of an unusual migration to or invasion of new territory,
those individuals of the species exposed to the new con-
ditions must adapt themselves in structure and habit in
order to meet successfully the new demands. By the
cumulative action of natural selection these adaptive
changes are emphasized; and this emphasis may come to
be so pronounced that the part of the species represented
in this newly acquired territory, if isolated from the orig-
inal stock, is so altered as to be quite distinct in apnear-
ance from the old. If these changed individuals are also
physiologically distinct from the old stock, i.e. are
unable to mate with them, a new species is established.
As already mentioned, the peopling of islands from main-
lands is an excellent and readily observable example of
the phenomena referred to in the third law of distribution.

APPENDICES
EQUIPMENT AND METHODS

APPENDIX |]
EQUIPMENT AND NOTES OF PUPILS

Equipment of pupils.—Each pupil should have a
laboratory note-book of about 8 & IO inches, opening at
the end, in which both drawings and notes can be made.
The paper should be unruled and of good quality (not too
soft). Each pupil should have also instruments of his
own as follows: scalpel, pair of small scissors, spring
forceps, pair of dissecting-needles, small glass pipette, and
paper of ribbon-pins for pinning out specimens. The cost
of this outfit need not exceed $1.00. The laboratory
should furnish him with a dissecting-dish and a dissecting-
microscope, or at least a lens.

Laboratory drawings and notes.—Each pupil should
make the drawings called for in the directions for the
laboratory exercises. These drawings should be in out-
line, and put in by pencil; the lines may be inked over if
preferred. Shading should be used sparingly, if at all.
Each drawing and all the organs and animal parts repre-
sented in it should be fully named. See the anatomical
plates in this book for example. With such complete
‘‘jabelling,’’ little note-taking need be done in connec-
_ tion with the dissections.

Notes should be made of any observations which cannot
be represented in the drawings; for example, on the

447

a48 APPENDIX

behavior of the living animals. All notes referring to
matters of life-history should be dated.

Field-observations and notes.—Scattered through this
book will be found numerous suggestions for student field-
work, for the observation of the life-history and habits and
conditions of animals in nature. As explained in the
Preface, the initiation and direction of such work must
be left to the teacher. But its importance both because
of its instructiveness and its interest is great. Pupils
should not only be incited to make individual observations
whenever and wherever they can, but the teacher should
make little field-excursions with the class or with parts of
it at various times, to ponds or streams or woods, and
“show ‘things’ to all. “The life=instom; samme teeing
habits of insects, the web-making of spiders, the flight,
songs, nesting, and care of young of birds, the haunts of
fishes, the development of frogs, toads, and salamanders,
the home-building and feeding-habits of squirrels, mice,
and other familiar mammals are all (as has been called
attention to at proper places in the book) specially fit
subjects for field-observation.

Each pupil should keep a field note-book, recording
from day to day, under exact date, any observations he
may make. Let the most trivial things be meted; when
referred to later in connection with other notes they may
not seem so trivial. The field note-book should be
smaller than the laboratory note- and drawing-book,
small enough to be carried in the pocket. Notes should
be made on the spot of observation; do not wait to get
home. . Sketches, even rough ones, may je advaita—
geously put into the book. Students with photographic
Cameras can do some very interesting and valuable field-
work in making photographs of animals, their nests and
favorite haunts. Such photographic work is very effectively
used now in the illustration of books about animals and

EPOLIPMENT AND NOTES: OF PUPILS 449

plants (see the reproductions of photographs in this book).
If the class is making a collection the collecting notes or
data made in the field-books of the different pupil collec-
tors should all be transferred to a common ‘‘ Notes on
Collections ’’’ book kept by the whole class.

APPENDIXea
LABORATORY EQUIPMENT AND METHODS

Equipment of laboratory. —The equipment of the
laboratory or classroom will, of necessity, depend upon the
opportunities afforded the teacher by the school officers to
provide such facilities as instruments, books, and charts.
If dissections are to be seriously and properly made,
however, some equipment is indispensable. Flat-topped
tables, not over 30 inches high, a few compound micro-
scopes (one is much better than none), as many simple
lenses, or, far better, simple dissecting-microscopes, as
there are students, dissecting-dishes, a pair of bone-
clippers, one injecting-syringe, a bunch of bristles, water,
a few simple reagents and some inexpensive glassware,
as slides, cover-glasses, watch-crystals, and fruit- or
battery-jars for live cages and aquaria, make up a suffi-
cient equipment for good work. Much can be done with
less, and perhaps a little more with some additional
facilities.

The dissecting-pans should be of galvanized iron or tin,
obloiig;. about 6 x-8 inches by 2 imehesPa@cen siti
slightly flaring sides. If an iron wire be run around the
margin, andthe margin bent back oyveqeieeaee willl
strengthen the dish, and make a broader and smoother
edge for the hands to rest on. Diagonally across the
dish, about one-fourth inch from the bottom, should run a
thick wire. A layer of paraffin one-half inch thick

450

LABORATORY EQUIPMENT AND METHODS 451

should cover the bottom. It should be poured in melted,
when the diagonal wire will be imbedded in it and will
hold it in place. Acids must not be put into the pan.

The reagents necessary are alcohol of 95 per cent and
85 per cent, and formalin of 4 per cent (the formaldehyde
sold by druggists is 40 per cent und should be diluted ten
times with water), these for preserving material for dis-
section; chloroform for killing specimens; glycerin for
making temporary microscopic mounts, and 20 per cent
nitric acid for preparing specimens for study of the nervous
systems In addition there will be needed the few other
materials mentioned in the following paragraphs as neces-
sary in the preparation of injecting-fluids, the staining of
fresh tissue and preserving by special methods.

A list of reference books desirable in the laboratory is
appended as a separate paragraph (see p. 454).

Collecting and preparing material for use in the
laboratory.—As directions have been given in the ‘‘ tech-
nical notes ’’ scattered through the book for the collecting
and preparing of all the various kinds of animals chosen
as subjects of the laboratory exercises, it will only be
necessary to give here directions for making certain
special mixtures and for the special preparation of speci-
mens by injection, etc. Specimens to be used for dissec-
tion should be kept in alcohol of 85 per cent or in formalin
of 4 per cent. Alcohol is better for the earthworm, but
for the other examples formalin is either better or as good,
and as it is much cheaper it may well be chosen for the
general preservative.

Methyl green, a.stain used for coloring fresh tissues.
Dissolve the methyl green powder in water, using about
as much powder as the- water will take up. Add a few
drops of acetic acid.

Liyjecting-masses.-—Injecticns are best made with prep-
arations of French gelatine, but white glue will answer

452 APPENDIX II

most purposes. [or fine injection use a combination of
the following: 1! part of a solution of gelatine, I part to
4 parts of water; I part of a saturated solution of lead
acetate in water, and I part of a saturated solution of
potassium bichromate in water. A mixture of these when
hot gives a beautiful yellow injection-mass which, filtered,
will pass through the finest capillaries. For different
colorings use dry paints, which come in ultramarine blue,
vermilion, and green. The gelatine should be thoroughly
soaked before the coloring-matter is added. A mistake
is generally made in using the injection-mass too thick.
One part by weight of gelatine to six or even more parts
of water is a good proportion. The gelatine as well as
elue-masses should be made in a water-bath, which con-
sists of one dish placed within another outer one contain-
ing warm water. [he mass should be injected warm, zof
hot, after which the injected specimen is to be placed in
cold water until the injecting-mass has set. Glue (the
ordinary white kind) can be used for most injections just
as the gelatine was used, but should not be so much
diluted. All injection-masses should be filtered through
a cloth before using.

Preparing skeletons—In general, skeletons are best
cleaned by boiling. After most of the flesh has been cut
away the skeleton should be boiled in a soap solution
until the remaining parts of the muscles are thoroughly
softened. The soap solution is made of 2,000 c.c. of
water, preferably distilled, 12 grams of s Itpetre, and 75
grams of hard soap (white). Heat the. until dissolved,
then add 150 c.c. of strong ammonia. Jhis stock solu-
tion is mixed with four or five parts of water, when the
mixture is ready for use. The-bones after boiling are
rinsed in cold water, brushed and picked clean, then left
to dry on a clean surface. |

Preserving anatomical preparations

Many specimens

LABORATORY EQUIPMENT AND METHODS 453

worth keeping will be found, and for them a solution
known as Fischer’s formulais suggested as good, especially
for brains. Fischer’s formula is made up as follows:
Beee ee. of water, 50 c.c. of formalin, 100 grams of
sodium chloride, and 15 grams of zinc chloride. These
are mixed together until thoroughly dissolved. Open
preparations well before placing them in the liquid and
use about twenty times the volume of the object to be
preserved.

lo keep fresh adissections.—For materials which are
dissected fresh and must be kept over for several days in
a fresh condition add a few drops of carbolic acid to the
water which covers them. Carbolized water (2 per cent
in water) will preserve a great many tissues for a long
time. Hearts will remain for years in a supple condition
in this solution.

Obtaining marine antmals, microscopic preparations,
etc. —For schools not on the seashore the marine animals
such as starfishes, etc., which are to be dissected or
examined as examples of the branches to which they
belong must be obtained as preserved specimens from
dealers in such supplies. Among such dealers on the
Atlantic coast are the Marine Biological Laboratory,
i oecee troll Wiass.; F. W. Walmsley, Academy of
Mati ociemees, Philadelphia, Pa.; and H.'H. and_€. S.
Primley, Iwaleieh, N. C.; on the Pacific coast the Supply
Department, Hopkins Seaside Laboratory, Stanford Uni-
versity, California. Ward’s Natural Science Establish-
ment, Rochester, N. Y., supplies almost any biological
specimens asked for. This establishment furnishes already
made dissections and sets illustrating life-history and
metamcrphosis. The few permanent microscopic prepara-
tions which are mentioned in the book as desirable to have
can be made by the teacher if he has had any training in
microscopical technic. If not, they may be _ bought

454 ee a 2 APPEND CGE

cheaply of such dealers in natural history supplies as the
Bausch & Lomb Optical Co., Rochester, N. Y.; the
Kny-Scheerer Co.,-:17 Park” Place; New) eee ity:
Queen: & Co:, 1010 Chestnut Street, Philadelpria, = Pa_,
and numerous others. From these dealers also can be.
bought all of the laboratory supplies, such as lenses,
slides, cover-glasses, dissecting-scalpels, scissors and
needles, etc., mentioned in this book.

Reference books.—Vhroughout the preceding chapters
exact references have been made to various books, as
many of which as possible should be in the school-library.
Some of these references have been made with special
regard to the teacher, but most with special regard to the
pupil. - All of the books referred 40 are7ineladed an the.
following list. For the convenience of the prospective
buyer, the names of the publishers and prices of the books
are. appended.’ In~- buying . books, it isiar sommes not
necessary to order from the various publishers. A list of
the books desired may be handed to any book-dealer, who
will order them and who should in most cases be able to
get them for a little less than publisher's list prices.

Baskett, J. N. The Story of the Birds. 1899, D. Appleton & Co. $0.65.

Beddard, Frank. Animal Coloration. 1892, Macmillan Co. $3.50.

— Zoogeography. 1895, Macmillan Co. $1.€0.

Bendire, Chas. Directions for Collecting, Preparing, and Preserving Birds’
Eggs and Nests. Distributed by U. S. National Museum.

Bird Lore, an Illustrated Journal about Birds. Macmillan Co. $1.00 a
year.

Cambridge Natural History, Vols. V (Peripatus), $4.00, VI (Insects),
$3.50. Macmillan Co.

Chapman, Frank. Handbook of the Birds of Eastern North America.
1899. D. Appleton & Co. $3.00.

Comstock, J. H. Manual for the Study of Insects. 1897, Comstock Pub-
lishing Co. $3.75.

—— Insect Life. 1901, D. Appleton & Co. $1.50.

—— and Kellogg, V. L. Elements of Insect Anatomy, 1901, Comstock
Publishing Co. $1.00.

LABORATORY EQUIPMENT AND METHODS 45%

Cooke, W. W. Bird Migration in the Mississippi Valley, Distributed by
the Division of Biological Survey, U. 8. Dept. Agric.

Cowan, T. W. Natural History of the Honey-bee. 1890, London: Houls.
ton, Is. 6d. i

Coues, Elliott. Key to North American Birds. 1890, Estes and Lauriat.
$7.50.

Darwin, Chas. The Formation of Vegetable Mold through the action of

Worms. D. Appleton & Co. $1.50.

Origin of Species. 1896, Caldwell. $0.75.

— The Structure and Distribution of Coral Reefs. D. Appleton & Co.
$2.00.

—— Plants and Animals under Domestication. D. Appleton & Co.

Davie, Oliver. Methods in the Art of Taxidermy. 1894, Oliver Davie &
Co., Columbus, O. $10 net. ,

Gage, S.H. Life History of the Toad. Teacher's Leaflets No. 9, April,
1898, prepared by College of Agriculture, Cornell University, Ithaca,
ee

Heilprin, A. The Distribution of Animals. 1886, D. Appieton & Co.
$2.00.

Hodge, C.F. The Common Toad. Nature Study Leaflet, Biology Series
No. 1, 1898, published by C. H. Hodge, Worcester, Mass.

Holland, W. J. The Butterfly Book. 1899, Doubleday and McClure Co.
$3.00.

Hornaday, W. T. Taxidermy and Zoological Collecting, 1897, Chas.
Scribner’s Sons. $2.50 net.

Howell, W. H. Dissection of the Dog. 1889, Henry Holt & Co. $1.00.

Huxley, T. H. The Crayfish: an introduction to the Study of Zoology.
DB Appleton «x Co: . $1.75.

Jordan, D. S. Manual of Vertebrate Animals of the Northern United
Biates,ouscd, 18990, A.C. McClure & Co... $2.50.

-——— and Evermann, B. W. Fishes of North and Middle America, 4 vols.
1898-1900, Distributed by U. S. National Museum.

—— and Kellogg, V. L. Animal Life. 1Igo0, D. Appleton & Co. $1.20.

_ Lubbock, John. Ants, Bees, and Wasps. 1882. D. Appleton & Co. $2.00.

Marshall, H. M., and Hurst, C. H. Practical Biology, 5th ed. G. P. Put-
nam’s Sons. $3.50.

Martin, H. W., and Moale, W. A. Handbook of Vertebrate Dissection, 3
parts. 1881, Macmillan Co.

Part 1. How to dissect a Chelonian (red-bellied slider terrapin);
Part 2. How to dissect a bird (pigeon);
Part 3. How to dissect a rodent (rat).

“McCook, Henry. American Spiders and their Spinning Work, 3 vols.
1889-1893, H.C. McCook, Phila., Pa. $30.00.

Miall, L.C. The Natural History of Aquatic Insects. 1895, Macmillan
Co. $1.75.

456 — APPENDIX II

Parker, T. J. A Course of Instruction in Zootomy, 1884, Macmillan Co.
$2.25. :

—— Lessons in Elementary Biology. 1897, Macmillan Co. $2.65.

—— and Haswell, W. A. Textbook of Zoology, 2 vols. 1897, Macmillan
Co. $9.00.

Peckham, George W. and E. J. Onthe Instincts and Habits of the Solitary
Wasps. 1898, sold by Des Forges & Co., Milwaukee, Wis. $2.00.

Potts, E. Fresh-water Sponges. 1887, Phil. Acad. of Sciences.

Poulton, E. B. The Colors of Animals. 1890, D. Appleton & Co. $1.75.

Reighard, J. E., and Jennings, H. S. The Anatomy of the Cat. 1901,
Henry Holt & Co. $4.00.

Ridgway, R. Directions for Collecting Birds. Distributed by U. S.
National Museum.

Riverside Natural History, 6 vols. Houghton, Mifflin & Co. $30.00.

Romanes, Geo. Darwin and After Darwin, I. 1895-97, Open Court Pub-
lishing Co.

Scudder, S.H. The Life of a Butterfly. 1893, Henry Holt & Co. $1.00.

Van Beneden, E. Animal Parasites and Messmates. 1876, D. Appleton
& Co. ,Gi-50.

Wallace, A. R. The Geographical Distribution of Animals. 1876, Harper
& Bros... $4@.eo.

Wallace, A.R. Island Life. 1881, Harper & Bros. $4.00,

APPENDIX Ill

ReAKING ANIMALS AND MAKING COLLEC-
TIONS

MucH good work in observing the behavior and life-
history of some kinds of animals can be done by keeping
them alive in the schoolroom under conditions simulating
those to which they are exposed in nature. The growth
and development of frogs and toads from egg to adult, as
well as their feeding habits and general behavior, can all
be observed in the schoolroom as explained in Chapter
XII. Harmless snakes are easily kept in glass-covered
boxes; snails and slugs are contented dwellers indoors;
certain fish live well in small aquaria, and many other
familiar forms can be kept alive under observation for a
longer or shorter time. But from the ease with which
they are obtained and cared for, the inexpensiveness of
their live-cages, and the interesting character of their life-
history and general habits, insects are, of all animals, the
ones which specially commend themselves for the school-
room menagerie. In the technical notes in the chapter
(XXI) devoted to insects are numerous suggestions re-
carding the obtaining and care of certain kinds of insects
which may be reared and studied to advantage in the
schoolroom. In the following paragraphs are given direc-
ions for making the necessary live-cages and aquaria for
these insects. !

Live-cages and aquaria.—Prof. J. H. Comstock has
so well described the making of simple and inexpensive

457

458 APPENDIX III

cages and aquaria in his book, ‘Insect Life,’’ that, with
his permission, his account is quoted here.
Live-cages.—‘‘ A good home-made cage can be built
by fitting a pane of glass into one side of an empty soap-
box. <A board, three or
four inches wide, should
be fastened below the
glass so as to admit of a
layer of soil being placed
in the lower part of the
cage, and the glass can

"iv

crn Ful iH
aot repay gy tl \
MET ul i

H
be made to slide, so as to
serve asa door (fig. 166).
cs lt: The glass should fit close-
Fic. 166.—Soap- be ARrecaine cage ar ly when shut, to prevent

insects. (From Jenkins and Kellogg. ) :
the escape of the insects.

“In rearing caterpillars and other leaf-eating larve,
branches of the food-plant should be stuck into bottles or
cans which are filled with sand saturated with Water.’ : By
keeping the sand wet the plants can be kept fresh longer
than in.water alone, and the danger of the larve being
drowned is avoided by the use of sand. |

‘¢Many larve when full-grown enter the ground to
pass the pupal state; on this account a layer of loose soil
should be kept in the bottom of a breeding-cage. ‘This
soil should not be allowed to become dry, neither should
it be soaked with water. If the soil is too dry the pupe
will not mature, or if they do so the wings will not expand
fully; if the soil is too damp the pupz are liable to be
drowned or to be killed by mold.

‘It is often necessary to keep pupz over winter, for a
large proportion of insects pass the winter in the pupal
state. Hibernating pupae may. be left in the breeding-
cages or removed and packed in moss in small boxes.
Great care should be taken to keep moist the soil in the

REARING ANIMALS AND MAKING COLLECTIONS — 459

breeding-cages, or the moss if that be used. The cages
or boxes containing the pupz should be stored in a cool
cellar, or in an unheated room, or in a large box placed
out of doors where the sun cannot strike it. Low tem-
perature is not so much to be
feared as great and frequent
changes of temperature.

‘‘ Hibernating pupz can be
kept ina warm room if care be
taken to keep them moist, but
under such treatment the mature
Mmiscets ate apt to. emerge in
midwinter.

‘«An excellent breeding-cage
ig) fepresented by fig. 167. It
is made by combining a flower-
pot and a lantern-globe. When
practicable, the food-plant of
the insects to be bred is planted jer ern y,

: : Fic. 167. — Lamp-chimney and
in the flower-pot; in other cases flower-pot breeding-cage for
a bottle or tin can filled with Kellove ) Pron Jenkins oud
wet sand is sunk into the soil

in the flower-pot, and the stems of the plant are stuck into
this wet sand. The top of the lantern-globe is covered
with Swiss muslin. These breeding-cages are inexpen-
sive, and especially so when the pots and globes are
bought in considerable quantities. A modification of this
style of breeding-cage that is used by the writer differs
only in that large glass cylinders take the place of the
lantern-globes. These cylinders were made especially
for us by a manufacturer of glass, and cost from six to
eight dollars per dozen, according to size, when made in
lots of fifty.

‘When the transformation of small insects or of a small
number of larger ones are to be studied, a convenient

460 APPENDIX. IIl

cage can be made by combining a large lamp-chimney
with a small flower-pot.

‘( The root-cage.—Yor the study of insects that infest
the roots of plants, the writer has devised a special form
of breeding-cage known as the root-cage. In its simplest
form this cage consists of a frame holding two plates of
glass in a vertical position and only a short distance apart-
The space between the plates of glass is filled with soil in
which seeds are planted or small plants set. The width
of the space between the plates of glass depends on the
width of two strips of wood placed between them, one at
each end, and should be only wide enough to allow the
insects under observation to move freely through the soil.
If it is too wide the insects will be able to conceal them-_
selves. Immediately outside of each glass there is a piece
of blackened zinc which slips into grooves in the ends of ©
the cage, and which can be easily removed when it is
desired to observe the insects in the soil.

‘(A gquaria.—For the breeding of aquatic insects aquaria
are needed. «As the ordinary rectangular aquaria are
expensive and are liable to leak we use glass vessels
instead.

‘«Small aquaria can be made of jelly-tumblers, glass
finger-bowls, and glass fruit-cans, and larger aquaria can
pe obtained of dealers. A good substitute for these is
what is known as a battery-jar (fg. 168). There are
several sizes of these, which can be Obtained of most
dealers in scientific apparatus.

‘Fo prepare an -aquartum, place inthe jar layer of
sand; plant some water-plants in this sand, cover the sand
with a layer of gravel or small stones, and then add the
required amount of water carefully, so as not to disturb
the plants-or to roil the water unduly.) The erowime
plants will keep the water in good condition for aquatic
animal life, and render changing of the water unnecessary,

REARING ANIMALS AND MAKING COLLECTIONS 461

if the animals in it live naturally in quiet water. Among
the more available plants for use in aquaria are the fol-
lowing:

‘¢Waterweed, Alodea canadensis.

‘‘«Bladderwort, U¢ricularia (several species).

‘“Water-starwort, Cadlitriche (several species).

‘Watercress, Vasturtium officinale.

‘“Stoneworts, Chara and Nitella (several species of
cach).

“«Frog-spittle or water-silk, Spzrogyra.

‘CA small quantity of duckweed, Lemna, placed on the
surface of the water adds to the beauty of an aquarium.

— mye
IN Gi |

WUE

Y

(From Jenkins and Kellogg.)

=~

Fic. 168.—Battery-jar aquarium. |

‘““When it is necessary to add water to an aquarium on
account of loss by evaporation, rain water should be used
to prevent an undue accumulation of the mineral-water
held in solution in other water.’’

Making collections.— Much is to be learned about
animals by ‘‘collecting’’ them. But the collecting

462 APPENDIX Ill

should be done chiefly with the idea of learning about the
animals rather than with the notion of getting as many
specimens as possible. To collect, it is necessary to find
the animals alive; one learns thus their haunts, their local
distribution, and something of their habits, while by con-
tinued work one comes to know how many and what
different kinds or species of each group being collected
occur in the region collected over. Collecting requires
the sacrifice of life, however, and this will always be kept
well in mind by the humane teacher and pupil.. Where
one set of specimens will do, no more should be collected.
The author believes that high-school work in this line
should be almost exclusively limited to the building up
of a common school collection. Let a single set of speci-
mens be brought together by the combined efforts of all
the members of the class, and let it be well housed and
cared for permanently. Each succeeding class will add
to it; it may come in time to be a really representative
exhibition of the local fauna. |

The high-school collection should include not only
adult specimens of the various kinds of animals, forming
a systematic collection, as it is called, but also all kinds
of specimens which illustrate the structure and habits of
the animals in question and which will constitute a
so-called biological collection. Specimens of the eggs
and all immature stages; dissections preserved in alcohol
or formalin showing the external and internal anatomy ;
nests, cocoons, and all specimens showing the work and
industries of the various animals; in short, any specimen
of the animal itself in embryonic or postembryonic con-
dition, or any parts of the animal, or anything illustrating
what the animal does or how it lives, all these should be
collected as assiduously as the adult individuals. Each
specimen in the collection should be labelled with the
name of the animal, the date, and locality, and the name

REARING ANIMALS AND MAKING COLLECTIONS 463

of the collector, with any particular information which
will make it more instructive. If such special data are
too voluminous for a label, they should be written in a
general note-book called ‘‘ Notes on Collections’ (kept
in the schoolroom with the collection), the specimen and
corresponding data being given a common number so that
their association may be recognized. In the following
paragraphs are given brief directions for catching, pinning
up, and caring for insects,
for making skins of birds
and mammals, and for
the alcoholic preservation
of other kinds of animals.

Insects. —For catching
insects there are needed
a net, a killing-bottle, a
few small vials of alcohol,
and a few small boxes to
carry home live speci-
mens, cocoons, galls, etc.
For preparing and _ pre-
serving the insects there
are needed insect-pins,
cork- or pith-lined drawers

‘a
Rants PO iat

wr s= =;

SSS Sens
Ses eee =

: Fic. 169.—Insect killing-bottle; cyanide
or boxes, and small wide- of potassium at bottom, covered with

mouthed bottles of alco- plaster of Paris. (From Jenkins and
Kellogg.)
hol.

The net, about 2 feet deep, tapering and rounded at
its lower end, is made of cheesecloth or bobinet (not
mosquito-netting, which is too frail), attached to a ring, one
foot in diameter, of No. 3 galvanized iron wire, which in
turn is fitted into a light wooden or cane handle about
three and a half feet long.

The killing-bottle (fig. 169) is prepared by putting a few
small lumps (about a teaspoonful) of cyanide of potassium

464 APPENDIX III

into the bottom of a wide-mouthed bottle holding about
four ounces, and covering this cyanide with wet plaster of
Paris. When the plaster sets it will hold the cyanide in
place, and allow the fumes given off by its gradual
volatilization to fill the bottle. Insects dropped into
it will be killed in from two or three to ten minutes.
Keep a little tissue paper in the bottle to soak up moisture
and to prevent the specimens from rubbing. Also keep
the bottle well corked. Label it “Poison and aoe: not
breathe the fumes (hydrocyanic gas). Insects may be left
in it over night without injury to them.

Butterflies or dragon-flies too large to drop into the
killing-bottle may be killed by dropping a little chloro-
form or benzine on a piece of cotton; to berplaced in a
tight box with them. Larve (caterpillars, stubs, etc: )~
and pupz (chrysalids) should be dropped into the vials of
alcohol.

In collecting, visit flowers, sweep the net back and
forth over the small flowers and grasses of meadows and
pastures, look under stones, break up old logs and stumps,
poke about decaying matter, jar and shake small trees
and shrubs, and visit ponds and streams. Many insects
can be collected in summer at night about electric lights,
or a lamp by an open window.

When the insects are brought home or to the school-
room they must be ‘‘ pinned up.’’ Buy insect-pins, long,
slender, small-headed, sharp-pointed pins, of a dealer in
naturalists’ supplies (see p. 453). _ These (pitegeest ten
cents a hundred. Order Klaeger pins, No. 3, or Carls-
baeder pins, No. 5. These are the most usemlisizes:
For larger pins order Klaeger No. 5 (Carlsbaeder No. 8);
for smaller order Klaéger No. 1 (Carlsbacdem tio 32)
Pin each insect straight down through the thorax (fig. 170)
(except beetles, which pin through the right wing-cover
near the middle of the body). On each pin below the

REARING ANIMALS AND MAKING COLLECTIONS — 465

insect place a small label with date and locality of capture.
Insects too small to be pinned may be gummed on to
small slips of cardboard, which should be then pinned up.
Keep the insects in drawers or boxes lined on the bottom
with a thin layer of cork, or pith of some kind. (Corn-
pith can be used; also in the West, the pith of the flower-
ing stalk of the century plant.) The cheapest insect-
boxes and very good ones, too, are cigar-boxes. But

ee

>

Pe. 170. —Insect properly ‘‘ pinned up.’ (From Jenkins and Kellogg.)

unless well looked after they let in tiny live insects which
feed on the dead specimens. Fora permanent collection,
therefore, it will be necessary to have made some tight
boxes or drawers. Glass-topped ones are best, so that
the specimens may be examined without opening them.
A ‘‘moth-ball’’ (naphthaline) fastened in one corner of
the box will help keep out the marauding insects.
Butterflies, dragon-flies, and other larger and beautiful-
winged insects should be ‘‘spread,’’ that is, should be
allowed to dry with wings expanded. To do this spread-
ing- or setting-boards (figs. 171 and 172) are necessary.
Such a board consists of two strips of wood fastened a short
_ distance apart so as to leave between them a groove for
the body of the insect, and upon which the wings are held
in position until the insect is dry. A narrow strip of pith
or cork should be fastened to the lower side of the two

466 APPENDIX III

strips of wood, closing the groove below. Into this cork
is thrust the pin on which the insect is mounted. An-
other strip of wood is fastened to the lower sides of the
cleats to which the two strips are nailed. This serves
as a bottom and protects
a | the points of the pins which

Nite ZS} project through the piece of
I MM i] cork. The wings are held
down, after having been out-
spread with the hinder mar-
gins of the fore wings about
at right angles to the body,
by strips. of paper pinned
down over them.

‘« Soft specimens ’’ such as
insect larvz, myriapods, and
spiders should be preserved
in bottles of alcohol (85 per
cent). Nests, galls, stems,
and leaves partly eaten by
insects, and other dry speci-
mens can be kept in small
pasteboard boxes. |

For a good and full ac-
count of insect-collecting and

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ENG 7417 1c Setting -boak@ with putteh) =. ee
flies properly ‘‘spread.” (After Lite, pPp- 284=3 FA.
Eomstonc) Birds, — Ya “eollecting
birds, shooting is chiefly to be relied on. Use dust-shot
(the smallest shot made) in small loads. For shooting
small birds it is extremely desirable to have an auxiliary

barrel of much smaller bore than the usual shotgun which
can be fitted into one of the regular gun-barrels. In such

REARING ANIMALS AND MAKING COLLECTIONS 467

an auxiliary barrel use 32-calibre shells loaded with dust-
shot instead of bullets. Plug up the throat and vent of
shot birds with cotton, and thrust each bird head down-
ward into a cornucopia of paper. This will keep the
feathers unsoiled and smooth.

Birds should be skinned soon after bringing home, after
they have become relaxed, but before evidences of decom-
position are manifest. The tools and materials necessary
to make skins are scalpel, strong sharp-pointed scissors,

ZN SZ
SS
—_ — _—— -

Zijddddddddddsdddsstttt

Fic. 172.—Setting-board in cross-section to show construction. (After
Comstock. )

bone-cutters, forceps, corn-meal, a mixture of two parts
white arsenic and one part powdered alum, cotton, and
metric-system measure. Before skinning, the bird should
be measured. With a metric-system measure carefully
take the alar extent, i.e. spread from tip to tip of out-
stretched wings; length of wing, i.e. length from wrist-
joint to tip; length of bill in straight line from base (on
fersal aspect) to tip; oe of tarsus, and length of
middle toe and claw.

To skin the bird, cut from anus to point of breast-bone
through the skin only. Work skin away on each side to
legs ; push each leg up, cut off at knee-joint, skin down
to next joint, remove all flesh from bone, and pull leg
back into place; loosen skin at base of tail, cut through
vertebral column at last joint, being careful not to cut

468 APPENDIX III

through bases of tail-feathers; work skin forward, turning
it inside out, loosening it carefully all around, without
stretching, to wings; cut off wings at elbow-yjoint, skin
down to next joint and remove flesh from wing-bones;
push skin forward to base of skull, and if skull is not too
large (it is in ducks, woodpeckers, and some other birds),
on over it to ears and eyes; be very careful in loosening
the membrane of ears and in cutting nictitating membrane
of eyes; do not cut into eyeball; remove eyeballs without
breaking; cut off base of skull, and scoop out brain;
remove flesh from skull, and ‘‘ poison ’’ the skin by dust-
ing it thoroughly with the powdered arsenic and alum
mixture. Turn skin right side out, and clean off fresh
blood-stains by soaking them up with corn-meal; wash
off dried blood with water, and dry with corn-meal.
Corn-meal may be used during skinning to soak up blood
and grease.

There remains to stuff the skin. Fill orbits of eyes with
cotton (this can be advantageously done before skin is
reversed); thrust into neck a moderately compact, elastic,
smooth roll of cotton about thickness of the natural neck;
make a loose oval ball of size and general shape of bird’s
body and put into body-cavity with anterior end under
the posterior end of neck-roll; pull two edges of abdominal
incision together over the cotton, fasten, if necessary,
with a single stitch of thread, smooth feathers, fold wings
in natural position, wrap skin, not tightly, in thin sheet
of cotton (opportunity for delicate handling here) and put
away in a drawer or box to dry. Before putting away tie
label to leg, giving date and locality of capture, sex and
measurements of bird, and name of collector. Before
bird is put into permanent collection it should be labelled
with its common and scientific name. |

The mounting of birds in lifelike shape and attitude is
hard to do successfully; and a collection of mounted birds

REARING ANIMALS AND MAKING COLLECTIONS 469

demands much more room and more expensive cabinets
than one of skins. For instructions for the mounting of
birds see Davie’s ‘‘ Methods in the Art of Taxidermy,’’
pp. 39-57; or Hornaday’s ‘‘ Taxidermy and Zoological
Collecting.’’ For a more detailed account of making
bird-skins, see also these books, or Ridgway’s ‘‘ Direc-
tions for Collecting Birds.’’

In collecting birds’ nests cut off the branch or branches
on which the nest is placed a few inches above and below
the nest, leaving it in its natural position. Ground-nests
should have the section of the sod on which they are
placed taken up and preserved with them. If the inner
lining of the nest consists of feathers or fur put in a
‘¢moth-ball ’’ (naphthaline).

To preserve birds’ eggs they should be emptied through
a single small hole on one side by blowing. Prick a
hole with a needle and enlarge with an egg-drill (obtain
of dealers in naturalists’ supplies, see p. 453.) Blow with
a simple bent blowpipe with point smaller than the hole.
After removing contents clean by blowing in a little
water, and blowing it out again. After cleaning, place
the egg, hole downward, on a layer of corn-meal to dry.
Label each egg by writing on it near the hole a number.
Use a soft pencil for writing. This number should refer
to arecord (book) under similar number, or to an ‘‘ egg-
blank,’’ containing the following data: name of bird,
number of eggs in set, date and locality, name of col-
lector, and any special information about the eggs or nest
which the collector may think advisable. The eggs may
be kept in drawers or boxes lined with cotton, and di-
vided into little compartments.

For detailed directions for collecting and preserving
birds’ eggs and nests, see Bendire’s ‘‘ Directions for Col-
lecting, Preparing, and Preserving Birds’ Eggs and

4.790 APPENDIX III

Nests ’’ or Davie’s ‘‘ Methods in the Art of Taxidermy,’’
Pp. 74-78.

* Mammals.—Any mammal intended for a scientific
specimen should be measured in the flesh, before skinning,
and as soon after death as practicable, when the muscles
are still flexible. (This is particularly true of larger
species, such -as foxes, wildcats, “etcs)") ie = mleasure-
ments are taken in millimetres, a rule or steel tape being
used. (1) Total length: stretch the animal on its back
along the rule or tape and measure from the tip of the
nose (head extended as far as possible) to the tip of the
fleshy part of tail (not to end of hairs). (2) Tail: bend
tail at right angles from body backward and place end of
ruler in the angle, holding the tail taut against the ruler. .
Measure only to tip of flesh (make this measurement with
a pair of dividers). (3) Hind foot: place sole of foot flat
on ruler and measure from heel to tip of longest toe-nail
(in certain small mammals it is necessary to use dividers
for accuracy). [he measurements should be entered on
the label, along with such necessary data as sex, locality,
date, and collector’s name.

Skin a mammal as soon after death as possible. Lay
mammal on back and with scissors or scalpel open the
skin along belly from about midway between fore and hind
legs to vent, taking care not to cut muscles of abdomen.
Skin down on either side of the body by working the skin
from flesh with fingers till hind legs appear. Use corn-
meal to stanch blood or moisture. With left hand grasp
a leg and work the knee from without into the opening
just made; cut the bone at the knee, skin leg to heel.and
clean meat off the bone (leaving it attached of course to
foot). In animals larger than squirrels skin down to tips

* The following directions for making skins of mammals were written
for this book by Mr. W. K. Fisher of Stanford University, an experienced
collector.

REARING ANIMALS AND MAKING COLLECTIONS — 471

of toes. Do the same with other leg. Skin around base
of tail till the skin is free all around so that a grip can be
secured on body; then with thumb and forefinger hold the
skin tight at base of tail and slowly pull out the tail. In
small mammals this can be done readily, but in foxes it
is often necessary to split the skin up along the under side
and dissect it off the tail-bones. After the tail is free
ckin down the body, using the fingers (except in large
mammals) till the fore legs are reached; treat the fore legs
ia the same manner as hind legs, thrusting elbow out of
the skin much asa person would do in taking off a coat;
cut bone at elbow; clean fore-arm bone. Skin over neck
to base of ears. With scalpel cut through ears close to
skull. With scalpel dissect off skin over the head (taking
care not to injure eyelids) down to tip of nose, severing
its cartilage and hence freeing skin from body. Sew
mouth by passing needle through under lip and then across
through two sides of the upper lip; draw taut and tie
thread. Poison skin thoroughly. Turn skin right side
out. Next sever the skull carefully from body, just where
the last neck-vertebra joins the back of the skull. It is
necessary to keep the skull, because characters of bone and
teeth are much used in classification. Remove superfluous
meat from the skull and take out brain with a little spoon
made of a piece of wire with loop at end. Tag the skull
with a number corresponding to that on skin, and hang
up to dry. A finished specimen skull is made by boiling
it a short time and picking the meat off with forceps,
further cleaning it with an old tooth-brush, when it is
placed in the sun to bleach. Care must be taken always
not to injure bones or dislodge teeth.

Mammals are stuffed with cotton or tow; the latter is
used in species from a gray squirrel up. Large mammals
stuffed with cotton do not dry readily, and often spoil.
Being much thicker-skinned than birds, mammals require

472 APPENDIX III

more care in drying and ordinarily require a much longer
period. Soft hay may be substituted for tow; never use
feathers or hair. Roll a longish wad of cotton about the
size of body and insert with forceps, taking care to form
the head nearly as in life. Split the back end of the cot-
ton and stuff each hind leg with the two branches thus
formed. oll a piece of cotton around end of forceps
and stuff fore legs. Place a stout straight piece of wire
in the tail, wrapping it slightly to give the tail the plump
appearance of life. (If the cotton cannot be reeled on to
the wire evenly, leave it off entirely.) Make the wire
long enough to extend half way up belly. Sew up slit in
belly. Lay mammal on belly and pin out on a board
by legs, with the fore legs close beside head, and hind
legs parallel behind, soles downward. Be sure the label
is tied securely on right hind leg.

For directions for preparing and mounting skeletons of
birds, mammals, and cther vertebrates, see the books of
Davie and Hornaday already referred to.

Fishes, batrachians, reptiles, and other antmals.—The
most convenient and usual way of preserving the other
vertebrates (not birds or mammals) is to put the whole
body into 85 per cent alcohol or 4 per cent formalin.
Batrachians should be kept in alcohol not exceeding 60
per cent strength. Several incisions should always be
made in the body, at least one of which should penetrate
the abdominal cavity. Anatomical preparations are simi-
larly preserved. By keeping the specimens in glass Jars
they may be examined without removal. Fishes should
not be kept in formalin more than a few months, as they
absorb water, swell, and grow fragile.

Of the invertebrates all, except the imsectsyeare pre-
served in alcohol or formalin. The shells of molluscs
can be preserved dry, of course, in drawers or boxes
divided into small compartments.

INDEX

je= \\lustrations are indicated by an asterisk

Acanthia lectularia, *188. ANE. 212, 238,2237

Acarina, 230. Anura, 299.

Acmara spectorum, *248. Ape, 401.

Actinozoa, 97, 102. Aphidiz, 200.

Adaptation, 407. Apis florea, comb ot, *222.
Adder, spreading, 321. Apis mellifica, *218.
fEzialitis vocifera, 349. Appearance, terrifying, 430.
Agalenidz, 235. Aquarium, 457

Avktistrodon piscivorous, 323. Aquarium, Patieae, * 461,
Aix sponsa, 347. | Aguila chrys@tos, 342.
Albatross, 346. | Arachnida, 144. 220.

Alca impennis, 345- | Arctomys monax. 391.

Alce americana, *385, 399. | Ardea herodias, 358.
Alligator, 326. Ardea virescens, 347.
Alligator mitssissippensis, 326. | Argiope sp., *236.
Alternation of generations, 96. Argonaut, 257.

Amblepiites rupestris, 282. A reonauta argo, 257.

Ariolimax califor JILCL 2?

Amblystoma, 297, 208.
| Arthogastra, 230.

Amblystoma maculatum, 299.

Ameiurus, 282. | Arthropoda, 144.
Ameba, *32; structure and life of, | Ascidian, 259, *261.

qt. Aspidiotus aurantiu, *108.
Amphioxus, 278. Asterias sp., structure and life of,
Anaconda, 324. 108.
Anas boschas, 347. | Astertas, -*109 ; . cross-section of,
Anatomy defined, 3. F112.
Anguilla, 284. Asterias ocracia, *{22.
Anguillula, 140. | Asterina mineata, *122.
Anolis principaiis, 319. | Asteroidea, 120, 121.

Anosta plexippus, anatomy of larva | Attidz. 235.
of, 177, external structure of. 171, | Auk, great, 345.
172; life. of. 175; mimicked by | Aves, 327.

Bastlarchia archippus, *433. | Aythya vallisneria, 347.
_Anseres, 347. | Ayu, 283.
Ant, little black, *224; little brown, |

22%. | Back-swimmer, 197. 199.
Antelope, *395, 396. Balanus, *153.
Antenna of carrion beetle. *184. Balena glactalis, 393.

Antilocapra americana, *395. 390.
Antrostomus vociferus, 350.

Balena mysticetus. 393.
Barbadoes earth, 82.

473

Aq4

Barnace, “F853. w55< ‘sessite,) By Se
stalked, 155.

Barn-owl, 353.

Bartramia tongicauda, 349.

Bascantum constrictor, 32%.

Bass, 282:

Bat, hoary, *392.

Batrachia, 291.

Batrachians, 291; body form and
structure of, 292; classification of,
295; life-history and habits of,
295; structure of, 292,

Bat, 391.

Bead-snake, 322.

Bear, 398.

Beaver, 301.

Bed-bug, *188.

Bee, 212 --solitary, 216,

Beetle, great water-scavenger, 163;
external structure, “*a64-. “inter-
nal structure, °*167: ‘antenna of
carrion, *184; Colorado potato,
209.

Beetle, 206; carrion, 209; whirlgig,
200.

Bell-animalcule,
of, 75.

Bills of birds, 362.

Bipinnaria, 119.

Bird, frigate, 346; man-of-war,
346; outline of body showing ex-
ternal regions, *330; ruby-throat
humming, nest and eggs of,
ee

Bird-louse, *194.

Birds, 327: bills and feet of, 362-
body form and structure of, 336;
care of young, 366; classification
of, 340; collecting, 466; determin-
ing, 359; development and life-
history of, 339; feeding habits of,
370; flight and songs of, 364 ;
migration of, 367; molting of, 361;
nesting of, 366; protection of, 370.

Bird-skins, making, 466.

Bison bison, 396, *397.

Bittern, 348.

Blacksnake, 321.

Liissus leucopterius, 198.

Blood, circulation of, in mammal,
5270.4 |

blood of toad, structure of, 40.

Blow-fly, 201, 202; section through
compound eye of, *185.

‘* Bob Jordan” (monkey), “400.

structure and _ life

INDEX

Bobwhite, 350.

Bombus, 210.

Bombyx mort, anatomy of larva of,
Te

Bonasa umbellus, 350.

Books, reference, 454.

Borer, peach-tree, *210.

Botaurus lentiginosus, 348.

Box tortoise, 315. |

Brachynotus nudus, *153.

Brains of vertebrates, *378.

Branch, defined, 73.

Branta canadensis, 347.

Breeding cage, 458, 459.

Brittle-stars, 120; 123, 122:

Bubo virginianus, 353.

Buffalo, 396, *397.

Bufo lentiginosus, 301; dissection
Of sie

Bullfrog, 299.

Bumblebee, 216.

Bunodes californica, 103.

Buteo, 353-

Butterfly, external structure of, 171,
*172; ‘life -of, 175 > anonagreh,
anatomy of larva of, 177; dead
leaf, *429; mimicked by viceroy,
*433-

Butterflies, 205; setting-board for,
*466, 467.

Buzzard, turkey, 352-

Cachalot, 393.

Cage, lamp-chimney and flower-pot
breeding, *459; soap-box breed-
ing, *458.

Cake-urchin, 124.

Calcarea, oI,

Calliphora vomitoria, 202; section
through compound eye of, *185.

Callorhinus alascanus, *399.

Callorhinus wursinus, parasitized,
yy ope

Cambarus sp., dissection of, 18; life
of, 146.

Camphephilus principalis, 355.

Cancer productus, *153.

Canis familiaris, 398.

Canis latrans, 398. |

Canis nubtlus, 308.

Canvas-back, 347.

Carcharcdon, 280.

Caribou, 396.

Cassowary, 343.

Castor canadensis, 391.

INDEX

Caterpillar, apple tent, 208; forest
tent, 209.

Catfish, 282.

Cathartes aura, 352. ;

Cavia, 390.

Cell, defined, 37.

Cell differentiation, degrees of, 54.

Cell products, 38.

Cell wall, 38.

Centiped, *228, 229; skein,

Centipeds, 226.

Centrocercus urophastants, 350.

Centrurus sp., *236.

Cephalpoda, 246.

Cercopithicus, *400,

Cervus canadensis, *394, 395.

Ceryle alcyon, 354.

Cete, 393.

Cetorhinus, 270, 280.

Chetura pelagica, 350.

Chain-snake, 320.

Chalk, 81.

Chameleon, green, 318.

Chelonia, 313, 314.

Chelonia mydas, 315.

Chelydra serpentina, 314.

Chen hyperborea, 247.

Chicken-hawk, 353.

Chimney-swift, 356.

Chinch bug, 198.

Chipmunk, 391.

Chiroptera, 391.

Chitin, 145, 158.

Chlorostomum funebrale, *248.

Chordata, 259; classification of, 260.

Chordetles virginianus, 356.

Chromatophore, 256.

Chub, 282.

Chrysemy's, 314.

Cicada, 199 ; seventeen-year,
septendecim, *200, 197.
Circulation of blood in mammal,

*376.
Circus hudsonius, 352.
Cistudo carolina, 314.
Clams, 246; hard shell, 247; soft-
shell, 247.
Class, defined, 75.
Classification, basis and signification
_ of, 65; defined. 3; example of, 68.
Chstocampa americana, larve, *208.
Chstocampa disstria, caterpillars,
*209; life-history ot, 207.
Clupea harengus, 284.
Cobra-da-capello, 324.

*228.

~200%

’

475

Coccide, 198.

Coccyges, 354.

Coccyzus, 354.

Cock, chapparal, 354.

Cockroach, 192.

Codfish, 284.

Coecilians, 302.

Ceelenterata, 92; classification of,
96; development and_ life-history
of, 95; form of, 93; skeleton ot,
95; structure of, 94.

Colaptes auratus, “355.

Colaptes cafer, 355.

Coleoptera, 2006.

Colinus virginiantus, 350.

Collections, making, 461.

Color, use of, 424.

Colors, warning, 430.

Colubrid.e, 319.

Columba fasctata, 351.

Columba livia, 351.

Columbez, 351.

Colymbus auritus, 343.

Comb-building of honey-bee, *221.

Comb of East Indian honey-bee,
barat

Commensalism, 155, 413.

Communal lite, 411.

Condor, Calitornia, 352.

Conaylura cristata, 391.

Conjugation, 35, 60.

Conoirachelus crategt, *212, 213.

Conotrachelus nenuphar, *214.

Constrictor, boa, 324.

Conurus carolinensis, 353.

Coot, American, 349.

Copperhead, 322.

Coral, 95, branche, , =1o4:
106.

Coral islands, 104, 106.

Coral polyps, 104.

Coral reefs, 106.

Corals, 92, 102, 104.

Coregonus, 283.

Corisa, 197.

Corisa sp., *199.

Cormoyant, 346.

Cornea of eye of horse-fly, *186.

Cottontail, 390.

Coyote, 398.

Crab, 151, 152; soft-shelled, 154.

Crabs, +55 3-

Crane, sand-hill. 348; whooping, 348.

Crayfish, dissection of, 18, *18, 22:
life of, 146.

red,

476

Cricket, house, *193.
Cricket, 192.
Crinoid, *126.
Crinoidea, 121, 125.
Crocodile, 326.
Crocodalea, 313, 325-
Crocodilus americanus, 326.
Crotalus, 222.
Crustacea, 144, __ 146.
structure of, 147.
Cryptobranchus, 2098.
Ctenophora, 97, 107.
Cuckoos, 354.
Cucumaria, 124.
Cucumber-beetles, 209.
Culex .sy)., 2045." 205-
Cureulio plum, *214:
Curculio.quince, +212, 253.
Curlew, long-billed, 350.
Cuttlefishes, 255.
Cyclas, 247.
Cyclophis estivus, 320.
Cyclops, 148, *149.
Cyclostomata, 278.
Cytoplasm, 38.

form and

Dabchick, 343.

Dactylus sp., *249.

Damp bug, *151.

Darters, 282.

Dasyatis, 281.

Decapoda, I51.

Decapods, 256.

Deer, 206:

Degeneration, 417.

Dendrostomium cronjhelmt, *134.

Development, defined, 3; embry-
onic, defined, 62; post-embryonic,
defined, 62; simplest, 59.

Diapheromera femorata, *427.

Diaspis rose, *198,.

Dictynidz, 235.

Didelphis virginiana, 390.

Diemystylus torosus, *299.

Dienystylus viridescens, 297.

Dimorphism, 96.

Diptera, 201.

Distribution, barriers to, 437; geo-
eraphical, 435: laws of, 4306:;
local, of birds, 367; modes of, 437.

Diver, great northern, 343.

Dolphins, 393.

Doris tuberculata, *254.

Draco, 319.

Dragon-flies, 294.

INDEX

| Dryobates uttlosus, 355-

Dragon-fly, *196.
Dragon, flying, 318.
Drawings, 447.
Dryobates pubescens, 355.

Duck, ruddy, 347.
Dyticus sp., 210.
Dytiscidz, 207.

Eagle, bald; 3523 golden. 352.

Ear of locust, *187.

Earthworm, anatomy of, *126; ali-
mentary canal of, *126; cross-
section: off = *3138 2 neproductive
organs of, *130; structure and life
Ob 127.

Earthworms, 136.

Echinoderm, development of, IIg ;
structure of, 1175 Shape of; 116,
Echinodermata, 108; classification

of,< 128.

Lchinodoris sp., *254.

Echinoidea, 25) 222, 423.

E-cit an; 2285;

Ecology, animal, 403.

Lctopistes migratorius, 351.

Eel, 284.
Fit, ereen:
+200)

Eggs of birds, collecting, 469.

Bide, 3247 -

Elasmobranchii, 279.

Ficassoma, 271.

Elk, *394, 396.

Fpeiridz, 236.

Ephemerida, 194.

Lpialtus productus, *153.

Equipment of Jaboratory, 450.

Equipment of pupil, 447.

Lrethizon dorsatus, 391.

Erethizon epixanthus, 391.

Eretmochelys imbricata, 215.

Erismatura rubida, 347.

Eumeces skeltonianus, *316.

Eupomotic gibbosuc, dissection of,
(facing) *263; life of, 270 ; struc-
ture of 263.

Exocetus, 285.

Eye, cornea of compound, of horse-
fly, *186; section through com-
pound, of blow-fly, *185.

Eye of vertebrate, *378.

western brown,

207;

falco sparvertus, 353-
Family, defined, 72.

INDEX

Fauna, 440.

Heather-stars, 121, 125, *126.

Feet of birds, 362.

Felis concolor, 398.

Ferz, 397-

Fever, yellow, and mosquitoes,

Fiber sibethicus, 39%.

Fire-flies, 209.

Jishes, 263; body form and struc-
ture of, 271; classification of, 277;
development and life-history of,
276; habits and adaptations cf,
285.

Fish-hatcheries, 288.

Flat-worms, 137.

Flea, house, *204.

Flickers, 355.

Flies, 201; chalcid, 214; ichneumon,
242.

Flight of birds, 366.

Flying fishes, 285.

Food-fishes, 288.

Food of birds, 370.

Foraminifera, 80.

Fox, 398.

fregata aquila, 340.

Frogs, 299. |

fulica americana, 349.

Fulmars, 345.

Function, defined, 14.

Functions, essential, 15.

Fur-seals, 398, *399.

Fur-seals, parasitized, *422.

205.

Gadus callarias, 284.
Galley-worm, *227.
Gall-flies, 214.

Gallinge, 350.

Gastropoda, 246,

Gavia imver, 347.

Gavial, 326.

Generation, spontaneous, 58.
Genmules, 85.

Genus, defined, 70.
Geococcyx californianus, 354.
Gephyrean, *134.

Girdler, currant stem, *215.
Glass-snake, 317.

Glires, 391.

Goat, Rocky Mt., 397.
Gonionema vertens, *IOl.
Goose, Canada, 347.
Gophers, pocket, 391.
Gordius, 140.

Grantia, *47.

|

|
|

ll

|

477

Grantia sp., 35.
Grayling. 284,
Grebe, horned, 343; pied-billed,
Green, methyl, 351.

Greensnake, 320.

Gregariousness, 419.

Grouse, ruffed, 350.

Grus americana, 348.

Grus mexicana, 348.

Guillemot, 345.

Guinea-pig, 391.

Guinea-worm, I40.

Gull, great black-backed, 345.
Gulls, 345.

Gymnophiona, 302.

Gyrinidz, 206,

Habitat, 441.

Hag-fishes, 270.

Hair-worms, 140.

flalietus leucocephalus, 352.

Flalictus, 216,

Harporhynchus redivivus, *371.

flatterta, 312.

Hawk, marsh, 352.

Helmet shells, 255.

fi. loderma horridum,

Hemiptera, 197.

Hermit-crab, 154, *153.

Herodiones, 347.

Heron, great blue, 348; green, 347.

Herring, 284.

fleteredon platirhinos, 321.

Hippocampus hippocampus, *285.

Holothuroidea, 121, 124.

flomo sapiens, 398.

Poney-pee, . 216 ;- - brood=cells ‘of,
*219:, building comb, *221- comb
or Hast. Indians *222:ccress2sec=
tion of body of pupa of, *Igr,

Honey-bees, 212.

Honey-dew, food of ants, 223.

Hornets, 217.

Horse-fly, cornea of eye of, *186

House-fly, 202.

Humming-birds, 356. :

flydra, *47; structure and life of, 46.

Hydrozoa, 96, 97.

Hydrophilide, 207.

flydrophilus sp., external structure
of, *164; internal structure of,
*167.

Llygrotrechus, 198, *199.

flyla pickeringtt, 300,

eae

478

flyla versicolor, 300.
Hymenoptera, 212.
flyptiotes sp., and web, *238.

Tguana, 318.

Imago, 190,

Injecting-masses, 451.

Insect,- pinned, “465: twig, -*427-
wingless, *181.

Insecta: 257-

Insectivora, 391.

Insects, classification of, I9I; col-
lecting, 463; communal, 215: de-
velopment and life-history of, 188;
form and structure of, 181; killing-
bottle for, *463; social, 215.

Invertebrate, defined, 30.

Islands, coral, 104, 106.

Isopod, *151.

Isopoda, 150.

Jack rabbit, 390.

Fanus integer, *215.
Jellyfish, *1or.

Jellyfishes, 92; colonial, 97.
Joint-snake, 318.

FIVUS F227

Jane-beetle, 212.
June-beetles, 206.

‘allima, *429.
Kangaroo, 389.
Katydids, 192.
Kelp-crab, *152.
Kill-deer, 349.
Killing-bottle for insects, *463.
Kingfisher, belted, 354.

Laboratory, equipment of, 450.

Lachnosterna, 212.

Lady-birds, 209.

Lagopus, 350.

Lake-lamprey, 2709.

Lampetra wildert, 279.

Lamprey, *278; brook, 279.

Lampropeltis bovlit, *321.

Lampropellis getulus, 320.

ikanceler, 278.

Larks, horned, *358.

Larus marinus, 345.

Larva, 189; of Monarch butterfly,
anatomy of, 177; parasitized,
AZO:

Lasiurus borealis, 392.

Lasiurus cinereus, *392.

|

INDEX

Lastus flavus, 223.

Leeches, 136.

Lemurs, 401.

Leucania unipuncta, *211,

Lepidocyrtus americanus, *181,

Lepidoptera, 205.

Leptocardii, 277.

Leptoplana californica, *138.

Lepus campestris, 390.

Lepus nuttali, 390.

Life-history, defined, 62.

Life-processes, essential, 15.

Limicolze, 349.

Limpets, 255, *248.

Littorina scutulata, *248.

Live cages, 457.

Liver of toad, structure of, 41.

Lizard, *309.

Lizards, 316.

Lobster, 151, 152.

Locust, differential, -15@> “eax: of,
*13875 red-legged, “aRoe | “ng7-
Rocky Mt., 156; structure and lite
of, 156; two-striped, 156.

Locusts, 192.

Loligo; 257.

Longipennes, 345.

Loon, 343.

Lumbricus sp., alimentary canal of,
*131; cross-section of, *F32- struc-
ture and liftoff 127)

Lung-fish, 285.

Lycena, scales of wings of, *206.

Lycosidz, 235.

Lynx rufus, 308:

Macrocheira, 154.

Madrepora cervicornis, *105.
Malaclemmys palustris, 314.
Malaria and mosquitoes, 205,
Mallard, 347.

Mammal, circulation of blood in,

Oe
Mammalia, 373.
Mammals, 373; body form and

structure of, 381; classification of,
389; development and life-history
of, 388; habits, instinct and rea-
son of, 388; making skins of,
470.
Man, 3098.
Man-of-war, Portuguese, 98, *97.
Marsupialia, 380.
Martesia xylophaga, *251-
Massasauga, 32.

INDEX

May-flies, 194.

May-fly, nymph of, *197.

Medusa, *I0O1.

Megalobatrachus, 298.

Megascops asio. *352, 353.

Melanerpes erythrocephalus, 355.

Melanerpes formicivorus, 359.

Melanoplus sp., ear of, *187; struc-
ture and life-history of, 157.

Melanoplus vibittatus, 157.

Melanopius differentialis, 157.

Melanoplus femur-rubrum,157,*158.

Melanoplus spretus, 157.

.Meleagrina margaritifera, 250.

Merula migratoria propingua, *368.

Metamorphosis, complete, 171, 188,
189; incomplete, 171, 189.

Metazoa, defined, 43.

Wice,: 308:

Micropterus dolomien, 282.

Micropterus salmoides, 282.

Migration of birds, 367.

Mimicry, 430.

Millipeds, 226.

Mite, cheese, *230.

Mites, 2209.

Modifications of structure and func-
tion, 29.

Moles, 391.

Mollusca, 239.

Molluscs, 239; classification of, 246;
development of, 246; form and
structure of, 245.

Molting, 361; of birds, 361.

Monitor, 318.

Monkey, *400.

Momomertum minutum, *224.

Monster, Gila, *317.

Moose, *385, 396.

Morphology, defined, 3.

Mosquito, 202, *203.

479

Murres, *344. -

Muscles of toad, structure of, 41.
Mus decumanus, 391.

Mus musculus, structure of, 373.
Mus rattius, 391.

| Musk-rat, 391.
. Mussel, fresh-water, life-history and

habits structure of,

239.
Mya arenaria, 247.
Myotis subulatus, 392.
Myriapoda, 144, 2206.
Mytilus californianus, *248,.
Myxine, 279.

ol, - 243;

| Names, scientific, 68.
| Narcobatis, 281.

Natrix stpedon, 320.
Nautilus, 255; pearly, 258.
Nautilus pompilius, 258.
Necturus, 297, 298.
Nemathelminthes, 140.
Neotoma pennsylvanica, 391.
Nereid, +124;

Nereis sp., *134.

| Nesting of birds, 366.

Nestef oriole, *365-
| Lettion carolinense, 347.

Mosquitoes, 201; and malaria, 205 ; |

and yellow fever, 205.

Moth, forest tent-caterpillar, life-
history of, *207.

Moths, 205.

Mourning dove, 351.

Mouse, life-history and habits of,
3479: structure of, 373.

Mud-eel, 297.

Mud-hen, 3409.

Mud-puppies, 297.

Mud-turtle, 313. |

Multiplication of one-celled animals,
59; of many-celled animals, 61.

| One-celled

Night-hawk, 356.
Night-heron, 348.

Nirmus prestans, *194.'
Non-calcarea, 91. ,
Notes, 447, 448.

Notochord, 259.

Notonecta, 197, 199.
Nucleus, 38.

Nudibranchs, 252, *254.
Numenius, longirostris, 350.

| Wyctea nyctea, 353-

Wycticorax, 348.

| Octopi, 255.
_ Octopods, 256.

Odocotleus americanus, 396.

Odonata, 194.

| Oligocheetze, 136.

Olor, 347.

Ommatostrephes californica, *257.
Oncorhynchus tschawtscha, 283.
animals, multiplication

Gi AS Fs

| Ooze, foraminifera, 81 ; radiolaria,

81.
Opheosaurus ventralis, 317.

480

Ophiuroidea, 121, 122.

Opossum, 389.

Order, defined, 72.

Oreaninos montanus, 397.

Orean, denned: 14.

Orthoptera, 192 ; sound-making of,

193.

Orb-web of Epeiridz, 236.
Ostrea virginiana, 248.
Ostriches, 341, *7Ae.
Otocorts alpestris, *358.

Ovis canadensis, *383, 396.

Owl, burrowing, 353; great gray,
353; great horned, 353 ; snowy,
353"

Oyster, 248.
Oyster-crab, 154.
Oyster-drills, 255.
Oysters, 240") seeds.
“spat ’- Ot 240.

of, 240 ;

Pagurus samuelis, *153.

Paludicolz, 348-

Panther, 3098.

Paramecium, “35; multiplication of,
60; structure and life of, 34.

Parasitism, 415.

Paroquet, Carolina, 353.

Parrots, 353.

Passer domesticus, dissection of, (fac-
ing) *327; life-history and habits
Gl, 335 Structure ot, 227.

Passeres, 3157:

Pearl-oyster, *2409.

Pelecanus californicus, 346.

Lelecanus eryvthrorhynchus, 346.

Pelecanus fuscus, 346.

Pelecypoda, 246.

Pelican, brown, 346; white, 346.

LPentacrinus sp., *126.

Pentacta frondosa, *125.

Peripalus ciseni; *220.

ETIMGISD., 7 VO2,

Retrels245,;

Petromyzon marinus, *278.

Lhalacrocorax, 346.

Pheasants, 350.

Phoca vitulina, 2O7e

Pheebe, black, nest and eggs of,
#340.

Pholas sp., *250.

Phrynosoma, 318.

Phylloxera, grape, 198, 201.

Phylloxera vastatrix, 198, 201.

Phylum, defined, 73.

a
S$

INDEX

Phy saliad Spx *O7-

Physeter macrocephatlus, 393-

Physiology, defined, 3.

Pici,’ 354208

Pickerel-frog, 300.

Pigeon, band-tailed, aoe,
351.

Pinnotheres, 154.

Pipe-fish, 285.

Pisces, 263.

Pituophis bellona, *323.

Planaria sp., *138.

Planarian, fresh-water,
rine, *138:

Planarians, 137.

Plant-lice, 197, 200.

Planula, 96.

Platyhelminthes, 137.

Plectrophenax nivalis, *358.

Plethowon, 297.

Plover, field, 340.

Pluteus i109;

Podilymbus podiceps, 343.

Poison-fangs of rattlesnake, *324.

Pollicipes polymenus, *153.

Polymorphism, 96.

Polyne brevisetosa, *134.

Polyps, 92, 97.

Pomoxts annularis, 282.

Pomoxis separoides, 282.

Pond-snails, 252.

Porcupine, 390.

Porcupine-fish, 285.

Porifera, 84.

Porpoises, 393.

Porzana carolina, 349.

Prairie-chicken, 350.

Prawns, 152.

Preparations, preserving anatomical,
Pcie

Primates, 398.

Pristis pectinatis, 281.

Protophyta, 82.

Protoplasm, described, 39.

Protopterus, 288. .

Protozoa, defined, 43,755 form ‘of,
78: marine, Se.

Pseudemys, 313.

Pseudogryphus californianus, 352.

Psittaci, 353.

Ptarmigan, 356.

Puff-adder, 325.

Pufims, 345.

/-ulex trritans, *2C4

Pulmonata, 253.

ee

#938 5° mas,

INDEX

Puma, 398.

Pumpkin seed, life of, 270; structure
of, 263.

Pupa, 189; cruss-section of body cf,
of honey-bee, *Ig1.

Pupation, 189.

Purpura saxicola, *248.

Pygopodes, 343.

Python, 324.

Quail, 350.
Querguedula discors, 347.

Rabbits, 390.

Radiolaria, 80.

Rai!, Carolina, 549.

Raja erinacea, 280, *281.

Raja levis, 281.

Rana catesbiana, 299.

Rana palustris, 300.

Rana sylvatica, 300.

Rangifer caribou, 396.

Raptores, 351.

Ratitze, 341.

Rats, 391.

Rattlesnake poison-fangs, *324.

Rattlesnakes, 321.

Rattles of rattlesnake, *223.

Reefs, coral. 106.

Reindeer, 396.

Remora, *.87.

Remoropsts brachyptera, *287.

Root-cage, 460.

Reptiles, body form and organiza-
tion of, 309; classification of, 312;
life-history of, 312; structure of,
310.

Keptilia, 303.

Resemblance, protective, 326.

Rheas, 343.

Road-runner, 354.

Robber-ant, 225.

Robin, Western, *368.

Rock-bass, 282.

Rock-crab, ¥15 3.

Rock-dove, 351.

Rodents, 390.

Rosalina vartans, *8t.

Rotifer sp.. *143.

Round worms, 140.

Ruminants, 395.

Sacculina, 67, *418.

Sage-hen, 350.

Salamander, red-backed, 297; tiger,
F202,

A8I

Salamanders, 297.
Salmo irideus, *283.
Salmon, king. 284.

| Sand-dollar, 124.

Sand-pipers, 345.

Sanninoidea existiosa, *212.

Sap-sucker, downy, 355; hairy, 355-

Saw-fish, 281.

Sayornis nigricans, nest and eggs
ol, * 340.

Scale insect, red-orange, *1098.

Scale insects, 198.

Scale rose, *108.

Scales of wings of Lyczna, *206;
wing of Monarch butterfly, *174.

Scallops, 246.

Scalops aguaticus, 391.

Scaphtopus, 300.

Sceloporus, 317.

Sciuropterus volans, 391.

Scturus carolinensis, 391.

Sciurus hudsonicus, 391.

Scturus ludovicianus, 391.

Scolopendra sp., 228, 229.

Scorpion, *230.

Scorpions, 229.

Scoltaptex cinera, 353-

screech-owl, *352; 353.

Scutigera forceps, *228.

Scyphozoa, 97, 1or.

Sea anemones, 92, 102, *103.

Sea cucumber, *125.

Sea-cucumbers, 108, 121, 124.

Sea-fan, 107.

Sea-feather, 106.

Sea-horse, *285.

Sea-lamprey, 279.

Sea-lily, 118.

Sea-pen, 106.

Sea-shells, 252.

Sea-slugs, 255.

Sea-snakes, 325.

Sea-squirt, *261.

Sea-turtles, 315.

Sea-urchin, *114; structure of, 113.

Sea-urchins, 108, 121, 123.

Seals, 397.

Selection, artificial, 409 ;
400.

Sembling of insects, 176.

Sepias, 256.

Setting-board for butterflies, *466,
407.

Shark, basking, 270, 280; hammer-
headed, 280; man-eating, 280,

natural,

482

Sharks, 280.
Shearwaters, 345.
Sheep-fluke, 138.
Sheep, Rocky Mt.,
Shipworm, 251.
shoveller, 247.
Shrews, 391.
Siinap, At. 052.
Silk-worm, anatomy of, *178.
Siphonophore, 98.

SURE, 2OGn 2G.

Sistrurus, 322.

Skate, barn-door, 281; common, 280,
een251.

Skates, 280.

Skeleton of coral, 105.

Skeletons, preparing, 452.

Skink: blme-tatled, “307.

Skin of toad, structure of, 40.

#333,,30 Jax

Slipper-animalcule, *35; structure
and life of, 34.

Slug, giant yellow, *252.

Slugs, 252, 253.

snake coral, 321.

Dake; atter, 1 326. lie Ol 207-

SUGUCLULE Ol, 203" /COpNEm. 7222.

Snake king, *321.

snakes, 316.

Snails, 252, 253.

Snapping-turtle, 314.

Silpes. 340.

Snowflakes, *358.

Snow-goose, 347.

Social life, 410.

Somaterta, 347.

Songs of birds, 364.

Sora, 340.

Sound making of orthoptera, 193.

Spadefoot, 300.

Sparrow, English, dissection. of,
@Gacmie) .*327-- liteshustoma and
habits, Of 335: structure o1/327:
western chipping, *360.

Sparrow-hawk, 353.

Spatula clypeata, 347.

Species, defined G0:

Species-extinguishing, 442.

Species-forming, 408, 442.

Speotyto cunicularia, 353.

Sphinx chersis larva, *431.

Sphinx-moth, pen-marked,
“431.

Sphyma, 280.

Spicules, sponge, 85.

Spider and web, *237.

larva,

|

sunfish, dwarf, 271;

INDEX

Spider, crab, Bor jumping, 225°
long- legged, *2 33. een 2 34 |
running with egg-sac, *234;: tri-
angle, and web, *238.

Spider-crab, 154.

Spiders, 229; hunting, 233: seden-
tary, 233; trap-door, 233; wander-
ing, 233; web-weaving, 233.

Spinnerets of spider “232,

Spizella socialis arizone@, *360.

Sponge, ‘commercial. S6r a aresh=
water, 34; glass, «Ba skeleton of,
88; structure of, 88.

Sponges, 84; calcareous ocean, 85;
classification of, 91; developmen:
and life-history of, 89; feeding
habits of, 88; form and size of,
87; of commerce, 90.

Spongin, 86.

Spongilla sp., 84.

Springtail, American, *181.

Squamata, 312, 316.

Squid, create 2577

Squids, 255, 257.

Squirrels, 391.

Starfish, *10g; cross-section of, *112.

Starhishes, 1@S¢ orem

Stentor Sp., +79:

Sterna, 345.

Sterna maxinta, 194.

Sting-ray.)2ole

Stoney, “hos

Strix pratincola, 353.

Strong wylocentrotus Sp., Sinuelure Of,
II

Ss trongvlocentrotus 7 ranciscanus,
*T15, 1225 StRUctGne. Ol sik.

Struggle for existence, 406.

Struthio camelus, 342.

sub-species, 69.

suckers, 283:

Sucking-bugs, 197.

Sun animalcule, *78.

golden, dissec-
tion Of, Gacing) “20x itic on) 276:
structure of, 263.

Supplies, obtaining laboratory, 453.

Swans, 347.

Swarming of honey-bee, 219.

Swell-fish, 285.

Swift, common, 316.

Sword-fish, 285.

Symbiosis, 155, 413. .

Symmetry, bilateral, 5; radial, 108,

Sympetrum illotum, *1o6,

INDEX

Syngnathus fuscum, 285.

Tadpole, 55.

Tadpoles, *296.

Tenia solium, 139.

Tapeworm, 139.

Teal, blue winged,
winged, 347.

Teleostomi, -282.

Tell-tale, 349.

Teredo, 251.

fem, 194.

Terns, 345.

Terrapin, diamond-back, 314; red-
bellied, 314; yellow-bellied, 314.

Testudo sp., *315.

Tetragnatha sp., *233.

Thalarctos maritimus, 398.

Thamnophis sp., lite of, 307; struc-
ture of, 303.

Thamnophis partetalis, *320.

Theridize, 235.

Therioplectes sp., cornea of com- |

347 3

green-

pound eye of, *186.

Thomiside, 235.

Thrasher, sickle-billed, *371.

Thrush, russet-backed, *363.

Thymallus signifer, 284.

Packs, 220.

Tiger-beetles, 209.

Toad, cellular structure of, 40; de-
velopment of, 55; garden, dissec- |
tion of, 5; horned, 317; skeleton
6) aia Oe

Toads, 299, 300.

Torpedo, 281.

Tortoise, Galapagos giant, *315.

Tortoises, 313.

Tortoise-shell, 315.

Totanus melanoleucus, 349.

Trachea, *184.

Tree-frogs, 300.

Tree-toads, 300.

Trepang, 124.

Trichina, 140.

LTrichina spiralis, 14, *141.

Trichinosis, 141.

Triopha modesta, *254.

Tripoli rock, 82.

Triton, green, 297.

Trochilus colubris, 356; nest and
eggs of, *357-

Trout, rainbow, *283.

Tumble-bugs, 200.

Turdus ustulaius, *363.

483

Turkeys, wild, 350.

Turtle, green, 315 ; hawk-bill, 315 ;
logger-head, 315.

Turtle-dove, 351.

Surtles,2313-

Tympanuchus americanus, 350.

Tyroglyphus stro, *230.

Ungulata, 393.

Unio sp., life-history and habits of,
243: structure of, 239.

Uria troile californica, *344.

Ursus americanus, 398.

Ursus horribilts, 398.

Varanus niloticus, 318.
Variation, 406.

| Variety, 60.

Venation of wings of insects, 174; of
wings of Monarch butterfly, *175.
Venus mercenaria, 247.

Vermes, 127; life-history and hab-
its of, 132; classification of, 135.
Vertebrate, defined, 30; brains of,

370; eye of, *379.
Vertebrates, 259; structure of, 259.
Vespidee, 217.
Vinegar-eel, 140, *140.
Viper, 324; blowing, 321.
Vipera cerasta, 324.
Vorticella sp., *76.
Vorticella, structure and life of, 75.
Vulpes pennsylvanicus, 398.

Walking-stick, 193, 194.

Wapiti, *394.

Wasps, 212; digger, 217; solitary,217.

Water-beetle, predaceous, 210.

Water-beetles, 206.

Water-boatman, *199.

Water-boatmen, 197.

Water-flea, 148, *149.

Water-dog, 298.

Water-snake, 320.

Water-strider, 197, 199, *Ig9.

Water tiger, 212, *214.

Weevils, 209.

Whalebone, 393.

Whales, 393.

Wheel-animalcule, *143.

Whip-poor-will, 356.

Whitefish, 284.

Wild-cat, 398.

Wings of Monarch butterfly showing
venation, *175.

484 INDEX

Wolf, 398. Xiphias gladius, 285.
Woodchuck, 391.
Wood-duck, 347. Yellow-hammer, *355.
Wood-frog, 300. Yellow-jackets, 217.
Wood-lice, 150. Yellow-shank, 349.
Woodpecker, California, 356; ivory-
billed, 355; red-headed, 355. Zenaidura macroura, 351.
Woodpeckers, 354. Zoogeography, 436.
Wood-rat, 391. Zooids, 98.
Worm, army, *21I1. Zoology, a first course in, 3; de-
Worms, 127; life-history and habits fined, 3; divisions of, 2; system-
of, 133; classification of, 135; ma- atic, defined, 3.

Tane,=* £34; Zoophytes, 92,

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Henry Holt & Co.’s Works on Science

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Kerner and Oliver’s Natural History of Plants. Translated by Prof. F.
W. Ouitver of University College, London. 4to. 4 parts. With over

1000 illustrations and 16 colored plates. $15.00
Kingsley’s Vertebrate Zoology. By Prof. J.S.Krinestzy of Tufts Col-
lege. Illustrated. 439 pp. 8vo. $3.00
— Elements of Comparative Zoology. 357 pp. 12mo. $:.20
Macalister’s Zoology of the Invertebrate and Vertebrate Animals. By
ALEx. MACALISTER. Revised by A. S. PACKARD. 277 pp. 16mo. 8cc.

Macloskie’s Elementary Botany. With Students’ Guide to the Examina-
tion and Description of Plants. By GrorGeE Mactosk1z, D.Sc., LL.D.

373 PP- $1.30

MacMillan’s Plant Embryology. By Prof. Conway MacMi tan of the
University of Minnesota. (/% preparation.)

McMurrich’s Text-book of Invertebrate Morphology. By Prof. J. PLay-
FAIR McMouraicu, M.A., Ph.D., of the University of Cincinnati. vi + 661
pp. 8vo. New Edition. $3-00

McNab’s Botany. Outlines of Morphology, Physiology, and Classification of
Plants. By Witt1am Ramsay McNas. Revised by Prof. C. E. Brsszy.
400 pp. 16mo. Soc,

Merriam’s Mammals of the Adirondack Region. With an Introduction
Treating of the Location and Boundaries of the Region, its Geological
History, etc. By Dr. C. Harr MERRIAM. 316 pp. 8vo. $3.50

Nicholson and Avery’s Exercises in Chemistry. By Prof. H. H. Nicuot-
son, University of Nebraska, and Prof. SamugeL Avery, University of

Idaho. 134 pp. 6o0c,
Noel’s Buz; or, the Life and Adventures of a Honey Bee. By Mauricx
NOEL. £34 pp. Retatl, $1.00
Noyes’s Elements of Qualitative Analysis. By Prof. Wm. A. Noyes of the
Rose Polytechnic Institute. 91 pp. 8vo. 80c

Packard’s Entomology for Beginners. For the use of Young Folks,
Fruit-Growers, Farmers, and Gardeners. By A.S. PackKarD. xvi-+ 367
pp. Third Edition, Revised. $1.40.

— Guide to the Study of Insects, and a Treatise on those Injurious and
Beneficial to Crops. For Colleges, Farm-Schools, and Agriculturists.
By A. S. Packarp. With 15 plates and 670 wood-cuts. Ninth Edition.

715 pp. 8vo. $5.00
——— Outlines of Comparative Embryology. Illustrated. 243 pp. 8vo. $2.50

Peabody’s Laboratory Exercises in Anatomy and Physiology. By Jas.
HDWARD PEaABopDy of the Peter Cooper High Schoo!, New York, x+
79 pp. Interleaved. xz2mo. 6o0c.

Percival’s Agricultural Botany. By Prof. Joun Percivat of the South-—
eastern Agricultural College, Wye, England. xii+ 798 pp. r2mo. $2.50

Perkins’ Outlines of Electricity and Magnetism. By Prof. Cuas. A.
Perkins of the University of Tennessee. 277 pp. 12mo, $1.10

vii "or 3

Henry Holt & Co.’s Works on Science

——=—

Pierce’s Problems of Elementary Physics. Chiefly numerical. By E.

Dana Pikgrcz of the Hotchkiss School. 194 pp. 6oc.
Randolph’s Laboratory Directions in General Biology. By Miss Harrinr
RANDOLPH, Instructor in Bryn Mawr College. 163 pp. 8o0c.

Reighard and Jennings’s Anatomy of the Cat. By Profs. Jacop Re1GHArRD
and H. S. Jenninos of the University of Michigan. xx+498 pp. 8vo0. $4.00

Schenck and Giirber’s Outline of Human Physiology. Translated by Dr.
WiL.1AM D. ZoETHouT. With pretace by Prof. Jacqurs Logs of the Uni-
versity of Chicago. viii + 339 pp. 8vo. $1.75

Scudder’s Butterflies. By S. H. ScuppEr. 322 pp. 12mo. $1.50
—— Brief Guide to the Commoner Butterflies. xi+ 206 pp. Retazl, $1.25

— Thesame. Wutth 21 plates, containing 97 illustrations. Retatl, $1.50
— The Life of a Butterfly. A Chapter in Natural History for the Gereral

Reader. 186 pp. 16mo. Retail, $1.00
Torrey’s Elementary Studies in Chemistry. By Joszrpu Torrgy, Jr., In-
structor in Harvard. 487 pp. r12mo. $1.25
Underwood’s Our Native Ferns and their Allies. By Prof. Lucizn M.
UNnvbERWwooD of Columbia, 156 pp. $1.00
—— Moulds, Mildews, and Mushrocms. //lustrated. 236 pp. $1.50

Wheeler’s The Elements of Animal Embryology. By Prof. WiLLiam
NoxTon WHEELER ot the University ot Texas. (/x preparation.)

| White’s Qualitative Analysis. By Prof. Joun Wuirz of the University of
Nebraska. 820 pp. 80c.

Williams’s Elements of Crystallography. By Grorce Huntineton WILL-
IAMS, late Protessor in the Johns Hopkins University. x-+ 270 pp. fe
vised and Enlarged, $1.25

Williams’s Geological Biology. An Introduction to the Geological History
of Organisms. By Prof. Henry S. Wixtiiams of Yale. 8vo. 395 pp. $2.80.

Woodhull’s First Course in Science. By Prof. Joun F. WoopHuLtt of the
Teachers’ College, New York City.

I. Book of Experiments. xiv 4-79 pp. 8vo. Paper. 50C.

Il. Text-book. xv +133 pp. 12mo. Cloth. 65C.

Woodhull and Van Arsdale’s Chemical Experiments. An elementary
manual largely devoted to the chemistry of every-day life. Juterleaved.

136 pp. 6oc.
Zimmermann’s Botanical Microtechnique. Translated by Jamzs ELris
Humpurey, S.C. «xii-+ 296 pp. 8vo. $2.50

HENRY HOLT & CO.) 3s arses coe oes

- vil ’or a

TIPO BOOTS: BY THE LATE

FRANCIS A. WALKER

President of the Massachusetts Institute of Techiology

DISCUSSIONS IN ECONOMICS AND STATISTICS

Edited by Professor DAVIS R. DEWEY.

With portratt. 454+ 481 pp. 2vols. 8vo. $6.00 mel. _
Important papers on Finance, Taxation, Money, Bimetallism, Economic

Theory, Statistics, National Growth, Social Economics, etc. ‘Lhe author had
hoped to bring these papers together himself.

Tne Dial: ** Professor Dewey has performed a real service to the
public, as well asto the memory of his late chief. . . . In the present
collection the editor has not included everything General Walker ever
wrote, but has aimed, so far as possible, to avoid repetitions of
thought ... . there are some discussions of the national finances in
the period following the Civil War, which havea timely as well as his-
torical interest at the present time. .. . To improve the census was
General Walker’s work for many years, and his experience cannot fail
to be of interest tothe present generation. . . . Economicsin tiie hands
of this master was no dismal science, because of his broad sympathies,
his healthy, conservative optimism, his belief in the efficacy of effort;
and, in a more superficial sense, because of his saving sense of humor
and his happy way of putting things ... . he was the fortunate pos-
sessor of a very pleasing literary style . ... clear and interesting to
the general reader, as well as instructive to the careful student. There
could have been no more fitting monument to his memory than these
two volumes, together with the other volume of ‘ Discussions in Educa-
tion:"2’

New Vork Commercial Advertiser: ‘Clear, direct and forceful, full of
familiar illustration and appeal to fact, and always interesting. Cer-
tainly no other man has had such a wide influence on the economic
thought of America, or has done so much to elevate it. . . . This state-
ment, however, can give no adequate notion of the wealth of material
or wide scope of subjects covered by these shorter articles .... one
can almost hear the spoken word in some ef the adresses ,... an
excellent index.”’

DISCUSSIONS IN EDUCATION

Edited by JAMES PHINNEY MUNROE. 342 pp. 8vo. $3.00 %ef¢.

The author had hoped to collect these papers in a volume himself.

The Dial: “A fitting memorial to its author. . . . The breadth of his
experience, as well as the natural range of his mind, are here reflected.
The subjects dealt with are all live and practical. . . . He never deals
with them in a narrow or so-called ‘ practical’ way.”’

Literature: ‘The distinguishing traits of these papers are open-
mindedness, breadth, and sanity. . . . No capable student of educa-
tion will overlook General Walker’s book; no serious collection of
books on education will be without it. The distinguished author’s
honesty, sagacity, and courage shine on every page.”

The Boston Transcript : ‘‘ Two of his conspicuous merits characterize
these papers, the peculiar power he possessed of enlisting and retaining
the attention for what are commonly supposed to be dry and difficult
subjects, and the capacity he had for controversy, sharp and incisive,
but so candid and generous that it left no festering wound.”

Bei HOLT & CO, sa waossw ave, Chicage

ii 1900

CHEMIa i

CAIRNS’S QUANTITATIVE CHEMICAL ANALYSIS

By Freperick A. Caikns FExutirely new edition, revised and
enlarged by Dr. E. WALLEk. xii+ 417 pp. 8vo. $2.00, net.

CONGDON’S QUALITATIVE ANALYSIS

By Prof. Ernest A. Conupon, of Drexel Institute. 64 pp. /nter-
leaved. 8V0. 60C., net.

NICHOLSON AND AVERY’S EXERCISES IN

CHEMISTRY With Outlines for the Study of Chemistry. To
accompany any elementary text. By Prof. H. H.

NicHo.son, of the University of Nebraska, and Prof. SAMUEL
AVERY, of the University of Idaho. 413 pp. rzmo. 60c., xet

NOYES’S ELEMENTS OF QUALITATIVE

ANALYSIS By Prof. Wm. A. Noves. of the Rose Polytechnic Insti-
ute. x-+orpp. 8vo, 8o0C., met.

REMSEN’S CHEMISTRIES By Prof. Ira REMsEN, of Johns |

Hopkins. (American Science
Serzes.)
Inorganic Chemistry (Advanced). xxii+853pp. 8vo. $2.80, wef.
Introduction to Chemistry (4rze/er). xix+435 pp. 12mo. $1.12, ez.

In addition to its pronounced success in this country, where it is
used in hundreds of schools and colleges, the book has passed through
several editions in England, and has been translated into German
(being the elementary text- book in the University of Leipsic) French,
and Italian.

Remsen and Randall’s Experiments (jor the ‘‘Introduction’’).
50c., él.

Elements of Chemistry (Zlementary). x-+272 pp. 12m0. 8o0¢., wet.
Laboratory Manual (/o7 the “‘ Elements”’). 40¢., net.

TORREY’S ELEMENTARY CHEMISTRY

By JoserH Torrey, Jr.,of Harvard. 437 pp. 12mo. $1.25, net.

The Dial: ‘It combines lectures and demonstrations with labora-
tory work in a manner that commends itself strongly to our appro-
val. It was time for some one to say these things, and we com-
mend the book most heartily. The essential aim of the author is to
restore the disciplinary value of the study, and his method is well
worthy of attention.’

- WOODHULL AND VAN ARSDALE’S CHEMICAL
EXPERIMENTS By Prof. Joun F. Woopuutt and M. B. Van

ARSDALE, both of Teachers’ College, New York
City. “236 pp. remo, G6ocs5 er.

Extremely simple experiments in the chemistry of daily life.

HENRY HOLT & CO, 2.5652 ee

VI, 1900

RUSSIA

KRAUSSE’S RUSSIA IN ASIA, 1558-1899

With appendix, index, andtwelve maps. 8vo. $4.00.

Boston Transcript : ‘*The most masterly marshaling of the
British arguments against Russia which has appeared inalong
time. . . . The man who wrote the book has had an inside
view of Russian methods, or else he is extremely clever in col-
lecting detailed information about them. His information is
brought down to date, and his passages on the Manchurian
railway agreement show that he can see near things as vividly -
as far things: His review of the present state of Russia’s
southern boundary in Asia is striking, and sums up a great
deal of history.”’

THOMPSON’S RUSSIAN POLITICS

By Herbert M. Thompson. An account of the relations of
Russian geography, history, and politics, and of the bearings
of the last on questions of world-wide interest. With maps.
12m0. $2.00.

Outlook: ‘*The result of careful study, compactly, clearly,
and effectively presented. . . . The author’s aim is tostir the
friends of freedom throughout the world toa deeper interest in
the cause of Russian liberty. His work is vivified by the fact
that his heart is in it.”

WALLACE’S RUSSIA

By D. Mackenzie Wallace, M. A., Member of the Imperial
Russian Geographical Society. Large 1r2zmo. $2.00.

Contents include: In the Northern Forests; Voluntary
Exile ; The Village Priest ; A Peasant Family of the Old Type;
The Mir, or Village Community; Towns and Mercantile
Classes; Lord Novgorod the Great ; The Imperial Adminis-
tration; The New Local Self-Government; Proprietors of
the Modern School; The Noblesse; Social Classes; Among
the Heretics ; Pastoral Tribes of the Steppes: St. Petersburg
and European Influence; Church and State; The Crimean
War and Its Consequences; The Serfs; The New Law
Courts ; Territorial Expansion and the Eastern Question.

Nation: ‘*‘ Worthy of the highest praise. . . . Nota piece of
clever book-making, but the result ofalarge amount of serious
study and thorough research. . . . We commend his book as
a very valuable account of a very interesting people.”

GAUTIER’S A WINTER IN RUSSIA

By Théophile Gautier. Translated by M. M. Ripley.
r2mo. $1.75.

Contents: Berlin; Hamburg; Schleswig ; Liibeck; Cross-
ing the Baltic; St. Petersburg; Winter; The Neva; Details
of Interiors; A Ball at the Winter Palace; The Theatres:
The Tchoukine Dvor; Zichy; St. Isaac’s; Moscow; The
Kremlin ; Troitza; Byzantine Art ; Return to France.

New York Tribune: ‘As little like an ordinary book of
travel asa slender antique vase filled with the perfumed wine
of Horatian banquets is like the fat comfortable tea-cup ofa
modern breakfast-table.’’

Pe {okt OG (He est est Sireet

vii, 1900

Champlin’s Young Folks’ Cyclopedia of

LITEKATURE ANBAR

With 270 illustrations. 604 pp. vo. $2.50

Brief accounts of the great books, buildings, statues, pictures, operas,
symphonies, etc,

‘‘Few poems, plays, novels, pictures, statues, or fictitious characters
that children—or most of their parents—-of our day are likely to in-
quire about will be missed here. . . . Mr. Champiin’s judgment
seems unusually sound—will be welcome and useful.’’—WVation.

‘¢Every schoolboy should have it on his study table. . . . The
range of the volume is very wide, for besides those items of classical
knowledge which constitute the average school encyclopzedia, we
have brief descriptions given of modern books, poems, inventions,
pictures, and persons about which the lad of the period should be
acquainted. . . . The pictures in the volume are varied and truly illus-
trative. Old pictures and sculpture are presented in the usual line
of drawings, but modern scenes and buildings are pictured through
excellent half-tone reproductions of photographs.’”’—V. Y. Zimes Sat-
urday Review.

‘‘He has covered the ground with great completeness; and, though
his notices are necessarily brief, they give the salient facts that bring
understanding. . . . It may be, too, that its completeness will make
it serviceable as a reference book to many of maturer years.’’—

N.Y. Tribune.

‘*The four books together would constiftte the best sort of a gift
for a young person of inquiring mind.’’— 7‘%e Dra.

‘¢A most valuable reference book for schoolboys and -girls.’’~
Bookman.

‘A good book to buy for the young folks and use yourself. It
contains a great deal of handy information which, unlike the young
folks, most of us have had time to forget.’’—Zz/e.

‘¢A commendable feature is the clear way in which synopses of all
the principal operas are given.’’— Providence Journal.

Earlier Volumes of Champlin’s Young Folks’ Cyclopaedia.
With numerous illustrations. 8vo. $2,50 each,

COMMON THINGS. PERSONS and PLACES.
GAMES and SPORTS.

xy 2-page circular, with sample pages of Champlin’s Young
Folks’ Cyclopedias and his other books, free.

HENRY HOLT & CO. Epes yee
| o*
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