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The Gray Squirrel.

(Courtesy of F. H. Tucker, Boston.)

Zoology

A

A Textbook for College and
U?tiverstty Students

By

F. E. CHIDESTER, A.M., Ph.D.

Professor of Zoology, West Virginia University

NEW YORK

D. VAN NOSTRAND COMPANY, Inc.
250 Fourth Avenue

1932

'^3

Copyright, ig32,

by

D. Fan Nostra?!^ Compa?iy, Inc.

All Rights Reserved.

This book or any parts thereof may not
be reproduced in any form without
written permission from the publishers.

PRINTED IN U. S. A.

LANCASTER PRESS, INC.
LANCASTER, PA.

To the Student who uses this TexthooX:

This textbook represents many years of
learning and experience on the part of the
author. It does not treat of an ephemeral
subject, but one which, since you are study-
ing it in college, you must feel will have a
use to you in your future life.

Unquestionably you will many times in
later life wish to refer to specific details
and facts about the subject which this book
covers and which you may forget. How
better could you find this information than
in the textbook which you have studied from
cover to cover?

Retain it for your reference library. You
will use it many times in the future.

The Puhlishers.

Dedicated to
DR. AND MRS. C. W. CHIDESTER

A RARE COMBINATION IN

MEDICAL PRACTICE AND A CONSTANT SOURCE OF

STIMULATION TO SCIENTIFIC EFFORT

PREFACE

This text was written as a general survey of modern zoology for
use by college students and to serve as a reference book for biologists.
In the author's attempt to include in the introductory course not
only the basic principles so obviously essential to a general culture
course in animal biology, but also to satisfy the needs of students
entering medicine and agriculture, he has found it desirable to em-
phasize physiology, ecology and applied zoology. Many of the
most interesting portions of this text have been introduced as a
result of inquiries by keen students.

After using much of the subject matter as a mimeographed text,
the author prepared the manuscript in its final form, and during
three summers has availed himself of the aid of many specialists
at the Marine Biological Laboratory, Woods Hole, Mass. Through
the interest of various authorities who gave advance information
about their work, certain chapters include material prior to the
actual publication of the research discussed.

Some of the most important features of the book are the logical
arrangement of facts about the animals within a group, a statement
of the chief characteristics at the beginning of the discussion, and a
summary on the economic importance at the end of each section.
The newer physiology has been introduced and a bibliography
checked by experts in each field is given at the end of each chapter.
Sources readily available have been selected and resumes chosen
instead of the pioneer researches. Extensive discussions of Embry-
ology and Animal Behavior have been found undesirable since such
studies cannot be comprehensively treated in an introductory course
without excluding other fundamental subjects.

The writer takes pleasure in thanking the following colleagues
at West Virginia University: Dr. A. M. Reese, Dr. L. H. Taylor,
Mr. A. G. Eaton, Dr. L. H. Peairs, Dr. A. J. Dadisman, Mr. Chan-
dler Brooks, Dr. J. A. Eiesland, Dr. P. D. Strausbaugh, Dr. A. J.
Hare, Dr. F. B. Trotter and Dr. C. G. Brouzas.

Certain chapters have, furthermore, received the benefit of criti-
cism by the following specialists: Dr. G. N. Calkins and Dr. C. A.
Kofoid, Protozoa; Dr. M. M. Metcalf, Evolution; Dr. C. E. Mc-

vi PREFACE

Clung and Dr. E. Carothers, Cytology; Dr. A. B. Dawson, Blood;
Dr. A. C. Redfield, Respiratory Pigments; Dr. A. M. Lucas, Ciliary
Action; Dr. Edwin Linton, Dr. C. A. Kofoid, and Dr. H. W. Stunk-
ard, Platyhelminthes; Dr. Frank Smith and Dr. Earl Martin,
Annelida; Dr. N. A. Cobb, Dr. M. C. Hall, Dr. C. A. Kofoid,
Nematoda; Dr. R. S. Lynch, Dr. H. M. Miller and Dr. H. B. Smith,
Trochelminthes; Dr. B. H. Grave and Dr. E. D. Crabb, Mollusca.
Dr. C. M. Child, Dr. Austin Clark and Dr. William Patten have
kindly furnished concise summaries of their important theories.

With the aid of their staffs the following Librarians, Mr. George
Osborn, Rutgers University, Dr. L. D. Arnett, West Virginia
University, and Mrs. T. H. Montgomery, Marine Biological Lab-
oratory, have so contributed to the accuracy of the text by their
tireless efforts in furnishing reprints, references and books that they
deserve much of the credit for such corrections of errors made by
senior scholars as the author may have been able to make.

Dr. W. H. S. Demarest, Dr. F. B. Trotter, and Dr. J. R. Turner,
the University Presidents under whom the writer enjoyed every
opportunity for effective teaching that these able executives could
possibly furnish, should be heartily thanked for their aid.

The writer also wishes to acknowledge his indebtedness to: the
late Dr. C. W. Hargitt, Dr. W. M. Smallwood, Dr. C. F. Hodge, Dr.
A. M. Reese, Dr. F. R. Lillie, Dr. E. G. Conklin, Dr. C. B. Daven-
port, Dr. T. J. Headlee, Dr. Gary Calkins and Dr. C. E. McClung.
By their encouragement, these men have been largely responsible
for the vigor and enthusiasm with which the writer has been able
to study zoological problems and to teach his subject for more than
twenty years.

General criticism has been offered by Dr. J. A. Dawson, Dr.
Mary MacDougall, Dr. W. C. Curtis, Dr D. H. Tennent, Dr.
Charles Packard, Dr. R. A. Budington, Dr. W. L. DoUey, Dr.
Oscar Richards, Dr. J. W. McGregor, Dr. J. W. Mavor, Dr. Leigh
Hoadley, and many others.

In the preparation of the glossary. Professor A. J. Hare of the
West Virginia University has assumed the responsibility for the
Greek and Latin derivations of the words used.

The drawings were made by Mr. W. J. Moore, Mrs. Helena
Lammers and Mr. Norris Jones.

F. E. C.

Woods Hole, Mass.,
November 1931

CONTENTS

Preface
chapter page

I — Introduction i

The Function of Zoology — The Divisions of Zoology — Living Things
Compared with Non-Living Matter — Protoplasm — Structure of the
Cell — Structure of Protoplasm — Physiological Properties — Chemical
Composition — Proteins — Carbohydrates — Fats — Water — Chemical
Elements — Carbon — Hydrogen — Oxygen — Nitrogen — Sulphur —
Mineral Salts, Enzymes, Hormones and Vitamins — Animal Relation-
ships— Fitness to Survive — Plants and Animals — Table — Classification
— Metazoa — Vertebrates — Phylum Chordata — Sub-phylum Vertebrata
— Sub-phylum Adelochorda — Sub-phylum Urochorda — Invertebrates —
Phylum Arthropoda — Phylum Mollusca — Phylum Molluscoidea —
Phylum Trochelminthes — Phylum Annelida — Phylum Echinodermata
— Phylum Nemathelminthes — Phylum Platyhelminthes — Phylum Coc-
lenterata — Phylum Porifera — Phylum Protozoa.

II — Protozoa 21

Classification — Characteristics — Natural History — Class i. Sarcodina
— Type of Group — Ameba proteus — Orders of Sarcodina — Parasitic
Sarcodina — Class 2. Mastigophora (Flagellates) — Type of Group —
Euglena — Economic Importance of Flagellates — Class 3. Infusoria
(Ciliates) — Type of Group — Paramecium — Parasitic Ciliates — Class 4.
Sporozoa — Type Plasmodium vivax,the Malarial Sporozoon — Orders of
Sporozoa — General Considerations — External Anatomy and Internal
Differentiation — Locomotion — Ingestion and Digestion — Respiration
■ — Circulation — Excretion — Irritability — Reproduction and Regenera-
tion— Sarcodina — Mastigophora (Flagellata) — Infusoria (Ciliata) —
Sporozoa — Endomixis — Distribution — Economic Importance — Fossil
Relatives and Relationship to Other Phyla — Metazoa.

Ill — Porifera 47

Classification — Characteristics — Distribution — Pigment in Sponges —
Type of Group — Grantia — External Anatomy — Ingestion and Diges-
tion—Circulation— Respiration — Excretion — Reproduction — Nervous
System — Habits — Enemies — Associations — Economic Importance of
the Porifera — Positive — Negative — Fossil Relatives — Ancestry and
Relationship to Other Phyla.

IV — Coelenterata 54

Classification — Characteristics — Natural History — Class i. Hydrozoa
— Hydra — Obelia — Alternation of Generations In the Hydrozoa — Si-
phonophora — Class 2. Scyphozoa — Type of Group — Aurelia — Class 3.
Actinozoa — Anemones and Corals — Class (or Phylum) Ctenophora —

vii

39371

viii CONTENTS

CHAPTER PAGE

General Consideration of the Coelenterates — Distribution — Anatomy —
Physiology — Habitat — Regeneration — Fossil Relatives — Ancestry and
Relationship to Other Phyla — Economic Importance of Coelenterates.

V — ^Platyhelminthes 71

Classification — Characteristics — Natural History — Class i. Turbella-
ria — Type of Group — Planaria — Class 2. Trematoda — Anatomy and
Life History of the Liver Fluke — Trematode Parasites — Class 3. Ces-
toda — Type of Group — Taenia solium — Cestode Parasites — General
Consideration of the Platyhelminthes — Distribution — Anatomy and
Physiology — Behavior — Regeneration — Fossil Relatives — Ancestry
and Relationship to Other Phyla — Axial Gradient Theory of Child —
Nemertinea, Possibly Allied to Platyhelminthes.

VI — Nemathelminthes 87

Classification — Characteristics — Natural History — Class Nematoda —
Family i. Ascaridae — Tvpe of Group — Ascaris lumbricoides — Family
2. Anguillidae — Life History of Caconema (Heterodera) radicicola —
Family 3. Strongylidae — Life History of Necator americana — Family
4. Trichotrachellidae— Family 5. Filarldae — Life History of Filaria
bancrofti — Family 6. Trichinellidae — Life History of Trichinella
spiralis — Uncertain Classes formerly placed under Nemathelminthes —
Acanthocephala — Gordiaceae — Mermithidae — General Consideration
of the Nemathelminthes — Distribution — Physiology — Fossil Relatives
— Ancestry and Relationship to Other Phyla.

VII— Annelida 100

Classification — Characteristics — Natural History — Class i. Archi-
Annelida — Polygordius — Class 2. Chaetopoda — Type of Group —
Lumbricus terrestris — Conjugation in the Earthworm. Class 3.
Hirudinea — Type of Group — Hirudo medicinalis — Adaptation of the
Leech to its Mode of Life — General Consideration of the Annelida —
Distribution and Habits— Parasites of the Annelida — Physiology,
Anatomy, and Locomotion — Regeneration — Fossil Relatives — Ances-
try and Relationship to Other Phyla — Economic Importance of An-
nelida.

VIII — Trochelminthes • . • • 121

IX MOLLUSCOIDEA I 27

Natural History— Class i. Brachiopoda— Class 2. Bryozoa (Polyzoa)
— Class 3. Phoronidea.

X ECHINODERMATA 1^9

Classification — Characteristics — Natural History — Class i. Aste-
roidea — Type of Group — Asterias — Artificial Parthenogenesis — Class
2. Ophiuroidea — Class 3. Echinoidea — Class 4. Holothuroidea —
General Considerations — Anatomy and Locomotion — Physiology —
Behavior — Embryonic Development — Parental Care — Regeneration

CONTENTS ix

CHAPTER PAGE

and Autotomy — Fossil Relatives — Ancestry and Relationship to Other
Phyla — Economic Importance.

XI— MoLLUscA 142

Classification — Class i. Pelecypoda or Lamellibranchiata — Class 2.
Amphineura — Class 3. Gastropoda — Class 4. Scaphopoda — Class 5.
Cephalopoda — Characteristics — Natural History — Class i. Lamel-
libranchiata— Types of Group — Clams and Mussels — Natural History
of Lamellibranchiata — Class 2. Gastropoda — Natural History of Gas-
tropoda— Class 3. Scaphopoda — Value of Dentalium — Class 4. Ceph-
alopoda— Natural History — Pearls — Composition — Source and Value
— Culture Pearls — Coated Glass Substitutes for Pearls — References —
General Consideration of the Mollusca— Distribution— Physiology-
Nervous System — Regeneration — Growth Studies of the iVIollusca —
Embryology — Care of the Young — Fossil Relatives — Ancestry and
Relationship to Other Phyla — Economic Importance of Mollusca —
Positive — Negative.

XII — Arthropoda '°3

Classification— Characteristics— Natural History— Class i. Crustacea
— Types— Crayfish and Lobster— Class 2. Onychophora— Class 3.
Myriapoda— Class 4. Insecta (Hexapoda)— Type of Group— Lubber
Grasshopper— Characteristics of More Important Races of Honey Bees
—Methods of Insect Control— Class 5. Arachnida— Bibliography on
Venomous Spiders— Other Classes— Xiphosura—Pycnogonida-Tardi-
grada— General Consideration of the Arthropoda— Characteristics and
Distribution— Integument and Musculature— Digestive System—
Respiration— Circulatory System— Excretion— Nervous System and
Sense Organs — Fossil Relatives.

XIII— Chordata ^°9

Classification— Sub-phylum Hemichorda (Enteropneusta)— Sub-phy-
lum Urochorda (Tunicata)— Sub-phylum Cephalochorda (Adelochorda
or Acrania)— Sub-phylum Vertebrata or Craniata— Class i. Cyclo-
stomata— Class 2. Pisces— Class 3. Amphibia— Class 4. Reptilia—
Class 5. Aves— Class 6. Mammalia— Invertebrates versus Verte-
brates—Sub-phylum Hemichorda (Enteropneusta)— Type of Group—
Balanoglossus— Sub-phylum Urochorda (Tunicata)— Sub-phylum
Cephalochorda (Adelochorda or Acrania)— Type of Group— Amphi-
oxus— Theories of the Origin of Vertebrates— Amphioxus— Arthropod
—Annelid— Nemertean— Bibliography.

221

XIV — Cyclostomata

Craniata— Classification— Characteristics— Cyclostomata— Character-
istics— Myxinoids — Petromyzontia.

XV— Pisces ^^"^

Classification— Characteristics— Natural History— Sub-class Elasmo-
branchii— Type of Group— The Skate— Sub-class Teleostomi— Order I.

X CONTENTS

CHAPTER PAGE

Crossopterygii — Order i. Chondrostei — Order 3. Holostei — Order 4.
Teleostei — Sub-class Dipnoi — General Consideration of the Fishes —
Locomotion — Coloration — Sound Producing Organs — Respiration —
Poison Glands — Skin — Blood — Lymph — Endocrine Glands — Lymph-
oid Tissue — Senses — Messmates and Associates — Parental Care —
Habitat — ^Temperature — Electric Organs — Phosphorescent Organs —
Adaptation of Fishes to their Environment — Economic Importance —
Positive — Negative — Migration in Fishes — Homing Instinct — Fossil
Relatives.

XVI — Amphibia 265

Classification — Apoda or Coecilians — Urodela or Caudata — Anura,
Salientia or Ecaudata — Characteristics — Natural History — Order i.
Apoda — Order 1. Urodela — Family i. Amphiumidae — Family 2. Sal-
amandridae — Family 3. Oroteidae — Family 4. Sirenidae — Order 3.
Anura — Family i. Pipidae, etc. — Family 2. Bufonidae — Family 3.
Ranidae, etc. — Type of Group, Rana pipiens, the Leopard Frog — Ex-
ternal Characters of the Frog — Skin — Muscle, Tendon, Fascia — Diges-
tive System — Circulatory System — Action of the Heart — Respiratory
System — Urinogenital System — Nervous System, Sense Organs —
General Consideration of the Amphibia — Distribution — External Anat-
omy— Skeleton — Muscles — Physiology — Digestive System — Respira-
tory System — Circulatory System — Urinogenital System — Embryology
— Parental Care — Parthenogenesis — Experimental Embryology — Re-
generation— Habitat — Fossil Relatives — Economic Importance — Posi-
tive— Poisonous Amphibians — Resistance of Amphibia to Poisons.

XVII — Reptilia 302

Amnion and Allantois — Classification — Characteristics — Natural His-
tory— Super-order 2. Chelonia — Type of the Group — The Slider
Terrapin — Super-order 6. Archosauria — Order Rhyncocephalia — Or-
der Crocodilia — Order Squamata — Sub-order Lacertilia — Sub-order
Ophidia — General Consideration of the Reptilia — Distribution —
Anatomy and Locomotion — Digestive System — Respiratory System —
Superficial Differences between the Crocodilia — Voice — Circulatory
System — Excretory System — Reproductive System — Care of the Young
— Nervous System and Sense Organs — Rattle of the Rattlesnake —
Poisonous Reptiles — Action of Snake Venom on the Digestive Tract —
Toxicity — Treatment of Snake Bite — Susceptibility of Snakes to Poison
— Do Mother Snakes Swallow their Young? — Some Superstitions that
Exist Regarding Snakes (Casselberry) — Fossil Relatives — Adapta-
tions of Reptilia — References on Reptilia.

XVIII— AvEs 334

Division A. The Ratitae — Characteristics — Tinamous — Division B,
The Carinatae — Characteristics — Classification — Order i. Pygopodes
— Order 2. Longipennes — Order3. Tubinares — Order 4. Steganopodes
— Order 5. Anseres — Order 6. Odontoglossae — Order 7. Herodiones —

CONTENTS xi

CHAPTER PAGE

Order 8. Paludicolae — Order 9. Limicolae — Order 10. Gallinae —
Order 11. Columbae — Order 12. Raptores — Order 13. Psittaci — Or-
der 14. Coccyges — Order 15. Pici — Order 16. Machrochires — Order
I. 17. Passeres — Natural History — -The Anatomy and Physiology of

^ Birds — Characteristics — Temperature — Feathers — Color — Skeleton-

Digestive System — Tongue — Buccal Glands — Esophagus — Crop —
I Proventriculus— Gizzard — Small Intestine — Rectal Cecae — Rectum —

Liver — Pancreas — Circulatory System — Respiratory System — Voice —
Excretory System — Reproductive System — Nervous System — Sense
Organs — Susceptibility of Birds to Poison — Types of Nests — Bird Mi-
gration— Why Do Birds Migrate? — Speed of Flight — Economic Im-
portance of Birds — Positive — Negative — Fossil Relatives — Arche-
opteryx — Archeornis — Ichthyornis — Hesperornis — A Living Connect-
ing Type.

XIX — Natural History of Mammals 373

Characteristics — Order i. Monotremata — Order 2. Marsupialia —
Order 3. Insectivora — Order 4. Chiroptera — Order 5. Carnivora —
Sub-order Fissipedia — Sub-order Pinnipedia — Order 6. Rodentia —
Sub-order Simplicidentia — Sub-order Duplicidentia — Order 7. Eden-
tata— Order 8. Ungulata — Sub-order Hyracoidea — Sub-order Peris-
sodactyla — Sub-order Artiodactyla — Order 9. Sirenia — Order 10. Ce-
tacea — Order 11. Primates — Races of Man — Fossil Man — Mam-
mals as Migrants.

XX — Mammalia — Physiology 420

Man versus the Higher Apes — Physiology of the Vertebrate Animal —
Mammalian Physiology — External Anatomy and Locomotion — His-
tology— The Skin — Claws or Nails — Hair — Perspiration — Digestive
System — Mouth — Teeth — Salivary Glands — Tongue— Esophagus —
Stomach — Small Intestine — Liver — Pancreas — Digestion in the Small
Intestine — Cecum — Appendix — Large Intestine — Digestion in the
Ruminant — Chemical Characteristics of Protoplasm — Proteins — Col-
loids— Precipitin Reaction — Carbohydrates — Monosaccharids — Disac-
charids — Fats — Lipins — Chemical Elements of Protoplasm — Carbon —
Hydrogen — Oxygen — Nitrogen — Mineral Salts — Sulphur — Phosphorus
— Calcium — Silicon — Fluorine — Sodium — Chlorine — Potassium —
Magnesium — Copper — Iodine — Arsenic — Iron — Manganese — Bro-
mine— Boron — Zinc — Aluminium — Enzymes — Autocatalysts — Nutri-
tion and Vitamins — The Organs of Internal Secretion — Endosecretory
Glands vi'ith a Duct — Testis — Ovary — Liver — Pancreas — Ductless
Glands — Thyroid — Parathyroid — Thymus — Suprarenal — Pineal —
Pituitary — Interrelations of the Organs of Internal Secretion — Effects
'* of Emotions on the Internal Secretions — References on the Endocrines

— Circulatory System — Action of the Heart — Pulse — Comparative
Anatomy of the Portal Systems— Blood — Blood Groups — Lymph —
Lymphatics — Flow of Lymph — Spleen — Respiratory System — How
Long Can Aquatic Mammals Submerge? — Voices of Mammals — Excre-

xii CONTENTS

CHAPTER PAGE

tory System — Reproductive System — Female — Male — Propagation
Rate in Mammals — Periods of Gestation — Nervous System and Sense
Organs — A Triumph of Coordination — Fatigue in the Nerve Cell —
Regeneration in the Nervous System — Hibernation and Aestivation
Organs that Man Can Lose — Statistics of Vitality — Susceptibility
of Mammals to Poison.

XXI — Social Life of Animals 482

Association of Different Species — Living Free — Commensalism — Sym-
biosis— Parasitism — Effects of Parasitism — On Parasite — On Host —
Association of the Same Species — Colonies — Communities — Gregari-
ousness — Polygyny and Polyandry — Cases in which the Sexes Live
Apart — Societies Composed of Different Species — Monogamy — Sea-
sonal Mateships — Types of Families — Parent Families — Father
Families — Mother Families — Child Families — References on Animal
Relationships — Protection — Masking — Color Resemblance — Mimicry
— Geographical Distribution— Barriers — Salinity of Water^ — Water
Supply — Depth of Water — Temperature — Mountain Ranges — Do-
mestication of Animals — Dog — Cat — Horse — Donkey — Pig — Cattle —
Goat— Sheep — Rabbits — Pigeons— Fowls — Ducks — Geese — Peacocks
— ^Turkeys — Tissue Survival Outside of the Body — Longevity of Ani-
mals— Mammals — Birds — Reptiles — Amphibia — Fishes — Arthro-
poda — MoUusca — Annelida — Coelenterata — Pulse Frequency.

XXII — Evolution, Heredity, Eugenics 499

Cell Division — Amitosis — Mitosis — Oogenesis — Spermatogenesis — Fer-
tilization— Theories of Heredity and Evolution — History of the Evolu-
tionary Idea — What we owe to Charles Darwin — Examples of Men-
delian Inheritance in Man — The Origin of Species according to
Lamarck, Darwin, Weismann, Mendel and DeVries — Evidences for
the Theory of Evolution — i. Morphology — 2. Classification — 3.
Blood Tests — 4. Embryology — 5. Paleontology — 6. Geographic Dis-
tribution— Sex Determination — Sex Linked Characters — Crossing Over
— Genes — Lethal Factors — Physiological Basis — Parthenogenesis —
Identical versus Fraternal Twins — Hermaphroditism and the Free
Martin — Hen Feathering in the Sebright Bantam — Evidence for and
against the Inheritance of Acquired Characters — Inheritance of
Disease — i. Prenatal Infection — 2. Prenatal Injury to the Germ Cells
or Embryo — 3. Inheritance of Weakness Predisposing to Disease —
4. Inheritance through the Germinal Substance — Maternal Impres-
sions— Eugenics.

CHAPTER I

Introduction

Living as they did near the Mediterranean and Aegean seas
where tides receded and left animals upon the shore, and where
insects developed in decayed flesh, it was natural that the early
Greeks and Romans should believe in the spontaneous generation of
life. This belief persisted until the experiments of an Italian
naturalist, Redi, performed in 1688, showed that maggots originated
in meat from eggs laid by flies. In the middle of the nineteenth
century, Pasteur proved conclusively that not only larger organ-
isms, but even minute bacteria would not develop in sterilized media
unless they were introduced.

We believe that all life came from pre-existing life — omne vivum
ex vivo — but it is not our purpose to discuss in this text the various
theories of how life came into being. • We are interested in the
science of all living things, Biology (Gr. bios, life; logos, discourse),
once termed Natural History, which includes the study of the struc-
ture and activities of both plants and animals. While we must
consider the plants in their relationship to animals, we cannot
include the study of Botany, but must confine ourselves to the
study of animals, called Zoology.

The Function of Zoology.— The science of Zoology (Gr. zoon,
animal; logos, discourse) indicates to us the relationship of animals
from the unicellular to the most highly developed multicellular
organism, man. In order to understand an animal thoroughly, we
must know its anatomy, physiology, reaction to environmental
conditions, and its economic importance.

Medicine in all its aspects owes a great debt to Zoology, not only
because of the opportunity to observe lower forms under favorable
circumstances, but also because of the important relationship of
parasitic animals to each other and to man. Some of the most
important discoveries in sanitation and preventive medicme, as
well as in surgery, have been made as a direct result of zoological

studies.

Agriculture owes much of its advancement to experimental work

2 INTRODUCTION

done by medical men and veterinarians, but within the past ten
years physiologists and biochemists in agricultural and medical
colleges have united in nutrition studies, undreamed in previous
decades.

The Divisions of Zoology. — Systematic Zoology, or Taxonomy
(Gr. taxis, arrangement; nomas, law), has since the earliest days
engaged the attention of naturalists. In fact, for many years they
contented themselves with merely naming hundreds of animals.
Fierce battles were waged over the question of priority and much
time was wasted in futile arguments over species differences. In
1735 a Swedish naturalist, who took the Latin name of Linnaeus,
conceived the idea of a system of binomial nomenclature such that
the generic and specific names written in Latin or Greek could be
understood by scientists of all nations. Animals distinguished
only slightly from each other were placed as different species of the
same genus. For example, the domestic cat, the wild cat, and the
lion belong to the same genus, which we call Felis; the domestic cat
belongs to the species domestica and the lion is Felis leo. Over

f 450,000 species of insects alone have been described. The branches
of Systematic Zoology include, among others, CoTpe^^alogy, the clas-
sification of Molluscs; Entomology, the classification of Insects;
Herpetology, the classification of Reptiles; Ornithology, the classi-
fication of Birds; and Mammalogy, the classification of Mammals.
From comparison of external characters, science progressed to a
study of internal arrangement and functions. Thus we have two
great divisions arising, one which deals with the form and structure,
being called Morphology (Gr. morphe, form; logos, discourse), and
the other treating of the functions of organs and parts, called Physi-
ology (Gr. phusis, nature; logos, discourse).

Morphology includes Gross Anatomy (Gr. anatemno, to cut up),
which deals with dissection; Histology (Gr. histos, a web; logos,
discourse), which is the study of the structure of cells and tissues
usually stained by dyes; Ejnbryology (Gr. en, in; bruo, bud), which
traces the development of the egg; and Pathology (Gr. pathos,
suffering; logos, discourse), which deals with the structure of diseased
tissues. The study of Pathology is linked with Histology, Em-
bryology and Physiology.

But Zoology is by no means confined to the study of stained or
preserved specimens. It is not the type of subject that it was
termed by the Professor of Latin quoted by Conklin: "Biology

INTRODUCTION 3

deals with things as dead as the dead languages and not nearly as
well preserved."

Biology rests ultimately upon the foundation of the two funda-
mental sciences, Physics and Chemistry. Recent advancement in
the utilization of ultra-violet light and radium on animal growth
gives us an inkling of the future possibilities in Physics. The com-
paratively new science of Biochemistry is continually presenting us
with explanations of extremely important physiological processes
hitherto unknown.

' In another age, all the branches of knowledge, whether relating to
God, or man or nature, will become the knowledge of "the revelation
of a single science," and all things, like the stars in heaven, will shed
their light upon one another.' Jowett: Plato, Introduction to Meno.

Physiology (Gr. phusisy nature; logos, discourse), the study of
functions, includes the study of Animal Behavior and Psychology.
Lovatt Evans, in an address before the British Association for the
Advancement of Science, said: "Physiology is something more than
bio-chemistry and bio-physics; it is and always will remain a bio-
logical subject."

Ecology (Gr. oikos, house; logos , discourse), the study of the re-
lationship of animals to their environment, has developed far beyond
the old Natural History of which Miall said: "Natural History
is encumbered by multitudes of facts which are recorded only because
they are easy to record." The study of Physiology is now so linked
with that of Ecology that it is difficult to separate them.

Zoogeography treats of the spatial distribution of animals while
Paleozoology, which deals with their fossil remains, links Geology
with Zoology.

Evolution (Lat. e, out; volvere, roll), the study of the origin
and descent (or ascent) of species, must draw upon all fields of
Morphology and Physiology as well as on Taxonomy and Paleon-
tology. Heredity treats of the transmission of characteristics from
parents to offspring. Genetics deals with Heredity and Variation.

Living Things Compared With Non-Living Matter. — The late
Professor W. K. Brooks of Johns Hopkins University once said:
"A living thing is a being which responds to the stimulus of any
event in such a way as to adapt its actions to other events of which
the stimulus is the sign."

There are certain fundamental distinctions between living and
non-living matter, as will be seen in the following table.

INTRODUCTION

Living and Non-Living Matter

Each plant and animal has a definite size
limit and form characteristic of the
species.

Living organisms grow by intussusception,
the addition of particles of protoplasm
prepared from their food by metabolic
processes.

Living organisms contain certain ele-
ments characteristic of protoplasm, and
Including complex proteins, built up from
Carbon, Hydrogen, Oxygen and Nitro-
gen, and undergo constant tearing down
(katabolism) and upbuilding (anabo-
llsm).

Living organisms are able to reproduce
complete Individuals like themselves, and
to regenerate mutilated portions.
Besides growth and reproduction, living
matter has other powers: contractility,
irritability, nutrition, respiration and ex-
cretion.

There is no limit to the size ^ or form

reached by non-living matter (e.g.

water).

Non-living bodies grow by adding to

themselves on the outside by accretion,^

accumulations of material chemically the

same.

Non-living matter may contain the same

elements but be lacking In the spark of

LIFE.

Non-living matter Is utterly unable to
reproduce.

Non-living matter is devoid of these
characteristics.

Protoplasm

Protoplasm is the term used to indicate that complex substance
from which all living things are built up. Protoplasm is somewhat
jelly-like in appearance, and nearly colorless, but may be opaque
when it contains food particles. It is considered to be an emulsoid,
existing either as an apparently liquid sol, with minute invisible
molecules; or as a gel, firm in consistence, with larger visible par-
ticles. Protoplasm is made up of "unit masses," which we term
cells. Each cell has a nucleus and cytoplasm. Plant cells may
have a cellulose wall, but in animal cells a cell wall is frequently
absent.

Structure of the Cell. — A cell is a complex living system or
physiological unit of protoplasm which contains a nucleus. The
protoplasm outside of the nucleus is usually called "cytoplasm."
All the contents of the cell have been shown to be the seat of vital
activity, but the nucleus contains certain elements, colored readily
by dyes, hence called chromatin granules, which a vast amount of

^ Since radiation pressure will in the end overcome gravity, even the mass of a star
beginning as a nebula cannot exceed a certain limit. Nature abhors infinity of size.
(J. A. Elesland.)

^ Huxley cited crystals as an example of accretion. We now believe that crystals
are assembled by electrical forces less complicated than in organic combinations.

INTRODUCTION

scientific study has shown to be the carriers of hereditary charac-
teristics, but which may yet share the honors with unknown units.
Chemical or physical agents may combine to determine the activity
of these granules.

Cey^fro/ bodies Coenfr-osomc)

_ '^/"

PJasmosome or true nucleolus f ■^Y_Mf-^'fc)te^.;,^^/(_' A

Chromatin ^Z t^^W^^^M\'^^-A\

Linm _ ^ i-(^L-v<^P'_:.:c*--i^

Koryosome or chromatin- nucleoJus ' ' ^ '

vr/osom es

:^^'^ I "-^ ,% V^V-'-Trive wall or membrane

^^^m^^i^&i'V" ^'^■^■^'^^ i^etoplosmic or

paroplosfic boc/i&s

Fig. I. Diagram of a generalized cell. (After Wilson, The Cell in Development and
Heredity. Courtesy of The Macmillan Co.)

Cell Membrane and Cell Wall. — The cell membrane protects
the cytoplasm from many physical and some chemical injuries.
It is, however, only semi-permeable, and admits some solvents, but
retains the colloids of its own protoplasm, and excludes foreign ones.

On account of the tendency for water to pass or diffuse from a
liquid with low concentration of soluble substance, through a per-
meable membrane to a liquid with higher concentration, we find that
the energy or osmotic pressure varies with the degree of similarity
of the concentrations. In discussing two solutions, we refer to
their tonicity. For example, a solution losing water through a
membrane would be hypotonic, while the one that gained the water
would be called hypertonic. Two solutions in osmotic equilibrium
are called isotonic.

The cell membrane may have a covering of some resistant
material like chitin or hardened gelatin in the animals, or of woody
cellulose in the plants. This covering is called the cell wall.

Cytoplasm. — The most conspicuous structure in the cytoplasm,
aside from the nucleus and certain large vesicles and plastids, is the
centrosome, or central body (consult Figure i), which we find acting
as the division center for the aster in mitotic division. (See page
500.) No centrosome is present in the cells of flowering plants.

Cytoplasmic Granules. — Granules of various kinds are scattered
throughout the cytoplasm, suspended in the clear, viscid "hyalo-
plasm." The relatively large yolk granules occur as solids, semi-
solids or as liquid drops. Fat and glycogen appear as cell inclusions.

6 INTRODUCTION

Plastids, found chiefly in plant cells, aid in the formation of
starch and various pigments. Chlorophyll bodies, the centers of
formation of starch by photosynthesis, are considered the most
important of the chloroplastic type.

Secretory granules of various chemical composition and physical
consistency, more or less transitory in nature, are found in secretory
cells. They dissolve to produce fat, mucin, or an enzyme. (See
page lo.) Storage granules are also quite generally distributed.

Fibrillae, almost as characteristic as granules, appear in many
types of cells, including gland cells, nerve cells and muscle cells.
Fibrillae may be produced by the fusion of small granules, but like
certain other cytoplasmic inclusions, some fibrillae are regarded as
artifacts.

The chondriosomes or mitochondria vary in form from granules
of 0.2 mu. to rods and filaments of much greater length. They are
found in most living cells and resemble albumins somewhat, both
in solubility and in staining reactions. The earlier technique of
fixation by acids such as acetic destroyed the mitochondria, but
they are shown successfully in living cells by Janus Green B.
Regaud suggested, as a possible explanation of their function, that
they are the centers of chemical action, and that they extract
substances from the protoplasm, transforming them into specific
intra-cellular structures. Cowdry has suggested that they supply
a surface-film, perhaps with a significance comparable to the nuclear
and cytoplasmic membranes.^

The Golgi apparatus is the term given to a group of cell-com-
ponents found widely distributed in both plant and animal cells.
They, like chondriosomes, require fixation by reagents lacking
acetic acid. Osmic acid fixers seem to show them best. The
apparatus appears in diffuse form as separate bodies, or in localized
form as a "Golgi net" consisting of concentrated fibrils. It has
been suggested by Nassanov, Bowen and others that the Golgi-
bodies have a secretory function. Bowen suggested that the Golgi
apparatus may be a center for the formation of enzymes.

H. Hibbard (Arch. d'BioL, Tom. 38, p. i, 1927) and M. Parat
(Arch. d'Anat. mic, Tom. 24, p. 73, 1928) have shown that Golgi-
bodies may be depositions of the stain used. We are still in con-
siderable doubt regarding the function of Golgi-bodies, mitochon-

' Consult Osterhout, W. J. V. 1929. Some aspects of permeability and bioelec-
trical phenomena. Bull. Nat. Res. Council, pp. 170-288, Washington, D. C.

INTRODUCTION 7

dria and other cell components, but it Is hoped that improved tech-
nique in fixation and staining, together with the development of
tissue culture studies and the micro-manipulation of living cells,
will reveal the functions of real structures and indicate which
granules are only artifacts.

There are other scattered bodies in the cytoplasm, not readily
seen but "haloed" under strong illumination, which may be the
ultimate units from which chondriosomes and Golgi-bodies are
aggregated.

Nucleus. — The nucleus is visible in living cells. Some cells
contain several nuclei, as in the giant cells of bone marrow, and
many others are found to contain two types of nuclei, certain
protozoa, In fact, having both a nutritive and a reproductive
nucleus. The nucleus is essential to the life of the cell, and is related
to metabolism and the secretory phenomena.

The nuclear monbrane, tough and elastic. Is found In the majority
of animal cells, but is absent in certain protozoa. It disappears
during mitosis (indirect cell division, page 500).

The nucleo-reticulum consists of chromatin, which Is stained by
basic dyes. Chromatin may appear in the form of fine granules,
larger granules, or in a network, with net-knots of massed granules.
(See Fig. i.)

Chromatin granules {chromomereSy chromioles) are suspended on
a reticulum of linin, which is delicate In structure and stained by
acid dyes. The granules aggregate to form chromosomes,'* which
are constant In number for the cells of the same species. Appar-
ently the granules are not dissociated, but usually prepared to
reassemble. The chromosomes are carriers of hereditary /«f/orj or
"genes," although we are not certain that they are the sole means of
transmission from one generation to the next. (See p. 538.)

Nucleolus. — The nucleolus or plasmosome Is a dense body,
spherical in shape, and chemically different from chromatin since
it Is stained with acid dyes. During cell division, the nucleolus
usually disappears. Sometimes there are several nucleoli, which
may play a part in the metabolism of the cell.

Structure of Protoplasm. — The fact that protoplasm differs
under various physiological conditions has given rise to several

*" Chromosomes are individual chromatic elements which appear definitely in
the nucleus at the end of the prophase stage and which act as unit structures during
mitosis." E. Carothers. See page 500 for a discussion of mitosis.

8 INTRODUCTION

theories of its structure. The granular theory suggests that a
protoplasmic mass is made up of minute granules which mass into
solids or arrange themselves in a linear series to form fibrils. The
fibrillar theory notes the fibrous structure of certain organs and
stresses the idea of a feltwork of fibrils. According to the reticular
theory, protoplasm is to be compared to a fish net or a hammock.
The alveolar theory indicates that protoplasm is comparable to an
emulsion such as milk, or a mixture of oil and water. The colloidal
theory recently championed by E. B. Wilson suggests that the alveoli
are of secondary origin and that the ultimate particles, "minute
scattered bodies, finally produce an emulsion-like structure."

Physiological Properties. — Protoplasm has the power to utilize
foods, to grow and repair wastes and develop energy. It secretes
usable material and excretes wastes. Repair of broken-down tissues
and construction of new is termed anabolism. The destruction of
waste materials is called katabolism. Both processes combined,
which result in life activity, are called 7netabolism. Protoplasm
responds to all sorts of external stimuli, adjusting itself to the
environment whenever possible. Finally it has the power of re-
production and a limited power of regeneration.

Chemical Composition. — When we attempt an analysis of the
chemical constituents of living protoplasm, we induce important
changes. By weighing the material before treating it, and then com-
paring the weights of all substances determined, we find that it is
possible to learn most of the constituents, except that all important
one — LIFE. Protoplasm consists of proteins, carbohydrates, fats,
inorganic salts, enzymes, water and the "vitamins."

Proteins, which constitute about 40 per cent of dry protoplasm,
are compounds with high molecular weights, containing about 53
per cent carbon, 22 per cent oxygen, 17 per cent nitrogen, 7 per cent
hydrogen. They also contain small quantities of sulphur and
phosphorus. Proteins include the albumen of eggs, fibrin of the
blood and casein of milk. They are colloids, and as such do not
readily diffuse through membranes nor go into solution.

Carbohydrates, which constitute about 11 per cent of dry pro-
toplasm, consist of carbon, hydrogen and oxygen, the last two
elements being always present in the same ratio as in water, dextrose
for example being C6H12O6. Glycogen, the only example of animal
starch, is found chiefly in the liver and muscles. Carbohydrates
can be converted into fats.

INTRODUCTION 9

Fats, constituting about 12 per cent of dry protoplasm, contain
carbon, hydrogen, and oxygen in such proportions that there is
much less oxygen than in the carbohydrates. Fats of the body are
derived from fatty substances consumed and are also formed from
carbohydrates and proteins. Fats are essential in maintaining the
proper body temperature.

Water is most essential to life and constitutes over 50 per cent
of the weight of most animals. Even the most ardent anti-pro-
hibitionist is made up of about 60 per cent water. It is necessary
to bathe tissues and to furnish the adequate liquid for blood, lymph
and cerebro-spinal fluid.

Chemical Elements of Protoplasm. — Carbon compounds are the
primary materials of protoplasm. About 18 per cent of protoplasm
consists of carbon. Carbon unites with oxygen to form carbon
dioxide |B|HflH| and to liberate energy.

Hyaroger^^hout 1 1 per cent of protoplasm) is taken into the
bodies of plants and animals in combination with oxygen as water,
and is also excreted in this form.

Oxygen is found in the free state and unites with various com-
pounds of protoplasm, the process of oxidation releasing energy.
In combination with living tissues we find that oxygen makes up
about 65 per cent of protoplasm.

Nitrogen is essential to protoplasm of which it comprises about
1 per cent. It forms 79 per cent of the atmosphere. Taken into
plant bodies usually in the form of nitrates, the plants utilize it in
the manufacture of proteins. Jfjimonia, a nitrogen compound,
formed in the katabolism of plants and animals, is changed by
certain bacteria into nitrates which are then absorbed by plants.

Sulphur, usually found in the soil as calcium sulphate, is ab-
sorbed by plants and used in the manufacture of some amino-acids.

Mineral Salts, Enzymes, Hormones and Vitamins. — The above
elements are said to comprise about 99 per cent of the weight of an
animal, but there are a number of other elements present in various
chemical combinations in extremely minute quantities. Some of
these are absolutely necessary to life, while others influence the
glands of internal secretion and thus aflfect growth. Among the
most important of these elements are iodine, iron, calcium, phos-
phorus, chlorine, magnesium, potassium, and sodium. Other
elements assuming greater importance every day are arsenic,
manganese, copper and zinc. Suffice it to say here that mineral

10 INTRODUCTION

salts are so essential to life that if they are withheld from the
animal body, death ensues much more quickly than from the lack
of proteins, carbohydrates, and fats. In solution the salts of the
body provide the proper medium for living tissues, and aid in main-
taining the optimum condition of physiological equilibrium. (For
a further discussion of the significance of the salts of these elements
see page 437.)

Enzymes are complex organic substances produced in living cells
by glands some of which are modified to produce other important
secretions. Enzymes are able as catalysts to hasten chemical reac-
tions, but do not enter into the end product of the reaction, and are
not themselves consumed.

Endocrine glands are glands of internal secretion that produce
catalyzing hormones which act as "messengers of stimulation," in-
fluence growth, and regulate the animal througlfHlyMjj^ole life.
(See page 444.)

Vitamins are certain accessory food factors that have been
studied extensively since 191 1. Just what their chemical com-
position may be has not yet been fully decided. The reader will
find further discussion of the subject in the section on Nutrition and
the Endocrines (page 441).

Animal Relationships

Fitness to Survive. — If we study simply the structure and the
activities of organisms and neglect the relation of the living being
to its environment, our study is not Biology, or the science of life.
Biology introduces a new problem, that of fitness. Biology asks
"When, how, why.?" Aristotle said: "The essence of a living thing
is not what it is made of, nor what it does, but why it does it."

It is the adjustment of the individual to his environment which
makes life possible. Life is one long continuous fight, a "struggle
for existence." T. R. Malthus in his "Principles of Population"
showed that human population tends to increase in a geometrical
ratio (i, 2, 4, 8) while the food supply tends to increase in an arith-
metical ratio (i, 2, 3, 4, 5, 6, 7, 8). Famines are still occurring in
India and China.

Today man is dependent on his fellow man for his subsistence
and directly or indirectly dependent on the plants and animals
about him. Each animal or plant represents a force in Nature and
is beneficial or injurious. If we study the habits of animals we will

INTRODUCTION ii

be able to evaluate them and to determine whether they should be
treated as friends and encouraged to increase, or even artificially-
propagated, or whether they should be attacked by chemical and
mechanical agencies or by protecting their natural enemies.

The most practical way within our reach of studying that
adjustment between the organism and the external world — the
fitness — which constitutes life is to learn all we can about the
physical basis, and all we can about its fitness.

To study life, we must consider three things: (i) the orderly
sequence of external nature; (2) the living organism and the changes
that take place in it; and (3) that continuous adjustment between
the two sets of phenomena which constitutes life.

Plants and Animals. — It might appear that, since man is an
animal, Zoology is the more important of the two studies. But we
must remember our thesis — the proper relation of the individual to
his environment — and we will see that plants and animals alike make
up the environment. The study of the relation of animals and
plants to disease is at present demanding the attention of some
of the world's greatest scientists.

To Linnaeus (1707-78) we owe the classification of plants and
animals. He stated that "plants grow and live, while animals
grow, live, and feed." Owen (1803-93) declared that a definition
of plants excluding all animals, or of animals excluding all plants,
is impossible. As we go down to the simplest forms we find dif-
ficulty in distinguishing between plant and animal. No one can
tell. We call these lowest types Zoophytes (Protista) and Phytozoa.

Origin. — Every organism kiiown in nature arises as a simple cell.
In the plant we call it the ovule; in the animal the ovum.

Composition. — So far as their chemical nature is concerned, the
plant and animal cell are the same. This has been repeatedly
proved. All contain carbon, hydrogen, oxygen, and nitrogen.
The skeletons, however, differ widely. The skeleton is largely a
cell wall modified in many ways. In general, plants exhibit a linear
aggregation of cells, while animals show a mass aggregation.

Morphology. — No outline can be drawn which will be common
to all plants and animals.

Physiology. — Plants and animals stand widest apart in the
mode of nutrition, and here we have the chief distinctions:

12

INTRODUCTION

Characteristics of /inimals

Animals usually have a
definite shape and are
possessed of automatic
motion.

Animals depend chiefly on
solid food which is liqui-
fied by internal digestion.

Animals derive carbon
from starch, sugars, fats,
from plants and from
other animals.

Animals derive their Ni-
trogen from complex ni-
trogenous compounds
formed by other organ-
isms. They secrete Ni-
trogenous wastes.

Animals are chiefly de-
void of chlorophyll.

Animals are composed of
cells with or without cell
walls and chiefly without
cellulose.

Animals have more
marked division of labor
among the organs and tis-
sues of the body.

Animals use the potential
energy of food, changing
it into kinetic energy.
We may say they are
generally oxidizers.

Animals are destructive
or katabolic.

Exceptions

Some plants move and
some animals are sta-
tionary.

Certain parasites, animal
and plant, absorb food
from that to which they
are attached.

Symbiotes in hydra make
food for hydra and hydra
makes CO2 for symbiotes.
Fungi are also exceptions.

Some Protozoa live like
plants and some plants
are carnivorous.

Some protozoa, sponges
and coelenterates have
chlorophyll while some
parasitic plants have no
chlorophyll.

Cellulose is found In
Flagellates and the tunic
of Tunicates.

Characteristics of Plants

Plants have a more vari-
able shape and are devoid
of automatic motion.

Plants absorb food In the
form of liquid or gases.

Plants derive their Car-
bon chiefly from CO2 of
the air and water.

Plants derive their Nitro-
gen from simple Nitrogen
compounds especially in
the soil. They do not
give oflF Nitrogenous
wastes.

Plants are chiefly chloro-
phyll bearing and use the
kinetic energy of sunlight
in building up complex
compounds.

Plants are composed of
cells with definite cellu-
lose walls

Plant cells show little
division of labor.

Plants build up simple
food into complex sub-
stances. They convert
kinetic energy of sunlight
into potential chemcal
energy. They are re-
ducers of carbon dioxide,
liberating oxygen.

Plants are predominantly
constructive or anabolic.
They make more energy
than they can use.

Classification

Natural Classification is an attempt to group animals on the
basis of similarity in structure and probable relationship.

INTRODUCTION 13

Let us trace the cat from Kingdom to Species.

Kingdom — Animalia
Phylum — Ch or data

Su b-Ph YLUM — Vertebrata
Class — Mammalia
Order — Carnivora
Fami l y — Felidae
Genus — Felis

Species — Felis domestica.

Metazoa. — /\nimals belonging to the Phyla above the Protozoa
have many cells and are called Metazoa (Gr. meta, beyond; zoow,
animal). Beginning as single cells, the Metazoa pass through
stages in which the cells are arranged in at least two layers, the
ectoderm and the endoderm. As adults Metazoa are made up of
cells arranged in unlike groups. Definitely specialized for par-
ticular functions, we find the cells dependent on one another, and
manifesting a pronounced "division of labor."

It is customary to begin the study of zoology with types of the
Protozoa, the lowest of the great divisions of animals. But before
we take up these forms, it may be well to survey briefly the animal
kingdom, beginning with the highest group of Vertebrates, the
Mammalia, to which class we belong.

Vertebrates

Vertebrates belong to the most highly developed Phylum of the
animal kingdom, called Chordata. Members of this group include
five well known classes, Fishes, Amphibians, Reptiles, Birds, and
Mammals. All of them possess a bony axis called the backbone or
vertebral column. In general we find that the vertebrates are of
much larger size than the invertebrates, and their greater activity
is accompanied by special adaptations of structure.

Phylum — Chordata. —

Sub-Phylum — Vertebrata

Class I. Cyclostomata

Class II. Pisces

Class III. Amphibia

Class IV. Reptllia

Class V. Aves

Class VI. Mammalia

14 INTRODUCTION

To the vertebrates belong all the most familiar animals such as
fishes, frogs, snakes and dogs. Vertebrates have certain structures
in common:

I. Remarkable similarity in the three divisions of the body,
head, trunk, and tail.

1. All vertebrates are bilaterally symmetrical, i.e. a plane passed
through an axis of the body will divide it into two equal halves.

3. A supporting axis, the notochord, is found at some stage of
development in all forms, but is replaced in all higher vertebrates
by an axial skeleton. Both appendicular and axial skeleton are
internal.

4. All vertebrates have two body cavities, the coelom and the
digestive tube.

5. The nerve cord is hollow and dorsal to the alimentary canal.

Class Mammalia (13,000 species). — Mammals are warm-blooded
animals with hair or wool covering the body, having a muscular
diaphragm which separates the chest from the abdomen. They
never have gills, but breathe by lungs. They have a well developed
and usually convoluted brain with many important association
tracts. While some mammals are adapted to aquatic and others
to aerial life, the majority are suited to life on land. Except in a
few of the lower forms we find that before birth young mammals
are closely attached to their mothers by a structure called the
placenta. In general, mammals are further advanced at birth than
in the lower classes of vertebrates. Mammary glands furnish
nourishment to the young until they are able to shift for them-
selves. Mammals range from the most highly developed form,
man, to the primitive duckbill platypus, which lays eggs and has
diffuse mammary glands.

Class Aves (23,000 species). — Birds are unlike mammals, having
specialized in a quite different direction. They have a body tem-
perature ten degrees higher than that of the mammals, and are dis-
tinguished from all other animals by the presence of feathers. Their
highly developed wings and pectoral muscles, hollow bones, large
lungs, and air sacs adapt the majority of them to an aerial life,
although some forms like the ostrich are flightless. Birds are of
great economic importance in the extermination of insects, but they
are of aesthetic value since many of them are beautifully colored,
while others are sweet singers.

Class Reptilia (5,000 species). — Reptiles differ more widely

INTRODUCTION

15

among themselves than other classes of vertebrates. In some
respects they appear to be related to both birds and mammals.
They have scaly or armored skins, never have gills, but breathe by
lungs and are cold blooded. They have three chambers to the
heart, the ventricular septum being perforate in all except the
crocodilia. Living forms are terrestrial or aquatic but extinct forms
were aerial. With the exception of a few lizards and snakes, they
are oviparous. (Lizards, snakes, turtles, alligators.)

Class Amphibia (4,000 species). — With slimy skins, the modern
species lacking armor, but externally resembling the reptiles so
much that Cuvier once termed them "naked reptiles," the amphibia
mark a transition from the aquatic life of fishes to the terrestrial
life of reptiles. In the larval condition practically all amphibia
have gills, while as adults they breathe by lungs, although in some
forms gills still persist. Amphibia are cold blooded, and their
unpaired fins are never supported by fin rays. They are, with a few
exceptions, oviparous. (Salamanders, frogs, toads.)

Class Pisces (20,000 species). — As strikingly adapted to life in
the water as birds are to life in the air, the fishes are all aquatic,
moving chiefly by a muscular tail. They have paired appendages
in the form of fins, and unpaired median fins always supported by
fin rays. All have permanent gills supported by cartilaginous or
bony gill arches. Fishes are cold blooded, the body temperature
remaining the same as that of the medium in which they swim.
The heart is two chambered, only the lung fishes exhibiting a prim-
itive auricular septum. In the skin of most fishes, one finds scales.
Some fishes are oviparous, others are viviparous. (Shark, sturgeon,
mackerel, trout.)

Class Cyclostomata. — While they somewhat resemble the bony
true eels, the hags and lampreys have no jaws, no lateral appendages
and no scales. A rasping tongue and a circular sucking mouth are
present. The gills are pocket-like and the vertebrae are separate
from the notochord. Lampreys are true vertebrate parasites.

Sub-phylum Adelochorda {Cephalochordd). — Fish-like forms once
classed with the mollusca. Branchiostoma (Amphioxus) has a
dorsal fin, lateral metapleural folds, well developed myotomes, and
a persistent notochord. The nerve cord has a neurocele. A
pharynx, with many gill slits, leads into a ventral atrium and
currents pass out the atriopore. A cranium is absent.

Sub-phylum Urochorda (1,500 species). — Once called worms, the

i6 INTRODUCTION

tunicates or "sea squirts" were later called mollusca. They are
characterized by a cellulose tunic, retrogressive metamorphosis
and reversible heart beat.

Invertebrates

Having described briefly the Urochorda and Adelochorda, which
we may consider types intermediate between the Vertebrates and
the Invertebrates, let us consider the characteristics that differen-
tiate the Invertebrate Phyla. We have seen that all the Verte-
brates belong to the same Phylum, and are to a great extent related,
but the Invertebrate Phyla are widely different in characteristics.

1. Invertebrates have neither internal skeleton nor notochord.

2. For the most part their nervous system is ventral to the di-
gestive tract.

3. They lack gill slits or visceral clefts.

4. When present, the heart is dorsal.

Phylum Arthropoda (450,000 species). — Segmented animals,
some with jointed appendages. Body covered by a chitinous exo-
skeleton secreted by cells beneath It; bilaterally symmetrical, with
anus but poorly developed coelom. (Examples — crab, spider, mos-
quito.)

Phylum Mollusca (60,000 species). — Unsegmented with no true
appendages. Fundamental bilateral symmetry Is lost in Gastro-
poda; while the ventral muscular foot characteristic of the group is
subject to modification. Frequently a bilobed shell is present with
the mantle, a dorsal fold of the body wall covering the animal.
Sometimes both shell and mantle are absent; but a coelom and anus
are present. (Examples — oyster, clam, snail and octopus.)

Phylum Molluscoidea (2,000 species). — a. Bryozoa or Polyzoa-
Colonlal, like some Coelenterates. Complete alimentary canal.
Large body cavity. (Pectinatella is the commonest fresh water
form.) b. Brachiopoda — once gigantic bivalves, rulers of the ocean.

Phylum Trochelminthes (500 species). — Somewhat resembling
the Infusorian protozoa, the Rotifers are often called "wheel ani-
malcules." Well developed digestive system with mouth, mastax
(chewing stomach), glandular stomach, intestine and anus. Fe-
males large, males few In number and small; resemble larvae of
annelids and molluscs.

Phylum Annelida (4,000 species). — Visibly segmented worms
with three cellular layers. (Triploblastic.) No jointed appen-

INTRODUCTION 17

dages; setae in the skin. Coelom opens to exterior by dorsal pores
and ventral nephridiopores. Alimentary canal well developed and
usually specialized. Nervous system consists of two dorsal ganglia
and a ventral chain of ganglia. (Examples — earthworm, leech.)

Phylum Echinodermata (3,000 species). — Triploblastic (three
layered) with a calcareous exoskeleton in plates or as spicules;
larvae bilaterally symmetrical but adults radially symmetrical.
The coelom is well developed; slow locomotion facilitated by water
vascular system; all marine; never bud to form a colony. (Ex-
amples— starfish, sea urchin, and brittle star.)

Phylum Nemathelminthes (1,500 species). — Unsegmented with
an elongate cylindrical body covered with tough cuticle; tubular
digestive tract with mouth and anus; coelom present; paired ex-
cretory organs and tubular gonads; nerve ring and associated gan-
glia; many parasitic. (Examples — hookworm, eel-worm, trichina.)

Phylum Platyhelminthes (4,600 species). — Unsegmented flat-
tened worms, bilaterally symmetrical and with three distinct layers
(triploblastic). Free living forms have a gastro-vascular cavity
with no anus, while the degenerate parasitic forms lack a digestive
cavity. (Examples — liver fluke, tape worm, and planaria.)

Phylum Coelenterata (4,500 species). — Radially symmetrical
with two cellular layers, and a non-cellular mesoglea; single gastro-
vascular cavity or Coelenteron; formerly called Zoophytes. Sting-
ing cells or nematocysts in the body wall. (Examples — corals, sea
anemones, jelly fishes and hydroids.)

Phylum Porifera (2,500 species). — Bodies of sponges consist
of a mass of connective tissue with two-layered (diploblastic) body
wall penetrated by canals or pores. All are aquatic, mostly marine.
Radially symmetrical; skeleton of spicules usually supports the body
wall. (The common bath sponge is an example.)

Phylum Protozoa (10,000 species). — Although it would seem
that in some respects sponges might be considered colonial Protozoa,
we must distinguish the latter from all Metazoa by their charac-
teristic of being complete single celled animals, without true tissues.
They are mostly so small as to be visible only with the aid of a
microscope; many species are colonial; many are parasitic.

PHYLUM PROTOZOA.
Class I. Sarcodina.
Class II. Mastigophora
Class III. Infusoria.
Class IV. Sporozoa.

1 8 INTRODUCTION

PHYLUM PORIFERA.

PHYLUM COELENTERATA.
Class L Hydrozoa.
Class n. Scyphozoa.
Class IIL Actinozoa or Anthozoa.

PHYLUM OR CLASS CTENOPHORA.

PHYLUM PLATYHELMINTHES.
Class L Turbellaria.
Class IL Trematoda.
Class IIL Cestoda.
Uncertain Class, Nemertinea.

PHYLUM NEMATHELMINTHES.
Class I. Nematoda.
Uncertain Classes.
Acanthocephala.
Gordiaceae.

PHYLUM ANNULATA, OR ANNELIDA.
Class I. Archi-Annelida.
Class II. Chaetopoda.
Class III. Hirudinea.

PHYLUM TROCHELMINTHES.

PHYLUM MOLLUSCOIDEA.
Class I. Brachiopoda.
Class IL Bryozoa.
Class IIL Phoronidea.

PHYLUM ECHINODERMATA.
Class I. Asteroidea.
Class II. Ophiuroidea.
^^}\ Class III. Echiftoidea.

Class IV. Holothuroldea.

PHYLUM MOLLUSCA.
Class I. Pelecypoda.
Class IL Amphineura.
Class III. Gastropoda.
Class IV. Scaphopoda.
Class V. Cephalopoda.

PHYLUM ARTHROPODA.
Class I. Crustacea.
Class II. Onychophora.
Class III. Myriapoda.
Class IV. Insecta (Hexapoda).

Order i. Thysanura (Aptera).

Order 2. Ephemerida.

Order 3. Odonata.

Order 4. Plecoptera.

Order 5. Isoptera.

Order 6. Corrodentia.

INTRODUCTION 19

Order 7. Mallophaga.

Order 8. Thysanoptera.

Order 9. Euplexoptera.
Order 10. Orthoptera.
Order 11. Hemiptera.
Order 12. Neuroptera.
Order 13. Mecoptera.
Order I4. Trichoptera.
Order 15. Lepidoptera.
Order 16. Diptera.
Order 17. Siphonaptera.
Order 18. Coleoptera.
Order 19. Hymenoptera.

Class V. Arachnida.

Other Classes.

Pycnogonida.
Tardigrada,

PHYLUM CHORDATA.

Sub-phylum Hemichorda (Enteropneusta).
Sub-phylum Urochorda (Tunicata).
Sub-phylum Cephalochorda (Adelochorda or Acrania).
Sub-phylum Vertebrata or Craniata.

Class I. Cyclostomata,

Class II. Pisces.

Sub-class Elasmobranchii.
Sub-class Teleostomi.

Order i. Crossopterygii.

Order 2. Chondrostei.

Order 3. Holostei.

Order 4. Teleostei.
Sub-class Dipnoi.

Class III. Amphibia.

Order i. Apoda or Coecilians.
Order 2. Urodela or Caudata.
Order 3. Anura (Salientia or Ecaudata).

Class IV. Reptilia.

Super-order i. Cotylosauria.

Super-order 2. Chelonia.

Super-order 3. Therapsida (Theromorpha).

Super-order 4. Sauropterygia.

Super-order 5. Ichthyopterygia.

Super-order 6. Archosauria.

Class V. Aves.

Division A. Ratitae.
Division B. Carinatae.

Order i. Pygopodes.

Order 2. Longipennes.

Order 3. Tubinares.

20 INTRODUCTION

Order 4. Steganopodes.
Order 5. Anseres.
Order 6. Odontoglossae.
Order 7. Herodiones.
Order 8. Paludicolae.
Order 9. Limicolae.
Order 10. Gallinae.
Order 11. Columbae.
Order 12. Raptores.
Order 13. Psittaci.
Order 14. Coccyges.
Order 15. Pici.
Order 16. Machrochires.
Order 17. Passeres.

Class VI. Mammalia.

Order i. Monotremata.
Order 2. Marsupialia.
Order 3. Insectivora.
Order 4. Chiroptera.
Order 5. Carnivora.

Sub-order Fissipedia.

Sub-order Pinnipedia.
Order 6. Rodentia.

Sub-order Simplicidentia.

Sub-order Duplicidentia.
Order 7. Edentata.
Order 8. Ungulata.

Sub-order Hyracoidea.

Sub-order Perissodactyla.

Sub order Artiodactyla.
Order 9. Sirenia.
Order 10. Cetacea.
Order 11. Primates.

CHAPTER II

Protozoa

The Protozoa (Gr. protos, first; zoon, animal) are the simplest
living animals and some of them resemble plants. Primitive and
mostly microscopic though they are, the Protozoa are complete
organisms in a single cell, carrying on the physiological processes of
higher forms. A protozoan may be ameboid, flagellated, or ciliated,
depending on its organs of locomotion.

Classification

Class 1. Sarcodina (Gr. sarx, flesh) move by false feet or pseudo-
podia.

Class 2. Mastigophora (Gr. ?nasfix, whip; and phero, bear) move by
flagella.

Class 3. Infusoria (Lat. in/usus, crowd In) move by cilia, and are
also called Ciliata.

Class 4. Sporozoa (Gr. spo?'a, seed; and zoon, animal). No loco-
motor organs in adult stage.

Characteristics

1. Morphologically the simplest ones are equal to isolated epi-

thelium.

2. Physiologically they are equal to the whole group of cells making

up the human body. Protozoa are complete unicellular
organisms and many have a brief multicellular phase.

3. Functionally they epitomize life processes.

4. Theoretically they are generalized cells.

5. Of practical economic importance, they cause many diseases.

6. As soil organisms protozoa are of doubtful importance.

Protozoa were first discovered by Leeuwenhoek in rain water.
Misconceptions arose because of the insufficient magnification
possible. O. F. Mueller (1786) made the first classification. He
classified 350 species, 150 of which are still regarded as valid. He

21

22

PROTOZOA

believed them to be the simplest form of animal. Von Siebold and
Kolliker (1849) proved that Protozoa are single cells and complete
organisms as well. Max Schultze (1865) gave the present idea.

Natural History

Class I. Sarcodina. Type of Group — Ameha proteus. Ex-
terna/ Anatomy. — Amebae resemble minute grayish animated par-
ticles of jelly. Some species of amebae, large enough to be seen

Pseudopodium

Cry:sfal

4^ ii^fe^"'^^^'^

' •S:'a

vacuole V . -fiT^ - ^^■■&-'-^^^^^=^- — -^^r—Food particle

Fig. iA. Ameba proteus-dubia SchaefFer. (Drawn by H. N. Lammers, after E. F.
Botsford, Jour. Exp. Zool., vols. 45-46, 1927.)

with the naked eye, have been selected and cultivated for laboratory
use. The diameter of the smaller ones is as little as five microns.
They constantly change their shape, sending out little projections
called pseudopodia, or "false feet" (Fig. 2, A and B).

The outer covering of the ameba is called the ectosarc (ectoplasm)
and is lacking in color. The inner portion of the animal called the
endosarc (endoplasm) contains the nucleus, the synthetic and
hereditary center of life, and vacuoles of different types. The

PROTOZOA

23

presence of numerous granules and particles of food gives the
animal a grayish appearance.

Fig. iB. Jmeia dividing. (Drawn by H. N. Lammers, after E. F. Botsford, Jour.

Exp. Zool., vols. 45-46, 1927.)

Locomotion. — There are a number of theories attempting to
explain the movement of ameba, but none of them seems quite
adequate.

According to the contractile theory of Bellinger (1906) and others,
contractile fibrillae were postulated. He showed that when viewed
with the microscope in a horizontal position the ameba "walks"
on stiff pseudopodia ^ (Fig. 3 A).

is-iiri

\~-AdvQncinq pseudopodium

Fig. 3//. Locomotion of Ameba. (After Bellinger.)

The surface tension theory indicates that ectoplasm is most
rapidly formed at the point where surface tension is increased.
Schaeffer (1920) has also emphasized the fact that ameba has a
wavy path or a flattened spiral.^

The adherence theory states that a pseudopodium adheres more
strongly to one side and that the endoplasm of that region, and
ultimately the whole animal, moves in that direction.

In the theory advanced by Mast (1923) ^ it is suggested that

1 Dellinger, O. P. 1906. Locomotion of Ameba and allied forms. Jour. Exp.
Z06I., vol. 13, pp. 337-358.

2 Schaeffer, A. A. 1920. Ameboid Movement. Princeton University Press.

^ Mast, S. O. 1923. Mechanics of locomotion in Ameba. Proc. Nat. Acad.
Sci., vol. 9, pp. 258-261.

24

PROTOZOA

Shell, composed of sond

Fig. 35.

Pseud o podia

Difflugia. (After Leidy.)

the moveme'tit of ameba is dependent on changes of the protoplasm
from sol to gel and back to a sol state again. (See page 4.) It
has also been suggested by Mast that form in ameba is dependent on

water content.

Digestion. — Food is ingested
directly through the ectoplasm^
and having entered the endoplasm,
minute quantities of HCl secreted
around the food mass form a gas-
tric vacuole. Carbohydrates are
not acted upon to any extent,
digestion being chiefly limited to
protein and fat. Solid wastes are
extruded at any point, the ameba
moving away and allowing the
weighty excrement to pass
through the ectoplasm. Ameba
can nip a paramecium in two, engulfing one-half, and leaving the
other half outside.

Circulation. — There is no definite distribution of food materials
but the movements of the animal thoroughly distribute the food
granules.

Respiration. — Oxygen is taken in through the whole surface of
the body, and CO2 is extruded. The contractile vacuole is also im-
portant in the interchange of gases.

Excretion. — Besides the ejection of solid feces by merely leaving
them behind as the animal moves forward, the contractile vacuole
definitely functions in the excretion of liquid and gaseous wastes.

Reproduction. — The ameba is able to divide its nuclear and cyto-
plasmic constituents equally, the process being called binaj-y fission
or division. Under adverse conditions or sometimes solely for
reproductive purposes the ameba encysts. It then forms daughter
cells which mature in about three weeks. The number produced
varies in different species.

Nervous System and Reactions. — Without nerve cells or fibers,
the ameba is still a complete neuromuscular organism. It reacts
to all sorts of stimuli, including light, heat, touch, gravity, currents
of water, chemicals, and electricity.

Tropisms. — The term "tropism" has long been used to indicate
the reaction of an animal to some sort of stimulus. A few of the

I

PROTOZOA

^5

tropisms are indicated: (i) Photo tropism, or heliotropism — reaction
to light. (2) Geotropism — reaction to gravity. (3) Rheotropism
— reaction to currents (stream pressure). (4) Thermotropism — re-
action to heat. (5) Thigmotropism — reaction to touch or contact.
(6) Chemotropism — reaction to a chemical. (7) Galvanotropism
— reaction to electrical currents.

In general we find that for any animal there exists an optimum
attracting stimulus, which we may term positive tropism (or taxis) ^
and a negative stimulus, usually the more powerful one. For
example, the ameba will be positively phototropic to a certain light,
but negatively phototropic to one of greater intensity.

Orders of Sarcodina. Order i. — Lobosa — (Ameba) soft jelly-like
— 5-200 ii. in diameter. They are found in pools of stagnant water.
Each species assumes its characteristic shape (Fig. 3 A). They are
full of granules and have one or more nuclei and a contractile vacu-
ole. They reproduce by simple fission, by sporulation, and rarely
by conjugation.

Order 2. — Foraminifera. They have a test or shell full of
openings, through which project filose pseudopodia. They are
chiefly marine, varying in size from microscopic to two inches in
diameter. Their shells are calcareous, siliceous and chitinous
(horny). There are 120 species of Foraminifera in English chalk
clifi^s. The Norfolk chalk measures are 1,450 feet thick. Globi-
gerina ooze forms gray chalk which is deposited on the bottom of the
ocean to depths of 2,500 fathoms. They reproduce by motile swarm
spores and by binary fission. Sometimes young with shells are
formed in the terminal chamber of the adult. The nummulites, the
largest of the foraminifera, are as large as a silver dollar. The
limestone pyramids of Egypt are full of nummulites.

Order J. — Heliozoa are mostly found in fresh water. They have
fine stiff radiating pseudopodia. Some have skeletons of delicate
siliceous spicules. Some species are colonial. Reproduction is by
fission^ spore-Jorrnation and by conjugation (Fig. 4).

Order 4. — Radiolaria are all marine. They differ from Heliozoa
in having a much more elaborate skeleton of siliceous or other
mineral substance. They have a central capsule surrounding the
nucleus. They are united to form colonies of various shapes in some
groups. Fossil radiolaria are found in slate, flint, chalk and deep
sea deposits.

26

PROTOZOA

Reproduction. — {a) Binary fission. The nucleus divides first,
then the central capsule, then the extra-capsular tissue, {b) Spore-
formation. The intra-capsular protoplasm divides into small

^' Egested particle

Nucleus

Con f roc tl/e vacuole

Fig. 4. Actinosphaerium, a Heliozoan. (Drawn by H. N. Lammers. After Leidy.)

masses, each of which becomes a flagellula with a single flagellum.
Sometimes the spores produced are alike, in others they are di-
morphic some being microspores and others megaspores.

Symbiosis of Radiolaria. — Radio-
laria and algae (yellow cells) live in
symbiotic relation. (See page 482.)
The radiolarian supplies CO2 and N
waste. The alga gives off O and
makes sugar.

P arasitic S arcodina. — Lambl
(i860) discovered an organism in
feces of a child and decided that it
was connected with diarrhea, but
later rejected this opinion. Later
(Afte7calkTns757o%;;'7/irPro- Lewis and Cunningham (1870) found
tozoa. Courtesy of Lea and amebae in the feces of nearly 20 per
Febiger.) cent of cholera patients examined in

India. They were not the cause of
cholera, however. Other investigators found two species of ameba
in the intestine of man, one harmless, Entameba coli^ one causing
dysentery^ Entameba histolytica (Fig. 5).

E-ndosome —-

Cor lex of

chromalin

Fig. 5. Endamoeba intestinalis.

PROTOZOA

27

Entameba buccalis {gingivalis) , found in the mouth around carious
teeth, is considered one of the causes of Pyorrhoea alveolarisJ^

Class 2. Mastigophora (Flagellates). Type of Group — Eu-
glena. — Certain intermediate forms called Mastigamebae (Fig. 7)

...Girdle
-- Tooth

!l7"ii Longitudinal

Flagellum

.Tentacle

Fig. 6. Noctiluca scintillans, postero- ventral view. (Courtesy of C. A. Kofoid.)

have not only the changeable shape and pseudopodia of the ameba,
but are provided with a flagellum in addition. There is apparently a
direct evolution from the pseudo- /

podium to the flagellum.

The true flagellates may have
one or more flagella. Some-
times one flagellum is used for
locomotion and another as an
anchor. Some forms have cellu-
lose tests and some are without
any shell or case. One group of
marine flagellates have siliceous
skeletons similar to those of the
Radiolaria. Reproduction is by
simple longitudinal division.

' FlocjeUum

„V(/> P^eudopodi-um

Fig. 7.

Mastigameba aspera. (Calkins.
After F. E. Schultze.)

Sometimes encystment occurs.

Euglena is a green flagellate found in fresh water associated with

3 Kofoid, C. A. 1929. The protozoa of the human mouth. Jour, of Paras., vol.
15, pp. 1 51-174.

28

PROTOZOA

Profoplosmic

Jnclusion

F/oge//um

Bleph aroplas t
Eyespo t

Reservoir

Other protozoa and with many of the algae. At times used in
elementary courses by botanists, since it furnishes the movement
so necessary to intrigue the student, it is unquestionably a plant-
animal. Its shape is roughly that of a cigar and it moves through
the water by means of a flagellum (Fig. 8).

The body is covered by a cuticle, the external portion of the

ectosarc. The endosarc contains
the gullet, a reservoir, contractile
vacuoles, chromoplasts and a
nucleus.

Some authors have claimed
(apparently without observa-
tion) that Euglena does not in-
gest solid particles. The writer
has observed with a class of
thirty students a whole culture
of Euglena in the act of ingest-
ing food granules. The animal
thrives best, however, when
given abundant sunlight. It is
quite evidently one of those
Phytozoa which is able to utilize
chlorophyll as well as to ingest
solids.

The red " eye-spot " is ap-
parently composed of material
with the power of absorbing
light. Reaction to shadows
occurs in Ruglena. just he/ore the
pigment spot reaches the shaded
region. In Volvox, a colonial
flagellate, each cell has a true
" eye-spot." Strong light produces negative phototropism.

Economic Importance of Flagellates. — Uroglena not only colors
drinking water yellow, but produces a fishy oily odor similar to that
of cod liver oil. Peridinians (Gonyaulax) sometimes turn the sea
red as blood off the coasts of California, Australia and India. They
remove the free oxvgen from the water and cause suffocation of the
fish. Synura tivella produces in drinking water a bitter spicy taste
resembling that of ripe cucumbers. Dinobryon, also a colonial form,

Nucleus

— Fttramy/on body

Pyrsnoid

Fig. 8. Euglena gracilis. (Drawn by H.
N. Lammers. After W. B. Baker.)

PROTOZOA

29

has a fishy odor similar to seaweed. Cristispira is the large flagellate
found in the crystalline style of clams and oysters.

Trypanosoma gambiense^ found in Southern Africa, causes sleep-
ing sickyiess in man. It is known to be transmitted by the bite of
Glossina palpalis^ the tse-tse fly. Other species of tse-tse flies
transmit different species of trypanosomes to mammals. Try-
panosoma brucei causes the tse-tse fly disease of cattle in tropical
Africa. The Germans claim that
a drug called Bayer 205 is a
specific for sleeping sickness. A
remedy for paresis, tryparsamide,
developed at the Rockefeller Insti-
tute, has been substituted for the
German patented preparation, and
reported successful.

Leishmania transmitted by in-
sects cause Leishmaniasis or infan-
tile ulcer, and tropical ulcer. Surra
and dourine are trypanosome dis-
eases of cattle and horses.

Giardia ( Lamblia) inlestinalis,
parasitic in the duodenum of man
and the rodents, causes diarrhoea.
The parasite is specific for each
mammal.

Histo)nonas meleagridis causes
black-head (entero-hepatitis) o f
turkeys. It is a small degenerate
flagellate of the trichomonad type,
which in tissues, loses its flagella.

Symbiosis. — Symbiosis between
termites and protozoa has been
discussed by Cleveland {Science,
vol. 61, no. 1585, p. 520) who has
shown that the intestine of wood-feeding termites contain small
flagellate protozoa, which may be removed by incubation, starvation,
or oxygenation without killing the termites. Neither organism can
live very long without the other, the termites dying three or four
days after the protozoa are taken from them. Cleveland empha-
sizes the fact that oxygenation will destroy ciliates and flagellates
found in cockroaches as well.

Fig. 9. Giardia maris. AX,
axostyle; 5, blepharoplast; BB, basal
body; C, centriole; E, endosome; N,
nucleus; PL, parabasal body; RH,
rhizoplast. (Calkins. After Kofoid
and Swezy.)

30 PROTOZOA

Class 3. Infusoria. — In the Infusoria we find that the body is
provided with cilia useful in locomotion and the ingestion of food.
All Infusoria possess cilia in at least the immature condition, but in
a few forms they are replaced in the adult by tentacles.

Subclass 1. Ciliata. — Infusoria having cilia throughout life.
They have a mouth, often with an undulating membrane. They
include five orders.

Order i. Holotricha. — Primitive Infusoria with small uniform
cilia arranged in more or less spiral rows. (Examples: Paramecium^
Colpoda.)

Order 2. Heterotricha. — Infusoria in which small cilia are found
covering the body while the peristome is bordered with a spiral of
large adoral cilia. Fusion of the cilia into membranelles produces a
direct pathway to the mouth. (Example: Stentor.)

Order j. Oligotrichida. — In this order the adoral zone forms a
ring around the margin of the peristome. Cilia are greatly reduced
or absent, and membranelles are the only motile organs. There are
three families, two of which are free living ( Halteridae and Tintin-
nidae), and the third consists of parasitic forms {Ophryoscolecidae)
in the stomach of ruminant mammals. (See page 482.)

Order 4. Hypotricha. — Ciliata with a dorso-ventrally flattened
body. The dorsal surface has longitudinal rows of vestigial cilia
in the form of spines, while the ventral surface has hooks, fans, and
fringed plates. The hooked cirri act as legs. (Examples: Stylo-
nychia, Oxytricha.)

Order 5. Peritricha. — Ciliata for the most part bare of cilia,
except in the oral region, and in some species with an aboral circlet
of cilia. The peristome bears a spiral band of large cilia, which
continues around the lid-like disc marking the distal end. Many of
the Peritricha are attached by a stalk which contains a contractile
fiber. (Examples: Vorticella, Epistylis.)

Subclass 2. Suctoria {Jcinetaria, Teniae ulif era). — Infusoria
which have cilia in the young condition, but tubelike tentacles in
the adult. They have no locomotor organs except in the free-
swimming young, and are attached by a stalk. Other Infusoria are
caught by the tentacles and after the cuticle has been dissolved, the
fluid protoplasm is sucked down into the body of the suctorian.
(Examples: Podophyra; Dendrosoma, a colonial form.)

Subclass 1. Ciliata. Infusoria. Order i. Holotricha. Type
— Paramecium caudatum. — Paramecium is a slipper-shaped, ciliated

PROTOZOA

31

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32 PROTOZOA

animal found active in infusions of decaying vegetation. It is
readily obtained from hay immersed in water (Fig. lo, A and E).

The outer covering or ectosarc has at its outer edge a thin
cuticle which tends to keep the animal of the same shape although it
is able to bend laterally. An oral groove running obliquely from the
anterior end to about the middle of the body aids in producing a
spiral movement as the cilia beat. The cilia are found all over the
body in spiral lines, and are especially prominent along the oral
groove and along the anterior and posterior ends. Under the cuticle
the ectoplasm contains a layer of protective organs called tricho-
cysts. The trichocysts in Epistylis umbellaria, a peritrichous
ciliate, are found in minute capsules arranged in pairs, each con-
taining a coiled thread. They are similar to the nematocysts, which
are characteristic of Coelenterates. The endoplasm contains
vacuoles, nuclei and food balls of ingested bacteria which traverse
the endoplasm along a definite path.

Locomotion. — The cilia beating violently in unison direct the
animal forward, or reverse it, and the spiral lines give the spiral
rotation which keeps the course of the animal in a straight line.

Digestion. — The cilia lining the oral groove direct particles of
food towards the mouth, and an undulating membrane (formed by
fused cilia) forces them down the gullet and into the interior of the
animal. The same type o{ gastric vacuole characterizing the Ameba
is found in Paramecium, Microchemical determinations have
shown that dilute HCl is formed around the food particles and that
protein digestion takes place. Excretion of indigestible material
is through a definite excretory aperture, the anus.

Circulation. — As in Ameba we find no circulatory canals. The
action of the two contractile vacuoles removes fluid. Water is
taken in by the mouth with the food which is distributed in the
movement called cyclosis.

Respiration. — Oxygen is taken in, and CO2 is extruded, through
the whole surface of the animal. The contractile vacuoles aid in
gaseous interchange.

Excretion. — Indigestible material not attacked by the HCl in the
food vacuoles is extruded at once along the oral groove by the
reversal of direction of the ciliary beat and the contractile vacuoles
are supposed to aid in excretion of liquids and possibly of nitrogenous
wastes, as well as gases. The anal aperture extrudes wastes subse-
quent to digestion.

PROTOZOA

33

Reproduction. — Paramecium reproduces by simple binary fission
and frequently conjugates. Isolated daily, the offspring of a single
Paramecium have been kept running since 1907 by Woodruff of
Yale University. Over 13,500 generations have been produced by

FiffST MATURATION DIVISION OF MICRONUCLEUS

3EC0N0 AND TMIRn
DIVISION OF MICRONUCLEUS

THREE 5OMAT1C DIVISIONS OF FERTILIZED NUCLEUS

rERTIUZATlON

TWO CONSECUTIVE DIVISIONS
GIVING FOUR NORMAL CELLS

Fig. II. Conjugation in Paramecium caudatum. (After Calkins.)

division without an opportunity for conjugation with a different
line^ (Fig. 10, J and B).

* Woodruff, L. L. 1929. Thirteen thousand generations of Paramecium. Proc.
Soc. Exp. Biol, and Med., vol. 26, pp. 707-708, May.

34

PROTOZOA

isi

\-.in 0.

Conjugation. — The nuclear elements of Paramecium are of two
kinds. The nutritive or somatic nucleus (macronucleus), consider-
ably larger than the reproductive or sexual nucleus (micronucleus),
is responsible for the meta-
bolic activities of the animal.
If a Paramecium is cut in
two, the part containing the
two nuclei will survive, but
the other half will die. The
reproductive nucleus as-
sumes importance in conju-
gation and sexual reproduc-
tion and the nutritive nucleus
then temporarily disappears
(Fig. 1 1 ) . Parameciu7n aurelia
has two reproductive nuclei.
Preliminary to conjuga-
tion the oral surfaces of two
animals are united by a pro-
FiG. \iA. Lacry- toplasmic bridge. The re-
maria sp. productive nucleus goes

through the maturation pro-
cess, divides twice formingfour gametes, three of
these degenerate, the survivor divides, forming
a resident/^;w«/^ pronucleus and a j-;;2^//migrant
male pronucleus . Each male pronucleus passes
across the protoplasmic bridge into the endo-
plasm of the other animal and fuses with the
female pronucleus, thus fertilizing it, forming
the zygote nucleus. After mutual fertilization,
the fusion nucleus of each animal divides by
indirect division (see p. 500 for mitosis) into
two and finally into eight nuclei equal in size.
Four of these develop into nutritive or somatic
nuclei, and four into reproductive or sexual ambiguum. (After Stem.

nuclei. Transverse divisions (simple fissions) F''^";^ Calkins 5/./o^j oj
. . . . , 1 • 1 . . the Protozoa. Courtesy 01

result m four animals, each with a nutritive L^a and Febiger )

and a reproductive nucleus.

Conjugation has been supposed to be necessary to prevent

degeneration of Protozoa, but experiments previously mentioned

i!

Fig. \iB. Spirostomum

PROTOZOA

3S

have proved that Paramecium is potentially immortal.

Nervous Systejn and Reactions. — On account of its rapid loco-
motion, Paramecium has been used a great deal in studies of be-

^^^' ^.■'••••••'-,.'ii,'^-t^

-.>..«> : b: .

^''^> ;

Fig. 13^. Chilodon. (After M. ^4- MacDougall.) 5. Colpoda cucullulus.
(After Biitschli.) C. Podophyra sp., a Suctorian. (After Calkins, Biology of the
Protozoa. Courtesy of Lea and Febiger.)

havior. Jennings has shown that Paramecium responds positively
to contact, gravity and to running water, and that its behavior with
reference to stimuli of light, chemicals, electricity and heat depends

36

PROTOZOA

upon the force of the stimulus, In some cases the reaction being
positive and in others negative.

Economic Importance of Ciliates.^ — Bursaria is said to produce
an odor in water supplies similar to that of a salt marsh. Vorticella
and Stentor (Fig. 14, A) are frequently found in "'pipe moss " and
along edges of reservoirs and dams, but are not injurious. Ciliates
clean up bacteria in sewage disposal plants.

Fig

^r Nucleus

ff~^ ^^//e/

Controcfile i/ocuo/e

Stentor sp. (After Stein. Drawn
by H. N. Lammers.)

Fig. i^B. Opalina. (After
Biitschli. Drawn by H. N.
Lammers.)

Parasitic Ciliates. — Balantidium coli and Balantidium minutum
have been found in the intestines of human beings infected with

® In considering the value of Protozoa, we must remember that they are mar-
velously adapted to laboratory experimentation. Calkins, Woodruff, Jennings, and
others have demonstrated this by a variety of fundamental studies on life processes.
Packard has studied the influence of salts on the division rate of Paramecium, adding to
our information facts which may have significance in efforts at the control of cancer.
(Packard, C. 1926. Effect of sodium on the rate of cell division. Jour, of Cancer
Research, vol. 10, pages 1-14.)

PROTOZOA 37

dysentery and are thought to be concerned with certain ulcers of the
large intestines.

Opalina (see Figure i^B) is parasitic in the intestine of the frog
(Metcalf). Several species of ectoparasitic infusoria are known to
attack fishes, causing inflammation and death. Ichthyophthirius
attacks steel-head-trout fingerlings, catfish, bass and perch. The
common stickleback is one of the carriers for the parasite.

Cyclochaeta and Chilodon are parasites of goldfish, brook trout
and small mouth black bass but apparently do not infest salmon,
steel-head trout or perch. Cyclochaeta thrives best when the
temperature of the water is low, below 50° F., but Chilodori cy print
requires a higher temperature (Guberlet).

, • ■ ' f .•

oneme around moafh
Phoryngeol boskef

\r^:^^:^-^m-^- "^ol/road track'

Fig. 15. Neuromotor apparatus of Chlamydodon. (After M. S. MacDougall. Biol.

Bull., vol. 54, p. 473, 1928.)

Class 4. Sporozoa. Type — Plasmodium vivax. — The Sporozoa
lack organs of locomotion and are characterized by their method of
reproduction by spore formation. They are all parasitic forms at
the active stages of their life cycle.

The malarial Plasmodia include three species. One, P. vivax.,
produces chill every 48 hours; another, P. malariae, causes chill
every 72 hours; while the third, P. falciparum., produces attacks
daily or at irregular intervals (Fig. 16).

Infected/d-zw^/^ mosquitoes of the Anopheline group are able to

38

PROTOZOA

transmit the organisms. The blood of a malarial patient containing
gametocytes is sucked up into the alimentary canal of the mosquito
where the gametocytes produce matured macrogametocytes (egg)

Some may be taken
into the stomach
of the niosquitowhen
it bites

luman

Development of
Parasite in

6:

InSalivary Development
Gland
(SffTlosq.

in the

rPosc^uito

'/ /In Body

' L Cavity of moscj.

'^^oscj. Storo2^^^

Fig. i6. Life history of tiie malarial organism. (After Kellogg and Doane. Courtesy

of Henry Holt & Co.)

and flagellated microgametocytes (sperm) which conjugate and form
a zygote or ookinete which grows into a multicellular somatella or
sporoblast in a cyst in the wall of the stomach. This cyst liberates

PROTOZOA

39

...e

-«

thousands of tiny sporozoites which collect in the mosquito's
salivary glands. If the mosquito afterwards bites a human being
some of the sporozoites from the wound may be introduced and will
enter the red blood corpuscles, and when sufficiently numerous will
produce a chill. Such chills occur at the end of every 48 hours with
each recurring cycle of sporulation, in the case of Plasmodium vivax.
Quinine, the specific against malaria, may be resisted by certain
of the malarial parasites in the spleen or bone marrow.

Orders of Sporozoa. Order i. Gregarinida. —
Monocystis is an abundant parasite of the seminal
vesicles of the earthworm. Porospora gigantea (two-
thirds of an inch long) is parasitic in the alimentary
tube of the lobster.

Order 2. Coccidia. — Coccidia cause red dysentery
in calves and infest the liver and intestine of man
and other vertebrates, besides oysters, insects and
Crustacea. At least five species of Eimeria occur in
chickens. One of these is very destructive to young
chickens.

Order ?. — Haemosporidia live in the blood. The

r -I- 1 T-»I J- J J U tic. 17. A

two important families are the Flasmodidae and the poiycystid

Babesidae. gregarine.

The Plasmodidae include the malaria organisms. Wasielewsky.

They induce malaria in birds and mammals. Plus- (From Calk-

modium vivax causes tertian fever, P. malariae causes ":^' '° °^/

• 1 r of the rroto-

quartan fever and P. falciparum causes tropical tever. .^^ Courtesy

Paresis has recently been treated successfully by of Lea and

infecting the patients with malaria. The organisms Febiger.)

are transmitted by Anopheline mosquitoes. (See Fig.

89.) O'Roke (1930) has found a fatal malarial disease in quails

transmitted by a degenerate fly, Lynchia, living in the feathers.

The Babesidae include several important blood parasites, all of

which are transmitted by ticks. Babesia bigemina, the organism

producing Texas cattle fever, is transmitted by the bite of the tick

Boophilus annulatus. Death occurs in acute cases in two days.

Trypan-blue has been used in the treatment of babesiasis. Babesia

canis, the organism attacking dogs, has been the most studied.

East Coast fever is caused by Babesia parva which is found in the red

blood corpuscles of cattle, producing anemia. Oroya fever is a

human disease occurring in mountain valleys of Peru. It is a

40 PROTOZOA

severe anemia associated with irregular fever, caused by Bartonella
bacillijormis.

Order 4. — Myxosporidia cause epidemics in fishes and silk worms.

Order 5. Sarcosporidia. — Sarcocystis is found in the muscles of
pig, mouse and man. It has been suggested that the larvae of flies
may transmit Sarcosporidia.

General Considerations

Protozoa are generalized single cells. They are differentiated into
ectoplasm and endoplasm. All organs of locomotion and defense
are from the ectoplasm. The seat of digestion and other functions
is the endoplasm. All Protozoa have a nucleus. There is generally
one but very often Protozoa are multinuclear. Other forms,
Infusorians, have two nuclei, one macronucleus and one micronu-
cleus. The former may be chain or dumb-bell shaped.

Locomotion. — The organs of locomotion in Protozoa are pseu-
dopodia, flagella or cilia. The ciliates are extremely speedy in
movement, while many of the flagellates scull rapidly. Shipley
found that in the case of four amebae given ten trials, the fastest
moved 0.2 of a mm. in 60 seconds, while the slowest moved that
distance in 80 seconds.

Nutrition. — Nutrition consists of capture and ingestion, digestion
and defecation. It may occur also by osmosis.

(i) Many organisms can build up complex proteins from simpler
chemical materials. There are holophytic plant-like types in which
sunlight energy is used in synthesis and saprozoic forms in which the
protoplasm is built up from organic substances in solution.

(2) Other organisms are entirely dependent on a supply of
protein ready made, obtained either by the holozoic method — by
engulfing and digesting other living organisms; or as parasites — by
feeding on digested foods. Parasites generally absorb their food in
an osmotic manner rather than by engulfing it. Some species of
Euglena are holophytic and others saprozoic. Some species in the
life of one individual are holophytic in the sunlight and saprozoic in
the dark.

Ingestion. — The ameba type is enclosing; but vortex currents are
set up by the cilia in Ciliates while the Suctoria pour their endoplasm
into an animal, digest it and then suck it through their tentacles.
Wenyon states that enzymes probably aid in liquefying the protein.

PROTOZOA 41

Digestion is always intracellular and in the endoplasm. Gastric
vacuoles contain fluids taken in with the food. Water is modified
by osjnosis to become a digestive fluid weak in HCl. At the begin-
ning of the digestive process, when food matters are first ingested,
there is a remarkable secretion of acid. This secretion ceases with
the beginning of the breakdown of food materials. Usually there
is a distinct alkaline reaction in the food vacuoles. Proteins are the
main sources of nutrition; starch is affected but slightly, but it is
claimed that the Rhizopoda dissolve starch grains and even cellulose.

Few protozoa are known to digest fats, but oil droplets and fat
bodies are found in practically all of the protozoan groups. Dawson
and Belkin have shown "^ that Ameba dubia and A. proteus are able
to digest several of the oils, including peanut oil and olive oil.

Some of the injurious bacteria may serve as excellent food for an
ameba. Rndameba coli ingests intestinal bacteria and Endameba
histolytica engulfs red blood corpuscles. Kofoid finds that a flagel-
late {Pentatrichoinonas) ingests red blood corpuscles. The majority
of protozoan parasites absorb food by osmosis. Some Ophryo-
scolecidae eat chlorophyll grains.

Excretion is by osmosis and also in the majority of Protozoa by
one or more contractile vacuoles. Contractile vacuoles are formed
in the endoplasm by accumulation of liquid. The cause of their
contraction is unknown. Probably the contractile vacuole is also
a respiratory organ. In one-half hour a protozoan throws out a
quantity of water equal to the size of its body.

Irritability. — The Protozoa are sensitive to nearly all stimuli.
There is not satisfactory evidence of color vision, although many
forms react to changes in light intensity. With regard to reaction
to the pull of gravity it is argued that this is not a true positive
geotropism (p. 25) in Paramecium. The Protozoa react to tem-
perature changes, chemical and electrical stimuli. Ameba is a
complete neuromuscular organism capable of responding to stimuli
without correlation. Reproduction in Ameba coiiijiAlA of. (i) simple
TJi^Joicm or fiooion^a). -buddrng^-Xg^-^pere formatioti^

Reproduction and Regeneration. Reproduction in the Sarco-
dina. — (i) Fusion of two amebae is said to occur, resulting in a new
organism. The significance and results of such a procedure are
unknown. Such a process has been compared to the fusion of the

7 Proc. Soc. Exp. Biol, and Med., 1928, vol. 25, pp. 790-793; and Biol. Bull., 1929,
vol. 56, p. 80.

42 PROTOZOA

sperm with the egg but no cytological proof of zygote formation has
been achieved. (2) Sporulation or encystment occurs in Ameba.
The animal becomes spherical, secretes three-layered cysts and
produces, by successive divisions of the nucleus, a multicellular
somatella containing 2, 4, 8 or more nuclei. The Ameba divides
at encystment into as many individuals as there are nuclei in the
somatella. These emerge through a pore from the cyst as amebulae
and in a few hours develop into full grown amebae. (3) Fission.
In some forms, division (binary fission) takes place during activity;
in others it takes place in a cyst. (4) Budding. In Euglypha, the
animal buds and new particles go out from the shell. Simple division
in Protozoa may lead to colony formation. (5) Conjugation in the
Sarcodina is general, except in Lobosa and an investigator thought
that he had seen it in Ameba proteus. This may have been only
agglutination. (6) There is no evidence of reorganization, or
endomixis (see page 44) in the Sarcodina.

Regeneration in the Sarcodina. — The excision of one-fourth of
the cytoplasm of the Ameba has no effect on its division. Regenera-
tion may take place in twenty-four hours and division follows nor-
mally. Enucleated amebae can move, but are not able to carry on
other body processes and soon die.

Reproduction in the Flagellata. (i) Fission. — With but few
exceptions the flagellates have longitudinal fission. (2) Encystment
and sporulation also occur at times.

Reproduction in the Ciliata.^ (i) Fission. — All ciliates have
transverse division. The reproduction of the macronucleus is
usually by direct division with little evidence of spindle formation
or definite chromosomes. In less complicated types of division,
the division of the macronucleus is relatively simple. In some forms
the macronucleus elongates, then constricts to form two equal
portions, one passing to each of the daughter cells {Paramecium,
Colpoda). When two macronuclei are present, each divides inde-
pendently of the other {Oxytricha, Stylonychia). In some types
multiple macronuclei may contain nuclear clefts with large granules
which reproduce by division. Micronuclei, if multiple in the cell,
do not fuse. The chromatin contents may be in part distributed and
then unite into a long banded nucleus. No elimination of micro-
nuclear material occurs. Each one divides by mitosis, with a

* Consult Robertson, M. 1929. Life cycles in the Protozoa. Biol. Rev., vol. 4,
no. 2, April.

PROTOZOA

43

definite number of chromosomes, (2) Conjugation is typical of the
Ciliata (see p. 23)- (3) Encystment and sporulation are characteris-
tic of many forms like Colpoda. In spore-formation there are many
simultaneous divisions.

Encystment, while characteristic of the Sporozoa, is found in ail
classes of the Protozoa. Motor organs are withdrawn and the ani-
mal forms a test or shell excluding the water, and becoming en-
cysted or fixed.

"In the majority of cases (Minchin, p. 165) an individual in the process
of encystment becomes perfectly spherical; occasionally ovoid or pear
shaped. Any food particles or foreign bodies are usually ejected or ab-
sorbed, contractile vacuoles disappear, all locomotor organs absorbed or
cast off. The protoplasm of the organism becomes less fluid and more
opaque. Lastly the cyst membrane itself appears around the body. It
stands off distinctly from the rest of the body and may vary from a soft
slimy or gelatinous coat to a firm membrane, often tough and impervious."

Protozoa in the encysted state are able to withstand drying,
freezing or sun baking. They may be transmitted by winds or
birds to a great distance. In parasitic forms, encystment is an
adaptation connected with a change from one host to another.

In the spo?'OZoan parasites y two forms of cysts are distinguishable:
I. Full grown forms may produce large resistant cysts, spherical
or oval in form. 2. Smallest forms in developmental cycle, the
products of multiple fission or sporulation, may secrete around them-
selves tough resistant envelopes, within which they may multiply
further. In this case, the envelope is the sporocyst and the entire
body a spore. " The spores of bacteria are for the most part simply
cysts, but are called spores on account of their small size " (Minchin,
p. 166).

The functions of encystment are: i. To protect during adverse
conditions. 2. For purpose of digestion after a heavy meal. 3.
Reproduction. 4. Reinfection.

It should perhaps be emphasized at this point that some ciliates
(Colpoda) divide on/y after forming a division cyst.

Regeneration in the Ciliata is a phase of growth. Ciliata with
the macronucleus (nutritive nucleus) will live since this nucleus
supervises constructive metabolism. Yet Dawson showed that
Oxytricha, lacking a micronucleus, would live for 289 generations,
from July 10, 1917, to Nov. 17, 1919, without conjugation, reor-
ganization (endomixis), or encystment.

44 PROTOZOA

If Stentor is cut into two pieces, any part containing a portion
of the nucleus will regenerate readily.

Endomixis. — There is some controversy over the significance of
the complete nuclear reorganization without cell fusion first de-
scribed by Woodruff as occurring periodically in pedigreed races of
Paramecium. At regular intervals of about 30 days, in Parameciurn
aurelia (sixty in P. caudatum) the old jnacronucleus gives rise to
buds or fragments which are absorbed in the cytoplasm. Each of
the micronuclei divides twice, which forms new products of both
micro- and macronuclei.

It is the belief of Calkins, from his investigations on Uroleptus,
that " endomixis " is a satisfactory substitute for the fusion of
different nuclei at conjugation. He holds that continued vitality
is possible when either process furnishes the necessary reorganization
of nuclear elements. Endomixis does not seem to be essential to
all ciliates. It has been interpreted as parthenogenesis.

Distribution of the Protozoa. — Even the most barren soils con-
tain Protozoa, the same species being found in tropical, temperate,
and arctic soils. The maximum numbers of soil Protozoa are found
at a depth of 4 to 5 inches, but some species seem able to live under
anaerobic conditions. Certain Protozoa thrive as internal parasites,
and live in the blood or internal organs of other animals.

The majority of the Protozoa, however, are aquatic. They are
found from the deepest seas (5,000 fathoms) to a point 10,000 feet
above sea level, Juday reported a fresh water anaerobic ciliate
found in the centrifuged plankton of Lake Mendota. It appeared
in water containing a minimum amount of oxygen. The maximum
number (95,250) appeared in a litre of water from a stratum having
no oxygen.

Pack reported 1 ciliata, 9 algae, 5 bacteria, i crustacean and 2
fly larvae in the water of Great Salt Lake which has 23 per cent
salinity. Dilution of the medium caused a shortening of the cirri
of the ciliates with increased size and activity.

Fossil Relatives and Relationship to Other Phyla. — The Fora-
minifera are of great geological importance, and are common as
fossils from the Silurian rocks down to the present time. Today
they are found in calcareous ooze, and are building beds of chalk
and nummulithic limestone.

The siliceous skeletons of the Radiolaria are found in slate and
deep sea ooze. They aid in the formation of flint. (See p. 52.)

PROTOZOA

Economic Importance of Protozoa*

Negative

45

Classes

Positive

Disease

Organism

Sarcodina

Limestone

Chalk

Flint

Amebic dysentery

End. histolytica

Flagellata

Bad taste in drinking water

Synura, Uvella, Dinobryon

Sleeping sickness

Tryp. gambiense

Dysentery

Giardia (Lamblia)
intestinalis

Tropical ulcer

Leishmania

Pyorrhoea

Endameba buccalis

Ciliata

Experimenta-
tion

Odor in drinking water

Bursaria (salt marsh smell)

Dysentery

Balantidium
Opalina

Sporozoa

Malaria

Plasmodium vivax

Coccidiosis

Eimeria

Red dysentery

Eimeria

Silk worm disease

Nosema bombycis

Encysted in muscle,

Sarcocystis

degenerate it

From the Tertiary deposits of the Barbadoes, Ehrenberg described
278 species of Foraminifera, known today.

We consider the Protozoa as the most primitive forms of animal
life. Certain forms are so closely allied to the plants that they can
scarcely be claimed exclusively by zoologists.

The Sarcodina form an ascending series from the Lobosa, with
no skeleton, up to the Radiolaria, which have well-developed
skeletons. The Mastigameba is a Flagellate with pseudopodia, and
we might consider it a connecting type between the two classes of
Protozoa. The fact that Porifera have collar cells, somewhat
resembling the flagellated protozoa, has led some zoologists to sug-
gest the evolution of Choanoflagellata into Sponges. Kofoid finds
in the colonial Dinoflagellata^ with nettling organs and eye spots,
relationships to the Coelenterata.

1 Negri bodies were at one time classed as Sporozoa, and later as Sarcodina, but
they are now grouped with various other inclusions of diseased cells, such as in tra-
choma, and sprue, as Chlamydozoa, or "mantle-covered" animals. Cowdry has even
questioned whether the granules are microorganisms. Hurst suggests (Lancet, Sept.
19, I931, p. 622) t\i3it rabies may have been transmitted in certain Trinidad cases from
humans to cattle, by vampire bats. See also Knutti, R. E., 1929, Jour. Amer. Med.
Assoc, vol. 93, p. 754.

46 PROTOZOA

References on Protozoa

BuTSCHLi, O. 1889. Protozoa, in Bronn's Tierreich.

Calkins, G. N. 1901. The Protozoa. Lemcke and Buechner, New

York.
Calkins, G. N. 1909. Protozoology. Lea and Febiger.
Calkins, G. N. 1926. The Biology of the Protozoa. Lea and Febiger.
Clarke, J. J. Protozoa and Disease. Pt. i, London, 1903; Pt. 2,

London, 1908.
Conn, H. W. 1905. Protozoa of Fresh Water of Connecticut. Bulletin

Geological and Natural History Survey of Connecticut.
Craig, C. F. 1926. A Manual of the Parasitic Protozoa of Man. J. B.

Lippincott Co., Philadelphia, Pa.
DoFLEiN. 1927. Lehrbuch der Protozoenkunde. Jena.
Leidy, J. 1879. Fresh-water Rhizopods of North America. Govern-
ment Printing Office.
Minchin, E. a. 191 2. Introduction to the Study of the Protozoa with

Special Reference to the Parasitic Forms. E. Arnold, London.
Sandon, H. 1927. The Composition and Distribution of the Protozoan

Fauna of the Soil. Oliver & Boyd, Edinburgh.
Stitt, E. R. 191 8. Practical Bacteriology, Blood Work and Animal

Parasitology, 5th edition. Philadelphia and London.
Waksman, S. a. 1927. Principles of Soil Microbiology. Bailliere,

Tindall and Cox.
Ward, H. B., and Whipple, G. C. 191 8. Fresh-water Biology. John

Wiley and Sons.
Wenyon, C. M. 1926. Protozoology, 2 vols. Wm. Wood & Co., N. Y.

Metazoa. (Gr. meta^ beyond; zoon^ animal.) — As we have al-
ready shown (page 13), the Metazoa include all the Phyla above the
Protozoa. The Metazoa begin as single cells, the fertilized eggs or
ova, but early in their embryonic life they form two or three cell
layers^ from which develop the organs and structures of the adult
animal. The germ cells are functional in reproduction, while the
body (somatic) cells carry on all other functions. To what extent
the germ cells (germplasm) may be affected by the somatic cells
(somatoplasm) and by environmental influences, is the basis of
considerable controversy. (See page 514, Inheritance of Acquired
Characters.) The somatic cells form tissues^ the discussion of
which is deferred to a later chapter. (Page 426.)

CHAPTER III

PORIFERA

PoRiFERA (Lat. porus, a pore; ferre^ to bear) were originally
classed as colonial Protozoa. Found attached to rocks and other
submerged objects, they resemble sea weed and were at one time
considered as plants. With the exception of one family they are
found in salt water.

While sponges may reproduce by eggs and sperm, they com-
monly reproduce by budding, colonies sometimes reaching a diam-
eter of three feet. It is possible to cultivate them artificially since a
complete sponge will develop from a single isolated cell.

There are three kinds of sponges, the horny sponge used in com-
merce, the siliceous sponges and the calcareous sponges, the last
named having no commercial value.

Classification

Class I. Calcarea (Lat. calcarius, lime) with spicules of carbonate of

lime.
Class II. Hexactinellida (Gr. hex, six; aktiriy a ray) with siliceous

spicules, in six rays.
Class III. Demospongiae (Gr. demos, people; sponges, sponge)

having spicules of silicon, or spongin.

Characteristics

1. Sponges are the simplest Metazoa, with two distinct layers,

ectoderm and endoderm, and an undifferentiated middle layer,
the mesoglea — which is filled with spicules of siliceous, horny
or calcareous material. They are a community of cells with
relatively little division of labor.

2, There is no true coelom or body cavity, but the internal gastral

cavity or cloaca ranges from a single tube to many branched
chambers.

a. Ascon — incurrent apertures pass directly into inner space.

b. Sycon — cell layers folded — ectoderm and endoderm, central
space.

47

48

PORIFERA

c. Leucon — external opening to canals, through orifices leading
through ectoderm to endoderm. The water comes in the

incurrent canal, then
into the radial, then
to the paragastric
cavity. The radial
canals are lined with
Jiagella; all whip
down and suck the
water in.
3. The general symmetry
o f t h e embryonic
gastrula stage is re-
tained in the adult.

Distribution. — The ma-
jority of the sponges are
marine, but there are a few
fresh water forms (Spon-
gillidae). They are found
attached to rocks, sea weed
and submerged objects.
The true horny sponges are
found in shallow water, not
deeper than 450 fathoms.
Other forms are found at
great depths.

Pigment in Sponges. —
Many sponges contain pig-
jnent. The lipochrome
pigment zobyierythrin (seen
in lobsters) is common.
The green pigment of the
fresh water sponge, analo-
gous to chlorophyll, prob-
ably aids in holophytic
nutrition.

Sponges vary in color
from red brown to bright
colors with pronounced

Fig. 18. Top, commercial sponge. Center,
the finger sponge. Bottom, red sponge. (From
A. G. Mayer, SeasJiore Life. Courtesy of N. Y.
Zool. Soc.)

PORIFERA 49

iridescence. The majority are gray in color. They vary in size
from microscopic to several feet in diameter. Their shape, while
frequently cylindrical, is quite variable. They may branch to
form a network, or assume the shape of a fan, or even that of a hat-
crown. (Figure i8.)

Type of Group — Grantia. — Grantia is a cylindrical, vase-shaped
marine sponge, somewhat less than an inch in length. It is readily
obtained from submerged piles and rocks alongshore, and since it is
convenient in size for external gross study, and can readily be
sectioned, it is ordinarily studied in college courses.

External Anatomy. — Grantia has an outer or dermal layer,
consisting of epithelial cells, contractile cells, gland cells and poro-
cytes. Lime spicules and spongin fibers are formed by the sclero-
blasts, which belong to the inner portion of the dermal layer. The
body wall consists of a skeleton of calcareous spicules of which there
are four varieties, a long and a short scimitar shape, a trident shape,
and a T shape. At times other four- and five-rayed spicules are
noted.

The middle layer is a jelly-like mesoglea, with wandering ameboid
cells, which ingest, store and transport food materials. From time
to time, germinal cells are here developed from some of the wander-
ing cells, and form ova or spermatozoa. Gemmules (statoblasts)
are formed in certain species. (See p. 50.)

The inner or gastral layer lining the radial canals is made up of
" collared " flagellate cells, or choanocytes, which create currents of
water and bring inward particles of food.

Ingestion and Digestion. (Figure 19.) — Food is ingested by
specialized cells and digested as in protozoa. Some cells are for
ingestion; the flagellated collar cells are extremely important in
absorbing and taking up food. They form rather dense masses
near the nuclei. Certain cells in the mesoglea are for storage, and
still others are for nutrition. The sponges make use of detritus
coming from dead plant and animal tissues found in sea water
along the coast. Food vacuoles are formed as in the Protozoa.

Circulation. — Circulation is by means of the ameboid wandering
cells of the middle layer. Respiration is carried on by the cells of
the body wall. Excretion is osmotic by cells, and also by the ex-
pulsion of solids through the osculum.

Reproduction, (i) Asexual. — Buds may arise near the base of
the sponge and become detached as a separate individual, or in

50

PORIFERA

some sponges colonies may be formed. Budding or branching is a
common method of reproduction in sponges.

In the fresh water Spongilla and in some of the marine sponges,
the autumnal death of the adult sponge is preceded by the formation
of statoblasts, or gemmules. The mesogleal cells aggregate in a
clump, are surrounded by a firm membrane, and protected by blunt
spicules, called amphidiscs. These gemmules survive the winter,

and develop into males or
females. From the ferti-
lized eggs come the summer
generation of sponges
which produce gemmules
and die in the fall. The
gemmules serve to preserve
the race, and to disperse it
as well. They may be
desiccated for years and
then grow new Spongillae
when the water returns.

(2) Sexual. — Ameboid
wandering cells from the
mesoglea form eggs or
spermatozoa. The ferti-
lized eggs become flagel-
lated free swimming larvae,
then become fixed, pass
through a primitive gas-
trula stage, and finally de-
velop the inhalant ostia
and the exhalant osculum
of an adult. The flagel-
lated cells of the larva de-
velop into the gastral choanocytes of the adult, and the larval inner
cells develop into the dermal layer.

Nervous System. — The first clearly marked neuromuscular cells
in the Invertebrates are found in the sponges where certain " poro-
cytes " are found surrounding the pores leading to the incurrent
canals. There is no nervous receptor present, but the porocytes
contract as do the Protozoa when stimulated. This may be called
the independent-effector stage. Although the nervous system is thus

Fig. 19. Longitudinal section of a simple
sponge. 0, osculum; ip, incurrent pores.
(Parker and Haswell, Textbook of Zoology.
Courtesy of Macmillan and Co., Ltd.)

PORIFERA

51

but little developed, the sponge reacts to stimuli. G. H. Parker has
shown that the oscula (of Stylotelld) were closed in quiet sea water
and on exposure to the air and to ether. The ostia (pores) opened
in sea water currents and in fresh water and atropine, and closed in
weak ether and cocaine.

Habits. — Sponges furnish shelter for small organisms. They are
inactive (sessile) and only open and close their openings. They are
not eaten by fishes or even Arthropoda. Their strong odor and

r'

Fig.

:o. Clam shell infested with boring sponge. (From A. G. Mayer, Seashore Life.
Courtesy of New York Zool. Soc.)

taste are important aids to the spicules in keeping enemies away.
Micro-organisms that find their way through the pores are taken in
as food by the phagocytic cells of the cloaca and radial canals.
Sponges are not true parasites, but the boring sponge, C/iona,
perforates the shell of oysters and other similar forms, seeking ^ro/^f-
tion instead of food. (Figure 20.)

Enemies of the sponges are bacteria, plant parasites and a few
fish, which attack them when they are young.

Associations. — Certain species of crabs (Dromia) are masked by
sponges living as commensals, which profit by securing more oxygen.

52 PORIFERA

A compact orange-colored sponge {Suberites domunculd), of
peculiar odor, grows around the shell inhabited by a hermit crab
and dissolves the shell substance. Algae live in sy?nbiosis with some
sponges. A cuttlefish {Rossia glaucopis) (see MoUusca, p. 154) puts
its eggs in pockets in the substance of a siliceous sponge.

Economic Importance. Positive. — i . The uses of the sponge are
too well known to more than mention that they are of great im-
portance in hospitals, homes, factories and garages.

2. As an industry, sponge fisheries are of great value, probably
being worth nearly two million dollars annually. In 1926 they
brought in (Florida fisheries alone) $666,093.00.

3. The siliceous sponges form flint deposits.

Negative. — i. Sponges may kill oysters by boring into them.
(Boring sponges.)

2. They may attach to the oysters and starve them by taking the
food first.

3. They may actually reduce the oxygen of the water in their
immediate vicinity by using currents first.

4. Sometimes /r^j-A water sponges are of serious injury in that
they attach to the walls of reservoirs and water pipes, and oflFer
lodgment for fresh water mussels and Bryozoa. Various algae
accumulate and the debris lodging against the miscellaneous or-
ganisms produces a felt-like mass called " pipe-moss."

5. The United States Department of Agriculture has published
a bulletin on the reclamation of soil in Florida marshes showing that
the sponge spicules wear away the hoofs of the mules used in plow-
ing, while the shoes of the plowmen are worn through and their feet
rendered raw in one day.

Fossil Relatives. — Fossil sponges similar to existing groups have
been found in formations from the Cambrian period down. They
are chiefly found in chalk and flint.

It has been estimated that a mass of sponge skeletons may give
rise to beds of flint nodules in the space of fifty years. Siliceous
sponges derive their spicules from small quantities of silicate in the
sea water, originating from the decomposition of igneous rocks such
as granite. The sponges and the Radiolaria (see page 44) furnish
siliceous skeletons to aid in flint formation. The siliceous chalks
are the first stage in the formation of flint. There is evidence from
the casts of spicules found that the silica of sponge skeletons
actually dissolved and was then redeposited.

PORIFERA

S3

Ancestry and Relationship to Other Phyla. — Porifera are nearer
the Protozoa than are any of the other types of Metazoa. The
collar cells resemble certain colonial choano-flagellates .

While the sponges somewhat resemble the Coelenterata, in
having a fixed mode of life, in budding, and in having a large gastro-
vascular cavity, the mode of formation of embryonic layers in the
two groups shows radical dissimilarity. They are probably derived
separately from the Protozoa.

References on Sponges

Cobb, J. N. 1902. The Sponge Fishery of Florida in 1900. Report of

U. S. Fish Com.
Davis, R. O. E. 1912. Sponge Spicules in Swamp Soils. Circ. No. 67,

Bureau of Soils, U. S. D. A.
Flegel, Ch. 1908. The Abuse of the Scaphander in the Sponge

Fisheries. Bull. U. S. Bureau Fish., Vol. 28.
Moore, H. F. 1908. The Commercial Sponges and the Sponge Fish-
eries. Bull. U. S. Bureau of Fisheries, Vol. 28, part i, pp. 403,

407-1 1, 426.
Tressler, D. K. 1923. Marine Products of Commerce. Chem. Cat.

Co., N. Y.
Wilson, H. V. 1910. Development of Sponges from Tissue Cells

Outside the Body of the Parent. Bull, of the Bur. of Fish., Vol. 28,

pp. 1265-1271.
Wilson, H. V. 1911, Development ot Sponges from Dissociated Tissue

Cells. Bull, of the Bur. of Fish., Vol. 30.
Consult, also, papers by Galtsoff, P., U. S. Bur. Fish.

CHAPTER IV

COELENTERATA

The Coelenterata (Gr. koilosy hollow; enteron^ Intestine) are
aquatic, and are for the most part marine, some developing into
enormous colonies. Their bodies, especially the tentacles, bear
nematocysts or " thread cells," structures not found in other Phyla,
which are used for offense and defense. The corals, which secrete
hard exoskeletons, are the most significant economically.

Classification

Class L Hydrozoa {Gr. hudra, wa.t€:r serpent; zoon, animal). They
include fresh water hydra, marine hydroids, small jelly
fishes (Gonionemus), and some stony corals.

Class II. Scyphozoa (Gr. skuphos, cup; zoon^ animal). They in-
clude most of the large jelly fishes (Aurelia).

Class III. Anthozoa or Actinozoa (Gr. anthos, a flower; zoon,
animal). Include sea anemones, most stony corals, sea
fans, sea pens.

Characteristics

1. Radially symmetrical.

2. They have two cellular layers, ectoderm and endoderm, with a

non-cellular mesoglea, a jelly-like substance, between.

3. They have a hollow body, the central space being called the

gastro vascular cavity or coelenteron. This may be very
small (Aurelia).

4. They have stinging cells or nematocysts.

Natural History

Class I. Hydrozoa. Hydra. (Figure 21.) — Because it is so
easy to collect and keep in the laboratory, many zoologists include
Hydra in the first course in zoology. It is from 1/16 of an inch to
3/4 of an inch long, and lives in fresh water attached by one end, but
is able to move about. The body is a tube cylindrical in shape, with

54

COELENTERATA

55

a basal disk for attachment, and a ?nouth surrounded hy Jive to ten
tentacles at the other.

Reproduction. — Buds appear laterally, and during the repro-
ductive season in October the spermaries (testes) may be seen on
the anterior third of the body, while the ovaries are seen on the
posterior or basal end. Hydra eggs resemble an ameba in ap-
pearance. Buds are formed
by the outgrowth of the endo-
derm and the ectoderm, and at
first include an enteron connec-
tion with that of the parent.

The outside of the Hydra,
except the basal disc, is cov-
ered by a thin cuticle. Hydra
has two distinct cellular lay-
ers, an outer ectoderm, which
is thin and colorless, and an
inner layer, the endoderm,
which is more than twice as
thick as the outer layer and
has in it brown or green color-
ing matter depending on the
species. Between the ecto-
derm and endoderm there is
a jelly-like substance called

the mesozlea. The body and t- it j • -j- l •

"^ ■' ^IG. 21. hydra vtriats, showing testes

the tentacles are hollow, the above and ovaries below. (After Hertwig-
space being called the gastro- Kingsley, Manual of Zoology. Courtesy of
vascular cavity or cloaca. Henry Holt & Co.)
(Figure 22, A, B, C.)

The ectoderm, protective and sensory, consists of (a) epithelio-
muscular cells, inverted cones with contractile fibrils; (b) interstitial
cells, which produce three kinds of nematocysts, (i) barbed with
hypnotoxin; (2) cylindrical, with a coiled thread and no barbs, and
(3) spherical, with a barbless thread in coils; (c) glandular cells at
the basal disk, which aid in attachment. The sex cells of both
ovaries and spermaries are derived from ectodermal interstitial
cells. The mesoglea is thin, jelly-like and non-cellular. The
endoderm has large digestive cells with muscle fibrils at the base,
and with flagellae or pseudopodia projecting into the cloaca;

56

COELENTERATA

absorptive cells in the gastrovascular endoderm, and secretory cells
which are small gland cells.

Flacjellum

—ip if —Pseudopoc/ium

Fig. ^iA. Hydra, longitudinal section. (Modified from Parker. Courtesy of The

Macmillan Co.)

Nerve cells are present in hydra in the ectoderm, a few in the
endoderm. Some nerve cells are connected by processes with the
muscle fibers of the epitheliomuscular cells.

COELENTERATA

57

Ingestion and Digestion.— Yiydrz. feeds on those minute animals
that it can seize with its tentacles. It attacks them with nemato-
cysts and propels them to its mouth by tentacles. Muscular
contraction of the body walls forces the food into the lower part
of the coelenteric chamber. Some of the endoderm cells have
^ro]ect\ng pseudopodia or flagella, while others are glandular.

Digestion. — i. The secretory cells of the endoderm
furnish the digestive fluid which acts on the contents
of the gastrovascular cavity. 2. The digestive cells
with pseudopodia engulf some of the food. 3. The
absorptive cells take it in.

Nervous Systejn. — Ectodermal nerve fibers and
cells form a plexus. There are superficial
cells. Some nerve cells connected with epithc
muscular cells are motor. There are a few endo-
dermal nerve cells also.

Behavior. — Hydra attach, swing and
feed, and sometimes loop or somersault.
In response to mechanical stimula-
tion, hydra contracts at
first but, becoming ha-
bituated, gives no fur-
ther reaction, except as
it may at times move
away from the occupied
region. The righting
position is not deter-
mined in hydra by grav-
ity. It reacts to light,
temperature and chemi-
cal stimuli. I n other
coelenterates, particu-
larlv the sea anemones, one finds remarkable response to tactile
and photic stimuli.

Food. — The food of hydra consists of aquatic forms, including
an occasional mosquito larva and rarely the eggs and fry of fishes.

Ene?nies. — The chief enemies of hydra are bacteria, saprolegnia,
aquatic insects and of course fishes and crayfish.

Economic Importance. — Hydra is to some extent beneficial in
that it captures an occasional mosquito larva. Since it also devours

Fig. 225. Hydra stinging cells. (After Dahlgren
and Kepner. Courtesy of The Macmillan Co.)

58

COELENTERATA

annelids and Crustacea that are food for fishes it may be considered
injurious. Gudger has called attention to early studies of Trembley
and the more recent ones of Beardsley which indicate the surprising
ability of hydra to capture young fishes. Beardsley found that in
one of the hatcheries of the U. S. B. P., hydras averaged 131 per
square inch in certain troughs used for black-spotted trout fry and
that they were responsible for a considerable mortality among the
young trout.

—Endoderm

Mesoglea

— Ectoderm

Fig. 22C. Hydra, cross section. (After Marshall and Hurst.)

The Hydrozoa are especially interesting to us on account of their
two forms of zooids, the nutritive hydranths and the reproductive
zooids, called medusae. In many of the Hydrozoa we find alterna-
tion of generations, the asexual generation being a fixed, plant-like
colony, while the sexual generation is a free swimming medusa.

Obelia, a Hydroid. — Since alternation of generations is especially
well shown in Obelia, it is frequently used in elementary zoology
courses.

Obelia is a colonial animal that looks like a plant. It has a basal
root, the hydrorhiza, attached to rocks, wharves and to alga, which
gives off stems, the hydrocauli. The side branches from the hydro-
cauli develop hydranths, or independent zooids, like a hydra in
structure. The tentacles of the hydroid are not hollow but solid.

COELENTERATA

59

Occasionally one finds a modified hydranth which is for the purpose
of reproduction, and is called the gonangium.

The perisarc is the thick outside covering, which is hard and
chitinous. It is expanded to form the cup of the hydranth and is
then called the hydrotheca^ or in the case of the gonangium^ the
gonotheca. A shelf across the base of the hydrotheca is the support

Fig. 23. Alternation of generations in the //>'^ro/iO/^f//«. (From Shumway, Gf wra/
Biology. Courtesy of John Wiley & Sons.)

for the hydranth. The soft parts of the stem are called the coenos-
arc, and the cavities of the coenosarc open into the hydranth forming
the typical gastrovascular cavity.

The ectoderm contains nerve cells, epitheliomuscular cells and
interstitial cells with nematocysts of two or more types. The
mesoglea is an undifferentiated, jelly-like layer between the ectoderm

6o

COELENTERATA

and endoderm. The endoderm contains large feeding cells with
pseudopodia and flagella, digestive cells (gland cells), and muscle
fibers. (Figure 23.)

Fig. 24. Portuguese man-of-war, Physalia, sheltering several shepherd fish, Nomeus,
amid its tentacles. (Courtesy of American Museum of Natural History.)

Alternation of Generations {Metagenesis) in the Hydrozoa. —

In Obelia, there are two types of zooid. The reproductive one, called
the gonangium^ produces ectodermal medusa-buds along the blasto-

COELENTERATA 6i

style^ which Is a continuation of the living central portion, the
coenosarc. The medusa buds, when mature, pass out at the top
of the gonangium and develop into medusae. Some medusae pro-
duce eggs and some produce sperms. The fertilized eggs develop
into a motile stage which, after swimming around for a time, settles
down and grows into a colony similar to the parent. The colonial
form reproduces asexually, by budding, and the medusae reproduce
sexually, by eggs and sperms. The zoophyte stage begins in the
autumn, and the medusa stage in the spring, so the life history takes
one year.

Siphonophora. — While we cannot discuss all the Orders of
Hydrozoa, we will consider briefly one of the most beautiful of the
pelagic forms, belonging to the Order Siphonophora. The familiar
" Portuguese Man of War " (Figure 24) consists of a colony of
individuals illustrating the condition of polymorphism. The
ectoderm invaginates and produces a large pneumatophore or float.
From the coenosarc arise individuals functioning as sensory polyps
or feelers, and numerous retractile tentacles supplied with nettle
cells. Feeding tubes digest and distribute the food. Reproductive
zooids are also present.

Class 2. Scyphozoa. — All Scyphozoa are marine, the majority
being pelagic, i.e., swimming at the surface of the ocean. Some of
them are beautifully colored, and certain species are phosphorescent.
All jellyfishes are carnivorous, and the larger forms are able to
capture and consume fishes. In their life history alternation of
generations is found, but the asexual stage is not highly developed
and in some cases a simple metamorphosis occurs.

Type of the Group — Aurelia. (Figure 25.) External Char-
acteristics.— Aurelia is a saucer-shaped jelly fish about 4 inches in
diameter, with four distinctive gastric pouches, conspicuous because
of the orange gonads found inside them arranged along the outer
wall towards the margin. The concavo-convex umbrella has an
exumbrella only slightly elevated in comparison with Gonionemus,
and the velum is absent. Each gastric pouch has a subgenital pit.
These have no connection with the extrusion of embryos and prob-
ably are respiratory and excretory.

Digestive System. — The mouth, rectangular when distended. Is
usually collapsed In the preserved specimen. Four oral arms, folded
like a leaf, and although they are devoid of tentacles, plentifully
supplied with nematocysts, are used to transport food to the mouth,

62

COELENTERATA

and with the aid of the nematocysts on the jnarginal tentacles^ to
kill it preparatory to digestion. From the mouth leads a short
gullet, situated on the 7nanubrium. The stomach is extended at
four points into the horseshoe-shaped gastric pouches. These have
relatively thick jelly walls. The gastric pouches have many gastric

filaments^ covered with nem-
atocysts, so that even if prey
remains alive up to that point,
it can be killed.

The radial canals carrying
food to the circular canal are
of two types, the unbranched
adradial, which proceed di-
rectly from the sides of the
gastric pouches to the circular
canal, and which have no
sense organs at their ends; and
the branched canals, called
per-radial and inter-radial.
The per-radial canals orig-
inate at the corners of the

Fig. 25. Aurelia, a Scyphozon. (From
Verrill.)

mouth, between the pouches, and have a sense organ at the end
of their central trunk; the inter-radial canals branch so close
to the gastric pouches that one cannot in some cases actually see
the beginning of the lateral branching. They arise at the middle
of the outer margin of the gastric pouches, and they also have sense
organs at the end of the main trunk.

Respiration is osmotic through the entire animal; and possibly
facilitated by means of the subgenital pit. Circulation is not
vascular, merely by water currents with food in suspension. Ex-
cretion is by the extrusion of solids through the mouth, and by
osmosis. Again the subgenital pits may function. The circular
canal of some medusae communicates with the exterior by small
excretory pores at the tips of papillae. These apparently function
in the excretion of nitrogenous wastes.

Reproduction. — The gonads are situated in the gastric pouches
and the eggs or sperms are discharged, not through the subgenital
pits, but into the stomach and out through the mouth. Fertilized
eggs are frequently seen developing attached to the oral arms.
(Figure 26.)

COELENTERATA

63

Nervous System and Sense Organs. — The nervous system consists
of a plexus of nerve fibers extending over the subumbrellar surface
between the epithelial layer of ectoderm and the muscular layer.
The plexus is thickened in a ring extending around the animal near
the circular canal and connecting with the sense organs, or tentaculo-
cysts. The marginal tentaculocysts are equilibratory and olfacto-
gustatory. Adjacent to the ocellus or statocyst are found the so-
called " olfactory pits."

Fig. 26. Development oi Aurelia. First row, growth of planula to scyphostoma;
below, strobilation (separation of ephyrae): left, oral view of scyphostoma; right, two
ephyrae. (After Hertwig-Kingsley, Manual oj Zoology, after Hatschek. Courtesy of
Henry Holt & Co.)

Class 3. Actinozoa (Anthozoa). Sea Anemone. — The Actino-
zoa include numerous species of sea anemones and corals. Sea
anemones are solitary animals, forming no permanent colony.
They are fleshy, with no skeleton.

Anatomy of the Sea Anemone. — The sea anemone is cylindrical,
with xx.^ peristome covered with hollow, horn-shaped tentacles, bear-
ing nematocysts. The mouth is provided with a muscular ciliated
groove, the siphonoglyph, which aids in holding and propelling the
food. George Meredith said, " Sea anemones are flowering stomachs
which open to anything and speedily cast out what they cannot con-

64

COELENTERATA

sume." The gastrovascular cavity is divided by thin double mesen-
teries into six radial chambers. Other shorter mesenteries, not at-
tached to the digestive tube, incompletely divide the cavities still
further. Near the base of the coelenteric chamber (gastrovascular
cavity) there are two types of mesenterial filaments. The first are
secretory in function, while the second, the acontia^ are provided with
gland cells and nematocysts. The acontia may be shot out through
the body wall of an irritated anemone until the mass of white threads
conceals the bottom of an aquarium jar. Italians eat certain sea
anemones, terming them " ogliole."

Fig. 27, Corals. (Courtesy of American Museum of Natural History.)

Corals. — The coral polyps resemble the sea anemones in their
internal structure, having an esophageal tube, mesenteries, and
internal gonads. Unlike the anemones, they form colonies^ and have
leathery, calcareous, stony, or horny skeletons of ectodermal origin.
In the red coral, originally separate spicules become embedded
in a cement-like deposit of calcium carbonate, forming a hard
branched rod which serves as an axis for the colony. Members of a
coral colony are connected, each individual securing its own food.

COELENTERATA

65

however. In one group of stony corals, the zooids are differen-
tiated, certain smaller individuals, the siphonozooids, lacking
longitudinal muscles, tentacles and gonads. Red coral is fashioned
into jewelry for children, while the white and rose pink Japanese
corals bring high prices. (See page 70.)

The living polyps are significant since they may become the
foundation of islands, or protective barrier reefs (Figure 28), but
frequently menace shipping when they grow to a point just below

Fig. 28. Great Barrier Reef of Australia. (Courtesy of Amer. Mus. of Nat. Hist.)

the surface. In general, the corals that build reefs are found in a
zone extending about 30° on each side of the equator. For the
most part, since they cannot live in water below a temperature of
about 60°, corals are found in tropical waters, near the coast, ranging
no lower than 20 fathoms, and never found in brackish or fresh water.
Formation of Coral Islands. — Charles Darwin suggested that an
island surrounded by a coral reef might subside,^ thus accounting
for an atoll and its enclosed lagoon. (See Figure 29.) Sir John
Murray and A. Agassiz have staunchly supported the erosion theory.
According to this theory coral reefs form around an oceanic island.
The reef grows but the soil and rock of the island are washed away
until an atoll with its lagoon are left. The few lagoons that serve

^ Davis, W. M., 1928, in his book The Coral Reef Problem, Am. Geog. Soc, agrees
with Darwin. The glacial control theory of Daly is the only serious rival to the sub-
sidence theory.

66

COELENTERATA

as safe harbors for ships do not offset the many dangerous coral
reefs that threaten ocean shipping.

Fig. 29. Whitsunday Island in the South Pacific, an atoll built by corals. (After

Darwin.)

Ctenophora. — The Ctenophora (Gr. ktenos, of a comb; phoreo, I
bear) are free-swimming marine animals, extremely transparent,
and for the most part found in tropical seas, although quite gen-
erally distributed. They are called sea walnuts or comb jellies.

(Figure 30.)

They are of little importance
except as food for other marine
animals. The U. S. Bureau of
Fisheries has, however, reported the
appearance of great numbers of
Ctenophores coincident with the
disappearance of oyster larvae in
Great South Bay. Formerly known
as destructive to molluscan larvae,
there have been a number of years,
1917, 1921, 1927, when heavy
" sets " of young oysters were lost
during the month of June. Prob-
ably certain temperature conditions
were responsible for the appearance
of the Ctenophores at a date earlier
than usual, and at a time when they could do damage to young
oysters. It is of course also barely possible that the temperature
changes were injurious to the oysters, and that the injury done by
Ctenophores was correspondingly less.

Fig. 30. Mnemiopsis, a Ctenophore
(Courtesy of T. C, Nelson.)

COELENTERATA 67

General Consideration of the Coelenterata

Distribution. — The majority of the Coelenterates are found in
salt water, where they are extremely numerous. The common
fresh water hydra and a species of fresh water medusa are the only
inland types.

Anatomy. — All Coelenterates have a body wall consisting of two
layers of cells (ectoderm and entoderm) and an undifferentiated
mesoglea. Digestion and circulation take place in a single coe-
lenteron. Muscle fibers aid in the process of locomotion. Loco-
motion is active in the jelly fishes like Gonionemus, which ejects
jets of water, but less rapid in the larger jelly fishes, which execute
undulatory movements. Hydra loops and somersaults.

Physiology. — Digestion is largely extracellular in some coe-
lenterates, the enzymes being discharged into the gastrovascular
cavity. In others it is an intracellular process. The endoderm
cells responsible for digestion and absorption are ameboid in
character, in some cases apparently fusing to form a syncytium.
In many Coelenterates, cilia or flagella bring about a slow circulation
of the liquid, which may be termed gastrovascular circulation.
Tryptic ferments found in some Coelenterates probably furnish an
acid secretion as in protozoa. Digestion of animals with a chitinous
covering is effected in the anemones by mesenterial jilmnents which
penetrate to all parts of the body and there digest and absorb food
matters. There is little or no evidence of free existence of pro-
teolytic enzymes in the gastral cavity. Glandular cells empty their
secretion into the gastric cavity, where it becomes liquid and
evidently has a part in what may be termed predigestion of food.
Products of this early digestion may be, and doubtless are, carried
to the most distant parts of the body by a sort of circulation, some-
times termed gastrovascular. This group appears to present a
sort of transition between purely intracellular digestion as it appears
among the protozoa and purely extracellular digestion found in
higher animals.

Respiration and excretion are performed through the body wall
and solid wastes are extruded through the mouth.

Nervous System. — In the Coelenterates we find that specialized
ectodermal cells receive and transmit stimuli to internally situated
contractile cells. The nerve net consists of a diffuse network be-
tween the receptor and effector cells. Parker ^ calls the units of

^Parker, G.H. 1919. Elementary Nervous System. J. B. Lippincott Co., N. Y.

68 COELENTERATA

this nerve net protoneurons . There are sense organs for equilibra-
tion, touch, visual sense and gustation.

Reproduction is asexual, by fission and budding; and sexual,
by ova and spermatozoa. Hermaphroditism and separate sexes
are both found. Many species of Coelenterates give off medusae
when not a month old. Their life cycles may be completed in three
months. Sagartta completes its life cycle in about 15 months. The
sea anemones may undergo pedal " laceration," which is asexual
reproduction.

Size. — Hydrozoa are mostly of small size. The Scyphozoan
jelly fishes are larger, Cyanea arctica reaching a diameter of 12 feet
with tentacles nearly 100 feet long. The largest reef anemone,
Discoso?na, an Actinozoan found in the Mediterranean Sea, reaches
a diameter of 1 feet.

Habitat. — A little hydroid lives in the mouth of the tube of the
worm Sabella. Stylactis^ another hydroid, lives on the skin of the
rock perch, Minous minot. Stylactis vertnicola attaches to the worm
Aphrodite at 2,900 fathoms. Scyphozoa have been found at a
depth of 2,000 fathoms.

Regeneration. — The remarkable ability of Hydra to regenerate
has been known since the experimental work of Trembley in 1744.
The hypostome with the tentacles will produce an entire new Indi-
vidual, and as many as seven heads have been produced by splitting
the animal anteriorly. Hydra may be turned Inside out and become
normal in a short time. It was at first thought that the ectoderm
cells were transformed into endoderm. This Is not so, however.
The animal either turns Itself back or else the inturned ectoderm
disappears and new ectoderm forms from the lips downward, cover-
ing the endoderm.

Interesting experimental work has been done by several investi-
gators with various Scyphozoa Including Aurella. They regenerate
remarkably when segments are cut out.

Fossil Relatives. — Hydrozoa are found as fossils from the Cam-
brian to the present. Scyphozoa are 99 per cent water and so few
traces remain In the rocks. Lithographic slates, found In the Juras-
sic strata of Bavaria, show the impressions of the thin soft bodies
or tentacles of jelly fishes. Sometimes the digestive cavity was
filled with sand and covered by other mud or sand before the body
of the jelly fish disintegrated and so the outline of the containing
cavity was preserved. Actinozoa or Anthozoa are found from the

COELENTERATA 69

Cambrian to the present. Corals are composed of CaCOa and so
are well preserved. Sea anemones and Ctenophores are not
preserved as fossils.

Ancestry and Relationship to Other Phyla. — The lowest Coe-
lenterate form known is the simple hydrozoan polyp, represented by
Hydra and by the hydrula stage of many Hydrozoa. Scyphozoan
polyps are represented by the scyphula of Aurelia, which is more
complex because of the stomodaeum, gastric ridges and filaments.
The Actinozoan polyp or actinula is more complex still.

The hydroids have adopted asexual multiplication by budding
during the larval stage. Certain of the zooids become medusae^ the
rest retaining the polyp form and furnishing nourishment for the
asexual colony.

The relationships of the Ctenophora to other Coelenterata are
doubtful. While the absence of stinging capsules and the presence
of collared endoderm cells in the Porifera places them in a separate
Phylum, it is assumed that they were derived from the Protozoan
ancestors of the Coelenterates.

Economic Importance of Coelenterates

Hydrozoa. — Hydra is an enemy of mosquito and other insect
larvae, but of relatively small importance in such a role. It also
attacks trout fry. Hydra is an enemy of annelids {Tubifex) and
small Crustacea such as Daphnia, which are important food for
fishes. The hydroids are food for fishes. Polypodium is in early life
parasitic on the eggs of the sturgeon. Scyphozoa are eaten in Japan
and the Philippines, preserved in salt or between oak leaves.
Sertularia are sometimes sold as " air-plants."

Actinozoa. — Sea anemones have been used as food by the Italians
for many years. They are sold under the name of " ogliole."
When fried in oil they are said to be very palatable. In the West
Indies, a coral-like form called the " sea-ginger " is esteemed as a
condiment.

Corals are the only Coelenterates of great importance economi-
cally. Coral reefs are formed by the limestone secretions of in-
numerable animals resembling anemones somewhat in structure.
Sometimes reefs of coral surround islands which submerge (Darwin's
theory, page G^) and leave a " lagoon " that proves a safe haven
for ships. But, in many cases, reefs are dangerous liabilities in

70 COELENTERATA

ocean travel. Many Pacific Islands are formed entirely of coral
rock, while the East Coast of Northern Queensland is bounded for
1,250 miles by the Great Barrier Reef, which extends parallel to the
coast at a distance from shore ranging from 10 to 90 miles. (See
page 65.)

The precious corals have been known for centuries. In India,
coral is used as a gift to the dead to keep evil spirits away from the
bodies. Pure white Japanese coral necklaces are extremely valu-
able, those with pale pink tints bringing as much as $5,000. The
finest rose-pink coral brings from $400 to $600 an ounce, but the
ordinary red pieces bring only about $10. The small fragments used
in children's necklaces bring about ^oi. a string.

References on Coelenterates

Hargitt, C. W. 1 901. Synopsis of the Hydromedusae of North
America. American Naturalist, vol. XXXV.

Trembley, a. 1744. Memoires pour servir a I'histoire d'un genre de
polypes d'eau douce a bras en forme de cornes. Leyden. (Re-
markable first study of Hydra.)

CHAPTER V

Platyhelminthes

The Platyhelminthes (Gr. plains, broad; helminthus, an intes-
tinal worm) are soft bodied, bilaterally symmetrical and dorsi-
ventrally flattened worms lacking the true segmentation character-
istic of the earthworm. The majority of the Turbellaria are free
living, the Trematodes are all ectoparasites or endoparasites, and
the Cestodes are all endoparasitic. Some parasitic flatworms re-
quire several hosts in order to complete their life history.

Platyhelminthes have two embryonic layers, the ectoderm and
endoderm. They differ from higher worms in that they have no
coelom. A packing tissue, the mesenchyme, forms a compact mass
oi pa7-enchyma (connective tissue) occupying the space between the
organs and the body wall. The majority are hermaphroditic, i.e.,
with the gonads of both sexes in one individual. The digestive
tract, when present, is a coelenteron with no anal opening.

Classification

Class 1. Turbellaria (Lat. turbo, I disturb), Planaria.

Class 2. Trematoda (Gr. trema, a pore; eidos, resemblance),

Distomes, liver flukes.
Class 3. Cestoda (Gr. kestos, girdle; eidos^ resemblance), tape

worms.

Characteristics

I. Flattened dorsiventrally.
1. Bilaterally symmetrical.

3. Do not bud to form a colony, but do form linear chains (tape

worm).

4. Lack a coelom, the spaces between the organs and body wall

being occupied by connective tissue called parenchyma.

5. Excretory system of paired branched proto-nephridia or flame

cells, connected in a water vascular system.

6. Nervous system consists of a supra-esophageal ganglion with main

ventral nerve trunks.

7. Have two embryonic layers.

71

72

PLATYHELMINTHES

Natural History

Class I. Turbellaria. — Turbellaria are unsegmented worms,
living in fresh, brackish or salt water or moist earth. They are
elongated and flat, and antero-posteriorly differentiated, with two
prominent eyes. They vary in color from transparent to red, gray,
brown and almost black. Some {Planaria maculatd) are spotted.
Locomotion is by undulation and by means of cilia. (Figure 31.)

5ra/n

Eye
■ Ovory

YolR (glands

In^esfine

-Lofero/ nerve

Vos deferens-

Genital pore'

1- Pharynx

~Infes//'ne

■ Mouth
Penis

Oviduct
Vocjina

Fig. 31. A Planarlan worm. (From Lankester, after von Graff.)

Planarians vary in size, but do not usually exceed one-half inch
in length. Some greenhouse and tropical tree planarians are over a
meter in length. They are widely distributed in fresh or salt water,
but only a few are pelagic. They usually live free but are sometimes
found in a state of commensalism, as for example Bdelloura, which
lives in the gill books of the horseshoe crab, Limidus. Planaria are
dorsiventrally differentiated and have eye-spots and ganglia. The
lappets, antero-laterally situated, are olfacto-gustatory organs.
The ectoderm is ciliated, often glandular, and equipped with rhab-
dites, rod-like bodies capable of being discharged on irritation.
Turbellaria with a branched digestive tract are called Dendrocoela,
and those with a straight digestive tract are called Rhabdocoela.

PLATYHELMINTHES 73

Type of Group — Planaria. Anatomy of P. maculata. — The body-
wall consists of the ciliated epidermis basement membrane, circular
muscles, external longitudinal muscles, internal longitudinal mus-
cles, outside of the connective or packing tissue, called parenchyma.

Digestive System. — The mouth is situated at the end of a pro-
trusible proboscis or pharynx, which is midventral. The mouth
leads into a central tube which may be axial as in the Rhabdocoela,
or branch, one running towards the head, and two, postero-laterally,
towards the tail. Digestion is both intercellular and intracellular.
Irregular columnar cells and goblet cells line the digestive cavity.
The goblet cells secrete an enzyme, probably used entirely in the
digestion oi fat. Intracellular digestion begins when the columnar
cells push out pseudopodia which seize and ingest food particles,
which later appear in vacuoles. There is no anal opening and any
undigested food must be discharged from the mouth.

There are no well-developed circulatory or respiratory systems,
as the branched digestive tract distributes the food in the form of
lymph.

Excretory System. — The water vessels of the excretory system
run through all parts of the body. They consist of two main
longitudinal trunks running on the right and left sides of the body
and opening externally on the dorsal surface by means of several
minute pores; connected in front by a transverse vessel. From
each main trunk come numerous branches which give off in turn a
system of fine vessels which terminate in flame cells, which are cells
with cilia directed down the tube. Some zoologists think that they
may also be respiratory in function.

Reproductive System. — The reproductive system is hermaphroditic
(monoecious). The male part of the apparatus consists of the
testes., vasa deferentia and cirrus or penis. The testes are numerous,
rounded structures situated near the right and left borders. Two
ducts, the vasa deferentia, run backwards from the neighborhood
of the testes and unite in the middle line posteriorly. The median
duct thus formed passes into the protrusible cirrus which opens in
the genital cloaca. At the base of the penis the seminal vesicles
empty, while the ducts of the prostate glands also empty into the
canal. The female reproductive organs consist of the ovaries,
oviducts, vitelline glands {yolk glands) and the uterus, a muscular sac.
Fertilization takes place in the uterus and the eggs develop in cocoons
that are passed along the oviducts from the animal's body, producing

74 PLATYHELMINTHES

tremendous lacerations sometimes, but the tissue destroyed is
easily regenerated.

The cocoons contain about a score of eggs with several hundred
yolk cells containing food. The larva at a certain stage develops a
temporary larval mouth and gullet, and swallows the food yolk,
by which it is able to grow rapidly. The larval mouth disappears
and a new permanent mouth replaces it. The embryo is like its
parents when it leaves the shell. Adult over-nourished Planaria
undergo fission, the posterior portion quickly regenerating a head.

The nervous systejn consists of the brain, a bilobed affair with two
longitudinal nerve cords or ventral nerve chains running backwards,
and giving off, internally and externally, transverse branches which
also subdivide. The inner ones frequently anastomose to form
commissures. The brain is rather diffuse and made up of groups of
ganglion cells, nerves, and has transverse fibers connecting the nerve
cords. The animals are responsive to all sorts of stimuli, and the
eye-spots, the lateral olfacto-gustatory organs, and the anterior end
are all well supplied with nerve endings.

Food. — Planaria live upon small Crustacea, larvae of Crus-
tacea, water mites, and Rotifera, as well as on plant food such as
diatoms and algae. They are also said to attack earthworms.

Class 2. Trematoda. — The Trematoda are leaf-like parasites
with no cilia in the adult, a thick cuticle, ventral suckers, sometimes
with posterior hooks, and with a forked or branched alimentary canal
ending in blind branches, the cecae.

Type of Group. — The liver fluke, Fasciola {Distomum) hepatic a.
The adult liver fluke lives in the bile ducts of sheep, cattle, horses
and pigs, and sometimes occurs in man. It is soft-bodied, flatteneft
and leaf-like with a triangular lobe at the broader end, and with two
well-developed suckers, the anterior one being perforated by the
mouth, and the posterior one ventrally situated. The disease
" liver rot," which is especially prevalent among sheep pastured on
snail-inhabited marshy ground, has killed many millions of sheep.

Life History. — The eggs of the liver fluke are 1/180 of an inch
long, with brownish shells, having a greenish sheen. They can
develop only in water where they hatch in from four to five weeks.

The larva or miracidium is 1/125 of an inch long, ciliated, and
with a single eye, but has no gut. If the larva does not find a
snail of the right species in from eight to ten hours, it dies. Having
entered the lungs of the snail, it loses its cilia, becomes broader and,

PLATYHELMINTHES

75

Fig. 32. Life-history of Fasciola hepatica. A, "egg"; B, miracidium; C, sporo-
cyst; D, E, rediae; F, cercaria; G, tail-less encysted stage; E, adult (neither reproduc-
tive organs nor nervous system is shown), b.o. Reproductive opening of redia; c,
cercaria; E, egg; ent, intestine; g, nerve-ganglion; g.c, germ-cells; g.l, cyst-producing
gland-cells; n, nephridium (only a few of the main branches of the excretory network
are shown); n.o, nephridial opening; o.s, oral sucker; p, proboscis (extruded); v.s,
ventral sucker; y, yolk-cells. (After Kerr. Courtesy of Macmillan and Co., Ltd.)

76

PLATYHELMINTHES

as a sporocysty develops germ cells which produce embryos. These
embryos grow into rediae which have germ cells and a primitive
digestive tube including a mouth, a pharynx and an intestine but no
anus. If the weather is warm, the rediae continue to multiply in
the lungs of the snail. If it is cold they multiply for a short time
and then pass into the liver of the snail where they give rise to tailed
forms called cercariae which have an oral and a ventral sucker, and
a forked intestine with no anus. The cercariae escape from the

P'e-nis ~--.^

Ovary

Shell (j/and

Vas c/eferens

''rot sucker

Uterus

Vas deferens

- Yolk-duct

Testis

Yolk-qlonc/s-

Fig. 22- -A" adult liver fluke. (After Kerr. Courtesy of Macmillan and Co., Ltd.)

body of the snail and, after swimming about, settle down on grass,
later becoming encysted. When their plant substrate is eaten the
cercariae develop in about six weeks into adult liver flukes and travel
from the intestine of the sheep to its bile ducts. Thus from one
single egg come the larval stages, miracidia, sporocysts, rediae^
cercariae and finally many adult flukes.

The adult liver fluke is a tailless cere aria with well-developed

PLATYHELxMINTHES 77

hermaphroditic gonads. Its digestive system consists of a mouth,
pharynx, oesophagus, intestine and non-anastomosing caecal tubes.
The intestine is usually darkened by the blood and bile used as food.
The excretory syste?n consists of a main duct with four anterior ducts,
a dorsal and a ventral one on either side. The nervous system
consists of a collar around the pharynx; two lateral ganglia and one
ventral median ganglion. The male reproductive system consists of a
pair of testes, vasa deferentia near the seminal vesicle, the ejacu-
latory duct and the penis or cirrus with its sac. Tho. female repro-
ductive system consists of the ovary, oviduct, yolk glands, shell gland,
vitellarian ducts and the vagina or uterus, opening at the genital pore.

Trematode Parasites.— Some of the trematodes infesting other
mammalian hosts are likely to infest man occasionally. For exam-
ple, Fasciola hepatica has been found in the human liver. Some
are normally parasites of man.

The blood fluke Schistosojna (Bilharzia) haojiatobium is a human
parasite found in Egypt involving large numbers of troops during
the recent war. The cercaria enter the blood stream through the
skin, finding their way to the small veins of the bladder and colon
and becoming mature in the submucous tissue. They require as an
intermediate host the non-operculate fresh water snail Bulinus or
Planorbis. Developing in the liver of the snail into tubular sporo-
cysts, germ cells develop within the sporocysts into cercariae with
forked tails. These later escape from the snail and in the free state
these cercaria must find a mammalian host in forty hours or die.
When they come in contact with mammalian skin they cast off their
tails, dissolve the cells of the skin, and work their way into a lym-
phatic or the blood stream and thence to the liver where they
mature and eventually lodge in the mesenteric veins. There was
very good scientific basis for the blind worship of the Nile ibis, an
important enemy of snails. (See p. 154.)

Schistosoma japonicumy found in the Orient, is somewhat smaller
than Bilharzia. It requires as its intermediate host the snail
Katayama nosophora in Japan and Oncomelania hupensis in the
Yangtze Valley. It is quite possible that several snails found in the
United States might act as carriers for Schistosoyna japonicum but
none as yet have been found. Schistosoma cause inflammation of
the rectum and bladder. Other species of Schistosoma ^ are found
in tropical America, the West Indies and the Philippines.

3 Cort, W. W. 1928. Schistosome dermatitis in the United States (Michigan).
Jour. Amer. Med. Assoc, vol. 90, p. 1027.

78

PLATYHELMINTHES

Clonorchis sinensis^ found in China and Japan and recently-
introduced into the U. S., infests the liver of man, cats, dogs and
pigs. It is generally leaf-like in shape and has two suckers. The
eggs hatch in the operculate snail Bithynia and the cercariae leave
the snail and encyst in thirty-four reported species of fresh water fish.
Man and the other mammalian hosts acquire the infection by
eating uncooked infected fish.

Fig. 34. Cercaria and adult of Cryptocotyk lingua. (Courtesy of H. W. Stunkard.)

In Cryptocotyle lingua., studied by Stunkard,-* we have an in-
teresting illustration of what may occur with introduced species.
The snail, Littorina litto?-ea, brought with ballast to New Brunswick,
Canada, in 1855, is supposed to have carried with it the cercariae of
Cryptocotyle lingua. The metacercariae of C. lingua occur in
marine fishes, chiefly the cunner, and adults are found in the intes-
tines of fish-eating birds and mammals. Four related species have
been shown experimentally to be infective for man. (Figure 34.)
It is possible that this form, readily collected at the Marine Biologi-
cal Laboratory, Woods Hole, Mass., may be used inland just as the
nematode Metoncholaimus pristiurus is now being shipped to dis-
tant points. (See page 98.)

Class 3. Cestoda. Type — Taenia solium. — The common pork
tape worm lives in the alimentary canal of man as an adult. Its
secondary host is the pig. The adult tape worm has a well-developed

* Stunkard, H. W. 1930. The life history of Cryptocotyle lingua. Jour. Morph.
and Physiol., vol. 50, pp. 143-183.

PLATYHELMINTHES

79

" head " or scolex armed with both hooks and suckers. The pro-
glottids are budded from the neck, the oldest being at the posterior
end. The worm may reach a length of over twelve feet and have
1,000 proglottids.

An alimentary canal is not necessary on account of the parasitic
habit of absorbing food predigested. Excretory tubes end in flame
cells.

The complete reproductive system develops in each of the pro-
glottids and attains sexual maturity beginning with the 200th.
The animal is male nearer the anterior end and hermaphroditic
posteriorly. The male structures consist of testes, efferent ducts,
vasa deferentia, a cirrus and a cirrus sac.

The female reproductive system consists of the paired ovary,
the oviduct, yolk gland and duct, shell gland and duct and the uterus
and vagina. The uterus is simple until the 600th segment; then it
branches.

The egg rises in the ovary, passes into the oviduct, and is included
with the yolk cells and spermatozoa in a chitinous shell, and finally
passes into the uterus and is released by rupture of the uterus when
the matured segment is discharged. Fertilization takes place before
the shell is formed, and may be by sperms from the same proglottid.
The eggs develop into hexacanth (6 hooked) embryos while still in
the uterus. They pass out in the feces and if eaten by a pig escape
from their covering and bore into the muscles. A proscolex, which
is a cyst with the cavity filled with water, develops a head and forms
a bladder worni or cysticercus with the scolex invaginated into the
bladder. When infested pork which is not fully cooked is eaten,
man receives cysticerci, which evert and attach, by the scolex, to the
wall of the alimentary canal and develop a chain oi proglottids.

Cestode Parasites. — Echinococcus granulosus {Taenia echino-
coccus) is found in the intestine of the dog. It is the most injurious to
man of the parasites belonging to the Cestode group and is taken into
the body upon unwashed salads or in drinking water contaminated by
ova from infected dogs. The adult worm in the dog has usually not
more than four or five proglottids. When the eggs reach the ali-
mentary canal of man, cattle, sheep, and hogs, the egg shells are
dissolved and the hooked embryos bore into the liver where they
develop into cysts. The bladder-worm stage is extremely large,
sometimes reaching a diameter of seven inches. It produces a large
number of scolices which in turn produce other crops of scolices.

8o PLATYHELMINTHES

The tissues of the host wall up the bladder worm and the enlarging
bladder worm is known as a hydatid cyst.

Taenia saginata is a human tape worm which grows to a length
of forty feet, its terminal segments reaching a width of 3/16 of an
inch. The scolex has four large strong suckers without hooks. The
cysticercus stage is found in the muscles of cattle and occasionally
in dogs. It is more common in the United States than the pork
tape worm.

Taenia solium is one of the commonest tape worms of man in
Europe. It reaches a length of twelve feet. Its scolex has both
suckers and hooks. The " bladder worm stage" Cysticercus cel-
lulosae, is found normally in the muscles of the pig but also occurs
in the dog, cat, rat and man.

Dipylidium caninum is found in the dog and cat and occasionally
occurs in man. Each proglottid contains a double set of repro-
ductive organs. The cysticercus is extremely small, a fact cor-
related with its existence in secondary hosts as small as dog lice
and fleas.

Taenia serrata, the common tape worm of the dog, has the rabbit
as its secondary host. If the rabbit swallows the eggs of the tape
worm, larvae develop in the alimentary canal and bore their way
through its wall into blood vessels which carry them to the liver.
From the liver the larvae migrate to the peritoneal cavity where
they grow into bladder worms or cysticerci. When a bladder worm
is swallowed by a dog the scolex attaches to the mucous lining of the
alimentary canal by means oi hooks and suckers and buds off a chain
of proglottids.

Taenia coenurus, the dog tape worm, produces larvae {Coenurus
cerebralis) which infest the brain of cattle, sheep and deer and cause
the disease known as " staggers " or " gid." It has many segments
as an adult in the intestine of the dog, and the cystic form may reach
a size of ^ of an inch in the brain of the intermediate host.

Diphyllobothrium latum^ the broad tape worm, causes anemia in
man. Its ciliated hexacanth embryo gets into the gut of a fresh
v/ater copepod, Cyclops strenuus or Diaptomus gracilis, then is
eaten by fish in whose muscles it encysts in the form of an immature
worm known as a plerocercoid. If eaten uncooked it becomes the
adult tape worm in man. Recently immigrants from Finland and
Baltic regions of Europe have introduced this parasite in the Great
Lakes region where fish have become infected. It is believed that

PLATYHELMINTHES

8i

the severe anemia produced by this parasite is due to a toxin given
off by the tape worm and absorbed into the blood of the host.^

Although there are many parasitic flatworms to be found in
fishes, birds and mammals, there is little danger of contracting
disease if the meats are well cooked.^

A B

Fig. 35//. Tapeworm head, cp, cirrus pouch; gp, genital pore; n, nerve; ov,
ovary; sg, shell gland; /, testicles; tc, transverse canal; ut, uterus; 0, vagina; vc, ventral
canal; vd, vas deferens; vg, yolk gland. X 20. (After DefFke, 1891, pi. i, fig. 3.)
{Coenurus cerebralis.) B. A segment. (Ranson. U. S. Dept. Ag., Bull. 66.)

Remedies for Platyhelminth Infections. — While it has been
demonstrated that santonin and nicotin, in doses fatal to ascarids,
have little effect on the cestodes, we know that the tape worm,
Taenia, is more sensitive to Beta-naphthol than Ascaris. The oil of
" male fern " {Aspidium) and Chenopodium are specifics for tape
worm. They stupefy the animal, it releases its scolex, and then a
mild cathartic will remove the whole worm.

* Vergeer, T. 1928. Dipkyllobothrium latum (Linn. 1758) the broad tapeworm
of man. Jour. Am. Med. Assoc, vol. 90, pp. 673-678. Also consult: Lyon, M. W., Jr.
1926. Native case of infestation by the fish tapeworm Diphyllobothrium latum.
Jour. Am. Med. Assoc, vol. 86, pp. 264-265.

^Linton, Ed. 1912. Cestode cysts in the flesh of marine fish and their bearing
on food values. Trans. Am. Fish. Soc (References.)

82 PLATYHELMINTHES

General Considerations

Distribution. — Free living flatworms occur from the deep sea to
the surface of fresh water lakes, while parasitic forms infest animals
of all the higher Phyla.

The Turbellaria are usually free-living, consuming insect larvae
and aquatic worms and eking out their diet by means of diatoms and
algae. Some forms like the flatworm, Bdelloura, which lives in the
gill books of the king crab, are commensals, while still others are
found parasitic in the intestines of Echinoderms and worms.

The Trematoda are all parasitic, some of them attaching to the
gills of fishes by hooks and suckers as ectoparasites. Others are
true internal parasites, found in the pericardial cavity of the mussels,
the urinary bladder of Amphibia and the alimentary canals, liver
and lungs of vertebrates. Many Trematodes find molluscs neces-
sary as their secondary hosts, the commonest instance being that
of the liver-fluke and the snail.

The Cestoda are internal parasites usually found in the ali-
mentary canal and requiring another vertebrate or invertebrate as
a secondary host. Passage from one host to another is not an active
migration as in the Trematodes. On account of their extreme
parasitism we find that the Cestodes are the most degenerate of the
flat worms.

Physiology. — The Turbellaria are covered with fine vibratile
cilia which aid in respiration as well as locomotion. They have a
well-developed, branched digestive tract, and a complicated excre-
tory system consisting of water vessels which give off fine capillaries,
which terminate in flame cells. It is assumed that the excretory
system may also function in respiration. The reproductive system
is " monoecious," or hermaphroditic? The nervous system is
highly developed, consisting of central cerebral ganglia or brain,
from which proceed posteriorly two longitudinal ventral nerve
cords, with connecting nerve strands or commissures. The Trema-
toda lack cilia but have minute cuticular papillae. They have an
anterior mouth surrounded by a muscular oral sucker, while poste-
riorly is a larger ventral sucker. Other openings are the median
genital openings and the posteriorly situated excretory pore. The
mouth leads into a muscular pharynx, a short esophagus and a rather

"^ Consult Curtis, W. C. 1902. Life history, normal fission, and reproductive
organs of Planaria maculata. Bost. Soc. Nat. Hist., vol. 30.

PLATYHELMINTHES 83

large intestine which divides into two lobes, each branched into
ceca. The only external opening of the alimentary canal is through
the mouth. Excretory system and nervous system are well de-
veloped, while the reproductive organs are hermaphroditic. In the
Cestoda we find that an alimentary canal is absent, but that repro-
ductive, nervous, and excretory systems are well developed.

Behavior. — The Turbellaria have well-developed tactile, olfac-
tory-gustatory and light percipient organs, but in the Trematodes
and Cestodes little development of these functions is found. In the
green marine worm, Convoluta roscoffensis^ geotropism has been
found to fluctuate with the rise and fall of the tides, even when the
animal was moved to an aquarium. Geotropism is dependent on the
statocyst. In Convoluta and in another Turbellarian, Vortex, it is
found that the parenchyma contains symbiotic unicellular green
algae (see page 26) similar in relations to that with the yellow cells
of Radiolaria.

Regeneration. — Planaria are notable in their ability to regenerate
new parts, a single individual having been cut into one hundred
twenty transverse pieces, behind the eyes, and each piece regenerat-
ing a perfect worm. The tape worms are able to produce new pro-
glottids as long as the scolex remains.

Fossil Relatives. — Fossil flatworms are rare. They occur from
the Pennsylvanian down to the present.

Ancestry and Relationship to Other Phyla. — The Turbellaria
and the Ctenophora have possibly been derived from a common
ancestor, the bands of cilia in larval Turbellaria resembling some-
what the ciliary swimming plates found in Ctenophora. The
simplest Platyhelminthes are Turbellaria; then we come to the
Trematoda, in which the larval cercaria corresponds to the cysticerci
of the Cestoda. The form Ligula has been considered a connecting
link between the Trematoda and the Cestoda, since it has the
elongated body and multiple gonads of the tape worm, but repre-
sents only a single proglottid.

Axial Gradient Theory of Child.— Dr. C. M. Child of the
University of Chicago, after experimenting with Planaria for many
years,^ elaborated an important theory of axiate organization,
according to which there is a gradient of metabolic activity in every

8 Consult also Child, CM. 191 5. Individuality in Organisms; and Senescence
and Rejuvenescence. Published by Univ. of Chicago Press.

84 PLATYHELMINTHES

organism. Dr. Child kindly consented to prepare for this text a
brief summary, which we are privileged to print without alteration.

"Many different lines of evidence, observational and experimental,
indicate that physiological polarity of axiation in general is in its simplest
terms a gradation or gradient in physiological condition along the axis in
question involving both quantitative differences in metabolism and proto-
plasmic constitution. During development the primary gradient or
gradients may be altered, may disappear and new gradients may arise so
that the original gradients do not necessarily persist in the adult organism.
Localization and differentiation at different levels of an axis result from
the differences in physiological condition at different levels of a gradient
and are often factors in altering or obliterating the original gradient.

"The evidence also indicates that such gradients arise or originate
in the reaction of a cell or a cell mass to some environmental differential,
but after its establishment a gradient may persist through cell division or
other reproductive process and so be inherited by the offspring of such
reproduction. A gradient may be determined by the localization,
experimentally or otherwise, of a region of increased physiological activity
in a cell or cell mass. The gradient in its beginning may be nothing more
than the gradation in activity from the center to the periphery of such a
region. In consequence of growth the center of such a region may be-
come an apical or anterior end of an axis. The environmental differen-
tials which determine gradients may be of various sorts, light, electric
current, local stimulation, differential exposure to oxygen, etc., and in the
case of organ axes, buds, etc., the environmental factors determining the
gradient may consist in the relations of the part concerned to other parts
of the organism.

"The high or most active end of a gradient may exercise a physio-
logical dominance over other regions. This dominance in its more
primitive form apparently decreases in effectiveness with increasing
distance from the dominant region and if a part of the organism comes,
either through increase in size of the organism or through decrease in
dominance or certain other conditions, to lie beyond the range of dom-
inance, physiological isolation of the part results and in many of the
simpler organisms such physiological isolation may result in agamic
reproduction.

"The gradient theory has no quarrel with heredity. The gradient
merely provides the plan, the pattern, the framework, so to speak, while
the material and its possibilities are given in the hereditary constitution
of the protoplasm in which the gradient exists."

PLATYHELMINTHES 85

Class (or Phylum) Nemertinea. (Gr. nemertes, true).— The
Nemerteans are soft, contractile, chiefly marine flatworms some-
times classed with the Turbellarian Platyhelminthes. They range
in length from 5 mm. to 90 feet.

The mouth is anterior and ventral and the anus is posterior.
They have an eversible proboscis armed with stylets, indicating that
it is functional both as a tactile and an ofl'ensive or food-t'aking
organ. The digestive tract consists of an esophagus, stomach,
intestine with paired diverticula or a long cecum, and a rectum.
The circulatory system, not found in Platyhelminthes, consists of
two or three longitudinal trunks with connecting branches. The
blood sometimes contains hemoglobin. Excretion is effected
through paired and many-branched longitudinal canals which open
to the outside through pores. Most nemerteans are unisexual,
and a few are hermaphroditic. The paired gonads discharge their
products through the body wall, having no permanent genital ducts,
A few are viviparous. Development is direct or in some forms by
the metamorphosis of a free swimming larva, the pilidium (Desor's
larva). (See p. 220.) The nervous system consists of a four-lobed
brain with a pair of large lateral nerves uniting at the posterior end
of the body, a dorsal median nerve, and, in some, a ventral median
nerve. There are lateral ciliated cerebral canals related to the
dorsal cerebral lobes. Certain species have as many as two hundred
ocelli equipped with a lens and nerve, while others have two otolithic
vesicles.

Nemerteans are carnivorous, and feed on soft-bodied inverte-
brates, certain large species capturing tubiculous worms. A few
are parasitic, infesting Crustacea and mollusca, while others are
commensals in the pharynx and atrial cavities of tunicates.

References on Platyhelminthes

Fantham, Stevens and Theobald's (1920) Translation of Braun's

Thierischen Parasiten des Menschen.
Linton, E. Many papers published by the U. S. Bureau of Fisheries.
Stiles, C. W. Cestode Parasites of Man. Bulletins 25 and 28, U. S.

Hygienic Laboratory.
Stiles and Hassall. The Inspection of Meats for Animal Parasites.

Bulletin 19, U. S. Dept. of Agriculture.
Stunkard, H. W. Many papers listed in his bibliography, New York

University.

86 PLATYHELMINTHES

Consult also papers listed in standard books on Parasitology, such as
Castellani & Chalmers, Chandler, Rivas, Stitt, and Underhill.

References on Nemertinea

CoE, W. R. Synopsis of the Nemerteans, pt. i. Am. Nat., vol. 39, p.

425.
Verrill, a. E. 1892. Marine Nemerteans of New England and

adjacent waters. Trans. Conn. Acad, of Sc, vol. 8, p. 332,

CHAPTER VI

Nemathelminthes. Nemas

The Nemathelminthes (Gr. nema, thread; helmins, an intestinal
worm) or Nemas live in fresh and salt water, damp earth and moss,
and among decaying substances; many are parasitic. They are
often minute in size and some may remain viable when dried. They
vary in size from o.oi to i meter or more in length.

Classification. (Modified)

Class Nematoda

Fam. I. Ascaridae.

1. Anguillulidae

3. Strongylidae.

4. Trichuridae.

5. Filaridae.

6. Trichinellidae.

Characteristics

I. Elongate worms, many parasitic.

1. Body usually cylindroid and unsegmented.

3. A nerve ring with associated ganglia.

4. Single and paired excretory organs, and tubular gonads.

Natural History
Dr. N. A. Cobb states (Nematodes and their Relationships):

"The number of species of nematodes must be enormously greater than
is commonly supposed. It may be estimated that more than 80,000
nematode species infest the 40,000 species of vertebrates. Insects,
much infested, will add many thousands of other species. The mollusks,
crustaceans and various groups of worms are also infested and investiga-
tions continue from these species also to augment the number of known
species of parasitic nematodes.

" Numerous as the parasitic species are, it is certain that the nematodes
living free in soil and in water far out-number them; they probably con-

87

88 NEMATHELMINTHES

stitute one of the important mechanical as well as biological factors in soil
and in the bottom of lakes and oceans. Estimates based on (Dr. Cobb's)
investigations show that in the upper foot of an arable soil the numbers
of nematodes run to thousands of millions per acre."

Longevity. — When in encysted condition in grains or in the soil,
nemas may live for years. Needham found in 1743 that nematodes
in wheat ears would live for several months in a dried condition.
Baker found that nematodes dried for twenty-eight years became
active again when moistened. (Becquerel. Latent Life. Scientific
Am. Supp., vol. 82.)

Family i. Ascaridae. — In the nemas of this family the body is
thick, and the mouth has tnree lips always bearing papillae and
amphids. The males are smaller than the females and have a curved
caudal end. Numerous species attack the vertebrates and many
of the invertebrates, living as parasites in their intestines, but found
in other organs or in the body cavity. In general they require no
intermediate host.

Type of the Group — Ascaris lumbricoides. — Jscaris lumbri-
coides, the human " eelworm," is found in the human small intestine
where resultant lesions may induce the symptoms of anemia.^
Profound respiratory affections such as pneumonia may be caused
by ascarids lodged in the lungs. It has been estimated that from
10 per cent to 40 per cent of Europeans are infested with A. lum-
bricoides.

The females contain as many as sixty million eggs. After
fertilization the eggs pass out of the body of the host with the
feces. The eggs become embryonated in the soil. Such ova remain
viable for five or six years. They enter the digestive tract through
water or contaminated food. Dirt eaters sometimes take them in
and it is possible that they may also enter with unwashed vegetables.

Ascaris lufnbricoides has been found in the dog, sheep and hog.
It possibly occurs in the cat and the rat. The host relationship
of pig and human ascarids has been tested by feeding eggs of the
human ascaris to pigs. They induced respiratory disturbances but
did not become established In the digestive tract of any of the pigs.

^ Wells, Jour. Paras., vol. 17, pp. 167-182, June, I931, found that a single dog-
hookworm, a strongyle, see p. 92, may withdraw .8 cc. of blood from the host in 24
hours. The Ascaridae may be extremely injurious also. The number of nemas as yet
known and studied is relatively so small that their classification is still provisional.

NEMATHELMINTHES

89

.^\

Excretory Pore

Pharynx

-Excretory Tube

Oenito/ Pore

— t/agino

%

^--Uterus

-^4 — Ovary

Eggs of the pig ascarls did not produce mature ascarids in the mon-
key and the two human subjects. No intermediate host is required
for the development of Ascaris hwibricoides.

Anatomy.— TVq female Ascaris lumbricoides is about six inches
long. It has a slender body tapering
at both ends. The body is grayish
pink in color with lateral stripes.

Digestive Syste?n. — The month has
one dorsal and two sub-ventral lips.
The dorsal lip bears two large papillae,
each sub-ventral lip bears a small
lateral papilla and a large sub-ventral
papilla. The amphids are small pores
slightly dorsal to the lateral papilla.
Amphids are supposed to be gustatory.
The long muscular esophagus leads into
the intestine which runs throughout
the body, ending with a slightly smaller
rectum that opens at the anus. Ab-
sorption takes place through the walls
of the intestine.

Excretory System. — The excretory
system consists of two longitudinal
canals, one in each lateral chord; they
open to the exterior through a single
ventral pore near the post-pharyngeal
region. (Figure '^i^d)

Reproductive System. — The female
reproductive system consists of two
slender coiled, thread-like ovaries, con-
tinuing into the dilated uteri which join
to form a short tube, the vagina. The
sperm from the male fertilizes the eggs
in the uteri and the eggs pass out
through the genital pore, situated about
one-third the distance from the head,
a shell resisting digestive juices. The male (about 4 inches long)
has a sinale thread-like testis from which the vas deferens leads
to the seminal vesicle and thence to the ejaculatory duct which
opens at the rectum.

--Intestine

-Excretory Tub^

Fig. 36. Anatomy of a female
round worm Ascaris. (After
Shipley and McBride. Courtesy
of Macmillan and Co., Ltd.)

The eggs are covered with

90

NEMATHELMINTHES

Nervous System. — A nerve ring encircles the esophagus con-
nected to two large nerve cords, one ventral and one dorsal; with
several other lesser cords and numerous nerve strands and connec-
tives.^

Other Ascarids. — Parascaris equorum, the largest species of
Ascaridae, is found in the horse family where it infests the small
intestine. Males are eight to ten inches and females ten to twelve
inches long. This species was used by Van Beneden in his classical
study of chromosomes. It is said that one-third of the dry sub-
stance of A. megalocephala consists of glycogen.

Ascaris vitulorum infests calves, attacking the small intestine
and sometimes ascending to the abomasum. It produces diarrhea,
colic and intestinal inflammation. Ascaris ovis infests the small
intestine of sheep. Ascaris suilla {lumbricoides) infests the hog's
small intestine. If it enters the stomach it causes nausea; if it
infests the pancreas it may occlude the bile ducts and cause jaundice.
Infesting the lungs, it causes " thumps." Toxocara canis and
Toxuscaris leonina infest dogs; Toxocara mystax infests cats. As-
caridia lineata occurs in poultry, infesting the intestine. Ascaridia
maculosa (syn. Heterakis maculosa) attacks pigeons.

Enterobius (Oxyuris) vermicularis (Oxyuroidea), a white worm
called the pinworm of man, is less than J/2 inch long. The male is
2 mm. to 3 mm., the female 9 mm. to 10 mm. in length. The color
is white, the body is expanded anteriorly. Metchnikoff believed
the pinworm an important cause of appendicitis. Several con-
flicting reports have since appeared, but there is good evidence that
the eggs and larvae of the pinworm are found in diseased appendices.
Oxyuris eqiii^ the horse pinworm, is found in the rectum and large
intestine of the horse, ass and mule.

Rhabditis nigrovenosa {Rhabdiasoidea). — In this form we find
well marked the alternation of generations — hermaphroditic with
sexual. It is found in the lungs of the frog and toad in a her-
maphroditic condition. The eggs are laid and pass into the ali-
mentary canal from the lung. They develop in water or soil into a
nematode in which the sexes are separate. Fertilized eggs develop
internally and eat all but the cuticle of the mother. From a free
life in the mud they pass into the frog's lung, by way of its cuticle
and mouth.

1 For nervous system of Ascaris see Handbuch der Zoologie, v. 2, Achte Lieferung
Teil (4) Bogen 23-32, ss. 280-283.

NEMATHELMINTHES 91

Family 2. Anguillulidae.— This immense group consists of
small, thread-like nematodes which live in water, mud and soil,
and also parasitically in plants and animals.

Anguillula aceti, the vinegar eel,^ a frequent subject for laboratory-
experimentation, lives in vinegar and stale paste. Tylenchus
dipsaci {devastatrix) attacks oats, rye, clover, hyacinths, the ear
cockle of wheat and about a hundred other plants. Tylenchus
tritici attacks oats. Caconema {Heteroderd) radicicola attacks
over seven hundred plant species, including tomatoes, cucum-
bers, potatoes, turnips, peach trees, lettuce, and most other crops
and weeds. In crop rotation it is most important to keep down the
weeds.

Lije History of Caconema radicicola.— The female is pear shaped,
and about 1/25 of an inch or about one-half the diameter of the head
of an ordinary pin. More than 500 eggs may be produced by one
female. Some of these pass out to the exterior, but many remain in
the body of the mother to develop, nourished by her remains and
by egg yolk. Upon hatching, the larvae seek out roots of many
species of hosts and drill into them by means of a protrusible oral
spine. The irritation causes a swelling or tubercle, the root-gall or
root-knot. The males pass through a larval stage and shed their
skins, then travel through the root tissue, as long eelworms, pair
with the females and die. Males are 1/12 to i/io of an inch long.

Experiments showed that Heterodera schachtii, the beet-root
nema, will travel thirty feet to a bed of germinating beet seeds.

In warm climates, such as the southern states and parts of
California, soil nematodes may pass through ten generations a year.
In colder latitudes, freezing may destroy them. Their ability to
encyst themselves preserves many in cases where the soil is porous
enough to enable them to burrow deep and then encyst. Warm,
moist sandy soils favor these nemas; heavy wet soils are less affected.

Control. — The best method of removing plant parasitic nemas
from the soil seems to be by rotation of crops. A few plants, like
some varieties of wheat, millet, peanuts, rye, red-top, forw, cow-peas
and soy beans, prove to be only slightly susceptible to Caconema
{Heterodera) radicicola. In greenhouse soils, either stearn steriliza-
tion or the use of hot water is effective. In the absence of weeds,
lure-crops are used in greenhouses to advantage.

1 Consult G. Zebrowski, 1931, "Anguillula Aceti— A Desirable Nema For Type
Study." Science, vol. 74, pp. 390-391, Oct. 16, 1931.

92

NEMATHELMINTHES

Family 3. Strongylidae. — This family is of especial interest to us
since it includes the hookworm of man, the gapeworm of fowls, and
many other internal parasites infesting domestic animals. While
these parasites are ordinarily found in the digestive tract, strongylosis
may be bronchial or pulmonic, intestinal, vascular or renal. Young
animals suffer more than adults. Larvae of the hookworm cause
profound irritation as they bore through the skin of the feet into

lymph spaces.

Dictophyme renale {Eustro7Jgylus visceralis)
{S. gigas, Rud) is the largest of the Nema-
thelminths. The females may reach a length
of 39 inches. It infests the kidneys of Carni-
vora (dog), Ungulata (horses, cattle) and
even man.

Strongyloidea {Dictyocaulus viviparus)
{Strongylus tnicrurus) infests the bronchi and
air cells of cattle and causes verminous bron-
chitis. Dictyocaulus filaria infests sheep,
goats and camels, attacking the bronchi and
lungs. Metastrongylus elongatus attacks the
bronchi and lungs of hogs. Strongylus elon-
gatus paradoxus infests the fourth stomach
(abomasum) of sheep, goats and cattle.
Strongylus equinus bores through the gut into
the blood vessels and causes aneurisms in the
mesenteric vessels of the horse. Numerous
other forms infest the domestic animals. A
(After Jordan and Kel- very common parasite of the fowls is Syn-
logg, Animal Life. ^^^^Z^J trachealis (Figure 37), the " gape-
Courtesy of D. Appleton >> T L ^ • 1 r
^ r- . worm. In the tropics several cases or

human mrestation by gapeworms nave been
reported this year (1931).

Oesophagostoma radiatum forms cysts in the mucous membrane of
the intestines of cattle. 0. columbianum, the nodular worm of sheep
and cattle, produces nodules in the large intestine which have been
mistaken for intestinal tuberculosis.

Necator americanus., the hookworm of man (Figure 50, A., 5, C
and D), causes tibial ulcer and dirt eating, besides weakness from
loss of blood. The symptoms of hookworm include paleness, thin-
ness, dull skin and eyes, dry hair, weakness, a depraved appetite for

Fig. 37. Syngamus
trachealis, the^ape-worm

NEMATHELMINTHES 93

ashes, tobacco, paper, plaster. Hookworm disease may be mistaken
for anemia as the red corpuscles are deficient in number. The eggs
pass out in the feces and if allowed to get into the soil will develop
into tiny worms. Larvae of the hookworm enter the feet, boring
through the skin into lymph spaces, thence via the lymph vessels
to the veins and into the heart. The heart pumps them through
the pulmonary arteries to the lungs. From the lungs (where they
form lesions) they travel up the bronchi and trachea to the pharynx
and are swallowed down the esophagus and into the stomach and
intestine. They may come directly into the intestine from the mouth
and esophagus, if taken in with dirty water or food. In the intestine
they do not multiply, but the females continuously produce ova
remaining there sometimes for three years. Nicoli showed (1917)
that hookworm larvae will live in water for eighteen months, but
Ackert found (1924) that at the end of that time, they were no longer
infective.^ Ackert also discovered that larvae will live in water
ranging from 45° to 98° F. The similar European hookworm {Ancy-
lostoma duodenale), found first in English Egypt, is about 2/5 of an
inch long, living in the small intestine of man.

Ancylostoma braziliense., a worm infesting the small and rarely
the large intestines of the cat, dog and fox, is the cause of " ground
itch " in Southern United States. Reference has been made
(page 88) to the important study of Wells (1931) on anemia pro-
duced by the dog-hookworm.

Through the activity of Dr. C. W. Stiles, U. S. P. H. S., and his
co-workers in the Rockefeller Sanitary Commission,^ the hookworm
is now being controlled in the United States and approaching
control elsewhere. Dr. Stiles has pointed out (Scientific Monthly,
October, 193 1, vol. 2>3^ PP- 362-364) that hookworm disease is even
now one of the most important causes of backwardness in southern
school-children.

Family 4. Trichuridae. — These nematodes, placed under the
family Trichinellidae by some writers, are called the " hair necks,"
as they have a long slender anterior portion which contains
the esophagus. The head is nude and the mouth rounded. They
are oviparous.

2 Ackert, J. E. 1924. Studies on the longevity and infectivity of hookworm
larvae. Am. Jour, of Hyg., vol. 4, no. 3, pp. 222-225.

' Cort and his associates, in the International Health Board, have published more
than thirty papers on hookworm disease, chiefly in the Am. Jour, of Hygiene.

94

NEMATHELMINTHES

Trichuris trichiura {Trichocephalus trichiwis) lives in the large
intestine near the cecum of man. It does not move and is sup-
posed to be of little injury. The posterior part of the body is
threadlike, while the anterior part is much narrower and hairlike.
Related species infest the colon and cecum of sheep, cattle, dogs
and hogs.

embr

B

Fig. 38. A, Trichinella spiralis^ female. B, larvae in muscle, not yet encysted.
C, encysted larva. (From Daugherty after Leuckart. Courtesy of W. B. Saunders
Co.)

NEMATHELMINTHES 95

Family 5. Trichinellidae. (Figure 38, A, B and C.)— In the
minute Trichinella spiralis, the body is thicker posteriorly and
not so slender and filamentous anteriorly, as in the Trichuridae.
The embryos develop in the uterus and are hatched there, so that
the young are brought forth alive (viviparous).

The Trichinellidae are found in the muscles of pigs, rats, mice,
man, rabbits, guinea pigs, and dogs. They are not found in birds.
Each larval worm is encysted in an oval capsule 0.4 to 0.6 mm.
long. Cysts may number 100,000 to 125,000 per cubic inch of meat.

Life History of Trichinella spiralis. — If the cysts are eaten, the
digestive juices free the worms from the meat in which they are
encysted. They then enter the small intestine and become mature
in a few days. The female, 3 to 4 mm. long (male 1.5 mm.),
penetrates the intestinal mucous membrane and in a month gives
birth to 1,500-10,000 living young and then dies. Young are
carried from the lymph vessels through the thoracic duct to the
veins, and finally from the blood vessels they wander into the
most actively used muscles of the body, such as the diaphragm, eye-
muscles, and muscles of the neck. They destroy the sarcolemma
and become encapsulated in cysts about 1.5 mm. long. High fever
is a symptom of trichinosis. In Emmerslaben, Saxony, in 1884,
there was an historic instance of one infected pig producing serious
illness in 364 people, 57 of whom died in the space of one month.

Within the past five years, a number of fatalities have been
recorded, due to Trichinella infections, in these United States.

Family 6. Filaridae. — These extremely minute elongated worms
live in blood and lymph vessels, serous cavities of the body, and in
subcutaneous connective tissue. The males usually have a spirally
rolled tail, and the females have two ovaries. The majority of them
are viviparous. None of the family are blood suckers.

Filaria bancrojti, formerly called Filaria sanguinis hominis,
is a slender, threadlike worm, the male about 40 mm. in length and
the female about 100 mm. (4 inches). They live in the lymphatic
glarids of man, and pass from the eggs into the blood and sometimes
into the kidneys. They are supposed to cause elephantiasis by
obstructing the flow of lymph. They are transmitted by night-
flying mosquitoes. Loa loa, a smaller form, is transmitted by a
biting fly ( Chrysops), which is day-flying. Filaria perstans is trans-
mitted by a midge (Culicoides). It is essentially a parasite of the
dark skinned races, rarely attacking the whites of West Africa.

96 NEMATHELMINTHES

Filaria equina infests the serous cavities and has been found in the
aqueous humor and causes opaque cornea in the horse.

The female Guinea worm {Dracunculus medinesis) is about thirty-
six inches long and as large as packing twine. It produces abscesses
under the skin in which the worm is coiled. Embryos must enter
water and penetrate the microscopic crustacean Cyclops. The larva
reaches man through drinking water containing Cyclops. Guinea
worms occur in Asia, Africa, and tropical America.

Mermithidae. — The hairworm, Mermis subnigrescens, is a
parasite of the common grasshopper. The grasshoppers swallow
the eggs with their plant food. The hairworm Agamermis decaudata
also infests grasshoppers. Cobb and his associates have suggested
that control of grasshoppers as pests may be aided by parasitizing
them, thus causing sterility and death. They found that a high
degree of parasitism caused all developing hairworms to become
7nales and a low degree of parasitism resulted in the parasites all
being females^ with a gradient (see page 84) between the extremes,
corresponding to the degree of parasitism. The Mermithidae
constitute a very large group, others of which infest injurious insects,
such as mosquitoes, ants, cutworms, and the like.

Forms Uncertain in Position Formerly Classed with the Nema-
thelminthes — Acanthocephala. — In this group of " thorn-headed "
worms, we find a protrusible rostrum or proboscis with five or more
rows of recurved hooks. An alimentary canal is absent. An un-
paired cerebral ganglion is present.

The larva of Echinorhynchus gigas lives in the larva of the June
bug (Melolontha). The adult worm is found in the pig, attached
when full grown to the wall of the small intestine. It is dioecious,
i.e., the sexes are separate. The ovaries of the female break up into
free floating egg groups. The uterus picks up immature and fer-
tilized eggs indiscriminately, but only the elongate, shelled ones may
pass the canals; immature eggs are led by a ventral opening back to
the coelom. In E. gigas, protonephridia open beside the genital
opening. The oviducts of the female and the penis of the male are
at the posterior end.

Gordiaceae. — These minute, slender animals are commonly
known as " horse-hair worms." They have an esophageal nerve
ring, a ventral nerve cord and the female genital opening is at the
cloaca. The larvae infest insects and the adults live in water,
twining around plants and depositing their eggs.

NEMATHELMINTHES

97

Treatment of Nematosis. — A diet rich in carbohydrates is
said to lessen the damage to the liver, kidneys and adrenals that
frequently ensues from the use of carbon tetrachloride in hookworm
disease. Hexylresorcinol is also effective. (Science, Aug. 1 8, 193 1.)

In certain pioneer studies, T. B. Johnson and W. W. Hodge, in
May and June, 1913, determined the phenol coefficients of resorcinol.

Vulva —
Vat^tna

Bipolar gang/ion cells-^-
Nerve -rinq
Lateral chord — ■■-

Ovum in ejaculatory duct

Ovary with c(^cjS In

process of development

Amphidiol nerve

Excretory pore

Coudol gland

p^ £(^ in process of fertilization

— Spermatozoa

£<jq with shell

Uterine wall

C/vette

Nucleus of
Salivary glond
£soptio^us-

Cardia —
Demonian system

Rectum

i' Renette duct

— Renette CG/I

^%@S?*^^^ Intestine

— Spinneret

Fig. 39. Marine free living Nematode, Metoncholaimiis pristiurus, female. Courtesy
of N. A. Cobb. (Drawn by J. Danforth.)

ethyl resorcinol and propyl resorcinol, three of the four points on the
curve. A brief account of the work of Professor Hodge was pub-
lished in 1913, Jour. Amer. Chem. Soc, vol. 2S-> P- ioi4> but it was
not until 1921, Jour. Amer. Chem. Soc, vol. 43, pp. 348-360, that
Hodge's curve with one more point added was published.

98 NEMATHELMINTHES

As an outgrowth of this pioneer work on alkyl-resorcinol deri-
vatives, Doctor Leonard of Johns Hopkins University has developed
the internal antiseptic "hexyl resorcinol."

Thyynol in 6o-grain doses is effective in the treatment of human
helminthiasis. The active principle of oil of chenopodium, called
ascM-idole, is used in doses of 0.5 c.c. Calomel, santonin, and oil
of male fern {Aspidiuni) are beneficial in trichinosis, but not effective
after the parasites have become encysted.

Nematodes as Laboratory Material. — Certain free-living aquatic
nemas are so resistant to external conditions that they can be shipped
alive long distances, and are thus favorable laboratory material for
zoological courses in schools and colleges. Prominent among these
are species inhabiting foul mud, such as Metoncholaimus pristiurus
(marine) and its close relatives, and certain species of Dorylaimus
(fresh water). M. pristiurus have been shipped thousands of miles
both summer and winter, and used successfully.^

General Consideration of the Nemathelminthes

Distribution. — Nematodes are found from the depths of the sea
to the tops of mountains and in hot springs and Antarctic ice.
While it was formerly supposed that they were almost all parasitic,
it is now known that besides infesting animals and plants of all
species, there are very many, small, free-living species.

Physiology. — Nematodes usually have a simple digestive tract,
well-developed excretory organs, tubular gonads and a nerve ring
with sensory papillae and both dorsal and ventral nerves.

Fossil Relatives. — The Nematodes range from the upper Paleo-
zoic to the present. They are found in the Coal measures and
parasitic in insects in the Tertiary amber.

Ancestry and Relationships to Other Phyla. — The various classes
of Nemathelminthes differ and it is still very doubtful whether they
should be grouped into a single Phylum. Some of the families
formerly classed under the Nemathelminthes are now separated,
apparently resembling the Annelida.

References on Nematodes

Chandler, A. C. 1922. Animal Parasites and Human Diseases. J.
Wiley and Sons, N. Y,

* Cobb, N. A. 1 93 1. Science, vol. 74, pages 489-490.

NEMATHELMINTHES 99

Cobb, N. A. 1914. Nematodes and their Relationships. Year Book
of U. S. D. A., 1914, and many papers.

CoRT, W. W., AND Associates. (Many papers in Am. Jour, of Hy-
giene.)

Harris and Brown. 1925. Oxyuris vermicularis as a causative factor
in appendicitis. Jour. Am. Med. Assoc, vol. 84, no. 9, pp. 650-654.

Stiles, C. W. 1903. Hookworm Disease. Bulletin 10, Hygienic Lab.,
Washington.

Stiles, C. W. 1910. Hookworm Disease. Pub. Health Bulletin 32,

Washington.
Stiles, C. W. 1910. Soil pollution as cause of ground itch, hookworm

disease and dirt eating. Circ, Rockefeller Sanitary Commission

for the Eradication of Hookworm Disease.
Underhill, B. M. 1924. Parasites and Parasitosis of the Domestic

Animals. Macmillan Co., N. Y.
Ward, H. B., and Students. (See bibliography from Univ. of Illinois.)

CHAPTER VII

Annelida or Annulata

The older terminology included the Molluscoidea, the Platyhel-
minthes, the Trochelminthes, and the Nemathelminthes with the
Annelida under the general term Vermes. For several decades,
however, the Phyla have been separated.

The Annelida (Lat. annellus, a little ring) are the most highly
developed of the worms, with regularly segmented bodies, which in
most cases indicate by external annulations the metameric arrange-
ment within, which is such that the internal organs are repeated in
each segment. The head usually has a " prostomium " in front of
the mouth. (See Figure 45.)

There is usually a well-developed coelom, and an extensive
series of blood vessels. Hair-like or comb-like gills function in
respiration in some forms, while in others minute capillaries in the
skin aerate the blood. The excretory organs, called nephridia, are
segmentally arranged and the nervous system consists of dorsal
cerebral ganglia, and a ventral nerve cord with segmentally arranged
ganglia.

Classification

I. Class Archi- Annelid a (Gr. arche, beginning; Lat. anne//us, a little

ring) without setae or parapodia.
1. Class Chaetopoda (Gr. chaite, bristles; pons, foot) with setae.
3. Class Hirudinea (Lat. hirude, a leech) without setae or parapodia,

but with suckers.

Characteristics

1. Segmented worms in which the segmentation is in most cases

visible externally.

2. Appendages paired, not jointed.

3. Setae are present in the body wall.

4. The coelom usually communicates with the exterior by paired

nephridia, and pores.

100

ANNELIDA OR ANNULATA loi

5. The nervous system consists of two dorsal ganglia, connecting

commissures passing around the pharynx, and a ventral
chain of ganglia with lateral nerves.

6. The alimentary canal is well developed and usually specialized.

7. Trochophore larva found in many forms.

Natural History

Class I. Archi-Annelida. — The most primitive of the Annelida
are the Archi-Annelida, represented by two families, both marine
and exceedingly small. The family Folygordiidae includes the
sand-living form Polygordiiis. It is slightly over an inch long, with
indistinct external annulations, but a septate coelom, and metameric
development of nephridia, gonads, digestive tube and ventral nerve
cord. The larva has a trochophore stage.

The family Hist7~iodrilidae are minute parasitic worms infesting
the lobster. They have three horny jaws, a well-developed digestive
system consisting of esophagus, intestine and rectum; and have
primitive united cerebral ganglia. The sexes are separate.

Class 2. Chaetopoda. — In the Chaetopoda, segmentation is
distinct both internally and externally, and the setae are segmentally
arranged on the parapodia or sunk in pits.

Order 1. Polychaeta. — The polychaetes are chiefly marine
animals, with setae arranged in groups on the fleshy parapodia.
They have a distinct head, usually provided with sense organs.
The prostomiufn bears from one to ten dorsal tentacles and two ventral
palps, which in certain forms are broken up into long respiratory
filaments. The sexes are usually separate. Eyes are present on
the prostomium of some forms, and lithocysts in a few forms (^reni-
cola). Polychaetes are of diflferent colors, including red, blue, green,
or yellow. They usually pass through a trochophore stage. (See p.
125.)

Heterogony is present in Nereis, a small pelagic form alternating
with a large bottom living one. The palolo worms of Samoa
{Leodice viridis) come to the surface during the October full moon to
breed and are caught by the natives who use them for food.

A few polychaetes are found in fresh water; the rest are marine,
and chiefly bottom living animals, which burrow in the sand or live
in tubes. The free-living forms are predaceous; the sedentary ones
Hve on all kinds of organic matter. There are many commensals
and a few parasites. (See p. 483.)

I02

ANNELIDA OR ANNULATA

SyUidae are brightly colored forms less than an inch long, which
are frequently found associated with sponges; some have an al-
ternation of generations, in Autolytus for example (Fig. 40) an
asexual individual sending off from its posterior end buds which
become male or female.

Aphroditidae are scale bearers, the scales, called elytra^ acting
as breathing organs. Lepidonotus squamatus has twelve pairs of
elytra. Polynoe, a small form about an inch
long, has a large proboscis, with four strong jaws
and a circle of papillae. It has twelve pairs of
scales. Aphrodite, sometimes called the " sea
mouse," is about five inches long and of a bril-
liant iridescent color.

Phyllodocidae are green and usually iridescent,
with a long head which bears four pairs of short
and four pairs of long tentacles. They secrete
slime which binds mud together.

Nereidae include the common Nereis, which
may reach a length of eighteen inches. The
" clam worm," as it is called by fishermen, is
bluish green in color, and lives during the day in
burrows in the sand, but comes out during the
night, and is preyed upon by fishes.

Nephthydidae are dorsi-ventrally flattened,
elongate worms, whitish in color with a distinct
red dorsal blood vessel. They are found in sand
and mud along the shore.

Leodicidae {Eunicidae) include the Pacific
(Samoan) palolo worm, and the Atlantic palolo
worm {Leodice fucatd) of the West Indies and
the Gulf of Mexico, which swarm within three
days of the full of the July moon. (See the Sa-
moan palolo, page 118.) Diopatra is a large reddish brown worm,
found from Massachusetts to South Carolina, in long tubes which
project above the surface. Diopatra reaches a length of twelve
inches, but is difficult to capture on account of the speed with
which it hides in its tube. (Fig. 41.)

Glyceridae include forms which are smooth, about eight inches
long, and have many segments. The small conical head has many
tentacles. The long proboscis has four hooked jaws. The Seden-

FiG. 40. A sex-
ual individual of
Autolytus with
male about to de-
tach. (From Ver-
r i 11 , Invertebrate
Animals of Vine-
yard Sound.)

ANNELIDA OR ANNULATA

103

Moufh

—Peristomlal cirrus

taria lack both jaws and a protrusible pharynx. They have small

uncini, or hooked setae, and a few hair setae. Some species form

calcareous tubes (Serpula), while others use the material available,

furnishing a cement by which they bind together sand, shells, or

sea weed into protective

coverings. The Spion-

idae include a number

of small burrowing

worms with long peris-

tomial cirri curving over

the back, and with the

dorsal cirri serving as

gills. The proboscis

lacks jaws. The Chae-

topteridae include fifteen

species of short, stout

worms, which live in

parchment-like tubes.

Wino , a porapodium

Fig. 41. Diopatra cuprea.
(From Verrill.)

Fig. 42. Chaetopterus pergamentaceus. (Original
drawing by H. Lammers.)

Certain species are highly phosphorescent. Important studies in
Experimental Embryology have been made with the Woods Hole
species, C. pergaynentaceus. (Fig. 42.) In the Tej'ebellidae we find
a cylindrical body, having many similar lobes, and with well-de-

I04

ANNELIDA OR ANNULATA

veloped mucus-forming glands. Amphitrite (Fig. 43) reaches a
length of fifteen inches, and is reddish brown in color. It is found
in sand and mud at low water mark. Polycirrus (the blood worm)
is a long, slender, blood-red worm which does not form a tube, and
has no branching gills. The Amphictenidae are small worms which
form portable tubes of sand open at both ends. Cistenides {Pec-
tinarid) gouldii is a flesh-colored form found in shallow water from

North Carolina northward.
The Cirratididae are worms
with a cylindrical body, having
many similar segments with
long filamentous cirri. They
live in burrows.

Maldanidae form sand
tubes. They lack gills. Cly-
menella is one of the commonest
types. The Arenicolidae are
represented by but two com-
mon species. Arenicola mar-
ina^ called the " lug-worm,"
reaches a length of ten inches.
It has twelve pairs of branched
red gills on the central seg-
ments. It burrows as much as
two feet into the sand, but can
be located by castings at the
entrance. The Sabellidae in-
clude a number of genera.
The tentacles are rudimentary,
the palps very large. A proboscis is present. They form mem-
branous tubes in mud and sand. Example — Sabella jnicrophthalma.
Serpulidae form long contorted calcareous tubes which are found
incrusting shells. {Serpula or Hydroides^

Older 2. Oligochaeta. — These hermaphroditic annelids lack
tentacles and parapodia, and have only a few setae, projecting from
pits in the body wall. Certain oligochaetes have external gills
{Nais). The head is not distinct, but has a small projection, the
prostomiujn, and ^ peristomiuniy which contains the mouth, but lacks
setae. Paired ovaries and testes are present in each animal, and
seminal receptacles store the sperm prior to the extrusion of eggs

Fic. 43.

Tufted worm {Amphitrite ornatd).
(Drawn by V^errill.)

ANNELIDA OR ANNULATA

105

and sperm into a cocoon, which is secreted by the modified clitellum.
There is no metamorphosis. The oligochaetes are singularly lacking
in sense organs, pigment eyes being found in the Naids. We shall
mention only five of the eleven families. (Figure 44.)

Aelosomatidae are microscopic fresh water worms, whose red,
yellow and brown oil globules make them appear spotted. They
reproduce by fission, and
are considered the most
primitive oligochaetes.

Enchytraeidae are slender
small worms found in plants
and in fresh water, near the
sea shore. Their blood may
be colorless, red or yellowo
The small white form,
Enchytraeus albidus^ is re-
commended by Gamble as
exceedingly useful for obser-
vation under a binocular
microscope. It requires a
temperature not higher than
60° F.

Naidae are small, trans-
parent, aquatic forms with
a distinct head, and from

two to four groups of setae on each segment. In Nais^ a common
fresh water species, the blood is yellow or red. Eyes are usually
present. Budding is a common form of reproduction. The Tubifi-
cidae are slender reddish worms living in tubes, from which they
protrude the posterior end into the water. Many species of Tubifex
are found in brackish water; a few occupy fresh.

Lumbricidae include the common earthworms. Among them
are the familiar Lu7nbricus terrestris of Europe and America;
Eisenia {Allolobophora) foetida, commonly found in manure; and
Helodrilus^ represented in America by ten species. Aristotle called
the earthworms the " intestines of the earth."

Order 2. Oligochaeta. Fam. Lumbricidae. Type — Lumbricus
terrestris. — The earthworm is from 5 to 18 inches long, with 100 to
160 segments, strongly marked by external rings. A tropical
species, Alegascolex australis^ reaches a length of eleven feet.

Fig. 44. Nats. (From Leunis. Davenport's
Zoology. Courtesy of The Macmillan Co.)

io6

ANNELIDA OR ANNULATA

Anatomy. — At Its anterior end, Lumbricus terrestris has a pro-
boscis-like fleshy lobe called the p7'Ostomium, with a mouth imme-
diately behind it on the ventral side. The skin is covered by a
transparent cuticle which is slightly iridescent, and is externally
marked by annulations representing true segments. All segments
except the first and the last have four pairs of setae, two pairs being
ventral and two pairs ventro-lateral. (Fig. 45, A and B.)

From the 31st to the 37th somite, the clitellum is situated. This
aids the worms in adhering at mating and furnishes a slimy sub-

~ ~ — Prostomium

-A Mouth

Seta

A

B

Fig. 45. A, ventral view of the first four segments of Lumbricus terrestris, showing
rows of setae. B, enlarged seta. (Drawn by W. J. Moore.)

Stance that hardens into the cocoons In which the eggs are fertilized
and develop. The setae of the 26th somite are modified for repro-
duction.

The external openings Include the mouth and anus at opposite
ends. There are two nephridiopores for each somite except the first
three and the last. The two pairs o{ seminal receptacle openings are
found between the ninth and tenth and the tenth and eleventh
somites. The two oviducal openings are at the 14th somite. The
two vasa deferentia at the 15th somite are readily seen. There are
also dorsal pores on the middle line of the back between the rings,

ANNELIDA OR ANNULATA 107

from the 8th somite to the last one, which permit the passage of
fluids from the coelom to the skin. The anus is at the posterior end.

Skin. — The thin protecting cuticle is formed from the living cells
of the hypodermis beneath. The hypodermis consists of a single
layer of cells most of which are covering and supporting, but some
of which are modified into glandular (mucus) cells, and others into
nervous cells. The nerve cells are connected with sensory fibers
passing into the nerve cord, and the animal is very sensitive to
light, touch and chemically different substances. The setae which
are chitinous are worn away and replaced by reserve setae that
grow from the main seta-sac.

Muscular System. — The circular muscles lie immediately beneath
the hypodermis and, contracting, elongate the segments. The
longitudinal muscles, contracting, draw the ends of the segments
towards each other, and the direction of the setae determines whether
the movement is forwards or backwards.

Body Cavity. — The body cavity, lined by peritoneum, contains
the digestive tract, gonads, nephridia, circulatory system and nerv-
ous system beside the coelomic fluid with yellow cells, derived
from the walls of the intestine, and the phagocytic amebocytes which,
like the phagocytic white corpuscles of man, engulf poisonous
particles.

Digestive System. — The mouth or buccal cavity (1-3 somites)
leads into the pharynx (4-5 somites), with glands which moisten,
and with powerful muscles which force food on. External muscles
attached to the body wall expand the pharynx. The esophagus
(6-i4th somite) has three pairs of saccular calciferous glands, at the
loth, nth, and 12th somites, secreting calcium carbonate, which
neutralizes the free acid of the soil. The secretions from the
posterior pairs of calciferous glands open into the anterior pair, and
thence into the esophagus. (Figure 46.)

The three pairs of glands are really parts of one glandular struc-
ture, which extends from somites 10 to 14. In many specimens of
Lumbricus terrestris, the only distinct enlargements are in somite 10.
The crop (15th and i6th somites) is for storage, and mixture with
the secretions of the calciferous glands. The gizzard (17th and i8th
somites) grinds the food with sand and gravel. The stomach-
intestine (19th somite to anus) has a median dorsal infolding, the
typhlosole, that increases the surface for absorption and retards the
passage of food.

io8

ANNELIDA OR ANNULATA

Prostomium

Cerebral ganglia ('brain)

—F'/lorynx
-Pharyngeal muscles

—Seqmen t
— Septum

—A Nephr.idium (enlarged)

Serninal vesicle I

-Aortic arch (dorsal heart)

-Seminal receptacles

Seminal vesicle Z.

Calciferous gland

— E:sophQ<^us

Seminal vesicle 3

Crop

Giz:zard

-Dorso-infesfinal blood vessels
■Dorsal blood vessel

Stomach- infest in e
■Lateral diverticulum

Fig. 46. Internal anatomy of the earthworm. (Drawn by W. J. Moore and Norris

Jones.)

ANNELIDA OR ANNULATA 109

The stomach-intestine has secretory cells that furnish a digestive
jfluid corresponding essentially to the pancreatic juice of the mam-
mals, as it digests proteins, carbohydrates and fats. Albumin is
broken down in y/2 hours at 37° C. in an alkaline medium, or 28>^
hours in an acid medium. It is believed thac a peptolytic ferment
is present that accounts for slow digestion in an acid medium. An
amylotic ferment diastase changes starch into sugar (maltose). An
emulsifying ferment acts on the fats. Absorption is by osmosis and
the blood transports the nutriment. The rectU7n is the posterior
part of the intestine and has no typhlosole. It opens to the outside
through the posterior anus.

Circulatory System. — There are 5 longitudinal blood vessels;
I dorsal, i ventral, i subneural and 2 lateral neural vessels; 5 pairs
of doj-sal hearts or aortic arches (7-1 1 somites). Parietal vessels
connect the dorsal longitudinal vessel to the subneural.

In the first 12 somites the dorsal vessel is not a collecting vessel,
but behind the last pair of hearts in the nth somite, it receives
blood from the body wall and the alimentary tract. Two longi-
tudinal trunks lateral to the alimentary canal collect blood from the
anterior somites and passing posteriorly, join the dorsal vessel in
the 1 2th somite.

From the posterior part of the body the blood is carried forward
in the dorsal vessel as far as the " hearts " which force it into the
ventral vessel. Valves in the aortic arches and dorsal blood vessel
prevent the blood from returning. The ventral vessel distributes the
blood, which flows anteriorly in front of the aortic arches and
posteriorly through the remainder of the body wall, nephridia, and
alimentary system. Aerated blood returns to the dorsal trunk
through the subneural and intestinal vessels.

There are two distinct fluids which remain separated. The
coelomic fluid is found between the gut and the body wall. The
haemolymph is found in a series of closed tubes. The coelomic
fluid corresponds to the lymph of higher animals which bathes the
individual cells of the body. Haemolymph is apparently a solution
of haemoglobin. The red fluid corresponds to red blood corpuscles
of the blood of the higher animals and serves as a carrier of oxygen
to various cells and tissues of the body.

In marine worms the respiratory pigment is called chloro-
cruorine. It is ^or^^jyr/w combined with iron. Some marine forms
like Arenicola and Nereis have brilliant red blood; Aphrodite and

no

ANNELIDA OR ANNULATA

I

ANNELIDA OR ANNULATA m

Polynoe have pale yellow blood; but in Sabella It is an olive green.

The nervous system is well supplied with blood, having two
lateral neural and one subneural vessel for the nerve cord. At room
temperature (i2°-i8° C.) in Lumbricus terrestris, the dorsal vessel
pulsates about fifteen to twenty times per minute, and in Nereis
(marine sand-worm) it is about eight times per minute. Respiration
is osmotic. There are many capillaries under the cuticle.

Excretion. — Paired nephridia are found in each segment except
the first three and the last. The receiving opening, the ciliated
nephrostome, is situated one segment anterior to the one contain-
ing its own yuphridium and nephridiopore. From the nephrostome
or funnel, currents flow into the ciliated neck which passes through
the anterior wall of the segment behind, then into a narrow tube
which coils three times and then opens into a wide glandular tube^
which expels the waste at the external opening, the nephridiopore.
About half of the nephridiopores are situated on the ventral surface
in front and slightly laterad to the outer seta of the inner double
row; while the remainder of the excretory apertures are high up on
the side of the animal, dorsad to the row of dorsal seta bundles, at
irregular distances.^

Solid wastes pass out the anus and gaseous wastes through the
dorsal pores of the body wall, which are mid-dorsal, in the groove
between the segments. The first one is between segments ten and
eleven and opens into segment eleven.

Reproductive System. (Figure 46.)— The earthworm is hermaph-
roditic (monoecious) with the gonads of both sexes, but does not
fertilize its own eggs.

Female

Internal Structures External Structures

Ovaries, 13th somite. Oviducts opening at 14th somite.

Two pairs of setninal receptacles. Openings to the seminal receptacles be-

tween the 9th and loth; and the
loth and nth somites.

^ In our description of the earthworm it will be noted that certain errors of most
textbooks have been corrected, particuhirly in treating of the calciferous glands, the
position of the nephridiopores, and the collecting vessels in the anterior somites. Such
corrections were inspired by the paper by Frank Smith, Certain differences between
text book earthworms and real earthworms. Trans. 111. Acad. Sc, vol. 17, pp. 78-83.
For systematic study of the Annelida, see Verrill, A. E., 1880, New England Annelida.
Trans. Conn. Acad. Sci., vol. 4.

112

ANNELIDA OR ANNULATA

Male

Paired testes in the loth and nth so-
mites.

Three pairs of seminal vesicles at- Paired vasa deferentia opening at the
tached from the 9th to the 12th 15th somite,
somite. The last pair, bi-lobed,
extend down over the 13th and
sometimes the 14th somite.

CO

crc

! F-

\ PJl

MR

Fig. 48. Nervous system of the earthworm. Drawing showing a lateral view
of the arrangement of the larger nerve trunks in the left half of the anterior segments
of the earthworm, Lumbricus terrestris. A, nerve from lateral region of cerebral
ganglion which passes to prostomium; AN, dorsal ramus of anterior segmental nerve;
AR, ventral ramus of anterior segmental nerve; 5, nerve from near middle region of
circumpharyngeal connective which passes to segment i; 5C, buccal cavity; C, nerves
from ventral region of circumpharyngeal connective which pass to segment 2; CG,
cerebral ganglion; CPC, circumpharyngeal connective; D, branch of nerve to pro-
stomium that supplies tissues of dorsal region of buccal cavity; £, nerve that supplies
the portion of the prostomium in the dorsomedian region of segment i; F, gangliated
thickening of enteric nerve plexus; G, branch of nerve to segment i that supplies
tissues of ventral region of buccal cavity; L, septal nerve; M, mouth opening; MTV,
dorsal ramus of median segmental nerve; MR, ventral ramus of median segmental
nerve; P, prostomium; PN, dorsal ramus of posterior segmental nerve; PR, ventral
ramus of posterior segmental nerve; SG, subpharyngeal ganglion; I-VI, segments i to 6.
(Courtesy of W. N. Hess, Journal oj Experimental Zoology, vol. 40, p. 235.)

Conjugation. — Two earthworms pair so that segments 9, 10 and
II of each animal are opposite the clitellum at segments 31-37, and
the vasa deferentia of each animal are nearly opposite the 26th seg-
ment of the other where the setigerous glands are modified. Mucus
secreted by the clitellar and other glands of each worm becomes
hardened into a single " slime-tube " encasing both animals from the

ANNELIDA OR ANNULATA

"3

8th to the 37th somite. Two parallel
lines extend posteriorly from the vasa defe-
rentia to the clitellum, forming primitive
channels for the passage of seminal fluid.
Within the slime-tube the seminal fluid
flows, containing free spermatozoa and
spermatophores. The spermatophores
are deposited in the seminal receptacles of
the other worm and the slime-tube is
soon left.

Fertilization. — Later on at the appear-
ance of the capsule or cocoon, formed by
capsulogenous glands in the clitellar
region, the 4-6 mature eggs are picked up
at the egg-sacs opening at the oviducal
apertures in the 14th somite; and the
sperms that were stored in the receptacles
are secured at their openings between the
9th and loth and the loth and nth
somites. Fertilization is effected in the
cocoon at the time it slips off over the
head, and since the sperms are from an-
other animal, self-fertilization is pre-
vented. In Lumbricus comtnmiis, two
embryos are produced as a rule, in many
cases arising as twins from a single ovum.
Foot found (1898) that the total number
of eggs in 100 cocoons was 399, about 4
to a cocoon. Isolated worms deposit
cocoons for weeks.

The observations of Foot and Wilson
have been to some extent contradicted by
Grove and Cowley (1926), who found in
Eisenia foetida that cocoon formation
does not take place while the worms are
still united by the conjugation slime tube.^

2 Grove, A. J., and Cowley, L. F. 1926. On
the reproductive processes of the brandling worm,
Eisenia foetida (Sav.). Quart. Jour. Microsc. Sci.,
70 (4), 559-581-

KL A>

Fig. 49. Sperm transfer
in Lumbricus terrestris,
(Drawn by W. J. Moore.)

114

ANNELIDA OR ANNULATA

ANNELIDA OR ANNULATA 115

They noted that after conjugation, a new slime tube is formed
extending from the 7th to the 34th segment and that the eggs pass
back into the cocoon, before it leaves the region of formation at the
clitellum. Whether the sperms are squeezed out as the capsule
reaches the apertures of the seminal receptacles, or they are also
passed back to the capsule, the authors are not certain.

Nervous System. — In the worms we have well-developed cerebral
and ventral ganglia, constituting the centralization stage in the
evolution of the nervous system of invertebrates. A bilobed brain
(paired cerebral ganglia) sends off two circumpharyngeal connectives,
which unite at the subpharyngeal ganglion. A ventral nerve cord
has a ganglion in each segment, with three pairs of lateral nerves.
Two pairs come off at the ganglia and one pair between the ganglia.
Afferent nerve fibers are sensory; efferent nerves are motor. Stough
(Jour. Comp. Neurol., vol. 40, no. 3, June, 1926) has shown that the
giant fibers, seen in cross sections of the earthworm nerve-cord, are
strictly segmental structures, and consist of a large number of
closely applied parallel axones. Epidermal sense organs, chiefly lo-
cated anteriorly and posteriorly, were discovered by Fanny Lang-
don when a college Junior. (Figure 50.)

Behavior. — Earthworms react to the ordinary stimuli of light,
temperature, chemicals and electricity. They are very susceptible
to the contact stimuli produced by vibrations. It is reputed that
one way to drive earthworms from their burrows is to bore with a
sharp stake into adjacent soil.

Several articles have appeared recently regarding the so-called
" singing " of earthworms. Apparently reliable reports have been
made of the peculiar noises, possibly due to the rasping of the setae
over stones or pebbles. Clark (Animals of Land and Sea) states
that the singing girls of Java sometimes swallow earthworms in
the hope that the tinkling sound will be " imparted to their voices."

Class 3. Hirudinea — Leeches. — Hirudo medicinalis, the medic-
inal leech, has a deep olive hue, is velvety, two to three inches in
length, hermaphroditic and is found in Europe, America, Turkey
and Africa. Medicinal leeches live 15-20 years, and are adult at
5 years. They inhabit water; the female deposits 15-20 eggs in a
cocoon. These hatch in 3-4 weeks.

External Anatomy. — Their external segmentation does not cor-
respond to the internal. There are usually 5 external grooves to
each segment. The medicinal leech has 2 suckers.

ii6 ANNELIDA OR ANNUL AT A

Digestive System. — The digestive tract consists of the mouth,
with three jaws, armed with chitinous teeth, a pharynx, esophagus,
crop with eleven lateral diverticula, stomach and an anus. A
secretion called deutero-albumose (hirudin) prevents the blood from
clotting. It is formed by the glands located near the jaws. The
muscular pharynx dilates to receive the blood and passes it on
through the short esophagus to the crop which has 1 1 pairs of lateral
diverticula and which stores the blood until it is digested in the
globular stomach. No digestion takes place in the lateral " pockets."
The rectum., situated between the last two diverticula^ is separated
by a sphincter muscle from the true stomach. It ends as the dorsal
anus near the posterior sucker.

Circulatory System. — There are two main lateral vessels running
longitudinally. These are connected with each other by looped
vessels which give off many branches. There are two sinuses., one
dorsal and one ventral, with numerous primitive lymphatic vessels.
The blood is red with many white blood corpuscles. The leech has
a body temperature of about 57° F., except when it has just gorged
with mammalian blood.

Respiration is carried on by the highly vascular skin. Experi-
ments have shown that leeches will live in pure Nitrogen for from 2
to 6 days.

Excretory System. — Seventeen pairs of nephridia, from the second
to the eighteenth segment, open laterally on the ventral surface.
There are about five external annulations to each true segment.

Reproductive System. — Leeches are hermaphroditic. There are
nine pairs of diffuse testes^ which are situated on each side of the
nerve cord. The spermatozoa pass by a short canal into the long
wavy vasa deferentia. From these they travel in the epididymis
where they are bundled into spermatophores and pass out by the
penis. They leave the body in the mid-ventral line between rings
30 and 31.

Two small tubular ovaries are enclosed in vesicles., continuing into
oviducts which unite as a uterus. Glandular cells secrete into the
uterus a mucus fluid which later hardens into a cocoon.

The genital pore is situated in the mid-ventral line at rings '^^
and "^^^d (segment 11). Conjugation consists in the actual simul-
taneous insemination of each worm by the other. Spermatophores
may remain for a long time in the uterus or may travel almost
immediately in the female ducts and fertilize the eggs at the ovaries.
Cocoon formation results.

ANNELIDA OR ANNULATA 117

The Nervous System consists of a pair of dorsal ganglia situated
above the pharynx and of a double commissural nerve cord with 23
ganglia. The dorsal, supra-esophageal ganglia are connected with
the sub-esophageal pair by a rather narrow nerve ring surrounding
the esophagus. The sub-esophageal ganglia represent five pairs of
fused ganglia. From the dorsal ganglia, nerves supply the " eyes "
and tactile and gustatory organs. The last ganglion gives rise to
seven pairs of nerves. The h-ain gives rise to five pairs of optic
nerves. There are ten " eyes " and many olfacto-gustatory and
tactile sense organs.

Allied Injurious Leeches.— Hirudo sanguisaga is found in the
nasal passages of man. Haemopis vorax, the horse leech, is taken
into the mouth when young by horses and cattle. It lives in ponds,
ditches and springs and attacks man, the horse, ox, camel, and dog.
It may become attached to the mouth, pharynx or even descend to
the trachea. It is also found attached to the conjunctiva. It
produces anemia, emaciation and even death. The treatment is
strong salt solution, alum, and tar. The tar causes coughing and
expulsion of the parasites loosened by the action of the salt and
alum. If the water is stocked with fish or filtered through sand,
the parasites are destroyed.

The land leeches^ Haemadipsa Zeylanica^ are wiry, active forms,
thin as a knitting needle, i inch long and not more than }4 inch in
diameter. They attach to the legs of man and animals. They are
found in Ceylon, India, the East Indies, Japan, Australia and South
America.

Adaptation of the Leech to Its Mode of Life. — The leech is re-
markably adapted to its habitat. It can swim with great rapidity;
it is protected by a rather tough hide. It has a mouth with 3 jaws
armed with chitinous teeth, a crop with 1 1 lateral diverticula capable
of storing enough blood to last 9 months. It takes in 3 times its
own weight at one time. Not only does it have anterior and poste-
rior suckers, but it secretes a substance " hirudin " said to be
deutero-albumose, which prevents blood from clotting.

General Considerations

Distribution. — The Chaetopoda, which include earthworms and
aquatic worms found in both salt and fresh water, are distributed
widely. Very few are parasitic but a number are commensals. It

ii8 ANNELIDA OR ANNULATA

is estimated that the average field soil has 150,000 earthworms to
the acre.

Some fresh water Oligochaeta form tubes of mud held together by
a mucus secretion. Others like the marine Chaetopterus form a
yellow, parchment-like tube. Some species like Hydroides (^Serpidd)
form lime tubes on shells. Sabellaria, an aberrant form, builds
reefs on porous rocks from sandy tubes. Some species excavate
galleries in rock or corals.

Behavior. — The palolo-worm^ Eunice, found in the Pacific coral
reefs, swarms during the last quarter of the moon in October and
November. The sexual posterior part of the worm (called the
epitoke) separates from the sexless anterior portion {atoke) and floats
on the sea, giving off spermatozoa and eggs. Fishermen prepare
their nets and boats and capture these worms in great numbers,
sometimes cooking them in leaves, but at other times eating them
alive. (See p. 102.)

The Annelids are said to give little response to light and shadow
after they have become accustomed to them. But Copeland, 1930
(Jour. Comp. Psychol., vol. 10, p. 339), showed that in Nereis virens,
an apparent " conditioned response " was induced by either in-
creased or decreased illumination, which indicated to the worm the
presence of food. The earthworm draws leaves into the burrow to
line it. There is no exploration of the form of the leaf; it is seized
at any point, but only those seized at or near the apex get into the
burrow.

Hirudinea. — The leeches {Hirudinea) are parasitic forms infest-
ing invertebrates as well as vertebrates. The majority of the leeches
live in fresh water and parasitize molluscs and the vertebrates.
Certain of them are permanent ectoparasites, Branchellion attaching
to various elasmobranchs. The giant leech {Macrobdella valvidi-
viana) may reach a length of i>^ feet and is subterranean and
carnivorous. Clepsine carries its young on the ventral surface.
The skate sucker {Pontobdella muricata) has a leathery knobbed skin.
It lays its soft eggs in empty mollusc shells and guards them for
over 100 days. Lophobdella lives on the lips and jaws of the Cro-
codilia. Certain intermediate types, the Myzostomata, parasitize
the feather stars, forming galls on them.

Parasites of the Annelida. — Certain parasitic Nematodes, the
minute threadworms {Pelodera pellio), are found in the body cavity
and nephridia as well as the ventral blood vessels of the earthworm.
Various protozoa also infect the Annelida.

ANNELIDA OR ANNULATA 119

Physiology, Anatomy, and Locomotion.— The Chaetopoda are
made up of similar segments or metameres. At the sides are borne
chaetae or setae^ which are in some forms attached to muscular
processes called parapodia. The well-developed body cavity or
coelom contains the alimentary canal, the vascular system and
respiratory branchiae. The excretory organs, nephridia^ are ar-
ranged in pairs in each segment except the first three and the last.
Sexes are separate in some forms while others are hermaphroditic.
The nervous system consists of paired dorsal cerebral ganglia and a
ventral chain of ganglia with lateral nerves. The larval form is
called a trochophore . The Naidae are fresh water forms which bud
asexually. The Hirudinea have 2^o\xX five external annnlations to
each internal segment and have an extremely distensible crop for
the storage of blood. They are hermaphroditic. They swim with
great rapidity. * The aquatic forms have an undulatory movement,
while the land forms, like the ordinary earthworm, contract the
circular muscles of the body, thus elongating the segments, and then
having fixed the setae in the ground, by contraction of the longitu-
dinal muscles, direct the movement of the worm either anteriorly or
posteriorly.

Regeneration. — Earthworms will regenerate a head or a tail,
sometimes forming a tail in place of the head, and starving to death.
Grafting and fusion to form two-headed or two-tailed individuals
have been successful.

Fossil Relatives. — The Chaetopoda are found as fossils from the
Cambrian to the present, while the Hirudinea are unknown as fossils.

Ancestry and Relationship to Other Phyla. — There seems to be a
well-defined connecting link between the leeches and the allies of the
earthworm, since we find that the leech Acanthobdella has setae and a
well-developed coelom.

There seems to be a wide gap between the Platyhelminthes and
the Annulata, since both metamerism and a different nervous system
characterize the latter. Some would hold that the hair worm,
Gordius^ is a close relative of the Annulata. On account of the
common Trochophore larva, some have linked the Trochelminthes
with the Annulata. (See page 125.)

Economic Importance of the Earthworm

Positive. — {a) Charles Darwin estimated that there were 50,000
worms in one acre of ground and cited a stony hill covered with earth

I20 ANNELIDA OR ANNUL AT A

three Inches deep In twenty years. Eighteen tons of earth were
brought to the surface In one acre.

{b) Earthworms have been and probably are still used by some
savages as food.

{c) Earthworms and marine annelids are used as fish bait.

Negative. — {a) Earthworms may be of slight injury in green-
house soils.

{b) Earthworms are accidentally Intermediate hosts in the trans-
mission of the gape-worm, Syngaynus trachealis. It is not necessary
to the life of the parasite that it be taken in by the earthworm.

{c) Certain medical men have from time to time suggested that
the earthworm may be important in transmitting cancer through
the deposition of the organism in feces transferred to vegetables by
the earthworm. This is purely conjectural.

Economic Importance of the Leech

Positive. — (a) In cases of hemophilia (persistent bleeding) and
after contusions, physicians and veterinarians still use leeches to
extract blood. Some drug stores keep a supply of leeches on hand
In the spring to serve the needs of those foreigners who get black
eyes at weddings and other celebrations. The doctor of the Middle
Ages was called the " leech."

(b) Leeches are said to have been used for food by some savages.

Negative. — Leeches parasitize some aquatic and amphibious
forms.

CHAPTER VIII

Phylum Trochelminthes

The Rotifera, sometimes called "wheel animalcules," belong to
a group, the exact relationship of which is unknown. They have
sometimes been classed with the worms. The majority of them are
free swimming and move by means of a trochal disc (Fig. 51). In
other forms a telescopic tail aids the animal in performing looping
movements similar to those of a leech. Przibram states that, in the
Rotifer, growth is not followed by the formation of new cells, but
the size of single cells increases.

Rotifera are for the most part found in fresh water, although
a few are marine. When the water dries up, the thick-shelled
winter eggs of certain rotifers may be dispersed by the wind or by
animals. They are able to survive freezing temperature.

Eichhorn (1781) describing Floscularia says: "Now I come to a
very wonderful animal, which has often rejoiced me in my observa-
tions: I call it the Catcher: extraordinarily artistic in its structure,
wonderful in its actions, rapid in capturing its prey." (From H. S.
Jennings, in Ward and Whipple's "Fresh Water Biology," published
by John Wiley and Sons, Inc., 191 8.)

Rotifera have an elongated body^ with a tail-like appendage, the
foot^ which commonly ends in two pointed toes. Pedal cement
glands aid in attachment. The digestive syste^n is well developed
with an anteriorly situated inouth which is between the ciliated
trochal discs and leads into a muscular pharynx. At the lower end
of the pharynx is the gizzard or mastax which has chitinous teeth.
(See Gosse, "Structure, Functions and Homologies of the Manduca-
tory Organs in the Class Rotifera." Phil. Trans., 1856.)

The excretory system is relatively simple, with paired convoluted
tubes, the kidneys, which open directly or indirectly into the cloaca.
The nervous system consists of the dorsally situated brain, with
nerves given off to the corona, the muscles, integument, and sense
organs. Two large nerves are given off laterally from the brain
and each divides into a ventral and a lateral longitudinal trunk.
The sense organs consist of the tactile and olfacto-gustatory an-

121

122

PHYLUM TROCHELMINTHES

tennae, and the single or paired eyes, which are not present in all
forms.

The male reproductive system consists of a large testis, two or

.Bristle of
C orona

Ciliary Rim.

Dorsal

Antenna

Ciliated Area.\

Retractors of
the Corona

fsophagus

Ciliated Area

CiJ

A'u clei of the
yolk Gland
Ciliated

Area
Lateral
Antenna'

Intestine

Sensory
,:~; Bristle

Brain

\\..A/astax
'^^V^^'\\ Masticatory
j;. \/V' Apparatus

%\ j--'\ Gastric Gland

cJJ — '^ \ Retractors of

■r^ \ •• the Corona

^ , • -r \ — Stomach

^^^■^^r?. >>^- .. . \ . Foot Retractor

£y.cretory Tube
Lateral

/JC I Antenna

fji. '-•■Contractile

Bladder
__ _ Foot Retractor-

Y!^.— - -ji^- -Cloaca

■//'-■■■ Cloaca

Fig. 51. Diagram of a Rotifer. Brachionus rubens Gosse. (After Wesenberg-Lund.)

four so-called prostate glands, a well-developed vas deferens, a large
seminal vesicle, and a protrusible penis.

Males of most Rotifera are relatively short-lived and quite
degenerate. In some species no traces of the digestive glands and
mastax, prominent in the female, are found. The rudimentary

PHYLUM TROCHELMINTHES 123

anterior portion of the digestive tube serves as a suspensory ligament
for the testis. (Miller, 1931.)

Cloacal fertilization is not apparently the rule, since in many
cases the male apparently bores into the body wall and the sperms
evidently pass through the wall of the oviduct in order to fertilize
the eggs. (Gamble, Camb. Nat. Hist.) Males hatch from the
small eggs of the mictic females.

In the female the large yolk-gland or vitellarium^ which usually
consists of eight cells, is found on the ventral side of the stomach.
The true ovary consists of many small, rounded cells, the posterior
one enlarged and receiving a shell just before it is extruded.

Rotifers are especially interesting to us on account of their use
in experiments on the alternation of parthenogenetic and bi-sexual
development. Whitney, Shull, Luntz and others have studied the
influence of food and other factors on the control of the reproductive
cycle in rotifers (Figure 52).'

Recalling Loeb's discovery that in the Echinodermata the ex-
traction of water from the eggs by hypertonic solutions would start
developmental processes, Jacobs (1909) suggested that in certain
rotifers desiccation is able to bring on reproduction. Hickernell
(1917), studying Philodina roseola^ found that the dried rotifer
had an integument thinner than that of the undried specimen, and
that an increase in the number of ovarian nuclei occurred at the
very beginning of the drying process, while the animal was recover-
ing. But Whitney (1930), reporting on the hatchability of eggs of
Hydatina senta stored for twenty-two years, found that the fecundity
of individuals hatching from fertilized eggs after this long period of
desiccation was lowered, the mothers from old eggs producing an
average of thirty less daughters than the controls.

It was shown by dal Bianco (Jour. Exp. Zool., vol. 39, no. i,
1924) that HCl and FeSOa brought about a notable acceleration of
the life cycle of Proales felisy even with concentrations that induced
a marked mortality.

Jennings and Lynch (1928) studied the origin of individual
differences during parthenogenetic reproduction under constant
environmental conditions. Their studies seem to indicate that
differences in the length of life of rotifers result from the interaction
of rhythmic processes of digestion and reproduction. They found,

1 Consult Shull, A. F., Determination of types of individuals in aphids, rotifers
and cladocera. Biol. Rev., 1929, vol. 4, no. 3, pp. 218-248.

124

PHYLUM TROCHELMINTHES

in addition to difference in length of life, differences \n fecundity of
individuals, correlated with differences in the size of the partheno-
genetic eggs from which they were derived. Lynch and Smith
(1931) showed that in rotifers it is possible to produce and maintain
depression for a long period of time and that the depression becomes

Fig. 52. Brachionus militaris. Dorsal views. A, female with attached par-
thenogenetic female eggs; 5, female with attached parthenogenetic male eggs; C,
female with attached fertilized eggs; D, male. (After Whitney, Jour. Exp. ZooL,
vol. 24, Oct. 1917.)

PHYLUM TROCHELMINTHES

125

greater in later generations. With restoration to normal conditions,
however, it disappears within one or two generations.

Miller (1931) has described the life history of the rotifer Lecane^
which is admirably suited to a study of the alternation of partheno-
genetic and bisexual generations. The mictic female rotifer, capa-
ble of sexual reproduction, produces small eggs which if unfer-
tilized develop into
males. The fertilized
eggs are larger and pro-
duce females. The com-
mon type of rotifer
female, the amictic^ can-
not reproduce by am-
phimixis (see page 518).
Eggs of the amictic fe-
males develop by diploid
parthenogenesis (see
pages 503 and 505) and
produce diploid females,
which may be either am-
ictic or mictic. In Mil-
ler's studies, the length
of life of females of
Lecane inermis depends
to some extent on the Fig. 53. Female producing and male produc-

Se verity of the process ing eggs of Lecane inermis. Left, the fertilized
of egg production. The (female producing) egg of the mictic female. Right,,
/■ , J the (female producing) egg of the amictic female.

\ Bottom, the (male producing) egg of the mictic

about two-tnirds as female, before the initiation of cleavage. (Courtesy-
many eggs as the amictic of H. M. Miller and the Biol. Bull.)
and have a longer life.

Parasitisyn in Rotifers. — Some rotifers (Drilophaga) parasitize
worms and some (Seison) parasitize Crustacea. Others are internal
parasites found infesting the coelom or the intestine of worms.

The trochosphere^ or trochophore larvae of the Rotifera, resemble
the free swimming larvae of certain annelids. (See page 119.)

References on Trochelminthes

HiCKERNELL, L. M. 1917. A Study of desiccation in the rotifer Phi-
lodina roseola, with special reference to cytological changes accom-
panying desiccation. Biol. Bull., vol. 32, no. 5, pp. 343-407.

126 PHYLUM TROCHELMINTHES

Jacobs, M. H. 1909. The effects of desiccation on the rotifer Philo-
dina roseola. Jour. Exp. Zool., vol. 6, no. 2, pp. 207-263.

LuNTz, A. 1926. Untersuchungen iiber den Generationswechsel der
Rotatorien. I. Die Bedingungen des Generationswechsels. Biol,
Zentralbl., 46: 233.

LuNTZ, A. 1929. Untersuchungen iiber den Generationswechsel der
Radertiere. II. Der zyklische Generationswechsel von Brachionus
bakeri. Biol. Zentralbl., 49: 193.

Lynch, R. S., and Smith, H. B. 1931. A study of the effects of modifi-
cations of the culture medium upon length of life and fecundity in a
rotifer, Proales sordida, with special relation to their heritability.
Biol. Bull., vol. 60, no. I, pp. 30-63.

Miller, H. M. 1931. Alternation of generations in the rotifer Lecane
inermis Bryce. I. Life histories of the sexual and non-sexual
generations. Biol. Bull., vol. 60, no. 3, pp. 345-381.

Shull, a. F. 191 1. Jour. Exp. Zool., vol. 10, 191 1, and later papers.

Wesenburg-Lund. 1929. Handbuch der Zoologie, Bd. 2, L. 50, W.
de Gruyter & Co., Berlin u. Leipzig.

Whitney, D. D. 1907. Determination of sex in Hydatina senta.
Jour. Exp. Zool., vol. 5, pp. 1-26.

Whitney, D. D. 1916. The control of sex by food in five species of
rotifers. Jour. Exp. Zool., vol. 20, pp. 263-296.

Whitney, D. D. 1930. Hatching twenty year old eggs and the reduc-
tion of vigor in the rotifer Hydatina senta. Anat. Rec, vol. 47,
P- 354-

CHAPTER IX

MOLLUSCOIDEA

Certain forms known as Brachiopoda and Bryozoa ("Polyzoa"
of England), on account of their resemblance to Mollusca, have been
grouped under the Phylum Molluscoidea.

In 1830, J. V. Thompson separated the Bryozoa from the polyps,
and called them Polyzoa from their habit of gemmation, and their
digestive tube. One year later, Ehrenberg changed the term to
Bryozoa. In 1841, Milne-Edwards created the Phylum Mollus-
coidea, including it in Bryozoa and Tunicata. Subsequently the
Tunicata were removed, and in 1 853, Huxley added the Brachiopoda.

Class I. — The Brachiopoda (Gr. brachion^ the arm; and pous^ a
foot) are strictly marine, being found in all oceans, and occupy a
calcareous bivalved shell, the valves of which are dorsal and ventral
instead of lateral as in the Lamellibranchs. Once rulers of the sea,
it is supposed that the Brachiopoda or " lamp-shells " were notably
reduced in numbers by
boring molluscs. They
are geologically very
ancient, Lingula, the
oldest known genus of
animals, having changed
but slightly since the
earliest Silurian times.

Class 2. — The B^-yo-
zoa (Gr. bruon^ moss;
and 200W, animal) are for
the most part colonial,
somewhat resembling
hydroids. They are
sometimes stained and

sold as " air-plants " but Hydrozoa (page 69) are the common
" air plants." They are found in both salt and fresh water. The
false coral {Discosoma nidita) is a marine colonial form that encrusts
shells and stones until it somewhat resembles coral. It is found
in water at least thirty feet deep. (Mayer.)

127

° A

Fig. 54. Statoblast of CristattUa. (After Allman.
Courtesy of Macmillan and Co., Ltd.)

128 MOLLUSCOIDEA

Occasionally one finds the fresh-water Bryozoa Fredericella and
Plumatella encrusting masses of vegetation and plant life in " pipe
moss." They die speedily when water is filtered, or when ground
water is used. The compound bryozoan Pectinatella alarms some
pond owners as it increases rapidly, forming a jelly-like mass, some-
times six feet in diameter. (Figure 54.) Bryozoa are eaten by
sharks, the cunner (a teleost), and an aquatic mammal, the " black-
fish."

References on Bryozoa

Allman, G.J. 1856. Monograph of freshwater Polyzoa. Proc. Roy.
Soc.

BossLER, R. S. The Bryozoa or Moss Animals. Smiths. Inst. Rep. no.
2633.

O'Donoghue, C. H. and E. 1926. Second List of Bryozoa from Van-
couver Island Region. Cont. to Can. Biol., N.S., iii, pp. 47-132.

OsBURN, R. C. 1912. The Bryozoa of the Woods Hole Region. Bull,
of the Bur. of Fish., vol. 30, doc. no. 760, pp. 205-266.

Class 3, Phoronidea. — The Phoronidea resemble the Bryozoa
in some respects and are usually placed under the MoUuscoidea.
Phoronidea are sessile marine worms bearing tentacles and living in
chitinous sand-covered tubes. The body of Phoronis is cylindrical,
and unsegmented, containing a large body cavity, with mesenteries
dividing it into three chambers. There are two circulatory fluids,
a colorless one in the body cavity, and the red hemoglobin-zonx.2\mvi^
blood of the closed circulatory system. Phoronis is hermaphroditic,
the larvae in their metamorphosis passing through a stage called the
Actinotrocha. A horseshoe-shaped nerve ring is located at the base
of the tentacles, with two ciliated sensory grooves anterior to it.

CHAPTER X

ECHINODERMATA

EcHiNODERMATA (Gr. ecMnos, a sea hedgehog; derma, skin) Is a
group of marine animals representing the most highly specialized
of the radially symmetrical forms, and is further distinguished by the
presence of a calcareous skeleton, which is sometimes in the form of
scattered particles or spines, in other cases developed into plates.
A well-developed coelom points to a high degree of organization.

Classification

Class 1. Asteroidea (Gr. aster, a star; eidos, resemblance) pentamer-
ous; arms not sharply marked off from disc; ambulacral
groove present. (Starfishes.)

Class 2. Ophiuroidea (Gr. ophis, a snake; oura, a tail; etdos, form)
pentamerous; arms sharply marked off from disc; no am-
bulacral groove. (Brittlestars.)

Class 3. Echinoidea (Gr. echinos, hedge-hog; eidos, form) pen-
tamerous; without arms or free rays; test of calcareous plates
having movable spines. (Sea urchin, sand dollar, heart
urchin.)

Class 4. Holothuroidea (Gr. helos, whole; thurois, rushing) long
ovoid; muscular body wall; tentacles around mouth. (Sea
cucumbers.)

Class 5. Crinoidea (Gr. krinon, a lily; eidos, form). Arms gen-
erally branched and with pinnules; aboral pole usually with
cirri or sometimes with stalk for temporary or permanent
attachment. (Feather star, sea lily.)

Class 6. Cystoidea (Gr. cystis, bladder; eidos, form) — extinct.
Confined to Paleozoic; extend from Cambrian to Permian
inclusive with maximum development in Ordovician and
Silurian.

Calyx usually stemmed; mouth nearly or quite central
upon the upper (ventral) surface. From the mouth radiates
two to five or more simple or branching ambulacra along
which food particles pass to the mouth probably driven

129

I30 ECHINODERMATA

by numerous cilia. These food grooves may be on outer
surface and are rarely extended into free branches, the arms.
Anal opening excentric, often closed by a valvular pyramid.
Cystoids are the oldest and least specialized group of
Pelmatozoa (which include cystoids, blastoids and crinoids).
Class 7. Blastoidea (Gr. blastos^ a bud; eidos^ form) — extinct.
Confined to the Paleozoic, ranging from the Ordovician to the
Permian. Calyx ovate, short stemmed or stemless; distinct
arms absent, existing only as pinnules. Ten spiracles around
mouth, connected internally with hydrospires. Some have
a distinct anal opening; in others this is fused with one of the
spiracles. From the mouth radiate five ambulacra! areas.

Characteristics

I. Radially symmetrical; larvae bilaterally symmetrical.

1. Calcareous skeleton, sometimes in plates which fit into each other

to form a shell; sometimes in the form of scattered particles

or spicules.

3. In many the surface is beset with spines or tubercles.

4. Never move rapidly in an adult condition; some are fixed by a

stalk.

5. Never bud to form a colony.

6. All marine.

7. Water vascular system (coelomic in origin) used for locomotion

and to open bivalve molluscs.

8. Body cavity well developed in the disc and usually in the arms,

and separate from the digestive cavity.

Natural History

Class 1. Asteroidea. Type of Group — Asterias forbesii.
Starfish. (Figure 55.) — The starfishes have a star-shaped body,
with a central disc and five radiating arms, each of which contains a
prolongation of the body cavity and the organs belonging to the
digestive, reproductive and water-vascular systems. On the dorsal
side one finds the anus and the madreporic plate, while on the ventral
surface the tube feet protrude from five narrow grooves.

External Anatomy. — The upper (aboral) surface is distinguished
by the presence of many spines of various sizes; pedicellariae at the
bases of the spines; a madreporite which is the entrance to a water-
vascular system; and anus.

ECHINODERMATA

131

The lower surface, usually attached, has a mouth, five grooves
(ambulacral) with two to four rows oi tube feet extending from them.

The skeleton is made up of calcareous plates {ossicles) united by
connective tissue. Ossicles are regularly arranged around the
mouth and in the ambulacral grooves and often along the sides of the

Fig. 55. Common starfish. (From Mayer. Courtesy of N. Y, Zool. Soc.)

arms. The ambulacral ossicles are movably articulated so that they
can open or close the groove. At the end of the ray the ambulacral
ossicles end in a median terminal ossicle. There are thus two or
three rows of movable ambulacral spines. The spines are shoj-t and
blunt, covered with ectoderfu and arranged in irregular rows parallel
with the long axes of the rays. They are supported on irregularly
shaped ossicles.

132

ECHINODERMATA

Fig. 56. Ambulacral plates and pores.
(W. J. Moore.)

In the spaces between the ossicles are a number of minute pores ,
the dermal pores^ bearing retractive dermal branchiae or papulae which
are soft filiform processes and concerned in respiration. The body
wall is covered with a layer of ciliated epithelium, the epidermis,
continued over tubercles, spines, pedicellariae, dermal branchiae and

tube feet. (Figure 56.)

Musculature. — The arms
are movable, being supplied
with muscle fibers in the body
wall.

Digestive System. — The
mouth opens through a short
passage, the esophagus, into a
wide sac, the cardiac divi-
sion of the stomach. This is
five-lobed (pentagonal), with
each lobe opposite one of the five arms. The cardiac stomach is
everted through the mouth. Its retraction is effected by special
retractor muscles attached at the sides of the ambulacral ridges.

The cardiac stomach communicates with the smaller pentagonal
pyloric stomach, which in turn opens into a short conical intestine,
leading upward to open at the anal aperture on the aboral side of the
disc of the starfish. The pyloric stomach is extended at its five
corners to form a pair of pyloric ceca in each ray. Each pair of
pyloric ceca begins as a cylindrical duct, leading into the pyloric
chamber. This bifurcates to form two smaller ducts, which give off
laterally short branches, each connected with many small glandular
pouches. The glandular pouches secrete juices containing enzymes
and pass them through the series of ducts into the pyloric stomach.
The pyloric (hepatic) ceca are productive of a digestive juice
similar to the pancreatic juice of vertebrates, which converts starch
into sugar, proteins to peptones and emulsifies fats. Intestinal
ceca, attached to the intestine, secrete a brownish material, probably
excretory.

Water Vascular System. — This remarkable system (Figure 57) is
used in the starfish for locomotion and in securing its food. It is a
specialized portion of the coelom. From the madreporic plate, the
stone canal leads downwards to the ring canal or circular canal. (The
circular canal bears four pairs of Tiedemann's vesicles and one extra
opposite the stone canal); from this canal five radial canals pass out.

ECHINODERMATA

133

one into each arm; the radial canals give off side branches from which
come connecting canals to the tube feet and ampullae. The tube feet
furnish a means of adhering to smooth surfaces when a vacuum has
been created by the withdrawing of water into the ampullae.
Squeezing the ampullae causes the water to distend the tube feet
and they protrude through the pores.

Madreporite
Stone Canol

Tiedemonn Body
Circular Cona/ —■

/Radial Canol -

Ampulla

Connecting Cono/

Tube Foot

Fig. 57. Water-vascular system of the starfish. (Drawn by W. J. Moore.)

Respiration. — The dermal branchiae are thin-walled finger-like
sacs that protrude through little holes in the wall of the animal,
called dermal pores. Dermal branchiae, as the name indicates, are
for respiration.

Circulation. — The presence of a well-developed digestive system
and of a quantity of coelomic fluid renders the blood vascular system
of less importance. The coelomic fluid contains a number of
ameboid corpuscles that collect wastes and pass them to the exterior
by passing along the walls of the dermal branchiae. It is also
worthy of note that the minute Tiedemann's vesicles on the circular

134 ECHINODERMATA

canal of the water vascular system produce ameboid lymphocytes
that may be quite important.

The perihaemal system, compared by some to a true blood vas-
cular system, consists of the axial organ (genital stolon), adjoining
the stone canal; the oral ring vessel, surrounding the mouth and
divided by a septum; the perihaemal vessel, divided by a septum,
and the five radial blood vessels that are found in the rays. The
perihaemal septum is found to contain gelatinous connective tissue
and many white blood corpuscles (leucocytes), and is perforated by
many irregular channels.

Excretion. — Besides osmotic excretion, the starfish has the ability
to excrete shells and other wastes from the mouth. Indigestible
foods also pass through the intestine and out at the anal aperture.
The ameboid corpuscles of the coelomic fluid aid in excretion.

Reproduction. — Starfishes are not hermaphroditic, although some
other Echinoderms are. Each animal produces from paired gonads
either eggs or sperms. The gonads are situated in the rays with
their ducts opening on the aboral surface through minute pores on a
pair of sieve-like plates situated close to the bases of the arms,
between the rays. During the spawning season the gonads may
have so many eggs that the starfish will have enormously distended
rays, and the hepatic ceca may be crowded until they are much
reduced in size. The eggs are fertilized outside the body, although
many perish without fertilization having been effected. In one
year a starfish may have arms two and one-half inches long and be
ready to spawn.

Artificial Parthenogenesis. — Norman, Greene, Matthews, Mor-
gan and Loeb, developed a method of inducing the development of
unfertilized eggs of echinoderms. Loeb continued the work for
many years and proved that in the absence of sperms, variation in
the temperature, the addition of sodium chloride, potassium
bromide and cane sugar solutions would cause normal larvae to
develop. For years students in the embryology course at the
Marine Biological Laboratory at Woods Hole, Massachusetts, have
repeated the experiments with complete success. Subsequent to
his echinoderm work, Loeb succeeded in producing fatherless frogs.
(See page 299.) In nature, echinoderms and some annelids as well
as plant lice and rotifers normally develop parthenogenetically, that
is, without the stimulus of sperm.

Nervous System. — The nervous system consists of the nerve ring.

ECHINODERMATA 135

found in the disk, and a radial nerve with branches, found in each
ray, in the integument covering the ambulacral groove. There are
also two radial nerve bands forming the deep nervous system, and a
third set of nerve elements, the aboral or coelomic nervous system,
extending along the roof of the arm superficial to the muscles.

Sense Organs. — The tube feet and the spines have tactile nerves
associated with them and the whole animal is undoubtedly sensitive
to temperature. At the end of a ray one finds a red spot, the " eye,'^
which is sensitive to light. Above it is a process, called the tentacle,
similar in appearance to the tube feet but without a terminal sucker.
The tentacles are olfacto-gustatory organs and more important to the
starfish than the so-called " eyes."

Behavior. — The starfish senses food and is able to open oysters
readily. MacBride states that small bivalves are taken completely
into the stomach of the starfish, the empty shell being later expelled
through the mouth.

MacBride quotes Schiemenz as follows: " A bivalve able to
resist a sudden pull of 4,000 grams will yield to a pull of 900 grams
long continued. A starfish can exert a pull of 1,350 grams- but must
raise itself into a hump in order to open an oyster." Turned upon
its back the starfish ordinarily uses certain rays to right itself.

Economic Importance. Positive. — Starfish are used to a limited
extent as fertilizer, and have been extremely valuable in the study
of embryology, particularly in connection with the problems of
fertilization. Negative. The starfish injures oysters and other
molluscs by direct action, opening and devouring them or ingesting
small ones and expelling the shells from the mouth. One little
starfish ate over 50 young clams in 6 days (Mead).

Class 2. Ophiuroidea. — The brittle stars or " serpent stars " re-
semble the true starfishes considerably, having a star-shaped body
with a central disc and five radiating arms. They have distinct
oral and aboral surfaces with the mouth in the center of the disc.

The arms are slender and tapering, covered with plate-like
ossicles and lateral spines. The muscular system of the arms is
highly developed so that rapid movement is effected by their lateral
sweep. Pyloric ceca and anus are lacking, the madreporic plate is on
the ventral surface instead of the dorsal, the tube feet are tactile
instead of locomotor and the ampullae have disappeared. Serpent
stars secure their food by means of specialized, oral tube feet, two

136

ECHINODERMATA

pairs to each arm. " Brittle stars " have highly developed autotomy
and the ability to regenerate new arms. (Figure 58, ^^ and 5.)

Fig. 58. A, serpent star. 5, sand dollar. (From Verrlll.)

Class 3. Echinoidea. — The sea urchins are not star-shaped, but
globular. The shell or test is made up of firmly united ossicles
ranged in rows which run from the oral to the aboral poles. Many
of the plates bear movable spines which aid in locomotion. Five

ambulacral plates have openings
into the egg sacs. There are five
bands of distensible locomotor
tube feet beginning near the oral
opening and running towards the
aboral pole. The distinctive
feature of the sea urchin known
as Aristotle^ s lantern consists of
five jaw-like structures, each
bearing a rather large sharp
white tooth. The intestine is
quite long and has no radiating
ceca. Sea urchins are able to
chisel out solid rock by turning
round and round. The spines
of large sea urchins have been
used as slate pencils by missionaries in the Pacific Islands.

The sand dollars or " cake urchins'" are flattened and disc-like,
living near the surface of the sand. The heart urchins or " sea bears "
bury themselves in the muddy sands for several inches. Under the

Fig. 59. Purple sea urchin. (From
Mayer, Seashore Life. Courtesy of N.
Y. Zool. Soc.)

ECHINODERMATA 137

name of " sea eggs," the urchins are sold during the spawning season
in the Orient.

Class 4. Holothuroidea. — The sea cucumbers include rather
small forms which are found in the colder waters, and large tropical
species. Some of the Holothurians are called sea slugs because of
their resemblance to a mollusc. Other forms are called cotton
spinners because they excrete cottony filaments when irritated.

Fig. 60. Sea cucumber. (Courtesy of Amer. Mus. of Nat. Hist.)

The sea cucumber has a muscular body wall with a few calcareous
spicules, a circlet of tentacles around the mouth and five zones of
tube feet running from mouth to anus. {Synapta lacks tube feet.)

The alimentary canal consists of a long coiled intestine with a
muscular enlargement, the cloaca, at the posterior end. Respiration
is carried on by the cloaca, tentacles, respiratory trees and body wall.

General Considerations

In the adult condition, Echinoderms usually creep along the
sea bottom, for they are all marine. The larvae, however, are
surface swimmers, or " pelagic." They are gregarious in habits
and found in all depths.

Anatomy and Location. — The Echinodermata are radially sym-
metrical, with an exo-skeleton of calcareous plates or ossicles bearing
in most cases spines. They have a well-developed alimentary,
nervous and water vascular system, with a poorly developed vascular
system. Reproduction is sexual.

Locomotion in the starfishes is a slow, creeping movement by

138

ECHINODERMATA

^ I

means of the tube feet. The Holothuroidea utilize their tentacles
in movement. The brittle stars move by lateral contractions of
their arms. The Echinoidea move by means of spines and a few

tube feet.

Physiology. — In the sea urchin we have the first instance of
masticatory structures in the invertebrates. The five teeth of the
" Aristotle's lantern " are extremely powerful. The digestive
system is extremely efficient as seen in the starfish. (See p. 132.)
Respiration is carried on by the dermal branchiae. Circulation is
not well developed and perhaps is not needed with the complicated
water vascular system. The body fluid, hydrolymph or blood, is
similar to the fluid in the water vascular system, but is richer in
albumen. In the sea cucumber, Thyone, the hemoglobin occurs
in small, very numerous corpuscles. Excretion is carried on by the
mouth, the dermal branchiae and the intestine.

Reproduction. — Well-developed gonads are present and sexes
are separate in many of the Echinoderms. Parthenogenesis occurs
frequently. (See p. 134.)

Behavior. — The Echinoderms have well-developed reactions to
stimuli of touch, light and temperature They also have primitive
olfacto-gustatory sense.

Embryonic Development of the Echinodermata. — The eggs of
Echinoderms divide into 2, 4, 8, 16, 32, 64 cells, each finally be-
coming a blastula^ then a gastrula^ and finally a larval stage. The
larvae are bilaterally symmetrical, with an aUmentary canal from
which later bud two coelomic sacs. These form the body cavity and
the water-vascular system. The larvae of the different classes
vary somewhat in structure. Bilateral symmetry is lost in the
adults except as it is retained slightly in the Holothuroidea.

Importance of Echinodermata in Biological Research. — During the
past thirty years, we have seen increased utilization of invertebrate
forms in research at our marine laboratories. The starfish and the
sea urchin have been the types used in numerous chemical and
physiological studies, far-reaching in their significance. Mathews,
Child, J. Loeb, Tenn/nt, F. Lillie, R. Lillie, Just, Heilbrunn, Glaser,
Sampson, Woodward, and their associates, have been especially
active in these studies.^

1 See the Wistar Institute Bibliographic Service, and the Journal, Biological
Abstracts, for references. Also refer to paper by D. H. Tenn^nt, 1929, Studies in
experimental embryology based on sea urchin eggs. Sc. Mon., vol. 29, no. 2 (167),
pp. 1 17-124.

ECHINODERMATA 139

Echlnoderm eggs are especially convenient for studies on the
physiological changes occurring during development. Warburg
found for example that fertilized starfish eggs utilized oxygen eight
times as fast as the unfertilized ones. Important studies on the
changes in permeability of eggs immediately following fertilization
have been made by R. Lillie and more recently by Dorothy Stewart.

F. Lillie and E. Just believe that the secretions of Arbacia (a sea
urchin) eggs contain an amboceptor with an ovo-phile side chain
which combines with the egg and a spermo-phile side chain which
combines with the sperm. The egg secretion enables the sperm
to fertilize the egg. (Consult Lillie, F. R. 191 9. Problems of
Fertilization. Univ. of Chicago Press.)

But A. E. Woodward finds that it is possible to precipitate from
the egg secretion by one method a substance which activates the
sperm, and by another method a second substance which brings
about parthenogenetic development of the sea urchin egg. Dr.
Woodward has also utilized iodin (see page 439) as an agent in
parthenogenesis. (Consult Woodward, A. E., and Hague, F. S.
1917. Iodine as a parthenogenetic agent. Biol. Bull., vol. 38,
PP- 355-360.)

The writer of this text believes that iodin saturates the un-
saturated fats of the egg, and that increased oxidation causes cell
division to occur.^ (See papers by Chidester and associates.)

Parental Care. — In the Asteroidea, the young are sheltered in
the arms of the adults. One form, Pteraster, has a tent-like brood
pouch.

Regeneration. — The Echinoderms have a well-developed charac-
teristic known as self-mutilation or autotomy. This is most marked
in many Ophiuroids, some Asteroids and some Holothurians, but
does not occur at all among the Echinoids. Brittle-stars and star-
fishes, when removed from water or molested, will sometimes break
off portions of their arms, piece by piece, to the very base. The
central disc is entirely capable of regenerating new arms. The sea
cucumbers frequently eviscerate themselves, escape from their

2 Iodin has a well-known corrosive action on fats, and it is undoubtedly effective
m dissolving the fatty pellicle around tubercle bacilli as well as other pathogenic
organisms treated successfully by cod liver oil. The West Virginia University group
are treating certain diseases with super-iodized cod Hver oil. Possibly iodin is re-
sponsible for the protective and curative actions ascribed to other chemicals admin-
istered in combination with it.

I40 ECHINODERMATA

enemies and later regenerate the entire alimentary canal. Mayer
(Seashore Life) reports that the brittle sea cucumber Synapta lives
in a ringed sand tube agglutinated with slime. Bands of sand are
formed and forced down to finally form the tube. Leptosynapta
breaks itself up into short lengths and then regenerates.

Fossil Relatives. — Cystoidea are extinct. Their fossils are con-
fined to the Paleozoic, extending from the Cambrian to the Permian
with maximum development in the Ordovician and Silurian. The
Blastoidea, also extinct, are confined to the Paleozoic, ranging from
the Ordovician to the Permian. The Crinoidea range from the
Ordovician to the present time, being most abundant as fossils in
the Upper Paleozoic. The Asteroidea, Ophiuroidea, Holothuroidea
and Echinoidea have descended to the present, from the upper
Paleozoic.

Ancestry and Relationships to Other Phyla. — It has been found
so difficult to connect the Echinodermata with other Phyla that they
have been for some time considered relatively isolated. Early
attempts to link them with the Coelenterata on account of their
radial symmetry have encountered the objection that the Echino-
dermata have an extensive coelom or body cavity. They have
highly developed alimentary and nervous systems not present in
the lower Phyla. It is now believed that the embryonic history
of the Echinoderms indicates that they developed from a group with
bilateral symmetry. The oldest classes of Echinodermata are those
with the radial symmetry least developed. Thus the stalked Cri-
noids are considered the ancestors of the free living forms. Crinoidea,
Cystoidea and Blastoidea represent the primitive type, while radially
symmetrical Asteroidea, Ophiuroidea and Echinoidea are probably
descended from the primitive Holothuroidea. The Echinodermata
are an isolated group, with no living or fossil links. The echinoderm
larva, somewhat comparable to that of Balanoglossus, called Tor-
naria (see page 217), has led evolutionists to place the Phylum in the
series of Invertebrates that are supposed to be progenitors of
Vertebrates.

ECHINODERMATA

141

Economic Importance of the Echinodermata

Class
Asteroidea,

Echinoidea.
Holothuroldea.

Negative
Attack oysters and clams, open-
ing shells and devouring the
soft parts.

Positive

Fertilizer.

Eggs used as food.

Experimental embryology.

Roe of sea urchins are eaten.

Spines are used as slate pencils.

Several species of sea cucum-
bers are utilized as food by
the Chinese under the names
of trepang or beche-de-mer.

References on Echinodermata

Cole, L. J. 1913. Direction of locomotion in the starfish, Asterias
forbesii. J. Exp. Zoo!., vol. 14.

Gemmill, J. F. 1 91 2. The locomotor functions of the lantern in Echi-
nus, with observations on other allied activities. Proc. Roy. Soc.
Lond., Ser. B, vol. 85.

Kindred, J. E. 1924. The cellular elements in the perivisceral fluid
of echinoderms. Biol. Bull., vol. 46, pp. 228-251.

Paine, V. L. 1926. Adhesion of the tube feet in starfish. J. Exp.
ZooL, vol. 46, pp. 361-366.

CHAPTER XI

MOLLUSCA

The Mollusca (Lat. mollis^ soft) are bilaterally symmetrical.
This symmetry is modified by dextral, sinistral, or frontal torsion in
the adult Gastropoda. While for the most part the Mollusca differ
from the Annelida and the Arthropoda in being unsegmented, the
Cephalopoda have certain segmented ducts, and the Amphineura
are segmented. The majority have an exoskeleton of calcium car-
bonate, the shell. In general we find that Mollusca are sluggish.
Many Mollusca are of economic importance (see page i6i).

Classification

Class 1. Pelecypoda (hatchet foot) or Lamellibranchiata (leafy
gills). Clams, oysters, mussels, scallops. Usually bilater-
ally symmetrical, with two-valved shells, and a two-lobed
mantle. Abundant in Cretaceous of America. Marine and
fresh water.

Class 2. Amphineura (on both sides — a nerve). Chitons, with
bilateral symmetry, shell of eight transverse calcareous
plates and many pairs of gill filaments. Ordovician to
present. Marine.

Class 3. Gastropoda (belly foot). Snails, slugs, whelks, with a
spirally coiled shell. Some dextral and others sinistral.
Cambrian to the present. Abundant since Ordovician.
Marine and fresh water.

Class 4. Scaphopoda (boot foot). Tooth shells with tubular shell
and mantle. Cambrian to the present. Dentalium from the
Tertiary to the present. Marine.

Class 5. Cephalopoda (head foot). Cuttle fishes, squids, octopi
and nautili. Bilaterally symmetrical foot divided into arms
with suckers. Nervous system is located in the head.
Nautiloids are first known from the Cambrian rocks; they
reach their maximum development in the Silurian and decline
to the Triassic. Marine.

142

MOLLUSCA 143

Characteristics

1. Mollusca are mostly unsegmented and without jointed ap-

pendages.

2. Symmetry is fundamentally bilateral, but in the Gastropoda

there is superposed dextral or sinistral asymmetry.

3. The foot is usually for locomotion.

4. The mantle is a dorsal fold of the body wall which covers the

animal.

5. Frequently a shell is secreted by the mantle, but sometimes the

mantle and shell are absent.

Natural History

Class I. Lamellibranchiata. Clams and Mussels. — As a type
for study either the fresh water mussel {Anodontd) or the clam
{Venus) proves excellent. Both are bilaterally symmetrical and
have a well-developed foot.

The Structure of the Shell. — " The mussel shell consists of three
layers. The outside horny layer is called the perlostracum; the
middle prismatic layer is formed from tiny prisms of calcium car-
bonate separated by thin layers of the horny conchiolin found in
the perlostracum; the Inner layer Is the nacre or ' mother of pearl *
which consists of alternate layers of calcium carbonate and conchio-
lin arranged parallel to the surface. The perlostracum and the
prismatic layers are secreted from the edge of the mantle, while the
nacre Is secreted from the whole of the epidermal surface of the
mantle." ^

Externally marking the shell, we find rather prominent depres-
sions, three or four in number, called lines of growth. Indicating the
number of seasons of growth. Less prominent depressions, the
lines being close together. Indicate the number of new edges of the
shell laid down by the mantle during the course of a single season.
There are also annual layers of nacre.

Internal Anatomy. — In both forms we find well-developed ante-
rior and posterior adductor muscles. These must be cut in order to
separate the shells. When cut, the dorsal hinge ligament forces the
valves to gape open. Lining both valves we find the mantle. This
is adherent to the shell ventrally just Inside the edge, the point of

1 Parker, T. J., and Haswell, W. A. 1928. Text-book of Zoology. The Mac-
Millan Co., London.

144

MOLLUSCA

attachment, the pallid linCy being readily seen in the cleaned shell.
In the hard-shelled clam^ Venus, which has two well-developed
siphons, we find a posterior invagination under the adductor muscle
called the pallial sinus. It marks the point of attachment of the
siphonal muscles. The siphons of fresh water mussels are very
poorly developed.

Fig. 6 1. Model of clam. (Courtesy of Amer. Mus. of Nat. Hist.)

Digestion. — The mouth has two pairs of labial palps, ciliated
externally; the gullet or esophagus is short. A pair of irregular dark
brown glands, the liver, surround the large stomach which has in it a
slender gelatinous rod, the crystalline style. T. C. Nelson (Biol.
Bull., 1925, vol. 49, no. 2, pp. 86-99) gives three views of the func-
tions of the crystalline style, (i) It contains amylotic ferments
which digest starch. (2) Its mucous or viscid secretion holds the
food long enough for proper digestion. (3) It separates the food
from foreign particles, acting as a " stirring rod."

The intestine passes from the posterior end of the stomach to
the visceral mass, coils parallel to the first portion, then turns
backwards and proceeds as the rectum through the pericardium and
above the posterior adductor muscles, finally discharging into the

MOLLUSCA 145

dorsal exhalant siphon or cloaca. The wall of the rectum has a
longitudinal ridge or typhlosole (as in the earthworm). Two similar
ridges begin in the stomach and are continued into the first part of
the intestine. An oyster is said to strain 135 liters of water daily
to obtain its oxygen and food. GaltsofF, P. (1928, Bull. Bur. of
Fish., vol. 44), has shown that for the North Atlantic oyster the
maximum flow of water is 3.9 liters per hour at 25° C; for the Gulf
of Mexico oysters, it is nearly twice as much, 7.5 liters per hour at
25° C.

Circulation. — The heart consists of a ventricle., surrounding part
of the rectum, and two auricles. The ventricle contracts and drives
the blood through the anterior and posterior aortae. Some of the
blood goes to the mantle where it is oxygenated and then returns
to the heart but not to the kidneys. The rest circulates through
the body and is finally collected by the vena cava just beneath the
pericardium. From the vena cava, the blood passes into the
kidneys and gills to the auricles and into the ventricle. Oxygen
and dissolved food are carried to all parts of the body, CO2 to the
gills, and other wastes to the kidneys.

Respiration takes place through the surface of the mantle, and
by means of a pair of branchiae or gills made up of two lamellae on
each side, united at the edges except dorsally. A lamella is com-
posed of gill folds supported by chitinous rods and covered with
cilia. The cilia of the gills produce a current which sets in through
the inhalant siphon into the mantle cavity and through the ostia
and the water tubes into the suprabranchial (epibranchial) chamber
and out at the exhalant siphon. The ingoing current carries oxygen
for the aeration of blood, and also brings food such as diatoms and
Protozoa, which pass into the mouth between the ciliated labial
palps. The outgoing current carries excreta from the blood and
feces from the cloaca.

Excretion. — The nephridia (organs of Bojanus) are a single pair,
one on each side of the body just below the pericardium. They are
U-shaped tubes bent on themselves and opening at one end into the
pericardium and at the other on the external surface of the body.
There are two parts — a brown, spongy, glandular kidney, and a thin-
walled non-glandular bladder with ciliated epithelium which com-
municates with its mate anteriorly by a large oval aperture. The
kidney receives excreta from the pericardium by cilia. Waste is
carried out through the exhalant siphon. The bladder receives

146

MOLLUSCA

excreta from the blood. Another excretory organ is the pericardial
gland or " Keber's organ." It lies just in front of the pericardium
and discharges into it. It may collect from the kidney; it secretes
uric acid.

Reproduction. — The sexes are usually separate. A few forms
are hermaphroditic and protandrous. The gonads^ situated above
the foot, are paired masses of tubes which open just in front of the
renal aperture on each side. Spermatozoa pass out of the dorsal
siphon of the male and into the ventral siphon of the female. The
eggs pass out of the genital aperture and lie in the gills. They are
fertilized there and develop in a modified pouch or marsupium.
The eggs develop by cell division until in the fresh water mussel a

Byssus

SheU ^:".iA;

Adductor muscle

tfM^JfD

Fig. 62. Glochldium of Anodonta. — A, a young mussel or glochidium. (After
Balfour.) B, the gills of a fish in which are embedded many young mussels forming
"blackheads." (After Lefevre and Curtis.) (From Hegner, College Zoology.
Courtesy of Macmillan Co.)

glochidium is produced. This has a shell with two valves, hooked
in some species, and closed by muscles. The glochidia attach to
the gills or fins of a fish, become surrounded by the stimulated
epithelium of the host, and develop there until able to carry on
independent existence. They are thus dispersed by the fishes to
considerable distance. (Figures 62 and ^^?)

In Venus and many other molluscs, we find that the embryo
develops as a free swimming larva of the trochophore type called a
veliger.

Eggs. — Lamellibranchs have a large number of eggs. The
oyster has 300,000 to 60,000,000 per annum. The fresh water
mussel has 200,000.

Nervous System. — There are two cerebral ganglia (one on each

MOLLUSCA

147

side of the esophagus) with cerebral commissures forming a nerve
ring. Each cerebropleural ganglion sends a nerve cord ventrally,
ending in a sin^t pedal ganglion in the foot. Each cerebropleural
ganglion gives off a cerebrovisceral connective (sometimes enclosed
by the kidneys) leading to a single visceral ganglion.

Fig. 63. Different stages of cyst. Proliferation in glochidia, fin margin of carp.
(After Lefevre and Curtis. Jour. Exp. Zool.^ 19 10.)

Sense Organs. — A patch of yellow epithelial cells, the " osphra-
dium," covers each visceral ganglion. They are supposed to be
olfacto-gustatory organs. Paired otocysts (statocysts) with calcareous
statoliths behind the pedal ganglia are organs of equilibrium.
Yves Delage removed the otocysts and caused lack of balance.
The edges of the mantle have sensory cells — especially on the
inhalant siphon — which are sensitive to light and touch. Pecten, the
scallop, has from 80 to 120 ocelli at the edge of the mantle. They
are connected with the branchial ganglion and each has cornea,
lens, and optic nerve. Apparently visual organs are absent in the
fresh water bivalves, but they are better developed in the marine
forms along shore. There is no satisfactory evidence for color
vision in Mollusca. Certain eyeless species react to sudden darken-
ing very quickly, but soon get used to stimuli and cease to respond.
The sense of geotropism ^ is determined by obscure conditions.
Reactions are influenced by size of illuminated or darkened surface,
as well as by intensity of light.

Class I. Lamellibranchiata. — Fresh water mussels or clams
( Unionidae, Anodontidae, Lajnpsilidae) have assumed considerable
importance in America. The United States Bureau of Fisheries has
established a Biological Station at Fairport, Iowa, for the artificial

^ See page 25 for definition of tropisms.

148

MOLLUSCA

propagation of mussels in the Mississippi basin. Valuable pearls
are secured from the adult mussels, and pearl buttons are manu-
factured from certain mussel shells. Their larvae (glochidia),
parasitic on the gills and fins of fishes, become dispersed widely.
(Figure 64, A and .S.)

Fig. 64//. Unto gibbosus Barnes. (After Simpson, U. S. B. F. Bull., 1898.)

The sa/f water or edible mussel {Mytilus edulis), cultivated for
many years in France and England, has only recently come into
general use in the United States. Through the activities of the late

Dr. I. A. Field,3 the
many mussel beds on
the Atlantic coast are
now being utilized. In
mid-summer, mussels
may sometimes become
poisonous.

The " pearl-oyster "
(Meleagrina), which is
not a true oyster but a
mussel, is found in the
Fig, 645. Lampsilis luteolus La. Female. (After South Sea Islands, Ja-
Simpson, U. S. B. F. Bull., 1898.) pan, Ceylon, the East

Indies and the West
Indies. Pearls are an accumulation of layers of " nacre " laid down
around foreign substances. (See page 157, Culture Pearls.)

The softs helled clam {My a arenarid)^ sometimes called the long-

^Field, I. A. 191 1. The food value of sea mussels. Bull. Bur. Fish., vol. 29.

MOLLUSCA

149

necked clam, is preferred by New Englanders for clam bakes and
chowders. It has extremely long siphons. The quahog ( Venus
mercenaria), or hard-shell clam, is found along the entire Atlantic
coast. Used little at the coast, it is preferred inland as it can be
shipped long distances and kept alive for a considerable time. Blue-
lined ones were used as money " wampum " by the American
Indians (Figure 65, A and B). The giani clam {Tridacna gigas) is

Fig. 65. y/, soft shell clam, M\a. B, razor shell clam, Ensis.

Courtesy of The Century Co.)

(From Arnold.

found in tropical waters where it sometimes proves a menace to
divers. Its shell may weigh five hundred pounds and reach a
length of four feet. A single valve may be found in use as a church
font. The razor-shell clam {Solen maximus) is eaten by the poorer
people of the British Isles, but not known in fashionable restaurants.
The giant " geoduck " clam of the Pacific coast {Glycimeris generosa)
reaches a weight of six pounds and has a siphon sometimes extended
twenty-four inches. The West Coast ''little neck" clam {Tapes
staminea) is an important food. The cockle {Cardium edule) is
eaten considerably in Europe. It is easily digested.

The scallop (Pecten irradians) found off-shore on the Atlantic
coast does not reach a diameter greater than three inches. Its
single adductor muscle is used for food. The giant scallop {Pecten
maxijnus) is found in deeper water and reaches a diameter of seven
inches. Both the scallops are extremely rich in iodine and should
be utilized more inland since they keep on ice in a much better
condition than do oysters. The crusaders brought with them from
the Holy Land a Mediterranean scallop {Pecten jacoboeus) which
they wore as a badge, indicating their foreign service.

I50

MOLLUSCA

The oyster [Ostred) "* is sessile and lacks a foot. It is used in
America more than any other shell fish and has been popular in spite
of the occasional occurrence of typhoid carried by freshened oysters.
The practice of transporting oysters from relatively clean salt water
to the mouths oi polluted t'xy&vs and there keeping them " floating "
until they have become bloated and swollen and have lost their
true ocean flavor is one that has brought oyster dealers additional
money when they sold oysters by the quart, but has lost many lives
from the typhoid germs collected.

Fig. 66. Mussel with Buddha images. Chidester. {Sci. Am. Supply 191 5.)

The window-glass shell ( Placuna placenta) is used in the tropics
for windows in churches and other buildings. Reese reports that
the demand for " window pane " shell in the Philippine Islands
has recently exceeded the supply, so that the Philippine Bureau of
Science planted new beds.

The wood-boring ship-worms {Teredo and Bankid) were in early
days a formidable enemy of wooden ships. Recently it was dis-
covered that the wood-boring ship-worm, Teredo navalis^ was doing

^ Brooks, W. K. 1905. The Oyster. Bait.

MOLLUSCA

151

great damage to the piles in Pacific and Eastern harbors/ At-
tempts by the United States Navy to protect wharves and piles

IS

Fig. 67. Teredo navalis. Age five weeks from metamorphosis. 6", shell ;F, foot; /j,
incurrent siphon; es, excurrent siphon;/), pallet. (B. H. Grave, Biol. Bull., Oct. 1928.)

A

have resulted in the sheathing of some docks with concrete

pregnation of the piles with creosote has also

given a large measure of protection (Figure

67). The borer {Pholas) is able to penetrate

rocks and cement. It has extremely long

united siphons and a shell with a file-Hke

surface.

Class 2. Amphineura. (Figure 68.) — The
chitons are bilaterally symmetrical molluscs
with eight calcareous plates or shields which
protect the dorsal surface of their boat-shaped
body. Like the wood louse and armadillo
they are able to roll themselves into a ball for
protection. In some species the shell plates
have between eleven thousand and twelve
thousand primitive visual organs. Chitons

Im-

Fig. 6 8. Chiton.
(From Hertwig-Kingsley,
Manual of Zoology.
Courtesy of Henry Holt
&Co.)

^ Grave, B. H. 1928. Natural history of shipworm. Teredo navalis, at Woods
Hole, Mass. Biol. Bull., vol. 55, no. 4, pp. 260-282.

Hill, C. L., and Kofoid, C. A. Marine Borers and Their Relation to Marine
Construction on the Pacific Coast. Final Report of the San Francisco Bay Marine
Piling Committee. 1924.

Sigerfoos, C. P. 1908. Natural History, Organization and Late Development
of the Teridinidae or Shipworms. Bull. U, S. Bur. Fish., vol. 27, p. 191.

152 MOLLUSCA

are found in shallow water, and are used as bait and for food.
One Pacific coast species reaches a length of eighteen inches.

Class 3. Gastropoda. — The Gastropoda differ from the Lamelli-
branchiata considerably, in that they usually have a spirally coiled
shell consisting of a single piece, a head region with eyes and sensory
tentacles, and in the alimentary canal have a buccal organ, the
odontophore^ bearing rows of chitinous teeth and functional in rasping
food and in cutting through other shells. Gastropoda creep slowly
on a ventral foot, which in the marine snails carries a horny opercu-
lum used in closing the orifice when the foot is retracted.

The chank-shell {Turbinella pyruni) , found in the Indian Ocean,
is used in the East Indies for bangles. When cut into armlets and
anklets, chanks are worn by the women of Hindustan. Chank-
shells were also used for beating cloth. The whelk {Buccinum) is
eaten by some Europeans. Another whelk {Purpura) was used
by the ancients in the production of " Tyrian Purple." The
Romans secured their dyes from shells found off the coast of Tyre
in Asia, and at Meninge on the shore of Africa. Pliny speaks of the
mixture of dyes of different shades to produce the finest purple for
royal robes. The slipper limpets {Crepidula Jornicatd) are de-
generate scale-like animals that in many cases become attached
permanently to a stone or dead shell by a stony cement secreted by
the foot. The embryology of Crepidula was the subject of an
authoritative study by Conklin (Jour, of Morphology, vol. 13, 1897).
The common limpet {Patella vulgata) is used as food in England and
on the Continent much more than in the United States. The ear-
shells ( Haliotis) found on the Western coast of America appear like
the single valve of a Lamellibranch, but they are true gastropods.
The shells are used for the manufacture of ornaments, in inlays
and also for making buttons. They also yield blister pearls of
brilliant colors. The fleshy foot of the animal is an excellent food,
which has been eaten in Europe and the Orient for centuries, and
furnishes abalone steak in California. It is also dried and shipped
to the Orient. The cowries {Cypraeidae) are used for ornaments,
to sink fishnets, and as money. A small species {Cypraea moneta)
is used in Siam and Western Africa as money. Lankester mentions
the fact that in the Friendly Islands the orange cowrie, a symbol of
rank, is worn only by the chief of the tribe.

The helmet shells {Cassidae) are used in the manufacture of
cameos^ since either white or black may be carved with the other as

MOLLUSCA

^S3

a background. The tritons or sea conchs {Tritonidae) reach a
length of twelve inches. The South Sea Islanders use one species
as a trumpet.

The common periwinkle {Littorina)^ used as food in Europe,
particularly the British
Isles, is not so popular in
America, although it occurs
along the Atlantic coast.

The oyster drill ( Uro-
salpinx cinereus) is an im-
portant enemy of the
Lamellibranchs. Using its
" radula " it quickly bores
holes into the hardest shell.
(Figure 69, A and B.)
The drilling sea snail
{Natica heros) deposits its
eggs in a " collar " com-
posed of sand, agglutinated
by mucus. The land snail
{Helix pomatia)^ imported
from Europe, is sold in
large cities and considered
a delicacy. The American
Helicidae are smaller in
size and are considered by
some vegetable gardeners
to be quite injurious to
plants. The escaped Euro-
pean garden snail is very
destructive to certain veg-
etables and flowers. Pliny
speaks of snails, cultivated
by the Romans, with shells
that would hold a quart of
wine! The modern snails are not more than three or four inches

lo"g- ^ . ...

The common pond snails include the genus Limnaea with its

shell a right-handed spiral, which lays its eggs in the spring in

capsules covered with jelly; and the genus Physa (in which the

Fig. 69. Enemies of the oyster. A, Uro-
salpinx, the drill; B, Fidgur, the whelk.
(From U. S. B. F. Report, 1897.)

154

MOLLUSCA

spiral is a left-handed one), which attaches its egg capsules to sticks
and leaves in the water. Either form is excellent for the study of
embryonic development, since the eggs are deposited in laboratory

aquaria and develop rapidly. (Figure 70, A
and 5.)

The land slugs {Limacidae) have a vestigial
shell. A species found in California reaches the
length of twelve inches. The giant slug {Arioli-
?nax sp.) is used by the South American Indians
in the manufacture of " bird lime " to capture
Fig. 70. Left, hummingbirds.

Lymnaea with dex- om c ^ '^ j J*1*~

^ , , ,, „. , ^ Snails are of great sanitary and medical sig-

tral shell. Right, , r . 1 j •.•

Physa with sinistral nincance as hosts ot larval trematodes, parasitic

shell. in vertebrates, including man. (See p. 77.)

Class 4. Scaphopoda. — The tooth shells or

tusk shells have a tubular calcareous shell open at both ends. The

foot is at the larger end. A lingual ribbon (radula) is present, and

the animal has a rudimentary head. Tentacles, eyes, a heart and

gills are absent. The captacula are ciliated contractile filaments

perhaps for breathing and securing food. The animal has the

univalve shell and radula of the Gastropoda and the symmetry

and pointed foot, without tentacles or head, that characterize the

Lamellibranchiata.

The Dentalium or iusk shell was used in California among the
Indians and the early whites as currency. The shells used were
valued at ^5.00 each if about two and one-half inches long; smaller
ones were about one inch long and were worth about ^oi. An eleven-
shell string was worth about I50.00. Dentaliums were traded for
wives, clothing, furs, and woodpecker scalps, whose red topknots
were of considerable value also.

Class 5. Cephalopoda. — The Cephalopoda, which include the
squids, sepias and octopuses, are highly developed marine Mollusca.
They have a true head, with well-developed eyes and olfactory
organs, and the anterior portion of the foot is modified into tentacles
or arms. The body is bilaterally symmetrical. Locomotion is
accomplished by movements of the tentacles and by expulsion of
water from a funnel or siphon leading out from the mantle cavity.
The shell is usually internal, that of the cuttlefish being sold as
" cuttle-bone," but in the Nautilus, the shell is highly developed as
a chambered external coiled structure.

MOLLUSCA

HS

The cuttlefishes^ or Sepias, have ten arms and a pair of highly
developed eyes. The body is covered by the mantle. Cuttle-
bone comes from the inner shell, which is very porous and light in
weight and largely lime. Cuttlefishes furnish sepia ink which is
used in art. Ground cuttlebone called " pounce " is used somewhat
in medicine as an anti-acid and when powdered fine is used by
draftsmen to prevent blotting. Italians esteem the " sepias " a
delicacy. India ink is made from the ink bags of fossil cuttlefishes.

The octopus {Octopus vulgaris) bears eight arms. It may reach
a length of fifteen feet and weigh seventy-five pounds. Terrible
stories are related (at a few dollars a column) regarding the battles
of divers with these horrible " devil fishes." They are used for
food by the Chinese and Italians.

Fig. -jiA. Female Argonauta argo. (Lull, Organic Evolution, after Claus-Sedgwick.

Courtesy of Macmlllan and Co., Ltd.)

The squid (Loligo) reaches a length of about one foot. The
internal shell, called the " pen " on account of its resemblance to a
feather, is relatively thin and chitinous (horny), not calcareous.

6 The Arctic cuttlefish is said to reach a length of eighteen feet, its size being ap-
parently correlated with the greater abundance of diatoms and other food in the
plankton of northern waters.

156

MOLLUSCA

Giant squids may reach a total length of thirty feet, the body being
not more than ten feet long. They form the food of the sperm
whales. Squids are used for bait and are eaten by French, Italians,
and the Orientals. Squid oil has been used for lubricating, and by
the Chinese as a medicine.

The chambered nautilus {Nautilus pompilius) is a cephalopod
with a many-chambered, spiral shell, lined with beautiful pearly
nao'c. Unlike the squids and octopi, the nautilus lacks an ink sac
and cannot change its color. Oliver Wendell Holmes' celebrated
poem has immortalized " The Chambered Nautilus."

The paper nautilus {Argo-
nauta argo) with a thin shell is
more active than the chambered
variety and is frequently seen
near the surface of the ocean.
The females are pelagic during
breeding season, but are found
in the depths the rest of the
time. The male Argonaut, one
inch long, only i/io of the size
of the female, has no shell, and
is able to detach the third arm
on the left side laden with sper-
matophores and spermatozoa.
The entire " hectocotylized
arm " passes into the mantle
cavity of the female and, at-
FiG. 7i5. Male Argonanta showing taching, permits the spermatozoa
hectocotylized arm. (Lull, Organic Evo- ^^ fertilize her eggs. (Figure 71,

A and B.)

Pearls. — Since so much of
the reputation for economic importance of the Mollusca depends
on the value of pearls, let us consider the source of pearls and
the methods used in producing " culture pearls."

Composition. — The composition of pearls is 91.72 per cent
carbonate of lime, 5.94 per cent organic matter and 2.34 per cent
water.

Source and Value. — The pearl " oyster," one of the Aviculidae,
Margaritifera, is not an oyster but a mussel. It is found in the
Persian Gulf and off the coasts of Ceylon and Japan. Similar forms

lution, after Claus-Sedgwick.
of Macmillan and Co., Ltd.)

Courtesy

MOLLUSC A 157

have been found in the Philippine Islands and on the coasts of
Venezuela and Pacific Mexico. Black pearls from the " pearl
oyster " of the Gulf of Mexico are extremely valuable. The fresh
water mussels, besides furnishing pearl buttons, also produce a
fine quality of pinkish pearls. The abalones {Haliotis) found in the
Pacific Ocean produce very few good blister pearls but the shells are
valuable for mother of pearl. Pink pearls are sometimes secured
from the large West Indian conch shell, Strombus gigas^ one of them
having sold for five thousand dollars.

True pearls increase in value notably according to the size. If
a one-grain pearl is worth ^10.00, a two-grain pearl is worth ^40.00,
while a ten-grain pearl is valued at ^1,000.00.

Culture Pearls. — The nucleus of a pearl may be a parasite, an
ovum, a fragment of tissue, or a bit of shell or other hard material.
Investigators have found Cestode larvae, Trematode worms, and
even small Crustacea and Hydrachnids as the nuclei of pearls.
Centuries ago the Chinese discovered that if foreign substances were
placed between the mantle and shell of a mussel, in many cases a
coating of " mother-of-pearl " was laid down over the insert.

The Japanese developed the earlier work of the Chinese to a
great enterprise under the guidance of the late Prof. Mitsukuri,
opening the oysters slightly and inserting bits of sand, images, and
bits of mother of pearl, with the result that blister or culture pearls
were produced. In 1892, Kokichi Mikimoto, the " Pearl King,"
following the suggestions made to him by Professor Mitsukuri,
began the cultivation of pearls on a large scale. Mikimoto's oyster
beds extend over 40,000 acres. According to Jordan (1927) he
employs one thousand people. The divers are all young women who,
it is reported, can remain two minutes under water.

Culture pearls with a spherical mother-of-pearl nucleus are just
as aesthetic as a natural pearl, which may be the " sarcophagus "
of a tape-worm. In spite of attempts to bar them from the market
as genuine, they are now sold for as much as $200 each. Chemically
and biologically they are true pearls.

Coated Glass Substitutes for Pearls. — Alabaster or glass beads
are now coated with pearl essence secured by the extraction of
guanin crystals from herring and other fishes (see page 254) and are
sold as artificial pearls.

158 MOLLUSCA

References on Pearls

Chidester, F. E. 191 5. Artificial production of pearls. Sc. Am.,

Supp. No. 2043, Feb. 1 91 5, p. 140-
Jordan, D. S. 1927. Mikimoto and the culture pearls. Sc. Am., Oct.

I927> PP- 300-302.
Tressler, D. K. 1923. Marine Products of Commerce. N. Y.

General Consideration of the Mollusca

Distribution. — Mollusca are found in both fresh and salt water,
and on land. While they are usually free-living, they serve as
obligatory intermediate hosts in the development and transmission
of certain parasitic worms, such as the lung and blood flukes of man,
and are also found in association with some of the aquatic Crustacea,

Physiology. — The soft bodies of the molluscs are protected by a
slimy covering frequently supported by a shell. Certain of the
gastropods and cephalopods lack such a shell.

In the Lamellibranch, Pecten^ the two valves are rapidly opened
and closed and the animal flaps along at considerable speed. Other
forms like the long-necked clam {Myd) utilize their siphons in bur-
rowing while the majority move slowly by means of the foot. The
oyster is sessile in the adult condition. In certain Gastropoda there
is a slow wave-like muscular motion of the foot; whereas in other
species locomotion is accomplished by ciliary activity (Copeland '').
The Cephalopoda when undisturbed move slowly by means of the
tail fin and sometimes by " walking " on the arms, but they are
capable of very rapid backward movement by jets of water ejected
from the " funnel " or siphon.

The Mollusca have a well-developed body cavity usually divided
into two chambers, the pericardial and the visceral. Digestion is
facilitated by the secretions from the hepato-pancreas or " liver."
The Gastropoda have a highly developed lingual ribbon, the
" radula," which is instrumental in the penetration of hard shells.
Snails are able to digest cellulose without the aid of bacteria. In
Cephalopoda a salivary secretion is poisonous enough to paralyze
small crabs. The devil-fish or octopus has acid-secreting glands
which soften the shells of oysters at the point of drilling. Teredo
feeds in part on the wood from its burrows filed off by its shell.

" Copeland, M. 1919. Locomotion in two species of the gastropod, Alectrion.
Biol. Bull., vol. 37, no. 2, pp. 126-138.

MOLLUSCA 159

Many of the snails respire by means of air taken into the mantle
cavity which functions as a lung. Other aquatic forms breathe by
means of gills. Pinna-globulin is a pigment in the blood of the
Lamellibranchs. Pinna squamosa has manganese instead of the
copper common to invertebrates, including oysters, but it does not
appear to function in transporting oxygen.

Many gastropods and cephalopods have haemocyanin, and in
the Gastropod Planorbis, haemoglobin occurs. (Redfield, personal
communication.)

Nervous System. — The nervous system of the MoUusca consists
of cerebral, visceral and pedal ganglia, with connectives. In the
Gastropoda, the coiled shell causes the nervous system to be in a
spiral.

It is said that the smallest snail can withstand more strychnine
than an adult man. Richards has shown « that Mytilus is poisoned
readily by atropine and camphor and less so by caffeine.

Regeneration. — Autotomy is not characteristic of moUusca in
general, but a few Lamellibranchs and Gastropods are able to part
with and regenerate a new bit of their foot.

Growth Studies on the MoUusca. — Molluscs are especially
suited for studies of the growth of animals because the shell is added
to and extended by the mantle as the organism grows. The amount
added in a given time, or the rate of growth, depends on the amount
of food that the animal receives. During the winter the animals
get little food and the edge of the shell thickens leaving a growth
ring or check mark when the growth begins again early the next
spring.

On Cape Cod, Massachusetts, the growth of the edible mussel
{Mytilus) begins in March following the great increase of its food
(plankton) in January and February .^ The growth rings of the
Pacific Coast razor clam {Siliqua) appear very clearly so that
Weymouth i" and his associates have been able to extend our views

8 Richards, O. W. 1929. Conduction of the nervous impulse through the pedal
ganglion of Mytilus. Biol. Bull., vol. 56, pp. 32-40. Richards has shown that the
rate of conduction of the nervous impulse was 92.9 ± 2-2, cm. per second in Mytilus
edulis at 24° C.

9 Richards, O. W. Studies on the growth of M. edulis and calijornianus in progress
communicated personally to the author.

10 Weymouth, F. W., and McMillin, H. C. 1930. Relative Growth and Mortality
of the Pacific Coast Razor Clam and Their Bearing on the Commercial Fisheries.
Bull. U. S. B. F., vol. 46, pp. 543-567-

i6o

MOLLUSCA

of the nature of the growth process from the analysis of measure-
ments of the growth of this clam. Other forms do not show these
rings clearly so that Richards has used x-ray pictures to show the
internal structure of the shell not visible to the unaided eye. The
growth of many shells takes place in an orderly manner and in some
cases in precise mathematical form such as the logarithmic spiral
formed by the chambered nautilus. ^^

Embryology. — The eggs of the MoUusca are extremely numerous.
In the oyster, it is estimated that there are 60,000,000; in the squid
as many as 40,000. The sexes are usually separate except in the
Gastropoda. (Figure 72.)

\

■v, ■-.

[

/

Fig. 72. First stages in embryonic development of the pond snail {Lymnaeus):
fl, egg cell; b, first cleavage; c, second cleavage; d, third cleavage; e, after numerous
cleavages (Morula);/, blastula (in section); |", gastrula just forming (in section); h, gas-
trula completed (in section). (After Rabl.) This may be taken as a type of the
earliest development of all many-celled animals (Metazoa). (From Jordan and Kel-
logg, Animal Life. Courtesy of D. Appleton and Co., Publishers.)

Most larval molluscs include a trochophore stage, which becomes
a veliger larva. The velum is situated anteriorly to the mouth and
proves extremely important in the locomotion and dispersal of the
animal. In the fresh water mussels, a parasitic stage, the glochidium
(see page 148) attaches to the gills or fins of fishes.

Care of the Young. — In certain of the Gastropoda, the eggs hatch
within the body of the parent. In one form the female {Galerus
chinensis) hatches her eggs by keeping them between her foot and

" Thompson, D. A. W. 1917. Growth and Form. Camb. Univ. Press.

MOLLUSCA

i6i

the stone to which she adheres. The octopus broods her eggs,
renewing the water around them by siphonal jets.

Fossil Relatives. — As indicated on page 1 42, under Classification of
Mollusca, they are found from the Cambrian to the present, the La-
mellibranchs being especially abundant in the Cretaceous of America.

Ancestry and Relationship to Other Phyla. — On account of the
occurrence of the trochophore larva the Mollusca are linked with the
worms. The Cephalopoda are separated from the other Mollusca,
having no free larvae and being provided with highly developed eyes
and nervous system.

Economic Importance of Mollusca

Class Positive

Lamellibranchiata. i. As money. Quahaugs and cowries, i.

1. Pearls. Pearl oysters, clams and
mussels.

3. Buttons from mussel shells.

4. As ornaments.

5. Food — oyster, clam, mussel, scallop

(adductor muscle), shells as chick- 2.
en grits.

6. For roads (New England uses oyster

shells).

7. As church fonts — Tridacna (500 lb.

shells).

8. Window pane (Placuna).

Negative

a. Pholas — "borer."
b. "Ship-worms."
Teredo navalis and
Bankia fimbriata
attack wooden
ships and piles.

Giant clam. Tridac-
na gigas (enemy of
divers).

Gastropoda.

I. For food or bait. Whelks, periwin-
kles, top shells, limpets, the aba-
lone (Haliotis).

1. For buttons and as ornaments.
Ear shells, sea snails, cameo shells
(Cassis), top shells. Queen conch
shells {Strombus gigas) were for-
merly used in Liverpool for the
manufacture of porcelain.

3. For dye stuffs the "sea hare" fur-

nishes purple dye. "Tyrian pur-
ple" {Purpura, the whelk).

4. For bird lime. The giant slug is

used by South American Indians
to lime humming birds.

5. The calcareous front doors (oper-

cula) of some S. American gastro-
pods are sold for use in the U. S. as
"eye-stones."

1. Boring gastropods at-
tack lamelli-
branchs.

1. Destroy vegetables
and plants — gar-
den snail (slug)
Limax.

3. Sometimes snails at-

tack the eggs of
fish in nests.

4. Intermediate hosts of

larval stages of
flukes of man.

l62

MOLLUSCA

Amphineura.
Scaphopoda.

I. Chiton used as food and for bait.

I. Tusk shells (Dentalium) were used
as currency in California by the
Indians.

Cephalopoda.

I. Little known except
in fiction.

1. Sepia "bone" and "cuttle bone"
used to feed birds requiring lime.

2. Dr. J. A. Eiesland cites the use of

cuttlebone for erasers in Norway
about 1870.

3. "Pounce" as anti-acid (medicine);

in art work to prevent blotting.

4. Sepia — for ink.

5. Squid oil — medicine and as lubricant.

6. Food and fish bait. Squids, octopi

and sepia.

References on Mollusca

Cooke, A. H. 1895. Mollusca, in Cambridge Natural History, Mac-

millan Co.
Gould, A. H. 1870. Report on Invertebrata of Massachusetts. 2d ed.

Binney (Mollusca and Tunicata).

Johnson, M. E., AND Snook, H. J. 1927. Shore Animals of the Pacific
Coast. The Macmillan Co., N. Y.

Simpson, G. B. 1901. Anatomy and Physiology of Polygyra albolabris
and Umax maximus, etc. New York State Educational Depart-
ment.

Tressler, D. K. 1923. Marine Products of Commerce, N. Y.

Verrill, a. E. 1882. Report on the Cephalopods of the Northeastern
Coast of America. Report of U. S. Fish Commission for 1879.
Government Printing Office.

CHAPTER XII

Arthropoda

The Arthropoda (Gr. arthron^ a joint; pous^ a foot) include
more than one-half the number of species in the animal kingdom
and comprise a wide variety of forms, with great significance econom-
ically.

The body, segmented and bilaterally symmetrical as in the
Annelida, is covered by a chitinous exoskeleton. The heart is
usually elongated and the nerve cord is ventrally situated, while
the cerebral ganglia are dorsal and anterior as in the earthworm.

This Phylum includes insects, barnacles, crabs, crayfishes,
spiders, ticks, and scorpions. The bee is an example of a beneficial
form; the housefly, of an injurious type.

Classification

Class 1. Crustacea.

Class 2. Onychophora.

Class 3. Myriapoda.

Class 4. Insecta.

Class 5. Arachnid a.

Characteristics

1. Marked metamerism.

2. Appendages jointed.

3. Body covered by chitinous exoskeleton, secreted by cells beneath

it.

4. Bilateral symmetry.

5. Mouth and anus at opposite ends. '

6. Seldom ciliated.

7. Muscles usually striped.

8. Dorsal heart, with incomplete circulatory system, the blood

sinuses extremely important.

9. Nervous system includes a ventral nerve chain with ganglia and

paired dorsal cerebral ganglia.

164

ARTHROPODA

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ARTHROPODA 165

Natural History

Class I. Crustacea. — Crustacea vary in size from microscopic to
the 34-pound lobster. Nearly all have a hard exoskeleton. They
shed this and grow for a time. Young crayfishes and lobsters
moult 8 times the first year, 5 times the second year, 3 times the
third year and from one to three times annually, thereafter. They
are divided into the head, thorax and abdomen. The head and
thorax are frequently fused to form a cephalothorax. There are
usually 21 segments in higher Crustacea. Seven is the typical
number of abdominal segments. There are eight in the cephalo-
thorax (5 legs and 3 appendages) and six in the head.

Subclass Malacostraca. Order Decapoda. Type — Lobster or
Crayfish. (Figure 73.) Digestive System. — This consists of the
esophagus, cardiac stomach, pyloric stomach, intestine, and liver.
The esophagus is lined by chitinous cuticle and supplied with small
" salivary " glands. The cardiac stomach contains the gastric mill,
which is equipped with powerful chitinous teeth, the most important
being the two laterals and the single dorsal. The posterior pyloric
stomach has a sieve-like strainer of coarse hairs. The short mid-gut
receives the secretions from the lateral liver or hepato-pancreas.
This gland absorbs peptones and sugar, manufactures glycogen and
furnishes enzymes corresponding to the gastric and pancreatic
juices of mammals. The intestine is long and straight, except for a
slight dilatation in the sixth abdominal segment, the rectum. An
intestinal cecum is dorsally situated. Chitin-lined, the intestine
has but few glands. Both mouth and anal opening are ventrally
situated.

Circulatory System. — The blood is a colorless liquid with amebo-
cytes. In Crustacea., hemoglobin is replaced by a fluid containing
copper instead of iron, which is called haemocyanin. It is colorless
when flowing, but turns plumbago colored when exposed to the air.
The heart is shield shaped with three pairs of ostia. There are seven
arteries and many sinuses. The ophthalmic artery supplies the
esophagus, stomach and head. Two antennary arteries supply the
stomach, antennae and excretory organs. Two hepatic arteries
supply the digestive glands. There are also dorsal abdo?ninal arteries,
the sternal artery which passes through the spinal cord, the ventral
thoracic, and the ventral abdominal.

Circulation of the Blood.— The heart sends the blood to the
arteries, capillaries, sternal sinus, and to the^///j where it is purified.

1 66 ARTHROPOD A

It returns from the gills to the cardiac sinuses, pericardial sinus and
back through the ostia to the heart. There are valves in the arteries
and sinuses.

Respiration is by means of gills. Astacus, the crayfish found
west of the Rockies, has i8 pairs; the lobsters have 20 pairs and
Cambarus, east of the Rockies, has only 17 pairs.

Excretion. — Paired, flattened " green-glands " are found in the
ventral region of the head near the esophagus.

Reproductive System. — Ordinarily the sexes of the lobster and the
crayfish are separate, although Turner has recorded many interesting
cases of hermaphroditism in the crayfish. The essential organs of
reproduction in the male are the bilobed testis, the paired vasa
deferentia transporting the sperms to the outside, and the modified
abdominal appendages, called stylets, which are used to transfer
the spermatozoa to the ventral pouch (seminal receptacle) of the
female.

In the female, the bilobed ovary sends off eggs which pass from
the paired oviducts and are fertilized by spermatozoa stored in the
ventral pouch at the time of conjugation, sometimes months pre-
viously. A lobster from 8 to 10 inches long produces from 3,000
to 100,000 eggs in a season. The crayfish may produce 2,000 eggs in
a season. Each egg is attached to one of the swimmerets and
hatches in about two months, the larvae undergoing two or three
moults before they leave the mother, and moulting 8 times the first
summer.

The Nervous System consists of a l^rain (two cerebral ganglia)
and a ventral nerve cord with esophageal connectives uniting the
cerebral ganglia and the nerve cord in the sub-esophageal region.

The ventral cord shows by the great number of concentrated
lateral nerves as well as by the marked enlargement in the anterior
thoracic region that the right and left halves of the ventral cord
have fused. To a limited extent this fusion is evident in the ab-
domen.

The ganglia of the last three cephalic and the first three thoracic
segments have united forming a large compound sub-esophageal
ganglion. Between the fifth and sixth thoracic ganglia the ventral
nerve cord is separated widely to permit the passage of the sternal
artery which runs dorsi-ventrally. There are 12 ganglia belonging
to the nervous system. The brain supplies the eyes, antennae and
antennules. (Figure 74.)

ARTHROPODA

167

Senses of the Crayfish. — Touch is the most
valuable sense. Crayfish are sensitive, to touch
over the whole body, especially on the chelae
and chelipedsy mouth parts, the ventral surface
of the abdomen and the edge of the telson.

Vision. — The compound eyes are almost
worthless for detecting the forms of stationary
objects, but good for moving objects. The re-
sponse is not due to any change in the intensity
of light such as that caused by a shadow falling
on the animals, for they react to a movement
made on the opposite side of them from a
window. Crayfish are sensitive to a strong light
and hide during the day under stones, among
the roots of plants near the bank, or burrow
into the bank. They retreat from a strong
light, but approach a dim one.

Smell and Taste. — Bell applied meat juice to
various parts of the body of the crayfish and
found that the antennae^ antennules, mouth
parts and chelipeds were especially sensitive.

Holmes and Homuth found that the outer
rami of the antennules bearing the olfactory
setae were especially sensitive to olfactory
stimuli, that the inner rami of the antennules
and the antennae^ the mouth parts, and the tips
of the chelipeds were all sensitive to some extent
to olfactory stimuli. Crayfish have a highly
developed topochemical or contact-odor sense.
The crayfish is sensitive to food when not in
contact with it. Experiments with freshly cut
meat and with meat on which the cut surfaces
had dried showed that the crayfish prefers fresh
meat, probably because it locates it sooner.

Hearing. — Bell learned that the crayfish has
no sound reactions, but is sensitive to vibrations

Fig. 74. The central nervous system of the lobster.
(After Calkins, Biology. Courtesy of Henry Holt & Co.)

1 68 ARTHROPOD A

in the water. Huxley said, "the crayfish has nothing to say to
himself or anyone else."

Equilibrium. — Bunting found that young crayfish with the stato-
cysts removed would swim upside down as readily as right side up.
It is also pretty certain that older crayfish have a sense of equilib-
rium, although the response to rotation in their case is not definite,
but purely individual.

In an experiment by Kreldl, shrimps recently moulted and lack-
ing statoliths were placed in filtered water and furnished iron filings
which they at once popped into their statocysts. By means of an
electromagnet he directed their movements, the animals orienting
according to the combined forces of the magnet and of gravity.

Eyes. — The compound eyes have about 2,500 visual rods, called
ommatidia.

Food of the Lobster and Crayfish. — Lobsters eat conchs, /^cotypus
(oyster drill), dead and live fish, eelgrass and My a arenaria (the long-
neck clam). In order to secure hard-shell clams ( Venus) they must
dig holes 2 feet in diameter and 6 inches deep. Crayfish are omniv-
orous. Some crayfish eat a great deal of vegetable matter; one
species, the chimney builder, Cambarus diogenes^ seeming to prefer
it. The vegetable matter eaten consists of dead leaves, potato,
onion, young corn and buckwheat. The animal food consumed by
the crayfish consists of worms, insects, insect larvae, a few fish, frog,
toad and salamander eggs, and occasionally a dead fish or frog.
Both lobsters and crayfish are cannibalistic. Sometimes females
eat eggs from their own abdomens and devour their own freed
offspring.

Enemies. — The chief enemies of the lobster, besides man, are
the codfish, trematodes, and gregarines. The gregarine protozoan
Porospora gigantea is a parasite on the lobster's intestine reaching
a length of two-thirds of an inch. The crayfish suffers from internal
and external enemies. Among the plants which live with the cray-
fish are diatoms, bacteria and saprolegnia. Internally, Distoma
cerrigerum and Branchiobdella have been noted. Besides man,
many small animals find crayfish palatable.

Many fish, including the black bass, Micropterus, which fisher-
men find very partial to crayfish, eat them. Surface reports that
the salamanders Cryptobranchus allegheniensis and Necturus
maculosus are among the chief enemies of the crayfish. Ortmann
mentions seeing the water snakes, Natrix sipedon and A^. lebens.

ARTHROPOD A 169

when captured, disgorge crayfish and has found garter snakes,
Eutaenia sirtalis, in the holes of Cambarus tnonongalensis. The
common box turtle catches many crayfish. Many birds, including
the eagle, king-fisher, wild ibis and turkey, have been observed with
crayfish in their claws; or the remains have been seen at the nests.

Economic Loss from Crayfish. — The river species do not espe-
cially injure human interests except in occasionally capturing a few
toads, fish and frogs, but the burrowing species are cited by Ortmann
as being very injurious, especially in the lowlands of Pennsylvania,
Maryland and West Virginia. They make mud piles which clog
harvesting machines, and are considered by the farmers of Maryland
as such pests that it is common to throw unslacked lime over the
fields in order to kill the unwelcome tenants. West Virginia farmers
claim that the crayfish destroys crops of buckwheat, corn and beans
by eating the young sprouts. Great damage is done by the bur-
rowing species, Cambarus diogenes, in burrowing into dams on ponds
and reservoirs, a notable instance being the levees of the Mississippi.

To destroy crayfish it is customary to throw unslacked lime over
the field, or to pour carbon bisulphide into the holes, or to drain the
infested area. None of these measures is efficacious, the first two
methods being impracticable on account of the difficulty in reaching
the bottom of the burrow and the last, simply lowering the water
level, only delays matters a little.

Economic Gain from Crayfish. — With the lobster fishery in a
state of decline, it seems as if the crayfish could be profitably sub-
stituted for its larger cousin. Crayfish mature in one season and
grow to a length of from four to five inches in three years, so that,
considering the large number of eggs (100-600) laid by one female,
there should be but little difficulty in supplying a large demand for
these animals. When we consider that the large Astacus readily
adapts itself to the slight difference in environment in the east, we
see that the crayfish is a very practicable substitute for the lobster.
There should be no difficulty in disposing of the smaller Cambarus^
either as fresh food or canned, as we get the abdomens of shrimps.

In school and college laboratories, the anatomy of the crayfish
has been studied ever since Huxley wrote " The Crayfish." The
habits and activities of the young and adult crayfish are of great
interest and profit for study. The animal is suited for many kinds
of experiments, and the large ganglia and nerve cells are readily
removed and are excellent for neurological work. Psychologists

lyo ARTHROPOD A

should study the relations of mother and offspring for the few days
just after the young are detached from the mother's swimmerets.

References on the Crayfish and the Lobster

Chidester, F. E. 191 2. The biology of the crayfish. Amer. Nat., vol.

46, pp. 279-293.
Herrick, F. H. 1911(1909). Natural History of the American Lobster.

Bull. Bur. of Fish., vol. 29, pp. 149-408.
Huxley, T. H. 1880. The Crayfish. D. Appleton Co.

Crustacea. (Entomostraca and Malacostraca.) — The Branchio-
poda, Ostracoda, Copepoda, and Cirripedia are certain Subclasses of
primitively developed Crustacea which are grouped under the
heading of Entomostraca as distinguished from the Malacostraca.
They are small in size and while not themselves especially significant
to man, they are of tremendous importance as the food of fishes.

Subclass Branchiopoda. — These Crustacea generally have a shell,
and many pairs of leaflike swimming appendages. The Order
Phyllopoda includes the fairy shrimp and the brine shrimp. The
fairy shrhnp, Branchipus^ a most beautiful form, is found in fresh
water just after the ice has left certain ponds. The brine shrimps
Artemia salina, has been the subject of experimental work on the
influence of reduced and increased salinity on its characteristics.
One species, Artemia jertilis^ is found in the Great Salt Lake.

To the Order Cladocera ^ belong certain species of Daphnia.
This form has a bivalved carapace enclosing the trunk. The eyes
are sessile and fused. The interesting study of phagocytosis made
by Metchnikoff showed that when the spores of a fungus, Mono-
spora, were swallowed by Daphnia^ they perforated the wall of its
alimentary canal, but were attacked and destroyed by the blood
corpuscles. (Figure 75, A and B.) Elton reports a huge multipli-
cation of water fleas in the Antwerp reservoirs in 1896 such that six
men worked night and day removing them by straining the water
through wire gauze. It was estimated that ten tons of water fleas
were taken out.

Subclass Ostracoda. — The common bivalved form Cypris uses
Its antennae in swimming. It has no special economic significance,
except as food for other animals.

' Banta, A. M., and associates, have made numerous important studies on sex
intergrades and the determination of sex in Cladocera. See his recent paper, Control
of sex in Cladocera, Phys. Zool., vol. 2, Jan. 1929.

ARTHROPODA

171

Subclass Copepoda. — These Entomostraca have no shell and
lack abdominal appendages. They are among the most important
fish foods. Forms like Cyclops are the best known. The parasitic
guinea worm (page 96) is transmitted by Cyclops. The Copepoda

Brood chamber
Heart-

Abdom.

Abdominal

Abdo.

Mandible
Anienna

Anal

Hepatic caeca

|— Compound eye
~ Ocellus
^Antennule

Labrum

Fig. 75^^. Female Daphnia pulex, bearing summer eggs.

Studies, vol. 11, 191 5.)

(Dodds, Univ. of Colorado

include many important fish parasites, the form Argulus being
parasitic on the carp. Dr. C. B. Wilson of the U. S. Bureau of
Fisheries is our international authority on parasitic Copepoda.
(Figure 76.) Lake Plankton is rich in the Copepod Diaptomus.

Frontal or nan

Uferus

/
/

' ^Median eye
'^ .-/st. antenna
^Paired eyes

^Znd. antenna

Caudal stylets'

Fig. 755. Branchinecta packardii female showing uterus and eggs. (Dodds, Univ.

of Colorado Studies, vol. 11, 191 5.)

A number of species of Cyclops, colorless and blind, have been
found in wells.

SublcassCirripedia. — The Cirripedia (Figure 77) include the com-
mon ^00 j-^w^-f/^ barnacle, Lepas, and the acorn barnacle, Balanus. The
latter are found along the coast attached to rocks and wharves where

172

ARTHROPODA

Fig. 77. Stalked barnacles {Lepas anatifera).
(From Kellogg & Doane. Courtesy of Henry
Holt & Co.)

Fig. 76. Caligiis mutabilisy dor-
sal view. F.P., frontal plates;
C.A., cephalic area; L.A., lateral
areas; T.A., thoracic area; F.S.,
free thoracic segment;G. 3"., genital
segment; A., abdomen; E.S., egg
strings. (Courtesy of C. B.
Wilson.)

Fig. 78. Sacculina, a crustacean parasite of
crabs, {a) Attached to a crab, with root-like
processes penetrating the crab's body; {b) re-
moved from the crab. (From Jordan and
Kellogg, Animal Life. Courtesy of D. Appleton
&Co.)

ARTHROPOD A 173

their sharp shells are sources of much annoyance to bathers. Bar-
nacles encrust the bottoms of ships. ^ Huxley described the barnacle
as a " crustacean fixed by its head and kicking food into its mouth
with its legs." One of the Cin-ipedia, a parasitic form known as
Sacculina, is considered to be the most degenerate of parasites.
(Figure 78.) It attacks the abdomen of crabs and causes degenera-
tion of the gonads. Barnacles are degenerate crustaceans.^ The
animals have lost their independence by attachment of the head or
back, and the readjustment of segmental plates to suit the new
needs. Embryology of the barnacles shows that they probably
arose from free swimming phyllopods. Ruedemann discovered a
primitive Balanus attached to the shell of a Cephalopod in the
Ordovician shale, which also bears out this hypothesis. The goose-
barnacles {Lepas) became fixed by the head, and developed several
valves.

Subclass Malacostraca. — The Malacostraca are usually large
Crustacea, with five cephalic, eight thoracic and six abdominal
segments, and with a grinding " gastric mill " in the stomach.
The Malacostraca include lobsters, crabs, prawns, shrimps and pill
bugs. The orders which we shall consider are the Amphipoda, the
Isopoda and the Decapoda. The Amphipoda lack a carapace and
have an elongated abdomen with three pairs of posteriorly directed
feet, and three pairs of anteriorly directed swimming feet.

The beach fleas ^ Amphipoda^ found on sea beaches, are important
food for other marine animals. A boring amphipod, Chelura,
attacks piles and wooden ships. The Isopoda have no carapace, a
broad flat body, leaflike legs, and seven free thoracic segments.
The wood-lice or sow bugs are Isopoda which live a wholly terrestrial
life. They feed on decaying vegetable matter but sometimes
damage plants in gardens and greenhouses. As they breathe by
abdominal gills, they seek moist places. Some of their relatives
live in fresh and salt water.'*

^ Visscher, J. P. 1927. Nature and Extent of Fouling of Ships' Bottoms. Bull.
U. S. Bur. Fish., vol. 43, 1927, Doc. 1031. Visscher found that paint of lighter colors
should be used to prevent fouling of ships' bottoms while they are in port. Barnacles
are stimulated most by light in the field of green and blue.

^ Clarke, J. M. 1921. Organic Dependence and Disease. N. Y. State Museum.

* Allee, W. C, who for over fifteen years has been studying animal aggregations in
Isopoda and other forms, has recently given an excellent summary, Animal aggrega-
tions, Qu. Rev. of Biol., 1927, vol. 1, no. 3, pp. 367-398. Consult also his book, Animal
Aggregations, U. of Chi, Press, 1931.

174

ARTHROPODA

An important genus, Lunnoria^ is found attacking submerged
wood, sometimes honeycombing piles more than half an inch. Piles
are accordingly creosoted or infiltrated with paraffin. (Figure 79.)

The order Decapoda includes our common crabs, shrimps and
lobsters. The first three pairs of thoracic appendages are modified
as maxillipeds, the thoracic segments are covered by a carapace
and there are five pairs of thoracic walking legs. The compound
eyes are stalked.

Fig. 79. Limnoria. (Courtesy of C. A. Kofoid.)

There are two distinct genera oi crayfishes in America, Cambarus,
found east of the Rocky Mountains, and Astacus extending to the
Pacific coast. The latter genus includes individuals that grow to
a length of 9 inches. The largest crayfish in the world, Astacopsis
franklinii, found on the northwest coast of Tasmania, may weigh
as much as 9 lbs.

The American lobster, Homarus americanus, the European lob-
ster, H. grammarus, and the Norwegian lobster, Nephrops nor-
wegicus, are extremely important as food of fishermen and when
served as delicacies inland. The lobster is found along the Atlantic
coast, ranging from North Carolina to Labrador. The largest
lobster ever taken weighed 34 lbs. and was 23.75 if^ches in length
(Herrick).

ARTHROPODA 175

The sea crayfishes, Palinurus vulgaris, sometimes called the spiny
or " rock lobsters," have no chelae and a much reduced rostrum.
They are valued by Europeans for food and are said to be similar to
the true lobster in flavor. The common prawn, Palaemonetes
vulgaris, reaches a length of about 1 inches. It is transparent.
The body is compressed and the exoskeleton lacks lime. The ros-
trum, eye stalks and antennae are very conspicuous. The common
shrimp, Crangon (Crago) vulgaris, is exceedingly abundant on the
Pacific coast, along the shore of the Gulf of Mexico, The edible
shrimp, Penaeus setijerus is found in shallow bays and estuaries
from Virginia to Texas. It reaches a length of 6 inches. Its value
as food is estimated to be over ^200,000 annually. While speaking
of shrimps, we might mention the order Stomatopoda which includes
Malacostraca with five pairs of anterior thoracic maxillipeds, three
pairs of thoracic legs and an extremely short carapace. The
mantis shrimp, Squilla {Chloridella) empusa, belonging to this order,
reaches a length of 10 inches. Several species of Squilla are eaten
in the Mediterranean and tropical Pacific. They are esteemed as
a delicacy in Tahiti and Samoa. Perhaps the American form may
yet come into use.

The hermit crabs, Eupagurus, related to the shrimps and prawns,
live in the shells of gastropods which they seek out very early in their
life history and in which they are protected. Sea-anemones and
hydroids are commonly found attached to the shells occupied by
hermit crabs. (See Commensalism, p. 482.) Robber crabs {Birgus
latro) are related land forms found on coral islands in the Indian
Ocean, They ascend cocoanut trees, and feed on the pulp of the
cocoanut. The blue crab {Callinectes hastatus) is the commercial
soft-shell crab. Rock crabs and painted crabs are also used for food
when soft. Oyster crabs bring a high price in the market. The
ghost crab, a scavenger, destroys the eggs of sea birds. (Figure 80.)
A little marina crab, Melia, inhabiting coral reefs, uses small sea-
anemones for defense and for feeding. It captures an anemone
in each claw and when attacked it thrusts the anemone towards
the enemy for defense. When the anemones capture food, the crab
seizes the tidbit.

Class 2. Onychophora. — The Onychophora (Gr. onux, a claw;
phoreo, bear) include approximately fifty species of the genus
Peripatus, found in Australia, New Zealand, Africa, South America,
and the West Indies. All the species of Peripatus are terrestrial,

176

ARTHROPODA

living in damp places. About thirty species live In the tropics,
eight appearing in Africa. Peripatus lives in crevices in rocks and
other dark sheltered places, and moves slowly, avoiding strong light.
It ejects slime from a pair of oral glands, capturing insects and
Crustacea. Much as it resembles the hypothetical " ancestral
Arthropod " of some zoologists, Peripatus is not ancestral, but merely

Fig. 80. Above, male spider crab. Left, female spider crab. Right, ghost crab.
Center, mud crab. (From Mayer, Seashore Life. Courtesy of N. Y. Zool. Soc.)

a primitive type, modified from an old stock. When first discovered,
it was termed a slug. Although it is an Arthropod, we find that
Peripatus has a number of characteristics of the Annelida, such as
paired segmental nephridia, and ciliated cells in the lining of the
reproductive tubes. Like the Arthropoda, its appendages are
modified as jaws, and it has well-developed tracheae, but lacks a
coelom around the alimentary canal. (Figure 81.)

ARTHROPODA

177

Class 3. Myriapoda. — The Myriafoda (Gr. murics^ ten thou-
sand; podes, feet) have a head with paired antennae and mandibles,
many similar body segments bearing leglike appendages, tracheae,
and excretory (Malpighian) tubules which open into the intestine.
The Millipeds are wormlike in appearance with about three hundred
segments, to each of which is attached two pairs of appendages.

Fig. 8 1 . Peripatus. (From Pearse, General Zoology. Courtesy of Henry Holt & Co.)

Very few of them are injurious to agriculture. Julus is a crop
destroyer. Centipedes have but one pair of appendages for each
segment. The large tropical centipedes {Scolopendra) are reported
to be extremely venomous and their bite may even be fatal to man.
They reach a length of eighteen inches, are carnivorous and able to
kill insects almost instantly. South American Indians use them as
food. The house centipede {Scutigera forceps) feeds on flies, cock-
roaches, and bed-bugs and since it is not very poisonous to man, is
of considerable economic importance.

Class 4. Hexapoda. (Insecta.) (Gr. hex., six; ?Ln6.pous, foot.)
— We live in the Age of Insects, and struggle with them for the
possession of the earth. Not only physical and chemical agencies,
but all available natural enemies must be utilized in order to keep
the insects under control. They devour our foodstuffs, destroy our
animal friends and still prevent us from claiming important new
territory. The number of species of insects outnumbers those of
all other animals taken together, and the number of individuals is
incalculable. Little is known about the histology, embryology or
physiology of insects, but all that we do know has shown that they
are of tremendous importance economically. Interesting studies
of their habits have shown that insects are highly developed and
specialized in their behavior.

The Insecta have three well-defined regions, the head, thorax and

Wings membranous

Fore wings parchment-like.

178 ARTHROPODA

abdomen. All insects have three pairs of thoracic legs and the
majority have one or two pairs of thoracic wings. Respiration is
accomplished by means of a complicated tracheal system. Insect
classification is based on the structure of the mouth parts and the
character of the development. Aldrich reported (1907) that there
were 640,000 named insect species.

Classification ^

Metamorphosis very slight; biting mouth parts; wingless Thysanura.

Metamorphosis incomplete.

With biting mouth parts.

Ephemerida.

Plecoptera.

Odonata.

Isoptera.

Corrodentia.

fOrthoptera.

Euplexoptera.

Wingless Mallophaga.

\nT II- 1 J Hemiptera.

W ith suckmg mouth parts < „, ^

"^ ^ 1 hysanoptera.

Metamorphosis complete.

With biting mouth parts.

Neuroptera.

With wings membranous s Mecoptera.

Trichoptera.

With fore wings thickened Coleoptera.

H7- LI- 1 J Lepidoptera.

With suckmg mouth parts S t^-

^ ^ IDiptera.

With lapping or piercing and sucking mouth parts < „

Folsom (1922) gives a most elaborate classification of insects
according to food habits: Microphaga, feeders on sugars and salts,
with yeasts and bacteria; sarcophaga, flesh eaters; copraphaga,
eaters of molds and bacteria; mycetophaga, consumers of fungi;
necrophaga, eaters of dead animals, etc. (A flesh-eating insect
larva may eat 200 times its own weight in 24 hours.) In America
it is customary to classify the insects into 19 orders. We will
consider them thus, treating briefly of each order.

Insects. Order 1. Thysanura. {Aptera). — T\vt Thysanura \n-
clude wingless insects with retracted mouth parts and no meta-

^ Classification after Kellogg and Doane.

ARTHROPODA

179

morphosis. The common ''fish moth " or stive}' fish attacks starched
clothing, book bindings and wall paper paste, and the " snow flea "
sometimes gets into maple sap.

Order 2. Ephemerida. — The May-flies have delicate wings,
poorly developed mouth parts and an incomplete metamorphosis.
The young May-fly lives in the water. Adult May-flies are said to
take no food, but to mate, deposit their eggs and die, all within the
short span of twenty-four hours. (Figure 82.)

«rt

Fig. 82. Young nymph of May-fly, showing tracheal gills. (After Jenkins and
Kellogg, from Kellogg and Doane, Zoology and Entomology. Courtesy of Henry Holt
& Co.)

Order 3. Odonata. — The dragon flies, as larvae and as adults,
are important enemies of mosquitoes. They have large compound
eyes, four membranous wings and strong, biting mouth parts.

Order 4. Plecoptera. — The stone flies are less important as fish
food. The nymphs live in running water where they cling under
stones.

Order 5. Isoptera. — The termites or " white ants " are found in
the tropics in great abundance, where they destroy houses and other
structures made of wood. Some species attack soft plants and living
trees. In Africa, they sometimes build pyramidal nests twenty feet
high. The termites are social insects. (See p. 484.)

Order 6. Corrodentia. — The book-lice are wingless insects
frequently found defacing the paper and bindings of old books.
Bark lice are winged forms feeding on lichens, oak leaves and other
foliage.

Order 7. Mallophaga. — There are about fifteen hundred species
of biting lice which live among the feathers of birds or the hair of
mammals. While they are not sucking forms, they cause bleeding
and the results are almost as bad. They irritate the animals which
resort to dust baths.

i8o ARTHROPODA

Order 8. Thysanoptera. — The thrips are minor pests of wheat,
onions, citrus fruits and grasses. Their feet are clawless with blad-
ders adapted for clinging to leaves. They have four narrow mem-
branous wings, fringed with long hairs.

Order 9. Euplexoptera. — The earwigs feed on fruit and flowers,
but are of no economic significance in America, where they are
rare. The mother remains to guard her eggs for a time.

Order 10. Orthoptera. — The cockroaches, Blattidae, are noc-
turnal insects frequenting water pipes and attacking food stuffs.
There are four species in the U. S., the common " croton bug " being
the form most frequently found. They eat the " silver-fish," bed-
bugs and each other.

The praying mantis, Mantidae, has its front legs peculiarly
adapted for seizing and holding its prey. Its peculiar attitude when
lying in wait for its food gives it the name " praying."

The walking sticks, Phasmidae, resemble their background so
perfectly that it is exceedingly difficult to locate them at times.
They feed on the leaves of trees, usually the oak.

Locusts or short-horned grasshoppers, Acrididae, have extremely
short antennae and well-developed leaping legs. They are impor-
tant enemies of plant life and, when they migrate in hordes, seem to
devour almost everything. Locusts were eaten in the Orient and
are still prized by some savages. (Figure 83.)

The Tettigoniidae {Locustidae) include the meadow grasshoppers
and the katydids. The katydids are large green insects feeding on
leaves and tender shoots, but occasionally devouring other insects.
'Y\\t females are silent. Certain yellowish brown, wingless forms,
living in cellars and caves, are called " cave crickets."

The Gryllidae have their wings flat on the body and are usually
stout-bodied. Many are wingless. The true crickets (house
crickets) are black forms, feeding on plants for the most part.
The eggs are laid in the ground in the fall and hatch in the summer.
The tree crickets are slender and light in color. The " snowy tree
cricket " injures grape vines and berry plants. The female guards
her eggs. The mole cricket has its front tibiae broadened for bur-
rowing. It is an important enemy of growing plants, particularly
the potato.

Type of the Order — Lubber Grasshopper — Rhomaleum Microp-
ierum. Anatomy. — The grasshopper is divided into three distinct
regions: The head, the thorax with three segments, and the abdo-

ARTHROPODA

i8i

men consisting of eleven segments. The head is rather elongated
dorsiventrally and bears two rather large laterally situated com-
pound eyes with many facets. There are three simple eyes, the
ocelli, one near the middle of the forehead and the others situated
near the bases of the antennae. The antennae are long and seg-
mented to give flexibility. They bear many spines which furnish
increased points of contact. The mouth parts consist of a dorsally
situated labrum; two crushing mandibles with serrated edges; a
pair of maxillae, each provided with a maxillary palp; and a ventral
labium with a pair of labial palps.

antennae

•ovipositor

fern uri
tibia''

tarsal segments

Fig. 83. Locust, with external parts named. (From Kellogg, The Animals and Man.

Courtesy of Henry Holt & Co.)

The thorax consists of three segments, prothorax, mesothorax and
metathorax, with a pair of legs attached to each of the segments.
The third and second thoracic segments bear wings in the grass-
hoppers. The anterior pair of wings are wing covers and used for
gliding, while the posterior pair, folded like a fan when at rest, are
the true flying wings.

The abdomen consists of eleven segments. In the male there are
nine distinct movable sterna. The posterior end in the female is
modified by hardened ovipositors, the tips of which are protruded
beyond the eleventh tergum. During oviposition, the tips are

l82

ARTHROPODA

ARTHROPODA 183

forced into the ground, then separated, forming a pit for the reception
of the eggs.

The Digestive System. — From the anterior mouth a short rather
broad esophagus (Fig. 84) extends dorsally and posteriorly into the
thorax, where it enlarges to form a thick-walled a-op or ingluvies,
which extends through the mesothoracic and metathoracic segments.

On each side of the anterior end of the crop are delicate branched
salivary glands which communicate by means of salivary ducts with
the mouth cavity. The proventriculus is not constricted from the
crop, but extends a short distance to the stomach. The stomach
or ventriculus extends to the seventh abdominal segment. At the
point where the ventriculus originates, there are eight cylindrical
pouches, the gastric cecat, extending anteriorly on the sides of the
proventriculus and continuing as eight diverticula or c&c?if^ posteriorly
along the sides of the ventriculus. No liver is present. The ileum^
or intestine which has noticeably hardened walls, is found in the
seventh, eighth and ninth abdominal segments, constricting poste-
riorly as it enters the colon or hind intestine, which runs dorsally
down the ninth and tenth segments. The rectum is a small white
enlargement situated in the dorsal portions of the ninth and tenth
segments and emptying at the anus on the lower surface of the
eleventh tergum.

Respiratory System. — In the grasshopper there are two pairs of
thoracic stigmata or spiracles. Eight pairs of abdominal spiracles
are situated laterally just above the pleurons, the most conspicuous
being the pair found on the anterior margins of the tympani. Ex-
tending throughout the body, we find a well-developed system of
tracheal tubes, which take the place of the complicated circulatory
system found in some other invertebrates, but lacking in the Arthro-
poda.

Circulatory System. — The heart is a long, narrow vessel, extend-
ing in the dorsal portion of the abdomen. It is divided by valves
into chambers, the anterior one being called the aorta. There are
no arteries or veins, but the blood passes through sinuses and finally
enters the heart through lateral ostia. (Many of the strongest
cardiac poisons have no action whatever on the insects.)

Urinary System. — The Malpighian tubules are masses of fine
tubes, anterior to the rectum, and open into the intestine. They
are primitive kidneys.

Reproductive System. — The ovaries consist of a long white struc-

1 84 ARTHROPOD A

ture above the ventriculus and intestine made up of two sets of tubes
bound together into a compact mass. Two delicate oviducts pass
posteriorly around the ileum and colon to the ventral portion of the
body where they unite to form the single median vagina which opens
on the upper surface of the subgenital plate at the ovipositor. The
spermatheca is a small white pouch situated above the posterior end
of the vagina and communicating with it at the bursa copulatrix
by means of a minute orifice. The testes consist of two sets of
coiled tubules bound together in one mass and situated above the
intestine. Each testis sends off a vas deferens, the two uniting to
form a median ejaculatory duct. To each vas deferens is attached a
seminal vesicle, while cement glands empty into the ejaculatory duct.

The Nervous System consists of dorsally situated cerebral ganglia,
two circum-esophageal connectives, a pair o{ fused sub-esophageal,
three pairs of fused thoracic, and five pairs of fused abdoyninal
ganglia. The thoracic ganglia are much larger than those of the
abdomen. Such highly developed concentration of ganglia in
cephalic and thoracic regions indicates a very high development of
reactions. In the ants and bees we find even greater concentration.

Order 11. Hemiptera. — The Hejniptera have sucking mouth
parts and when wings are present, they have four. Most of the
Hemiptera are winged. Some generations of aphids are wingless.

The Heteroptera, true bugs, include aquatic and land forms.
The giant water bugs (Belostomatidae) are important enemies of
insects, tadpoles and small fishes. The harlequin cabbage bug is an
important pest in the South, while the gj-een soldier bug and the
spined soldier bug are predaceous, destroying the larvae of injurious
Hexapoda. The squash bugs {Coreidae) and allied forms attack
squashes, pumpkins and other garden vegetables. The assassin
bugs {Reduviidae) are predaceous forms attacking other insects
such as the bed-bug. They may even attack man. The Indian
bed-bug {Cimex hemipterus) and the common bed-bug {Cimex lec-
tularius) transmit dum-dum fever, a flagellate disease. (See p. 29.)
The chinch-bug is one of the worst pests of corn known and also
attacks wheat. The leaf bugs attack foliage.

The most important of the Homoptera are the scale insects and
the plant lice. The cicadas {Cicadidae) include a form known as the
seventeen-year " locust," which lives underground as a nymph from
thirteen to seventeen years. The eggs are laid in living twigs.
They hatch in about six weeks, burrow into the ground and feed on

ARTHROPOD A 185

the juices of roots until the seventeenth year, when they emerge,
moult and become adults.

The plant lice or aphids {Aphididae) Include our most destructive
greenhouse and orchard pests. The grape phylloxeran {Phylloxera
vastatrix) causes decay of the roots of grapevines. Aphids undergo
parthenogenetic development. (See p. 123.)

The scale insects, especially the San Jose scale, are extremely
injurious to fruits. The cottony-cushion-scale, which attacks the
orange groves of California, was successfully controlled by the lady
beetle ( Novius cardittalis) Imported from Australia.

Several families of plant hoppers occur. These Include the
spittle Insects, the lantern flies, some of which are luminescent, the
leaf hoppers and the tree hoppers. The leaf hoppers are injurious
and difficult to control.

Certain Hemiptera, known as the Parasitica {Anoplura), are
wingless and constitute formidable enemies of man and other mam-
mals. The species that Infest man (Genus — Pediculus) Include the
head louse, the body louse and the crab louse. Domestic animals are
infested by the genus Haematopinus.

Order 12. Neuroptera. — A number of orders were formerly
grouped under the Neuroptera, but are now separated. The order
Neuroptera includes some very large Insects. They have four long
narrow and finely netted wings. Their metamorphosis is complete
and they have biting mouth parts. Their antennae are conspicuous.

Larvae of the dobsonfly, known as " helgrammltes," are used for
fish bait. The a7it lions, or " doodle-bugs," make pits in sand, dust
or decayed wood, capturing thus many small insects. The adult
ant lion resembles a damsel fly.

The lace-winged flies or " aphis lions" have thin lacy wings and
are green in color. Their larvae resemble those of the ant lions
but have yellow or red markings. They feed on colonies of plant
lice. The adults have brilliant golden eyes.

Order 13. Mecoptera. — The scorpion flies have four membra-
nous wings, thickly veined but with few cross-veins. The head is
beaked and the mouth parts are adapted for biting. Metamorphosis
Is complete. Scorpion flies feed on small insects. Both the larvae
and the adults are carnivorous.

Order 14. Trichoptera.—The caddice flies have rudimentary
mouth parts, four membranous wings thinly clothed with hairs, and
have complete metamorphosis. The aquatic larvae lack pro-legs

1 86 ARTHROPODA

and form cocoons of sand, pebbles and silk, which are easily recog-
nized as those of the " caddice-worm."

Order 15. Lepidoptera. — Lepidoptera have four wings covered
with fine, powdery scales. The larvae of moths and butterflies,

called caterpillars, are
worm-like, having three
pairs of true thoracic legs
and from one to five pairs
of pro-legs.

„ . ^. ., . Micro - Lepidoptera in-

FiG. 85. Case or Discosmoecus gilvtpes. , , , ^ ...

(Dodds, G. S., and Hisaw, F. L., Ecology, ^^^^^ /^e super-families
vol. 6, no. 2.) Pyralidina, Tortricina and

Tineina.

The Pyralidina or " leaf-rollers " feed on stored grain. The
European corn borer {Pyrausta nubilalis), an important pest in this
country, appears to accumulate in destructive numbers in areas of
naturally high soil and atmospheric moisture. Meal moth {Pyralis
farinalis) larvae feed on meal and flour, making tubes of silk in the
77teal. The Mediterranean flour moth {Ephestia kushniella) is one of
the most injurious forms, infesting flour mills. Other injurious
forms are the meal-moth, the clover-hay worm, the melon-worm and
the pickle-worm. The Tineina^ smallest of the Lepidoptera, include
the grain moths and the clothes moths. Grain moths attack grains
both in the field and stored. The common clothes moths are yellowish
moths whose larvae do a great deal of damage to woolen clothing
and furs. (Figure 86, A and 5.)

The family Tortricina includes the bud moth which attacks young
shoots of apple trees, the strawberry leaf roller and the extremely
injurious codling moth. The codling moth causes an annual loss of
over ^12,000,000. The larvae burrow through the blossom end of
an apple and eat their way to the core, devouring the seeds. The
larvae of the second generation usually feed on the surface of the
apple. In the fall the larvae burrow into crevices of the bark, spin
white silk cocoons and hibernate. The Oriental fruit worm was
introduced on the ornamental cherry trees sent from Japan to
decorate the city of Washington, It attacks twigs and young
peaches. The Noctuidae are the largest family in the order, with
more destructive forms than any other. The army worms migrate
from field to field in large bodies. The corn ear worm or cotton-boll
worm, the cotton worm^ and the cabbage looper are a few of the more

ARTHROPOD A 187

important pests. The cotton-boll worm and the cotton worm cause
millions of dollars loss annually to the cotton growers. The
Bombycidae include the coinmon silk-worm moth. The silk worm has
been artificially bred in China for over five thousand years.

Some of the largest and most showy of the moths belong to the
giant silk worm family, the Saturniidae. These include the Poly-
phemus, the Cecropia, and the Luna moths. The Cecropias are a
trifle injurious to shade trees, but in general these species are
interesting only on account of their size. The carpenter moths
(Cossidae) are wood-borers attacking trees.

A B

Fig. 86. yf, clothes moth. 5, larva of clothes moth. (After Riley. U. S. Dept. Agr.)

The Geometridae are called " measuring worms " when in the
larval state. An extremely important species is the spring canker
worm (Paleacrita vernata) whose larvae feed on the leaves of fruit
trees. The Liparidae or tussock moths injure shade trees. The
white marked tussock moth is a native form injurious to fruit and
shade trees, while the antique or rusty tussock moth is a European
species found in Nova Scotia, New England and the West. The
brown tail moth attacks shade and forest trees, but avoids the
conifers. The gypsy moth has spread from the New England states
into some of the Middle Atlantic states. The Sphingidae include
the hawk moths or humming bird moths. They have long tongues
adapted for sucking nectar from flowers like honeysuckles. The
butterflies have their antennae enlarged at the tips, and fly exclu-
sively in the daytime^ while moths fly at night and have threadlike
or feathery antennae. There are two great super-families, the
Papilionina or true butterflies and the Hesperina or skippers.

The Nymphalidae include forms with poorly developed front
legs, not adapted to walking. Some of the more common forms are
the thistle butterfly, the Admiral, the wood nymph and the viceroy.
The viceroy is interesting because it closely resembles the bad tasting

1 88 ARTHROPODA

monarch butterfly and is supposed to be thus protected. (Natural
Selection, p. 515.) The swallow-tailed butterflies (Papilionidae)
include the black swallow tail whose larvae feed on celery and parsley;
and the tiger swallow tail^ yellow in color, which is the largest common
species. Caterpillars of the cabbage butterflies devour the outer
leaves, then bore to the heart of the cabbage.

The alfalfa caterpillar {Ewymus) attacks alfalfa in the West.
The gossamer winged butterflies {Lycaenidae) are the smallest and
most delicate butterflies. The larvae are small and slug-like and
feed on plants. One carnivorous form, the " harvester," is valuable
to the fruit-grower since its larva feeds on the wooly aphids.

Pigment in Butterfly Wings. — One of the present day fads is that
of enclosing butterfly wings in glass brooches. The natural color
should remain for some time since colors in the wings of fossil but-
terflies were found persistent when exhumed by Dr. R. J. Tillyard
millions of years after they were sealed with mud. Exposure to the
air caused rapid fading, however.

Order 16. Diptera. {Flies, Mosquitos, etc.) — The Diptera, as
the name indicates, have two wings. They have sucking mouth
parts, and the metamorphosis is complete. There are over 7,000
species of Diptera in North America.

The common housefly {Musca domesticd) carries typhoid, tubercu-
losis and other bacterial diseases. It is also important in the
transmission of the eggs of several species of Nematode and Cestode
worms. A fly wing is said to vibrate 330 times per second. House-
flies lap up liquid food with their folding proboscis.

The blow fly and th.& flesh fly {Sarcophagidae) deposit their eggs
on meat and cheese on which the maggots feed. The horse fly
{Tabanidae) attacks cattle and horses and even man. The female
feeds on blood, but the male lives on nectar. The tachina fly
{Tachinidae) is an important enemy of caterpillars (particularly
the army worm), and kills many locusts and leaf-eating beetles.

The bot-flies {Oestridae) attack cattle and horses. The eggs of
the horse bot-fly, licked off their legs by infested animals, develop
in the lining of the stomach until the time of pupation when they
are extruded.

The ox-warble larvae ( Hypoderma lineata) pass to the esophagus
of the host in the same manner as those of the horse bot-fly, but
then burrow into the subcutaneous tissue and lodge just under the

ARTHROPOD A 189

skin where they cause lumps. Ultimately they develop and pass
out through the hide, riddling it with holes. Herms cites a case of
the ox warble in a child in which the grub, Hypoderma lineata^
travelled from below the knee to a point behind the ear, taking
about two months' time.

The sheep-bot flies, living in the nostrils of sheep and antelopes,
travel up the frontal sinus and cause the disease known as " stag-
gers." Other bot-flies attack rodents and even man. One form,
Dermatobia hominis, found in Mexico, Central, and South America,
attacks Birds, Mammals and Man. It is transported by certain
mosquitoes, particularly Psorophora lutzi. The larval period re-
quires about three months.

Mosquitoes {Culicidae) ^ have slender sharp-pointed mandibles,
enabling them to puncture the skin of animals. Mosquitoes are
extremely important in the transmission of parasites causing disease.
They include three important groups: Anopheles, Aedes, and Culex.
(Figure 87.)

In the Anopheliites, the head has upright forked scales and the
palpi in both sexes are almost as long as the proboscis. Anopheles
larvae lack a siphon tube and breathe through a stigmatic opening
on the eighth abdominal segment. They rest at the surface
of the water. In resting, as in the position of biting, the Anoph-
eles adult elevates its body in a characteristic manner (Figure 88).
Anopheles quadrimaculatus and several allied species transmit
malaria. Bird malaria is transmitted by the Culicine mosquitoes
{Culex pipieyts).

In Aedes {Stegomyia) (Figure 89), the head has a few forked
scales and a mass of flat scales covering the head while the palpi
are less than one-half as long as the proboscis. Aedes larvae have a
short, conical siphon tube, and hang down from the surface of the
water. The successful completion of the Panama Canal was ac-
complished only after measures were taken to kill the yellow fever
transmitting mosquito, Aedes egyptii {Stegomyia calopus).

In the Culicines, the head has a few flat scales, but many narrow
curved and upright forked scales. The palpi of the male are nearly

1 Varro, the Roman author, cautions the builder against placing his farm-house
on swampy ground " because certain minute animals, invisible to the eye, breed there,
and, borne by the air, reach the inside of the body by way of the mouth and nose and
cause diseases which are difficult to get rid of." Centuries later mosquitoes were
proved to be the carriers of malaria and yellow fever.

190

ARTHROPODA

Anopheles. Female Anopheles, Male Culex, Female Culex

A

Fig. 87. A, structural characteristics of antennae of Culex and Anopheles. B,
resting position of Culex mosquito (above), and Anopheles mosquito. (Courtesy of
Major George C. Dunham, and U. S. Army Medical Field Service School.)

ARTHROPODA

191

as long as the proboscis, while those of the female are less than one-
half as long. Culex larvae have a slender, long siphon, and hang
down from the surface of the water. The adults in resting position
do not elevate the abdomen as in the Anophelines. Filariasis, the
disease known as elephantiasis, which is caused by a small nematode,

Fig. 88. Larvae of Anopheles, above, and Culex, below, in feeding and breathing
position. (From Howard, Mosquitoes oj the U. S.)

Microfilaria bancrofti, is transmitted through the agency of a Culi-
cine mosquito, Culex {fatigans) quinquefasciatus. Dengue, or
breakbone fever, is a tropical disease, found in Mexico, which is
transmitted by both Culex fatigans and Stegornyia calopus.

Poison. — The poison of female mosquitoes has not been thor-
oughly studied, but Noguchi reports that there are three sets of
glands, two of which are ordinary salivary glands, and the third set,

192

ARTHROPODA

Fig. 89. Yellow-fever mosquito, Stegomyia fas-
ciata. (Howard, F. B., 1354, U. S. D. A.)

situated between the
other two, secretes the
poison. If a mosquito
punctures the skin, but
does not reach blood,
the poison is not injected.
An anticoagulant is pro-
duced by the mosquito.

The gall gnats {Ceci-
dofnyiidae) are terrestrial
forms attacking many-
plants and producing
" galls." The Hessian-
fly, a small black form,
is estimated to damage
wheat and rye to the ex-
tent of many millions of
dollars annually. The
crane flies ( Tipulidae)
somewhat resemble mo-
squitoes. They are often
quite large, with long,
loosely attached legs.

Fig. 90. Male and female fruit flies {Drosophila melanogaster) . (Morgan, Physical
Basis of Heredity. Courtesy of J. B. Lippincott Co.)

ARTHROPODA 193

Their larvae live in the soil and injure the roots of plants. The
midges {Chironomidae) are small flies somewhat resembling mo-
squitoes. In the larval state they are red, wormlike, aquatic forms.
The black flies {Simuliidae) are aquatic in the larval state, and the
adults are great pests in some localities since they are blood suckers
and attack fishermen.

T\\& fruit flies, particularly the Drosophilidae (Fig. 90), are used
in investigations on heredity. (See p. 538.) There are about
1,000 species of Trypaneidae attacking various fruits. The Mediter-
ranean fruit fly ^ {Ceratitis capitata), known for over 100 years, and
of considerable importance in the Mediterranean countries and
more recently in Hawaii, was discovered in Florida on April 6, 1929.
Its life cycle takes from 30 to 40 days, pupation occurring in the
ground. In Hawaii and in South Africa, Ceratitis capitata has
proven a serious pest of the citrus fruits, but also attacks deciduous
fruits such as peaches and apricots. Lemons are practically im-
mune to this pest, but sour oranges are more susceptible than the
sweet varieties. In Hawaii, poison sprays have not been used with
any degree of success, but they
appear to be more effective in
the U. S.

The Syrphus flies {Syrphi-
dae) are important enemies of
the aphids and feed on nectar
and pollen. Some are scaven- p^^ ^^ ^ "rat-tailed" larva (Syr-
gers, the " rat-tailed " larvae phidae). (Smith, Insects of New Jersey,
feeding on foul organic matter. N.J. Board of Agr.)
(Figure 91.)

Some of the species " mimic " the bees and wasps. According
to the ancient Bugonia myth, bees develop in the carcasses of dead
animals, but the drone-flies {Eristalis tenax) are the forms thus
found. The reactions of the drone-fly to light have been extensively
studied by Dolley.^

8 In climates where the mean temperature fails below 50° F. over periods covering
3 months, there is little development of Ceratitis capitata and accordingly it is hoped
that we can limit its ravages to the Southern states. (Herrick, G. W. The procession
of foreign insect pests. Sc. Mon., vol. 29, pp. 269-274.)

'W. L. Dolley, Jr., and J. L. Wierda. 1929. Relative sensitivity to light in
different parts of the compound eye in Eristalis tenax. Jour. Exp. Zool., vol. 43, pp.
129-139, May.

194

ARTHROPODA

The sheep tick, the horse tick and various bird ticks belong to
the sub-order Pupipara.

Order 17. Siphonaptera. (Fleas.) — The Siphonaptera, or fleas,
are wingless, with sucking mouth parts and complete metamorpho-
sis. There are about 50 species in the United States. The common
cat and dog flea, Ctenocephalus canis, attacks man. The human
flea (Pulex irritans) and the chigoe or " chigger " {Sarcopsylla pene-
trans) are important enemies of man, the latter burrowing into the
skin. This is not the common chigger, which is a mite. (See page
201.)

The rat flea {Laemopsylla cheopus) transmits bubonic plague from
rats and ground squirrels to man. Fleas may start out with one
animal as a host and transfer to its enemy.

Order 18. Coleoptera. (Beetles.) — The beetles have four
wings, well-developed biting mouth parts, and a complete meta-
morphosis. There are over 12,000 species found in America, ex-
clusive of Mexico.

The tiger beetles (Cicindelidae), both in the larval and adult
states, are important enemies of insects and crustaceans. The
larvae live in holes in the ground. The ground beetles (Carabidae)
are extremely important predaceous insects. They destroy the
larvae and adults of many injurious leaf-eating insects. The cater-
pillar hunter (Calosoma scrutator) is an important enemy of the
hairy " tent-caterpillar." Other forms attack cut-worms and
canker worms. A few species feed on young grains, but the majority
of the Carabidae are beneficial. The carnivorous water beetles
(Dytiscidae), a.re important enemies of mosquitoes and other injurious
insects. The larva, the ferocious " water-tiger " traps air under the
hairs of its tergum and is able to remain under water for some time.
Large " tigers " reach a length of three inches. The water scavengers
(Hydrophilidae) are large forms living under the surface of water
during the day, but flying to lights at night. They are black and
over an inch in length. The whirligig beetles (Gyrinidae) are small
aquatic forms not more than ^ of an inch long. Children some-
times call them " money-bugs." The lady bugs (Coccinellidae) or
" lady-bird beetles " are predaceous in the larval as well as the
adult condition. They are important agents in the control of plant
lice and scale insects. The genus Epilachne is herbivorous.

The carpet beetle (Anthrenus scrophulariae) attacks rugs and
clothing, including feathers. The club-horned beetles (Clavicornia)

ARTHROPODA 195

may be found on land and in the water. Some are herbivorous and
exceedingly injurious. The Dermestidae destroy stored grains.
The saw-toothed grain beetle {Cucujidae) is an extremely injurious
species.

The buffalo-moth attacks wool, feathers and furs, while the
larder beetle destroys and spoils animal food products. The
Elateridae, or click-beetles, are interesting as adults, but their larvae,
called wire-worms, attack plants and seeds. Certain of the wood
borers {Buprestidae) are distinguished as the flat-headed borers.

T\iQ fireflies or Latnpyridae are luminous insects flying at night.
Many non-luminous forms belong to the same family. The blade
horned beetles or LaiJiellicornia have antennae with their terminal
joints developed into leaflike plates forming a club. There are two
families, the Lucanidae or stag-beetles, and the Scarabaeidae. One of
the most familiar forms is the stag-beetle, with its long mandibles
or " antlers." Some males have well-developed mandibles and are
tailed " pinching bugs." The Scarabaeidae include the most of the
Lamellicorns. The leaf chafers feed on flowers and leaves. The
scavenger beetles bury or eat decaying matter. The sacred beetle
or Scarab, found in Egyptian tombs, is a species of dung-feeding
tumble bug. Egyptians worshipped the scarab because it killed
worms. Other forms notably injurious are the 'June bug and the
rose chafer. The larval June bug called the white grub or " molly
grub " is of considerable injury to underground roots, while the
adult form, injurious to foliage in a less degree, is a household
annoyance in the early summer. The "Japanese beetle {Popillia
japonica), a serious pest, was imported into New Jersey and Penn-
sylvania and has spread into adjoining states at the rate of about
twenty miles per year. The rhinoceros beetle is the largest American
species. In the West Indies related forms reach a length of six
inches.

The plant eating beetles ( Phytophaga) include the pea and bean
weevils {Bruchidae), the leaf beetles {Chrysomelidae), and the long-
horned beetles {Cerambycidae).

The Bruchidae larvae feed on the seeds of peas and beans and are
called bean-weevils. The most injurious Chrysomelids include the
elm-leaf beetle, and the Colorado potato beetle, which is one of the
largest of the Chrysomelids and an important enemy of the potato.
The Cerambycidae are long-horned beetles including many wood-
boring forms, such as the apple tree borers and the maple borers.

196

ARTHROPODA

The larvae are called the " round-headed borers " to distinguish
them from the Buprestid larvae which are flat-headed. The
Tenebrionidae include the ordinary meal worm which is a minor pest
in spoiled grain, but is useful in feeding pet birds and " horned
toads." The Meloidae, or blister beetles, feed on plants. They are
used to supply the cantharides or Spanish fly used for blistering.
The snout beetles {Rhynchophord) include the bark beetles, most
destructive to trees, and the Curculios or weevils. The Mexican
cotton-boll-weevil has cost the South many thousands of dollars by
destroying its cotton, while the alfalfa weevil is a serious pest on the
West Coast.

Fig. 92. Blastophagay the insect which pollinates figs. (U. S. D. A.)

Order 19. Hymenoptera. {Gall-flies, Ants, Wasps and Bees.) —
The sawflies, horntails and gall flies are boring Hymenoptera whose
larvae feed on the leaves of shrubs and in some cases induce develop-
ment oi galls.

The chalcid flies {Chalcidoidae), minute parasites attacking the
eggs and larvae of injurious insects, are for the most part extremely
beneficial to man. One species is responsible for the fertilization
of the fig. The fig-wasp has recently been introduced from Asia
Minor into California. The gall-flies {Cynipoidea) utilize a sharp
ovipositor to thrust their eggs into green stems of oaks, roses and a
few other plants where the hatching larvae stimulate the plant to

ARTHROPOD A 197

form a gall. The giant oak-gall grows to the size of the human fist.

The Ichneumonoidae are parasitic hymenoptera attacking many-
injurious insects such as the cabbage butterfly, tent-caterpillars,
cotton-worms, brown-tail and tussock moths.

The braconid flies {Braconidae) are also valuable in that they
parasitize plant lice, tomato worms, sphinx caterpillars and fall
web-worms. The Serphoidea are a group of mostly small insects
parasitic on other insects.

In the stinging hymenoptera, which include the ants, bees and
wasps, the females and workers sometimes have the ovipositor
developed into a " sting."

Ants. {Fo7-micoidea.) — Found in nearly all parts of the world,
and comprising some twenty-five hundred species, ants have de-
veloped to a marked degree a differentiation in body structure and in
habits. The first two segments of the abdomen are expanded dor-
sally, serving as a peduncle to the rest of the abdomen. The nest
or home, usually underground, is divided into many channels and
passages.

The carpenter ant {Camponotus penn) builds its nest in the dead
wood of living trees and of buildings. The mound building a?jt
builds ant hills ten feet in diameter. The slave making ants {Formica
difficilis) depend on their servants (other ants) for shelter and food.
(See Communities, p. 484.)

The corn louse ant {Lasius brunneus) tenderly cares for one of the
extremely injurious aphids attacking the roots of corn. The tiny
red ant {Myrmicidae) , while something of a pest in this country,
becomes an actual menace in the Orient.

Stingless ants, the Campanothinae, are provided with a cushion-
like poison apparatus and secrete formic acid. Males do not possess
a poison.

Wasps. — The digger wasps {Sphecoidea) are distinguished from
the true wasps by their non-folded wings. They are solitary and
place paralyzed insects and spiders in their nests, where the larvae
feed on living helpless prey.

The true wasps ( Vespoidea) include the solitary wasps and the
social wasps. The solitary wasps {Eumenidae) resemble the digger
wasps in that they form burrows. They deposit their eggs and then
abandon them. (Consult Taylor, L . H., 1922, Psyche, vol. 29,
no. 2.) The social wasps ( Vespidae) include t\v^ yellow jackets and
hornets. The queens have stings but the males are harmless. Social

ipS ARTHROPODA

wasps feed the young continually through the larval stage of about
two weeks. The white-faced hornet makes a large paper nest.

The Chrysidoidea are parasitic Hymenoptera, about one-half inch
long, feeding on larvae of other Hymenoptera, or on the stored food
in their nests.

Bees. — The Apoidea include the bees. Bees are stouter bodied
than wasps and usually hairy. Their tarsal segments are flattened
and enlarged for carrying pollen.

The short-tongued bees are either solitary or gregarious, but never
social. Most of them are mining bees, sinking perpendicular shafts
a foot into the ground of grassy fields. The long-tongued bees
{Apidae) have the lower lip greatly developed for securing nectar.
The leaf cutter is a solitary species depositing her eggs in a hole in
some trees, with a supply of pollen and nectar for the young, and
then abandoning them. The guest bees {Psithyrus), regarded as
degenerate bumble-bees, have no worker forms but infest the nests
of solitary bees.

The social bees or " bumble-bees " {Bombus) live in communities
like the ants. They are important in the pollination of clovers.
(See page 484.) The queen usually starts her nest in a deserted
mouse's nest. The honey bee {Apis mellifera),^ a native of Europe,
has been domesticated the world over for centuries. There are
two genera, one stingless, the other including our common hive bee.
The colony consists of queens, drones and neuter workers. The
queen is fed on " royal jelly," which is a nutritious fluid excreted by
the nurses. The bee is able to lift and carry about twenty-five
times its own weight (Figure 93).

Honey. — For centuries honey has been used for food and at the
present time the United States produces about 250,000,000 pounds
of honey annually. Although it is reported to be lacking in vitamins
and minerals, honey is esteemed as a delicacy and is used in the
preparation of medicines and candies.

"The honeys of Hymettus and of Hybla were especially famous
In ancient times; and both retain to the present day their char-
acteristic flavor of wild thyme." (Consult L. Whibley, "A Com-
panion to Greek Studies." Cambridge University Press, 1905.)

* Alpatov, W. W., 1929, furnishes a new classification of bees in "Biometrical stud-
ies on variation and races of the honey bee {Apis mellifera)". Quart. Rev. of Biol.,
vol. 4, no. I, pp. 1-58, March. Vergil, in one of the finest passages of ancient poetry
(Georgics, Book IV), treats of the culture of bees. He discusses the placing of hives,
the managing of swarms, and describes a battle between two discordant "kings."

ARTHROPODA

199

In Northern Asia Minor poisonous honey has recently been
reported. This phenomenon was described earlier by Xenophon
and Aristotle. The bees are supposed to secure toxic nectar from
two species of rhododendron. The toxic honey causes giddiness
and sometimes a brief loss of consciousness, followed by a short
period of general malaise " as though one had been on a spree."

Worker Queea JDrone

Fig. 93. Worker, queen, drone. (From Phillips, U. S. D. A. Farmers Bull. 447.)

Methods of Insect Control. — Insects are controlled by poisons
acting through the alimentary canal or by contact. Sucking insects
are controlled by contact poisons while biting and chewing insects
are controlled by internal poisons.

Contact Insecticides. — In the adult condition, the chief sub-
stances used as contact insecticides against sucking insects, such as
flies and bugs, are lime sulphur wash, whale-oil soap, kerosene
emulsion, tobacco decoction, miscible oils, pyrethrum, lime dust,
commercial sodium fluoride, carbolic acid emulsion, and white
arsenic. In the case of aquatic larvae like those of the mosquito, a
thin film of oil or a thin coating of some substance like Paris green
or pyrethrum proves effective.

Stomach Poisons for Biting Insects. — In the case of the biting
insects attacking trees and vines, it is customary to spray or dust
with active poisons such as Paris green, arsenite or arsenate of lime,
arsenate of lead, hellebore, or sodium fluoride. Arsenate of lead
is used in preference to Paris green.

The Use of Gases. — Repellants such as naphthalene are used to
drive insects away. Lime repels the striped cucumber beetle, while

200 ARTHROPODA

whitewash containing a repellant chemical is used on tree trunks to
drive away the egg-laying adults of borers. The poisonous gases
most commonly used as fumigants in insect control are carbon
bisulphide, naphthalene, hydrocyanic acid gas, sulphur dioxide,
tobacco, formalin and carbon tetrachloride. Young trees are
usually fumigated when imported into a state or received from a
foreign country. In the orchard, trees are covered with tents and
fumigated.

Temperature Control. — Fall cultivation with reference to the
susceptibility of the animal to low temperatures proves beneficial in
killing wire worms, potato beetles, tomato worms and grasshoppers.
Superheating will kill most of the flour mill insects. The Mediter-
ranean fruit fly is limited to a temperature above 50° F., so will
probably never get a foothold in any but our Southern States.

Burning. — As weeds are likely to harbor injurious insects, they
should be destroyed. Larvae and adults of garden and orchard
pests are burned with the infested brush and vines.

Natural Enemies. — Sometimes pests are imported into a new
territory without the simultaneous introduction of their natural
enemies. It is then necessary to find the most important forms that
prey upon them. Such has been the province of explorers working
for the United States Department of Agriculture.

Next to the insects themselves, the birds are our most effective
insect enemies.^ Some of the most important are the quail, the
robin, the cuckoo and the sparrows. Even the despised crow more
than pays for the small amount of corn that he eats. Measures
that prevent the multiplication of wild races of cats will prove ef-
fective in the protection of the birds.

Other Protective Measures. — Valuable lumber is sometimes
stored under water in order to prevent the action of wood borers.
The use of fertilizers to stimulate plant growth may hasten develop-
ment so that the plant will be able to resist an insect attack. To
protect from the tent caterpillar, trees are frequently banded with
tar and wrapped in burlap. Crop rotation and early lure crops
often rid a plot of potato beetles. Ballou of the U. S. Department
of Agriculture discovered (1928) that after a meal of geranium
leaves or petals, the Japanese beetle becomes paralyzed. Post-
mortems on the 35 per cent of paralyzed beetles which died inside

® Strickland, E. H. 1928. Can birds hold injurious insects in check? Sc. Men.,
vol. 26, pp. 48-56.

ARTHROPOD A 201

of twenty-four hours showed that the digestive tract is destroyed in
that time, and that all soft parts of the body cavity are disintegrated
in forty-eight hours. The geranium is particularly attractive to the
Japanese beetle.

Class 5. Arachnida. — These air-breathing Arthropoda have no
antennae, or true jaws; have the head and thorax fused into a
cephalothorax; and at the posterior part the abdomen; and have
four pairs of walking legs, with their first pair of appendages de-
veloped into nippers, or chelicerae. They include spiders, mites,
ticks, scorpions, and the king crab.

Scorpionidae. — The scorpions are found in warm regions hiding
away during the day and coming forth at night to prey on insects
and spiders, which they sting with their poison fang at the tip of the
abdomen. The sting of an ordinary scorpion of three or four inches
has been compared with that of a hornet. Patten believes that
scorpions are descended from the fossil Merostomata {Eurypterida).
(See pages 207, 218.)

Phalangidea. — The harvest men or " daddy-long-legs " have
extremely long legs and a segmented abdomen. They feed on
living insects.

Acarina. — The common red mite and the " red spider " of green-
houses attack plants. The chiggers or harvest mites attack mam-
mals, including man, burrowing into the skin and causing much
irritation. The follicle mite, Demodex folliculorum, invades the hair
follicles of mammals and man, producing black heads. The itch mite
is a parasite of the epidermis. The scab parasite, Psoroptes com-
munis, produces sores on cattle and horses.

Ticks are responsible for the transmission of a number of diseases.
The cattle tick, Boophilus {Margaropus) annulatus, is the medium of
transfer of a sporozoan, Piroplasma bigeminum, which causes Texas
fever. In Africa, a common tick, Ornithodorus moubata, has habits
like a bed-bug and causes relapsing fever.

Older Araneida. (Spiders.) — Spiders (Figure 94) are among the
most interesting of the Arthropoda. They construct webs, using two
kinds of silk, one dry and inelastic, the other viscid and elastic.
Spiders use silk to construct webs, to build tents or nests, and also
in locomotion. Man uses spider threads for cross-hairs in his
telescopes. Spiders are Arachnids, with the abdomen separated
distinctly from the cephalo-thorax, but the segments of each region
closely fused They have four pairs of legs and two pairs of mouth

202

ARTHROPODA

parts. The mandibles or chelae are large and end in a slender,
sharp-pointed hollow fang, through which poison flows. The palpi
{pedipalpi) are sometimes half as long as the legs.

The trap door spiders^ Cteniza^ dig tunnels, line them with silk.

13 ^2 14 18

Fig. 94. Internal anatomy of a spider. /, mouth; 2, sucking stomach; j, ducts
of liver; 4, so-called malpighian tubules; 5, stercoral pocket; 6, anus; 7, dorsal muscle
of sucking stomach; <?, caecal prolongation of stomach; g, cerebral ganglion giving off
nerves to eyes; 10, suboesophageal ganglionic mass; //, heart with three lateral openings
or ostia; 12, lung sac; /J, ovary; 14, 15, 16, 17, silk glands; 18, spinnerets; ig, distal
joint of chelicera; 20, poison gland; 21, eye; 22, pericardium; 23, vessel bringing blood
from lung sac to pericardium; 24, artery. (From Sedgwick, Textbook oj Zoology.
Courtesy of Macmillan and Co., Ltd.)

and equip them with a
hinged lid. The ground
spiders., Drassidae, deposit
their eggs in silken tubes
and do not spin a web.
The jimnel web weavers,
Agalenidae, weave concave
sheets of silk with a funnel
on one side, attaching the
web to blades of grass by-
threads. After a heavy
dew, the webs are conspic-
uous on the lawn or in the
field. The cobweb weavers
( Theridiidae) are small,
light-colored forms, hang-
ing downward from shape-

FlG.

95-

Epeira, a garden weaver.
A. M. Reese.)

(Photo by

ARTHROPODA 203

less mazes of threads, frequently spun in corners of rooms. The
orb weavers^ Epeiridae (Figure 95), construct webs that are mar-
vels of efficiency, and sometimes span streams twelve feet wide.

Poisonous Spiders. — The b/ack widow spider has caused a num-
ber of deaths. Kellogg states (191 5) that a diadem spider of 1.4 gr.
contains sufficient poison to destroy completely all the blood cor-
puscles in 2.5 litres of rabbit blood. Comstock says that the
tarantula^ frequently found in bunches of bananas, is incapable of
seriously injuring man.

Bibliography on Venomous Spiders

Baerg, W, J. 1923. The effects of the bite of Lactrodectes mactans.

Jour. Parasit., vol. 9, pp. 161-169, March.
Bogen, E. 1926. Arachnidism, spider poisoning. Arch, of Int. Med.,

vol. 38, no. 5, pp. 622-632, Nov. 15.
Comstock. The Spider Book.

Kellogg, V. L. 191 5. Spider poison. Jour. Parasit., vol. i.
Lloyd, J. S. 1921. Spiders used in medicine. Sc. Amer. Mon., vol.

60, July.
Reese, A. M. 1921. Venomous spiders. Sc, vol. 54, no. 1399, Oct.

21.

Reese, A. M. 1929. Economic Zoology. 3d Edition.

Other Classes. Xiphosura. — The king crab or horseshoe crab
(Figure 96), is the only living representative of an ancient group.
Related fossil forms from the Carboniferous indicate that it origi-
nated in fresh water. The horseshoe crab, Limulus, is a large
marine form (2 feet long), commonly found on our Atlantic coast.
It lives in shallow water and feeds on worms. It has a large
cephalo-thorax and a relatively large abdomen with a long caudal
spine. It is used for fertilizer and to feed hogs. It is particularly
interesting to us because of the theory of the origin of vertebrates,
developed by William Patten. (See p. 218.)

Pycnogonida. — Sometimes classed as relatives of the Arachnids,
these marine forms have four somewhat primitive eyes resembling
those of spiders. They have a slender cephalo-thorax and abdomen
and four pairs of jointed legs with seven or eight segments each. j

The alimentary canal extends as ceca^ into the legs. Organs of / /^X6
respiration are absent. The ma/es have four to seven cement glands "

on certain of their appendages, usually the third. The secretion

204

ARTHROPODA

cements the legs together in masses which are carried on the
" ovigerous " legs of the male, and in one species on the female.
The nervous system consists of cerebral, subesophageal and three
other thoracic ganglia with two pairs of abdominal ganglia. Meta-
morphosis usually occurs. The larvae of one genus are parasitic
on the Coelenterata. They have no economic significance.

Fig. 96. Limiilus polyphemus, the king-crab. A, dorsal view. /, carapace; 2,
meso- and meta-soma; j, telson; 4, median eye; 5, lateral eye. B, ventral view.
/, carapace; 2, meso- and meta-soma; j, telson; 4, chelicera; 5, pedipalp; 6, 7, 8, g,
3d to 6th appendages, walking legs; 10, genital operculum turned forward to show
genital aperture; //, 12, /j, 14, IS-, appendages bearing gill books; 16, anus; //, mouth;
/<?, chilaria. (From Shipley and McBride. Courtesy of Macmillan and Co., Ltd.)

Tardigrada. — The Tardigrada, slow-moving forms called " water
bears " are small soft-skinned animals living in fresh and salt
water or damp moss. They have four pairs of short-hooked, un-
jointed legs. The digestive tract is well developed, the buccal cavity'
containing teeth sometimes calcified. Their muscles are non-
striated. No respiratory or circulatory organs are developed. The
gonads are saccular and empty into the rectum. The nervous
system consists of cerebral ganglia, and a nerve cord with four
ventral ganglia.

General Consideration of the Arthropoda

Chaxacteristics and Distribution. — Deep sea Crustacea are huge
in size and have a brilliant red coloring. Some are phosphorescent.

ARTHROPODA 205

Many aquatic forms are microscopic in size. Except in certain
fixed forms, like the barnacles and parasitic forms like Sacculina,
we find bilateral symmetry.

The Arthropoda walk, leap, burrow, swim, and fly, with loco-
motor organs and accessory structures correspondingly developed.

Geographically they are most cosmopolitan. In the Island of
Cyprus, certain centipedes are found on the burning plains and in
the snows of the mountains. A fresh water crustacean, Lepidurus
glacialisy is found only in the Arctic regions. The brine shrimp
Artemia salina is found in brackish water and in pans of exceedingly
salty water evaporating in the sun. In certain hot springs, crus-
taceans and insect larvae live at a temperature of 60° C.

Integument and Musculature. — The skin of the Arthropoda con-
tains epidermal cells (pigmented membrane of the lobster) which
secrete a chitinous exo-skeleton frequently containing lime salts,
but found to be extremely thin at the joints. Chitin is anhydride
of dextrosaynine^ a sugar derivative. Growth is in most cases ef-
fected by a process of ecdysis or moulting^ in which the old shell
cracks off and the new skin rapidly hardens. The period just after
moulting is a most dangerous one for most Arthropoda, for their
brethren are cannibalistic. Under the epidermis we find connective
tissues and the dermis with nerves and blood vessels.

Circular muscles found in the Annelida are absent in the Arthro-
poda, the longitudinal muscles causing movement of the segments.
The appendages are well supplied with muscles.

Digestive System. — In parasitic forms the mouth may be ex-
tremely rudimentary. The wide difference in mouth parts of in-
sects gives a basis for their classification. The digestive tube varies
much with the type of food consumed. Crustacea like the lobster
have a short gullet leading to a large cavity, the stomach, which has
a gastric mill for gizzard-like grinding.

In insects with mandibles (grasshoppers, crickets, and locusts)
we find a well-developed gizzard. In the insects there is great
variation in the form and length of the digestive tube. In carniv-
orous species the crop, gizzard and large intestine are sometimes
absent. In bees the crop is the " honey-bag." There is no true
liver in the insects, but the functions of a hepato-pancreas are per-
formed by glands in the stomach.

In spiders the pharynx and gullet are extremely small and the

2o6 ARTHROPODA

alimentary canal Is short and straight. The stomach and intestine
send out lateral tubular or bladder-like expansions.

There are many species o^ parasitic Arthropoda. Fish lice (crus-
tacea) are external parasites and suck in nourishment. Rhizo-
cephala, such as Sacculina, send ramifying absorptive roots through
the body of the host. But in insects and arachnids we find parasi-
tism most highly developed.

Respiration.^" — In water-breathing Arthropoda we find modified
appendages (gill-books of the king crab) or well-developed gills
such as in the lobster. The air breathers have a highly developed
tracheal system opening to the exterior by paired spiracles or
stig?7iata.

Circulatory System. — The system of circulation of Arthropoda is
not closed but an open one with sinuses playing an important part in
the collection of impure blood. The heart is usually elongated and
dorsally situated in Arthropoda. The Crustacea (lobster) have a
shield-shaped heart just posterior to the stomach. The blood enters
t\vQ pej'icaj-dial iinus and passes into the heart by several pairs of ostia
which have valves. Arteries leave the heart and pass to the inter-
cellular spaces.

The orange color of the blood of the prawn, and the yellow
color of the insects' blood are perhaps due to carotene, according
to A. C. Redfield. The green blue color of the blood of a lobster
is due to hemocyanin.

The role of carotene, a highly unsaturated hydrocarbon (CgoHse)
as an important agent in holding and slowly emanating absorbed
radiant energy, is a subject that interests the author of this text.
(P. 442.)

Excretion. — In Insects and Arachnids there are excretory tubules
(Malpighian tubules) which communicate with the intestine. In
the lobster and allied Crustacea, the paired green glands send their
secretion out from pores at the bases of the antennae.

Nervous System. — In Arthropoda the cerebral and sub-
esophageal ganglia have developed highly. We also find that the
thoracic ganglia are large and show the efi'ects of a lateral fusion.
The nerves in the thoracic region are especially well developed. On
the whole the nerve cord reminds one of that of the Annelid but is
more highly developed.

*° Lee, M. O. 1929. Respiration in the insects. Qu. Rev. of Biol., vol. 4, no. 2,
pp. 213-232.

ARTHROPODA

207

Sense Organs. — Tactile and olfacto-gustatory senses are ex-
tremely well developed in the group. ^^ Equilibratory organs
(otocysts) are found at the base of the antennules in the Crustacea.
In the mosquito we find auditory vibratile hairs, while the grass-
hopper has specialized tympani^ with nerve cells for the reception of
sound waves.

Vision is accomplished by two kinds of eyes, simple ones called
ocelli^ and compound ones. The compound eye consists of om-
matidia arranged radially around the end of the optic nerve. Each
ornmatidium consists of an external cornea (facet), a cellular cone-
like lens, sensory retinal cells which receive the light, and pigment
cells which separate the retinal elements of the ommatidia from each
other.

Fig. 97. Three trilobites. A, a Cambrian species; 5, a Devonian species, showing a
compound eye; C, an Ordovician species. (From Norton, Elements of Geology.)

Fossil Relatives. Eurypterida (Merostomata) .—This order is
linked with Limulus by many Paleozoologists. Specimens six feet
long are found in strata from the Cambrian to the Carboniferous.
The head is small and unsegmented, bearing two lateral compound
eyes, two median ocelli, and six pairs of gills, covered by plates.

" In insects the chemical sense is much more highly developed than in man. The
mouth parts and tarsal segments of the red admiral butterfly {Pyrameis atalantd) are
256 times as sensitive to saccharose as the human tongue. Olfaction in the bee is keen;
but the bitter substances such as quinine are readily accepted when mixed with saccha-
rose. (D. E. Minnich. 1929. The chemical senses of insects. Qu. Rev. of Biol.,
vol. 4, no. I, pp. 1 00- 1 12, Mar.)

2o8 ARTHROPODA

Patten considers that Paleozoic Eurypterids have scorpions as their
survivors and that the Ostracoderms represent their fossil descend-
ants, which led towards the true Vertebrates. (See page 219.)

Trilobita. — The extinct trilobites (Figure 97) were dominant
species in the Cambrian period, but disappeared in the Carboni-
ferous. The limbs resembled those of Crustaceans and antennae
were present. It has been suggested that trilobites descended from
a stock common to Arachnoidea and Crustacea.

Arachnoidea. — The scorpions are represented in the Silurian
rock by fossil forms similar to those now living. All living Arach-
noidea are represented in Tertiary deposits. Crustacea are abun-
dant as fossils, from the early Paleozoic. Myriapoda are found
from the Devonian. Insecta appeared in the Pennsylvanian.

CHAPTER XIII

Chordata

Classification

Subphylum Hemichorda (Enteropneusta).
Subphylum Urochorda (Tunicata or Ascidia).
Subphylum Adelochorda (Acrania).
Subphylum Vertebrata (Craniata).

Class Cyclostomata.

Class Pisces.

Class Amphibia.

Class Reptilia.

Class Aves.

Class Mammalia.

The Phylum Chordata Includes not only common Vertebrate
animals such as Fishes, Amphibia, Reptilia, Birds and Mammals,
but also includes certain marine forms that are extremely significant
in discussions of the probable origin of Vertebrates from Inverte-
brates.

The name Chordata is derived from the notoc/iord, which is
found at some stage of the existence of all Vertebrates, but is per-
sistent in the adults of those intermediate types that we will shortly
proceed to describe. The notochord is a long, cylindrical, double-
pointed rod, which is located ventral to the nerve cord. Notochor-
dal tissue consists of large vacuolated cells (somewhat resembling
the pith of plants) with their nuclei confined to the dorsal and
ventral regions. The vacuoles of these cells are filled with liquid
which renders them turgid. The notochordal sheath is extended
dorsally to enclose the nerve cord.

Comparison of Vertebrates and Invertebrates

Up to the present time we have been dealing entirely with the
Invertebrates. It is therefore desirable, before we go further with
the animal phyla, to compare briefly the Invertebrates with the

209

2IO CHORD AT A

Vertebrates, pointing out the distinguishing features which mark
an advance in the Vertebrate type.

Invertebrates versus Vertebrates

Dorsal heart. Ventral heart.

Solid nervous system. Tubular dorsal nervous system.

No endoskeletal structures. Either a notochord or a vertebral column.

There is no Class of the Invertebrate Metazoa whose characters
have not been repeatedly suggested to reveal affinities with the
Vertebrates.

Before discussing the different theories of Origin of the Verte-
brates, it will be best to take up the anatomy of examples of the
Hemichorda, Urochorda and Cephalochorda, since these are con-
sidered by some to be connecting types.

Subphylum Hemichorda. (Enteropneusta.) Characteristics.
(Balanoglossus.) — i. Hollow, tubular notochord, opening into a

straight alimentary canal.

2. Gill slits.

3. Dorsal blood vessel and anterior
(dorsal) heart.

4. Dorsal and ventral nerve strands,
with many nerve fibers and scattered giant
nerve cells.

The genus Balanoglossida includes

Balanoglossus {Dolichoglossus) kowalevskii.

This form is divided into three regions,

the proboscis^ the collar, and the trunk.

The proboscis, when distended with water,

serves as an organ for burrowing in the

mud. Gill slits open into the anterior end

of the straight alimentary canal. The

paired hepatic cecae are located near the

posterior end of the digestive tube. The

dorsal and ventral blood vessels receive

blood from the anterior heart. Excretions

are extracted by the kidney, which sends

its wastes out through the proboscis-pore,
Doscis; 2, collar; ?, giu-siics. . , , n 1 n • j t-i

(After A. Agassiz. Courtesy With Other expelled fluids. The sexes ^ are

of Henry Holt & Co.) separate and the ger7n cells, formed in a

Fig. 98. Balanoglossus.
Linville and Kelly. /, pro-
boscis; 2, collar; j, gill-slits.

CHORDATA

211

double row of ovaries or testes, are extruded through pores in the
body wall. (Figure 98.)

Some species of Balanoglossidae have a ciliated larva called the
Tornaria, which was once considered a larval Rchinoderm. (See p.
217.) Cephalodiscus and Rhadopleura are colonial Hemichorda,
which reproduce by buds. Both these forms were at one time re-
garded as Polyzoa. They have small probosces, and their alimen-
tary canals are bent. Both are deep-sea forms.

Subphylum Urochorda. (Tunicates, Sea Squirts, Ascidians.)
Characteristics. — i. Retrogressive metamorphosis.

2. Multiplication by budding, as well as by gonads.

3. Reversal of the heart beat.

4. A tunic or mantle composed of cellulose (CeHioOs).

Adult sea squirts (Figure 99, A, B, C, D, E, F) resemble the
siphonate molluscs in the possession of incurrent and excurrent ori-
fices and a mantle. The Tunicates hence were long associated with

Molgula
manhattensis

Molgula
arenata

Eugyra
pillularis

Botryllua
gouldii

Cynthia partita

Salpa cabotii

Fig. 99. A group of Urochorda. J, Molgula manhattensis. B, Molgula arenata.
C, Eugyra pillularis. D, Cynthia partita. E, Botryllus gouldii. F, Salpa Cabotii.
(From Verrill.)

212 CHORD ATA

the molluscs. Later, they were associated with the worms. Their
development, however, shows them to be related to the Vertebrates.
The larval ascidian is more highly developed than the adult.

Anatomy and Physiology. — The tunic or mantle has the same
chemical constituents as cellulose (CeHioOs). Nowhere among
animals is there such a rich formation of cellulose. The anterior
part of the digestive tract is modified into a pharynx or branchial
chamber, the walls of which are perforated by a number of gill
slits leading to the exterior, or to a peri-branchial chamber, and from
this to a cloaca. While respiratory water passes through the gill
slits, the food particles which it contains are received by a ring-
shaped ciliated band and, enveloped by mucus, are led to the esoph-
agus. The mucus is formed by a ciliated glandular groove, the
endostyle on the ventral surface of the pharynx. The ventral tubular
heart lies in the pericardium between the gill region and the stomach.
It changes the direction of its contractions frequently, first driving
the blood to the gills, then resting; then pumping it from the gills
and sending it to the stomach. The ductless excretory organs are
in the second loop of the intestine; the dorsal ganglion and the
subneural gland are the only remains of the comparatively well-
developed brain of the larva. The subneural gland which is asso-
ciated with the dorsal ganglion is homologous to the hypophysis ^
of the higher vertebrates. The gonad is hermaphroditic, the testis
surrounding the ovary, and the animal is first a female, then after
pregnancy becomes a male. The larva of the ascidians is active,
swims by a long tail, looks like a tadpole, and has a notochord.
(Figure loo.)

Description of the Larval Ascidian. — The tail is fringed with a
caudal fin which is an outgrowth of the thin test covering the whole
surface. The notochord is in the axis of the tail. The nerve cord is
dorsal and forms the trunk ganglion and sense vesicle with otocyst
and eye. The digestive system consists of pharynx, esophagus,
stomach and intestine. The larva remains only a few hours in the
tailed free swimming stage. Then It becomes fixed by adhesive
papillae and begins to undergo retrogressive metamorphosis.
Molgula manhattensis (which has no tailed form) reaches its full size

^ Butcher (1930), Jour. Exp. Z06I., vol. 57, no. i, pp. i-ii, has shown that in
Molgula manhattensis the pituitary gland has the oxytocic principle of posterior pitui-
tary. (See page 448.)

CHORDATA

213

of one inch in about six weeks. Botryllus (the star-spangled jelly)
is a compound ascidian ranging from New Jersey to Maine.

Economic Importance. — The sea squirt or " sea-peach " is eaten
in South America and the Mediterranean countries, but is said to
taste rather bitter.

Fig. 100. Internal anatomy of the adult sea squirt. (Courtesy of Amer. Mus. of

Nat. Hist.)

214

CHORDATA

•^j

/

■o

>o

Subphylum (Cephalochorda, Adelochorda,
or Acrania). Type — Branchio stoma ^ or
Amphioxus. — Amphioxus, the lancelet, is
transparent, less than three inches long, lives
in shallow sea water, partly buried in sand,
burrows head foremost, swims at night.
Beebe reports them in the Sargasso Sea.
(Figure loi.)

It has a median dorsal fin, extending
posteriorly to form the caudal fin and then
ventrally to the post-atrial region to form
the ventral fin. The laterally situated meta-
pleural folds occupy the position of lateral
fins in fishes.

Body Wall. — The outer covering is a
single layer of columnar epithelium cells,
the epidermis., with sensory cells, goblet cells
(unicellular glands) and ciliated cells. The
dermis consists of soft connective tissue.

Muscular Layer. — The muscular layer
has strikingly definite metameric segmen-
tation. The myomeres, myotomes or muscle
plates are alternately arranged on the right
and the left sides permitting flexible lateral
movements and with connective tissue septa

2 Balanoglossus, the Tunicates, and Branchiostoma
have the following characteristics in common at some
stage in their existence: (i) notochord; (2) pharyngeal
gill slits; (3) dorsal nervous system.

Fig. ioi. A lateral view of Amphioxus (trans-
parency), a, anus; «./>., atrial pore; f./., caudal fin;

^&D cir., cirri, on the edge of the vestibule leading to the
mouth; ^./., dorsal fin; r, fin rays; g, gill of branchial
structures consisting of alternate slits, through which the
water passes, and supporting plates, in the walls of
which are the blood vessels; in., intestine, from which

: as a diverticulum springs /, the liver; m, the mouth sur-

rounded by a fringed velum; my., myotomes or muscle
segments; n.c, notochord; 0, ovaries; s.c, spinal cord;

'G ^•/•> ventral fin. (From Galloway. Courtesy of P.
Blakiston's Sons Co.)

CHORDATA

215

called myocommas. The dorsal body wall is greatly thickened as
it is in all Chordates and contains the hollow nervous system and
the notochord. The notochordal sheath of connective tissue is
produced dorsally into a covering for the canal containing the nerv-
ous system. The cells are
turgid with fluid.

Digestive System . — The
mouth has ciliated oral cirri,
with tactile sensory cells.
The twelve velar tentacles
extend as strainers from the
velum across the mouth.
The pharynx with its one
hundred pairs of gill slits
functions in respiration as
well as digestion. The epi-
branchial groove is ciliated,
dorsally indenting the phar-
ynx, and the ventrally situ-
ated endostyle (Figure 102)
(hypobranchial groove) fur-
nishes mucus which entangles
food particles. The food is

carried by the cilia of the „ _ .• ^ ^i- ,,

•^ . Fig. 102. Cross-section Amphioxus.

epibranchial groove to the m- Hertwig-Kingsley. a, aorta descendens; b,
testine. The liver, attached peribranchial space; c, notochord; ro, coelom
to the anterior end of the (branchial body cavity); e^ hypobranchial
intestine, protrudes into the groove, beneath It the aorta ascendens; g,
1 1 ;,.,, TU^ V,o gonad; ^^, gill arches; ^i, pharynx; /, liver; »7,

pharyngeal cavity. Ine he- & ' '^ ' '^ ^

^ ■' ° . •J- • muscles; «, nephndia, on the lert with an

patlC secretion is a digestive ^..^w; r, spinal cord; .«, spinal nerve; .;>, gill
juice probably analogous to glit. (After Lankester and Boveri. Courtesy
the secretion of the pancreas of Henry Holt & Co.)
of the vertebrates.

Respiratory System. — The atrium is a wide chamber between the
body wall and the pharynx into which the gill clefts lead. As in the
tunicates the cilia lining the gill clefts produce a current setting in
at the mouth, entering the pharynx and passing thence by gill slits
into the atrium and out the atriopore. The current is for respiration
as well as food. The coelom consists of paired cavities in the pharyn-
geal region connected by narrow canals in the gill folds with the
endostyle.

21 6 CHORD ATA

Circulatory system consists of a dorsal vessel (paired and un-
paired dorsal aortae); a ventral vessel (subintestinal vein and ven-
tral aorta); and commissural, connecting, afferent and efferent
branchial arteries with intestinal capillaries. The circulation differs
from that in the Annulata, since the blood in the ventral vessel
travels forwards and the blood in the dorsal vessel travels backwards
which is the opposite from the condition in the Annelida. All the
intestinal blood passes through the liver before reaching the ventral
aorta. The hepatic portal system is characteristic of all verte-
brates. The blood is almost colorless with no leucocytes and but
few erythrocytes.

Excretory System. — There are 90 pairs o( nephridia situated above
the pharynx. Columnar and excretory cells are situated on the
floor of the atrium.

Reproductive System. — The sexes are separate, 26 pairs o{ gonadial
pouches opening into the atrium. The ripe germ cells burst from the
inner walls of the gonadial pouches and escape by way of the atrium
and atriopore to the external water where fertilization takes place.

Nervous System. — The dorsal nerve tube has an axial cavity, the
neurocele, which is dilated anteriorly to form the cerebral ventricle.
The dorsal portion of this ventricle is dilated into a pointed pouch,
the median olfactory lobe, while in the ventral posterior portion there
is a depression probably corresponding to the infu7jdibulu7n of higher
forms. A large number of spinal nerves come from the spinal cord.
They arise alternately, in each segment, two dorsal nerves, sensory
and motor, supplying the skin and transverse muscles; and two
ventral nerves, purely motor, supplying the myotomes.

Sense Organs. — The olfactory pit {hypophysis) is a ciliated depres-
sion opening externally on the left side of the snout. The median
cerebral " eye " has no lens and may not be sensitive to light. The
socalled gustatory groove on the roof of the buccal cavity may not
be an organ of taste. There are no equilibratory or auditory organs
known.

Kconomic Importance. — Vast quantities of the Amphioxus are
used as food by the Orientals, particularly the Chinese.

Theories of the Origin of Vertebrates

Theories of the origin of vertebrates include the Amphioxus
theory, the Annelid theory, the Nemertean theory and the Arthropod

CHORDATA , 217

theory. The higher phyla of Invertebrates have practically all
been studied by investigators with the idea that affinities with the
vertebrates could be determined.

Amphioxus Theory. — The Amphioxus theory as developed by
various workers and set forth by Willey is as follows. The ancestor
of the vertebrates was a free swimming animal intermediate between
the tadpole of the Tunicate and Amphioxus. It had the ventral
mouth, pituitary and notochord (limited) of the Tunicate; and the
myotomes, coelomic epithelium, and straight alimentary canal of
the Amphioxus. The chief factor in the evolution of the verte-
brates has been the concentration of the central nervous system
along the dorsal side of the body and its conversion to a hollow tube.
The hypophysis may have become evolved in connection with a
functional neuropore. Adam Sedgewick and Van Wijhe suggested
that the neural canal had as its original function the promotion of
oxygenation of the tissue of the Central Nervous System, the water
entering by the neuropore and leaving through the posterior neu-
renteric canal. Harmer and Brooks suggested independently that
the gill slits arose at first to carry away the bulk of water con-
stantly entering the mouth with the food, obviating the necessity
of the flow of water through the alimentary canal. Later they aided
in performing the function of respiration. (Cephalodiscus has
luxuriant branchial plumes, sufficient for respiration, and the pair
of gill slits allow the water to pass from the pharynx.) The noto-
chord occurs in Balanoglossus {Enteropneusta) in the proboscis;
and in the tail of larval Tunicates. In Balanoglossus it may be a
divergent structure. The notochord may have arisen as a solidi-
fication of the endoderm, continued into the caudal portion of the
body to afford axial support for a locomotor tail. Endoderm as a
stiffening substance has been developed in some medusae and hy-
droid polyps as there is skeletal tissue in their tentacles in the form
of a solid endodermal axis.

The Amphioxus theory supposes that Amphioxus was derived
from a Tunicate (Ascidian) and that the Tunicate arose from a form
possibly hke Balanoglossus. Balanoglossus may or may not have
arisen from the Echinodermata. The ciliated Tornaria larva of
Balanoglossus is similar to the larvae of the Echinoderms in that it
possesses bilaterality, ciliated bands, pelagic life and is small and
quite transparent.

That the earlier fishes were similar to Amphioxus and that the

21 8 CHORDATA

higher fishes developed from the primitive type through the in-
fluence of a rapid stream environment is the belief of T. C. Chamber-
lain.

Arthropod Theories. — The theory of Gaskell (1908) is based on
the assumption that the whole alimentary canal of a crustacean-like
Arthropod united with the nerve cord to form the hollow brain and
spinal cord of the vertebrates. Gaskell's theory reflects his knowl-
edge of physiology, but indicates his lack of training in comparative
anatomy, embryology and paleontology.

Patten's Arachnid theory was first published in 1889 in the
Quarterly Journal of Microscopical Science, and was followed by a
number of important papers preceding the publication of his book
in 191 2. Dr. Patten has pointed out (personal communication,
1 931) that the Arachnid theory gives a satisfactory explanation
of the other theories of evolution of vertebrates while none of these
theories explains the detailed resemblance between Vertebrates and
Arachnids,

The following summary was furnished by Dr. Patten (consult
his article in the Quarterly Journal of Microscopical Science, vol,
Si.PP- 317-378, 1890):

"The Arachnid theory — 1890 — is based on the following evi-
dence: (i) In the Arachnids, the first sixteen, or more, metameres
form a characteristic pattern, consisting of five groups of highly
specialized functions and organs, all of them different and all ar-
ranged in a definite sequence. (2) This basic pattern is essentially
the same as that in the "head" of vertebrates, and all the corre-
sponding organs in each group have essentially the same structure,
and develop embryologically in essentially the same ways. Some
of the corresponding parts are the notochord and the endocranium,
the main divisions of the brain, special groups of sense organs,
nerves, ganglia, somites, gill sacs, and oral arches. (3) The marine
Arachnids were the highest animals in existence during the long
and very early geologic eras. In the Cambrian, or some pre-Cam-
brian era, they apparently gave rise to the great class of Ostraco-
derms, which are mainly Silurian; and they in turn gave rise to the
true fishes, with united oral arches, which first appeared in the
Devonian. Many peculiarities of the Ostracoderms, especially
the structure of the exoskeleton and the oral arches, support this
conclusion. (4) The Tunicates, Amphioxus, and other chordate

CHORD ATA 219

types, are regarded as defective, aberrant offshoots of the main
vertebrate arachnid phylum."

The recent discovery by Prof. J. Kiaer of well-preserved fossil
Ostracoderms in the Silurian rocks of Norway, and the collection by
Professor Stenso of perfectly preserved fossils of one of them, Cepha-
laspis, from the Devonian rocks of Spitzbergen, have given new evi-
dence to support Professor Patten, and gratified the friends of this
"grand strategist of evolution.!' Serial sections of the Spitzbergen
specimens studied by Patten indicate that the "radiating bony chan-
nels for the cranial nerves, and many other architectural features of
the anatomy of the head conform to the general plan seen in the
heads of fossil Enrypterids and other arthropods." ^

Professor Patten has made three expeditions to the Island of
Oesel excavating fossils and in 1931 found six new species of ostraco-
derms.^

Annelid Theory. — The Annelid theory advanced by Dohrn,
Semper, Beard and Delsman postulates that an annelid is turned
over on its back and develops a mouth and anus. The notochord
is represented in the annelids by a bundle of fibers running along the
nerve chain, occupying a similar position to the notochord of the
chordata and apparently serving the same function of support.
Connective tissue encloses both nerve cord and fiber bundles
(Faserstrang.) just as the notochord and the spinal cord are
enclosed in the higher type.

The segmentally arranged nephridia correspond to the primitive
kidney tubes of the vertebrate kidney. The segmentally arranged
ganglia around the appendages of some worms ( Nereis) may cor-
respond to the branchial and lateral sense organs of the Ichthyopsida
and the ganglia of some of the cerebral nerves.

The fundamental relationship of the nervous system and the
vascular system to the digestive tract as found in the annelids is
quite comparable to the condition in the primitive vertebrates.

Wilder has indicated the present trend away from the Annelid
theory and points out that a worm-like ancestor does not necessarily
mean that we must accept an annelid. (See trochophore, p. 125.)

5 Gregory, W. K., 1928, in Creation by Evolution, edited by F. Mason, Mac-
millan Co., New York.

* Consult Patten, W., 1931, New Ostracoderms from Oesel. Science, vol. 73,
no. 1903, pp. 671-673. Tremataspis has, as predicted, paired jaws or oral arches, like
those in embryonic vertebrates (frog) and which work sidewise, not forward and back-
ward as in the united oral arches of adult vertebrates.

220 CHORDATA

Nemertean Theory. — The Nemerteans, probably related to the
Platyhelminths, were suggested as having affinities with vertebrates,
by Hubrecht. His theory attempts to homologize the proboscis
sheath of the Nemertean with the notochord of the chordate. He
suggests that the vertebrate nervous system developed from the
three nerve cords of a Nemertean. The dorsal nerve cord of the
Nemertean became the central nerve system and the lateral nerve
cords persist in the rami lateralis X, of the lower vertebrates. As
the other organs of the animals are not similar in arrangement the
theory seems of little importance.

References on the Origin of Vertebrates

Delsman, H. C. 1922. The Ancestry of Vertebrates as a Means of
Understanding the Principal Features of Their Structure and
Development. Weltevreden (Java).

Gaskell, W. H. 1908. The Origin of the Vertebrates. London,
Longmans-Green.

Hubrecht, A. A. W. 1883. On the ancestral form of the Chordata.
Quart. Jour. Micr. Sci., N.S., 23: 349-368.

Lull, R. S. 191 7. Organic Evolution. New York, Macmillan.

MacBride, E. W. 1914. Text-book of Embryology. Vol. i, Inverte-
brate. London, Macmillan.

Newman, H. H. Vertebrate Zoology. New York, Macmillan.

OsBORN, H. F. 1917. The Origin and Evolution of Life. New York,
Scribners.

Patten, W. 191 2. The Evolution of the Vertebrates and their Kin.
Phila., Blakiston.

Patten, W. 1920. The Grand Strategy of Evolution. Boston, R. G.
Badger.

Wilder, H. H. 1909. History of the Human Body. New York, Holt.

CHAPTER XIV

Cyclostomata

Craniata. — The Craniata include the vertebrates, from the eel-
like lamprey, up to man himself. In all we find that in the embryo
an axial notochord appears. This is persistent inside the centrum
of the vertebra of an elasmobranch, but is replaced in higher forms
by the true vertebral column.

Classification. —

I.

Cyclostomata

II.

Pisces.

III.

Amphibia.

IV.

Reptilia.

V.

Aves.

VI.

Mammalia.

Characteristics of Craniata. — i. Segmented animals without
external ringing of the body but with metameric arrangement of the
internal parts.

2. A cuticular skeleton absent, but there may be a horny epi-
thelium or dermal ossifications. (Scales, etc.)

3. An axial skeleton is present; either a notochord or skull and
vertebral column. Two kinds of appendages are supported by the
axial skeleton, the unpaired fins of the fishes and amphibia and the
paired fins, or limbs of the higher vertebrates.

4. The central nervous system is dorsal and hollow and consists
of cerebrum, midbrain, optic lobes, cerebellum, and medulla ob-
longata, with the spinal cord attached. The eyes and ears are the
most highly developed of the sense organs.

5. The respiratory organs arise from the endoderm; gill slits are
present in the embryo. In land forms, these are replaced by lungs,
developed from the hinder part of the pharynx.

6. The heart is ventral and consists of one or two auricles; and
one or two ventricles. In gill breathers the blood in the heart is
venous. Pulmonary respiration brings blood to the heart pure

221

222

CYCLOSTOMATA

from the left side. The sinus venosus brings the impure blood to
the right side of the heart. Circulation is a thoroughly closed

system.

Cyclostomata. (Gr., a circle; a mouth.) — The Cyclostomes,
forms just below the fishes, include hag-fish and lampreys, both of
which somewhat resemble eels but differ in a number of essential
characteristics. (Figure 103.)

Fig. 103. Cyclostomes. Upper figure, Pacific hagfish, Bdellostoma dombeyi.
X 3^. The light apertures along the sides are mucous canals, the dark ones are
branchial openings. Middle figure, Atlantic hagfish, Myxine glutinosa. X K- The
dots along the side are mucous pits; the left common branchial aperture is at *. Lower
figure, sea lamprey, Petromyzon marinus. X 3^. (After Dean.)

Characteristics. — i. No jaws.

2. No lateral appendages.

3. No scales.

4. No masticatory apparatus; rasping tongue present.

5. No atrial cavity.

6. Have a median unpaired nostril and the first distinct ap-
pearance of a head.

7. Have round mouth closed by the tongue.

8. Pocket-like gills.

9. Persistent notochord.

10. Vertebrae present, separated from notochord.

11. The gonads discharge into the coelom.

Myxinoids. — The hag-fishes produce slime and, when captured,
" turn water into glue." They are all marine. They attack dis-
abled fish and enter the gills or mouth. Their digestive apparatus
is so large that one meal takes a long time to digest. Blind, they

CYCLOSTOMATA 223

hunt at night. They are hermaphroditic, with an ovotestis, but one
sex always predominates.

Petromyzontia. (Stone; suck in.) — The lampreys are found in
both fresh and salt water, the marine species being larger. They
are predaceous, true vertebrate parasites. (Brook lampreys are
not parasitic.) The lamprey breathes through the mouth except
when feeding, then through the gill clefts.^ Gage and Day of
Cornell University showed that the lake lampreys have in their
buccal glands an anticoagulating substance similar to " hirudin."
(See page 116.)

The larvae, once called Ammocoetes, resemble Amphioxus. They
have a hood, median eye, endostyle, epibranchial groove (which
becomes the esophagus). The endostyle becomes the thyroid gland,
and the median fin specializes.

1 Consult Gage, S. H. 1927. The Lampreys of New York State. Supp. to
17th. Ann. Report, N. Y. State Cons rvation Commission.

Gage, S. H. 1929. Lampreys and tiieir ways. Sc. Mon., vol. 28, pp. 401-416,
May.

Surface, H. A. 1897. Lampreys of Central New York. Bull. U. S, Fish.
Comm., vol. 18, pp. 210-215.

Wheeler, W. M. 1900. Development of Urinogenital Organs of the Lamprey.
Zool. Jahrb., vol. 13, pp. 1-88.

CHAPTER XV

Pisces

Classification

Subclass Elasmobranchii.
Subclass Teleostomi.

Order 1. Crossopterygii.

Order 2. Chondrostei.

Order 3. Holostei.

Order 4. Teleostei,
Subclass Dipnoi.

Characteristics

1. Aquatic vertebrates.

2. Breathe by gills (vascular outgrowths of the pharynx). In the

Dipnoi a single or double swim bladder functions as a lung,
and the air is received at the surface of the water.

3. The swim bladder of the Teleostomi is used as a hydrostatic

organ.

4. There are two pairs of fins, pectoral and pelvic, and also unpaired

median fins.

5. The skin usually has numerous scales, formed from the dermis,

but covered with epidermis which may produce enamel.
Scales are suppressed in electric fishes, and rudimentary in
some other forms. Glandular cells are also found in the skin.
There are sensory mucus canals, for touch and chemical
sense. Some fishes have well-developed poison glands near
the fins.

6. The lateral line organs along the trunk are for vibrations of

low frequency.

7. The muscle segments persist throughout life. There is no muscle

in the dermis however.

8. The gut ends in a cloaca in many; in others a distinct anus is

situated in front of the genital and urinary apertures.

224

PISCES

225

9. The nostrils are paired; there are no posterior nares, so the organs

are exclusively olfactory.

10. There are no tympanic cavities or ear drums.

11. The heart is two chambered with venous blood except in the

Dipnoi where it begins to be three chambered and receives
pure blood from the lung as well as impure blood from the
body.

Apart from the Dipnoi, the heart has one auricle, receiving
impure blood from the body; one ventricle which drives it
through the ventral aorta to the gills, whence the purified
blood flows to the head and by the dorsal aorta to the body.
There is a sinus venosus receiving the impure blood and
sending it into the auricle and thence to the ventricle.
The conus or bulbus arteriosus, located at the exit of the
arterial trunk from the heart, becomes more bulbous in the
Dipnoi, presaging the development of the distinct bulb of
the Amphibian heart. There are no vena cavae, but there
are two posterior cardinal vessels.

12. The kidney is the persistent mesonephros. There is no distinct

urinary bladder. (Small paired ones in some fishes.)

Natural History

Subclass Elasmobranchii. (Gr., a metal plate; Lat., a gill.)
Characteristics. — The Selachii have a cartilaginous skeleton,
placoid scales, gills covered (separate covers), heart with arterial
cone, a spiral valve in the large intestine and no swim bladder.
Sharks have triangular teeth with notched edges; dogfish have flat,
diamond-shaped teeth. They are marine except one fresh water
Nicauragan shark. (Figure 104.)

The great white shark or " man-eater " {Carcharadon carcharius)
grows to thirty feet in length. Usually found in tropical waters, it
sometimes strays to the North Atlantic. It will follow ships and
seize refuse and so occasionally gets a " man overboard." Until the
summer of 191 6 all reports of attacks on man by sharks in American
waters were branded as false. Whale sharks reach a length of fifty
to sixty feet. They eat small fish, squids and shrimps, straining
them out of the water by means of the gill rakers. The thresher
shark has a much elongated upper lobe on its " super-heterocercal
tail," which furnishes a powerful weapon and also drives the small

226

PISCES

Nurse Shark

Gingli/mostoma cirratum (Gmelin)

Smooth Dogfish

Mustelus canis (Mitchill)

Hammer-head Shark

Sphyrna zygaena ( Linnaeus)

Sand Shark

Carcharias littoralis
(Mitchill)

Spined Dogfish

Squalus acanthias (Linnaeus)

Tiger Shark

Galeocerdo tigrinus
(Miiller and Henle)

Thresher Shark

Alopias vulpes (Gmelin)

Man-eater Shark

Carcliarodon carcharias
(Linnaeus)

^Mackerel Shark

Isurus tigris (Atwood)

Fig. 104. Sharks of various types. (After Nichols and Breder. Courtesy of N. Y.

Zoological Society.)

PISCES

227

fish together. Angel sharks are transition types between sharks
and the skates and rays. They have large pelvic and pectoral fins,
extending laterally. (Figure 105.) Rays and skates are much
flattened dorsiventrally. They vary in size from the small " rugs"
of the New Jersey coast to large skates eight feet in diameter.
(Figure 106.)

In the electric ray {torpedo-ray) modified muscle plates called
electropaxes are developed from the muscles of the pectoral region.
They are under control of the ray and connected with nerve centers
in the medulla. The whip-tailed or sting-rays have tails armed with
barbed spines, eight to nine inches long. At the base of the spines
poison is secreted which entering the wounds made by the tail
causes severe inflammation. Eagle rays may reach a width of
twenty feet. The animal envelops prey with its " wings." Pearl
divers have been drowned by these " sea vampires." Sawfish
may be twenty feet long with a five-foot snout equipped with saw-
like teeth. (Figure 107, A, B, C, D.)

Holocephali. (Chimeras.) — The sea cat has an operculum or
gill cover and five claspers developed from its fins. It reaches a
length of three feet and rarely attacks bathers. (Figure 108).

Subclass Elasmobranchii. Type of the Group — The Skate.^
General External Characteristics. — i. Body flattened dorsiven-
trally. (The flounder is flattened laterally.)

2. Pectoral fins broad, fused perfectly with head and trunk.
Pelvic fins well developed and bilobed, bearing claspers in the male.

3. Ventral mouth with teeth.

4. Paired nostrils located ventrally.

5. Dorsally situated spiracles, originally the first pair of gill
clefts, communicating with the pharynx.

6. Five pairs of gill clefts located ventrally. (Laterally in the
dogfish.)

7. Ventral anus leading into cloaca.

8. Two small pouches, one on each side of anus with two ab-
dominal pores opening into coelome.

Integument.— The epidermis has several layers of cells and is
richly supplied with glandular goblet cells. The dermis is studded
with bony dermal placoid scales or " skin teeth," which are based in

^ Since it is possible to secure rather small mature skates, many instructors prefer
to use them instead of the shark. We will therefore describe the skate, but present
figures to illustrate the nervous system of the dogfish.

228

PISCES

Fig. 105. The angel-shark {Rhina Squat'ind). J, dorsal view; B, view of the
mouth and nasal barbels. />./., pectoral fin; pv.f., pelvic fin; sp, spiracle. (Courtesy
of Am. Mus. of Nat. Hist.)

Fig. 106. Common skate. (Courtesy of N. Y. Zool. Soc.)

PISCES

229

Sting Ray

Dasyatis centrura ( Mitchill )

Butterfly Ray

Pteroplatea maclura ( Le Sueur)

Eagle Ray

Myliohatis freminviUei ( Le Sueur)

Great Manta

Manta birostris (Walbaum)

Torpedo

Tetronarce occidentaZis
(Storer)

Fig. 107. Rays. (Courtesy of Nichols and Breder and the N. Y. Zoological Society.)

230

PISCES

bone, cored with dentin or ivory and tipped with enamel from the
epidermis. The enamel is inorganic, the cells being replaced by
lime salts. The dentin contains 34 per cent organic matter and the
bone is cellular tissue.

tn.sp

Fig. 108. Chimaeroid fish. After R. Lull. (Courtesy of The Macmillan Co.)

There are senso?~y tubes or mucus canals on the ventral surface
just under the skin. They function for touch and chemical sense,
having ampullae with sensory cells at the inner ends and pores
opening to the outside. There are no spines on the ventral surface
except a few bristly ones in the region of the cloaca.

Muscular System. — The muscles are segmentally arranged, the
jaw muscles being well developed. Organs not present in the skate
are the electric organs, best developed in the teleosts, a South Ameri-
can eel {Gymnotus) and an African Siluroid {Malapterurus) , but
also found in the Elasmobranch torpedo ray. In the torpedo they
lie on each side of the head between the gills and the anterior part
of the pectoral fin. They are vertical prisms, divided by transverse
partitions of connective tissue into large number of cells formed
from metamorphosed muscle fibers. These electropaxes or electric
plates consist of muscle substances and many nerve endings. Four
nerves connect them with the electric lobe in the medulla oblongata.

Skeleton. — The skeleton is cartilaginous with a deposition of
bone in the jaws and vertebral column. The skull of the skate is
not ossified: It consists of a large cartilaginous case with brain
cavity; 2 condyles, 1 large ear capsules, 1 large nasal capsules, a
long rostrum in front and two fontanelles on the roof. The pectoral
girdle is a hoop of cartilage attached dorsally to the crest of the
vertebral plate. The ventral region, the coracoid is separated from

PISCES 231

the dorsal, scapular region, by three facets serving as attachments
for the three basal portions of the pectoral fin, while the supra-
scapula connects the scapula with the crest of the vertebral plate.
The pelvic girdle is not attached to the vertebral column. In the
male the claspers are connected closely with the posterior part of
the hind limb and have a complex cartilaginous skeleton and an
associated gland.

Cavities. — The coelom in the trunk is divided into a pericardial
cavity, lined vf ith. pericardium consisting of coelomic epithelium and
connective tissue, while the abdominal cavity is lined with peri-
toneum. In the dorsal neural cavity is found the central nervous
system.

Digestive System. — The mouth has teeth (special development
of dermal teeth) which are worn away at the outside and renewed
on the inside. A naso-buccal groove connects the nostrils with the
buccal cavity, while the spiracles which communicate with the
buccal cavity ventrally, open dorsally behind the eyes. The tongue
is reduced or almost entirely absent, in skates but is present in
sharks. Salivary glands are lacking, but the short broad esophagus
has mucus glands which lubricate it somewhat. The U-shaped
stomach (see Figure 109) is divided into cardiac and pyloric regions.
The sfnall intestine is extremely short and receives the secretions
from liver and pancreas. The three lobed liver has a large gall
bladder, leading by the bile duct to the small intestine. The
pancreas at the end of the duodenum, has its duct opening opposite
the bile duct. The colon is rather large and has a well developed
spiral valve, in which the mucous layer of the large intestine is so
coiled that it increases surface for absorption and retards the passage

of the food.

The rectal gland, possibly with an excretory function,^ is at the
posterior part of the intestine. The spleen, a ductless gland, dark
red in color, is attached to the stomach by mesentery but has no
digestive significance. It is functional in blood formation.

Respiratory System. — The spiracles open dorsally, each con-
taining a rudimentary gill on the anterior wall supported by a
spiracular cartilage. Water may enter or leave the mouth. The
spiracles serve as intakes for the respiratory stream and also as
spout holes to clear away debris and to keep the eyes clean. ^

2 Crawford, J. 1899. On the rectal gland of the Elas-mobranchs. Proc. Roy.
Soc. Edinburgh, vol. 23, pp. 55-61.

3 Rand, H. W. 1907. Amer. Nat., vol. 41, p. 285.

232

PISCES

In higher vertebrates the spiracle is used in connection with
audition and while other gill clefts disappear entirely, it gives rise
to the tympanic cavity and the Eustachian tube. There are five
pairs of gill pouches, opening internally to the pharynx and externally
by gill slits.

Bile due t — -/- — •

Gall bladder

Liver

■Cordioc stomach

Spiral valve

Rectal gland

Fig. 109. Digestive system of skate. (Drawn by W. J. Moore.)

Water enters the mouth and passes the interior clefts into the
branchial pouches, then outward by the exterior clefts. Gill
pouches are developed from the pharynx and so the respiratory
epithelium is endodermal. Cartilaginous visceral arches alternate
with the gill clefts. A gill consists of two hemibranchs or half gills.
The Dipnoi utilize the gills and the modified swim bladder which
functions as a lung.

Circulatory System. — The heart is four-chambered consisting of
one auricle, one ventricle, with an auriculo-ventricular valve with
two lips, the sinus venosus, situated dorsally and posteriorly and

PISCES

^33

with numerous valves, which lead into tlie auricle, and the conus
arteriosus with six valves, which carries the blood anteriorly from

■Mondfbulor
•Frontat

Spirocular

Bcrsi/or

£Jff'eTna/ cor-of/d
■Inferno/ carotid
— Comrnon carotid
— Superior coronary

Hyo 'dean

•Anterior innominote

Posterior coronary

Ventral aorta

Verfebrol

Posterior innominate

Auric le (ofrium)
■Afferent ttronctiiof
Nutrient arteries fgil/s)

■Efferent brancttio/
ttypotironchia/

Ventricle

Bracftial

■Sob-clovian

Superior mesenteric

Fig. 1 10. Arterial circulation of skate. (Drawn by W. J. Moore.)

the heart to the ventral aorta. (Figure no.) In fishes the heart is
at the anterior end of the coelome. (Figure in.) The walls of
the ventricle are thick and the walls of the auricle are thin. The

234

PISCES

hearts of all fishes except the Dipnoans contain venous blood only.
The ventricle forces the blood through the ventral aorta to the
afferent branchial arteries to the capillaries of the gills, where it
is oxygenated and thence passes into the efferent branchial arteries
and into the dorsal aorta, thence throughout the body.

Juqu/or vein
Inferior Jutjular vein

Veins from abdominal woll-
Cordinal vein — I

Hemorrhoidal vein — -1

Ppigosfric vein —■

Iliohemorriioidal vein-
Posterior anastomosis_
of cardinal vein

Femoral vein~~-^—r —

Bulbus arteriosus

-Con us arteriosus

/Auricle

■Sinus venosus

Ventricle

frecavol sinus

Hepatio sinus
■ Cardinal vein

-Brachial vein

Cardinal sinus
Spermatic sinus

Henal portal veiry

^Factors of renaj portal
vein from pelvic and
lumbar regions

^Branches of renal portal
vein enterincj l^idney

Caudal vein

Fig. III. Venous circulation of skate. (After Parker's Zootomy. Courtesy of Mac-

millan and Co., Ltd.)

The renal portal system is well developed in the Elasmobranchs
but disappears in birds and mammals. In the skate the caudal vein
brings blood from the tail, dividing in the abdominal cavity to form
the right and left renal portal veins, which end in afferent renal veins
supplying the kidneys. The blood leaves the kidneys by the
posterior cardinal veins which enter the cardinal sinus.

The hepatic portal vein is formed by the union of veins that bring
blood from the stomach, intestine, spleen and pancreas. The
large vessel thus formed passes forwards and enters the liver. Leav-

PISCES

^35

ing the liver the blood enters the sinus venosus by two hepatic
sinuses, closely apposed.

Urinogenital System. — The dark red kidneys lie dorsal to the
vertebral column. Several tubes from each kidney combine to
form a ureter. The two ureters open into the urogenital sinus.

— Testis
Epididymis

Fig. 112. Urinogenital system of male skate. (Drawn by W. J. Moore.)

whence the watery products pass out by the cloaca; in the female
they open into little bladders — the dilated ends of the Wolffian
ducts — and thence by a common aperture into the cloaca.

Segmental ducts divide into Wolffian and Miillerian ducts.
The Wolffian duct becomes in the male the vas deferens; in t\icfe7nale
it is an unimportant Wolffian duct; the Miillerian duct becomes in

236

PISCES

the/emale the oviduct, in the male it is a mere rudiment. The body-
cavity rids itself of waste through the abdominal pores. '^

In the male, the anterior portion of the kidney persists as the
epididymis, and its duct becomes the spermiduct. The posterior
portion, the functional kidney, has its own duct, the ureter. In the
female no direct connection exists between the reproductive and
renal organs in the anterior portion. The ureters open in males
into a median chamber — the urino-genital sinus — which also re-

OsNum
— Esophagus

-Oviduct

—Mesonephric duct
-Ovary

-j — S/?e// gland

Uterine portion
of the oviduct

Kidney
^Ureters

Urinary bloddei^
Urinary papilla

Cloaca

Opening of cloaca^
■Abdominal Pore

Fig. 113. Urlnogenital system of female skate. (Drawn by W. J. Moore.)

ceives the spermiducts. This communicates with the cloaca by a
median opening on a papilla — the urino-genital papilla. There is a
median urinary sinus in females. The ureters open into the sinus
or directly into the cloaca. The testes are fastened by a fold of
peritoneum on each side of the cardinal sinus. (Figure 112.)
Spermatozoa pass from the testes by the vasa efferentia into a tube

* Smith et al. have shown that the perivisceral fluid escapes through the abdominal
pores. They also emphasize the secretory capacity of the pericardium and peritoneum
in Elasmobranchii. (Smith, H., 1929, J. Biol. Chem., vol. 81, no. 2.)

PISCES

237

surrounded anteriorly by the epididymis. The tube of the epi-
didymis is continued into the vas deferens which is dilated posteriorly
into the seminal vesicle and adjacent sperm sac. The vasa. de-
ferentia open into the urogenital sinus. Sperms pass along the
groove between the claspers of the male.

The ovaries are anchored by peritoneum on each side of the
cardinal sinus. The eggs escape into the
body cavity, and enter the single anterior
aperture of the two oviducts. (Figure 1 13.)
The lower portions of the oviducts open
into the cloaca. Many of the dog fishes
and sharks are viviparous^ while the skate
is oviparous^ with a horny purse (Figure
114) secreted by its oviducal or "shell"
glands.

Nervous System. — The brain consists
of the fused cerebral hemispheres with a
nervous roof, the optic thalamus or thala-
mencephalon, with dorsal pineal body, and
ventral pituitary body and thinly roofed
third ventricle within; the mid-brain with
paired optic lobes above, the crura-cerebri
below, the Aqueduct of Sylvius or iier
passing below; the cerebellum with its
anterior and posterior lobes both marked
by ridges and grooves; and the medulla
oblongata which has a thin vascular roof,
and lateral restiform bodies. There are
ten pairs of cerebral nerves, and many
paired spinal nerves.^ (Figure 115, Fig-
ure 116.)

Sense Organs. — In the Elasmobranch Fig. 114. Egg case of a
eye, there is no focusing device. The shape skate. (Drawn by Norris
of the eye and the density of the vitreous Jones.)
humor aid in keeping the spherical lens close

to the pupillary opening of the iris. The ears are sacs with three
pairs of semicircular canals. Within the vestibule are calcareous

6 Norris, H. W., and Hughes, S. P. The cranial, occipital and anterior spinal
nerves of the dogfish, Squalus acanthias. Jour. Comp. Neurol., vol. 31, no. 5, pp.

293-395-

238

1

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PISCES

-H

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.0

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PISCES 239

otolithic particles surrounded by a jelly. The nasal sacs are cup-
like cavities with plaited cells. They serve for sinell only. The
sensory tubes are best seen on the ventral surface, where they lie
just under the skin. At their internal ends lie ampullae, con-
taining sensory cells. At their outer ends there are pores. It is

r — No sat capsule
j^-Olfacfory bulb

Olfactory ^folk

Olfactory lobe

Cerebrurn

■ Tfialamencepbaton

^—•f Opffc nerve

• Optic chioa/na
•Opfic tracf
-Inferior fobe
-Pituitary

-Oculomotor nerve

• Trochlear nerve

-ffesfiform body

^^^/ - TriqemirtQl nerve

-S^m^ -^ Abducens nerve

•■Facial nerve

•Auditory nerve

tvledulla oblon<jafa

Closso pfiarync^eal nerve*

Spinal cord

— Pneumo<jastric nerve

Fig. 116. Ventral view of dogfish brain, showing cerebral nerves. (Drawn by W. J.

Moore.)

probable that they are organs partly of touch and partly of
" chemical sense." The lateral line organs detect vibrations of low
frequency. The ear, the lateral line, and a pre-auditory sensory
patch are developed from a thickening of the ectoderm. The
ectodermal rudiments of the otocyst and the lateral line are in some
cases continuous at first. Sensory cells in the canals closely
resemble the sensory cells of the ear. (See p. 259.)

240

PISCES

Subclass Teleostomi. Order 1. Crossopterygii. {Long-finned
Ganoids.) — Polypterus bichir {Senegalus) (Figure 117) lives in the
deeper waters of the Nile (Harrington), but does not bury itself in
the mud like true mudfishes. The air bladder is an accessory-
respiratory organ. It is connected by a primitive trachea with the
pharynx and used as a lung. The larva of Polypterus resembles
amphibian larvae. It has external gills, and utilizes its pectoral

Fig. 117. Polypterus bichir. Ganoid. /, full length lateral view of 44 cm.
Polypterus bichir. X i. la, dorsal view of mid-dorsal line of same. X i. /^,
lateral view of anterior portion of trunk of same, with pectoral fin removed. X i.
ic, ventral view of anal fins of same. X i. (Courtesy of Amer. Mus. of Nat. Hist.)

appendages as supports. The median fin is primitive like that of
the tadpole, but differs in that it has cartilaginous supports or rays.

Calaniichthys., the other genus of Crossopterygii, has an eel-like
shape, and lives in small muddy streams in middle western Africa,
feeding mainly on Crustacea. The Paleozoic Crossopterygii are
regarded as probable ancestors of the terrestrial vertebrates and the
present day fishes.

Order 2. Chondrostei. — This order has a skeleton largely
cartilaginous, with ganoid scales and a heterocercal tail.

The paddlefish or spoon-bill {Poly don) lives in the Mississippi
River and its tributaries. . It may reach a length of six feet and
weight of one hundred fifty pounds. It is sluggish, feeding on
mud, shoveled up with its spoon-bill snout, which is equipped with

PISCES

241

Fig. 118. Short-nosed sturgeon. (Nichols
and Breder. N. Y. Zool. Soc.)

many tactile and gustatory end organs. A relative of the American
spoon-bill lives in the waters of China.

The sturgeon {Acipenser) (Figure 118) has its rostrum prolonged
into a snout with a transverse row of barbels hanging from the
ventral surface. The scales
are large and arranged in five
longitudinal rows, and have
keels. The sturgeons are
found in the Great Lakes,
and in the Black and Caspian

seas. Caviar, is made from the eggs of sturgeons, and their flesh
is also eaten. They reach a size of thirty-two hundred pounds.

Order 3. Holostei. — Holostei are between the Elasmobranchs
and the Teleosts, and include Amia and Lepidosteus. They have
the cartilaginous and bony skeleton, ganoid scales, swim bladder
and pyloric appendages of the teleosts; and the conus arteriosus and
spiral valve of the elasmobranchs. The tail is diphycercal. (See p.

The gar pikes {Lepidosteus) are fresh water fishes, ranging from
five to ten feet (Alligator gar), and found in North and Central
America. They have long slender bony snouts with sharp teeth,
and kill many other fishes. The air bladder serves as a lung when
the animal comes to the surface to gulp in a fresh supply of air.
(Figure 119.)

Fig. 119. Long-nosed gar. (Courtesy of N. Y. Zool. Soc.)

The bow fin, Amia calva, called the " mudfish " or " fresh water
dog fish," resembles the true bony fishes. It has, however, a
continuous dorsal fin, heavy ganoin covered scales and a tail modi-
fied from the heterocercal to a shape almost homocercal. The air

242

PISCES

bladder is used as a lung. The male guards the nest and later takes
care of the young for a short time. The embryonic development is
less like that of a teleost than of an amphibian. (Figure 120.)

Order 4. Teleostei. (Gr. — complete, — a bone.) — The teleosts
include most of our common food fishes. The skeleton is ossified.
Except for one genus, the spiral valve is absent. The stomach has

Fig. 120. Bowfin, Jmia caha. (From L. A. Fuertes. Courtesy of Slingerland-

Comstock Publishing Co.)

pyloric appendages (120 in the cod). The scales are cycloid or
ctenoid. The gills are comblike and an operculum is always present.
The swim bladder is usually present though its duct is not always
open. The eyes are large and lidless. The optic nerves of Teleostei
cross each other, without interlacing.

^ The Akaj'inp tarp 0 n {Elopidae), (Figure 121) called the " silver
king," is much sought by fishermen as it is a gamey fighter. Its

Fig. 121. Tarpon. (From Goode. U. S. B. F.)

large silvery scales furnish ganoin for the manufacture of ornaments.

The salmon {^Salmonidae) is a marine fish spawning in fresh
water at the age of four or five years. Its long migration to an-
cestral spawning grounds has puzzled and thrilled scientists for
many years. (See page 263.)

The white fish lives in deep water in the winter and migrates to

PISCES

243

the shallows to feed and to spawn. It ranges in weight from three to
twenty pounds. The lake trout ranges from a few pounds to over
one hundred pounds in weight. The red spotted brook trout (speckled
trout) is a shy fish inhabiting clear cold streams and is much sought
after by fishermen. (Figure 122.)

Fig. 122. A, lake trout. 5, brook trout. (From L. A. Fuertes. Courtesy of

Slingerland-Comstock Publishing Co.)

The bullheads and catfishes {Siluridae) are for the most part fresh
water fishes. The Mississippi catfish grows to a length of six feet
and may weigh one hundred pounds. (Figure 123.)

The saw-toothed piranha is one of the most savage of fishes and
although it seldom reaches a length of one foot is feared by man and
attacks fishes and even alligators. Travellers find that the piranha
will seize one's fingers, trailing over the side of a boat. In catching
piranhas, copper wire, three strands thick, is used to attach the hook.

The barracuda of the Eastern coast which sometimes reaches a
length of six feet, is an important enemy of crustaceans, fish and
aquatic mammals. It is reputed to attack man, but most of the
cases reported proved to be the bites of tropical sharks.

244

PISCES

The chubs, horned dace and carp belong to the family Cyprinidae.
The German carp is a fish introduced to America in 1872, and now
plentiful. It is not well flavored and is probably injurious to other
fishes, as well as active in keeping down vegetation ordinarily fed
upon by ducks. Gold-fish, Cyprinida, bred for centuries by the
Japanese, have been developed into beautiful forms.

Fig. 123. Bull head.

(From L. A. Fuertes. Courtesy of Slingerland-Comstock
Publishing Co.)

The suckers {Castastomidae) are fresh-water fishes with long
protractile mouths. Mullets are relatives.

The common herring {Clupeidae) is said to be one of the most
important food fishes. Slight differences in temperature have a
great influence on the appearance of the shoals of these fish along
our coast.

There are six species of cave-fishes {Amblyopsidae) in the sub-
terranean streams of Missouri, Kentucky and Indiana. They have
been studied most by Dr. Eigenmann of Indiana University. The
eyes are reduced. Loeb has found that some fish eggs develop
without eyes if kept in the dark (Neo-Lamarckism, page 514).

Fig. 124. Atlantic flying fish. (From Nichols and Breder.)

T\iQ. flying fishes {Exocoeiidae) (Figure 124) have the power to
plane along above the surface of the water. As in other fishes the
tail gives a great initial impetus. It is said that they can " fly "
two hundred yards.

PISCES

245

The true eels {Anguillidae) are found in fresh and salt water.
They migrate upstream to the headwaters of fresh water rivers and
live there until at maturity they pass down to the sea to spawn.
It is only recently that their habits became fully known. (See page
264.)

Fig. 125. A, pike. B, pickerel. C, muskellunge. (Courtesy of Slingerland-Com-

stock Publishing Co.)

The pikes {Esocidae) (Figure 125, A^ B, C) include the pickerel,
Esox lucius, which is a serious enemy of other more important
food fishes, and also captures frogs and small birds. The muskel-
lunge {Esox masquinongy) is a hard fighting food fish reaching a
weight of one hundred pounds and a length of six feet.

The mummichogs {Poecilidae) include the salt water minnow,
Fu7idulus hetej-oclitus, which is not only extremely valuable in
mosquito extermination on the northern salt marshes of the U. S.,
but is of great use in experimental embryology. (Figure 126, A
and B.)

The top minnow {Gambusia affinis) is of great Importance in
the extermination of the larvae of Anopheline mosquitoes. They

246

PISCES

have been utilized in the southern part of the U. S. and, shipped to
other countries, have successfully attacked the mosquito larvae
there. Top-minnows must be renewed in many places where winter
floods carry them away.

E-Mevirhot

Fig. 126. J, Fundulus heterocUtus , male. B, Fundulus heteroclitus, female. (F. E.
Chidester, Bull. 300, N. J. Exp. Sta., 191 6.)

The sticklebacks {Gasterosteidae) are interesting because of the
nest building of the male. He entices the female to the nest and
after she has spawned, he fertilizes the eggs and guards the nest.
(Figure 127.)

Fig. 127. Two-spined stickleback. (From Nichols and Breder.)

Both the pipe fish and the sea horse {Syngnathidae) are peculiar
in that the male carries the eggs in a ventral brood pouch. (Figure
128.) Jordan states that the female deposits the eggs on the bottom
of the sea and that the male transfers them to his brood pouch.
The sea horse is the only fish with a prehensile tail.

PISCES

247

The sea basses {Setranidae) are mostly marine. The striped
bass and the black sea-bass are the most prized by fishermen. The
latter is said to reach a weight of 300 lbs.

A small fish {Rhodeus amarus) lives in the embryonic state in the
gill cavities of the mussel ( Unto).
Thus a fresh-water mussel may
send out glochidia that attach to
an adult fish, which at the same
time sends its embryos to be shel-
tered by the mussel.

The smallest fish in the world
is the Philippine goby {Pandaka
pygmaea), which is but five-six-
teenths of an inch long when full
grown. A slightly larger goby
{Mistichthys luzonensis) is also
found in Luzon, P. I.

The perches {Percidae) include
the little used yellow perch and
the pike perch. The latter is con-
sidered a valuable species and
propagated by the U. S. Bureau of
Fisheries.

The small-mouthed black bass Evolution^ after Doflein, (Courtesy of
( Centrarchidae) is extremely gamy. The Macmillan Co.)
The common sunfish or ^^ pumpkin

seed " is not to be confused with the Hawaiian " sun fish." (Figure
129, J and B.)

The porcupine fishes {Diodontidae) are armed with movable
spines and when alarmed puff their bodies full of air, and float belly
upward. (Figure 130.)

The head fish, or " sunfish " of Hawaii, is an odd appearing fish
(Figure 131), with a skeleton largely cartilaginous and with heavy
armor. The smooth skin is extremely thick. The body looks as
though it extended but a short distance beyond the head and lacked
a tail entirely. Some specimens are said to have reached a weight
of 2,000 lbs. (Zane Grey's record fish) and a diameter of 8 feet.

The shark-suckers, or remoras {Echeneididae) (Figure 132), are
equipped with a modified anterior dorsal fin resembling a rubber
boot sole. It acts as a sucking disk, enabling the animals to attach

Fig. 128. Seahorse, male, with
abdominal pouch. From Lull, Organic

Fig. 129. ^, large mouth black bass. 5, long-eared sunfish. (Courtesy of Slinger-

land-Comstock Publishing Co.)

■

1

^^1

^^^^T^??^

^^^K^^^

V

^^^^Hk#^^

IE

gQ

Fig. 130. Puffer fish. (Courtesy of Amer. Mus. of Nat. Hist.)

PISCES

249

themselves to sharks and other marine forms. The remoras have
been used by natives in capturing other fish (Gudger). The goose
fishy or angler {Lophiidae), is a fish with an enormous mouth and a
modified first dorsal ray which it uses as a lure. The common
mackerel^ the Spanish mackerel, and the tuna (called " horse-
mackerel ") are examples of the family Scombridae. The tuna is
large, sometimes weighing 150 lbs.

Fig. 131. Head fish, Mola mola. (Courtesy of Amer. Mus. of Nat. Hist.)

T\\efla fishes {Pleuronectidae) include the smaller species and the
large halibut {holibui). The lateral eye of one side moves over to
the other and the fish lies on its side. Flounders are well pigmented
and have been utilized in experiments by Sumner and Mast who
showed that color change will assume the character of the back-
ground-checkerboard, etc., if the eyes are intact. Blinded, the fish
cannot change color, to match its environment. (Figure 133.)

The upper jaw of the swordfish {Xiphiidae) (Figure 134) is
extended into a formidable weapon. Instances are recorded in
which a large swordfish (500 lbs.) has penetrated the bottom of a

250

PISCES

heavy whaleboat. The swordfish is one of the finest of the food-
fishes, but utilized in New England chiefly. The sailfish is another
odd type.

The cod, the haddock, and the hake are all important members of
the family Gadidae. The cod is now especially valuable as a source
of cod liver oil. This oil has been used as a remedy for growth
deficiencies for many years, but recently its importance has been
much emphasized by the " vitamin " enthusiasts. (Figure 135.)

Fig. 132. Shark suckers. (Courtesy of Amer. Mus. of Nat. Hist.)

Subclass Dipnoi. (Gr., " two breathing apertures.") — The Imig
fishes have a heart with the beginnings of a division into two auricles.
Gill respiration is combined with the use of a modified swim bladder
which acts as a lung. A posterior naris opens into the mouth cavity.
They have paired fins and persistent notochord. The Australian
lung-fish ( Neoceratodus fosteri) feeds on worms, crustaceans and
mollusks secured from the bottom vegetation. Its single lung is
utilized when it comes to the surface. It can survive in stagnant
and polluted water where other fishes perish. (Figure 137.)

^^2aa^

Fig. 133. A, common mackerel. B, bonito. C, Spanish mackerel. D, halibut.
(From Nichols and Breder. Courtesy of N. Y. Zool. Soc.)

Fig. 134. Sailfish. Istiophorus gladius. (Courtesy of American Museum of Natural

History.)

Fig. 135. A, cod. (From U. S. B. F. Manual.) B, pollock. C, haddock. Nichols
and Breder. (Courtesy of N. Y. Zool. Soc.)

252

PISCES

The African lung-fishes {Pj-otopterus) feed on worms, crustaceans,
frogs and insects. They burrow into the mud, secreting a cocoon of

Anieniof dorsa/ f/'n ri./f '

PectorsJ fin-^

Nostri/s,

'Poster/or donsa/ fin

?' r^i/fin

JS'c/e'

A (Ji// coven' ^ ^^^^'-Pe/v/c fin j^ T

*- -Ifead A Trunk ^ Ta// -^

K. S- FLSM CoMttlNMnv V.

Fig. 136. Yellow perch indexed. (Courtesy of Amer. Mus. of Nat. Hist.)

slime, and aestivate during the dry season. A slimy covering en-
closes the animal except for a small aperture through which lung
breathing is carried on.

Fig. 137. Australian lung fish, Ceratodus. (Courtesy of Amer. Mus. of Nat. Hist.)

The South American lungfish {Lepidosiren) is a trifle more
terrestrial than Protopterus and lives in a deep burrow in the swamp,
laying eggs in the soil. It takes several gulps of air at a time when
it comes to the surface of the water.

PISCES ^^2

General Consideration of the Fishes

Locomotion in fishes may be by: Swimming, leaping from the
water, crawHng or hopping about with the pectoral fins (Angler
fish and E. Indian Goby); planing on extended pectoral fins (flying
fishes); or wriggling after rains from one stream or pond to another
(eel).

Coloration. — The coloration of fishes is due to the presence In the
dermic portion of the skin of (a) special pigment containing cells
(chromatophores), (-^) a peculiar reflecting tissue composed of
iridocytes. Coloration varies with the species of fishes and may
vary in the same fish according to background, age, ill-health, and
emotions.

Sound Producing Organs. — (a) Stridulation. — The bull head uses
its preoperculum for stridulation while the gurnard uses its hyoman-
dibular bone. In the drumming fish, the postclavicles stridulate
with a grooved area on each cleithrum and the air bladder takes up
the vibrations. Friction of the upper and lower teeth causes a
grinding noise in the mackerel. The sunfish makes sounds like
those of pigs grinding their teeth.

{b) Expulsion of the air from the swim bladder and mouth
produces quite noticeable sounds in the eel, the carp and the loach.
The eel is said to produce a single note, more musical than any
uttered by other fishes. The air-bladder and its muscles in the
drum-fish {Poganias chromis) constitute the most powerful sound
producing apparatus in fishes.

Respiration. — The rate of breathing varies with the species, the
minnow and the stickleback breathing 150 times per minute, while
the blue wrass and the rockling have a respiratory rate of fifteen
per minute. Skin respiration, vascular caudal fins and larval
external gills are important, while some fishes use the air bladder or
develop special accessory organs for aquatic or aerial respiration.
Many fishes rise to the surface and swallow the air. The air bladder
is used for respiration In the ganoids and many teleosts, and in the
" lung fishes."

Skin. — P/acoid sc3.\es are found in the Elasmobranchs, and while
they are usually closely set, we find that in the skate they are scat-
tered. In sharks one can trace the evolution of placold scales Into

ieefh.

Ganoid scales are hard plates forming an armor in such forms as

254

PISCES

the gar-pike. The outer surface " ganoin " is extremely hard and
smooth and readily polished. (Figure 138.)

Teleostean fishes have two types of scales, cycloid and ctenoid.
Cycloid scales are circular in shape and overlap. Ctenoid scales are
rounded but have a serrated comb-like edge that makes them firmer
in position. Flounders have ctenoid scales on the upper side and
cycloid scales on the under side. The pipe-fish and the sea horse

have scales fused into a
bony armor. Embryonic
eels have scales, but in
adults it is impossible to
see even traces of them
with the naked eye.

In some elasmo-
branchs and t e 1 e o s t s
from the depths of the
ocean we find epidermal
organs modified from
glands into luminous
organs or "photophores."
Some fishes like shad,
herring, and menhaden
have in the tela subcu-
tanea, crystals of guanin,
which form the base of
Ctenoid; 3, ganoid; 4, placoid. (From Hertwig- pearl essence. (See page
Kingsley. Courtesy of Henry Holt & Co.) 1 57-)

Fish have chromato-
phores (melanophores) and change color to match their background,
but when blinded the color changing stops.

Poison Glands. — When the poisonous secretion produced by
glands at the bases oi dogfish spines is injected into the lateral line of
a fish, respiration is accelerated and the animal soon becomes
lethargic. Eagle rays and sting rays, have barbed serrated spines
at the base of the tail and the glandular secretion accompanying a
blow from the tail, undoubtedly adds to the effects produced by the
irritation. Several teleostean fish including the catfish, have poison
glands associated with spines on the dorsal fins or in the axillary
region.

Blood. — In fishes the blood consists of a nutritive ^\nd, plasjna^

Fig. 138^. Scales of fishes. /, cycloid; 2,

PISCES

^SS

in which float red corpuscles and white corpuscles. In the Cyclo-
stomata (Petromyzon) the red corpuscles are circular, but in the
true fishes they are usually biconvex, flat, oval, nucleated and with
hemoglobin, and rich in iron. In the Dipnoi (lung fishes) the red

£^S^jU*i^^

Fig. 1385. Types of tails of fishes. J, diphycercal fin of Polyptertis bichir.
(Vertebral column and notochord divide the tail into symmetrical dorsal and ventral
portions.) 5, heterocercal tail of the sturgeon. (As a result of an upward bending
of the notochord and vertebral column the fin has become asymmetrical, the ventral
portion much larger than the dorsal.) C, D, homocercal fins, C, of Amia caka; D, of
Trutta salar. (By a still greater upward bending of the notochord and vertebral
column the dorsal portion has almost entirely disappeared and the ventral portion
almost alone forms the fin, externally apparently symmetrical, but in its internal
structure very asymmetrical.) ch, chorda; a, b, c, cover-plates. (From Hertwig-
Kingsley. Courtesy of Henry Holt & Co.)

corpuscles are larger than in most animals (40 mu-mu in diameter)
being exceeded in size only by the Urodele Amphibians. Leucocytes
are not plentiful in most fishes, but are more numerous in the
Dipnoi than in other vertebrates.

Digestive System. — In the large intestine of the Elasj72obra7ichti
there is a spiral valve, lacking in the Teleosteii. The small intestine

256

PISCES

is very short, but receives the secretions from well-developed liver
and pancreas.

In the Teleosteii, the teeth are premaxillary, vomerine, superior
pharyngeal, inferior pharyngeal, and mandibular. There are no
salivary glands, no spiracles and no posterior nares. The pharynx
is equipped with a fringe of gill rakers (strainers). The small non-
muscular tongue is supported by the ventral part of the hyoid arch.

||gg||I^-- Top-pL

Co/, epi ,

'^^T^.. Oobl. ce/f

3as. mem.

Fig. 139. A highly magnified view of a portion of the intestinal epithelium of the
sea bass, showing several columnar cells and a large goblet cell. The striated 'top-
plate' is evident, interrupted at the mouth of the goblet cell. Bas.mem., basement
membrane; CoLepi., columnar epithelium; Gobl.cell, goblet cell; Top-pl., top-plate.
(Courtesy of I. H. Blake, 7- Morph., vol. 50, Sept. 1930.)

The gullet is broad and short, and the stomachy curved, is divided
into cardiac and pyloric regions with pyloric <r^f^^ ranging from six
in the perch to one hundred and twenty in the cod, and secreting
pancreatic enzymes. The pancreas is absent, but in a few teleosts,
pancreatic tissue is combined with the liver. In the goosefish,
and many other teleosts there are isolated Islands of Langerhans
in the mesentery that furnish the requisite " insulin." The Toronto
investigators have extracted it from fishes, and treated diabetes
successfully.

PISCES

m

All the Cyprinidae lack peptic glands. Babkin and Bowie ^ have
shown that Fundulus heteroclitus has no stomach, that pepsin and
HCl are absent and that every phase of digestion takes place in an
alkaline medium.

Fig. 1 40. Scorpaenoid fish. (Courtesy of Amer. Mus. of Nat. Hist.)

Ljonph. — Fishes have small vessels (the lymph capillaries),
lymph spaces, and lymph sinuses. In the eel a lymph heart in the
tail communicates with the smaller of the two caudal veins and
rhythmically pumps lymph into the vein. Lymph consists of
plasma minus red corpuscles, but normally rich in the white corpus-
cles with large nuclei called lymphocytes.

Endocrine Glands. — The thyroid gland in the Elasmobranchs is a
large compact organ near the anterior end of the ventral aorta.
In the Teleostomi it is sometimes paired or as in the perch consists
of diffuse masses of reddish lobules scattered along the afferent
branchial artery. The thymus gland of the embryo Elasmobranchs
and Teleosts has a multiple origin, arising from a series of epithelial
thickenings, one of which is developed at the dorsal extremity of
each of the gill clefts except the spiracle. The rudiments invaginate
and fuse. The thymus of the adult Elasmobranchs is paired, the
organ lying just above the branchial arches. In the Teleostomi, the
thymus is found at the dorsal extremity of the last branchial arch
near the mucous membrane of the branchial cavity. The pancreas
is represented in teleosts by the pyloric appendages, while isolated

« Babkin, B. P., and Bowie, D. J. 1908. The digestive system and its function
in Fundulus heteroclitus. Biol. Bull., vol. 54, no. 3, pp. 254-277.

258

PISCES

Islands of Langerhans in the mesentery furnish insulin. (See p.
156.)

Elasmobranchs have two structures, the paired suprarenals and
interrenals. The suprarenals are segmentally arranged bodies
situated in pairs on the segmented arteries given off from the dorsal
aorta. The first pair are called axillary hearts. The interrenal is a
thin, elongated, yellow body with one or two anterior lobes. It
extends in the median line between the two kidneys or occupies the
internal portion of the ventral surface of each kidney. In Teleosts
the suprarenals, varying from two to five in number, are frequently
found embedded in the kidneys.

Lymphoid Tissue. — Ordinary lymphatic glands are absent in
fishes and it is probable that functional lymphoid tissue abounds
to compensate. The large anterior portion of the mesonephros in
the Teleostomi, called the head kidney, is almost entirely replaced by
lyjnphoid tissue, practically no renal structure remaining. It is
concluded, from the presence of free red corpuscles and oxyhemo-
globin, that the head kidney performs a blood destroying function.
The spleen, of course, forms leucocytes and also destroys blood
corpuscles, devouring worn out reds. Possibly the head kidney
performs a similar double service.

Fig. 141. Four-eyed fish, Anableps dovii. (Courtesy of Amer. Mus. of Nat. Hist.)

Senses. — Fishes vary greatly in their use of the senses. Some
are predominantly olfactory or gustatory while others depend
largely upon vision to direct their movements. In all, the tempera-
ture sense ^ and lateral line sense are of paramount importance.

Olfaction, Gustation. ( Chemical Sense.) ^ — Fish have a chemical
sense dependent on free nerve endings; smell, dependent on a highly
developed distance receptor, the olfactory nerve; and taste, which

^ Chidester, F. E. 1924. A critical examination of the evidence for physical
and chemical influences on fish migration. Brit. Jour. Exp. Biol., vol. 1, pp. 79-118.

* Parker, G.H. 1922, Smell, Taste and Allied Senses in the Vertebrates. J. B.
Lippincott, Philadelphia, Pa.

PISCES 259

is dependent on the taste buds. Fish are extremely sensitive to
variations in acidity and alkalinity in the water.

Vision. — Fish are able to change color, adapting themselves to
the background. When blinded, they are unable to thus adapt
themselves. Experiments of Lyon showed that fish see the banks of
streams, and will react to currents of water even if not directly in
contact with them.

Tactile and Kinesthetic Senses. — Currents and surface waves are
apprehended by fish through the general cutaneous nerves for touch.
In general, fish react to stream pressure, aligning their bodies to
face the current.

Lateral Line. — Parker holds that the lateral line nerves serve in
an auxiliary capacity aiding the general cutaneous nerves in rheo-
tropic responses. Lateral line organs are stimulated by vibrations
of low frequency, about six per second. Parker concludes that
lateral line organs are intermediate in function between the organs
of touch and the ear^ the latter being sensitive to vibrations of high
frequency.

Hearing. — The surface between the air and the water is a screen
through which little sound passes. Vibrations of the water induced
by foot-falls on the bank are not to be confused with stimuli affecting
the sacculus, which Parker believes to be the chief organ of hearing.
During the recent war Parker, experimenting with cannon fired
near the surface of the water, found that fish were driven away
by the concussion. As vibrations of the air were transmitted to
the water it is difficult to believe that true hearing was evidenced.

Messmates and Associates. — The small horse mackerels
( Carangidae) swim in the shelter of large jelly fishes. A small fish
{Amphiprion) lives inside the large sea anemone {Crambactis) .
Fierasfery a small fish, lives in the hind-gut of the sea cucumber.
Another form lives in the mantle cavity of the large sea snail,
Strombus gigcis.

Parental Care. — One of the most remarkable instances of paren-
tal care by the male is that seen in the sea horse and the pipe fish,
where the eggs are carried in a ventral brood pouch by the male.
The males of sticklebacks and lump-suckers guard their nests for
weeks. The butterfish {Pholis gunnellus) coils around its eggs and
guards them.

Habitat. — The trout lives in water ranging from 20° C. to 1° C.
and spawns in October. The common eel of Europe ranges from

iGo PISCES

Iceland to the Nile. In studying the fishes of the New Jersey salt
marshes during the winter the author found that small miyinows dug
from their burrows and brought into the laboratory in stiff, immobile
condition would revive in a short time.

Britton ^ studied the freezing, overwarming and resuscitation of
the eel, skate, flounder and cod. When the temperature exceeded
30° C, or went below — 1° C. the fish became immobile and finally
the heart stopped beating. Resuscitation was readily effected in
many cases by transferring the fish to water of the normal tempera-
ture, about 16° C. In one case a skate, Raia laevis, was exposed for
" sixteen hours in a refrigerator to a temperature as low as — 20° C,
the whole of the fish being solidly frozen," and on gradual thawing
the heart beat returned to a slow regular thythm, but the animal
did not fully recover. At the lower temperatures, 6° C. to 10° C,
the respiratory action was almost coincident with heart beat.

Reaction to Temperature Change. — One of the greatest factors
in the behavior of fishes is their response to temperature change.
We find that, by means of heat and cold corpuscles in the skin^ fish
proceed towards warmer or cooler water, and that it is the relative
temperature that determines their activity. Herring are sensitive
to very slight temperature changes, according to Shelford and
Powers (191 5), reacting to differences as small as 0.2° C. It has
been shown that temperature changes influence the reactions of
fishes to lights salinity^ Ph and to internal factors such as the de-
veloping gonads. Unquestionably this sense is the greatest single
factor that we find influencing the metabolism and behavior of
fishes. It must even be considered in connection with the instincts
of the species.

Electric Organs. — In the Elasmobranchs we find electric organs
present in the torpedo ray. The electric eel is a Teleost with the
power to shock the unwary. With but one exception, electric
organs are composed of metamorphosed muscles and retain their
original nerve endings.

Phosphorescent Organs. — The highest development of piscine
phosphorescent organs is in fishes inhabiting the depths of the sea.
A luminous organ in the fish is a collection of gland cells usually
forming the lining of a series of radially arranged tubules in the
deeper portion of the organ. The luminous organ contains ganglion

' Britton, S. W. 1924. The effects of extreme temperatures on fishes. Am. Jour,
of Physiol., vol. 67, no. 2, pp. 411-421.

PISCES 261

cells and nerves joining either a spinal or cerebral nerve. Phos-
phorescent organs are used to see prey, to dazzle and frighten
enemies and as recognition lights.

Harvey ^° has studied luminescence in two species of fish {Photo-
blepharon and Anomalops). In these forms the luminescent organs
consist of a large number of sets of parallel gland tubes. The
lumina of the tubes are filled with an emulsion containing granular
and rodshaped bacteria living in sy?nbiotic relation.

Adaptation of Fishes to Their Environment. — Fishes have their
head, body and tail compressed into a curved spindle form which
offers little resistance to the water. They have a well-developed
caudal fin used for propulsion; paired pectoral and pelvic ^^^zj- are
important in executing lateral movements, while their dorsal and
ventral fins aid in preserving an even keel. Fishes swim, leap, flop
and plane. The climbing perch moves up tree trunks by small
hooks on its pectoral fins. The sea robin uses its pectoral fins in
progressing over the sandy bottom. The mucus secreted by the
glands of the skin and the fact that the scales overlap, tend to reduce
friction in swimming. In many forms the swim bladder furnishes a
means of varying the specific gravity so that the animal can rise or
sink in the water. Some fishes are provided with sharp spines and
poison glands for offense and defense. Well-developed organs of
vision, olfaction and the lateral line sense enable fishes to locate
food or warn them of danger.

Economic Importance of Fishes and Their Relatives

Positive. — Cyclostomes were formerly used as food.

Elasmobranchs. — Dogfish, sharks and skates are eaten fresh and
canned. Shark leather, formerly used for " shagreen " spectacle
cases, and also for polishing wood and other materials, has recently
been advertised widely by the United States Bureau of Fisheries for
use in making shoes, handbags and pocketbooks. Attempts have
also been made to utilize other elasmobranch skins. Shark fins
have been used as gelatin In China and India. Sharks are also used
as fertilizer. Shark liver oil has been used as a substitute for cod
liver oil. A basking shark may produce over a ton of oil. Dogfish
oil is now purified and used as an insect repellant. The odor is not
obnoxious to man.

10 Harvey, E. N. 1920. The Nature of Animal Light. J. B. Lippincott Co.,
Philadelphia.

262 PISCES

Teleosts. — Many species of the bony fishes are valued as food.
Some of the common food fishes are herring, shad, codfish and sal-
mon. Fish are eaten fresh, smoked, dried, salted, canned whole, or
flaked, and pickled. Cod, halibut and salmon skins have been
suggested as a source of leather, but are not in use by civilized man.
The Alaskan Indians have for many years used salmon skins to
make shirts and boots. Eel leather has been utilized for pig-tails
and flail thongs. Some Southern negroes value eel skins as a cure
for rheumatism. The swim-bladder of the sturgeon and some other
fish is used to make isinglass and fish-glue. Menhaden are caught
by the ton and made into oil and fertilizer.

Pearl essence is secured from herring, alewives, shad and men-
haden. The California sardine is also a source. Pearl essence is
securedr-b^y the extraction of the blade-like crystals oi guanin found
in the epidermis of the fish. The crystals are separated into uniform
sizes and when mixed with gelatin are used to coat glass beads,
making imitation pearls. A solution of guanin is also prepared for
use as nail-gloss.

Fish meal is secured from fish and fish waste by cooking without
scorching, and pressing the oil out while the fish is hot. Fish meal
is used in poultry and stock feed.

While it will probably never replace cod liver oil, in furnishing
Vitamins A and D for human consumption, there is no question
that the vast quantities of salmon liver oil will reduce prices for the
cheaper grades of fish oil used in cattle feeding.

Negative. Cyclostomes. — Lampreys attach themselves to the
bodies of other fish, cut through the body wall and suck out the
blood and soft parts until the victim dies. Hags parasitize marine
fishes, entering the body cavity of the host through the hole that
they cut.

Elasmobranchs. — The great white shark called the " maneater "
sometimes reaches a length of forty feet and can cut the body of a
man in two at one bite. Small dogfish destroy lobsters, crabs, and
food fishes, and injure nets and other fishing gear to the extent of
1500,000 per year in Massachusetts. Sting-rays or " stingarees "
occasionally injure man. Rays and some sharks have poison glands
at the base of their dorsal fins. The torpedo or electric ray is able
to give a shock of fifteen volts and temporarily disable a man.

Teleosts. — Certain of the bony fishes are enemies of man. The
barracuda, sometimes reaching a length of six feet, is reputed to

PISCES 263

attack man. Its flesh, while said to be poisonous, is probably never
injurious unless ptomaines have been allowed to develop. (See
page 243.) The saw-toothed piranha has powerful teeth and oc-
casionally attacks bathers. It is said not to fear the alligator.
Some of the catfishes have poison glands at the bases of their spines.

Migration in Fishes. — Fishes apparently seek waters of a certain
temperature or acidity or salinity which are the optimum for their
developing eggs and furnish food for themselves and fry. Certain
races frequent the same streams year after year unless driven away.

The fresh water fishes in many cases (trout) travel from the
larger rivers to brooks, where the temperature is cooler, to spawn.
Suckers have an annual migration very early in the spring.

Salmon, shad, and sturgeons leave the salt water for fresh water
to spawn, but spend their life to maturity in feeding in the salt
water and migrating only from the deep to the shallow, more brack-
ish water inshore. When they ascend rivers salmon sometimes trav-
el over 2,000 miles to spawn. Apparently the young salmon return
to their ancestral spawning grounds whenever possible. Extensive
scale studies and tagging experiments of American and European in-
vestigators have proved that many individuals return after two or
three years to the very region whence they came as newly hatched
fish. King salmon have averaged forty-two miles a day for a
journey of 1,500 miles. In the case of the anadramous (up running)
fishes such as the salmon, it is the belief of many observers that
their remarkable ability to find their way back to the " parent-
stream " is inexplicable except as a mysterious instinct. Some
would hold that the ancient habit of migration to a region once
inundated by salt water has persisted through the centuries in
spite of the fact that the land has risen and that the animals must
now travel long distances in fresh water. Other investigators have
concluded that the olfactory and chemical senses, oxygen supply,
tactile and kinesthetic senses, temperature sense and the hormonic
stimulation of the developing gonads play an important part."

" Consult Chidester, F. E. 1924. A critical examination of the evidence for
physical and chemical influences on fish migration. Brit. Jour. Exp. Biol., vol. 2, pp.
79-118. The author has recently conceived the idea that the iodin-fat balance may
be concerned in the migrations of fishes. For example, the eel, living in fresh water,
may migrate down to the salt water in order to secure the optimum iodin necessary
for it to mature its eggs or sperms. On the other hand, the salmon, and other ana-
dramous fishes, may find it necessary to migrate from the salt water to the fresh to
reduce the iodin content sufficiently so that eggs or sperms may develop under
physiological conditions determined for the race ages before.

264 PISCES

In the case of the eeU a catadramous (down running) form in
which adults from Europe and America seek the same spawning
grounds, we have the most remarkable case of " homing instinct "
known in animals. The larvae of two different species find their
way back to fresh water streams of the proper continent without
guidance by older fishes. The eel migrates from fresh waters for
over 2,000 miles into the ocean and the American and the European
eels have been discovered by Dr. Johannes Schmidt of Copenhagen
to have a common spawning ground in the West Atlantic Ocean off
Florida, about equidistant between the Leeward Islands (West
Indies) and Bermuda.

The time for maturity is different in the two species of eels and
the American eel terminates its larval stage in about one year and so
is not far enough away from the American coast to go to Europe.
The European eel takes three years to pass through its larval devel-
opment and thus is near the coast of Europe when it is time for it to
move up into fresh water. It is believed that when adult eels
migrate down from fresh water streams where they have lived
perhaps 20 years, seeking a spawning ground in salt water, they are
all maturing sexually and have that stimulus in common. Their
metabolic condition may determine the optimum salinity and tem-
perature. Eels take from 5 to 20 years to mature their eggs and
sperms and then they pass down the brooks and rivers to the ocean
for their last voyage, for they die after spawning.

Fossil Relatives of Fishes. — The Elasmobranchii arose in the
Upper Silurian, and were extremely abundant in the Carboniferous.
The development of a bony skeleton can be traced in the fossil forms.
Some of the 2inc\&nt' Selachii had dorsal and anterior spines. The
fossil Holocephali show in their skulls certain similarities to the
Dipnoi. Rocks of the Devonian Age (Age of Fishes) show spines
and teeth of the Holocephali. Physostomous Teleosts (those with
the duct of the swim-bladder open) are said to be the most ancient.
Herring-like forms appeared in the Jurassic period. Dipnoi, or
lung fishes of the type now found in Australia (Ceratodus), are very
ancient, appearing in the Triassic period. The Dipnoi are inter-
mediate types between Fishes and Amphibians, but not necessarily
to be considered the " connecting links."

CHAPTER XVI

Amphibia

The familiar amphibia are the toads, frogs, and salamanders.
As the name indicates, they Hve two Hves, one in the water and the
other on land. The majority of the amphibia lay their eggs in
water and the larvae breathe by gills, while the adults breathe by
lungs. Some adult amphibia have persistent gills, however.
Amphibia are of considerable economic importance, toads being
particularly beneficial in capturing insects.

Classification

Amphibia. (Gr., " leading a double life.")

Apoda or Coecilians. (Legless amphibians found in the tropics.)

Urodela or Caudata. (Salamanders.)

Anura or Salientia. (Tailless toads and frogs.)

Characteristics

1. Skin smooth, moist and devoid of scales.

2. Limbs penta-dactylic or with five toes.

3. Skull articulates with the first vertebra by two occipital condyles,

and is composed of very few bones.

4. Lungs are present except in a few cases.

5. Heart has three chambers, a ventricle and two auricles.

6. Most of the species undergo a metamorphosis, the young living

in the water and breathing by means of gills. As the lungs
become functional these gills disappear, except in a few of
the lower amphibia.

7. As a rule, the Amphibia are aquatic or semi-aquatic In habits,

and even when they live far away from the water during
most of the year, they nearly always go to the water in the
spring to deposit their eggs.

8. Amphibians are confined to the torrid and the temperate zones.

In the temperate zone they hibernate when cold weather
sets in.

265

266

AMPHIBIA

Order i. Apoda (Gymnophiona or Coecilians). — In this family
there are about forty species, placed in seventeen genera, on slight
grounds, the characters probably having been developed independ-
ently in various countries. (Figure 142.) The Apoda have no
limbs or girdles. The eyes are subcutaneous and probably only
serve as a means of distinguishing light from dark. They burrow in
the ground feeding on small invertebrates. They have a protrusible
sensory tentacle between the eyes and nose. Fossil Apoda are
unknown, as their subterranean life does not favor preservation.
Some are oviparous and some are viviparous.

C B

Fig. 142. Group of Apoda. A, Caecilia, emerging from burrow; B, Ichthyophis
glutinosus (nat. size), female guarding her eggs, coiled up in hole in the ground; C, a
nearly ripe embryo, with cutaneous gills, tail-fin, and still a considerable amount of
yolk. (Redrawn after P. and F. Sarasin.) (trom Newman, Vert. Zool. Courtesy
of The Macmillan Company.)

After hatching, when the gills have disappeared, the young of
Ichthyophis glutinosa (Ceylon, Malay Islands) take to water and
move about like an eel, coming to the surface occasionally to breathe.
This form has from 200 to 300 vertebrae. Apoda have apparently
degenerated from the ancestral amphibians.

Order 2. Urodela (Gr., visible tail) or Caudata. — The tailed

amphibia have many vertebrae and are not so pronounced in their

metamorphosis as the Anura.

Trunk Tail

Vertebrae Vertebrae

Amphiuma dz 35

Cryptobranchus 20 24

Necturus 19 29

AMPHIBIA 267

The Urodela may retain their gills permanently, lose them per-
manently, or may have a persistent gill slit.

Family 1. Amphiumidae. — The hel/ bender {Cryptobranchus
allegheniensis) is possessed of two vestigial gill clefts, with no gills.
C. allegheniensis inhabits rivers and streams of North America and
reaches a length of over two feet. The eggs are fertilized internally,
as many as four hundred being produced in strings by the female.
The larvae have gills. Cryptobranchus has four fingers and five
toes. The skin is excessively slimy, being rich in goblet cells.

The giant salamander of Japan {Cryptobranchus japonicus
maximus), between five feet and six feet in length, is found in the
mountainous regions of Japan and China where it is still feared
and even worshipped by natives. It has no gill openings and has
but three branchial vessels (thus resembling Necturus). It is
situated from 600 to 4,500 feet above sea level, and feeds on fishes,
amphibia, worms, and insects that it secures from the small streams
of mountain meadows. It is caught on the hook and eaten by the
Japanese.

The " Congo snake ^' or " Congo eel'' {Amphiuma means) is an
eel-like salamander growing to a length of three feet. It is found in
the Mississippi rice fields and in swamps and muddy water. It lays
hard-shelled eggs and the female coils around them to protect. The
larvae have external gills with legs larger than those of the adult.

Family 2. Salamandrinae (Salamandridae) . — The crested newt
{Ti'iton cristatus) is significant on account of its sexual dimorphism.
The male has a high crest on the head and trunk. The upper
surface of the head is black and white, while the under parts are
orange yellow with black spots. The female has no crest and gen-
erally has a median yellow line on the back. The crested newt is
found in Central Europe and the British Isles. It is not found in
Spain nor in Southern France.

The vermilion spotted newt, Triturus (Diemictylus) vitidescens,
is interesting on account of its changes in color. It lives in the
water for the first three years, becoming green with external gills.
Leaving the water it becomes yellow with vermilion spots. Re-
turning to the water for the breeding season it again becomes green,
establishes pharyngeal respiration and lives in perfect aquatic
adjustment, only to return to the land again, re-establish oral cilia
and take on the vermilion and yellow of terrestrial life.

The Alpine salamander {Salat?iandra atra) is a form that produces

268 AMPHIBIA

but two young at a birth, and these feed on the other eggs in the
uterus and metamorphose before birth. It was claimed by Paul
Kammerer that this type transformed to another species on bringing
S. atra to the lowlands.

The spotted or fire salamarjder {Salamandra maculosa) is the
European species that Kammerer claimed to have duplicated by
placing S. atra in water. S. maculosa is found in moist places,
except when it spawns. Then it seeks the water and deposits fifteen
or more eggs which have been fertilized by a spermatophore dis-
charged into the water by the male. The young take nine or ten
months to develop, and live as gilled forms for about four months
before they metamorphose into the land type. The cutaneous
poison of the fire salamander is a milky white fluid fatal to small
mammals and to the cold-blooded animals as well. It is extremely
painful when applied to mucous surfaces.

The tiger salamander {Ambystoma tigrinum) is black with yellow
spots which may extend from blotches to broad stripes and bands.
It lives on land, but its larval form, once called Axolotl, may remain
aquatic or transform according to circumstances and individuals.
The capacity to retain the larval body and become sexually mature is
called Neoteny and is a most interesting attribute of certain Am-
phibia.

Family 3. Oroteidae. {The Mud-Puppies.) — The common
mud-puppy ( Necturus maculatus) of North America is possessed of
large fringed external gills. It has small limbs, lidless eyes, and
lacks maxillary bones. It is of a brownish color, with black spots.
(Figure 143.)

The blind cave mud puppy {Proteus anguineus) is found in caves
of Central Europe. It has a white body, with three pairs of bright
red gills. When taken from darkness and exposed for a time to the
light the skin becomes patched with gray and finally a jet-black.
Typhlomolge rathbuni is a similar form found in the caves of Texas.

Family 4. Sirenidae. {The Sirens.) — The mud-eel {Siren
lacertina) is interesting because of its retrograde metamorphosis.
Cope found that its young lose their external gills and then rede-
velop them. However, old Sirens can live without gills.

References on the Urodela

Bishop, S. C. 1926. Notes on the Habits and Development of the Mud
Puppy. N. Y. St. Mus. Bull., no. 268.

AMPHIBIA

269

Reese, A. M. 1906. Anatomy of Cryptobranchus allegheniensis.

Am. Nat., vol. 40, no. 472, pp. 287-326.
Smith, B. G. 191 2. The embryology of Cryptobranchus allegheniensis,

including comparison with some other vertebrates. Jour. Morph.,

vol. 23, pp. 61-157.

Fig. 143. Necturus maculosus. (Courtesy of S. C. Bishop.)

Order 3. Anura (Salientia. Ecaudata). — The Anura (Gr., not,
a tail) are highly specialized types, with marked metamorphosis.
There are over nine hundred species of frogs and toads in this order.
They have nine to ten vertebrae with the coccyx (urostyle). No
tail or gills are found in the adult.

The Surinam toad ( Pipa) lacks a tongue and has a common open-
ing for the Eustachian tubes. It is a South American form with
peculiar breeding habits. Its mating is such that the long oviducts

270

AMPHIBIA

l"'iG. I44. Mid-wife toad, Alytes obstet-
rlciuis. (Courtesy of the Amer. Mus. of
Nat. Hist.)

of the female protrude from her body and the eggs pass out to be
fertilized by the sperms and then are guided forwards so that they
are spread over the back of the female, where they sink into pockets
in the skin. Each pocket has a hinged lid which the larva lifts.

Thej'?;-^ toad {Bomhuiator igneus) has a purplish ventral surface
with orange yellow patches. When alarmed it throws itself back
to display the brilliant abdomen, elevating the head and turning the
legs over the back. B. pachyphus, a poisonous variety, has lemon-
colored patches.

The mid-wife toad {Alytres
obstetric ans) lives in France
and Switzerland. The eggs
are externally fertilized and
the male carries them away
with him into the water at
intervals. When they are
nearly ready to hatch, he re-
mains in the water to facili-
tate such development.
(Figure 144.)

The spade-foot toad {Pelo-
bates cult7-ipes) is a toad which digs deep holes in the sand by
means of a spur on the hind foot.

The Bufonidae, the true toads, comprise a large family which is
found on all continents of the globe. Toads possess a rough skin,
whose irregularities are caused by the large number of poison glands
contained in it. Their secretion is abundant and the toad is on this
account not attacked by many animals (see page 300). Bufo
leyitiginosiis americanus, the common toad of North America, is
considered to be of great economic importance. Estimates of its
value as a destroyer of injurious insects vary from ^5.00 to $15.00
per individual annually. Toads are said to devour plant-eating
millipeds which secrete hydrocyanic acid. (Figure 145.)

The tree frogs ( Hylidae) are an extensive and widely distributed
family, there being over one hundred and fifty species. They have
the power of changing color from the ordinary green to either grey or
dark brown. By means of small discs on the tips of their toes they
are able to climb trees. They are extremely noisy at night when
they spend most of their time catching insects. One form (Noto-
tre?/ia) has in the female a fold of skin on the back serving as an egg

AMPHIBIA

271

pouch. In another type {Hyla goeldii) the female carries the eggs
in a depression on the back.

The true frogs, Ranidae, are represented by only one genus {Rana)
in North America. The bull frog {Rana catesbiana — Figure 146)
is the largest North American species and one of the largest of the
genus. It reaches a length of from five to eight inches. The color
of the upper surface is green or olive brown, marked with dark
spots. Bullfrogs seldom go far from the water. They feed on other
species of Rana, and even eat ducks and chickens if small. The

Fig. 145. Toad. (Photo by Newton Miller.)

writer has found in the stomach of a single large specimen two full-
grown leopard frogs, packed as neatly as one places shoes in a box.
^\\& green frog {Rana cla?nitans) (Figure 147) has a greenish color and
is marked by small irregular black spots. Its length is three inches.
It lives in or near the water. The -wood frog {Rana sylvatica) is found
in damp beech woods often far from water.

The leopard frog (Rana pipiens), formerly called Rana virescens,
is the most common of all the North American species of Rana.
Its greenish ground color is marked by large black blotches, edged
with whitish, The legs are crossed above with black bars. There
are two irregular rows of black spots down the back and the lower
side of the pale body. The legs are very long.

The pickerel frog {Rana palustris) resembles the preceding species.

272

AMPHIBIA

It is brownish in color, with two rows of large brown spots between
the dermal plicae which are ridges or folds of skin behind the eyes.
This species is found in the eastern part of the United States.

Fig. 146. Rana catesbeiana, the bullfrog. (Courtesy of A. A. and A. H. Wright.)

The Javan flying frogs {Rhacophorus pardalis) have extremely-
large webbed feet by which they plane from branch to branch.

Studies made at the Biological Station in Dominica (Caribbean
Sea) show that a frog {Eleutherodactylus martinicensis), but one

Fig. 147. Rana clamitans, the green frog, male. (Photo by A. A. and A. H. Wright.)

inch long at maturity, deposits its eggs in small groups on wet forest
mould. The eggs are large enough to be mistaken for those of a
salamander (one-fourth of an inch in diameter). Tadpoles pass
through the ordinary gilled stage and develop in a short time, with-

AMPHIBIA 273

out living in any liquid except that of the egg. (P. G. Howes, Na-
ture Magazine, July, 1926, vol. 8, pp. 13-15.)

A Cuban toad {Bufo empusus), called the shell-headed toad or, in
Spanish, sapo de concha^ lives in a burrow, and c^kz's, itself in, using
its hard horny head as an operculum.

A gigantic frog {Rana goliath) , weighing ten pounds and said to be
" as large as a good sized terrier," is the largest frog known. It
comes from French West Africa where it is eaten by negroes who
" consider its thigh bones priceless for purposes of divination "
(Barbour).

The smallest known frog {Phyllobates limbatus), one centimeter
long, was discovered in Cuba in 1910 by Thomas Barbour after
sixty years had elapsed from the time when the species was originally
described.

Anura. Type — Leopard Frog (Rana pipiens).^ External Char-
acters.— The frog has no neck, its head being united to the trunk.
The eyes protrude considerably but can be withdrawn into the orbits
as the eye socket is not separated from the mouth by any of the bones
of the skull. In the center of the eye is a dark oval opening, the
pupil, which is surrounded by a brightly colored ring, the iris.
The eye is covered at times by the eyelids. The upper eyelid is
capable of but little movement, but the lower lid can be drawn up so
as to cover nearly the whole eye. The lower eyelid corresponds to
the lower eyelid of the mammal plus the nictitating membrane,
which appears to form a dorsal continuation of the lid. Behind the
eye is a nearly circular area, the tympanic membrane, the covering
of the drum of the ear.

Above and behind the snout lie the paired nostrils or external
nares, guarded by valves which open and close in connection with
the respiratory movements. The tip of the upper jaw is movable
and when it is pushed upward the valves of the nostrils become closed
and prevent the passage of air. Inside the mouth are a pair of
openings, the internal nares. On the upper side of the head in
front of the eyes there occurs a small light-colored mark, the brow
spot, which is the outer portion of a glandular outgrowth of the
brain, the pineal gland. (See Hatteria, N. Z. Lizard, page 308.)

The forelegs are short and consist of three divisions, the upper
arm, forearm and the hand. The hand has four fingers and an

^The material herewith presented is largely compiled from Holmes, S. J., 1927,
Biology of the Frog, The Macmillan Co.

274 AMPHIBIA

additional rudimentary finger which is easily felt under the skin.
The two inner fingers contain three joints each and the two outer
four joints each. The " thumbs " of the male are thickened notice-
ably. The hind legs are long and well suited for jumping and swim-
ming but of little service in walking. They are also divided into
three parts, the thigh, shank, and foot. The foot is well developed
and has the ankle remarkably elongated. There are five toes and
the rudiment of a sixth toe called the prehallux^ situated on the
inner side of the foot.

The toes increase in length from the first to the fourth. The
fifth is a little shorter than the third. The first two toes contain
three joints each, the third and fourth contain four each, and the
elongated fourth toe has five joints. The webbed hind feet are
used in swimming.

The Skin and Its Appendages. — The loose skin consists of the
cuticle or epidermis and the cutis vera, corium or dermis, and
contains numerous glands. The epidermis has several layers of
epithelial cells, the outer ones horny and flat, the middle polygonal,
and the inner columnar. Each cell has a distinct nucleus. In
the deeper cells the nucleus is broad, oval and rounded; in the other
cells it is flattened and thin. The horny layer is usually very thin,
consisting of one or two layers of flattened cells, but on the back
and on the under side of the toes it is very thick and rough. Con-
tractile ^/o^w^w/ cells are also found in the epidermis. Just beneath
the horny layers are found the goblet cells or mucous cells. These
are supposed to contain a substance important in connection with
the process of casting oflF the skin. Toads and frogs are known to
eat their shed skins.

Cutis Vera. — The epidermis is attached to the cutis by means of a
continuous layer of branched cells deeply stained when the ani-
mals are fed certain foods. Many of these cells are pigmented.
This layer is seldom flat, but raised into papillae or folds which are
repeated by the superimposed epidermis. In addition to this layer
the corium (dermis) has, except in webs and supplemental toes, three
distinct layers of connective tissue, with much unstriped muscle
fiber.

The skin is loose In structure and serves for an important lymph
space; accordingly the frog is much used in medical studies oi edema.
The muscle ^^«- of the cutis is unevenly distributed. It is found in
the back of the dorsal surface of the head and neck and less freely

AMPHIBIA

275

on the dorsal surfaces of the extremities, but not to any extent on
the abdomen, breast and ventral surface of the extremities, and is
absent in the feet.

Pigment of the Skin. — The greater quantity of the pigment cells
of the skin is found in the cutis. These cells are called Chromato-
phores. They play an important part in bringing about the well-
known changes in the coloring of the skin. These cells have been
found to be supplied by nerve fibers. When the nerve fibers were
stimulated, the cells were influenced. Blinded, the frog cannot
change color.

fVebs and Folds. — On the under side of the toes are little cushions
or pads. The toes are connected together by a web which makes the
foot an excellent paddle. Behind the eyes there extend two ridges
formed by a thickening of the skin. These are the dorso-lateral
dermal plicae or folds.

Muscle. — The muscles of the frog retain their vitality for a long
time after they have been removed from the body, and accordingly
they are well adapted for physiological experiments, the large
gastrocnemius or calf muscle of the frog being used a great deal in
the study of physiological activity. Contraction may be brought
about by the application of nervous, thermal, chemical, mechanical
or electrical stimuli. The response to stimulus is very rapid in
voluntary muscle and is much slower in involuntary muscle.

Tendon. — Most of the muscles are attached by one or both ends
to bones. In some cases the attachment is direct, in others by
means of a tendon which is a band of very tough inelastic connective
tissue. The outer surface of the muscle is covered by connective
tissue or fascia which is more or less elastic. The tendons of many
muscles are formed by a continuation of x\\^ fascia., which becomes
thicker toward the end of the muscle where it becomes a dense
fibrous band.

Digestive System. (Figure 149.) — The function of food is to
afford energy necessary to carry on the various activities of the
organism, and to rebuild wastes. In order that food material
may be built up into the tissues of the body, it must be rendered
soluble, so that it can pass through the inner lining of the alimentary
canal into the blood and lymph, and from these fluids through the
walls of the cells in the different parts of the body. The frog does
not chew the food taken into the mouth but swallows it down the

5ub-mandibular muscle

■Deltoid muscle
— Pectoral muscle Zd

-Pectoral muscle 3rd
Pectoral muscle 4-tt)

Linea olbo
External oblique muscle

Tronsversus muscle

Myocomma

— Pectus abdominis muscle

--Rectus onticus femoris
Vastus internus
Triceps extensor femori3

Adductor moijnus

Pectus Internus major
Pectus internus minor

Ex tensor cruris

Titjialis onticus

Tibiolis posticus

Gastrocnemius

— Tendon of Achilles
—Plantar aponeurosis

B A

Fig. 148. yf, amphibian muscular system. Ventral view. 5, outside view of the leg.

(Drawn by G. C. Weber.)

AMPHIBIA

277

esophagus into the stomach where it is acted upon by the gastric
juice.

The alimentary canal consists of: {a) the esophagus, a short,
wide tube leading from the buccal cavity to the mouth; ih) the
stomachy a wide tubular sac, one and one-half inches long, narrowed
behind and separated from the duodenum by the pyloric constric-
tion, a valve; {c) the small irjtestine, with the duodenum., one inch

/r'/gh/ auricl^

ffight ovic/act'~^<^_ \

/?/'ghf /arxj -

Sysf'ema'fic trunks'
Coel. mes. ortery
Pt. cv. vein -

/?, kidney
f^. oviduct

Ureter
Dorsal oorfa—'
flight oviduct"-'

Reef urn ''

Ventricle

J Left auricle

Left oviduct

"^ /^ostcovaj vein
- Liver
—Ouilei^
—Lett Jung

--Left oviduct

'g^^'-Left ovary

zc'Le'tt oviduct
"Left oviduct

Urinary bladder

/Abdominal vein

Fig. 149. Organs of a female frog. (From Newman, after Parker and Haswell.

Courtesy of The Macmillan Co.)

long, bent back parallel with the stomach, and the coiled ileum^ a
slender tube about four and one-half inches long; {d) the large
intestine or rectum^ a straight tube about one and one-fourth inches
long and three-fourths of an inch wide; (<?) the cloaca^ continuous
with the large intestine. It receives the large intestine^ bladder^
ureters and genital ducts.

Accessory Organs. — The liver is a reddish brown organ with two
lobes connected by a narrow bridge. The left lobe is large and
subdivided into two. The gall bladder is a small spherical greenish

'/

278 AMPHIBIA

sac between the lobes of the liver. The bile duct leads to the
duodenum, one-half inch below the pylorus. The distal end reaches
the pancreas. The pancreas is a whitish irregularly lobed mass lying
in loop between stomach and duodenum. Pancreatic ducts are
numerous and open into the bile-duct which passes through the
pancreas to reach the duodenum.

Layers of Stomach. — id) Serous, flattened and derived from
peritoneum; sub-serous, consisting of a few longitudinal muscles and
connective tissue, {b) Circular muscle layer, {c) Submucous,
composed of connective tissue and blood vessels with a muscularis
mucosae made up of inner circular and outer longitudinal muscles.
{d) Mucous, consisting of glands embedded in a matrix of connective
tissue.

At the cardiac end of the stomach, the glands are long and their
mouths deep. The pyloric glands are less deep with the mouths
of the glands deeper in proportion.

Gastric Digestion. — As in higher vertebrates, the gastric juice
contains HCl and the ferment pepsin and acts on protetlfs, converting
them into soluble peptones. There is no action on carbohydrates
and fats. The secretion of the esophagus is alkaline and lubricates
the esophagus. It must be made acid by the gastric juice before
it can digest a substance. Holmes states that the pepsin content
of the esophageal glands of the frog is greater than an equal area of
the stomach. The frog digests a piece of worm in about twenty-
four hours.

The small intestine has folds but no true villi or glands in the
mucous layer. Goblet cells and absorptive cells are found. The
small intestine receives the bile and pancreatic juice and is important
in absorption. The intestinal juice is primarily amylotic.

Pancreatic secretion is alkaline from Na2C03 and contains three
ferments: (i) Trypsin, which changes proteins to amino-acids to
peptones, completing the action of the digestive juices. Unlike
pepsin it acts in an alkaline or neutral medium. (2) Amylopsin,
which converts starch to sugar. (3) Steapsin or lipase, which
splits fats into fatty acids and glycerin and then emulsifies and
saponifies them.

The liver secrets bile, an alkaline fluid of complex composition.
The fatty substance, cholesterin, and the bile pigments are waste
products. In higher vertebrates it has been proved that bile has a
weak ferment that acts on fats, aiding in their emulsification.

AMPHIBIA 279

It also has slight amylotic Q.n6. proteolytic ferments. Desaturation of
fats is one of the most important functions of the liver.

The principal function of the liver is the formation of glycogen,
sometimes called " animal starch." The glycogen is given out into
the blood in the form of dextrose, into which it changed by an enzyme
in the hepatic cells. The liver thus acts as a reservoir for food,
storing it up when it is in excess, expending it gradually to tide over
periods of fasting, such as hibernation. Glycogen is also found in
muscles, ovaries, the central nervous system and the skeleton.
The pancreas regulates the liberation of sugar (page 455).

As an organ of excretion the liver collects u7-ea from the muscles
and so changes it that the kidneys can extract the injurious sub-
stances more readily.

When food passes from the stomach into the duodenum of the
intestine it has an acid reaction due to gastric juice. In the duo-
denum it is mixed with bile and pancreatic juices which are alkaline
and so is neutralized. Proteins not acted on by pepsin are acted
upon by the trypsin of the pancreatic juice and converted into
peptones. The pancreatic juice changes starch into sugar. The
soluble food is absorbed through the walls of the intestines into the
blood and lymph.

Spleen. — Since the spleen is found attached to the digestive tube
by mesentery it is usually identified and drawn with the digestive
system. It is, however, ductless and important in connection with
the circulatory system, but without digestive function. During
embryonic life the spleen produces red corpuscles. Even in the
adult amphibian spleen leucocytes (white blood corpuscles) and
occasional spindle cells are formed. The destruction of old, worn-
out, red corpuscles and the ingestion of wastes with pigment
granules seem to be important splenic functions.

Circulatory System. — The functions of the circulatory system
are to carry food material and oxygen to all parts of the body, and
to remove the CO2 and other waste products of tissue metabolism
to the organs where they are eliminated. Two fluids, blood and
lymph, perform these functions.

The vascular system of the vertebrate is a closed system of tubes
of vessels filled with blood, and ramifying through all parts of the
body. Its main parts are: The heart, which contracts and con-
tinually drives the blood around the system of vessels, the arteries,
which take the blood from the heart to all parts of the body, the

28o

AMPHIBIA

Carotid arch
Systemic orcti

^ci/mocufoneaus orchj

ffitjtit auricle
Left auricle

'External carotid
-InternoJ carotid

Carotid qland
Laryncjeal

—Great cutaneous
•-Pulmonory

Occipifo-
vertebral

■Subclavian
Vertebral

Celiaco- mesenteric

■Anterior mesenteric
■L umt?ors

■Posterior mesenteric

//iocs

Sciatic

Fig. 150. Arterial system of frog. (Drawn by W. J. Moore.)

AMPHIBIA

281

veins, which carry the blood from these parts back to the heart,
the capillaries, which are very small vessels connecting the arteries
and veins. (Figure 151.)

Structure of the Heart. — The heart of the frog, situated in the
anterior part of the body cavity ventral to the liver, lies within a sac,
the pericardium, whose cavity is completely cut off from the coelom.

£x ternol jugular
Infernal juqulor

Left auricle

Hepafic vein

Coslric t^e/'n
HepoliC porfol vein
Duodena/ vein —

Jnfesfinol vein -

Sp/enic vein -

Ren of vein ^^

Renol porfol vein

Vesical vein ,

Sciotic '/ein —

Righf auric fe

-Pre-cavat

Sinus venosus

^ — Pulmonary
Cardiac yein^^^^CfSrochiof vein

—Lunq

-Musculofenous

■L iver

Abdominal vein
■PostccivaJ veir)
■Testis
Spermafic vein

- -J /Sidney

OorjO'/mnbar vein

— Abdominal vein

Pelvic vein

femoral vein

Fig. 151. Venous system of the frog. Dorsal view. (After Parker and Haswell.

Courtesy of Macmillan and Co., Ltd.)

although originally continuous with it in early development. In
Amphibians and in Reptiles, the heart has three cavities, two auricles
and one ventricle.

The venous blood from the body is received into the right auricle
and the purified blood from the lungs into the lejt. Both throw
their contents into the ventricle which pumps the mixed blood in
two directions, partly to the lungs and partly around the system.

282

AMPHIBIA

Circulation Is incomplete, since three kinds of blood are found,
arterial, venous, and mixed. In many animals arrangements exist
which nearly separate venous from arterial blood.

When the pericardium is opened on the ventral side, the following
parts come into view: (i) The conical ventricle with its apex pointing
backward. The ventricle has very thick muscular walls and ap-

Truncus arteriosus

Ouricle

flight auricle——

3pira/ vo/ve—
Bulbus cordis

Dorsaf otric
venfricuior \fal\/e

VerttricJe

Opening into pulmonary vein
Opening into sinus venosus

Septum

Riqht olrio

ventricular valve

■Muscle ridges

Fig. 152. Internal view of the heart of the frog. (Modified from Kerr. Courtesy

of Macmillan and Co., Ltd.)

pears paler than the rest. (2) The thin-walled auricles lie imme-
diately in front of the ventricle; they are separated internally by a
septum. (3) The truncus arteriosus, a cylindrical body arising
from the right anterior border of the ventricle, and running obliquely
across the auricles. It divides into two trunks which soon give rise
to arteries — common carotid, systemic and pulmoCutaneous. (4)
The sinus venosus, a thin-walled sac, dorsal to the ventricle and
behind the auricle; it receives two precavae and the large postcava.

AMPHIBIA 283

The four divisions of the heart contract in order, first the sinus
venosus, then the two auricles, next the ventricle, and lastly the
truncus arteriosus. (Figure 152.)

Internal Structure. — The heart propels the blood always in one
direction and keeps the -pure and impure blood separated. The
sino-auricular aperture leads from the sinus venosus into the right
auricle. It is a transversely oval opening, guarded by imperfect
anterior and posterior valves, in the ventral wall of the sinus venosus
near the median plane of the anterior end. The right auricle is the
larger of the two. It has thin walls, thickened by muscular strands
which form interlacing ridges on its inner surface. In its dorsal
wall is the opening from the sinus venosus (sino-auricular aperture).
The left auricle is smaller, sometimes much smaller, than the right
auricle, which it resembles in the structure of its walls. In its
dorsal wall, very close to the sino-auricular aperture, is the opening
of the pulmonary vein. The inter-auricular septmn, the partition
between the right and left auricles, is much thinner than the walls
of the auricles, and is placed obliquely, the left auricle lying more
dorsal than the right. The septum ends with a free posterior edge,
opposite the auriculo-ventricular aperture.

The auriculo-ventricular aperture lies at the base of the ven-
tricle, and rather to the left side. It is guarded by valves which
hang into the ventricle and it is divided by the lower edge of the
septum into right and left divisions, admitting blood from the right
and left auricles respectively.

The ventricle is conical in shape with the apex backwards, and
has a small central cavity, with thick spongy walls. The spongy
character is due to great development of a network of interlacing
muscle strands similar to those of the auricles. The pockets
formed by muscle ridges serve to keep the pure and impure blood
separated.

Arteries. — The truncus arteriosus., a cylindrical body, arises
from the right anterior border of the ventricle and runs forward
across the auricles. (See Figure 150.) It divides in front into a
right and left branch, each of which again divides into three aortic
arches, the carotid arch, the systemic arch and the pulmocutaneous
arch.

(i) The carotid arch is the most anterior of the three arches.
It runs around the side of the esophagus and is connected dorsally
with the second or systemic arch.

284

AMPHIBIA

(2) The systemic arch runs obliquely around the esophagus to
the dorsal surface and unites with the systemic arch of the other
side at about the level of the anterior end of the kidneys to form the
dorsal aorta.

(3) The pulmocutaneous arch is the most posterior of the three
aortic arches. It divides into the great cutaneous and the pul-
monary arteries.

Veins. — Except the blood coming from the lungs, all of the blood
is returned to the heart through the three large venous trunks which
enter the siy2us venosus. The two anterior vena cavae are each formed
through the junction of three branches, the external jugular, the
innominate and the subclavian. The posterior vena cava is a median
vein which returns to the heart the blood from the liver and kidneys
and indirectly the blood from the other viscera and the hind limbs.
The three vena cavae open into the sinus venosus. The left auricle
receives the pulmonary veins.

Portal Systems. — The blood from the hind limbs does not empty
directly into the posterior vena cava as in the higher vertebrates,
but it is forced to pass through a second system of capillaries before
reaching that vessel. A portal vein, returning blood from the capil-
laries of some organ, breaks up before reaching the heart into a
second set of capillaries within some other organ. These again
unite to form a vein which carries the blood to the heart. In the
frog there are two portal systems, the i-enal portal system leading to
the kidneys, while the hepatic portal system brings to the liver blood
from the hind limbs and from the alimentary canal.

Action of the Heart. — The auricles contract and the oxygenated
blood from the left auricle, which has come in from the pulmonary
vein, is forced into the left side of the ventricle; and the impure
blood from the right auricle, received from the sinus venosus, passes
into the right side and middle of the ventricle.

The blood is prevented from being mixed by being received into
the before-mentioned pockets or chambers in the ventricle. The
impure blood, nearer the opening of the truncus arteriosus, passes out
first and into the pulmocutaneous arches, while the pure pulmonary
blood from the left side is forced out at the close of the ventricular
contraction and passes into the carotid and systemic arches. Thus
the impure blood from the heart goes mainly to the lungs and skin
where it is purified, while the purer blood passing out towards the
close of the contraction is sent throughout the body.

AMPHIBIA 285

The heart of the frog beats for hours after being removed from
the body. Electrical, thermal and chemical stimuli will cause the
heart to beat again after it has ceased normal contractions.

Vocal Organs. — In vertebrates the vocal and the respiratory-
organs are intimately associated since the production of sound is
caused by the expulsion of air from the lungs. The sound-producing
organs of the frog are situated in the larynx below the pharyngeal
cavity. The larynx opens into the pharynx through the glottis
above and posteriorly by a pair of openings into the lungs. The
skeleton of the larynx is composed of cartilages affording places for
attachment to muscles which open and close the glottis.

Sound is produced by the expulsion of air from the lungs which
set in vibration the paired vocal cords. In the males of many species
of Rana we find a pair of vocal sacs at the side of the pharynx.

Respiratory System. — The lungs are thin-walled sacs covered with
peritoneum. The inner surface of the lungs is divided by septa into
small chambers or alveoli which increase the amount of surface
exposed to the air. The walls of the alveoli are richly supplied
with capillaries. The alveoli are lined with a single layer of thin
flattened epithelial cells. On the edges of the septa they are colum-
nar and ciliated. Outside the epithelium is a layer of connective
tissue containing blood and lymph vessels and highly contractile
smooth muscle cells.

The respiratory movements of the frog consist of throat move-
ments and lung breathing. Throat movements may take place
without movements of the body or nares, with the glottis closed and
no air passing into or out of the lungs. Air is drawn through the
open nares into the mouth cavity. Its floor is lowered, and forced
out through them when the floor is again raised. Lung breathing
causes distinct lateral expansions of the body wall.

The process of respiration consists of: External respiration with
exchange of gas between the blood and the surrounding medium,
carbon dioxide being given off and oxygen taken in; and internal
respiration., gaseous exchange between the blood and the tissues.
Most of the oxygen in the blood is carried by red corpuscles in weak
chemical combination with hemoglobin. Oxygenated blood Is
bright red, impure blood is dark blue in color.

The skin is a respiratory organ in air and water, and during
hibernation it is the only respiratory organ. More CO2 is given off
through the skin than through the lungs.

286

AMPHIBIA

Urinogenital Organs. — Every cell excretes as well as secretes,
part of the waste passing off as CO2, while solids are discharged by-
special organs. The skin is an organ of excretion in the frog. In
higher vertebrates the sweat glands excrete. The liver is an im-

Suprarenal qlond
Kidney

Lcydic^s duct
S&rninal vesir.l&
Rectum

Open'inq of Leydiqs duct

—Urinary bladder
(pulled bock)

Fig. 153. Urinogenital system of male bull-frog. (Drawn by W. J. Moore.)

portant excretory organ, through bile and the formation of urea.
The walls of the intestines are important in excretion. The kidneys
are the most important. The kidneys of the frog are oval, flattened,
dark red bodies in the posterior part of the body cavity. The duct
of the kidneys (ureter) is at the outer margin of the kidneys. The

AMPHIBIA

287

-Esophagus
-Anterior end of oviduct
^ —Mesentery

Ureter (Wolffian duct)

Oviductol opening
Ureter opening

Cloaca

Urinary bladder

Fig. 154. Urinogenital system of female frog. (Drawn by W. J. Moore.)

c

(LI
>

C

o

I

u

§

«-»

u

u

CO

C

.§
o ^-^

^ >-'

^ 8

c

^ -^

v^ C
^ 2

il

c

u

>

•

a
'S

.2

r

1 1

J
1

.5

>i;

o

-T3

vri

O

AMPHIBIA

289

ventral surface is flatter than the dorsal. The orange-colored ad-
renal body, on the ventral surface, is a gland of internal secretion.
(See page 286.) The kidneys are made up of coiled uriniferous
tubules with a knot of blood vessels, the glomerulus^ at one end.

The Wolffian duct is the sperm-
duct in the male and the ureter
In the female. The Miillerian
duct is the oviduct in the female
and rudimentary in the male of
Rana pipiens. It is absent in the
bull frog. The kidneys of the
male frog are closely related to the
sexual organs. (Figures 153 and

154-)

The vasa eferentia are ducts
carrying spermatozoa from the
testes, passing into the substance
of kidneys and through the kidney
to the ureter which acts as a vas
deferens also and is called Ley dig s
duct.

The kidney receives blood
from two sources, the renal ar-
teries from the aorta and the renal
portal veins which bring venous
blood to be purified. The kidney
secretes urea (NH2CO3) and Na,
K, Ca, and Mg phosphates and
chlorides.

The urinary bladder is a bilobed
sac attached to the ventral side of
the cloaca below the openings of
t\xQ ureters. The bladder collects Fi^- ^S^- Ventral view of the nervous
11, -11 system or frog. (After Woodruff, Foun-

urme when the cloaca is closed. , ,. / d- 7 c -c ^ /-

dations of Biology, from ncker. Lourtesy

Nervous System.''— i:\i^ brain of The Macmillan Co.)
(Figure 155, A^ B, andC) consists

of small olfactory lobes at the anterior end of the two elongated
cerebral hemispheres; two large optic lobes^ a diencephalon with the
vestigial pineal stalk attached, a narrow cerebellum situated just

^ Strong, O. S. 1895. Cranial nerves of amphibia. Jour. Morphol., vol. 10.

290

AMPHIBIA

anterior to the rather wide medulla oblongata. Ventrally one sees
the paired optic nerves, which cross (optic chiasma), the infundibulum
to which is attached the pituitary gland or hypophysis. There are
ten pairs of cerebral nerves. (See table, below.)

Sense Organs. — Olfactory sense is served by small nasal cavities
with folded walls of nasal membrane. The anterior nares lead to the
cavities from the outside and t\\t posterior nares open into the mouth.
In the fish, as already noted, the olfactory openings were used only
for smell, but in the amphibia and higher vertebrates, the nares are
important in respiration. The eyes are well developed, but the

Origin, Components, Function and Distribution of the Ten Cerebral Nerves

OF Fishes and Amphibia

Num-

Name

Functional

Cells of Origin

Distribution

ber

Components

I.

Olfactory

Sensory

Nasal mucous
membrane

Mitral cells of olfactory bulb.

II.

Optic

Sensory

Gang, cells of
retina

Diencephalon (Thalamen-
cephalon).

III.

Oculomotor

Motor

III. Nucleus in
midbrain

Sup., Inf. and Int. Recti; and
Inf. oblique muscles of the
eye.

IV.

Patheticus
or Tro-
chlearis

Motor

IV. Nuc. dorsal
midbrain

Sup. oblique muscle.

V.

Trigeminal

Sensory

(Motor) V. nuc,

Mandibular nerve to jaws;

and

medulla Gass.

Ophthalmic, Maxillary and

Motor

gang.

Mandibular nerves.

VI.

Abducens

Motor

VI. Nuc, medulla

Ext. rectus muscle.
Sensory fibers associated.

VII.

Facial

Largely

VII. Side of

Muscles of face, muscles of hy-

Motor

medulla

oid arch, roof of mouth, pala-
tine, hyomandibular and
lateral line (in larval am-
phibia).

VIII.

Auditory

Sensory

Side of medulla

Utriculus, sacculus and semi-
circular canals of Internal

IX.

Glosso-

Motor and

Side of medulla

ear.
Muscles and sensory corpus-

pharyngeal

Sensory

cles of pharynx and tongue.

X.

Pneumo-

Motor and

X. Nuc, medulla

Sensory and motor fibers to

gastric or

Sensory

visceral arches, pharynx.

Vagus

heart, and alimentary canal.

AMPHIBIA

291

animal, like many others, is sensitive primarily to moving objects.
The tongue is supplied v^\t\\ papillae, bearing taste organs. In order
to detect a substance it must be liquefied.

Hearing is quite well developed. Near the center of the tym-
panic membrane is a little protuberance, the tip of the columella,
the small bone at its inner end connected with an opening in the
skull which communicates with the inner ear. When the tympanic
membrane vibrates in response to sound waves, the vibrations com-
municated to the internal ear produce the sensation of hearing.

Amphibian tadpoles have functional lateral line organs sensitive
to vibrations of low frequency, one step below the sensation of
hearing. In adult amphibia they disappear. In the skin there are
thermal and tactile organs.

General Consideration of the Amphibia

Distribution. — Amphibia live in or near swamps, ponds and
streams and are never found in salt water. They are on this ac-
count absent from most oceanic islands. Although many of them
have lost their gills and taken up terrestrial life, they return to
water to spawn. The salamanders are for the most part limited to
the temperate zone, while the Anura are found widely distributed
and hibernate or aestivate as temperature demands.

External Anatomy. — There is a great variation in the matter of
retention of gills in the salamander, some having persistent gills and
lungs while others lose the gills entirely.

In the toads and most tree frogs, webs are lacking from the hind
toes, while certain species of frogs have their toes ending in rounded
sucking discs.

Amphibia respire largely by the skin, which is full of capillaries.
The stratum corneum of the skin is shed periodically. Warts and
granules are cornifications of the epidermis. In the males of the
African " hairy frog " {Astylosternus), the granules of the skin are
developed at the breeding season into hairlike structures, which,
according to Kingsley, are supplied with nerves and are probably
sensory in function, although certain writers have described them
as accessory breathing organs.

The skin of amphibia is rich in mucus glands, Cryptobranchus
being especially slimy. Some species of amphibia have well-de-
veloped poison glands. (See page 300.)

2g2

AMPHIBIA

Skeleton of the Amphibia. — The sku// of the amphibian has less
cartilage in the adult than is found in the bony fishes. It has two
occipital condyles for articulation of the first vertebra. The car-
tilaginous nasal capsules are connected with the auditory capsules

nasal

,sphiruhethmoid

digits

palaiine-

fronto-parietaL.
pterygoid

cervical vertebra,
clavicle-

sacral vertebra

jTused

-•calcaneum

tibio-fibula

/
astragalus

Fig, 157. Skeleton of garden toad. (After Kellogg, Animals and Man. Courtesy of

Henry Holt & Co.)

by trabeculae. In the tailless amphibians {Anura) there is a well-
developed tympanic cavity opening internally by the Eustachian
opening.

In the frog, cartilage develops into the bones of the upper jaw

AMPHIBIA 293

and the hyoid apparatus, which remains partly cartilaginous and
supports the tongue. The cartilaginous cranium has a number of
cartilage bones and some membrane bones.

The scapula is ossified and connected with the dorsal supra-
scapula, which is partly cartilaginous. The ossified coracoid has a
bar of cartilage, the pro-coracoid, while the clavicle is a membrane
bone attached to it. The coracoid and pro-coracoid are joined
ventrally by the epi-coracoid cartilage.

The episternum, tipped by the cartilage plate, the omosternum,
projects anteriorly from the united epi-coracoids. The sternum
extends posteriorly and is tipped by the cartilaginous xiphisternum.

The pectoral limb consists of the humerus, the fused radio-ulna,
six carpals and four complete digits with a vestigial pollex on the
radial side.

The vertebral column has nine vertebrae and an elongated poste-
rior urostyle. The vertebral column furnishes a firm dorsal sup-
porting structure, and protects the delicate nerve cord.

The pelvic arch consists of two long curved ilia, the fused ischia
with the ventral fused pubes. Into the acetabulum or socket fits
the femur. The tibia and fibula are united (tibio-fibula), while the
two proximal tarsal bones, the calcaneum and the astragalus, are
extremely elongated, making an additional segment in the hind
limb. Next to the three distal tarsal bones there are five well-
developed digits with a spur, the prehallux on the tibial side of the
first.

Muscles. — In the lower Urodela the muscles are segmented in
both trunk and tail. In the Anura, the myotomic structure is for
the most part lost except in the divisions of the rectus abdominis
muscles. Muscles are attached to bones by means of bands of
modified connective tissue known as tendons.

Physiology. Digestive System. — In the common toad, teeth are
absent. The retractor bulbi muscles pull the eye balls down in both
toads and frogs for protection, so that they are able to clamp down
on worms and insects that otherwise might escape from their mouth.

When present in the Amphibia, teeth occur on the premaxillae,
maxillae and vomers, but they are also found on the palatines and
the dentaries. The tongue is fixed in many salamanders, while in
the frogs and toads it is usually free posteriorly and can be flipped
out. In a few forms, called the Aglossa, it is absent.

294

AMPHIBIA

Respiratory System.— The most striking example of metamor-
phosis occurs in those amphibia in which the larval external and
internal gills are replaced in the adult by lungs (see Figures 158 and
159). In many salamanders, respiration is pharyngeal and cuta-

Infernal carotid

Hyoid

—/famus

cornmun/'cans

— Oil I cleft

■Occipifo-vertebral
— Bulbus arteriosus
■Scapular
-Conus arteriosus ^

■Pulrnonory

—Anterior scapular

-y^ Broc/lio/

r^ Fhsterior scapular

£piijastric

Pancreot Ic — —
Hepatic —

Anterior mesenteric —

t/roqenifal — C

liypoqastric

■Dorsal aorta
■Gastric

Coelioco -mesenteric

—Accessory mesenteric

^ Posterior mesenteric

L umbar

■Posterior epiqosfric

Iliac

—Sciatic

-Caudal

Fig. 158. Arterial system, ventral view, of Cryptobranchus. (After Reese, Amer.

Nat., 1906, vol. 40.)

neous.

Even in the frog, during hibernation, respiration is cuta-
neous. The body temperature of the frog varies from 58° to 61,°
Fahrenheit. Salamanders are mute, but frogs and toads are noisy
creatures, especially at spawning time.

AMPHIBIA

295

Circulatory System. — It is very easy to see in the embryonic
Anura and even in the adult Urodela a transition from the fish type
of vascular system. The red blood corpuscles of the Amphibia are
oval, nucleated and extremely large. In the salamander Amphiuma,
the red corpuscles are eight times as large as those of a man.

i/enfr/c/e
Superior \/ena co\/a y '^.

Innominate 1

Internal Jugular - -

Brochiol-

Posterior corc/mol-

Splenic

~ — ^ — inferior gastric

Pancreatic

Portal

Atx/ominol

■Mesenteric
Inferior cava

Vein of Jacobson

Prom urinary ■

I Hoc
Caudal -
Fig. 159. Venous system. Ventral view. (After Reese, Amer. Nat., 1906, vol. 40.)

Urinogenital Organs. — In the male amphibian, we find an inter-
esting condition in that the " Leydig's duct " transports both urine
and sperm to the cloaca.

Embryology. — The ripe ova of frogs have distinct po/ar dif-
ferentiation. The upper " animal pole " is deeply pigmented, while

296

AMPHIBIA

the lower " vegetal pole " has no pigment but is rich in yolk and
much heavier. Frog eggs are deposited in a mass of jelly which
encloses green algae aiding in aeration, and which unquestionably
aids in the absorption and radiation of heat. The jelly also pre-
serves the eggs from friction and the attacks of enemies. (Figure
160.)

Fig. 160. The metamorphosis of the frog. (After Brehm, from Galloway- Welch,
Textbook of Zoology. Courtesy of P. Blakiston's Son & Co.)

Cleavage. — The first vertical cleavage occurs about 3 hours after
fertilization, and divides the ovum into a right and a left half. The
second vertical cleavage about three-fourths of an hour after the
first is at right angles to the first while the third cleavage, an equa-
torial one, divides the dorsal pole from the ventral. Segmentation
which is total but unequal results in the development of a ball of cells
of which the dorsal ones are smaller and more numerous than the
yolk cells beneath. At this stage the egg is called the blastula.

At the close of segmentation the egg has developed into a hollow
sphere with the cavity or blastocoel nearer the dark upper pole.
The upper hemisphere has two quite distinct layers. A crescentic
groove appears at one side of the egg between the layer of white and
dark cells. The horns of the crescent extend until they form a cir-
cle, the blastopore, which is filled with a mass of white cells called the
yolk plug. Rapid division of the marginal black cells in the dorsal
region reduces the diameter of the blastopore. At this stage the

AMPHIBIA

297

egg is called the gastrula. The upper germ layer or ectoblast de-
velops from this layer of black cells.

From the development of the band of cells and the fusion of its
right and left halves, a meridional band extends into the dorsal lip
of the blastopore. On the dorsal side, the groove becomes a long
narrow slit which is the primitive digestive tract of the frog. The
roof of the niesenteron, as it is called, is the beginning of the lower
germ layer, the entoblast.

Fig. \b\A. Vinal Edwards and Robert Goffin at the nets. Woods Hole, Mass.

The middle germ layer, the mesoblast^ arises as two plates split
off from the outer surface of the entoblast and yolk cells. The
mesoblast separates into two layers with a space between which
becomes the coelom.

Germ Layers. — From the ectoblast are derived epidermis, nerv-
ous system and the lining of the mouth and anus. An anterior
invagination called the stomodaeum develops into the mouth and
a posterior one into the proctodaeum.

From the entoblast are derived the lining epithelium of the diges-
tive tract and its associated glands.

From the mesoblast come muscles, bones, blood vessels and urino-
genital organs.

Superficial Changes. — At first the egg is spherical, then in four
or five days it becomes ovoid, finally elongating at about the loth

298

AMPHIBIA

day into a fish-like tadpole with distinct head, body and tail. Three
pairs o{ external gills ^ which are later to be replaced by internal gills,

function i n respiration. I n
front of the two gill-arches
two depressions unite to form
a ventral horseshoe-shaped
sucker. Shortly after hatching
the mouth and anus are devel-
oped and the alimentary canal
becomes tubular and folded
while its diverticula^ the liver
and pancreas, are formed.

Internal gills covered by
operculi replace the external
gills. Rapid increase in size
occurs, the tail which has been
developed to a remarkable ex-
tent soon begins to degenerate,
and the limbs appear. At
about the 8th week the gills are
replaced by lungs. At about
the loth week the tadpole
ceases to feed on algae, the
skin is moulted, the gills are
absorbed, the digestive system
assumes its adult condition and
the animal becomes carniv-
orous. Then the tail is com-
pletely resorbed, the hind limbs
Fig. 161 5. George M. Gray, Curator, ^ ^ ■' , , . ,

^.^ ■ D- 1 • t T u . elongate and the animal comes

Marine Biological Laboratory. «.,njiiga.Lv, m, «_i

(Photo by Chidester, 1931.) to shore as a young /ro^.

References

Hodge, C. F., and Dawson, J. Civic Biology. Ginn and Co.
Wright, A. H. 1910. The Anura of Ithaca, N. Y. A key to their eggs.

Biol. Bull., vol. 18, no. 2, pp. 69-71.
Wright, A. H. 1914. Life Histories of the Anura of Ithaca, N. Y.

Carnegie Inst. Washington, D. C, Pub. 197.

AMPHIBIA 299

Parental Care. — A number of species of frogs and toads build
nests in which eggs are deposited. Some frogs attach these nests to
leaves over the water and the tadpoles hatch and drop in. Still
others deposit their eggs in masses of froth some distance from the
water. The male sometimes proves to be the caretaker of the young.
In the obstetric toad he carries strings of eggs until the tadpoles are
ready to hatch. In another species, the South American Rhino-
derma, the male transfers the eggs to his huge vocal sacs until they
are hatched. The viviparous salamanders have already been men-
tioned.

Parthenogenesis. — Bataillon, Loeb and others have induced the
parthenogenetic development of frogs. Parmenter's studies of the
chromosomes of these fatherless creatures show that they may be
either male or female.

Experimental Embryology and Regeneration. — On account of
the convenience with which amphibian eggs may be secured inland,
they have been used a great deal in experimental embryology.
Grafting of two different species and divisions of the egg at the two-
cell stage have been successfully accomplished.

W. Roux, Hertwig, Morgan, W. H. Lewis, Spemann, and many
other investigators have performed experiments on the developing
eggs of amphibia. Roux injured the first formed blastomeres,
and Hertwig (1893) and later Morgan (1902) studied the develop-
ment of half embryos and whole embryos from one of the first two
blastomeres of the frog's egg. W. H. Lewis first showed (1904,
Amer. Jour, of Anatomy, vol. 3) that the optic vesicle determines
location of the lens. Spemann and his students have made many
significant studies on the development of the eggs of Triton, the
salamander. (Consult Morgan, T. H., 1927, Experimental Em-
bryology, Columbia University Press.)

Harrison, who was the pioneer (see page 495) in tissue culture
(J. Exp. Z06I., 1907, vol. 4, p. 239; 1910, vol. 9, p. 787), has trained a
number of anatomists, who have carried on extremely important
experiments on transplantation and extirpation of limbs and eyes in
Amphibians. An interesting account of some of the work was
brought out in the discussion following a lecture by Detweiler given
at the November, 1930, meeting of the N. Y. Neurological Society,
and reported in Archives of Neurology and Psychiatry, vol. 25, no. 4,
pp. 914-919, April 1 93 1. (Consult also papers by Harrison, Det-
weiler, D. Hooker, F. Swett, and R. Burns.)

300 AMPHIBIA

Habitat. — As stated before, amphibia hibernate and aestivate.
That they are able to live in cavities in solid rock has often been
reported. But Buckland, after experiments with frogs and toads
enclosed in cavities of stone and excluded from air and food, found
that none lived over two years and most succumbed inside of a year.

Fossil Relatives. — The Stegocephalia are extinct, tailed forms
which lived in fresh water. Their teeth were complexly infolding
(Labryinthodonts). One form known as Mastodonsaurus had a
skull over four feet long and nearly as wide. They were abundant
in the lower Permian and Upper Pennsylvanian. Traces of gills in
certain fossil forms indicate that the Stegocephalian larvae were
aquatic. They were armored, some of them having overlapping
scales like fishes.

The Urodela have very few fossil remains. One, found in Ger-
many, in Miocene rocks, was called " homo diluvii testis," or " the
man who witnessed the flood." Anuran fossils are rare, and found
only from the Comanchian to the present, while Apodan {Gymno-
phionan) fossils are unknown.

The connecting links between the lobe-finned fishes (Cros-
sopterygii) and the amphibians have not yet been discovered, but
comparison of the skulls, labyrinthine teeth and fishlike shoulder
girdles of land-living amphibia with these fishes indicates their close
relationship.

The Stegocephalia are apparently related to certain of the extinct
Reptiles, the Theromorpha (Therapsida), which appear to have
affinities with the Mammals. Huxley, comparing amphibians with
mammals, brought out the fact that both have two occipital condyles,
and that the carpal bones resemble each other. But Theromorpha
(see page 331) also have two occipital condyles.

Economic Importance of Amphibia. Positive. — i. As food, we
find that frogs (legs) are in considerable demand.

2. Frogs and toads are important enemies of injurious insects.

3. As experimental animals for use in Physiology and Embry-
ology the Amphibia are unexcelled.

4. Savages secure arrow poison from the skins of some Anura.
Poisonous Amphibians. — The poisons from the skin glands of

toads, salamanders and newts, when injected can kill mammals,
birds, reptiles, and even fishes, provided the dose is proportionate
to the size of the animal. Small birds and lizards succumb in a few
minutes while guinea-pigs, rabbits and dogs succumb in an hour.

AMPHIBIA 301

A young dog will suffer discomfort for twenty-four hours after taking
a toad in its mouth. Snakes, however, eat toads without any dis-
comfort.

The Indians of Columbia obtain poison from Dendrobates tincto-
rium by exposing the frog to fire, and use it for shooting monkeys,
as it acts on the central nervous system. Toads do not cause warts,
although their skin is poisonous. The Chinese have for thousands
of years used a toad-skin preparation called " Senso " as a heart
stimulant. It is said to be fifty to one hundred times as powerful
as digitalis, to which it is chemically allied.

Resistance of Amphibia to Poisons. — The toad is not poisoned
by dosages of digitalis that prove fatal to the frog. This resistance
depends upon a difference in the tissues, as the isolated hearts be-
have the same. The frog is tolerant of morphine in quantities fatal
to man.

References on the Amphibia

Barbour, T. 1926. Reptiles and Amphibians.

Chamberlain, F. M. 1927. Notes on the Edible Frogs of the U. S.

Report of the Commissioner, U. S. Fish. Com.
DiCKERsoN, Mary C. 1906. The Frog Book. New York.
Kirkland, H. a. 1897. The Habits of the American Toad. Hatch

Expt. Sta. Bull. 46.
Miller, N. 1909. The American toad. Am. Nat., vol. 43, pp. 641-

668 and 730-745.
Surface, H. A. 1913. First Report on the Economic Features of the

Amphibians of Penna. Zool. Bull., Penna. Dept. Agr., Harrisburg,

May-July.
Wright, A. H. 1914. Life Histories of the Anura of Ithaca, N. Y.

Carnegie Inst. Washington, D. C, Pub. No. 197.
Wright, A. H. 1920. Frogs, Their Natural History and Utilization.

Bur. Fish. Doc. No. 888.

CHAPTER XVII

Reptilia

Amnion and Allantois. — Comparison of Reptilia with Aves and
Mammalia shows that the first two Classes, sometimes grouped as

Sauropsida^ are much more
closely related to each
other than either one is to
the Mammalia. The three
classes are alike in possess-
ing a structure called the
amnion.

In the course of devel-
opment in the reptiles, birds
and mammals, called
Amniota, the embryo is
enclosed in a membranous
dome-like sac, the amnion,
which contains a fluid, the
amniotic liquor. A net-
work of blood vessels is
developed over the yolk-sac
which is an organ of res-
piration as well as of nutri-
tion. (Figure 162.)

w\ '' f / ^^^ I ra^^Mi • vtM* -^" higher mammals,

however, the allantois
effects respiration. The
allantois is a vascular sac-
like outgrowth from the
Fig. 162. Vertebrate embryos with their hinder part of the embry-
membranes. A, reptile or bird; 5, placental onic intestine. It is pres-
mammal. In A the yolk sac is functional and ent in Amphibia but is very
the allantois respiratory; in B the yolk sac is 5^1^11. 'XV^ fishes and am-

functionless and the allantois becomes the , ., . , , • u ^u „ii„„
, . , .,■ I J /Ar phibia, lackmg both allan-

nutntive placenta and umbihcal cord. (Arter ^ , .°

Wilder, History of the Human Body. Courtesy tois and amnion, are some-
of Henry Holt & Co.) times called Anamniota.

302

REPTILIA 303

In Amniota, the allantois grows around the embryo as a stalked
vesicle^ which in reptiles, birds and monotremes lies close beneath the
egg shell and acts as a respiratory organ during the rest of the em-
bryonic period. It also receives excretory matters from the kidneys.
In the mammals above the monotremes, an important vascular
connection takes place between mother and fetus by means of the
allantois. This is called the placenta. The allantois becomes
attached to a definite region of the uterine wall and from it vascular
processes or villi arise so that the fetal and maternal blood vessels
come into close relationship with each other. Gills are no longer
necessary since the allantoic placenta functions in the respiration and
nutrition of the fetus.

Classification

Super-order i. Cotylosauria. Primitive fossil forms.

Super-order 2. Chelonia. Living forms, including turtles and
tortoises.

Super-order 3. Therapsida (Theromorpha) . Fossils linked with
mammals.

Super-order 4. Sauropterygia. Fossil forms with a long neck.

Super-order 5. Ichthyopterygia. Fossil aquatic forms.

Super-order 6. Archosauria. Besides the primitive fossil Theco-
dontia, Pterodactyla and Dinosauria, the super-order in-
cludes one living connecting type, the Rhyncocephalian
Hatteria, and the living orders of Crocodilia and Squamata.

Since only four orders of the Reptilia have living representatives,
we shall discuss these first, and defer the description of fossils to
the section on Fossil Relatives (page 330).

Living Orders of Reptilia

Chelonia.
Rhyncocephalia.
Crocodilia.
Squamata.

Characteristics

The reptiles have an amnion, an allantois, a horny skin, ossified
skeleton, two auricles, two ventricles with incomplete septum
(except in the Crocodilia), a single occipital condyle, are cold
blooded, breathe by lungs and have twelve cerebral nerves.

304

REPTILIA

Natural History

Super-Order 2. Chelonia. — Skull without temporal vacuities.
Compact body enclosed in a case, consisting of bone and horny
plates, which form a dorsal carapace and a ventral plastron. The
vertebrates and ribs of the thoracic region fuse into the carapace,
and the pectoral and pelvic girdles are internal to the ribs. The
limbs terminate in claws, or are flipperlike. There are no teeth and
the quadrate bones are immovable. The cloaca is elongated.

This order includes tortoises, which are strictly terrestrial;
turtles y semi-aquatic and marine; and terrapins y which are hard-
shelled fresh water species.

Fig. 163. Atlantic green turtle. (Courtesy of N. Y. Zool. Soc.)

The green turtle ( Chelone mydas) is a marine form, reaching a
weight of 400 pounds, whose flesh, oil and eggs are all consumed by
South Americans. In this country, soup and flesh are esteemed
delicacies. The hawks-bill turtle {Chelonia imbricatd) is a smaller
marine form once used as a source of tortoise-shell, but now little
sought. The leathery turtle {Sphargis coriaced) is the largest living
turtle, reaching a weight of 1,000 pounds and a length of six feet.
It is marine, but spawns on land. It is inedible. The giant tortoise
{Testudo) ot the Galapagos Islands is a gentle form, frequently
photographed at zoos carrying children on its back. It may reach
a weight of 300 pounds. The common snapping turtle {Chelydra

REPTILIA

305

serpentina) of Eastern America and the alligator snapping turtle
{Macrochelys lacertind) of Southern United States are vicious forms,
feeding on fishes. The common snapper attacks young water fowl.

#

o

^

®

e

^,\

®

o

c?

Q

^

Fig. 164. Soft-shelled turtle. (Courtesy of N, Y. Zool. Soc.)

Fig. 165. Diamond back terrapin. (Courtesy of N. Y. Zool. Soc.)

The pai?jted terrapin^ Troosts terrapin^ and the yellow-bellied terrapin
are Httle used for food, but the red-bellied or " slider " terrapin and
the diamond-backed terrapin are much served in fashionable

3o6

REPTILIA

restaurants. Overfishing has reduced the importance of the terrapin
fisheries over one half in 30 years. The wood terrapin is edible and
protected from extermination in New York State. The common
spotted turtle is said to be unable to eat when out of the water.

Fig. 166. Skeleton of Cistudo {Emys europaea). V, vertebral (neural) plates;
C, costal plates; M, marginal plates; Nn, nuchal plate; Py, pygal plate; B, plastron
(ventral shield); CI, clavicle; Jcl, inter-clavicle; Sc, scapula; Co, coracoid; Pco, acromial
process (pro-coracoid); Pb, pubis; Js, ischium; Jl, ilium; H, humerus; R, radius; U,
ulna; Fe, femur; T, tibia; F, fibula. (After Claus-Sedgwick. Sonnenschein, London.)

The musky map and speckled turtles are all important enemies of
insects. The common box turtle feeds on insects, but also consumes
some vegetable matter. It has a lobed plastron which it can close
tightly. (Figs. 163, 164, 165, 166.)

REPTILIA

307

The soft-shelled turtles {Aspidonectes feros) are edible forms
found from South Carolina to Texas and up the Mississippi to the
Great Lakes. They weigh as much as 30 pounds. They are omniv-
orous, feeding on Crustacea and insects, but also destroying fish
and waterfowl, since they are extremely fast swimmers.

Type— The " Slider" Terrapin {Pseudemys rubriventris) .—The
turtle has no teeth, but horny jaws. Its tongue is broad and soft,
and the pharynx is thin walled and distensible. The thick-walled
esophagus bears papillae. The stomach has a pyloric valve. The
small intestine consists of the duodenu7n, ileum, with an ileocecal
valve, large intestine and rectum. There are paired cloacal sacs and
the respiratory system consists of the glottis, larynx, trachea and two
bronchi. The lungs are large and many branched. The hyoid
apparatus supports the larynx. Movements of the hyoid, neck
and anterior limbs aid in respiration.

Aquatic tortoises and marine turtles have two large sacs at-
tached to the cloaca. These are filled with water and richly vascular.
At times, when water is replaced by CO2, they may buoy up the shell
and supplement the lungs. Females are said to utilize the liquid in
these sacs in wetting down the eggs deposited in sand on the shore.

The heart has two auricles and incompletely divided ventricles,
the septum being perforated. The venous blood passes from the
postcaval and two precaval veins into the sinus venosus and thence
to the right auricle. From the right auricle it flows to the right side
of the ventricle.

From the right ventricle it goes to the puhnonary artery which
divides on the right and left; and also through the left aorta which
sends blood to the viscera and into the dorsal aorta. The left arch
is therefore venous to the alimentary canal by way of the coeliac.
Purified blood from the lungs passes to the auricle and left side of
the left ventricle. The blood then goes through the right aortic arch
to the dorsal aorta. It is impure, because mixed in the ventricle.
The turtle has no renal portal, but the usual hepatic portal system.

Urinogenital Organs. — The urinary system consists of paired,
reddish, oval kidneys, paired ureters, a urinary bladder shaped like a
dirigible balloon, the cloaca, oval in shape, and the anus.

The testes are oval, yellow bodies with vasa deferentia leading
to the grooved penis which is attached to the anterior wall of the
cloaca. The paired ovaries are rather diffuse, somewhat resembling
the single left ovary of the bird. The oviducts open into the cloaca.

3o8

REPTILIA

Turtles lay white oval or rounded eggs in the sand, tamping the
earth down with the posterior portion of their shell.

Nervous System. — The cerebral hemispheres and cerebellum are
large and the olfactory apparatus is well developed. The eyes are
small and hearing is acute. Tactile sense is well developed, the
animal being sensitive to raps on its shell. The skin of the ap-
pendages is especially sensitive.

Super-Order 6. Archosauria. Rhyncocephalia. — Rhyncoce-
phalia (Gr. rhynchos, snout; and cephale, the head) are generalized
types, linking the Squamata, Crocodilia and Dinosauria. They
resemble the Lacertilia in form, but differ in having a fixed quadrate
bone. They are represented by one living relative, Sphenodon
( Hatteria) . (See page 1,1^ i .)

The New Zealand lizard, Sphenodon or Hatteria, has a well-
developed ^/«d'«/d'_>'^, sensitive to light. It lives in a burrow. There
are several fossil relatives from the Permian to the present, with
maximum development in the Triassic.

Fig. 167, Gavial. (Courtesy of N. Y. Zool. Soc.)

REPTILIA

309

Order Crocodilia. — Alligators, crocodiles, and caimans, like the
turtles, have an oval cloacal opening, immovable quadrate bones,
and bony plates in the skin. They differ in structure from all other
reptiles although their shape is hzard-like. They have abdominal
ribs and abdominal sternum. Their teeth are placed in sockets.
The heart is completely four-chambered.

The Chinese alligator {Alligator sinensis) lives in the Yang-tse
Kiang in China. It is a small species, greenish black, with yellow
spots. It is the nearest living relative of the American alligator.

The American alligator {Alligator mississippiensis) is found as
far north as North Carolina. It may reach a length of 16 feet 3
inches. It is the only crocodilian that bellows. It is much less
vicious than the crocodiles. Alligators are sold to tourists, and
there is a constant demand for their hides, used for bags and pocket-
books. Alligator farms supply animals to the cinema producers.

The caimans of South America are quite vicious. Gavials,
found in India, may reach a length of thirty feet, and are quite
ferocious, but rarely attack man. (Figure 167.)

The salt water crocodile and the mugger of India and the sacred
African crocodile ^ are extremely dangerous animals and cause many
deaths annually. An American crocodile, resembling the African
form, was found in Florida in 1875, ^1 I^^. W. T. Hornaday. It
is extremely vicious.

Order Squamata. {Super-Order F/.)— This order includes two
sub-orders, Lacertiliay or lizards, and Opkidia, or snakes. The
Squamata (Lat. squamatus, a scale) have horny scales, renewed
periodically, movable quadrate bones, a transverse cloacal opening
and paired penes.

Sub-Order Lacertilia. (Lat. lacertus, a lizard.) — The lizards,
chameleons and iguanas have certain characteristics distinguishing
them from the snakes and the crocodilia. Lacertilia have paired
appendages or rudiments, scaled ventral surface, tympanic mem-
branes, a sternum (usually) and movable eyelids.

The blind-worm, or slow-worm, a limbless lizard {Anguis Jragilis)
found in Europe and Asia, is a most snaky animal. Its body is
covered with smooth round scales and its locomotion resembles that

1 " The crocodile is esteemed sacred by some of the Egyptians, by others he is
treated as an enemy, and the people of Elephantine even eat their flesh. The
lonians called the Egyptian ' Champsae ' crocodiles, after the wall-lizards of Ionia."
(Hereodotus II, 69.) The name Champsae remains today in the Coptic language.

3IO

REPTILIA

of a snake. It is not blind and certainly not at all worm-like. It is
viviparous. Ditmars cites a case of 2. Jourteen-inch female giving
birth to sixteen young, each three inches long. Young slow-worms
feed on termites. Adults feed on earth-worms, insect larvae and
slugs. The teeth are re-curved and fang-like with traces of a groove^
showing that the animal is related to the poisonous lizards.

The " glass snakes " {Ophisaurus apus of Europe, and 0. ventralis
of America) are limbless lizards. (Figure 168.) Their movable
eyelids, and ear openings distinguish them from the true snakes.
When attacked, they quite easily drop their brittle tail and move
away to regenerate a new one.

Fig. 168. Glass snake, Ophisaurus ventralis. (Courtesy of N. Y. Zool. Soc.)

The beaded lizards ( Helodermatidae) include two poisonous forms
found in deserts in the United States, Mexico and Central America.
The Gila monster {H. suspectum), a beaded lizard with grooved
fangs, has been reported to be quite poisonous to man, but the
evidence is rather inconclusive. (See p. 328.) Its large tail is a
reservoir for fat storage. It may reach a length of two feet.

The geckos of the Mediterranean region {Geckonidae) can run
on smooth surfaces, climbing walls and ceilings by means of adhesive
pads on their toes. The suctorial disks are arranged like the slates
on a roof. The gecko is non-venomous, feeding on insects. It
drops its tail when attacked. (Figure 169.)

The European ''green lizard" or wall lizard {Lacerta viridis).

REPTILIA 311

is a generalized type. It eats insect larvae but is not able to digest
those with hard chitinous coverings. Its tail is very brittle and
quickly dropped off when the animal is irritated. The common
swift {Sceleporus spinosus undulatus) is an arboreal lizard living
chiefly on tree-inhabiting insects. It deposits its eggs, which re-
semble tortoise eggs, in a rather deep tunnel.

Fig. 169. Ringed gecko, ventral view. Tarentola annularis. Northern Africa.

(Courtesy of N. Y. Zool. Soc.)

T\v^ flying dragon {Draco volans) (Figure 170) lives in the Indo-
Malay region. It has membranes stretched between the fore and
hind limbs and extends these to plane from tree to tree or limb to
limb. It is brightly colored like the flowers among which it lives.

The horned-toad {Phrynosoma cornutum) (Figure 171) is a true
lizard armed with long neck spines and peculiarly adapted for desert
life, having a dull grey concealing color and being equipped with
valves in its nostrils which prevent the inhalation of fine sand. It
drinks dewdrops and eats insect larvae and ants. Captive speci-
mens have been observed by Ditmars and others to shoot jets ot
blood from the eyes a distance of five feet. The animal is not
poisonous, is easily tamed, and can be " hypnotized " by gently
stroking its ventral surface.

312

REPTILIA

The skinks include a species (Eumeces quinquelineatus) which
lives from Massachusetts to Florida and westward to Texas. It
may reach a length of ten inches. It changes in color in a striking
manner as age increases.

The monitor ( Varanus sahator) was for many years considered
the largest lizard. It is found in Ceylon and the Malay Archipelago.
It reaches the length of eight feet and is able to swallow a hen's egg

at one gulp. It is used as
food.

The Nile monitor ( Var-
anus niloticus) digs through
the rain-softened walls of
the clay nests of a South
African termite, and de-
posits its eggs, ten to thirty
in number, in the center of
the nest. The termites re-
pair the nest, but after
about ten months the
young escape from their
leathery egg shells and,
aided by the rainy season,
tunnel out and seek the
nearest stream.

The largest living lizard
{Varanus ko7nodoensis) was
only recently discovered
in the hills of Kommodo
in the Lesser Sunda Is-
lands. It is said to reach
a length of ten feet.

The smallest lizard
( Lepidoblepharis sanctae-
mariae) found in eastern
Panama is about two inches long, weighing less than five grams.
The sea lizard, an iguana {Amblyrhynchus cristatus), inhabits
the shores of the Galapagos Islands. It feeds on sea weeds and
when attacked swims away into the sea. The animals are gregari-
ous, living in flocks of several hundred.

The common iguana {Iguana tuberculatd) found in tropical

Fig. 170. Draco volans (flying lizard). (After
Hilzheimer.)

REPTILIA

3^3

America is largely herbivorous, but the young individuals feed upon
insect larvae. Adults will also capture small rodents and young
birds. The iguana is arboreal and grows to a length of six feet.
The flesh, tasting much like chicken, is considered a delicacy in
tropical America.

.rv

Fig. 171. Phrynosoma. (Courtesy ot" X. Y. Zool. Soc.)

The chameleons {Chamaeleon vulgaris) are arboreal forms found
in the Old World, some in Africa and Arabia, others in India and in
Spain. The club-shaped tongue, half the length of the body, is
covered with glutinous material and is used in capturing insects.
The colors include green, blue, grey, brown, black and yellow.
Chameleons are able to change their color with extreme rapidity,
but do not, according to Ditmars, assume the colors of their back-
ground, as do fishes and amphibia.

The Aynerican " chameleon " {Anolis carolinensis) is found in
Southeastern United States. It is not a true chameleon, but
changes color under changed conditions of light and temperature.
From ashy grey it will turn to a dull yellow or a vivid green. Its
food is meal-worms and flies and it drinks dew from leaves. It
reaches a length of six inches.

Sub-Order Ophidia} (Gr. ophis, a snake.) — Snakes have a

1 Much of the material on snakes in this text has been compiled from R. L. Ditmars'
Reptiles of the World and Reptile Book. Doctor Ditmars has inspected a part of the
MS.

314 REPTILIA

bifid protrusible tongue, frequently fanged, movable, displaceable
maxillary and palatine bones, numerous vertebrae, movable ribs
and ventral scutes. They lack tympani. Eustachian tubes, sternum,
and appendages. Their eyelids are fused. The lungs are asym-
metrical, some species having a degenerate right and others a de-
generate left lung. The urinary bladder is absent and the urine,
chiefly uric acid, as in birds, solidifies in the air. The temperature
of snakes varies from 68° to 84° Fahrenheit.

"The limbless serpent can outclimb the monkey,
Outswim the fish,
Outleap the zebra,
Outwrestle the athlete.
And crush the tiger."

(Owen.)

The yellow-headed worm snake {Glauconia albijrons) reaches a
length of eight inches. It lives in ant hills and is a formidable
enemy of termites.

The Boidae {pythons and boas) have vestigial hind legs, a pair
of strong movable spurs attached to vestiges of the pelvic bones.
Among the common pythons are the regal python, which may reach

Fig. 172. West Indian boa. (Courtesy of N. Y. Zool. Soc.)

a length of thirty feet, and can swallow a small antelope; and the
smaller Indian python, which is much used in side-shows, as it is
easily tamed. The Anaconda or water boa is extremely vicious.
It is viviparous, Ditmars recording one specimen that gave birth

REPTILIA

3^S

to thirty-four young, each one twenty-seven inches in length and an
inch in diameter. (Figure 172.)

The common boa {Boa constrictor) reaches a length not greater
than II feet. It is a native of tropical South America. Easily
tamed it is used by " snake-charmers," although its smaller size
renders it less thrilling to audiences, fearful lest they miss the sight
of a snake tightening its coils on its tamer. Ditmars relates a case
of a brood of 64 young. Other boas include the vicious Cuban boa,
the common American rubber boa, and the Indian sand boas. The

Fig. 173. Thamnophis marciana. (Courtesy of A. G. Ruthven.)

brown sand boa or two-headed snake {Eryx johnii) has a round
stumpy tail, sometimes painted with " eyes " by the Hindoos, who
claim that one end of the animal watches while the other sleeps.

The sub-family Colubrinae includes the majority of snakes.
All of this family lack poison glands and hollow fangs. (Figure
173.) The Eastern ribbon snake is a beautiful reptile, reaching a
length of 3 feet. It feeds on fishes and amphibians. The garter
snakes {Eutania) are all prolific viviparous forms, and are beneficial
for the most part. The water snakes iTropidonotus) are sometimes
quite vicious but are non-venomous. The brown water snake is the
largest, reaching a length of 5 feet. An Indian water snake {T.
macrophthalmus) spreads its neck and was mistakenly brought in
by the natives when the British first offered a bounty for the hooded
cobra. The Indian rat snake of the Malay peninsula is protected
by a fine, as a rat exterminator. It reaches a length of 8 feet. The
American black snake {Zamenis constrictor) is not a constrictor,
but holds its prey to the ground under a coil. It destroys small
rodents, but occasionally eats amphibians and young birds.

T\it family Colubridae include a number of large snakes killing

3i6

REPTILIA

by constriction and feeding entirely on mammals and birds. They
are of tremendous importance in destroying injurious rodents.
The pilot black snake ( Coluber obsoletus) is found from New England
to Florida and ranges west of the Mississippi. It hibernates with
the timber rattler. The chicken snakes {^Coluber o. quadrivittatus)
are feared by poultrymen as enemies of young fowls and as egg
eaters, but destroy more than enough rodents to pay their way.

The hog-nosed snake, blowing viper or puff-adder {Heterodon
platyrrhinus) is a most sinister reptile. When alarmed it flattens
the anterior portion of its body, hisses, shakes the tail and darts its
head here and there. It feigns death on some occasions, rolling
on its back and becoming limp. It will not bite.

The common king snake or chain snake {Ophibolus getulus)
ranges from Southern New Jersey to Florida and westward to the
Pacific coast. Although a deadly enemy of the poisonous snakes of
America and apparently immune to their venom, Ditmars found
that when injected with the poison of the Cobra, they died within
the hour. The king snake is cannibalistic but is extremely fond of
rodents. A large king snake may be 6 feet long. The animal,
although such an enemy of other reptiles, is easily tamed by man.
The milk snake [Ophibolus doliatus) is found in the Northeastern
states. It frequents barns, hunting for mice, and has been mis-
takenly thought to rob the dairy, although it has never been caught
" milking the cows." The ring-necked snake (Diadophis regalis)
found west of Illinois is the largest of the genus. It lays eggs which
are so thin skinned that they hatch in half the time required by
other snake eggs. It lives under flat stones and in dead trees and
feeds upon earthworms, salamanders, young lizards and snakes.
The scarlet king snake ( Cemophora coccinea) is found in the south-
eastern part of the United States. Its chief interest is that it is
confused with the deadly coral snake. The scarlet snake feeds on
mice and reptiles. It is oviparous and coils around its eggs until
they are hatched.

The Opisthoglypha are not as poisonous as the Elapine and Vi-
perine snakes, since they have furrowed or grooved fangs, located
at the extreme rearof the upper jaw. Ditmars, however, emphasizes
the fact that their venom acts on the nerves and that it will kill a
lizard more quickly than the bite of a viper.

The annulated snake {Sibon septentrionalis) of Africa and the
tropical Americas, and the pike-headed snake {Oxybelis acuminatus)

REPTILIA

317

of Mexico and South America, are opisthoglyphs that feed on lizards.
The Proteroglypha include two sub-families, the Hydrophinae
which are marine forms, and the Elapinae which include Old World
Cobras and the New World coral snakes Their fangs are hollow
and connected with venom glands secreting powerful poison. The
fangs are rigidly attached on the anterior portion of the upper jaw
instead of folding back against the roof of the mouth as in the
viperine snakes.

^^^y ' ^Bf j^K^^^^Ki^^iiflBlk

^i^^_ ^^^Bf

■

^^-. jP

.4 ^

' ' . L ■•

Fig, 174, Sea snake, (Courtesy of N. Y. Zool. Soc.)

One of the Hydrophinae^ the yellow-bellied sea snake {Hydrus
platurus), is found in salt water off the coast of Central and tropical
South America, The sea snakes swim in schools of 20 or more.
They are preyed upon by fish and sea birds. Their venom is ex-
tremely powerful and produces a benumbing of the nerve centers.
(Figure 174.)

The Elapine snakes have a slender body and a narrow head.
Their fangs are short, always erect and situated on the anterior
portion of the jaw. But one genus of these reptiles is found In
America.

The Spectacled Cobra or " Cobra-de-Capello " ( Naja tripudians)
Is found In India and the Malay Archipelago. Although the fangs

3^8

REPTILIA

are extremely small, their wounds are more quickly fatal than those
of the vipers with large teeth. Spectacled cobras are said to be
most vicious when in captivity, apparently proving untamable.
Ditmars states that cobra venom ejected and entering the eyes
will produce blindness or death. Cobras feed on small rodents,
birds and amphibians and can swallow eggs entire. They reach a
length of over 6 feet. (Figure 175.)

Fig. 175. Asp. (Courtesy of X. Y. Zool. Soc.)

The Egyptian cobra or Asp ( Naja haje) is a smaller snake than
the spectacled cobra, reaching a length of not more than five feet.
It is extremely intelligent and startlingly quick in its movements.

The king cobra or Hamadryas ( Naja bungarus) reaches the
length of 12 feet. It is said to be the most deadly of the Old World

REPTILIA

319

snakes. Apparently tamable, it Is most treacherous. Cobras are
oviparous. In 1927, there were 19,069 deaths from snake-bite in
India. Cobras and kraits were chiefly responsible.

The Ringhals {Sepedon hue 7n achates), a South African cobra,
reaches a length of five feet. It feeds on amphibians, birds and
their eggs, and small rodents. It ejects jets of poison six feet.
The krait {Bungarus coeruleus) is an extremely dangerous snake
found in Asia and the Malay Archipelago. It has no hood. It
reaches a length of 4 feet.

The Australian black snake {Pseudechis porphyriacus), an ex-
tremely venomous snake, is sometimes called the purple death
adder. (See p. 328, Snake Venoms.)

Fig. 176. Body rings of false coral snake and true coral snake. (Courtesy of Anti-

venin Institute of America.)

Several species of Doliophis are found in Southeastern Asia.
The venom-secreting glands are not confined to the head but extend
through the anterior one-third of the body. Due to this strange
variation, the heart is located more posteriorly than in other snakes.

About 26 species of the New World Elapine snakes are known,
two of them being found in Southern United States. The two

320 REPTILIA

species of Elaps found in the United States resemble harmless
forms including the Western milk snake and the scarlet king snake.

The poisonous snake (Figure 176) has single black rings bordered
with a pair of yellow rings while in the harmless species the yellow
rings are single bordered with a pair of black rings. The harlequin
snake or coral snake {Elaps fulvius) is found in our Southern States
and ranges into Mexico. It is cannibalistic but very fond of lizards,
which seem quite susceptible to its poison. Coral snakes seem quite
gentle and do not " strike " but certainly do bite and chew vigor-
ously. They are oviparous and according to Ditmars the eggs re-
quire as much as thirteen weeks for development.

Family Viperidae. — The viperine snakes are long fanged with
small vertical movable maxillaries each bearing an extremely long
hollow fang. Each maxillary has a lever bone aiding in the eleva-
tion of the fang. When the jaws are closed, the fangs of the vipers
fold against the roof of the mouth. The majority of the viperine
snakes have thick bodies and flattened heads, the pupils resembling
those of a cat eye.

Certain of the true vipers {Sub-family Viperinae) are horrific
in appearance while others found in South Africa are according to
Ditmars " Moderately slender with an ordinary head while the eye
has a round pupil and there is a loreal plate (between the eye and
the nostril) as seen in the typical harmless snakes."

The Cape viper {Causus rhombeatus) has relatively small fangs
which are lifted at will. Cape vipers are found in Southern Africa,
reaching a length of about 3 feet. Unlike vipers in general, this
form is oviparous. It feeds on frogs, apparently without using its
poison fangs. The common viper ( Vipera berus) is found all over
Europe and is the only poisonous snake found in the British Isles.
It feeds on rodents and young birds. The sand natter ( Vipera
ammodytes) is found in Southeastern Europe. A soft horn about
one-eighth of an inch in length protrudes from its snout. It
reaches a length of two feet and is extremely dangerous. It feeds
on small rodents.

The Daboia or Russell's viper ( Vipera russellii) is one of the
most deadly snakes of India. The Puff adder {Bitis arietans),
found in Africa, hisses loudly at each breath. The gaboon viper
{Bitis gabonicd) of tropical Africa will stand its ground when sur-
prised, hissing viciously. Ditmars calls it " the most sinister of all
the venomous snakes, in its aspect." The horned viper or asp

REPTILIA

321

{Cerastes cornutus) is a small African desert species with a sharp
spine above each eye.

The pit vipers {Sub-family Crotalinae) have a deep pit between
the eye and the nostril. (Figure 177, A and B.)

The water moccasin or cotton-mouth snake {Agkistrodon piscivorus)
is a semi-aquatic form found in the Southeastern United States.

Poison qlond

Head of Micrurus

(Pro feroglypha)

Cross section
of cjrooved fonq.

Grooved foncj.

Poison gland

Head of Crotalus

(So ten o q hyp ho)

Cross section
of hol/Ov^ fonq-

Tronsporenf" yiev</

of hollov^ fane

Fig. 177. Fangs and head of coral snake {Micriirus) and rattler {Crotalus). (Cour-
tesy of Antivenin Institute of America.)

It reaches a length of six feet. It is omnivorous, devouring fishes,
amphibians, other^reptiles and small birds and mammals. Death
may ensue in one-half hour after the bite of an adult specimen.
(Figure 178.)

The copperhead snake {Agkistrodon co7ttortrix) is found east of
the Mississippi River, ranging South from Massachusetts. It
occurs as far west as Texas. It is not extremely vicious although
one of the most venomous of forms. Its food includes amphibians,
small birds, and rodents. It is viviparous and produces as many as
a dozen young at a birth. (Figure 179.)

The bushmaster {Lachesis mutus) is found in Central and tropical
South America. Reaching a length of ten feet, it is said to be the

322

REPTILIA

only Crotaline snake that lays eggs. Ditmars cites a case of death
in less than ten minutes after an eight-foot bushmaster had bitten a

man.

Fig. 178. Cotton mouth (water) moccasin, Agkistrodon piscivorus. (Courtesy of

Antivenin Institute of America.)

The. Jer-de- Lance {Lachesis lanceolatus) Is found ranging from
Southern Mexico into South America. On the Islands of Martinique
and Guadeloupe it is much feared by workers on sugar plantations.

In Honduras, the " barba amarilla " or yellow beard, an ally of

Fig. 179. Copperhead snake, Agkistrodon mokasen. (Courtesy of Antivenin Institute

of America.)

REPTILIA

3^3

the fer-de-lance of Martinique and the jararaca of tropical South
America, is feared on account of its size (8>^ feet) and the fact that
it injects a teaspoonful of poison. (Figure i8o.)

The diamond back rattlesnake ( Crotalus adamanteus) , found in the
Southeastern part of the United States, grows to a length of eight
feet and weighs more than any other Doisonous form. Death ensues
in less than an hour after its bite.

■.^\--

M^I^Mi?^-^

Fig. 1 80. Barba amarilla. (Courtesy of N. Y. Zool. Soc.)

Other rattlesnakes of the United States include the pigyny or
ground rattlesnake of Southeastern United States, the Massasagua of
the Central and Western states, the Texas rattler (6 feet long) (Figure
181), the timber rattler of the eastern mountains, and the horned rattler
or sidewinder of the Western states. (Figure 182.)

Ditmars has recently described a ten-foot Honduran rattlesnake
that produces paralysis of the neck muscles in a few minutes.

The smallest adult snake, a Syrian Leptotyphlops, is blind, lives
in the sand and resembles in size and shape a steel knitting needle.

General Consideration of Reptilia

Distribution. — The Lacertilia are of wide distribution. The
wall lizard {Lacerta muralis) is found from Belgium to North Africa.
The Chelonia are found in the temperate and tropical regions for
the most part. The sea-turtles are confined chiefly to the tropical
seas. The Caimans are found in Central and South America, while

3^4

REPTILIA

REPTILIA 2^^

the alligators are found In North America and in China. The true
Crocodiles of Africa and Asia have an American relative. The
Snakes are widely distributed, the common grass snake {Tropi-
donotus natrix) ranging from Sweden to Algeria.

Fig. 182. The sidewinder or horned rattler {Crotalus cerastes). (Courtesy of Chas.

Bogert.)

Anatomy and Locomotion. — The Reptiles vary from the limbless
Snake to the Lizards and Crocodiles which have well-developed
limbs and a powerful tail.

The oddest appearing forms are of course the Turtles. In the
Chelonia both dorsal and ventral surfaces are covered by large
horny plates. The scales are confined to the head, neck, limbs and
tail. The Lizards and Snakes have horny plates covering their
entire surface. In the skin of the geckos there are minute hard
bodies intermediate between cartilage and bone. In the Crocodilia
the whole surface is covered with horny plates underlaid with a pad
of dermal connective tissue. In all Reptiles, except the Crocodilia,
a periodical moult or ecdysis occurs. This casting of the old skin
is done completely in Snakes and some Lizards, while in other
Reptiles it is by degrees.

Lizards move by means of their limbs and tail. Snakes have an
undulatory movement on land and are able to swim very well.
The aquatic Chelonia utilize their legs very effectively in swimming.
Crocodilia depend upon limbs and tail and are able to swim with
rapidity. On land their activity is much reduced but they are
surprisingly quick in seizing prey and in the use of their powerful
tail.

Digestive System. — For the most part Lizards are non-poison-
ous. The Mexican beaded Lizards have grooved teeth and are
supplied with poison glands. Snakes rarely have premaxillary
teeth. The vipers have a single large curved hollow poison fang

326 REPTILIA

with small reserve fangs at its base. This is moved to a vertical
position when a snake opens its mouth to strike its prey. In the
Chelonia there are no teeth but the horny jaws resemble a bird's
beak. The Crocodilia have many conical hollow teeth on the pre-
maxillae, maxillae and dentary.

The tongues of certain Lizards are forked and retractile as in
Snakes. The chameleon has an extremely long club-shaped tongue.
In Snakes the tongue is extremely slender and is utilized as a tactile
organ. Some hold that it is sensitive to sound vibrations.

In the esophagus of turtles there are large horny recurved papil-
lae. Crocodilia and Chelonia have a gizzard-like stomach. In
Lizards and Snakes a rudimentary cecum is found at the anterior
end of the large intestine.

Respiratory System. — In the Snakes and some snake-like Lizards
there is a great reduction in the size of the left lung. Chameleons
have inflatable air-sacs which enable them to puff up and startle
their enemies. The Crocodilia and Chelonia have large and well-
developed lungs.

In the Crocodilia the nostrils are at the upper end of the snout
and can be closed by two valves. In front of the choanae, two soft
" palatal folds " shut off the mouth from the pharynx. When a
crocodilian is drowning its prey, it can push the glottis anteriorly to
meet the posterior nares, and then respire comfortably.

Old ma.\e gavials have a cartilaginous hump containing air which,
situated at the tip of the snout, enables them to remain under water
longer than younger animals.

Superficial Differences between the Crocodilia

Alligator. Crocodile.

Exposes four points above water Exposes snout and neck crest when

when floating — the eyes and the floating,
nostrils.

Fourth tooth from front bites into Fourth lower tooth from front pro-
socket in upper jaw; in older ani- jects slightly outward and fits in-
mals it may pierce jaw and show to grooved notch in outer edge of
from above. upper jaw.

Makes nest of sticks and grass. Makes nest in sand.

Less active and vicious. More active and vicious.

The caimans may have a blunt snout like the alligator or a
pointed one like the crocodile. They also have the fourth tooth of

REPTILIA

327

the lower jaw fitting into a socket. The gavial has a decidedly long
and pointed snout and the first and fourth lower teeth bite into
grooves in the upper jaw.

Voice. — Snakes and lizards have no vocal cords, but hiss through
the nose. Crocodilia roar and the tortoise of the Galapagos Islands
bellows.

Circulatory System. — xAll Reptilia have a four-chambered heart,
but with the exception of the Crocodilia the ventricular septum is
perforated. The red corpuscles of snake blood are 11 microns long,
approximately the same as in frog blood, but those of the lizard are
about 16 microns in length.

Excretory System. — The kidneys are not always symmetrical in
Reptiles, in the Snakes for example being elongated and band-like.
The kidneys of Lizards are fused in the mid-line. A urinary bladder
(usually bi-lobed) is found in Lizards and Chelonians, but is lacking
in Snakes and Crocodiles. The urine is rich in salts and solidifies
quickly on reaching the air as in the case of birds.

Reproductive System. — Fertilization is internal in the Reptilia,
which have either a bifid or a median solid penis. Many Lizards
and the majority of Snakes are viviparous but the Crocodilia and
Chelonia are oviparous.

Care of the Young. — Crocodilia and Chelonia deposit their eggs
in nests of sand or twigs and grass, and return to them periodically.
The female python protects her eggs by coiling around them, her
temperature rising several degrees during the process to promote
hatching.

Nervous System and Sense Organs. — In the Reptilia the brain
has distinctly advanced from the amphibian type. The cerebral
hemispheres have developed greatly but the cerebellum remains
small. The eyes are large and the ears well developed, except in the
Snakes where a middle-ear is absent. Tactile, olfactory and
gustatory senses are well developed. The Turtle is surprisingly
sensitive to taps on its shell.

Rattle of the Rattlesnake. — Several species of snakes, including
the bushmaster and the copperhead, have a large horny spine at
the base of the tail. In the rattlesnake after the first year, three
moults occur annually and at each moult a new rattle is formed.
Considering the first ring to represent the first year, the age of a
rattlesnake may be determined by allowing three rings for each
year. The possibility of accidental loss of a segment or two must
of course be considered.

328 REPTILIA

Poisonous Reptiles. — With the exception of the beaded Lizards,
the Lacertilia are not poisonous. A Bornean Lizard, Lanthanotus,
is suspected of being poisonous. Heloderma produces painful
swellings in man, but its venom has no hemolytic action.

The salivary glands of Snakes are differentiated into organs for
the formation of powerful poisons. In the Australian black snake
they act on the bloody causing intravascular clotting; some of this
class also contain hemolytic substances. The arterial and venous
walls are broken down and the blood oozes out. Gangrene may set
in. Cytolysins act on red cells, white cells and the endothelium of
the blood vessels.

The other class, typified by the cobra, cause a paralysis of
respiration. According to Cushney and Yagi, the action of cobra
venom is like that of curare in that it paralyzes nerve endings.
Noguchi states that in the case of cobra venom toxic action must
be ascribed to neurotoxin. Poisoned animals suffer from motor
paralysis.

The chief local effect produced by rattlesnake and water moc-
casin venom is, according to Noguchi, the escape of red blood
corpuscles from the vessels. Hemorrhages are not restricted to
the site of the injection of the venom. Animals killed with snake
venom decompose rapidly because of the decrease in bactericidal
power of the blood, caused by the venom.

Toxicity. — According to Barbour the common laboratory stand-
ard of toxicity ^ is the minimal lethal dose per pigeon. The poison
of sea-snakes which is dangerous to man instantly kills fish. Turtles
are almost as susceptible to all venoms as fish. Worms, Insects
and Echinoderms are only slightly susceptible to snake venoms.
While snakes and frogs quickly succumb to cobra venom, they are
relatively insusceptible to the bites of rattlers and moccasins.
The digestive juices destroy most snake venoms, but poisons of the
cobra, the Old World Vipers, and the Australian black snake are
resistant.

^ Philpott (Proc. Soc. for Exp. Biol, and Med., vol. 26, pp. 522-523, 1929) has
shown that the venom of the Texas rattlesnake {Crotalus atrox) in dilutions of 0.00025
gm. per cc. had an immediate lethal effect on Paramecium caudatum, Stentor coeruleus
and Bursaria truncatella. Action was slow in effect on Volvox spermatosphara and
Oxytricha fallax, and was only temporary and slight in Chilomonas Paramecium.
Coleps hirtus, Podophyrafixa and Dileptus gigas were unaffected. The minimum lethal
dose of Agkistrodon piscivorus (moccasin) for Paramecium caudatum was 0.0000014
gm., and for the venom of the fer-de-lance {Bothrops atrox) was 0.0000125 gm.

REPTILIA 329

Treatment of Snake Bite. — If administered very soon after the
person is bitten, anti-venin serum is effective. A tight ligature,
preferably of rubber, should be placed above the wound, but must
not be left on more than half an hour at a time or gangrene will set
in. The wound should be cut open with a knife or razor blade and
may be sucked although this is unsafe if a person has sores in his
mouth. A strong potassium permanganate solution is injected or
poured upon the wound and serum is administered if available.
After the first few moments potassium permanganate is not effective.'
Subsequent treatment should include the draining of a wound for
two weeks at least.

Most engineers and explorers now carry into territory where
rattlers and moccasins abound, antivenins, a little vial o{ potassium
permanganate crystals^ a scalpel or razor-blade to cut open the wound,
bandages, and a tourniquet. However, if one wears boots or puttees,
he is usually quite well protected. Hypodermic injections of strych-
nine are useful as a stimulant. It is held by some that small doses
of alcohol are beneficial. This is a pernicious belief, as the adminis-
tration of alcohol is likely to hasten death by distributing the venom
more rapidly in the blood vessels. Caffeine (strong coffee) and
strychnine are beneficial in relieving from giddiness and stupor.

Susceptibility of Snakes to Poison. — The snake is not poisoned
by amounts of digitalis fatal to the frog. Its tissues are not sus-
ceptible, as isolated hearts behave the same. Cayenne pepper,
fresh slaked lime and powdered sulphur are worthless as snake
repellents. Snakes are immune to tear-gases and to poison gases
including phosgene and chlorin. They are, however, susceptible
very quickly to chloroform and also to mustard-gas.

Do Mother Snakes Swallow their Young? — This question is one
that has often been propounded. There is absolutely no doubt that
snakes do swallow other snakes and that they may even, when
alarmed, swallow their own young. Many people have testified to
seeing the old snake swallow little ones, but no one has ever reported
the interesting phenomenon of the little snakes returning to the
light of day. Perhaps they do!

1 Dr. A. M. Reese is studying the effects of potassium permanganate on mam-
mals receiving injections of snake venom that would ordinarily be toxic.

330 REPTILIA

Some Superstitions That Exist Regarding Snakes. ^ —

"l. Snakes do not suck or milk cows. This is next to a physical
impossibility and science has no authentic record to prove it
true.

" 2. Hoop snakes do not exist. Substantial rewards have been offered
for specimens and a demonstration of* rolling' but no one has
tried to claim the reward.

"3. Snakes do not charm birds but cause them to become so excited
or nervous that they lose reason or instinct of protection.
This is especially true of nesting birds.

"4. When a snake is killed some vital organ or organs stop function-
ing, but all cells are not killed. These living cells function
by reflex action for a varying period of time dependent on the
kind of cells, and not dependent on the action of the sunlight.

" 5. Snakes do chase people, especially the blue racer. It is, however,
a coward and will run equally fast in the opposite direction
if the pursued become the pursuer.

"6. Snakes do not sting or bite with any part of the body except the
teeth. The tongue is sensory in function, being the seat of
the senses of touch, taste and perhaps smell.

"7. No snake or part thereof has any medicinal property which can-
not be found in some other material. For instance sweet oil
is just as good as rattler oil, and not as repulsive to most
people. This belief has been imposed upon the people by
'fakes' or 'quack doctors.' They are not even considered by
reputable physicians.

"8. Green is not a warning color against poisonous snakes.

"9. Snakes are blind only during the process of molting or when the
old skin is loose and is being shed because a new skin has
developed underneath.

" 10. A horse-hair rope will not act as a barrier to a rattlesnake. This
has been demonstrated many times by actual test,"

Fossil Relatives. Super-Order I. Cotylosauria. — Geologically
the oldest known reptiles, appearing in the Carboniferous and dis-
appearing in the Triassic. Skulls completely roofed, v^^ith no
lateral temporal vacuities. Pelvis, flattened. Resembled Stego-
cephalia in presence of pectoral cleithrum. Heavy neural arches.
Example: Seymouria.

' By permission of R. D. Casselberry from the Pennsylvania State College, Cor-
respondence Study Department, Zoology 35 C, Lesson 7.

REPTILIA 331

Super-Order 11. Chelonia. (Gr. chelone^ a tortoise.) — Fossil
relatives of the turtles include a Permian species Eubotosaurus,
found in S. Africa, which had teeth and widened ribs.

Super-Order III. Therapsida. {Anomodontia, Theromorpha.)
(Gr. ther, a wild beast; morphe^ form.) — Single lateral temporal
vacuity below post-orbital and squamosal. Brain case high, ear
low, columella articulates with quadrate. Lower jaw flattened,
with loosely articulated bones. Fossils found in Permian and to
the Triassic age, chiefly from Africa and North America.

The Mammalia are supposed to have arisen from this order,
possibly by way of the Theriodontia, which were carnivorous, with
teeth resembling the incisors, canines and molars of mammals.
The Monotremata (see p. 373) have been compared with the Therio-
dontia, in support of such a theory. Examples: {Dicynodon^
Cynognathus^ Galepus, Ophiacodon).

Super-Order IV. Sauropterygia. (Gr, sauros^ a XvL?ixdi\pterygia^
fins.) — /\quatic reptiles with a single temporal vacuity, bounded by
the post-orbital squamosal arch. Single coracoids, meeting in a
ventral symphysis. The cervical region is extremely long, and the
caudal portion of the spinal column is very short. Sauropterygia
range from the Triassic to the Cretaceous.

Super-Order V. Ichthyopterygia. {Gr. ichthysy & fish; ptejjgia,
fins.) (Ichthyosauria.) — Marine reptiles with a single lateral
temporal vacuity, a large head, elongated jaws, teeth in grooves, no
neck, and a long tail resembling a fish. They had two pairs of
paddle-like limbs, no sacrum, primitive pelvis, no sternum, but well-
developed abdominal ribs. They are of the Mesozoic age, ranging
from the Triassic to the Upper Cretaceous.

Super-Order VI. Archosauria. — Several Orders belong to this
super-order, which includes the reptiles that have two lateral tem-
poral vacuities in the skull.

Order i. — Thecodontia are the earliest Reptiles to show a diapsid
skull with two lateral temporal vacuities.

07-der 2. — Rhyncocephalia appeared in the Permian, with maxi-
mum development in the Triassic.

Order J. Dinosauria. (Gr. deinos, terrible; sauros, a lizard.) —
These Mesozoic land reptiles were among the largest, reaching a
length of one hundred feet and a height of twenty feet. The earliest
species, in the Triassic, were carnivorous. Another branch, the
Sauropoda, include gigantic herbivores. A herbivorous branch, the

33^

REPTILIA

Ornithopoda, had a bird-like beak, and the Orthopoda had pneumatic
bones and a bird-like pubis.

Order 4. Crocodilia. — Fossil Crocodilia are found in the Triassic
strata. Huxley traced an " almost unbroken series " of Crocodilia
from the Triassic down.

Order 5. Pterodactyla or Pterosauria. (Gr. pteron, a wing; and
sauros, a lizard.) — The Pterosauria were adapted for flight, having
a long neck and a pair of bat-like leathery wings. The bones were
light and hollow, the breast bone was keeled. The earlier forms had
sharp teeth. They varied in size from that of a sparrow to the
Pterodactyl with a twenty-four foot wing stretch. The largest
forms lacked teeth and had a short tail.

Order 6. Squamata. — The Squamata are geologically the most
recent of the Reptilia now persistent.

Sub-Order {a). Lacertilia. — There are a few fossil lizards in the
Jurassic, but the majority began with the Tertiary.

Sub-Order {b). Ophidia. — Fossil snakes appeared in the Ter-
tiary strata.

Sub-Order (c). Pythonomorpha. — These extinct forms had a
snake-like body with paddle-like limbs used in swimming. They
reached a length of over fifty feet {Mososaurus). The skull re-
sembled that of the Lacertilia.

Adaptations of Reptilia. — The Crocodilia have protective bony
plates in the skin, sharp teeth, strong jaws and a muscular tail. A
valve in the throat shutting off the mouth from the pharynx (see p.
326) enables them to submerge their prey and still breathe with
ease. The Chelonia have a strong compact box-like shell and
powerful cutting jaws. Large lungs enable them to remain under
water for some time. Lacertilia have rapid locomotion. In some
protective coloration is evident. The long tail is a storehouse for
food and in many species is broken off and left when enemies are
pressing. Ophidia have displaceable jaw bones and loose ribs,
permitting the animal to swallow prey larger than itself. The
glottis is anterior to the mouth, enabling the snakes to breathe while
swallowing. The teeth are recurved so that the prey cannot escape.
Snakes kill by crushing or utilizing poison glands.

Economic Importance of Reptilia. — Crocodilia furnish skins that
are used in the manufacture of shoes, bags, pocket books and belts.
They feed on fish and in the case of the Asiatic and African crocodiles,
destroy many human lives. The flesh of crocodiles is said to be

REPTILIA 23:^

unpalatable on account of its strong musky flavor. (Clark.) Alli-
gators are occasionally eaten by the Southern negroes. Lacertilia
are important in the extermination of injurious insects and some
species (iguana) are utilized as food. Ophidia are in general bene-
ficial in exterminating harmful rodents and insects. The poisonous
snakes are relatively few, but cause twenty-five thousand or more
deaths annually, most of them in India.

References on Reptilia

Barbour, T. 1926. Reptiles and Amphibians. Houghton Mifflin Co.
DiTMARS, R. L. 1907. The Reptile Book. New York.
DiTMARS, R. L. 1 9 10. Reptiles of the World. New York.
Reese, A. M. 191 5. The Alligator and its Allies. New York.
Surface, H. A. First Report on the Economic Features of the Turtles

of Penna. Zool. Bull, of the Dept. of Agr. of Penna., Harrisburg,

Aug. -Sept.
Surface, H. A. 1907. The Lizards of Pennsylvania. Bull, of the

Dept. of Agr. of Penna., Harrisburg.

CHAPTER XVIII

AVES

Birds are more highly specialized in structure and habits than
even the mammals. They, like the insects, are perfectly adapted to
flight. Geological records and some vestigial structures (scales)
indicate the close relationship of birds to reptiles.

So widely distributed are birds and so familiar to our sight and
hearing, that it is difficult to conceive of a civilization without them,
or what would happen to that civilization, did they not exist. Eco-
nomically, birds are of the greatest significance, since they not only
serve as food, but are the most important agencies in keeping
insects from utterly destroying the food of men. More than 23,000
species of birds have been described. They have been classified
according to types of bills and claws and in some cases from their
colors and habits. The classification is variable and unreliable.

Subclass I. Archeomithes. — Fossil birds.

The fossil, reptile-like birds belonging to the genus Archeopteryx
are quite evidently connecting types between the reptiles and the
birds. (See Fossil Relatives of Birds, page 370.)

Subclass II. Neomithes. — Recent birds.

Among the more recent birds, there are two Orders that exist as
fossils, and will be described later, under the heading of Hesper-
ornithiformes, and Ichthyornithiformes. (See page 371.)

The remainder of the Subclass Neornithes will be arbitrarily
divided into two divisions, the running birds, called Ratitae, and
the flying birds, or Carinatae.

Natural History

Division A. The Ratitae

The Ratitae are the running birds with reduced wings. Exam-
ples: ostrich, emu, cassowary, rhea.

Characteristics. — i. Raft-like or keelless breast bone.

2. Wings rudimentary or not large enough for flight.

3. Foot two-toed, large leg fitted for running.

334

AVES 33 s

The ostrich reaches a height of 6 to 8 feet and may weigh 450
pounds. Its single stride when running is 25 feet and it runs 60
miles per hour, but in circles, and is easily caught. It uses its two-
toed feet in defense and can kick a horse to the ground. Ostriches
do not hide their heads in the sand, but they do thrust them into
the sand in search of water which they frequently find. The eggs
are said to contain as much food as 24 hens' eggs. African savages
utilize the egg shells as containers. Ostrich plumes are extremely
valuable or less so according to the fashion dictated by milady.
High tariff, overproduction, and post-war depression, caused the
price of feathers to drop from I14 to less than $4 a pound. There
are now about 250,000 birds on African ostrich farms. In the
United States, ostriches have been bred since 1882. The plumes are
plucked or clipped twice a year. (Figure 183.)

The emu is an Australian form next to the ostrich in size. It
lacks the ornamental wings and tail plumage of the ostrich. The
cassowaries inhabit Australia and the Malay Archipelago. They
have long silky plumage and live in thickly wooded regions. Some-
times they take to the water for bathing. The female cassowary is
larger than the male. Both sexes are black. The plumage is made
into rugs, mats and head ornaments. The r-heas, the New World
ostriches, live on the pampas of the Argentine Republic, Southern
Brazil, Bolivia and Paraguay. Their wings are better developed
than those of the ostrich. They flap them as they run.

The elephant birds, now extinct, were existent in Madagascar
400 years ago. They were flightless and about 7 feet tall. Their
eggs, found in Madagascar, are 13x9 inches with a capacity of two
gallons. A single Aepyornis egg was equal to 12 ostrich eggs, 288
hens' eggs, or 500,000 humming-bird eggs. The natives of Mada-
gascar claim that elephant birds are still left in the interior, but this
is doubted. The 7noa {Dinorthiformes), now extinct, lived in New
Zealand 500 years ago. It was like the ostrich, but with heavier
bones and rudimentary wings. The kiwis of New Zealand belong
to the genus Apteryx, and are not completely wingless. They are
probably related to the cassowaries. Their voice is a shrill sound —
KI-WI. The nostrils are at the tip of the bill. The male incubates
the eggs which are about one-fifth the body weight of the bird.

Tinamousy which are found from South America to Mexico, are
classed by some authorities near the ostriches and considered
Ratitae; while others class them as an aberrant family of the order

33^

AVES

J^

Fig. 183. Group of Ratite birds. J, Rhea, R/iea americana; B, the Kiwi,
yipteryx australis; C, Cassowary, Casuarius uniappendicidatus; D, Ostrich, Struthio
camelus; E, Emeu, Droaemus novae-hollandae. (Newman, Vertebrate Zoology. Re-
drawn after Evans. Courtesy of The Macmillan Co.)

AVES 337

Galliformes, among the Carinatae. The wings are short and
rounded; the keel of the sternum is well developed and the pectoral
muscles large. The tail feathers are reduced. Strong, swift run-
ners, they can rise, after considerable effort, to 150 feet and fly or
plane a thousand yards. Probably the tinamous represents an
intermediate condition between the flying birds and the running
or flightless birds.

DivisioN^ B. The Carinatae

The Carinatae include most of our common flying birds.
Characteristics. — They have a keeled sternum and are for the
most part fliers.

Classification (Modified from the A. O. U. Check List).—

Order i. Pygopodes — auks, grebes and loons, penguins.

Order 2. Longipennes— gulls and terns.

Order 3. Tubinares — petrels and albatross.

Order 4. Steganopodes — frigates, cormorants and pelicans.

Order 5. Anseres — wild geese and swans.

Order 6. Odontoglossae — flamingo.

Order 7. Herodiones — storks, herons, ibises, and spoon-bills.

Order 8. Paludicolae — cranes, rails and coots.

Order 9. Limicolae — plovers and snipes.

Order 10. Gallinae — pheasants, pea-fowls, chickens, turkeys.

Order 11. Columbae — pigeons and doves.

Order 12. Raptores — hawks and owls.

Order 13. Psittaci — parrots and parokeets.

Order 14. Coccyges — kingfishers and cuckoos.

Order 15. Pici — woodpeckers.

Order 16. Machrochires — humming birds, swifts, nighthawks, and

whip-poor-wills.
Order 17. Passeres — flycatchers, larks, jays, orioles, and grackles.

Order 1. Pygopodes. — Looyis are large, often 24-28 inches long,
and the most expert diving birds. Their cry is weird, laughing, loud
and melancholy, resembling the dying wail of a person. The small
European grebe is called the " dabchick " because it tucks its young
under its wings when it dives to escape enemies. Grebes resemble
penguins more than loons.

The " Great Auk" once abundant on the islands north of Scot-
land and near Newfoundland, has been killed off, feathers being the

338

AVES

chief attraction. The eggs have been collected, resulting in no
evidence of their presence, other than bones. The last living speci-
men was seen in 1844.

The penguins (Figure 184), marine birds found in the Antarctic
seas, have paddlelike wings which work from the shoulder in a rotary
fashion. The legs are set far back, and the feet are used for
steering, not propulsion. Penguins have almost waterproof feathers.
Their plentiful subcutaneous fat produces a marketable oil. The
male aids in incubating the eggs which require 6 weeks to hatch,
and the young are blind.

Fig. 184. Galapagos penguin. (Courtesy of N. Y. Zool. Soc.)

Order 2. Longipennes. — Gul/s (Figure 185, A and B) are
aquatic, mainly oceanic, of medium size, with long pointed wings
and webbed feet. They are scavengers of the ocean, feeding from
the surface. Terns are more active than gulls. Their bodies are
slender and they have long-forked tails and pointed bills. They
nest on islands in colonies.

Order 3. Tubinares. — The petrels , " Mother Carey's Chick-
ens," are widely ranging sea birds of moderate size with long narrow
wings and a hooked bill. The " stormy petrel," the smallest of

AVES

339

web-footed birds, Is deemed a prophet of rough weather. The
albatross^ immortalized by Coleridge in his " Rime of the Ancient
Mariner," is one of the largest of the flying birds with a wing stretch
of from twelve to fifteen feet and may weigh twenty pounds. It
is able to fly and soar for hours. The gannets are sea birds fre-
quenting the colder regions, coming ashore during stormy weather.

— JUk^.

Black Tern

=■ fa-*

Herring Gull

Fig. 185. A, black tern. 5, herring gull. (From L. A. Fuertes. Courtesy of

Slingerland-Comstock Publishing Co.)

Order 4. Steganopodes. — The cormorants are large sea-coast
birds. They are voracious fish eaters, coming to inland lakes during
the breeding season. The Chinese tame them and use them in
catching fish. The darters or " snake birds " are not marine, but
frequent inlets of the sea and fresh water lakes. They excel as
divers, but are poor flyers. The frigate birds or " man-of-war
birds " are true sea birds, only coming to shore to nest. They have
long wings, and an extremely long tail. Their legs are weak, but
they are remarkable flyers. The pelicans are large tropical birds.
The large bill and lower jaw are provided with large pouches in
which are stored fish. They are known to many by their stubby tail
and short legs. (Figure i86.)

Order 5. Anseriformes. — The swans are large birds, graceful in
form and movement. They are pugnacious and quarrelsome.
Their voice is " like a blast from a French horn," but musical when
given by a large flock in chorus. The trumpeter-swan is white.
The geese are intermediate between swans and ducks in some
characteristics, especially in the length of the neck. (Figure 187.)
Some ducks are feathered brilliantly. One of the most handsome

340

AVES

is the male mandarin duck. Diving birds can remain under water
about one minute. Eider ducks are natives of the north and are the
best known and most valuable of the duck family. Many eider
ducks are slaughtered to secure the much prized breast feathers,

Fig. 1 86. Pelican. (Courtesy of E. R. Sanborn and N. Y. Zool. Soc.)

" eider-down." The mergansers^ or fish ducks, differ from true
ducks in having more slender bodies, grebe-like necks, and long
compressed bills with serrated edges. They are fish eaters and
hence not as edible as other ducks, but are much sought by hunters
on account of their " quick-get-away." (Figure 187, A^ B, C, D.)

Order 6. Odontoglossae. — Flamingoes are large, long-legged,
long-necked birds with pink plumage. They are good flyers, but
are better known as waders. They scoop up fish and shell-fish,
straining them out as the water and mud pass through holes in the
lower part of their beak.

Order 7. Herodiones. — Herons, ibises, and storks bear a strong
resemblance to one another. The ibis fed on snails in the Nile,
and was worshipped. (See Schistosoma, page 77.) The long legs,
collapsible necks, and flapping wings of storks are well known to
all children. The stork migrates long distances. (See p. 366.)

AVES

341

The spoonbill is stork-like with a spoon-shaped bill that easily
captures insect prey, larvae, fish, frogs, etc. It is found in the trop-
ics. The tropic birds are found in the tropic oceans, flying hundreds
of miles from land and taking refuge on ships or floating debris.
(Figure 188.)

Fig. 187. A, black duck. 5, Canada goose. C, greater scaup. D, mallard ducks.
(From L. A. Fuertes. Courtesy of Slingerland-Comstock Publishing Co.)

Orders. Paludicolae. — The sandhill crane is the most abun-
dant and largest of this species found in America. The great
bustard is the largest of European birds, being about 45 inches long
and weighing about 30 pounds. It looks like a goose, but has a
head and bill resembling the crane. The sun bitterns are small, like
the rails, with short legs, thin neck, a large head and a long, pointed
bill. The head is sunk on the body, when at rest, giving the bird a
neckless appearance. The rails resemble the quail and the plover.
(Figure 188, A, B, C, D.)

Order 9. Limicolae. — The Limicolae are marsh and shore birds,
with long necks, long slender bills, rather long slender legs, short tails

342

AVES

and wings. They are usually brown or gray, with blotches of white.
The hind toe is, with one exception, lacking or extremely short.
There are about 75 species of these mud-dwellers in the United
States.

Fig. 188. y/, great blue heron. 5, night heron. C, killdeer. D, ring-necked plover
(From L. A. Fuertes. Courtesy of Slingerland-Comstock Publishing Co.)

The phalaropes are small in size with lobed toes. The female is
more brilliantly colored than the male (which is uncommon in birds)
and does the courting. The male incubates the eggs. The -plover,
or killdeer, is one of the most beautiful of the shore birds, being
found along inland pools and ponds. The American golden plover
is found along the seashore and frequenting the banks of tide pools.
It migrates tremendous distances. (See p. Z^(y^

AVES

343

Other members of this order are the American woodcock^ with its
long sensitive, probe-like beak, used in procuring earthworms; the
Wilson's snipe, the sandpipers, and the curlews.

Order 10. Gallinae. — This order includes two families of un-
familiar birds, the brush turkeys {Megapodes) of Australia and New
Guinea and the curassows and guans ( Cracidoe) of tropical America.

Fig. 189. //, snipe. 5, spotted sandpiper. C, bob white. D, spruce grouse. (From
L. A. Fuertes. Courtesv of Slingerland-Comstock Publishing Co.)

The Gallinaceous birds include the common fowl and game birds
such as wild turkeys, grouse, partridges, bob-whites, and ptarmigans.
The most highly specialized types are characterized by brilliant
plumage, being the males of the golden and Lady Amherst pheasants,
native to South China and Eastern Thibet.

The common bob-white or quail \s> an extremely important weed-
seed and insect destroying bird. The rufed grouse are strong flyers
and their flesh is extremely palatable. Ruffed grouse are susceptible
to the disease tularemia. Wild turkeys are still found in the East,

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AVES

in Pennsylvania and West Virginia. Ptarmigans turn snow white
in winter. Pea fowls are oriental birds, domesticated all over the
world.

There are four distinct species of the jungle fowls ^ all native to
the jungles of the Indo-Malayan regions. The domestic fowl has
come from the red jungle fowl of this species. The black breasted
game fowl ho.?, retained more than the others the original characteris-
tics of its ancestors. The most different from the primitive is the
Japanese tosa fowl, in which the tail feathers have been known to
reach a length of fifteen feet, and also the Cochins, with their short,
plump appearance and feathered shanks. (See p. 494, Domesti-
cated Animals.) The Greeks were addicted to the sport of cock-
and quail-fights. The Chinese and Malays still have quail-fights.
(Consult D'A. W. Thompson, " A Glossary of Greek Birds."
Oxford, 1895.)

Order 11. Columbae. (Pigeons, doves.) — The dodos, recently
extinct, were large, peculiar looking pigeons. Pictures of them, and
their bones, prove them to be odd looking, short, plump with an
eagle-like beak and very little plumage. The true pigeons are a
. large family widely distributed * The best known are the carrier

/\ pigeons, rock pigeons and the great crowned pigeon. The rock
pigeon or rock dove is the species from which most fancy breeds of
domestic pigeons have come. When they are allowed to interbreed
freely the offspring revert to the characters of their wild ancestors.

Homing pigeons were used by the Greeks who probably learned
the art of training pigeons from the Persians. The Sultan estab-
lished a message system using pigeons, which lasted in Bagdad from
1 150 to 1258. Homing pigeons were used in transmitting mes-
sages by the Roman general Decimus Julius Brutus who was then
besieged by Mark i\.ntony. During the World War the combatants
used over five hundred thousand homing pigeons, the American
Army utilizing twenty thousand. Our homers are equipped by the
Signal Corps with " pigeon whistles " to frighten away hawks.

The passenger pigeons (Figure 190) once lived in flocks of
enormous numbers. Wilson, an early American ornithologist,
estimated one flock to include two billion individuals.'* The last
passenger pigeon, hatched in the Cincinnati Zoo, died there on

*A town in Michigan marketed (1869-1870) in two years 15,840,000 pigeons.
Hornaday. (Our Vanishing Wild Life.)

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345

September i, 1914, at the age of twenty-six years. The passenger
pigeon had a pointed tail and nested several feet from the ground.
The mourning dove is a beautiful bird, and although it has a
square tail is sometimes confused with the passenger pigeon. It is
an important enemy of weed seeds. It nests on or near the ground.

Fig. 190. Passenger pigeons. (Courtesy of Field Museum of Natural History.)

Order 12. Raptores. — Eagles, hawks, falcons, owls and condors
are characterized by hooked sharp beaks, strong talons, large crop
and markedly predaceous habits.

The golden eagle has dark brown plumage. It is nearly one
yard long, with a wing spread of nearly seven feet. It destroys
poultry, young deer, and small mammals. It is still found in the
Rockies. The American^ or " bald " eagle^ our national bird, has a
white head and tail in its fourth season. It lives along rivers and
feeds on fish, although it is not above the occasional capture of a
lamb. (Figure 191.)

The sharp-shinned hawk and Cooper s hawk (Figure 192) are
the common hawks most responsible for the loss of game and poultry,
while the duck hawk is extremely destructive to water fowl.
Sparrow hawks and pigeon hawks are important enemies of the
English sparrow, and beneficial rodent exterminators, but attack
some valuable birds.

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The American goshawk^ a native of Canada, coming to the
United States only in the winter, is a bold destroyer of game birds,
especially the ptarmigan. It has been known to escape with a
freshly killed chicken or even to follow the owner into the house and

Fig. 191. Eagle family. The female is ripping up a fish to feed to her three
eaglets, whose white heads are ranged before her. The inbending of the left foot of
the male, seen taking off in the air, was due to an old wound. He was wantonly killed
in the following November. Vermilion, April 27, 1924, at about six in the evening.
By F. H. Herrick. American Eagle Series of Western Reserve University.

snatch it from the table (Fisher). It reaches a length of twenty-five
inches. The ancient sport of falconry is being revived somewhat
abroad and in the United States, and goshawks are the favorite
" falcons." In Turkestan, sparrow-hawks, goshawks, buzzards,

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kites and eagles have been used in falconry tor centuries. Golden
eagles are used to hunt foxes for their pelts.

Fig. 192. Young Cooper's hawk. (Courtesy of W. E. Rumsey and A. J. Dadisman.)

References on Falconry

Blanc, M. E. 1895. Hunting with birds of prey. Pop. So. Men., vol.

47, no. 6, pp. 818-823, Oct.
FuERTES, L. A. 1920. Falconry, the sport of kings. Nat. Geog., Dec.
Goodman, G. G. 1929. Falconing. Nat. Hist., July-Aug.
Lattimore, O. 1929. The desert road to Turkestan. Nat. Geog.,

June.

The Turkey buzzard (see Figure 193 C), seen in most of the
Southern States, is valued by man on account of its importance as a
scavenger. Laws once existed in some Southern States protecting
the buzzard. It is suspected of carrying the germs of hog cholera.

The Andean condor^ the Caltforntan condor and the king vulture^
all members of the group Falconiformes, are notable in their ability

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to soar for hours. This capability has baffled physicists interested
in the problems of aviation.

The secretary birds are the strangest of the birds of prey. They

Fig. 193. A, red-tailed hawk, 5, osprey or fish hawk. C, turkey buzzard.
D, great gray owl. (From L. A. Fuertes. Courtesy of Slingerland-Comstock Publish-
ing Co.)

are long-legged, standing about four feet high and with great speed-
ing ability. They are fond of snakes, but will eat lizards, frogs,

AVES 349

and insects. Distending a stiff wing, they receive the bite of a
snake, stun the reptile and kill it.

There are eighteen species of owls in the United States. Among
the commonest forms are the barn owl, the long-eared owl, the barred
owl, the great gray owl — an Arctic bird never found south of the Ohio
River, and the screech owl. The great horned owl, sometimes called
the " tiger of the air," is a bloodthirsty game killer. Besides killing
poultry, it is of great importance as a destroyer of rodents. It is
the only owl that can be considered an enemy of man. The snowy
owl comes from the Arctic zone to the Northern part of the United
States in the winter. It feeds upon wild game and rodents, but
avoids poultry yards. The bun-owing owl is found in prairie dog
holes in the Southwestern states. It does not prey upon the " dogs "
but avoids them and their companions (?) the rattlesnakes. Bur-
rowing owls are able to dig their own holes, and certainly do not
go down into homes already occupied.

Order 13. Psittaci. {Paj-rots and paroquets.) — The parrots are
brilliantly colored with great ability to mimic. They live to a great
age (seventy-five years) and learn to talk quite readily. At times
they display remarkable memory for certain expletives uttered by
their owners in moments of stress. The African Gray parrot with
a red tail is the best talker. The brush-tongued parrots, found in
Australasia, have an odd " brush " at the end of the tongue, adapted
to feeding on honey. The paroquets are extremely small parrots
found in the United States, in Florida. They feed on fruit and seeds.
The macaws are large scarlet and blue birds with long pointed tails
and horrible voices. The hyacinthine macaw of Brazil feeds on
nuts of the palm, macuja, crushing them by means of its powerful
beak. The cockatoos are usually snow-white, with long triangular
erectile crests. They are frequently trained for vaudeville exhibi-
tion. A giant black species from New Guinea with a slender
cylindrical tongue, and an enormous beak, is able to open the
excessively hard " canary nut."

Order 14. Coccyges. — The cuckoos are best known from their
peculiar habit of placing eggs in other birds' nests. Instead of
building a nest of her own, the female lays the egg on the ground,
then carries it in her bill to some other nest. This parasitic habit
belongs to the Old World Cuckoo, for the American cuckoo builds
its own nest.

The Coraciae are sub-orders having affinities with the cuckoos

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and the sparrows. They include the kingfishers and the horn-bills.

The horn-bills are large birds using their enormous bills in wall-
ing up nests. The male seals up the female in a hollow tree, feeding
her through a small aperture. The kingfisher family includes three
species in the United States. It nests in a hole dug horizontally
into a bank of earth. Its food consists almost entirely of small
fishes. The belted kingfisher is an enemy of trout and other fry
at fish hatcheries.

Order 15. Pici. — The woodpeckers and sapsuckers are the most
familiar of our native birds. There are about twenty-five species
of American woodpeckers. The flicker, or golden-winged wood-
pecker, is a large bird which perches crosswise on limbs like the
true perchers. It is also called the " yellow hammer " or "high-
hole." Its stomach contents show over fifty per cent insect food,
about forty per cent vegetable food, chiefly berries and seeds. The
red-headed woodpecker, immortalized in Longfellow's " Hiawatha,"
is a showy creature with a brilliant crimson head and neck, white
breast and black back and tail. Its food consists of ants, beetles,
weed-seeds and fruits. It is particularly fond of beech-nuts. The
downy woodpecker and the hairy woodpecker consume about seventy-
five per cent insect food and about twenty-five per cent vegetable
food, mostly weed-seeds and wild fruits. The yellow-bellied sap-
sucker injures trees by girdling them. It drinks the sap exuding
from its neatly formed squarish holes. In New England some
orchard owners protect their trees with fine wire netting. This
form is the most migratory of our woodpeckers. Toucans have
enormous bills which, however, are extremely thin and light in
weight.

Order 16. Machrochires. — The Machrochires Include the whip-
poor-will, night hawk and chimney swift which are exceedingly
valuable as enemies of both day and night flying insects. (Figures
194 and 195.)

The humming-birds feed on insects and spiders and on the sap
of trees in holes prepared by the sapsucker, as well as upon the
nectar of flowers. Humming birds, although small, are exceedingly
brave and pugnacious, and one pair of them will attack and drive
to flight hawks and large snakes. The swifts are less attractive
than humming birds and are often mistaken for swallows. They
have a broad bill and wide mouth like the goat-suckers.

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Fig. 194. Rufous hummingbird on nest. (Photo by W. L. and Irene Finley. Cour-
tesy of National Park Service.)

Fig. 195. Nest and eggs of ruby-throated humming bird. (Courtesy of Fred E.

Brooks.)

Order 17. Passeres. — This is the largest order of birds, con-
taining over half the species. As the name indicates the forms are
perching birds. The birds of paradise are the most brilliantly
colored of the order. The great bird of paradise is the most beauti-
ful of the species. The lyre-birds rival the birds of paradise in
plumage construction, but are not so brilliant.

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The blue-birds, robins and the thrushes {Fam. Turdidae) are
important enemies of insects and worms. Robins are a bit injurious
to cherries, since the dietary change offered by these (acid) fruits is
so welcome to them. The chickadee {Fam. Paridae) is an extremely
important enemy of insects, including aphids (plant-lice) and canker
worms.

Fig. 196. J, kingbird. B, wood thrush. C, chimney swift. D, horned lark.
(Courtesy of Slingerland-Comstock Publishing Co.)

The crows and jays {Fam. Corvidae) number over two hundred
species. They eat fruits, insects, seeds and the eggs and young of
other birds.

The king-bird., the phoebe and the fly-catchers, crested and least
{Fam. Ty7~annidae),2iX^ all extremely important insect destroyers.

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The king-bird, however, is said to be an important enemy of honey-
bees.

Black-birds and orioles {Fam. Icteridae) are among the most
beautiful of birds. The boboUyik of the south is an enemy of rice
fields. In the north it is considered one of our sweetest singers.
The orioles are extremely beautiful birds with peculiar nests hanging
down considerable distances from boughs. The cow-bird has the
habit of laying its eggs in the nests of other birds, particularly
sparrows and warblers.

Fig. 197. Young brown thrashers. (Courtesy of G. H. Roush.)

The sparrows znd finches {Fam. Fringillidae) are all important
destroyers of weed-seeds. The English sparrow, however, which
was introduced into America in 185 1 has proved a menace to the eggs
and young of our beneficial tree swallows.

The shrikes or butcher birds {Fam. Laniidae) are important
enemies of English sparrows and rodents, but on account of their
habit of killing the small forms like the chickadee and the wren,
must be considered injurious. They impale the bodies of their
victims on twigs.

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The swallows {Fam. Hirundinidae) are extremely efficient insect
destroyers. Their relatives, the purple martins^ will readily take
up their abode in bird houses. The mocking-birds, thrashers and
wrens are beautiful singers and important enemies of insects. The
warblers {Fajn. Mniotilitidae) include over one hundred species,
about seventy-five of which are found in the United States. They
are important enemies of insects.

Fig. 198. Whitebreasted nuthatch. (Courtesy of F. E. Brooks.)

The Anatomy and Physiology of Birds

No animal has feathers except the bird. " A bird is known by
its feathers." Every part of the organization is modified for aerial
life.

Characteristics. — i. Feathers.

1. Sternum and shoulder girdle enlarged to support wing mus-
cles.

3. Forelimbs modified as wings.

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3SS

4. Pelvic girdle and hind limbs adapted to support the body on
the ground.

5. Respiratory system developed to produce a higher tempera-
ture than in any other animal.

6. Absence of teeth.

7. Loss of the left aortic arch.

8. Right ovary and oviduct lost.

9. Poorly developed olfactory organs.

10. Extraordinary development of the eyes.

Temperature ^ is lower in most lowly organized birds. There is
a progressive gradation to the higher birds. The apteryx or kiwi, a
wingless bird of New Zealand, has a temperature of 37.9° C. (100.2°
F.). The emu, cassowary and penguin have a temperature of
39.° C, the sparrows and warblers from 42° C. to 44° C. (107.6°
F.), the common fowl, 40.6° C. The average of sparrows is 109.9°
F., which is 10° above the temperature of man. (Figure 199.)

Feathers have a hollow, transparent barrel, or quill, continuous
with the shaft or rachis. The shaft is opaque, quadrangular in
cross section and filled with a pithy substance. From the shaft
above the quill arise lateral branches, known as barbs or rami.
Barbs give off barbules and these in turn give off the barbicels
which are hooked processes. The hooked processes produce the
web and furnish it strength to resist or act upon the air. From the
underside of some feathers at the juncture of the quill with the web-
bearing portion is a secondary feather, the after shaft. There are
three kinds of feathers: (i) Contour feathers (complete). (2)
Down feathers, soft shaft, no barbs, serve to retain heat. Some
have no shaft. (3) Filoplumes, degenerate, hairlike with few or no
barbs.

Feathers are derived from cornification of the inner layer of the
epidermis. The papillae consist of external epidermis and internal
dermis, the latter furnishing nutriment to the growing feathers.
Epidermal scales of the birds arise similarly from papillae.

Birds shed their old feathers. They molt in the fall and have a
partial molt in the spring b7-eeding-season. They acquire a new set
of feathers from the follicles. Some also shed parts of their claws,
bill and bill membranes. (Figure 200.)

^ For further data on temperature and color, see Knowlton's Birds of the World.

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Color. — (i) The chemical absorption colors have coloring matter
as a pigment or coloring solution. Colors thus produced are black,
red, brown, orange and yellow, rarely green, and never blue. Certain
red birds (plantain eaters, Miisophagidae) lose their red color in the
rain but regain it when dry. The pigment (turacin, a copper salt)
stains the water into which the animal goes for a bath.

Fig. 199. Forms of beaks. After Claus. Forms of beaks {a, b, c, d, k, after
Naumann; g, i, m, 0, regne animal; /, from Brehm): a, Phoenicopterus antiquorum; b,
Platalea leucorodia; c, Emberiza citrinella; d, Turdiis cyaniis; e, Falco candicans; f,
Mergus merganser; g, Pelecanus perspicillatus; h, Recurvirostra avocetta; i, Rhynchops
nigra; k, Columba livia; /, Balaeniceps rex; m, Anastomos coromandelianus; n, Ptero-
glossus discolor; 0, Mycteria senegalensis; p, Fakinellies ignetis; q, Cypselus apus.
(From Daugherty. Courtesy of W. B. Saunders & Co.)

(2) Another type of color production is by means of pigment
combined with structural peculiarities, such as ridges and furrows
in the surface of the feather itself. Thus we find produced blue,
green usually, sometimes yellow. In transmitted light, feathers
with these colors show the color of the pigment.

(3) Metallic colors are found in the humming birds, dove, grackle,
starling, and peacock. The commonly accepted hypothesis is that

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357

77ietallic colors are due to the structure of the surface of certain parts
of the feathers such as striae^ ridges, knobs or pits, in combination
often with an extremely colorless layer, these elements acting as
prisms. Dr. R. M, Strong believes that in the pigeon the metallic
colors of the neck feathers are due to spherical granules of the trans-
parent wall and terms them " plate interference colors " or New-
tonian rings. Feathers are found only on certain feather tracts
which differ in different species of birds.

Fig. 200. Foot forms, a, semi-palmate, wading of Ciconia; b, perching of Turdus;
c, rasorial of Phasianus; d, raptorial of Falco; e, adherent of Cypselus; f, cursorial of
Struthio; g, zygodactyl (scansorial) of Picus; h, lobate of Podiceps; i, lobate and
scalloped of Fulica; k, palmate of Anas; I, totipalmate oi Phaethon. (From Schmarda.
Hertwig-Kingsley. Courtesy of Henry Holt & Co.)

Skeleton. — The forelimbs and pectoral girdle (Figure 201) are
modified for flight. The skeleton of the limb is rigid. The hind
limbs and pelvic girdle are used for bipedal locomotion. The
skeleton is permeated by air usually in ratio to the mode of life.

(i) Condors and cranes, soaring birds, have lightly built skele-
tons. (The snipe and the curlew have airless bones, but fly long
distances.)

(2) Ducks and other water fowls have cavities of the long bones
filled with marrow.

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Fig. 20I. Skeleton of an Egyptian vulture. Rh, cervical ribs; Du, inferior
spinous process of the thoracic vertebrae; CI, clavicle; Co, coracoid; Sc, scapula; St,
sternum; Stc, sternocostal bones (sternal ribs); Pu, uncinate process of the thoracic
ribs; % ilium; Js, ischium; P^, pubis; H, humerus; R, radius; U, ulna; C C, carpus;
Mc, metacarpus; P' P" P'", phalanges of the three fingers; Fe, femur; T, tibia; F,
fibula; Tm, tarso-metatarsus; Z, toes. (Claus-Sedgwick. Courtesy of Macmillan and
Co., Ltd.)

AVES 359

(3) Bones of strictly aquatic birds are solid, being filled with
bony tissue. The presence of air in the bones is believed to aid in
oxygenizing the blood and in adjusting the air pressure when a bird
descends rapidly from a great height.

A fossilized wing of a pterosaur recently sent to the U. S. National
Museum from Oregon was so perfectly preserved that it was possible
to determine the character of the bones. Instead of being hollow
as in our modern fliers, the cavities of the bones were filled with light
spongy tissue which served to strengthen them.

Digestive System. — The mouth is without teeth. (Vestigial
teeth are present in some parrots.) The tongue is of various types:
(i) Pointed, in the pigeon; (2) Long and protrusible, in the wood-
pecker; (3) Short, in parrots; (4) Sucking tubes, in the humming
birds.

In birds we find that swallowing consists of violently jerking the
head with an accompanying tongue pressure. There is no soft
palate, and no epiglottis is present, but the larynx is protected by
retroverted papillae at the base of the tongue. Insectivorous birds
have a pouch at the base of the throat. In the nutcrackers there is
a goitrous swelling in the throat, where the animal stuffs itself with
nuts. The pelican's enormous bill holds 10 quarts of water.

The upper part of the esophagus has buccal glands, sometimes
called salivary glands, used to moisten the food. The crop is a non-
glandular sac in which the food is softened and macerated. Animal
food may remain in the crop for 8 hours, and vegetable food may be
retained for from 16 to 20 hours. Fruit and insect eating birds
have no crop. The pigeon has a double crop. " Pigeon's milk " is
formed in the o'op and consists of proteins and oil, with no casein
and no sugar of milk. It is a milky appearing fluid which mixes
with macerating grains and is regurgitated for the young. The
toucan regurgitates and chews over its food. The indigestible parts
of the prey of the owl are regularly " cast " or regurgitated from the
stomach. The lower part of the esophagus is a continuation from
the crop to the stomach. The proventriculus has glandular walls,
its gastric follicles secreting gastric juice. (Figure 202.)

The gizzard is thick and muscular, and is used to grind food.
It corresponds to the pyloric end of the mammalian stomach.

The triturating agents are hard foreign bodies such as sand and
gravel. Pigeons and other gallinaceous birds carry gravel to their
young. It is necessary to have such in order to bruise the grains

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and allow the gastric juice to act. Fowls can pulverize glass and
some metals by grinding them in the gizzard.

The small intestine consists of the duodenum and the ileum.

Esophagus (upper portion)
Crop

Esophagus C/oiver portion)

Liver Co small portion)

Bile ductus
■Fttncreos
Proventricu/us

Gizzard

Spleen

Ceca
■Duodenal loop

Recturf)

Anus

Fig. 202. Digestive tract of common fowl. (Drawn by W. J. Moore.)

The duodenum has a U-shaped loop. This varies in different birds
but is ordinarily quite long and equal to twice the length of the body,
except in the fish eaters, where it may be but one-eighth the length

AVES 361

of the body. The ileum is not ordinarily long, but in the owls it is
nearly as long as the duodenum.

The rectal ceca are diverticula at the point where the ileum
enters the rectum. In the grebe, a single cecum in present. In
most birds there are two ceca, variable in length according to their
habits. In the pigeon the ceca are not more than 2 inches long
(shorter than in any other vegetable feeder) while in the common
domestic fowl, they may reach a length of 3 feet.

Rectum. — The large intestine (called the rectum rather than the
colon) is wider than the small intestine, and has coarse, short villi.
It terminates by a valvular opening in a dilated cavity, the remains
of the allantois (see page 302), now a rudimentary urinary bladder.
The ureters and generative ducts open into a transverse groove at
the lower part of the urinary dilation. The anal follicles are in a
conical glandular cavity communicating with the posterior part of
the cloaca and named the " Bursa Fabricii."

Liver and Gall Bladder. — There is usually a gall bladder, with
two bile ducts leading from the large liver to the duodenum. The
pigeon has no gall bladder but the fowl has an extremely large one.

Pancreas. — The pancreas is a compact elongated reddish gland
lying in the loop of the duodenum, into which it discharges its
ferments through three ducts. The three enzymes digest proteins,
carbohydrates and fats as in mammals (p. 432).

Circulatory System. — The heart is comparatively large. (Figure
203.) Two auricles are present and the two ventricles are com-
pletely separated. The right auricles receive impure blood from
the right and left precavals, and the postcaval veins. The blood
passes from the right auricle through the auriculo-ventricular valve
to the right ventricle. From the right ventricle it goes past the
semilunar valves to the pulmonary artery and thence to the lungs.
Four pulmonary veins from the lungs bring the blood to the left
auricle. From the left auricle through the mitral valve it passes to
the left ventricle. From the left ventricle it passes the semilunar
valves to the right aortic arch ^ which gives off the innominate
arteries, then continues as a dorsal aorta. Venous and arterial
blood do not mix in the bird. The jugular veins are united by a

8 In the reptiles, the right aorta transmits pure blood, while the left aortic arch
contains mixed blood.

The pigeon (Columba) has about 2,000,000 red corpuscles in a cu. mm. of blood.
Erythrocytes vary in size from 12.1 microns in the fowl to 14.7 in the pigeon.

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transverse vein so that if the head is turned around the blood can
still flow back into the heart through one of the jugular veins.

Grac/iiol artery

Srochio/ t^e/n

Subclavian artery

Vertebral vein
Vertebral artery

■Juqulor vein

Common carofi'd artery

Brachial artery.

Broctiia/ vein

.Lett pectorof
arteries and veins

__Internal mammary
artery and vein

— Left auricle -.

- J f

Rii^tlt precavat vein y /
Aortic arch
flight auricle
Post cava/ vein —

Riqtit ventricle "^

Hepatic veins

Reno/ artery
temorot artery

Afferent renal vein-^^=-^=S

t^emorol vein

Ffenal porta/ vein

3ciafic artery
Renal arteries

Dorsal aorta

Fig. 203. Heart of pigeon. (After Parker's Zootomy. Courtesy of Macmillan and

Co., Ltd.)

"^Left pulmonary artery
Left ventricle

—Coe/ioc artery
Dorso/ aorta
-Anterior mesenter/c artery

■Epiijastric vein

I/iac vein

Afferent renai vein

—f^emora/ artery

Femora/ vein
Renal vein

Respiratory System. — Air passes from the anterior nares or
nostrils through the posterior nares, pharynx, trachea, and bronchi
into the lungs and thence into from six to nine large air sacs. The
air is forced into the air sacs by passage through the air in flight
and out of them by wing compression. Hollow bones which render
them lighter in the air are found in the soaring birds.

Voice Box. — The syrinx is a structure found at the point where
the trachea divides into the bronchi. A flexible valve extends

AVES 363

forward at the point where the trachea divides. Muscles control
the tension of this valve and the number of vibrations and pitch
resultant are thereby regulated.

Bird Songs. — Call notes are heard throughout the year, but
songs, which Darwin believed to be associated with sexual selection,
are limited in most birds to the breeding season. (See page 515,
Sexual Selection.) The rhea and the ostrich are said to be mute.

References on Bird Songs

Allan, F. H. Some little known songs of common birds. Nat. Hist.,

vol. 22, p. 235.
Oldys, Henry. 191 7. The meaning of bird music. American Museum

Journal, vol. 17, February, pp. 123-126.
Saunders, Aretas A. Flight songs and mating songs. Auk, vol. 39,

p. 172.
Tyler, W. M. 1923. Courting orioles and blackbirds from the female

bird's eyeview. Auk, vol. 40, Oct., pp. 696-697.

Excretory System. — The kidneys are paired and ordinarily three
lobed. The first lobe is usually larger although in the pelican the
third lobe is larger. The tern has 7 or 8 lobes in its kidneys and the
eagle has four. No urinary bladder is present. A rudimentary
urinary bladder is found most highly developed in the ostrich, while
the owl, pelican, grebe and swan have small ones. The urine
solidifies on reaching the air.'' The adrenals (suprarenals), endo-
secretory glands regulating blood pressure, are rounded and yellow-
ish and found on the inner edge of the first lobe of the kidney.

Reproductive System. Male. — In the male, there are two testes
which vary greatly in size according to season. Two seminal
vesicles store the sperms. There are two vasa deferentia with
eversible papillae at the cloacal end. The Anatidae have a penis,
coiled when flaccid. The Cursores have a penis consisting of two
fibrous bodies with a fissure between. (Figures 204 and 205.)

Female. — In the female the right ovary is degenerated^ with a
vestigial oviduct. The left ovary persists and has a long convoluted
oviduct with a papilla at the end. The oviduct secretes albumen
in the upper part, farther down the shell gland secretes the shell
membrane and finally the posterior part secretes the shell. The

^ Great deposits of the feces and urine of certain birds are found in Peru. This
substance, rich in salts, is sold as the fertilizer, "guano." See page 368.

364

AVES

uterus Is considerably enlarged. Antiperistalsis of the oviduct
sometimes results in the formation of a new shell on an egg already
provided with one.

Ovory - with

ot/o of different siie

■Funnel of oviduct

•Kidney

-Oviduct

Ureter

Sfiell glared

-Rudimentary ritjflf
ov/duct
Vesicula s&niinolts \ \ \\ jl / /

Openinq of the areter\ \ \\ \\ / y^ Opening of ureter-

into tfie cloaca NsV'O^^^— ^5^/^ '"'" ''^^ clooca

Open.no of vas deferensfii^^ ^'^^ Opening of oviduct

,nto the clooca / ( j 1 ,„^„ ,^g cloaca

-Cloaca ^-Cr^ ~Z^^

Cloaco

Fig. 204. Reproductive system of the Fig. 205. Reproductive system of the
fowl, male. (Drawn by W. J. Moore.) fowl, female. (Drawn by W. J. Moore.)

Nervous System. — The brain is short and very broad. The
cerebral hemispheres are large and the optic lobes immense. The
cerebellum is extremely large, indicating well-developed equilibration.
The olfactory lobes are very small.

Sense Organs. — The bill and tongue are tactile organs; tactile
nerves are also present at the base of the feathers, especially the
wings and tail. The sense of synell is very poorly developed while
the sense of taste is poor but serviceable. Hearing is extremely
acute and vision is phenomenal. The eyes are very large and of a
biconvex shape. Birds have a tremendously developed power of
accommodation. They can swoop down to the water with great

AVES 2^s

rapidity and seize a fish which is unseen by a man standing on a clifF
above the water. Buzzards see a sleeping man and gather quickly.
Many a traveler has when ill been quite disconcerted by the sight
of buzzards gathered in his vicinity. Keen eyes enabled one of them
to note his quietude and others quickly gathered as the scout circled
downward. Whether the buzzard smells decaying flesh of dead
animals is a debated question. Experiments seem to indicate that
it sometimes does. Many zoologists are of the opinion that sight
Is the chief means of locating the buzzards' food.

Susceptibility of Birds to Poison.— Small doses of morphine
produce in birds disturbances of the digestive tract and a light sleep.

Types of Nests. — Birds' nests vary greatly in structure and in
location. Birds may deposit their eggs on the sand, unprotected,
or they may build a nest in an excavation in the ground or in a
hollow tree. Some forms seek out lofty eyries^ others build colonies
on the sides of cliffs, while still others build mounds. The mound-
building birds of Australia open the mounds to admit the sun and
remove or add debris as the humidity varies. The nests of others
float on stagnant pools or are built in the grasses of swamps and
meadows.

There is a great specialization in the material \x^Q.di in constructing
the nest. Some warblers line their nests with the seed capsules of a
certain species of moss. The tailor bird sews leaves together with
plant fibers. The tropical bower-bird includes bits of shell and bone
in its nest. The crow and the starling are particularly fond of bright
bits of metal. Stories are told of tame crows that successfully stole
table silver.

The chipping sparrow lines its nest with horsehair., while the
crested flycatcher usually Includes a portion of the cast skin of a snake.
As mentioned before, the South American hornbill male seals his
spouse Into her nest in a hollow tree and brings food to her during
the nesting period. The chimney swift builds its nest (In a chimney)
of twigs stuck together by saliva.

The edible birds' nests of the Orient are built by swift-like birds
{Collocalia) , in rocky caverns along the sea. The first nests built
are made up almost entirely of glutinous salivary secretion and are
sold for as much as $15.00 per pound. The first quality nests are
almost entirely destroyed by native collectors. Later nests con-
taining twigs and other foreign matter are not destroyed, or the
birds would soon be extinct.

266 AVES

One of the most beautiful of the birds' nests is that of the Balti-
more oriole. It is easily recognized by the long strand suspending it
a foot from its supporting branch. It is tightly woven and when the
bird is on its nest its weight closes the opening so that no rain can
enter. The South American cacique builds a nest similar to that of
the oriole and with a much longer anchor. It may hang seven feet
from a branch.

Bird Migration. — Coward classifies birds with respect to their
migrations as:

(i) Permanent residents; (2) Summer residents. (Leaving in autumn
and returning in spring); (3) Winter residents. (Leaving in the spring
for their breeding area); (4) Birds of passage — or spring and autumn
migrants; (5) Irregular migrants — occasional invaders; (6) Stragglers or
wanderers.

The American Golden plover nests along the Arctic coast from
Alaska to Hudson Bay; winters in Argentina, after a roundabout
oceanic flight of 2,500 miles, passing through Labrador and Nova
Scotia with rests and feeding at each of these places, then flies
directly across the sea to Guiana and thence after a further rest to
Brazil where it feeds until March. The return route is a more
direct one. The distance covered in the elliptical indirect route is
said to be nearly 20,000 miles. Birds usually migrate in company
with other experienced travellers, but they make successful pil-
grimages when it is evident that older birds are not there to guide
the flock.

Storks marked in Prussia have been taken in the African Trans-
vaal. The Arctic tern nests along the coast of Maine and North-
ward to the limit of land, but winters along the borders of the Ant-
arctic continent. Thus it migrates about 11,000 miles, probably at
sea. Cooke states that the Arctic tern has more hours of daylight
than any other animal. " The midnight sun has already appeared
before the birds' arrival at the Northern nesting site, and does not
set during their entire stay at the breeding grounds. During two
months of their sojurn in the Antarctic^ the birds do not see a sunset."
They have 24 hours of daylight for at least 8 months of the year.

Some species fly by day and some by night, others fly both day
and night. Some day-migrants follow coast lines or river valleys,
guiding themselves by sight. But in the case of the noddy and sooty
terns, studied by Watson and Lashley, birds liberated at sea, 600

AVES 367

miles from their nests and 450 miles from shore, and others liberated
on the mainland 850 miles away flew directly to the proper island
and nests.

Why Birds Migrate. — One of the commonly accepted theories as
to migration is that ages ago the United States and Canada were
occupied by non-mi gj-ato7j birds. When the Arctic ice fields moved
South during the glacial period, rendering the Northern half of the
continent uninhabitable, because of lack of food supply and a low
temperature, the birds migrated farther and farther each decade
until finally the racial habit of long migrations was established.
Another theory is that the birds' original home was in the South and
that as the ice retreated northward they sought a less crowded
breeding ground, only to return to their winter quarters in the South.

In some recent work done by W. Rowan of Alberta, Canada, the
factor of the physiological impelling force of the developing gonads
is emphasized along with the environmental factor provided by
varying day lengths.'^ Rowan says: " Migration cannot be looked
upon as an act of volition, but as the automatic response to a certain
physiological state probably induced by a gonadial hormone. The
birds must migrate if physically able to do so." Unquestionably
Rowan's point regarding the influence of the gonads is well taken.
(See Fish Migration, page 263.)

We know that birds have a time sense, and that the northerly
movement of the robin is correlated with the attainment of a certain
mean daily temperature. The average of weather conditions
influences the average time of arrival, and the flight of night mi-
grants is known to be correlated closely with meteorological condi-
tions. Adams found that bird migrants arrive in waves following
peculiar types of weather.

In spite of the evidence collected by many observers, there are
those who seem content, like many of the adherents of the " parent-
stream " theory in fishes, to dismiss the whole problem by stating
that it is probably due to a mysterious sense of direction.

Others have suggested that a peculiar physical property of the
feathers causes the magnetic pole to exert a powerful attractive
influence.

* In his studies on the sexual cycle of the European starling, Bissonnette has shown
that increased daily light periods will increase spermatogenic activity. Consult
Bissonnette, T. H., 1931 (Jour. Exp. Zool., vol. 58, pp. 281-319), and earlier papers.

368 AVES

Speed of Flight. — Migrating birds are able to reach a speed of loo
miles an hour and travel from i,ooo to 5,000 feet above the earth.
A carrier pigeon is recorded as having averaged fifty-five miles an
hour for four hours, probably exceeding the speed of most migrants.

Mr. Thomas Ross, who is in charge of the army lofts at Fort
Monmouth, N. J., is quoted (American Magazine, June 1928) as
stating that an American carrier pigeon flew 300 miles at a little
over seventy-one miles an hour. He also quotes the unsubstan-
tiated statement that a pin-tail duck has made 125 miles an hour.
Herons, hawks and flickers fly about twenty-five miles per hour.
According to Chapman, the great wandering albatross of the South-
ern Seas has been known to fly 3,400 miles in eight days.

Economic Importance of Birds. Positive. — i. The eggs and
flesh of the common fowl, ducks, geese, and even the ostrich, are
eaten.

1. Feathers of the ostrich, the egret and the bird of paradise
have been in times past great favorites for ornamentation.

3. The Chinese are extremely fond of the edible birds' nests
secured along the coast, north of Borneo.

4. From the Islands of the South Pacific comes the important
fertilizer known as guano. ^ This has been deposited for centuries.

5. As scavengers, the buzzards and vultures are especially
valuable.

6. Birds are preeminently our best friends in that they destroy
insects, rodents and the seeds of our most pestiferous weeds. The
English starling, until recently considered as great a pest as the
English sparrow, is, according to S. S. Pennock of Philadelphia, an
extremely successful hunter of the larvae of the Japanese beetle.

Negative. — i. Destroyers of poultry. Very few birds attack
domestic fowls. Several species of the hawks may be classed as
injurious, while the only owl that is injurious is the great horned owl.

2. Enemies of beneficial birds. The English sparrow, the
starling and the jay drive away other birds and the jay eats eggs
and young. The shrike or butcher bird is an important enemy of
our bird friends.

3. Destroyers of crops and fruits. The crow, the English spar-
row, the robin, and the grackle consume some of our food products.

' For further information regarding guano, consult: Murphy, R. C. 1924. The
most valuable bird in the world. Nat. Geog. Mag., vol. 46, p. 279, and Coker, R. E.
1920. Peru's wealth producing birds. Nat. Geog. Mag., vol. 37, pp. 537-566.

AVES 369

4. Disseminators of injurious seeds and parasitic animals.
Even our valuable game birds may be the means of dispersing
parasitic worms and protozoa, and it is a well-known fact that the
starling, introduced into New Zealand, spread the seeds of the
English blackberry, with the result that the thorny bushes form a
snare for lambs and interfere with cultivation.

References on Birds

Beal, F. E. L. and Others. 1916. Common Birds of S. E. United

States in Relation to Agriculture. Farmers' Bull. no. 755, U. S.

Dept. Agr.
Bradley, O. C. 1915. The Structure of the Fowl. A. and C. Black,

Ltd., London.
Chapman, F. M. 1910. Birds of Eastern North America. New York.
Chapman, F. M. 1903. Color Key to North American Birds. New

York.
Fisher, A. K. 1908. Economic Value of Predaceous Birds and Mam-
mals. Yearbook of the U. S. Dept. Agr.
FoRBUSH, E. H. Game Birds, Wild-Fowl and Shore Birds. Mass.

State Board of Agriculture.
FoRBUSH, E. H. Useful Birds and their Protection. Published by the

Massachusetts State Board of Agriculture.
Friedmann, H. 1929. The Cow Birds. C. C. Thomas Co., Springfield,

111.
Heilmann, G. 1927. The Origin of Birds. D. Appleton and Co., New

York.
Henshaw, H. W. Fifty Common Birds of Farm and Orchard.

Farmers' Bull. no. 513.
Kaupp, B. F. 1 91 8. The Anatomy of the Domestic Fowl. W. B.

Saunders Co.
McAtee, W. L., and Beal, F. E. L. Some Common Game, Aquatic,

and Rapacious Birds in Relation to Man. Farmers' Bull. no. 497.
Mentor. 1913. Game Birds of America. Vol. i, Oct. 6, no. 34.
Mentor. 1916. American Birds of Beauty. Vol. i, June 2, no. 16.
National Geog. Mag. 1914. 64 Pictures in Colors of Common Birds

of Town and Country. Vol. 25, May.
Thomson, J. A. 1923. The Biology of Birds. The Macmillan Co.,

N. Y.
Weed, C. M., and Dearborn, N. Birds in their Relation to Man.

J. B. Lippincott Co., Philadelphia, Pa.

37°

AVES

Fossil Relatives of the Birds. Saururae. — These reptile-like
forms had a long, slender, lizard-like tail, sharp teeth, a short neck,
a small keel to the breast bone and claws on the fingers and toes.
Two specimens were found in the Jurassic of Bavaria. The
Archeopteryx (Gr. ancient wing) was discovered in 1861 at Solen-

FiG. 206. Archeopteryx as it would appear with feathers restored. (From Romanes,
Darwin and After Darwin. Courtesy of Open Court Publishing Co.)

hofen, Bavaria; (Figure 206.) It had been so well preserved be-
tween the layers of lithographic slate that the details of feathers of
the wing and tail were plainly seen. It had a bird-like head and
brain. Its jaws were, however, equipped with sharp reptilian teeth.
The head and neck were devoid of feathers while the legs had quill
feathers. The wings had three fingers with reptile-like claws, with

AVES

371

the metacarpal bones separated. The fingers had the same number
of joints as in the lizards. The keel was only lightly developed.
Archeopteryx used its wings chiefly for planing rather th.B.n flying.
The Archeornis (Gr. ancient bird), slightly different from the Arche-
opteryx, was discovered in an almost perfect state of preservation
in 1877, "6^^ Eichstatt, Bavaria. It had an extremely long reptilian
tail with twenty-one joints, which was " Hke a telescope pulled out,
while the tails of the modern birds are like a closed telescope."

Fig. 207. Left, Ichthyornis victor. Right, Hesperomis regalis. (From Daugherty.

Courtesy of W. B. Saunders & Co.)

Ichthyornithiformes. — Ichthyornis (Figure 207 A) had socketed
teeth, a keeled sternum and was a strong flyer and apparently a fish
eater. It was found in the Cretaceous of Kansas. It was small,
about the size of a pigeon.

Hesperornithiformes. — Hespej-ornis (Figure 207 B) was a three-
foot, flightless diving bird, with grooved teeth, a keelless sternum
and strong paddle-like hind limbs. It was also found in the Creta-
ceous of Kansas.

A Living, Connecting Type. — In the South American Hoactzin,
the adults are like certain pheasants, but differ in anatomical
characteristics. The breast bone is wider behind than in front; the
keel of the sternum is confined to the posterior part; the crop is

372

AVES

large and muscular, taking the space usually filled with pectoral
muscles and the anterior part of the sternum. The young birds
when first hatched have a clawed thumb and index finger on the wing,

Nucleus of ^

Pander

l-otebra-^

Blastoderm

,. NecK of iQtebra

Inner- She/I

Outer- £helf
membrane

White yolk--'
yel/ow YolH

■-CholQZO

Dense a/bumen

'' l^e.ss dense a/bumen
^ Vitellines membr-ane

Fig. 208. Diagram of the hen's egg in longitudinal section. (After Lillie. Courtesy

of Henry Holt & Co.)

resembling the condition in Archeopteryx. They are able to climb
about the branches and find their own food, using their feet and wing
digits.

fhoryn^eof poucnes I to JOT

Anr. carc//na/ v.
Aortic Qr-dh JS"-,

Aortic ortzriei
TTandlZI

Trocnsa

/\trium -

Duct Of Cuvier •-

Stnus s/enosus '

i- iver -
Ventricle-

Dorsal aorta
Mesonephros '
F<ost. cardinal
Hind

Aortic arch I

(disopfieorln^)

carotid o .

Ext. iliac
CI

EKt. carotid a.

-Ant. card /not v.

Allantoic vein
Yolk stocK
Omph. mes. v.
Ornpti. mes. a.

Allonf-oic vein

A //onto is

Allantoic artery
Proc todoe am

Post-anal <jut

Fig. 209. Internal organs of a four-day chick. (From Lillie, Development of the Chick.

Courtesy of Henry Holt & Co.)

CHAPTER XIX

Mammalia

Perhaps our chief interest in the Mammals is derived from the
fact that we ourselves belong to this great class of vertebrates. In
the early days man found his most formidable enemies among the
mammals, and even now he suffers from the activities of the rodents.
On the other hand, mammals have furnished milk, meat, and furs,
and certain forms have been used for centuries as servants and
beasts of burden. Like the Birds, they are a tremendous economic
factor in our civilization.

Characteristics

Mammals have a double occipital condyle, a hairy skin, and well-
developed milk glands. They are warm blooded, with the heart
divided into four chambers and the single (left) aortic arch curving
over the left bronchus and continuing as a dorsal aorta, the visceral
arches modified into the earbones, with the cerebral hemispheres
usually connected by a heavy commissure called a corpus callosum.
The thoracic and abdominal cavities are separated by a muscular
diaphragm.

Order i. Monotremata. — This order includes egg-laying mam-
mals with mammary glands devoid of teats. Eggs about half an
inch long, rich in yolk with soft, but tough shells. Episternum and
coracoid well developed. Oviducts distinct throughout; cloaca in
both sexes, into which the ureters and urinary bladder open sepa-
rately. In the center of the vertebrae the epiphyses are absent or
imperfectly developed. The bones of the skull coalesce early.
The corpus callosum is absent. (Figure 210.)

The spiny ant eater {Echidna aculeata), found in Australia,
Tasmania and New Guinea, reaches a length of about 18 inches.
As the name would indicate, it is covered with spines and hairs.
It curls up like a hedgehog when alarmed. It has no teeth but is
provided with a long extensible tongue which it utilizes in securing
insects and worms. It places its egg in a primitive mammary pouch
consisting of a fold of the abdominal skin. The young when hatched

373

374

MAMMALIA

are fed by milk exuding upon the hairs of the mother's abdomen.
The young are later protected by being concealed in a burrow.
The long-snouted Echidna {Praechidna) is found in New Guinea;
here under the name of the " Nodiak " it is eaten by the natives.
The duck-bill {Ornithorynchus {paradoxus) anatinus) (Figure 2ii)
is found in Australia, New Guinea, and Tasmania. It has a small
rounded head, and a black horny bill. It crushes its food between

Fig. 2IO. Echidna. (Courtesy of N. Y. Zool. Soc.)

the ridged plates of its lower jaw and the roof of its mouth. Highly
developed glandular cheek pouches aid in digesting the food before
it reaches the small stomach.^ The body temperature of the duck-
mole, like that of Echidna, is but two to five degrees higher than the
surrounding medium. Its oviducts open separately into the cloaca,
but as in the birds the left ovary and oviduct alone are functional.
Aquatic, it digs burrows thirty feet into the banks of deep pools.
It builds a nest and deposits two eggs. When hatched, the young are
blind, hairless, with short beaks, but possessing teeth. The duck-
bill has no mammae and the milk oozes out through many fine

* Consult H. Burrel. 1927. The Platypus. Angus and Robertson Ltd., Sydney,
Australia.

MAMMALIA

375

apertures upon two mammary areas each about one half inch in
diameter. The young scrape and suck the milk from these areas.

Young duck-bills feed upon Crustacea, insects and worms. On
each hind foot, male duck-bills, or duck-moles, have a sharp horny
spur with a poison gland connected.

Fig. 211. Platypus. (Courtesy of N. Y. Zool. Soc.)

Fossil Relatives of the Monotremata. — Monotremata are found
in the Pleistocene, and it is possible that the doubtfully mammalian
types of Protodonta, Dromatherium and Micronodon^ of the Upper
Triassic, are also related.

Order 2. Marsupialia. — Viviparous, usually carrying their
young (born in a rudimentary condition) in a marsupium or pouch;
allantoic placenta usually absent. Small eggs undergo a total
segmentation in most species, and develop in the maternal uterus,
nourished by a secretion from its walls. The ventral surface
is supported by the marsupial bones, slender rods articulated right
and left, at the pubic symphysis. Corpus. callosum absent.

376 MAMMALIA

The opossum family {Didelphidae) ^ found in America, is dis-
tinguished by the presence of a marsupial pouch. This may be
absent or relatively shallow as in the case of some species or it may
approach the highly developed condition existent in the kangaroo.
The young of the Virginia Opossum {Didelphys virginiana) remain
for two months with their mother, at first residing in the pouch,
then ride around on her back. The opossum feeds on wild fruit,
berries, corn, insect larvae, eggs and young birds and mammals.

Tasmanian marsupials (Family Dasyuridae) have fewer incisor
teeth than the American opossum; they lack a cecum and their tail
is not prehensile.

The Murine opossum, a mouse-like form, is found in South
America. It is about the size of a chipmunk and lacks an abdominal
pouch.

The Australian ant-eater lacks a pouch and resembles a red
squirrel in appearance. The wombats are unwieldy creatures
resembling the badger. They have rudimentary cheek-pouches and
tail.

The Kangaroos {Macropodidae) are found in Australia where
nearly all land mammals are marsupials. Unlike the opossum and
the Tasmanian devily the kangaroo family are all herbivorous. The
newly born young are taken by the mother and placed in her pouch
where they remain until their eyes open and they have developed
hair. For some time after this they return to the pouch from little
excursions into the world. When first born, a kangaroo may be
not more than an inch long.

The " Old man " or gray kangaroo reaches a height of over five
feet, weighs two hundred pounds and can leap over twenty feet,
using its long legs and powerful tail. The red kangaroo with a brick
red coat of a very fine, silky texture is the one most frequently seen
in captivity. It reaches a height of almost four feet. The rock
wallabies (genus Petrogale) do not utilize their tails a great deal in
locomotion but use them as balancers. The black-tailed wallaby
and the opossum are said to have starved out the other animals on
Kawau Island.

Fossil Relatives of the Marsupialia. — For the most part the
marsupials are found as fossils from the Upper Triassic to the
present.

Order 3. Insectivora. — Small, usually terrestrial (but some-
times aquatic or arboreal) clawed mammals; feet plantigrade.

MAMMALIA 377

generally pentadactyle; molars enamelled, tuberculated, and rooted.
They have a primitive brain. There are frequently scales on the
tail among the hairs; the clavicle is present; the animals have soft
hair, and usually a proboscis-like, tactile snout.

Feeding almost wholly on insects and worms they are chiefly
nocturnal. They are found almost everywhere except in Australia
and South America. Evidence from fossils indicates that they are
survivors of extremely primitive placental mammals. The eyes are
extremely small and in some cases hidden by fur.

The colugo {kaguan) is a peculiar form, sometimes called the
" flying lemur." It is found in trees from Siam to Java with a
smaller relative inhabiting the Philippines. It belongs to a sub-
order, Dermoptera. Extensions of its furry skin stretched between
the fore and hind legs enable it to plane through the air like a flying
squirrel. It is about the size of a small cat.

The shrews {Soricidae) are small, mouse-like animals with
pointed heads, external ears and eyes, rat-like feet, slender bodies
and a short tail. The common shrew is found on the Atlantic
coast, ranging from New England, Southward to North Carolina
and Northwestward to Alaska. It is quick of hearing, utterly
untameable, and from glands in the axillary region, emits a musky
odor, which repels hawks, cats and foxes, but apparently attracts
weasels and owls. The water shrew is the largest of the American
forms, measuring 6 inches in length, with a tail over 2 inches long.
The great musk shrew of India, called the " muskrat " in the Old
World, is important as a destroyer of insect vermin. Some of the
long-nosed shrews are aquatic, living in bank burrows and swimming
and diving with ease. (Figure 212.)

The short-tailed or " little " shrew {Cryptotis parvd) has a total
length of but 3.1 inches and is the smallest American mammal. It
is found from the middle West to the Atlantic coast. ^ Shrews eat
worms, insects, young birds, but also feed on roots and nuts. Euro-
pean superstitions regarding the shrews include such statements
as that of Rev. Edward Topsell, who in his rare " Historic of Four-
footed Beastes," printed in London in 1607, says of the shrew that
" It is a ravening beaste, feigning itself gentle and tame, but, being
touched, it biteth deeply and poysoneth deadly. It beareth a cruel
minde, desiring to hurt anything, neither is there any creature that

2 H. E. Anthony. 1928. Field Book of North American Mammals. G. P.
Putnam's Sons, N. Y.

378

MAMMALIA

it loveth, or it loveth him, because it is feared of all." (Ingersoll,

1906 p. 71.)

Physicians report the characteristics of the shrew as occurring
in certain women and men as well. Perhaps dementia praecox and
paranoiac tendencies may be fostered by a policy of letting children
have their own sweet will, and only defending oneself from their
actual blows.

Fig. 212. Smoky shrew. (Courtesy of W. Va. Exp. Sta.)

The moles ( Talpidae) have vestigial eyes, broad, spade-like front
teeth and no neck. Unlike the shrew, the animals have no external
ears or external eyes. There are twelve species. On the body the
mole has fine, thick velvety fur, but the tail is hairless.

The common mole is gray in color, with webbed hind feet, and
reaches a length of about six inches. It burrows in loose earth and
in ten seconds will leave upheaved tunnels. Hornaday timed a
mole in a clover field and found that it had tunnelled twenty-three
feet in seven hours.

The star-nosed mole has, on the tip of its nose, eighteen ray-like
points, with four smaller ones between them. It burrows into
swamps along the banks of ponds and brooks and apparently is
adapted to an aquatic life. It devours fish, fish eggs and water
snakes and also feeds on insects and worms.

The common European hedgehog has an armor of short, stiff,
sharp gray spines which are not barbed as in the porcupine and which

MAMMALIA 379

are not discharged. When irritated, the hedgehog rolls itself into
a ball with its head tucked between its feet. Hedgehogs feed on
slugs and insects, but also eat small mammals and frogs, and are
protected on account of their value as snake killers. Some Euro-
peans are very fond of the flesh of the hedgehog.

Fossil Relatives of the Insectivora. — The living families of
moles, shrews and hedgehogs arose in the Eocene period. Related
forms occurred in the Jurassic. R. C. Andrews has discovered in
Mongolia fossil skulls with teeth of the insectivorous ty^pe, indicating
the pattern from which insectivores, carnivores, and possibly pri-
mates may have evolved.

Order IV. Chiroptera. — Clawed animals with fore-limbs modi-
fied for flight, the bones, especially those of the second to the fifth
digits, being greatly elongated so as to support a broad web of skin
extending back to the hind-limbs. The sternum has a keel for the
attachment of the pectoral muscles, which are important to the
movements of flight. The dentition is complete. The cerebral
hemispheres are smooth and do not overlap the cerebellum. Anal
glands, furnishing a strong, even offensive smelling secretion, are
common. Although bats are swift fliers they do not have air spaces
in their bones as do some of the birds. There are more than six
hundred species of bats, which at first were classed with birds.

The Megachiroptera are large, diurnal forms, sometimes called
fruit bats, fox bats, or "" flying foxes." They destroy fruits and on
this account have been barred from admission into some states.
The larger fruit bats are eaten by the natives of the East Indies.
The hammerheaded bat is found in Africa.

The Microchiroptera include the leaf -nosed bats, the vampire bats
and the smaller common forms. The leaf-nosed bat is found in
California and Mexico and has a wedge-shaped leaf of naked skin
just behind the nostrils. The javelin bat, ranging from South Amer-
ica to Mexico, is a vampire or blood-sucker, attacking horses, cattle
and men. It reaches a length of four inches. An extremely large
form from South America, erroneously called the " great vampire,"
is not at all injurious, but feeds on fruits and nuts. It is twenty-
eight inches in length.

The naked bats of Borneo have thick leathery skins and a scent
gland on their neck. Under each arm they have a mammary pouch
in which the young are carried and nursed until they are able to fly.

The cominon bats ( Vespertilionidae) are found all over the world.

38o MAMMALIA

Of the two hundred species, there are less than twenty in the United

States.

The commonest American species are the little brown bat {Myotis
lucifngus) which is less than four inches in length, and the brown bat
{Eptesicusfuscus) which is widely distributed throughout the United
States. The little red bat is a swift flyer and as active as a bird.
The gray bat is a large form reaching a length of three inches. It is
found in the United States and Canada. The big-eared bat has ears
half as long as its body and is found in the Southern States,

One family {Molossidae) seems more like the rat, for it is ter-
restrial.

Fossil Relatives of the Chiroptera. — Bats are known from the
Eocene of Colorado.

Order V. Carnivora. — Clawed, furry mammals with at least
four digits. Incisors small; canines large, curved and pointed;
premolars and molars usually compressed; stomach simple, cecum
small. Tapetum lucidum of eye very shiny. Clavicle lost or
reduced, ulna and radius well developed. Teats abdominal, uterus
bi-cornuate, placenta deciduate, usually zonary.

Sub-Order Fissipedia. — The cat family (Felidae) includes lions,
tigers, leopards, and the like.

The " saber-tooth " cats were found in America and the Old
World in the Tertiary period. The great " saber-tooth " tiger
{Smilodon) was as large as our largest Kadiak bear.

The puma, cougar or " mountain lion," an American form, once
ranged over the whole continent. It may reach a length of seven
feet and a weight of two hundred pounds. While it is stated that the
puma dreads mankind there are well-authenticated reports of at-
tacks on children and grown men.

The jaguar is the largest and handsomest species of the cat
family in America. It is found as far North as Southern Texas.
It is an enemy of pigs, cattle, horses and wild mammals, but ap-
parently afraid of man. It may reach a body length of five feet
with a tail two feet long and weigh one hundred fifty pounds. (Figure

2I3-)

The ocelot or tiger cat, also found in Texas, is a small leopard,
with horizontal black stripes on a yellowish ground color. It is
about the size of a small spaniel and feeds on birds and arboreal
mammals.

The Canada lynx is a small bob-tailed wild cat found in Quebec

MAMMALIA

381

and Ontario, but ranging southward into the United States. The
Bay lynx, wild cat or bob-cat, is found east of the Mississippi in
wooded areas, and extends westward to the Pacific coast states. It is
a formidable enemy of cotton tail rabbits.

Fig. 213. Jaguar. (Courtesy of N. Y. Zool. Soc.)

The lion has been considered the king of beasts for centuries.^
Amenenhat I. recorded proudly, 2000 B.C., " I hunted the lion."
The lion, explorers state, is by no means the bold animal that it is
traditionally supposed to be. The African buffalo is said to be more
than a match for a single lion. The zebra seems to be the lion's
favorite food. (Figure 215.)

The tigo- is found in Persia, Siberia and Manchuria and ranges
southward through China and the Siamese and Malay Peninsula to
Java, but is not found in Borneo. Passing around the Bay of Ben-
gal, it has never crossed to Ceylon. It is considered a far more
dangerous animal than the lion. In 1927, the Indian Government
reported 1,033 persons killed by tigers.

The leopard is a more active, sly animal than either the lion or
the tiger, and is probably responsible for many more losses among
sheep, cattle and ponies. Leopards killed 218 persons in India in
1927.

1 The Marcomanni called the lions sent across the Danube by the Romans "dogs."
Herodotus II. 69.

382

MAMMALIA

The cheeta or hunting leopard of Africa and India belongs to the
genus {Cynaelurus) intermediate between the cat and the dog. It
has been trained to capture game for its master in India.

The cojnmon house cat has descended from the single wild species
{Felis maniciilatd) of Northeastern Africa. Egyptians prepared

Fig. 214. Canada lynx. (Photo by courtesy of Canadian National Railways.)

mummies of cats which indicates that they regarded them as beloved
companions. A tablet in the Berlin Museum dating from 1800
B.C. is inscribed with the word, " mau," meaning cat.

The Egyptian wild cat of today {Felis libyca) is about the size
of the domestic cat, generally yellowish in color with faint pale
stripes which become darker on the limbs. There are today about

MAMMALIA

3^3

thirty races of cats, grouped into long-haired and short-haired
varieties. There is also a Mexican hairless cat. (See p. 524.)

The civets ( Viveridae) are relatively small animals with incom-
pletely retractile claws. From their scent glands, " civet " perfume
is secured.

Fig. 215. Tsavo lions. Both specimens are males, but from an arid region of
Africa where manes are lacking. They killed 135 men employed in the construction of
the Uganda R. R. (Courtesy of Field Museum of Nat. Hist.)

The mongoose ^ (mungoos) is found in Egypt where it is called the
ichneumon and in East India where it goes by the native name,
mungoos. It lives in thickets and in holes among rocks. It is an
enemy of snakes, lizards, poultry and rodents and is said to oc-
casionally chew the ears of native infants, left sleeping.

There are three species o( hyenas {Hyenidae). They are found
in Europe, Asia and Africa, where they are much despised. They
are scavengers. They have a large dog-like head and strong jaws
with thirty-four powerful conical teeth. Hyenas are able to kill
donkeys, sheep and camels.

The raccoons {Procyonidae) are plantigrade like the bear family.
They are found in the wooded regions of the Southern and Eastern
states, especially in swamps. They live in hollow trees and are

3 In 1872 the mongoose was introduced into Jamaica to destroy the rats infesting
the sugar cane. At first beneficial there, it began killing poultry until it proved a
distinctly injurious form. Recently it has turned cannibal and relieved the situation.

3^4

MAMMALIA

omnivorous. They have the peculiar habit of washing (soaking)
food before eating it.

The bears ( Ursidae) are plantigrade (flat-footed) animals with
long claws that are not retractile. They are terrestrial and omniv-
orous. Very few of them are able to climb trees. The polar bear
has a pure white coat the year around. In the winter, it lives on
fish, seals, walruses and the carcasses of whales, augmenting its
diet in the summer by vegetable matter. It reaches a height of
fifty inches and a length of over seven feet and may weigh over one
thousand pounds. In captivity if polar bears are furnished with a
large swimming pool, they can endure hot weather as well as the
black bear (Hornaday).

The brown Kodiak bear of the Kodiak Island ranges from Sitka
to the extremity of the Alaskan peninsula. It reaches a length of
about ten feet, and weighs nearly two thousand pounds. It is,
however, a timid animal. It feeds on salmon and small mammals,
but in the summer almost becomes a vegetarian.*

The grizzly bears have high shoulders, brown hair with silvery
gray tips and may reach a weight of about twelve hundred pounds.
In Yellowstone Park, they have become celebrated for their excessive
friendliness to visitors who at times are disappointed to discover
that the animals are not as tame and harmless as dogs. (Figure
2i6.)

The black bear is a timid animal and an excellent climber. It is
still to be found in the Adirondacks and the mountains of Pennsyl-
vania and West Virginia. It feeds on berries and fish and robs
"bee-trees." The black bear has a brown phase, brown (cinnamon)
and black cubs sometimes being found in the same litter.

The glacier bear., found in Alaska, the smallest species of bear in
America, reaches a height of but two feet. Its color is bluish gray
except for the dark brown muzzle.

The Mustelidae are small, fur-bearing animals such as the otter,
mink, weasel, marten, wolverine, skunk and badger. The North
American otter is still found in the South and also in Northwest
Canada and Alaska. It lives in a burrow usually under the roots
of a large tree growing near the water. It reaches a length of about

* In the spring when he emerges from hibernation the Kamschatkan brown bear
eats sea-weed, later he grazes on herbage, and in the middle of June feeds on the migrat-
ing salmon. In August, he eats wild peas, in September he eats berries and in later
October, just before hibernating, he feeds luxuriously on ground-marmots. (Elton.)

MAMMALIA

3^S

two feet. The sea otter is one of the most valuable of the fur-bearing
animals. It is now raj-ely found except in Alaska. Its fur is a
lustrous black and very thick and fine in texture. The 7nink, much
smaller than the otter, lives along the banks of streams, but is not

Fig. 2 1 6. Bear and cub, in Yellowstone National Park. (Photo by V. J. Mele.)

an aquatic animal like the otter. The pine marten or " American
sable " lives in dense forests of pine and spruce, and feeds on small
rodents, birds and reptiles. It grows to the size of an ordinary
house cat. Demand for their fur has reduced the number until but
few of these shy animals remain. Pennant's 77jarten, called the
black cat, is rather large, sometimes reaching a length of three feet
and a weight of eighteen pounds.

The weasel, the smallest of the marten family, is brown in sum-
mer, but becomes the white " ermine " in winter. It kills chickens
and small mammals, being particularly valuable in the extermination
of rats and field mice. ^\\z ferret is a domesticated variety of the
English " pole-cat." Formerly used in this country in hunting
rabbits and rats, it is rarely seen today. (Figure 217, A and B.)

The wolverine, " mountain-devil " or Carcajou, is the greatest
thief among animals. It follows a " line " of traps, devouring the
bait and sometimes stealing the trap. Cabins and caches are
stripped of edibles and foodstuffs, too large to carry away, are

386

MAMMALIA

dragged in the dirt. Wolverines resemble a cross between the
badger and the bear.

The common skunk. Mephitis mephitica, is a native of North
America, found from Hudson's Bay to Guatemala. An allied form,

V^

^.d.^

Fig. 217. /^, ferrets. 5, wolverine. (From L. A. Fuertes. Courtesy of Sllngerland-

Comstock Publishing Co.)

the conepatl, is found in South America. Preeminently an insect
eater, the skunk destroys more beetles, grasshoppers, and grubs
than all of the other mammals together, and also devours vast
quantities of mice in addition. The skunk is also partial to sala-

MAMMALIA 387

manders, snakes and the eggs of birds nesting on or near the ground.
Under conditions of civilization his fearlessness ^ renders him an
important enemy of poultry. It is said that owls, eagles, and the
puma prey upon skunks.

The badger skunks resemble badgers in that they are expert
diggers. They are found in South America but range northward
into Arizona. The badger lives in burrows and feeds on ground
squirrels and prairie dogs. It has naked soles, short legs and a
broad, flat body. In the United States, it is found in the Rocky
mountains and westward to the Pacific coast. (Wisconsin is called

Fig. 218. Young red foxes. (Courtesy of A. B. Brooks.)

the " badger " State.) In Alaska it hibernates during most of the
winter. The European badger lives in the woods. The Asiatic
badgers have a strong musky secretion.

The Dog family {Canidae) have served as man's companion
^onger than any other domesticated animal. They are found every-
where except in New Zealand. The genus Canis includes dogs,
wolves, foxes, and jackals. (Figure 218.)

The common red fox is found throughout the whole northeastern
United States extending westward to the limit of trees. Foxes

* Few there are who will brave the overpowering scent from the anal glands of a
skunk, which can be discharged in any direction to a distance of ten feet. The scent
is so powerful that it can be readily detected when a mile away, and it is capable of
anesthetizing a person. The scent is n-butyl mercaptan, C4H9SH, the excretion of
sulphur being quite characteristic of the scent glands as well as the urine of the meat
eaters.

388 MAMMALIA

feed on small mammals and upon ground birds as well as on frogs,
lizards, insects and fruits. Foxes are extremely cunning and are
valued by hunters on that account. A rare phase of the red fox,
the black fox, sometimes called the " silver gray " fox, is extremely
valuable for its fur. A single black fox skin is said to have brought
$2,900.00. Fox farms are found in Canada and in the northern
part of the United States. At the winter fur auction in New York
City beginning January 23, 1928, it was reported that the silver fox
pelts (over 800 in number) were worth more than $1,300,000.
The majority of these skins came from a single fox farm ^ in Wis-
consin.

The Arctic fox has two color phases, one, brown in summer and
white in winter; the other, gray or black in summer and blue or
black in winter. In the far north it is snow white the year round.
In Iceland and the Aleutian Archipelago it is dark the year round
and is known as the " blue " fox. In Labrador the blue phase is
rare, while in Greenland, Alaska and Spitzbergen both are common.

The darker color makes the fox extremely conspicuous instead
of protecting it. Roosevelt and Dugmore have both concluded
that practically speaking there is no such thing as protective or
concealing coloration. (See Thayer's theory, page 488.)

The coyote or prairie wolf is a cowardly animal, stealing poultry,
pigs, lambs and sheep, but never attacking mammals larger than
deer. Their cry is a dog-like barking howl. They are smaller
than the gray wolf, but somewhat resemble it.

The red wolves have been so active of late in Texas, killing sheep,
goats and poultry, that in the rural districts government hunters
have been employed to kill them off. In the eight months preceding
January, 1928, 100 of the animals were killed. Bounties as high as
I300.00 were offered in some Texas counties. The red wolf, like
the coyote (prairie wolf), is a solitary nocturnal despoiler. A giant
red wolf caught recently weighed Gi^ pounds.

The gray wolf, " lobo " or timber wolf, is a large strong animal
ranging from Florida to Arctic America. They hunt in packs or in
relays and destroy deer, antelope, cattle and young horses. In
Alaska they grow to a length of over 4 feet and a height of 2^ feet,
weighing over 100 pounds.

^ Fromm Bros., of Hamburg, Wis., received a single check for ^1,021,071.24 in
payment for the silver foxes sold in New York at the auction of 1928. At other auctions
that winter, they received $267,203.00 additional.

MAMMALIA 389

The African and Oriental jackals are scavengers, but also rob
hen-roosts. They feed on figs and fruits as well.

There are over 200 breeds of domestic dogs. They are derived
from at least seven wild species, including the jackals of Asia, the
jackal-wolf of Northeast Africa, the gray wolf and the coyote of North
America.

Sub-Order Pinnipedia. {Seals and Walruses.) — The Pinnipedia
are aquatic carnivores with their digits united by a membrane.
The Northern fur seal iOtaria ursina) is not a true seal, but is a sea
bear or sea lion, found on the Pribilof Islands. It spends about
two-thirds of each year far out at sea, making a circuit of six thou-
sand miles in the open ocean without touching land. The United
States protects a large fur seal herd on the Pribilof Islands, Alaska.
The California sea lion {Otariidae) feeds mostly on squids and octopi,
but fishermen consider it injurious as a fish consumer. The true
seals {Phocidae) have no external ears and their nostrils are dorsally
situated. Among the common forms are the harbor seal and the
hair seal. The bluish gray fur of the harp seal is extremely valuable.
The hooded seal males have a nasal sac that can be inflated to a
length of ten inches. Elephant seals (twenty feet long) are nearly
extinct, but a few were discovered recently at Guadaloupe Island.
Walruses {Odobenidae) are clumsy on land, but have extremely
powerful tusks (canine teeth) and can wreck small boats. They
eat shellfish, crustaceans and aquatic plants. Formerly supplying
the Alaskan natives with fuel, light, harness and boats, the demand
for walrus oil has led to their almost complete extermination.

Fossil Relatives of the Carnivora. — Primitive Creodonta are
found in the Eocene of North America, Europe, and Africa, and are
almost indistinguishable from the Insectivora and Ungulata of that
period. Fossil dogs appeared in the Eocene of North America.
Fossil cats are known from the Oligocene period where the huge
saber-tooth tigers lived from the Miocene to the Pleistocene. Bears
came in with the Miocene, and the great cave-bear ( Ursus speleus)
of Europe was hunted for food during the Pleistocene period. Seals
and walruses have descended from primitive Pinnipedia of the
Miocene period.

Order VI. Rodentia. — Vegetable-feeding, mostly of small
size, with furry integument, clawed digits, and usually plantigrade
limbs. Clavicle usually present. No canines, never more than two
incisors in lower jaw and but two in the upper except in the Lepo-

390 MAMMALIA

ridae, all elongated, chisel-like, growing from persistent pulps;
premolars few. Placenta deciduate and disc-shaped. Cecum
large. (Figure 219.)

Rodents vary in size from the porcupine of three feet in length
to the small mouse about three inches long. Squirrels {Sciuridae)
are found everywhere except in Australia and Madagascar. Four
species are found in the United States and Canada.

The Calijornia ground squirrel {Citellus beecheyi) (see Figure
220) lives in and on the ground, storing its food of fruits, nuts, and
grain in the ear in its underground burrows. It is of particular
interest since it carries bubonic plague caught from rats.

Other squirrels include the Eastern Gray squirrel which lives in
the tree tops and the 7'ock squirrels or " chipmunks " which live in
fences and among the roots of large trees. The largest squirrel in
the world is the great Malabar squirrel of India, which grows to be
eighteen inches long, with a tail fourteen and one-half inches long.

The Easter?i chipjnunk (Tamias st?-iatus) ranges from Illinois
eastward. It is a lively little creature about ten inches long, and
seems fond of nests in rocky crevices and decayed tree trunks. It
usually has several entrances to its tunnel. It feeds on acorns,
nuts, and grains but is also a consumer of mice, birds' eggs and
insects. Its chief enemy is the weasel but it is also preyed upon by
birds.

The flying squirrels {Sciuropterus) are not able to fly, but by
means of a furry membrane spread from the anterior to the posterior
limbs they plane from one tree or branch to another. The Asiatic
flying squirrel reaches a length of eighteen inches.

The p}'airie-dogs (Cynomys) live in villages on the plains. They
are a great pest in the cattle country. Rattlesnakes visit their
burrows in search of young " dogs " and burrowing owls are fre-
quently found in vacated burrows, but the " happy family " does
not exist.

The woodchuck, or "groundhog," lives on clover and other grasses
and may enter isolated gardens. He lives in a burrow and hiber-
nates in November. It is traditional that he wakens on " ground-
hog day," February 2, and " if he sees his shadow, sleeps six weeks
longer, which means a cold spring,"

The gray marmot is found in the Northwestern part of North
America and is called the " whistler " on account of its danger signal.

MAMMALIA

39^

Fig. 219. Red squirrel. (Courtesy of Canadian National Railways.)

Fig. 220. California ground squirrel {Citellus beecheyi). (Courtesy of Joseph Dixon,

University of California.)

392

MAMMALIA

The Alpine marmot is. a similar form, hibernating a dozen in a group,
packed into a hair-lined burrow.

The North American beaver {Family Castoridae), an aquatic
rodent, has a heavy body, webbed hind feet, and a large flat tail.
Contrary to the statements of some nature fakers, the tail is not

ii^'^

Fig. 221. y^, chipmunk. 5, flying squirrel. C, prairie dog. D, beaver.
L. A. Fuertes. Courtesy of Slingerland-Comstock Publishing Co.)

(From

used as a trowel or a sledge, but as a danger signal and in swimming
and diving. The beavers fell trees up to eighteen inches in diameter
and quickly dam streams to flood the entrance to their burrows.

The largest family of rodents and the most important economi-
cally is the family Muridae to which belong the rats and the mice.

MAMMALIA

393

The genus Rattus includes a number of species, all of which are
important as disease carriers. (Figure 222.)

The brown rats (R. norvegicus) destroy grains, poultry and nesting
birds, carry away eggs, sometimes cause fires, and even bite through
lead pipes and cause floods. The black rat of England was the
carrier of the " great plague "
of 1665 which destroyed one
hundred thousand people.
Brown rats eventually drove
the black rat out of England.
It is now chiefly confined to
ships. It disseminates bu-
bonic plague, which is trans-
mitted by rat -fleas to ground
squirrels. Ships in port have
three-foot metal discs guard-
ing their hawsers. Poison
baits and fumigants are used
to destroy rats in ships and
storehouses that are not rat-
proofed.

The Eastern wood rat
(pack rat, trade rat), the
most handsome of the rats, is
noted for its mental capacity.
It stores food, but also steals
tools, silverware and even
watches, and stores them
away. Vernon Bailey states
that they are edible, " better
than Gray Squirrels."

The albino rat is our most
important mammal for ex-
perimental purposes, and has
been inbred for nutrition and
other studies (see p. 441).

The common house mouse
{Mus musculus), a species introduced from Europe, is an important
enemy of food stuffs and especially injurious in warehouses. The
field mouse or meadow mouse (see Figure 223) is a short-eared,

Fig. 222. Brown rat infested by Cysti-
cercus fasciolaris. (A. T. Hopwood, Para-
sitology, vol. 14, no. I.)

394

MAMMALIA

short-tailed animal with a thick body. It feeds on roots and
grasses and also turns its attention to young fruit trees, shocks of
corn, and fields of alfalfa. The pine mouse is a burrowing mam-
mal feeding largely underground. It is of great injury in truck

gardens and has damaged many
small trees.

Lemmings, short-tailed prai-
rie-dog-like forms, have a max-
imal production which was in
times past every four years, but
now comes about every ten
years. Their migrations (see p.
418) are a sign of over-produc-

TI" T. ~, 'Z. ' tion. It is interesting to note

223. Meadow mouse. (Courtesy °

of W. Va. Exp. Station.) that in their enemies, hares,

Arctic foxes, weasels and lynxes,
there is a corresponding cycle of increase.

The musk-rat or musquash is a small aquatic rat-like rodent
with a broad blunt head, thick-set body and short legs. Its long
tail is almost naked. Musk-rats are widely distributed through the
United States. They are omnivorous, feeding on the stalks and
roots of flags and reeds, and on animals such as insects, fish and shell
fish. Musk-rat skins are dyed and sold as " Hudson Seal " or
" electric Seal." The dormouse, a small form found in the Old
World, resembles a small squirrel. It spends about six months of
the year " wrapped in a profound sleep." It utters a shrill whistling
snore surprising in its volume. The American porcupines are
arboreal forms. They are well protected by spines which readily
pull out and being barbed remain in the flesh of the enemy. Jerboas
or jumping-mice {Dipodidae) (Figure 224 A) have kangaroo-like
tails and hind legs and are reputed to jump ten feet,

TYiQ pouched gophers {Geomyidae) (Figure 224 B) are burrowing
rodents found in Central America and the central plains of North
America. The red pocket gopher is a vicious, thieving animal,
tremendously injurious to fruit trees, grain and vegetables. It also
honeycombs and weakens the banks of canals and irrigating ditches
m the Mississippi valley. Farmers use traps and strychnin poisoned
grain in an attempt to kill ofi^ the pests.

The hare and rabbit family {Leporidae) includes two quite distinct
groups. The rabbit group {Sylivilagus) is represented in the United

MAMMALIA

39S

States by the gray 7'abbit or " cottontail " which is found from New
England to Yucatan. Although cottontails are small with relatively

Fig. 224//. Egyptian jerboa. (Courtesy of N. Y. Zool. Soc.)

Fig. 2245. Pocket gopher {Thomomys a'xahnee). (Courtesy of T. I. Storer, Univ. oi

Cilif.)

short, weak limbs, they are exceedingly cunning and burrow in cities
and towns, rearing families in apparently quite accessible places. In
the West, cottontail rabbits are such pests that rabbit-proof fences.

396 MAMMALIA

poison baits, trapping and hunting are all resorted to, in an attempt
to decimate them.

The hare family {Lepus) includes the Jack hare (sometimes called
the Jack rabbit), the prairie hare, the vaj-ying hare and the polar hare.
The " Jack hare " can distance a speedy greyhound and some hunters
insist that it can beat a rifle bullet! The hare is a large, long-legged,
long-eared animal which does not burrow, but rears its young in a
nest.

Hares and rabbits girdle trees and eat garden vegetables, clover
and alfalfa. It is said that except when famished hares exhibit
considerable delicacy of taste, selecting only certain varieties of
soy-beans and alfalfa. Rabbits, introduced into Australia and New
Zealand, spread rapidly and destroyed the grass so that sheep died
of starvation.

Tularemia, a disease somewhat similar to spotted fever,^ is car-
ried by lice and ticks from one rabbit to another. It may cause
serious epidemics and reduce the number of rabbits and ground
squirrels considerably. Man is susceptible to tularemia. It is
transmitted from the bites of ticks or lice, or from handling diseased
rodents.

Fossil Relatives of the Rodentia. — Rabbits and squirrels were
first found in the Oligocene of North America, while the beaver, rats,
and mice appeared in the Pliocene of Europe.

Order VII. Edentata. — Clawed, without enamel on the teeth;
teeth absent from the anterior part of the jaw. Great number of
sacral vertebrae, as many as thirteen in some armadillos. Brain
sometimes low, sometimes of comparatively high organization.

There are three genera of South American ant-eaters {Myrineco-
phagidae), all lacking teeth, but with extremely long protrusible
tongue, plentifully coated with a thick secretion developed from their
salivary glands. They have long snouts and powerful bodies
adapted to tearing bark from trees or ripping open ant hills. (Figure
225.)

The great ant-eater may reach a body length of five feet with a
tail as much as two feet long. It is able to defend itself against dogs
and snakes. The single oflfspring rides on the back of the mother,
remaining with her a year. The tamandua, a small ant-eater found

^ R. R. Parker and J. S. Dade, Tularaemia in Sheep in Nature, Pub. H. Reports,
vol. 44, Jan. 18, 19-9, found Bacterium tularense in the flesh of sheep. Probably the
wood tick, Dermacentor andersoni, transmits the disease from jack rabbits to sheep.

MAMMALIA

397

as very

in South America, reaches a length of about two feet. It h
large front claws.

The sloths {Bradypodidae), found only in the New World, are
arboreal forms, never descending to the ground if possible. They
are nocturnal feeders and their hair usually contains quantities of
green algae, causing them to resemble branches. The three-toed
sloth has nine cervical vertebrae, while the two-toed sloth has six
instead of the seven usually found in mammals.

/i

>-»^: ' • '■■■ ;■.'*-

^

Fig. 225. Giant ant eater. (Courtesy of N. Y. Zool. Sec.)

The three-banded armadillo {Dasypodidae) of Argentina is able
to close itself into a tight round ball so that it resembles a nut.
The nine-banded armadillo is somewhat larger and is found ranging
from Texas to the central part of South America. It has been
studied recently at the University of Texas, since it offers a most
interesting example of quadruplets, identical of course. Armadillos
eat insects and worms, and occasionally salamanders and lizards.

Fossil Relatives of the Edentata. — Fossil remains of the modern
sloths and ant-eaters are unknown, but the extinct ground sloths
{Megatheriidae) with the head and teeth of a sloth and the tail of an
ant-eater were found in the Pleistocene, one species having reached
the length of nearly twenty feet. A large armadillo-like form known
as Glyptodon was found in the Pliocene of the Americas.

Order VIII. Ungulata. — Terrestrial, usually herbivorous, nearly

398

MAMMALIA

always hoofed. Clavicle absent, canines small or absent, premolars
and molars well developed with broad crowns.

Sub-Order Hyracoidea. — The hyrax ( Hyracoidea), a small animal
found in Africa, is probably the form described in the Bible as
" Cony." It has about twenty-two vertebrae that bear ribs. It has
in addition to a cecum a ^poAVob-ectal cecae. Superficially it resembles
the rabbit, having a hare lip and an extremely short tail. Its front
feet have four toes, while the hind feet have three. (Figure 226.)

Fig. 226. Hyrax. (Courtesy of N. Y. Zool. Soc.)

Sub-Order Proboscidea. — The elephants have no clavicle. They
have an extremely thick skin, huge five-toed legs and a long nasal
proboscis. The incisors of the upper jaw grow to form tusks.
Elephas indicus has been used as a beast of burden in India for many
years.'^^ It reaches a height of less than ten feet. It is more intelli-
gent and docile as well as more powerful than the African species.
Elephas ajricanus has a shorter, more rounded head than the Asiatic
and its ears are enormous, covering the back of the head and the
neck. Both the male and the female have tusks (elongated incisor

^»Livy in describing Hannibal's passage over the Alps (Livy, Book 21. Chapter
28) discusses the manner in which historians supposed that his war-elephants were
transferred across the Rhone River. Some reported that the elephants were induced to
swim, while others described the manner in which they were ferried on long rafts.

MAMMALIA

399

Indian

African

Fig. 227. A, Indian rhinoceros. B, South American tapir. C, elephants. (From
L. A. Fuertes. Courtesy of Sllngerland-Comstock Publishing Co.)

400 MAMMALIA

teeth) while the African form has three toes on its hind feet instead
of four. It reaches a height of twelve feet. (Figure 227.)

Sub-Order Perissodactyla. — Perissodactyla are o^^-/o^(^Ungulata
with an uneven number of digits; the axis of symmetry passes
through digit three. Premolars and molars are completely folded.
Stomach simple; cecum large. Gall bladder absent, teats situated
in the groin and placenta diffuse. (Horse, tapir and rhinoceros.)

The tapijs {Tapiridae), found in tropical America and India, are
as old a family as the horses {Equidae). They have four-toed fore
feet and three-toed hind feet. The nose and upper lip are elongated
into a proboscis. Tapirs are enemies of the cocoa plant. They are
hunted for food and for their hides.

The rhinoceroses have extremely thick skin deposited in folds
resembling plates of armor. The East Indian species has one nose
horn, and the African white rhinoceros has two. Nose horns, out-
growths of skin like whalebone, grow at the base as the tip wears
away. They are used as weapons, and powdered for medicines.
The rhinoceros injures cane and melon fields, and cacao plantations.

The horse {Equidae) has a geological record back to the Eocene
Epoch when the little Eohippus had four complete toes and the
splint of a fifth on its fore feet, while the hind feet had three com-
plete toes and a splint of the fifth. It was about the size of a small
dog. (See p. 526, The Evolution of the Horse.)

All our horses have been introduced from the Old World. Wild
horses are found at the present time in Asia {Equus heinmonus, the
Asiatic Wild Ass; and Equus przewals kit, Przewalsky's Horse) and in
Africa (£. asinus, the African Wild Ass; and the Zebras, Equus
zebra, burchelli, and Quagga).

The African Wild Ass has been domesticated and is utilized as
our donkey. The White Ass was used in Africa as a means of
transportation for the great, centuries ago. Andrews states that the
Asiatic Wild Ass is capable of bursts of speed of 60 miles an hour.

Hybrids. — The " mule," a hybrid between the horse and the ass,

is an extremely powerful draft animal. Male hybrids are as a rule

infertile,^ and only a few cases of fertile hinnies ^ have been reported.

8 Wodsedalek, J. E. 1916. Causes of sterility in the mule. Biol. Bull., vol. 30,

PP- 1-39. 1916.

8 Groth, of the Texas A. and M. College, has reported a case of "Old Beck," a
fertile mule, who in 1920 produced a daughter, sired by a Jack, and later produced a son
sired by a stallion. It is further reported that the horse-like colt has sired a healthy
colt, making "Old Beck" a grandmother.

MAMMALIA 401

The United States Department of Agriculture has experimented
with the zebra and the quagga, hybridized with the horse, but has
been unable to secure any notable improvement over the mule.
The African quagga is now extinct.

Artiodactyla. — Artiodactyla are even-toed ungulates in which the
third and fourth digits form a symmetrical pair. Premolars are
smaller than molars; stomach usually complex, cecum small.
Placenta diffuse or cotyledonary.

The Artiodactyla are divided into the Ruminants and the Non-
Ruminants. The Ruminants are that extremely important group
of domestic animals which have been of service to man for thousands
of years — cattle, sheep, goats, and camels; also such non-domesti-
cated types as antelopes, deer and giraffes. The Non-Ruminants
include pigs, peccaries and the hippopotamus.

The African hippopotamus or " river horse " once ranged over
Europe and India. It is thick skinned and almost devoid of hair.
Its perspiration is reddish. The hogs {Suidae) are important sources
of food supply. The United States produces over one-third of the
hogs of the world, and exports many. The wild boar has been hunted
for centuries by the sportsmen of Europe. Its tusks are elongated
canine teeth. The African wart hog has such a horrible appearance
that it is said to be the ugliest of mammals. Another African form,
the " red river hog" is one of the most beautiful of the Suidae, having
long slender ears and a glossy coat. The collared peccary ox javelin
(hunted on horseback in Mexico) and the white-lipped peccary range
from Mexico into South America, frequenting the upland jungles.

The ruminants are animals that have four parts to their stomachs
and regurgitate the food from the rumen or paunch, chewing it as
the " cud." (See Figure 241, page 434.)

The Chevrotains of India and Africa are hornless forms, resem-
bling both the deer and the pig. They have in some cases four toes
reaching the ground, do not chew the cud, and have simple stomachs
with only three chambers. The " deerlets " have changed but little
since the Miocene period.

The Camelidae are able to retain twenty quarts of water in the
tightly closed water cells of the rumen of their stomachs, and march
for a week over the sanded wastes. Their nostrils are guarded by
valves, their tough cartilaginous mouth permits them to eat thorny
vegetation, and they walk over the sand on padded feet. The hujnp
of the camel is a reservoir of nutriment to the animal and a satis-

402

MAMMALIA

factory human food. The one-humped Arabian camel Is very speedy.
The two-humped Bactnan is short legged, and long haired. It is
especially important in the heat and cold encountered in Mongolia.
Camels were introduced to the United States in 1850 at the Gold
Rush and later purchased for use in the Union Army. The llama
is a Peruvian beast of burden. In Peru, Chile, and South Africa,

Moose

Fig. 228. A, Virginia deer. 5, moose. C, elk. (From L. A. Fuertes. Courtesy of

Slingerland-Comstock Publishing Co.)

the alpaca {el paco)^ a somewhat smaller form, is bred for its valuable
long hair.

The deer family ( Cervidae) are differentiated from the other
ruminants by the presence of bony antlers. The male deer of most
species have solid horns which are shed once a year, close to the
skull, and are fully renewed by rapidly growing out in a soft state

MAMMALIA

403

called the velvet (Hornaday). The first pair of antlers grown during
the second year are two straight, slender spikes (" dag antlers ").
The fully grown antlers branch several times. The American Elk
or Wapiti {Cervus canadensis), tall as a horse, with a beautiful mane
and a pair of large antlers, is termed by Hornaday " The king of the
Cervidae." The elk browses and grazes. The European red deer
are related to the elk.

Fig. 229. Mule deer in "velvet." (Photo courtesy of Canadian National Railways.)

The mule deer or Rocky Mountain " black-tail," (Figure 229) the
largest of the North American " deer," ranges as far east as western
Dakota, preferring a dry climate and a high altitude. It is difficult
to keep in a park. The Virginia deer or " white-tail " deer is a
forest animal noted for its tendency to hunt cover. Its antlers
project forward.

The American caribou is a deer-like animal ranging farther north
than any other hoofed animal except the musk ox. The woodland
caribou shifts away the snow with its flanged horn and feeds on
grasses, moss and lichen. Other caribous include the Newfoundland

404 MAMMALIA

caribou and the barren ground caribou. The domesticated reindeer
in this country were imported from Siberia and Lapland to Alaska.
In the reindeer, horns are present in both sexes. Caribou and
reindeer are readily interbred. The American moose {Alces ameri-
canus) is the largest animal of the deer family, not excluding the
celebrated " Irish elk." It stands over six feet high at the shoulder,
its legs are four feet long and its heavy antlers spread over six feet
in width. The male has a long strip of skin, the " bell," hanging
down from its neck. The female lacks bell and antlers. The musk
deer lacks horns and has musk glands highly developed in the male,
which furnish the basis of many perfumes.

The giraffes {Giraffidae) of Africa, although somewhat like the
deer, have no antlers but short horns covered with hairy skin. The
giraffe, in spite of its tremendously long neck, has only seven cervical
vertebrae. It reaches a height of twenty feet from its front hoofs
to the top of its head. Its eyes are large and its face mild appearing,
although it is adept at kicking in all directions.

The long neck of the giraffe has, according to the Lamarckian
theory, developed as a result of the efforts of the animals to reach
the elevated branches of tall trees. (See p. 514-)

It is believed that the parent stock, the three-horned giraffe
{Giraffe camelopardalis) ^ has given off the other species such as the
two-horned giraffe of Southern Africa and the six-horned giraffe of
Western Uganda. Giraffes are silent, even the female making no
noise whatsoever.

The North American prong-horn {Antilocapra atnericana) has
horns which in the male are branched like those in the deer. The
horns of the female are unbranched. W. L. Finley reports that the
pursued prong-horn antelope runs at a speed of about forty-five
miles an hour.

The cattle family (Bovidae) include the wi/d catt/e, sheep, goats,
the bison, and the antelopes. There are many breeds of domestic
sheep which are used for flesh and for wool. Persian and Astrakan
lambskins are valued in fur trade.^'' The/at-tail sheep of Asia have
a tail that weighs as much as fifty pounds. The Spanish Merino
sheep introduced into Australia, Africa and United States is valued
for its fine long wool. There are six North American species of wild

^^ Tight curled fur from a lamb 3 days old is called " broadtail." The same lamb
at 6 to 10 days of age would give "Persian Lamb Fur." At three weeks the fur would
be sold as Karakul.

MAMMALIA

405

sheep. Both male and female in Dorset sheep are horned, while the
Suffolk breed are both hornless.

The Rocky Mountain Bighorn (Figure 230) is a large strong an -
mal adapted to its life on the mountain top. It is valued for its
massive horns and its flesh. The Chamois of the European Alps,
like the Rocky Mountain goat, is termed a goat antelope. The

Fig. 230. Rocky mountain sheep. (Photo courtesy of Canadian National Railways.)

Rocky Mountain goat is not a true goat, but is our only native goat-
like species. It has very high shoulders, thick legs and a long face.
It lives just above the timber line on high mountains and has ex-
ceedingly sharp hoofs adapted to ice and snow.

The true goats include the Spanish Ibex, the Steinbock of the
Tyrolean Alps and the Persian Wild goat. The goats of Cashmere
and Thibet furnish extremely fine wool, while the Angora goat (Asia
Minor) also furnishes a highly valuable silky hair. In Southern
Europe, herds of goats are driven from house to house and milked
at the customer's door.

The ibex is a large wild goat with horns that extend nearly
straight up in a scimitar-like curve. Formerly found in the Alps,
they are now limited to the Himalaya Mountains, Syria and Abys-

4o6

MAMMALIA

sinia. The Himalayan ibex stands forty inches in height and has
horns that reach a length of fifty inches Another Himalayan goat,
the markhor^ has enormous black twisted horns, five feet in length,
and a yellowish mane over one foot long. It is supposed to be the
ancestor of the Angora goat.

The antelopes^ also Bovidae^ include the koodoos, elands, spring-
bucks, gazelles, hartebeasts, gemsbucks, water bucks and black
bucks found in Africa. Space does not permit a description of these
forms.

Fig. 231. Asiatic ibex. (Courtesy of the Field Museum of Natural History.)

The musk-ox^ found in the frozen north, has a remarkable ability
to subsist on grasses and willows, covered by Arctic snows. The
males have a strong musky odor.

The wild ox of Europe ( Bos primigenius) is one of the ancestors
of our cattle. From this primitive species it is supposed that most
of the English, North German, and Holland cattle have descended.
(See p. 494, Domestication of Mammals. )^°"

The Wisenty or European bison {Bos bonasus), somewhat re-

^""It is related that bullfighting was introduced into Spain from Rome. The
Romans, feeling that it was too brutal a sport to force animals to fight for their amuse-
ment, chose the lesser evil and used gladiators.

MAMMALIA 407

sembles our American bison or buffalo, but is considerably taller.
It is a forest lover. Belated efforts have saved a few wisents in the
Caucasus Mts. The American bison, or " buffalo,'' is not a true
buffalo since it has a hump. It was first seen by white men in
Anahuac, the Aztec capital of Mexico, in 1521. The "buffalo"
once roamed over the plains of the West and migrated from North
to South, thirty-six hundred miles, extending up the Western slope
to the Canadian home of the musk-ox. From East to West it
ranged about two thousand miles. The American Bison Society
has prevented the complete extinction of the buffalo and there are
now a number of flourishing herds.

Yaks are used in Thibet as beasts of burden, while their milk and
flesh are excellent food. Their skins furnish clothing, harness and
tent covers and their hair is twisted into ropes. Their dung is the
only fuel available to the Thibetans, when snow hems them in.

The Indian zebu has a fleshy hump above the shoulders, a devel-
opment of loose skin on the underside of the neck, a short, steep rump
and quite long legs. Different breeds are found in Asia and Africa.
" Brahman " cattle were introduced into the United States in
considerable numbers in 1906, when A. P. Borden imported fifty-one
head from India to Texas. In Texas, as well as in Brazil, pure bred
zebus and hybrids are valued highly since both are free from ticks
and cattle-fever, and remarkably resistant to drouth and heat.

Certain cattle called Podolian are found in Southwestern Russia
(Podolsk) and in Hungary and are said to be descended from the
Giant Ox, Bos taurus primigenius. Mature cows reach a height of
nearly five feet and a weight of twelve hundred pounds, while bulls
are even taller and weigh eighteen hundred pounds. Podolian
cattle are not valued for milk production, but as draft animals.
They are quite resistant to disease.

The True Buffaloes. — The Cape buffalo ( Bos caffer) has thirteen
pairs of ribs like the ox family. The hair of the back is directed
backwards. The African buffalo lives in reedy swamps. Explorers
fear the water-buffalo more than all other African game. The
Asiatic buffalo has the hair directed forwards on the anterior portion
of the back. The Indian buffalo is of large size with widely separated
horns. It is stronger than the tiger and able to combat the ele-
phant. All buffaloes are fond of water and cover themselves with
mud to keep off the gad-flies.

4o8

MAMMALIA

Cattle Hybrids.— One of the oldest of the cattle hybrids has been
that with the I^ison, or " buffalo." (Figure 232.) Potent " cattalo "
males are rarely produced and there is a relatively low percentage of
fertility among the hybrid cows. In the Dominion of Canada, Gal-
way cattle have been successfully hybridized with yaks in an attempt
to produce a stock even more cold-resistant than the hardy Irish
breed. Zebu-cattle hybrids, developed in Louisiana, Texas, and
South America, are important additions to the breeds of beef cattle
since they are disease resistant. The hybrid male is not fertile.

Fig. 232. Cattalo at Wainwright, Canada. (Photo courtesy of Canadian National

Railways.)

Fossil Relatives of the Ungulata. — In the lowest Eocene the fossil
ancestors of the clawed mammals (Unguiculata) are very much like
those with hoofs (Ungulata). Both are five-toed, flat-footed forms
with freely movable fore limbs. One of the most primitive forms
which occurred in the lower Eocene (Phenacodus) reached the size
of a large sheep. In North America the mastodon {Mammut
americanum) appeared in the Pleistocene. The mammoth {Elephas
primigenius), a form whose height was usually less than nine feet,
appears in the Arctic ice of Northern Siberia. The Imperial ele-
phant (£. imperator) reached a height of over thirteen feet. The

MAMMALIA 409

horse family arose in the Lower Eocene of North America, and
Eura'sia. Its descent has been traced from a primitive five-toed
Ungulate. True pigs (Sus) are known from the Middle Eocene.

The giraffes, found from the Pliocene to the present, were not
confined to Africa, but were present in Eurasia as well. The llamas
and camels were found on the North American continent in the
Upper Eocene. Later they migrated into South America, Asia, and
Africa.

Order IX. Sirenia. — Aquatic with moderate-sized head,
depressed fish-like body, paddle-like pectoral limbs, pelvic limbs
absent, horizontal tail fin. No dorsal fin. Integument thick,
wrinkled and hairless. Snout inconspicuous, nostril openings
paired and dorsal; cervical vertebrae unfused, clavicle absent.
Fore legs pentadactyle, often with rudimentary nails; always a
flexible elbow. Brain comparatively small, convolutions ?wt highly
developed. Testes abdominal; teats are two in number and pectoral
in position. Uterus two-horned and the placenta non-deciduate
and zonary.

The dugong is the only Old World Sirenian. It reaches a length
of fourteen feet, and was once so abundant off the coast of Queens-
land that a dugong fishery was established at Moreton Bay (Horna-
day).

The manatee or sea cow reaches a length of twelve or thirteen
feet and a weight of twelve hundred pounds, superficially resembling
a seal. Its tail, a rounded disc, is a powerful propeller. The
Florida manatee reaches a length of about nine feet. Nearly ex-
terminated, a fine of $500 protected it till it is now on the increase.
The flesh of the Sirenia is considered a delicacy by some. Monks in
South America eat all aquatic mammals on fast days, as they con-
sider them fish.

Stellers sea cow {Rhytina), the " Arctic sea cow" furnished food
for Captain Bering when his ship was wrecked on Bering Island in
1741. Steller, the naturalist of the Bering expedition, reported
their length as about twenty-five feet and weight as much as eight
thousand pounds. The species was exterminated in 1854.

Fossil Relatives of the Sirenia. — The sea cows originated in the
Eocene of Egypt, and the West Indies, and were later found in
Europe and America. It is supposed that the sea cows and the
elephants may have been derived from a form occurring in the
Middle Eocene.

4IO MAMMALIA

Order X. Cetacea. — Aquatic with large head, fish-hke body,
thick hairless skin, pectoral limbs paddle-like, pelvic limbs absent,
horizontal caudal fin. So that animals may breathe while feeding,
the larynx is prolonged into a tube extending through the pharynx
to the choanae, from which the nostrils lead directly upwards to the
single or paired external opening. Sole organ of respiration, nose.
Eyes small, external ears lacking, mammae close to sexual opening.
Teeth either present in large numbers, similar and conical; or out-
lined early, then resorbed and replaced by large horny plates of
baleen (whalebone).

Baleen whales are toothless, but have plates or strainers of
whalebone suspended from the upper jaw. The largest of the
baleen whales is the great sulphur-bottomed whale which may reach
a length of over one hundred feet. The " right whales^' also whale-
bone whales, produce excellent oil. The sperm whales have a narrow
beak-like lower jaw with heavy conical teeth arranged in a double
row. They reach a length of eighty feet and could have swallowed
Jonah. Ambergj'is^ used by druggists and perfumers, is formed in
the intestine of the sperm whale apparently as concretions around
the beaks of cuttlefish. It is worth about ten dollars per ounce.
(Figure 123-) Of the 27,566 whales caught in the season 1 928-1 929,
there were 13,650 blue whales. Nearly two million barrels of oil
were yielded. Whale meat is now used extensively for food in
Japan, but Norway leads all countries in whaling and caught nearly
15,000 in 1928-1929.

The dolphin has a slender, cigar-shaped body, a small head and a
long narrow beak. It reaches a length of seven and one-half feet.
Teeth are present on both its jaws. The short-beaked dolphin found
in the Pacific Ocean is the most attractive in appearance. The
porpoise is jet black with a blunt head. It does not reach a length
greater than four and one-half feet, and rarely leaps from the water.
It feeds on herring and menhaden. (Figure 233.)

The narwhal {Monodon monoderos^ reaches a length of sixteen
feet and the male has a long ivory canine tusk twisted from left to
right and extending from six to eight feet. The killer " whale "
{Orca) reaches a length of twenty feet and has a back fin from four
to six feet in height. It kills whales, seals and sea lions, using its
teeth as large as those of the largest whale. Hornaday mentions
one killer " whale " that captured and swallowed alive four small
porpoises. Another observer reported that a single Orca ate

MAMMALIA

411

twenty-four seals off the Pribilof Islands. The black fish reaches
a length of about eighteen feet and has been taken in great quantities
on account of its valuable jaw oil. It is able to elevate itself ver-
tically in the water, standing on its tail. The white " whale "
is found in the far North, where it is said to ascend the Yukon River,
Alaska, for seven hundred miles.

Fig. 233. Side view of porpoise at Woods Hole, Mass. (Photo by Julian Scott.)

Fossil Relatives of the Cetacea. — Certain primitive Eocene
whales seem transitional from early Carnivora. The toothed whales
are found in the Middle Tertiary, and the sperm whales appeared
in the Upper Eocene. Whale-bone whales are known from the
Miocene to the present.

Order Primates. (Lemuroidea, Anthropoidea, Hominidae.) —
The Primates include the Old and New World monkeys and the
most highly developed Primate — man. For the most part the
Primates inhabit a warm climate. Chiefly arboreal in habits, we
find that with the exception of man, they feed on fruit, insects and
birds, and do not engage in the chase after terrestrial prey.

Characteristics. — Primates have from 32 to 36 teeth, a closed
orbit, and two pectoral mammae. They excel in the development of
the nervous system, having large richly convoluted cerebral hemi-
spheres, but are comparatively primitive when bones, muscles,
teeth, and other organs are taken into account. Nearly all are
adapted to an arboreal life; the limbs are prehensile owing to the
pollex and hallux being more or less completely opposable to the
other digits. There are nearly always five nailed digits. Clavicles
are well developed. They have no foramen above the inner condyle
of the humerus and the femur rarely has a third trochanter. The

412 MAMMALIA

stomach is generally simple. The placenta may be non-deciduate,
or deciduate and metadiscoidal.

Lemurs {Le?nuroided), the lowest division of the Primates, in-
clude the tarsier, the aye-aye and the lemurs. They have long,
fox-like muzzles, small ears and 32-36 teeth. In the center of the
upper jaw there is always a toothless gap. The ruffed , or black and
white lemur, the largest of the race, is about the size of a house cat,
has a very long tail, and beautifully soft black and white fur. Other
lemurs, the mouse lemur ^ the dwarf lemur and \\^^ fat-tail lemur ^ are
much less beautiful than the black and white lemur. They aestivate
during the hot dry seasons, living on stored-up fat. The " slow "
lemurs, found in West Africa and East India, are extremely sluggish,
live in trees and eat fruits, insects, birds' eggs and young birds.
The aye-aye of Madagascar resembles a large big-eyed squirrel with
the face of a weasel. It has but 18 teeth, with large incisors and
no canines. Its third finger is extremely slender and elongated and
is used in securing food and in making the animal's toilet. The
female constructs a nest for her single offspring. The tarsier is
found in the forests of Borneo and the Philippine Islands. It is
about the size of a small rat, has a long tufted tail and hind legs
considerably longer than the front ones. Its paws have long bony
digits with pads enabling it to climb smooth bamboo trees. It is
nocturnal, hunting for insects and lizards.

Monkeys. — The Platyrrhina (broad nosed), or American mon-
keys, have a wide space between the nostril openings which are
directed outward. The larger species have prehensile tails.

The marmosets {Hapalidae) are the lowest in the scale of the
American monkeys. They are small, delicate creatures with hair-
less faces, large eyes and very long tails. The hair is abundant and
silky, standing up on the head in a ruff. Their tails are not pre-
hensile. The Saki monkeys are black shaggy-haired animals with
a long black chin beard and a large hairy, non-prehensile tail.
They come from tropical South American east of the Andes and are
of medium size. The owl monkeys, also from South America, have
long, hairy non-prehensile tails and extremely large, owl-like eyes.
The squirrel monkeys are extremely active and nervous and must be
kept in cages. They are arboreal, preferring insects as their food.
The Cebidae, found in South America, have 2^^ teeth, flat nails and
frequently have a prehensile tail. The capuchin, or " ring-tail "
monkey {Cebus), comes from Central and South America. It has a

MAMMALIA 413

white throat and forehead with a brownish or black body. It is
frequently seen in captivity. There are six species of howling
monkeys {Mycetes). They have a large sound-box, developed from
the hyoid bone, and their concerts may be heard more than a mile.
The spider tnonkeys {Ateles) have long slender legs and tails and
small, round heads. Their long, prehensile tails are used to swing
by and with limbs outstretched they do somewhat resemble a
spider. They are found as far North as Mexico. They are fre-
quently carried by organ grinders.

The Old World monkeys ( Catarrhina) have their nostrils close
together and directed downward. Unlike the New World form,
they have open cheek pouches. The tails are non-prehensile or
absent.

Macaques (Fam. Cercopithecidae) have cheek-pouches; range
from one to three feet in length and are found in Asia. The pig-
tailed monkey of the East Indies (a macaque) is trained to throw
down ripe cocoanuts. The baboons {Cynocephalus)^ found in Africa
and Arabia, are the fiercest of the Primates, explorers stating that
hungry lions will not attack them. Their canine teeth are long and
sharp. They go in troops of a score, robbing grain fields, but also
feeding on birds. They are terrestrial but do not walk erect. The
Asiatic holy apes (langurs) represent to the Hindoos, Hanuman, the
Monkey God, who assisted Rama, a mythical hero. The pious
Brahmins protect them so that they are great pests. The wanderoo
of Ceylon and the Nose Monkey of Borneo are other interesting
types. These forms have a sacculated stomach, in the first chamber
of which leaves are stored for a time, obviating the necessity of
cheek pouches.

The anthropoid apes {Simiidae) assume an erect posture when
they come to ground, although they are arboreal in their habits.
They lack cheek pouches and ischial callosities (except in the
gibbon). Their arms are much longer than the legs, they have an
opposable pollex and a vermiform appendix. The gibbons {Hylo-
bates)y the smallest of the man-like apes, are found in the Indo-
Malayan region. They have long jaws with extremely long canine
teeth and their arms are the longest of any of the group. They leap
remarkable distances from branch to branch. Although naturally
timid, they often exhibit surprising courage in the defense of their
young. The Siamang of Sumatra is jet black and has a throat
pouch that distends as the animal shrieks. The brown orang-utan.

414

MAMMALIA

found in Borneo and Sumatra, lives in tree tops, but comes to the
ground for water. It is easily tamed when young, but as it ap-
proaches maturity becomes savage. It is about two-thirds the size
of a gorilla, reaching a height of four and one-half feet. It sleeps
in a nest of broken branches in the fork of a tree.

The gorillas are the largest and most powerful of the monkeys.
They have a tremendous barrel-like chest and massive frame and
are able to aquit themselves with distinction in any battle. Since

Fig. 234. Chimpanzee. (Courtesy of N. Y. Zool. Soc.)

the time of Du Chaillu, gorillas have been regarded as most ferocious
beasts. The late Carl Akeley believed however that the gorillas of
Western Africa rarely attack man unless forced to a fight. Gorillas
reach a height of six feet and weigh as much as five hundred pounds.
The chimpanzee (Figure 234) is a third smaller than the gorilla and
has a large brain and the keenest mind of any ape. It is easily taught
and when young is quite popular with directors of animal films.
The two species of chimpanzees are natives of equatorial Africa.

MAMMALIA

415

Hominidae. — Man resembles the lower vertebrates in general
characteristics and differs less in structure from the higher apes
than do the monkeys. The Hominidae differ from the Simiidae
chiefly in the development of the brain and in those characteristics
associated with an erect posture.

Among the most striking of the characteristics differentiating
man are his increased brain development and power of articulate
speech; reduced canine
teeth, spinal column adapted
to erect posture with four
distinct curves; basin-shaped
pelvis which supports vis-
cera; arms shorter than legs
and with opposable thumbs,
arched (shock-absorbing)
feet. Whether loss of hair
has come from the wearing
of clothes is a subject for
conjecture. (Figure 235.)

Fossil Man. — Human
fossils are very rare, and
when found are either in
river valley deposits or in
those limestone caverns that
served as homes and later as
burial places.

The Java ape-man
{Pithecayithropiis ei'ectiis) ,
consisting of a cranium, a

femur and four teeth, was ^ — g

discovered by E. Dubois in ^^^ ,_^^_ Skeletons of man and of gorilla,
a river deposit at Trinil, (Lull. Courtesy of The Macmillan Co.)

Central Java, in 1891. The

age of the geological formation was estimated at about 500,000
years (Early Pleistocene). The teeth were more human than in
the gibbon and the skull capacity was about two-thirds that of
man. Pithecanthropus erectus was about five feet, seven inches tall.

The Heidelberg jaw, representing the oldest recorded European
race {Homo heidelbergensis), was discovered in 1907 in a gravel pit
seventy-nine feet below the surface, at Mauer, near Heidelberg, S.

4i6 MAMMALIA

Germany, by Dr. O. Schoetensack. The mandible was found fully
equipped with teeth.

The Piltdown man^^ {Eoanthropus dawsoni), found in 191 1 by
Mr. Charles Dawson at Sussex, England, consisted of fragments of
the cranial walls, nasal bones, a canine tooth and a mandible. The
brain case was typically human except for the thickness of the walls.
The forehead was high and lacked the prominent supraorbital ridges
of the Neanderthal man. The jaw was apparently more apelike.

The first specimen of the Neanderthal man was discovered in
1856 near Dusseldorf in Rhenish Prussia. In a cavern high up on
the side of a ravine an entire human skeleton was found, but it was
at first thought to be an idiot soldier from an expedition of Napoleon.
Later ten related skeletons were found in various places in Western
Europe. They were short, the males reaching a height of only five
feet, five inches. Neanderthal man is supposed to have lived during
the third interglacial and fourth glacial periods. The Neanderthal
people were cave-dwellers and made tools and weapons of flint.
They buried their dead, leaving weapons and food for use in the
future world. Whether they were destroyed or amalgamated seems
debatable. One European Professor of Anthropology living a
few decades ago was himself described as a " typical Neanderthal
man."

At Aurignac, France, seventeen skeletons of Cro-Magnon man
were found in 1852, but were buried in the village cemetery and lost
to science. In 1868 five more skeletons were discovered at Cro-
Magnon, France, and shown to belong to a highly developed pre-
historic people. Physically they were superb, some of them reach-
ing a height of six feet, four inches. Their brain was larger than
the average brain of the white race of today. Cro-Magnon men
came from either Asia or Africa and replaced or absorbed the
Neanderthal type. Along with them developed a high type of art
as shown by bone and ivory carvings and cave paintings. Like
the Neanderthal man their burial customs indicate a belief in life
after death. Following the Cro-Magnons and perhaps absorbing
them came migrants from Asia, establishing the narrow-headed

" Osborn, H. F. 1929. Note on the geologic age of Pithecanthropus and Eoan-
thropus. Science, vol. 49, no. 1782, pp. 216-217. Osborn states that Eoanthropus,
the Piltdown man, is now believed to be of greater geologic age than Pithecanthropus
of Java.

MAMMALIA 4I7

Mediterranean and the broad-headed Alpine types which persist
today.

The Peking Skull. — In December, 1929, Mr. W. C. Pei, who was
in charge of excavations at Chou Kou Tien, near Peking, discovered
the skull of a primitive man. It was possible to fix the age of the
Peking Man at the beginning of the Pleistocene (Ice) Age. The
brain was apparently advanced over that of the Pithecanthropus.,
and had a slight frontal bulge. Further study is being made, and
should be most important since the cranium is complete. Pere
Teilhard de Chardin and Dr. Davidson Black are engaged in study-
ing the skull and in searching for eoliths.

Races of Man. — We have chosen from the various classifications
of Homo sapiens a division into three predominant varieties, the
Negro, Mongolian and Caucasian, first describing the most primitive
race now living, probably related most closely to the Negroid.

The Australian race have a chocolate brown skin, long black
wooly hair, a long skull (dolichocephalic), prominent eyebrows, large
canine teeth and are tall with long limbs. They are still found in
Australia and are the most primitive of living men.

The Negroid race have a black or brown skin with short wooly
hair, a dolichocephalic skull with flattened nasal bones, prominent
sloping teeth and thick lips. They are found in Africa from the
Sahara Desert to the Cape of Good Hope.

The Mongolian race have a yellowish brown skin, straight black
hair, scanty beard, a short head (brachycephalic), flat nose, small
oblique eyes and teeth of medium size. They include the Chinese,
Japanese, Tartars, Polynesians, Esquimos, North and South Ameri-
can Indians, Lapps and Finns.

The Caucasian race have a white skin, soft straight hair, a well-
developed chin, thin lips, small teeth and a narrow nose.

(«) The Mediterranean race are short, slender, long-headed with
eyes and hair brown or black. Members of this race, found orig-
inally along the shores of the Mediterranean, are ancestral to the
slender and short-limbed brunets of the British Isles and the
Continent.

{h) The Alpine race are of medium height, round-headed with
eyes gray or brown to black. The Central French, South Germans,
North Italians, Austrians, many Poles, Turks, Armenians and
Persians are of Alpine ancestry.

(r) The Nordics are tall and long headed, with blonde hair, and

41 8 MAMMALIA

blue or gray eyes. They include the Scandinavians, North Ger-
mans, many French and Dutch, English, Scotch, most Irish and the
Americans and Canadians of early immigration.^

Race Mixture and the Evolution of Man. — While it has been
demonstrated in some parts of the world that the offspring from the
union of distinct races are of an excellent type, we are jealously
guarding these United States against swamping our best stock with
poorer lines, Caucasian though they may be. For many years it
was common in some European countries to banish criminals and
defectives, and even to furnish them transportation to the land of
the free. Today we find judges in some of our states most gerter-
ously warning petty criminals to get out of the state (and into
another). But the stringency of our present immigration laws now
prevents many undesirables from entering the country.

Charles W. Eliot thought Zangwill's phrase the " melting pot "
most inapplicable to America. He agreed with the one who sug-
gested a new symbol — " America should be a symphony orchestra,
playing with intelligence, good will, and self control."

Mammals as Migrants. — Relatively few mammals migrate.
Those that do migrate include the bison, reindeer, fur seal, dolphin,
bat and lemming. The bison formerly ranged over North America
from north to south about thirty-six hundred miles; from east to
west about two thousand miles. The reindeer of Spitzbergen mi-
grate to the central portion of the island in summer and back to the
sea coast in the autumn, where they feed upon sea weed. Fur seals
breed on the Pribilof Islands in the Bering Sea, from about May i to
September 15. Then they go out to sea and spend the winter,
making a total circuit of about six thousand miles. The dolphin
travels up the Amoor River for four hundred miles just as the ice
breaks up. Bats have seasonal migrations of considerable distances.
The lemmings of Norway and Sweden are small rodents (relatives of
the mice) about three inches long. Periodically the increase in
their numbers is so great that they migrate down from the moun-
tains and traverse the Scandinavian Peninsula in hordes. It is

1 Brouzas is studying the physical characteristics of the ancient Greeks. He
reports that Inge beheved the Spartans were almost pure Nordics, and the Athe-
nians ahnost pure Mediterraneans. Brouzas holds that the principle of like attracts
like must be accepted, and that the Greeks admired blond hair because they them-
selves were blond. (Consult Brouzas, C. G., 1930, Proc. Amer. Phil. Assoc, vol.
61, pp. xxvi, xxvii.)

MAMMALIA 419

traditional that they devour all the vegetation in their pathway,
and continue to travel overland and across streams until they reach
the sea where they perish. If it were not for their enemies, the
Arctic foxes, weasels, and lynxes, they would ruin the territory
through which they pass.

Homing Instinct. — Many instances are cited indicating the
remarkable ability of the common house cat and the dog to find
their way home after having been transported by train or automo-
bile. Undoubtedly the roving habits of both these animals have
given them a rather wide knowledge of adjacent territory. It is
most difficult, however, to conceive of their finding landmarks a
hundred miles away.

In the savage state, man evinces an uncanny ability in travelling
through forests and swamps, and emergencies have proved to many
a city dweller that he has a well-developed, although unused ability
in that line. Keen, though unanalyzed, powers of observation
prove to be the solution of many unexpected achievements in the
wilds.

CHAPTER XX

Mammalia — Physiology

Man is an animal. We see this more and more as we study the
structure and vital phenomena of other animal organisms. Co7n-
parative Anatomy shows the structure to be comparable and animals
have been grouped in a series ranging from the simple one-celled
animal to man in all his complexity. Embryology shows us that man
conforms to the Law of Development just as inflexibly as does the
simplest invertebrate. Comparative Embryology shows a striking
similarity between the embryo of man in its early stages and the
embryos of other mammals at corresponding periods in their devel-
opment. But it is in the study of the vital phenomena, Physiology,
that we find the greatest similarity. There is a wide variation in the
degree of specialization of organs for certain functions, but there is
in all living animals a property that separates them from the non-
living by a seemingly unbridgeable chasm.

The late Jacques Loeb, of the Rockefeller Institute, artificially
fertilized the eggs of the sea urchin and the starfish by chemicals,
and to his great disgust, the reporters announced that he had pro-
duced life. Jarring, varying temperatures, and differences in the
salinity of the water produce the same effect in Nature. All
sciences have theories regarding the origin of life, but no theory is
without a flaw. Granting that chemicals can be combined to pro-
duce life, we have proved nothing. We have pushed back the ques-
tion a little farther. We have not shown the nature of the phenom-
enon which causes the chemicals to combine. This is life perhaps.
Electricity may be life in one sense. However, we cannot prove the
spontaneous generation of life. We are able to vary conditions in
the case of developing eggs and get different results but we cannot
introduce the spark of life. Lovatt Evans said (1928) in his address
before the British Association for the Advancement of Science:
" Science can not fathom the mystery of life."

Man vs. the Higher Apes

In man and the higher apes the similarity of structure is carried
out even to the finer details of the brain. The brain weight and

420

MAMMALIA— PHYSIOLOGY 421

histological development of the cerebral hemispheres in the higher
apes is about that of a microcephalic idiot. The behavior of the
apes shows many human traits in that capacity for learning and
intelligent acts can be interpreted.

The work of Yerkes (" Almost Human ") and of Kohler has
shown the ability of the chimpanzee, and to a less extent the gorilla,
to recognize complex relations in problems set the animals and has
indicated a capacity to plan solutions and to utilize simple tools.

Man has developed a remarkable reasoning power and has
brought with him a high development of conscience and a religion.
Even the most degraded savage worships something. The dis-
coveries of archaeologists show that wherever human remains are
found, tokens of idol or deity worship accompany them.

Man is continually at warfare with other animals and with his
fellow men. As man's religion and sympathy become more strongly
developed we find that his attitude towards gaining possessions by
aggressive warfare decreases.^

It is necessary for the life of any organism that it be properly
adjusted to its environment. The more plastic the mind, the more
easily does life continue. The very process of education tends to
keep the mind open and to prolong the period of mental adolescence.

Physiology of the Vertebrate Animal

In the vertebrate type of animal we distinguish from a physio-
logical point of view the following principal organs: those of diges-
tiorty respiration^ circulation^ excretion^ reproduction^ muscular system,
which is the organ of movement, and the nervous system, the organ
of control.

The body is made up of a bony framework, the skeleton, with
muscles and fat covered with skin. Food is taken into the mouth,
digested by the alimentary system, the wastes are carried off by the
excretory system, the lungs and the skin, and the sustaining portions
are carried around to the tissues by the ^/oo^ which brings the wastes
from the tissues to the excretory system. The lungs serve to aerate
and purify the blood before its return to the organs of the body.
The interdependence of the various systems calls for a governing and
correlating center, the nervous system. It is constantly functional in

1 " The human animal cannot be aware of beauty except in self-forgetfulness, and
it cannot produce beauty except in self-forgetfulness." Arthur Clutton-Brock.

422 MAMMALIA— PHYSIOLOGY

bringing about rapid readjustments to external conditions, as well
as in keeping the natural relations between the systems and organs.
The organs of digestion include the alimentary canal and its accom-
panying secretory glands, the liver and pancreas, which have as
their function the preparation and absorption of foodo

The organs of respiration comprise the lungs and skin. Their
function is the exchange of gases between the organism and the
atmosphere. The organs of circulation are the heart, arteries, veins,
and capillaries with fluid contents. Their function is distribution
and renovation of blood throughout the organism. The muscle fiber
is the essential element of this system. The main organs of excretion
are the kidneys, which are supplemented by the action of the lungs,
the skin, the liver and the blood. Their function is the separation
of urea from the blood. The active element is the epithelial cell.
The organs of reproduction are the ovaries and the testes. The essen-
tial elements are the ovum and the spermatozoan, both of which
are derived originally from epithelial cells.

The muscular and nervous systems form an organ which is both
master and servant to the entire organism. The nerve centers
receive information through the sense organs and nerves regarding
the outer and inner needs of the entire organism and, acting through
the motor nerves^ bring about muscle activity producing those move-
ments that satisfy the demands of the situation.

The principal nerve centers are the brain and spinal cord. The
principal sense organs are the skin, eye, ear, nose and tongue.
Many of our most important body functions are carried on, without
fret or worry, by the sympathetic system.

Mammalian Physiology

External Anatomy and Locomotion. — For the most part the
mammals are quadrupedal in locomotion. Even in man, the biped,
whose upright posture has been fashionable for ages, it has been
shown that resumption of the quadrupedal method of locomotion
may benefit cases of prolapsed viscera.

The plantigrade animals like man and the bear are usually five-
toed. The digitigrade forms such as the cat are four-toed. In the
horse, a digitigrade or unguligrade animal, the original four toes
(with a rudimentary fifth) have degenerated to a single toe. The
horse and the antelope seem particularly adapted for speedy flight.

MAMMALIA— PHYSIOLOGY 423

Most jTvam-mals except the ungulates have a perfected digitigrade
gait, having developed special sole-pads for the absorption of the
shock. The elephant^ however, is said to be rectigrade, its weight
resting on heavy pads, the foot not moving independently. In the
camel^ the feet are provided with two broad cushion-like pads, while
the hoofs are reduced to nails.

The only tvuQ flying mammals are the bats, but other forms, such
as certain squirrels, are able to plane through the air. Extensions
of the skin on the inside of the fore and hind limbs are drawn taut
when the limbs are extended, and furnish a flat surface.

Some forms like the mole and the gopher are able to burrow in
the ground. In these forms, particularly in the mole, one finds
heavily developed shoulder girdles. Depending on the degree of
subterranean life, one finds degeneration of the eyes.

Certain aquatic mammals such as the whale have undergone
degeneration of the hind limbs, with a great development of the
pectoral appendages for swimming. In marine mammals, we find
that the caudal fin is horizontal instead of vertical and that it has
two symmetrical halves.

C&nfro/ bodies CcenfrosomK)

Oc^g, 6o<:/,B^l,-^y ^ Vc^^Z/co/ layer

PJosmosame or true nucleo/us "^~-T-^ *'j-ii"'A^ ^ *^'r"1

Chromatin "T Tfeul^itSiiSr; -■.*:- -14 Plasfids

Linin

'■^Truc trva/f or membrono

Korvosome or chromatin- nucleolus It-': < ^ , ^ 'a « ^ '•ri ^ . .

Vacuole ff/tjid <^obule)

- Passive metaplosmic or
paroplaatic bodies

Fig. 236. Diagram of a generalized cell. (After Wilson, The Cell in Development and
Heredity. Courtesy of The Macmillan Co.)

Histology. Cells and Tissues. — All living bodies are composed
of organic constituents called cells. In the Metazoa we find one
fundamental characteristic, that of division of labor. Certain cells,
grouped together for the purpose of reproduction, are called germ
cells, while others which carry on all processes except reproduction
are called somatic cells. The argument between the Lamarckian
and the Weismannian schools is based upon the question of possible
influence of environment upon the germ cells. (See page 514.)
(Figure 236.)

424

MAMMALIA— PHYSIOLOGY

A cell is a minute portion of living substance or protoplasm,
sometimes inclosed by a cell membrane, and at some stage of its
development containing a nucleus. It is a physiological unit.
(See page 423.)

When cells, similar in structure and originating from the same
germ layer of the embryo, are grouped together to perform some
special function, they are called tissues.

Fig. 237. Four nerve cells. J and C, from the cerebellum; B, from the gray-
matter of the spinal cord; D, from the cerebrum; a, the axon. The cells J and D are
stained so that the main body and the dendrites (p. 76) are a uniform black; B and C,
so as to show the nucleus and cytoplasm. (Hough and Sedgwick, The Human Mecha-
nism. Courtesy of Ginn and Co.)

We may classify tissues as Epithelial or bounding tissues, and
Connective or supporting tissues. E-pithelium is a tissue which is
distinctively cellular with its cells usually similar in size and form,
and united by a small quantity of intercellular substance. (Figure

237-)

Epithelium is found covering all outer surfaces and all inner

free surfaces and is protective and secretory. It is the first tissue

found in the embryo. Pavement epithelium is found lining the

mouth, on the inside of the lungs, and covering the body. It is

MAMMALIA— PHYSIOLOGY

425

constantly being worn off and replaced. Cubical epithelium is
found in the bronchioles of the lungs and in the ducts of certain
glands of the digestive system. Columnar epithelium is found
lining the alimentary canal of vertebrates and a peculiar type of
" ciliated " columnar cell is commonly found in the trachea and
bronchi and lining the oviduct and the central canal of the spinal
cord. Glandular epithelium consists of epithelial cells so differen-

1A

2A

Fig. 238. Diagram illustrating different forms of glands. Upper row, tubular
glands; /, 2, and J, simple tubular glands; 4, compound tubular gland. Lower row,
alveolar glands; /a, 2a, and Ja, simple alveolar glands; 4a, compound alveolar gland.
(From Bailey's Histology. Courtesy of Wm. Wood and Co.)

tiated as to be capable of forming compounds given off as secretions.
The simplest type of glandular cell is the unicellular gland called the
" goblet " cell. This type of mucus-secreting cell is found in the
hypodermis of the earth worm and occurs also in the intestines of
vertebrates. N euro- epithelium is found lining some of the ven-
tricles of the vertebrate brain. Certain cells are aggregated into
end organs of special sense. The sensory cells are spindle-like with
hair-like processes extending as fine fibers at the inner end and
establishing connection with the nerve. Ordinarily these cells are
surrounded by supporting sustentacular cells. Germinal or repro-
ductive epithelium is found in the gonads. The sexual cells arise

426 MAMMALIA— PHYSIOLOGY

from epithelium derived from the primitive mesoderm or in some
cases from ectoderm or endoderm. When the sexual cells develop
(somewhat as glands form) they frequently starve the adjacent cells.

Connective tissues are derived from the mesoderm. Mucous
tissue is found in embryonic animals. The umbilical cord and the
vitreous humor of the eye are mucous tissue. Reticular tissue is
fibrous connective tissue in which the inter-cellular substance has
disappeared. It is found in adenoid tissue and in lymph glands,
in the spleen, and in the mucous membrane of the intestinal canal.
Fibrous tissue consists of areolar, tendinous and elastic tissue.
{a) Areolar tissue consists of bundles of white fibers with a few
fibrils of elastic tissue. The inter-spaces are filled with lymph.
{h) Tendons and ligaments consist of dense white fibrous tissue. (<r)
Elastic tissue consists of yellow elastic fibers, frequently found in
bundles.

Adipose tissue consists of a matrix of areolar tissue containing
cells, the nuclei of which are a-central.

Cartilage may be hyaline, elastic or fibro-cartilage. {a) Hyaline
cartilage is jelly-like and found in embryonic bones and at the ends
of bones. It has a homogeneous matrix and prominent cells. {]?)
Elastic cartilage is found in the lobe of the ear, in the epiglottis and
in the Eustachian tube, {c) Fibro-cartilage is found in inter-
vertebral substance and in the sesamoid bones. It consists of
groups of slightly flattened nucleated cells enclosed in capsules and
scattered among fibers.

Bone. — Bony tissue may be either compact and dense like ivory
or spongy and cancellous with many interstices. The outer layer
is called t\\Q periosteum. In true bone we find fine fibers in a calcified
ground substance with branched cells, the bone corpuscles., lying in
cell spaces called lacunae situated in folds or lamellae around a cavity
called the Haversian canal. Ramifying passages which contain cell
processes are called canaliculi and radiate in all directions from the
lacunae.

Muscle substance is a specialized contractile tissue which is the
agent of active movement. It is distinguished from undifferen-
tiated protoplasm since it contracts in one direction. In inverte-
brates such as protozoa, sponges, and coelenterates we find primitive
contractile fibrils, but in worms, molluscs and arthropods, muscular
tissue is highly developed. Non-striated or smooth 7nuscle cells
are involuntary. The cells are long, spindle shaped, and somewhat

MAMMALIA— PHYSIOLOGY 427

flattened. Each cell has an oval or rod-shaped nucleus. The cell
substance is longitudinally striated but has no cross striations. It is
found in the walls of the intestine, trachea, and bronchi, the urino-
genital system, blood vessels and hair follicles of mammals and in
the foot of the mollusc. Striated muscle consists of long cylin-
drical fibers made up of fibrils arranged end to end in small bundles
and enclosed by a sheath or sarcolemma. This outer connective
tissue covering is continued into tendons which attach to the skele-
ton. Nuclei are situated in the liquid protoplasm under the sar-
colemma. The striated appearance is due to the presence in muscle
substance of different chemical compounds of protoplasm arranged
in light and dark bars which give a different staining reaction. It is
supposed that the wider bar is the contractile substance.

Cardiac muscle is a peculiar type of involuntary striated muscle.
The fibers consist of primitive fibrils which are aggregated into
oblong masses each with a nucleus in the center. Muscles are well
provided with nerves and blood vessels. In cardiac muscle inter-
cellular bridges are found. (Clark, 1927.)

Skin. — The skin covers the body completely, the epithelium
changing at the openings of the internal passages to a soft delicate
mucous membrane. It varies in thickness, becoming extremely
heavy in man on the palms of the hands and the soles of the feet.
In the cat it is well developed on the pads of the feet and in the
neck region, where it is protective against the bites of enemies.
The skin consists of the epidermis, cuticle or outer skin, and the
dermis, corium or true skin.

The epidermis consists of two layers, the stratum Malpighi and
the horny layer, or stratum corneum. Although bony plates are
lost in the mammals, one finds heavy armor in some forms, the
rhinoceros having a skin over three inches thick. The dermis^
cutis vera or true skin, consists of fibrous connective tissue with
many glands, blood vessels, lymphatics and nerves. The append-
ages of the skin are the nails, and the hairs, with their sebaceous
glands and sweat glands. They are all developed as thickenings
and down growths of the Malpighian layer of the epidermis. The
sebaceous glands are small saccular glands, the ducts from which
open into the mouths of the hair follicles. Both the ducts and the
saccules are lined by epithelium which becomes charged with fatty
material. The sweat glands, so well developed in terrestrial forms,
are much reduced in aquatic mammals.

428 MAMMALIA— PHYSIOLOGY

Claws or Nails. — Claws or similar structures, nails or hoofs, are
found in all the mammals except the Cetacea. They are thickenings
of the epidermis. In the cat there are five claws on each fore foot
and four on the hind foot. The dermis forms a crescentic fold at
the root of each claw.

Hair. — All mammals are born with a thin covering of very fine
hair, lanugo. It can be noted on a child from the day of birth to
two or three days of age, when it disappears. It is replaced by a
protective covering of more noticeable hair, as the child grows older.
The cat has long coarse hairs on each side the nose called vibrissae^
which function as tactile organs. In the marine mammals, although
fetal hair appears, the majority have lost their hair, except for a
few bristles around the mouth. The fur seals retain a thick under
coat of fur — " seal skin." In the white whale and the narwhal, even
the fetus has lost its hair. Those mammals without hair develop
a thick layer oijat under the skin. The skin is richly supplied with
tactile and temperature perceiving corpuscles.

Perspiration. — The body is continually throwing off perspiration
which we term insensible perspiration. Excessive amounts appear-
ing as droplets are termed sensible perspiration. In man, the in-
sensible perspiration is estimated to be from one to two quarts in
twenty-four hours. Increased exercise, pilocarpin, strychnin,
nicotine, nausea or mental excitement will increase perspiration
markedly.

In the dog and the cow with perspiration limited by the nature of
their skins, we find that the muzzle shows evidence of considerable
evaporation. In the horse, it is estimated that about fourteen
pounds of insensible perspiration are extruded in a day, through the
skin, of course.

Digestive System. Mouth. Teeth. — Mammals have two sets
of teeth, the deciduous or milk teeth, and the permanent teeth.
The whalebone whale has a fringe of baleen hanging down from the
upper jaw and acting as a strainer for the small fish and Crustacea
eaten by these monsters of the deep. The duck-mole {Ornithorhyn-
chus) has its teeth composed of thick strong plates.

Salivary Glands. — The mammals possess parotid, submaxillary
and sublingual glands. These glands are serous, mucous and mixed,
but in some animals the submaxillary is mucous and the sublingual
is mixed, while in others the reverse is the process. Salivary glands
are lacking in the Cetacea. The vampire bat has a buccal gland

MAMMALIA— PHYSIOLOGY

429

secretion that prevents the clotting of blood. In man, the watery-
secretion from the parotids contains the enzyme ptyalin^ while the
submaxillary and sublingual glands furnish the viscid mucin.
The salivary glands and the mucous glands lining the buccal cavity
furnish about three pints of saliva in twenty-four hours.

Fig. 239. Section of a portion of a salivary gland, magnified 500 diameters. The
duct d divides into the two branches d' and d'\ one of which ends in the alveoli, a, a.
Neighboring alveoli, a', «', whose ducts are not in the plane of the section, are also
shown. (After Koelliker. From Hough and Sedgwick, Human Mechanism. Cour-
tesy of Ginn and Co.)

Tongue. — The mammalian tongue is well supplied with tactile
and gustatory papillae. The human tongue has three kinds of
papillae. The filiform papillae are the smallest and are scattered
over the dorsal surface of the tongue except at its base. In the
Carnivora the conical tips of these papillae are heavily armed with
horny epithelium, so that it is possible by their use to scrape bones
clean of muscles and even tendons. There are about four hundred
fungi-form papillae found over the middle and front of the tongue.
They are bright red in color. The ariterior portion of the tongue
is sensitive to sweet substances., while the lateral portions are sensitive
to sour and salt. The circumvallate papillae, about twelve in num-
ber, lie near the base of the tongue in a v-shaped group. They are
richly supplied with nerve fibers and specialized sensory cells and
are especially sensitive to bitter substances.

In the mouth the food is divided, moistened, formed into a ball
and prepared for swallowing. Some of the starch, acted upon by
ptyalin, the enzyme of saliva, is changed into maltose.

43°

MAMMALIA— PHYSIOLOGY

The esophagus is similar in structure to the pharynx but with
well-developed mucous glands secreting an oily fluid that lubricates
the canal. In man, it is about nine inches long.

Stomach. — The mammalian stomach is divided into three dis-
tinct regions, the cardiac at the anterior end, the intermediate

Nosal covify —
Pa/of e -
Tongue -

I -Mf -flaso- pharynx

■ Cavity of moui'h
■-Pharynx

■-Openina of larynx

Oesophagus
Go// b/oddei^

, Pylorus

Bi/e duct—

Tr-ans\/erse co/on —
Li\/er --

Hepatic flexure
of colon

Common orifice of b.
and pancreatic duc/s

Duodenum

Ascend ina colon

Caecum

Appendix
Ileum

- Pancreatic duct

^Splenic flexure
' of colon
Pancreas

Descendlncj colon

-r Small intestine

Fig. 240. General view of the digestive system. (Cunningham, D. J., Textbook of

Anatomy. Y. J. Pentland, Pub.)

fundus and the pyloric at the right or intestinal end. A well-
developed pyloric sphincter muscle is situated at the entrace to the
duodenum. The acidity of the chytne^ when it reaches the pyloric
region of the stomach, induces the sphincter to open. In adult

MAMMALIA— PHYSIOLOGY 431

man the stomach is about ten inches long, four inches wide and
deep, and holds about three pints.

Gast7-ic juice is a pale yellow fluid, rich in HCl. It arrests the
process of changing starch to sugar, producing chyme. It contains
pepsin^ which changes albumen and gelatin to a soluble form called
peptone; rennin, which curdles milk; and lipase^ which emulsifies
neutral fats and fatty acids, but has no effect on non-emulsified fats.

Digestive Action in the Stomach. — The action of the saliva upon
starch is arrested, and the larger lumps of masticated food are
broken up into a thick, grayish soup-like chyme which consists of
starch unchanged by saliva; oils and fats set free in the gastric
digestion; undissolved proteins; dissolved proteins; and debris of
indigestible materials such as cellulose.

The small intestine consists of the duodenum situated on the
right side of the body with a wide curve embracing pancreatic
and bile ducts., t\\& jejunufn situated on the left side, and the some-
what constricted ileum which leads to the cecum and the large
intestine. The human small intestine is twenty-three feet in length.

The semi-digested acid food from the stomach, as it passes over
the bile duct, causes a flow of bile and pancreatic juices which tend
to neutralize the acid chyme, but the contents of the duodenum do
not become distinctly alkaline until they have reached a point at
some distance from the pylorus. The valve of the common duct is
closed when the chyme is rendered alkaline, and is opened when the
acid chyme arrives again.

The liver is of a dark red-brown color, situated just below the
diaphragm. It is the largest gland in the body. The principal
function of the liver is the formation of glycogen, sometimes called
" animal starch." The glycogen is given out into the blood in the
form of dextrose, into which it is changed by an enzyme in the hepatic
cells. The liver thus acts as a reservoir for food, storing it up when
it is in excess and expending it gradually to tide over periods of
fasting. The liver forms bile and urea and is most important in the
purification of the blood. The gall bladder, present in the cat as in
man, is not found in all mammals, some rodents lacking it entirely.
It stores up the bile and liberates it periodically, through the bile
duct which enters the anterior portion of the duodenum as the com-
mon bile duct, together with or close to the pancreatic duct. The
liver weighs between three and four pounds in man and secretes
nearly three pounds of bile in twenty-four hours. Bile is alkaline,

432 MAMMALIA— PHYSIOLOGY

greenish yellow In color and bitter to the taste. It is passed from
the bile duct to the duodenum, where it neutralizes chyme and thus
facilitates the action of the pancreatic juice. In higher vertebrates,
bile has a weak ferment that acts on fats, aiding in their emulsifica-
tion. It has slight amylotic and proteolytic ferments. American
packing houses sell gallstones from cattle to the Chinese and Japanese
who use them as medicine.

The pancreas is a rather long narrow organ, pinkish-yellow in
color and situated at the posterior end of the stomach, extending
along its greater curvature. A duct traversing the gland enters the
duodenum via the common bile duct or quite close to it. The
pancreas secretes digestive enzymes and is also responsible for an
internal secretion which regulates the liberation of sugar from the
liver. (See p. 445.)

Pancreatic juice is alkaline, its sodium carbonate neutralizing
the acid food from the stomach. The enzyme trypsin is at first
secreted in the form oi trypsinogen and converted into trypsin by the
action of enterokinase formed by the intestinal glands. Trypsin
converts proteins into amino-acids which are reconvertible into
proteins when needed. Amylopsin {diastase) digests carbohydrates,
thus continuing in an alkaline medium the action of the salivary
glands stopped by the acid gastric juice of the stomach. Steapsin
{lipase) splits fats into soaps, fatty acids and glycerine. Dissolved
fats are absorbed in the intestinal walls and later combined to form
fat in the cells.

The human pancreas secretes about one pound of pancreatic
juice in twenty-four hours. In the pancreas of the cow, which
weighs but seventeen ounces, eleven pounds of fluid are secreted
per day.

Digestive Action in the Small Intestine. — The change of starch
into sugar is resumed; proteins are largely dissolved by the action
of the bile, pancreatic juice, and the intestinal juices. Starch is
converted into sugar and the sugar is in part converted into lactic
and other acids. Fats are emulsified and to some extent saponified
by the steapsin of the pancreas.

The Cecum. — x^t the point where the ileum joins the large
intestine there is a pouch, the cecum^ relatively small in the cat and
man, but large in herbivores, where cellulose is dissolved by bacterial
action. In man, the cecum has attached to it an attenuated vermi-
form appendix^ frequently the seat of inflammation. Foreign sub-

MAMMALIA— PHYSIOLOGY 433

stances, impacted feces, or parasitic worms, such as the pin-worm
(see p. 90), cause appendicitis.

The Large Intestine is divided into the ascending colon, the
transverse colon, and the descending colon which terminates in the
rectum. In the carnivora the large intestine is short; but is well
developed with sacculated walls in the herbivora. The human large
intestine, five feet long, is estimated to absorb four hundred cubic
centimeters of water in twenty-four hours.

Digestive Action in the Large Intestine.— The contents become
slightly acid due to the fermentation of the contents of the intestine.
Beneficial bacteria are very important. Absorption is very active.
The great absorbent vessels are the veins and lacteah. The lacteals
carry chyle to the thoracic duct at the receptaculum chyli. Food
passes through the digestive tract of man in a few hours, but takes
three days in the horse and five days in the cow.

Digestion in the Ruminant (Example: the cow). — The cow lacks
incisor teeth on the upper jaws and is therefore unable to cut it as
she feeds, but rips loose a tuft of grass by pressing the lower incisor
teeth against the upper jaw and giving a jerk of the head. After
rolling the morsel between the molars a short time it is swallowed
down the esophagus to the rumen or paunch.

The stomach of the cow is large, occupying three-fourths of the
abdominal cavity, and holds 45 gallons. It consists of four parts,
the rumen^ the reticulum^ and the omasum^ constituting the pro-
ventriculi; while the abomasum or " rennet " is the true stomach.

The esophagus opens into the stomach on a dome formed by the
rumen and the reticulum and is continued through the reticulum to
the omasum by esophageal grooves.

The rufnen is partly divided into dorsal and ventral sacs. Large
papillae, sometimes reaching a height of one-fourth inch, stud its
brownish mucous membrane. The muscular coat reaches a thick-
ness of one inch. The food is stored in the paunch till a favorable
time for rumination after which it is passed into the reticulum.

The reticulum, or honeycomb, is the smallest of the four parts
and contains mucous folds one-half inch high enclosing four, five and
six-sided spaces (honeycomb) as well as many small papillae. At
the reticulo-omasal orifice, there are small horny papillae, curved
like birds' claws. The muscular coat has two oblique layers. Little
balls of food are prepared in the honeycomb cells and then regurgi-
tated for thorough mastication and mixture with the salivary secre-

434

MAMMALIA— PHYSIOLOGY

tions. The cow moves her lower jaw once in one direction and then
chews the other way. Subsequent to mastication the food is swal-
lowed again and passes through rumen and reticulum to the omasum
or psalterium.

The omasum or psalterium, sometimes called " the maniplies,"
has loo longitudinal folds or laminae which spring from its dorsal
and lateral walls. A dozen of the largest have a convex attached
edge and a free concaved ventral edge. The food is pressed into

ReHculum

Abomasum

Dorsal sac -4

—;/■ Duodenum

' Posterior blind sacs

Fig. 241. Stomach of a ruminant. (Drawn by W. J. Moore.)

thin layers in the spaces between the laminae and reduced to a fine
state of division, by being ground down by minute horny papillae
studding the surface of the folds. From the omasum the food passes
into the true stomach.

The abomasum^ or true stomach, is divided by a constriction into
two regions, the fundus and the pylorus. It has a mucous coat and
longitudinal and circular muscles, strongly developed to form the
pyloric sphincter. In the abomasum the acid gastric juice functions
as in other mammals.

References on the Ruminant Stomach

Reynolds, M. H. 191 i. Veterinary Studies for Agricultural Students.

Macmillan and Co., N. Y.
ScHALK, A. F., AND Amadon, R. S. 1928. PHysiology of the Ruminant

Stomach. Bull. 216, North Dakota Agr. Exp. Sta., Fargo, N. D.
SissoN, S. 1914. Anatomy of Domesticated Animals. 2d ed. W. B.

Saunders Co., Phila.

MAMMALIA— PHYSIOLOGY 435

Chemical Characteristics of Protoplasm. — When we attempt an
analysis of the chemical constituents of living protoplasm, we induce
important changes. By weighing the material before treating it,
and then comparing the weights of all substances determined, we
find that it is possible to learn most of the constituents, except that
all-important one — life. Protoplasm consists of proteins, carbo-
hydrates, fats, inorganic salts, enzymes, water and the " vitamins."

Proteins are compounds with high molecular weights, which
contain carbon, oxygen, hydrogen and nitrogen. Usually the/
contain sulphur, and sometimes phosphorus. They are apparently
a condensation of the molecules of numerous amino-acids and by
hydrolysis they yield amino-acids in different quantities and of
different characteristics.

Proteins differ in their color reactions and are readily classified
by such reactions. Proteins also differ in precipitation reactions.
Some are precipitated by the mineral acids such as nitric, hydro-
chloric, and sulphuric, others by salts of the heavy metals, par-
ticularly mercuric salts. The alkaloidal reagents which precipitate
the vegetable alkaloids are precipitants for proteins. Eggs, rich in
proteins, are used as an antidote for copper, lead or mercury poison,
since they render the metallic compounds insoluble so that they
may be removed by the stomach-pump or laxatives.

Colloids. — Proteins are colloids. The term " colloid " which
comes from the Greek word for " glue " referred at first to substances
like glues and gums, but now is used to indicate finely divided mat-
ter suspended in any medium. Colloids may include liquid dis-
persed in a gas or another liquid or even a solid; or may refer to
solids similarly dispersed. Blood, lymph, bile and the various
digestive secretions are common examples of colloidal solutions.

Proteins, as colloids, do not readily diffuse through membranes
nor go into solution They readily absorb substances however and
in the cell they synthesize and oxidize them. Protein individuality
is such that the blood of one order cannot, as a rule, be transfused
successfully into the circulation of another order without fatal
results. Foreign proteins are apparently incompatible. It is
interesting to note, however, that human blood may be successfully
administered to certain of the anthropoid apes. Clumping together
(agglutination) of blood corpuscles occurs when incompatible blood
is transfused.

436 MAMMALIA— PHYSIOLOGY

Precipitin Reaction. — An interesting test for the detection of
human blood in murder cases is dependent on the solubility of blood
protein. It is said that soluble protein will give the test after a
period of fifty years. The serum of an animal (a rabbit is ordinarily
used), injected with the blood or blood serum of another animal, will,
when added to a homologous serum, precipitate the albumin in the
form of a light flocculent precipitate. (See p. 528, Evidence for
Evolution.)

Carbohydrates consist of carbon, hydrogen and oxygen, and occur
in both the crystalline and colloidal state. Carbohydrates can be
converted into fats. In plants the starches are commonly dis-
tributed, but glycogen is the only example of animal starch. Gly-
cogen occurs in all the growing cells of the animal body, but is
found chiefly in the liver and muscles (see page 444).

There are three chief groups of carbohydrates. The monosac-
charids with one sugar group include dextrose or grape sugar. The
disaccharids include cane sugar, milk sugar and maltose. Several
monosaccharid molecules become united into a polysaccharid. Corn
and potato starch and wheat flour are common examples of polysac-
charids. The monosaccharid, dextrose (C6H12O6), is formed in the
leaf of a green plant from carbon dioxide and water. Plants manu-
facture carbohydrates from carbon dioxide and water. Recently
Professor E. C. C. Baly of Liverpool University has produced sugar
synthetically in his laboratory by utilizing ultra-violet rays on quartz
vessels of water in which carbon dioxide was dissolved. With small
quantities of either iron or aluminium compounds as catalysts (see
page 440) he obtained sugar. In nature, sugar is made through the
action of the sun on chlorophyll-containing plant cells, and from this
sugar other foods are formed by the addition of different chemical
elements. Sugar, then, is the source of all food, and the process
just mentioned, " photosynthesis," is the most important chemical
reaction in nature.

Fats contain carbon, hydrogen, and oxygen in different propor-
tions, containing much less oxygen in proportion to the carbon than
in the carbohydrates. Fats can readily be converted into carbohy-
drates. They are found in seeds and nuts, and in animals occur in
the connective tissue called adipose. Lipins contain carbon, oxy-
gen, hydrogen, and nitrogen, and may contain phosphorus also.
The lecithin of egg yolk is an example of a lipin. Fats of the body
are derived not only from the fatty substances consumed, but are

MAMMALIA— PHYSIOLOGY 437

also formed from carbohydrates and proteins. Fats contain twice
as much heat energy as carbohydrates and are essential in maintain-
ing the proper body temperature.

Substances that contain at some point in the chain two carbon
atoms united by more than one bond are said to be " unsaturated,"
and are able to form additive compounds with the halogens chlorin,
bromin, and iodin. The " iodin number " of an oil or fat is a meas-
ure of its ability to absorb iodin. Unsaturated fats act antienzy-
matically, and undoubtedly function in the animal body in taking
up iodin. Excess fat in the diet may predispose to goiter.

Experiments by Chidester and associates have indicated the
importance of unsaturated fatty acids in the treatment of Vitamin A
deficiency, when combined with ferrous iodide. The author is also
continuing experiments with the idea that the efficacy of wheat
germ oil, hempseed and other oils used in the recovery of animals
deficient in Vitamin E is in part due to their highly unsaturated
condition. The degree of unsaturation decreases rapidly in seeds
during their period of germination. Cocoanut oil has a high degree
of saturation, and is ineffective.

Chemical Elements of Protoplasm. — Carbon compounds are the
primary materials of protoplasm. Carbon unites with oxygen to
form carbon dioxide and water and to liberate energy.

Hydrogen is taken into the bodies of plants and animals in com-
bination with oxygen as water and is also excreted in this form.
Oxygen is found in the free state and unites with various compounds
of protoplasm, the process of oxidation, releasing energy.

Nitrogen is essential to protoplasm. It forms 79 per cent of the
atmosphere. Taken into plant bodies usually in the form of
nitrates, the plants utilize it in the manufacture of proteins. Am-
monia, a nitrogen compound, formed in the catabolism of plants and
animals, is changed by certain bacteria into nitrates which are then
absorbed by plants.

Mineral Salts. — Proteins, carbohydrates, and fats are not the
chief foods of man. The most important foods are mineral salts,
water and air.^ If mineral salts are withheld from the body, death
ensues much more quickly than from the withholding of proteins,
carbohydrates, and fats. The salts of the body in solution aid in
providing the proper medium for living tissues while those in com-
bination with organic substances furnish the proper elements for

^ Of course not all food constituents necessary to man have been evaluated.

438 MAMMALIA— PHYSIOLOGY

the formation of tissues. The mineral salts are necessary to main-
tain normal physiological equilibrium and purposeful activity in the
organism.

Sulphur is absorbed by plants and used in the manufacture of
some amino-acids. Phosphorus is essential to the formation of
nuclein and lecithin of living cells. Calcium salts are necessary in
the coagulation of blood and milk. Apparently the normal beating
of the heart depends on the relationship of calcium to sodium and
potassium salts. The condition known as rickets is due to a failure
to maintain the proper ratio between the calcium and phosphates of
the food. Cod liver oil is a cure for rickets (see page 443, Vitamin
D). Silicon and fluorine are required in small quantities for the
proper formation and growth of bones and teeth. They are secured
from milk and fibrous vegetables. The ash of hair shows 40 per cent
of silicon dioxide. Sodium as NaCl is essential to herbivorous
animals, but the carnivores do not take salt. Raw meat protects
the Greenland Eskimo from scurvy, rickets, and avitaminosis.

Chlorine is important to the animal in maintaining the secretion
of gastric juice and in keeping the optimum osmotic pressure. The
acid-secreting cells of the stomach select for their use the NaCl of the
blood. Potassium salts are indispensable in the synthetic processes
of organic combination. They aid in the formation of glycogen
from glucose, of fats from glycogen and of proteins from peptones.
The liver, the source of glycogen, contains twice as much potassium
as sodium. Potassium is found in red blood corpuscles and also in
the brain and is apparently necessary to the normal function of
organic life. Magnesium is found in greater quantity than calcium
in the muscular tissues and the nervous system. The salts of
magnesium aid in the formation of the albumin of the blood, reduce
foreign matter and waste and maintain the osmotic pressure of the
blood. Irradiation with ultra-violet light is said to decrease the
magnesium content of rats. Magnesium requires the presence of
calcium salts for proper function and is in fact injurious in the ab-
sence of calcium. An excess of magnesium in the blood is said to
cause glycosuria. Magnesium has been proved necessary for the
growth and maintenance of white mice. The chlorophyll of green
plants is always associated with magnesium. Copper.^ found in the
earth in metallic form, occurs in minute quantities in most vegetable
and animal tissues. It 7nay act as a catalyzer in the production of
hemoglobin.

MAMMALIA— PHYSIOLOGY 439

lodin. — It has long been known that iodin is extremely important
in connection with the normal functioning of the thyroid gland
and that the latter is a powerful regulator of metabolism. It in-
creases the rate of oxidation. Minute quantities of iodin are neces-
sary, the human thyroid containing about one-fifteenth of a grain
of iodin, but lack of the essential amount may cause a disease known
as cretinism in which bodily and mental development are both
subnormal. Iodin is an important constituent of vegetable foods
and is found in large quantities in the plants and the animals of the
ocean. In all probability it is in part responsible for the preserva-
tion of the carnivorous Eskimos of Greenland. It has been suc-
cessfully used in the treatment of pernicious anemia, given as
thyroid extract.

Recent discoveries would seem to indicate that the iodin-fat
balance is important in several of the so-called vitamins, and that
the effectiveness of cod liver oil in certain diseases is really due to
the very small quantities of iodin present. The author of this text
would also like to link the iodin-fat balance with his own theory
of Fish Migration, since it is possible that the eel, fattened in fresh
water, may need iodin to induce development of its gonads, while
the anadramous fishes, like the salmon, possibly need to seek water
of lower iodin content and finally to go into fresh water before their
iodin-fat balance is reached, and eggs mature. (See page 263.)

R. McCarrison (1919) and later the Mellanbys (1921) have
emphasized the importance of iodin-fat balance in goiter, but until
certain studies on the Vitamins were made (Chidester, Eaton,
Thompson, Speicher, and others, 1928-) the significance of their
finding was not appreciated.

Arsenic^ found in the earth as a sulphide, occurs in minute
amounts in animals and vegetables. Gautier and more recently
Bertrand have emphasized the importance oi arsenic as a constituent
of the living cell. The yolk of the hen's egg usually contains twice
as much arsenic as the white. Arsenic enters into the composition
of the epidermis and its appendages, the thyroid and the mammary
glands, and the central nervous system. Arsenic resembles phos-
phorus in its chemical affinities. It is reported that the Tyrolean
mountain climbers habituate themselves to quite considerable doses
of arsenic, for its energizing effects.

Iron is an important constituent of both plants and animals. It
Is necessary for the formation of chlorophyll In plants. Without

440 MAMMALIA— PHYSIOLOGY

the iron in blood, oxygen could not be carried to the tissues. Iron is
requisite to oxidative processes and is contained in hemoglobin.
With an ample supply of calcium^ the body needs less iron. Lack
of iron leads to insufficient nutrition, anemia, and death. Certain
wave-lengths of ultra-violet light increase the blood content of iron.
Although not a constituent of the chlorophyll molecule, iron acts
as a catalyzer in the production of chlorophyll. Millikan has said,
" From an engineering standpoint, the universe may be said to be
made up of the primordial positive and negative electrons, and of
four elements built out of them; namely, helium, oxygen, silicon,
and iron."

Manganese. — Lindow and Peterson have presented data (1927)
on the manganese content of eighty-four materials, covering the
principal classes of human foods. Pineapples, beet-tops and blue-
berries contained relatively large amounts (122-134 mgm.). Hog
liver contained 12.2 mg. per kilogram of dry material while beef
spleen and round steak contained none. The liver of young animals
is the storehouse for the body's reserve of manganese and other
mineral elements apparently necessary for the maintenance of
physiological equilibrium. The human body contains only one-
half ounce of manganese, but a deficiency results in disease. McCar-
rison reports (Ind. Jour. Med. Res., vol. 14, p. 641) that daily doses
of manganese chloride, 0.0327 mgm., caused accelerated growth in
rats, especially marked in the males. Manganese is said to increase
in amount as plants grow older.

Bromine^ boron^ zinc, and aluminium are present in small quanti-
ties in plants and are important to the life and growth of the plant.
Their exact significance as food for the living animal is not fully
understood. Bradley (1904) found zinc in the blood of the gastro-
pod Sycotypus {Fulgur) canaliculatus.

Enzymes are produced in living cells, some of which, the glands,
are specially modified to produce important bodily secretions (pan-
creatic juice). Enzymes are able as catalysts to hasten chemical
reactions, but do not form a part of the end products of the reaction.
An example of catalysis to which we have already referred (page
436) is that of iron which in the presence of light hastens the com-
bination of hydrogen and oxygen to form water. The genes are
said to act as auto-catalysts in that they increase their own sub-
stance prior to each mitosis. (See page 500.)

MAMMALIA— PHYSIOLOGY

441

Nutrition and Vitamins. — Since 191 1, a great mass of literature
has accumulated, largely consisting of the further enumeration of
food substances characterized as belonging to groups of vitamins.
The wholesale advertising of essential foodstuffs such as milk and
green vegetables has resulted most favorably. A fuller appreciation
of the virtues of cod liver oil and the tremendous importance of the
ultra-violet and infra-red rays has also been a product of vitamin
study. But perhaps too much time has been wasted in biological
tests of foods long known to be chemically allied.

Fig. 242//. Rat in advanced stage of xerophthalmia due to lack of Vitamin A.

(Courtesy of Eli Lilly & Co.)

Vitamin A is found in cod liver oil, butter, cream, cheese, whole
milk, egg yolk, liver, heart and kidneys, spinach, lettuce, cabbage,
tomatoes, carrots, sweet potatoes, parsnips, green peas, and many
other substances. Deficiency in Vitamin A results in an anemic
condition, with failure of ovulation and retardation of growth. The
sense organs are diseased and pus laden, the eyes being typically
affected by xerophthalmia with conjunctivitis and corneal degenera-
tion. Vitamin A is fat soluble. Exposure to the air and forced
oxygenation renders it inactive. Commercially canned tomatoes
(no oxidation) were as rich in vitamins at the end of three years as
fresh tomatoes. While it is generally considered that the vitamin

442

MAMMALIA— PHYSIOLOGY

is completely recoverable from the unsaponifiable fraction of oils
and fats that contain it, the writer is convinced as a result of experi-
mentation that there are really two factors in Vitamin A, one which
aids in curing or preventing the keratinizations characteristic of
Vitamin A deficient animals and drawing on the stored up fats of the
animal body, while the other, a factor belonging to the unsaturated
hydrocarbons and fats, is the growth factor.

It may be significant that carotin (C40H56) is an unsaturated
hydrocarbon, and that it is transformed by the rat into Vitamin A,

when furnished in arachis oil,

itself unsaturated. In those
cases where carotin and even
chlorophyll have been able to
induce growth in Vitamin A
deficient rats, it is worth men-
tioning that the experiments
were not run long enough to
determine the point where the
vitamin substitute ceased draw-
ing upon the stored up foods of
Fig. 1±iB. Pieeon with polyneuritis , • i> 1 j ^r^i

r„ . J- . J c • . • \j-i ■ v> the animals own body, ine

lollowing a diet dencient in Vitamin a. ■'

(Courtesy of Eli Lilly & Co.) writer holds that the complete

Vitamin A contains both the
catalyzers and the growth factor, and includes iodin, (ferrous) iron,
and unsaturated as well as saturated fats.

Vitamin B is found in the heart and kidneys of animals. It is
not found in the meat of chickens, turkeys, ducks and guinea fowls.
It is most abundantly distributed in roots and tubers and all green
plant tissues. Cereals and the germs of seeds, yeast and wheat
germ contain it. In man the disease known as beri-beri, with a
failure of some nerves to function, and a disturbance of the appetite
and digestive processes, results from eating polished rice. There is a
resultant atrophy of the lymphoid tissue, and an hypertrophy of the
pancreas, Spleen and certain other glands of the body. In birds a
disease called polyneuritis is caused by similar lack of the seed coat
in food. Vitamin B is soluble in water and alcohol. It is destroyed
by high temperature (130° C).

There has been so much confusion over the terminology con-
nected with the factors contained in Vitamin B that a Committee on
Vitamin B Nomenclature has recommended (Science, vol. 69, p. 276,

MAMMALIA— PHYSIOLOGY 443

1929) that the term " Bios " be used to denote the factor encourag-
ing the rapid growth of yeast cells; that the term " B " be used to
designate the heat labile, antineuritic factor; that the term "G"
be used to denote the heat stable, water soluble, dietary factor called
pellagra preventive^ which has to do with maintenance and growth.
Alcoholic extracts of yeast lack the pellagra preventive.

Evans and Lepkovsky showed that the glycerides of the saturated
lauric, capric and myristic acids were beneficial to animals deprived
of the anti-neuritic Vitamin B. In the treatment of " black-tongue "
in dogs, which he considered the analogue of human pellagra^ Gold-
berger had, without emphasizing its importance, added " syrup
iodide of iron, U. S. P." to the successful diets. Perhaps Vitamin
B may also involve the fat-iodin balance.

Vitamin C, the anti-scorbutic, is found in lemons, oranges,
tomatoes, cabbage, lettuce, spinach, green beans, peas and turnips.
Oysters are rich but meat is poor in Vitamin C. Deficiency in
Vitamin C causes a disturbance of respiratory and circulatory
systems, loss in weight, necrosis of the teeth, with swelling of the
gums, and the bones become friable. The disease known as scurvy
may continue to hemorrhages and death. Infantile scurvy occurs
in children brought up on proprietary foods. Vitamin C is soluble
in alcohol and is destroyed by heat in the presence of oxygen,
especially in an alkaline solution. Tomatoes, cooked in the can,
are found to retain the Vitamin, and canned spinach is reported to
be equal to orange juice in its Vitamin C content.

Vitamin D controls lime and phosphorus utilization in the
formation of bone. It was formerly included under Vitamin A.
Egg yolks, cod liver oil and whole milk are rich in it. The mercury
lamp and the sun are effective in activating it in the body and in
foods. Irradiated ergosterol is an important source for experimental
work at present. Absence of Vitamin D produces " rickets " and
bone deformity. It is soluble in alcohol and oils.

Excess of Vitamin D leads to an excessive precipitation of cal-
cium in the body. An imbalance between calcium, sodium and
potassium might be injurious, and iron assimilation might also be
affected by excess calcium. Commercial preparations of irradiated
ergosterol should be used only under the direction of a physician.

Vitamin E, which prevents sterility, is found in all natural foods.
It is especially abundant in lettuce and the germ of seeds, but is also
found in milk and meats. It is concerned in the normal function

444 MAMMALIA— PHYSIOLOGY

of the placenta, and perhaps related to the metabolism of iron. It
is not affected by ordinary temperatures.

The writer holds that resorption of the young in female rats on a
Vitamin E deficient diet is really an iodin effect, comparable to that
induced in a shorter period of time by excess iodin. Wheat germ
and hemp seed oils that are so effective in the treatment of Vitamin
E deficiency are rich in the highly unsaturated fatty acids during
their effective period. The effectiveness of these oils is lessened as
the period of germination advances and the oils become more
saturated. (See page 437.)

What Are Vitamins? — The author holds that the " vitamins "
are really proper combinations of minute quantities of chemicals
that are functional as catalyzers, and make available not only the
proteins, carbohydrates and fats that are in combination with them
in food-stuffs, but that they also furnish the proper medium for the
liberation of food-stuffs stored in the organism. The influence of
these potent chemicals is felt in all glandular function, and particu-
larly of course in the activation of the endocrine glands.

The Organs of Internal Secretion. Endosecretory Glands with
a Duct. Testis. — In addition to sperms, an external secretion, the
testes furnish an internal secretion responsible for the male secondary
sex characters. Steinach found that transplantation of the testes
into spayed female guinea pigs induced masculinization. Lydston
and others have transplanted human testes, with temporary benefit.^

Ovary. — The ovary produces eggs and regulates the female
secondary sex characters. In the fowl Goodale found that removal
of the ovary causes the bird to take on male plumage. Domm found
that a compensatory testis-like structure developed on the right side.
Steinach found that castrated male guinea pigs could be feminized,
by implanting ovaries in their body cavities.

In early or normal menopause, and in epilepsy, ovarian extracts,
notably corpus luteum and folliculin extract, are beneficial. Allen
and Doisy have cured some cases of sterility with follicular liquid.

Liver. — The liver secretes bile externally, and produces glycogen^
a " negative internal secretion " which is an important body food,
and transforms harmful ammonia into harmless urea. A hormone
extracted from liver has been most successful in the treatment of
pernicious anemia.

^ Consult Moore, C. R. 1926. Qu. Rev. of Biol., vol. i, pp. 4-50.

MAMMALIA— PHYSIOLOGY 445

Pancreas. — The digestive enzymes of the pancreas act on pro-
teins, carbohydrates and fats. The internal secretion,(^£^£r£^^
successfully isolated by Banting^ and associates in 1922, was secured
from the Islands of Langerhans of the pancreas of fetal calves.
J. J. Abel has since then prepared pure crystalline insulin, so power-
ful that only i/ioo of a grain is the daily dosage for a diabetic.
Many lives are now saved annually by the use of " insulin."

Endosecretory Glands without a Duct. Thyroid. — The thyroid
glands contain ten times as much iodin as any other organ in the
body. Iodin in food and water must be optimum, or goiter may
result. The thyroids stimulate carbohydrate and calcium metab-
olism and bear an important relation to body fats. Pioneer studies
by Gudernatsch with tadpoles indicated that if fed thyroid extract,
they metamorphosed rapidly into small toads. Uhlenhuth has
shown that anterior lobe substance from the pituitary gland will
stimulate the thyroid and induces precocious metamorphosis in
amphibia. In hypersecretion of the thyroids, goiter or exophthalmic
goiter may result. In the latter, the eyeballs protrude and the pulse
is greatly accelerated. Hyposecretion results in colloid goiter, cretin-
ism, or myxedema. Cretins are dwarfed, with low mentality, and
are frequently deaf mutes. Myxedema (mucous fat) is accompanied
by great increase in weight, retarded bone growth, brittle teeth,
slow pulse, thickened, wrinkled skin and slow metabolism. Thy-
roxin (Kendall) and thyroid extract have been used in the treatment
of cretinism, myxedema, and endemic goiter. It is dangerous to
start to furnish a community additional iodin in drinking water,
as some goitrous persons may be injured. But the campaign of
education about the importance of sufficient iodin in food and water
(McClendon, Minnesota; and the South Carolina Board of Health)
is admirable.

Applying the discoveries of Bloor, Hill, Sperry and others that
under certain intestinal conditions iodin may be discharged from the
body in considerable quantities in \\iQ feces, Chidester has suggested
that in the cases of water-borne goiter recorded by McCarrison and
others, it is quite likely that certain bacteria will cause the liberation
of iodin and that subsequent demands made on the thyroid by the
excess of unsaturated fatty acids in the intestine will cause thyroid

1 But Banting and Best in the Journal of Laboratory and Clinical Medicine,
1922, Vol. 7, p. 467, gave full credit to E. L. Scott for his pioneer studies, described
in 19 1 2 in the American Journal of Physiology, Vol. 29, p. 306.

446

MAMMALIA— PHYSIOLOGY

hypertrophy. Possibly disturbance of the calcium-iodin balance
will also account for non-bacterial cases due to water.

The writer cannot resist the opportunity to again pay tribute to
McCarrison for his initial discovery of the significance of the iodin-
fat balance and to deplore the fact that it is now receiving such
belated recognition, more than twelve years after its discovery,
in 1919.

Internal Jugular vein j-r^K "

Middle thyroid vein —
Inferior thyroid vein-—.

Thyroid

— Common carotid

Median furrovi/
of thymus

Lun^-

FiG. 243. The thyroid and thymus in a child of six months. (Sappey.) (Schafer's
Text Book of Mic. Anat. Courtesy of Longmans, Green & Co., London.)

Parathyroids. — The parathyroids have been operatively removed
with the thyroids, and death ensued, after a condition of tetany.
The parathyroids influence calcium metabolism, and also affect
sugar metabolism, and aid in preserving the nitrogen balance.

Thymus. — The thymus gland degenerates at puberty, and may
be concerned with both the thyroids and the gonads. Soli, and
later. Riddle, believed that the thymus was concerned with calcium

MAMMALIA— PHYSIOLOGY . 447

metabolism and shell formation in the birds. Crew reported (1928)
that removal of the thymus had no effect on calcium metabolism
in fowls.

Snp7'arenals. — It has long been known that the suprarenal
glands are essential to life. The suprarenal medulla is the source
of epinephrin (adrenalin) which was the first hormone to be isolated
chemically (Takamine) and is extremely potent, one part in eight
billion producing reaction in the rabbit intestine. Wheeler and
Vincent found that as long as an adequate amount of cortex sur-
vived, destruction of all of the medullary tissue led to no ill effects.
Addison's disease is caused by pathological changes in the cortex
and is characterized by reduced blood sugar, subnormal temperature
and a peculiar pigmentation of the skin, with muscular weakness.

In October, 1927, Rogoff and Stewart described the results
obtained with 0.9 per cent NaCl or glycerol extract of the cortex.
They treated completely adrenalectomized dogs. Of thirty dogs
treated, six lived longer than the longest of the control animals.
They did not give the average survival of treated animals as com-
pared with controls, which should have been done. In the same
month, 1927, Hartman, MacArthur and Hartman described the
first method for preparing an epinephrin-free extract of the adrenal
cortex. By the use of such an extract, the average survival period
of completely adrenalectomized cats was markedly increased (21
days) over that of controls (6 days). This average included all
cats treated, even those complicated by infections.

In March, 1930, Swingle and Pfiffner described a method of
preparing a concentrated extract of the adrenal cortex sufficiently
potent to maintain the lives of adrenalectomized cats indefinitely.
Their process was very complicated and their extract contained
much epinephrin and inert material. In June, 1930, Hartman and
Brownell described a much simpler method of preparing a concen-
trated extract of the adrenal cortex containing less than i : 100,000
epinephrin. With this extract it is possible to maintain the lives
of adrenalectomized cats indefinitely. One animal was kept alive
for 268 days, dying because the extract was discontinued. This
substance, found in the adrenal cortex, which is essential to life,
has been called cortin. Both Swingle and Hartman have furnished
extracts to clinicians who have successfully treated cases of Addi-
son's disease with them.

Suprarenal virilism is found in some women with diseased

448 . MAMMALIA— PHYSIOLOGY

adrenals. Cannon ^ demonstrated the effect of increased suprarenal
activity on blood sugar, muscular activity, and recovery from
fatigue. Fear or anger enables one to fight better or run faster!

Pineal Body {Epiphysis). — In cases of pineal tumor, causing
deficient secretion, there is a tendency to obesity and individuals
may be sexually precocious with premature ossification of the bones.
Pineal extract has been administered to cases of retarded mental
development, with reports of gratifying improvement. But we
really know very little about pineal function.

Pituitary Body {Hypophysis). — The pituitary has two lobes, an
anterior one and a posterior one, each with distinct functions. In
cases of hypersecretion of the anterior lobe., acromegaly and gigantism
may result. The hair is excessive, teeth are widely separated, the
extremities are elongated and the fingers become broad and spade-
like. The skin is thick and wrinkled and the sweat and sebaceous
glands are excessively active. Glycosuria and excessive gonadial
development may also occur. The stimulating influence of anterior
lobe substance on the thyroids has already been noted (p. 445)-

P. E. Smith and E. T. Engle (Am. Jour, of Anat., vol. 40, pp.
159-217, 1927) have shown that the implantation of anterior
hypophyseal substance in infantile female rats and mice will induce
sudden and extensive ripening of the Graafian follicles. After 3
days of implantation they induced the ripening of 48 ova in a 22-
day mouse. There is correlation between the sizes of rabbits and
the number of young. Larger breeds are thus affected in growth and
ovulation by the anterior hypophysis. Hyposecretion of the anterior
lobe results in infantilism, obesity, a thin, smooth, dry skin, scanty
hair, slender fingers, and dwarfism with the torso longer than the
extremities. The oxidative metabolism is low.

Hypersecretion of the posterior lobe causes contraction of the
smooth muscles, resulting in a rise in blood pressure. Pituitrin
is used in obstetrics since it keeps smooth muscle contracted longer
than does adrenalin. Sugar tolerance is decreased in hypersecretion
of the posterior lobe. Hyposecretion of the postej'ior lobe results in
subnormal temperature, increased sugar tolerance and adiposity
accompanied by drowsiness (Dickens' fat boy). Epilepsy fre-
quently occurs.

^ Consult Cannon, " Bodily Changes in Pain, Hunger, Fear and Rage."

MAMMALIA— PHYSIOLOGY 449

Dr. Oliver Kamm reported^ (December, 1928) the isolation of
two hormones from the posterior lobe of the pituitary. The alpha
hormone is effective in obstetrics, contracting the uterus, while the
beta hormone raises blood pressure and also controls the excessive
output of water and its utilization in the body tissues. Fleshy
people (the physiological wets) are extremely sensitive to the
action of the beta hormone, while slender scrawny ones (the physio-
logical drys) quickly return to normal after the administration of
this hormone. Both hormones act immediately to increase the
sugar of the body and thus offset an overdose of insulin.

References on the Endocrines

Barker, L. F. 1925. Endocrinology and Metabolism. D. Appleton

and Co.
Cooper, E. R. A. 1925. The Histology of the More Important Human

Endocrine Organs at Various Ages. Oxford University Press.
DoDDS, E. C, AND Dickens, M. A. 1925. The Chemical and Phys-
iological Properties of the Internal Secretions. Oxford University

Press.
Falta, Wilhelm, and Meyers, M. K. 1923. Endocrine Diseases.

P. Blakiston's Son and Co.
Sharpey-Schafer, E. The Endocrine Organs. Part I, 1924, and Part

II, 1926. Longmans, Green and Co., Ltd.
Vincent, Swale. 1925. Internal Secretion and the Ductless Glands.

Physicians and Surgeons Book Co.

The Circulatory System. — The blood vessels are a system of tubes
completely closed except where the lymphatics open. In one place
the system is dilated into a large complexly formed rhythmically
contractile organ, the heart, which is the central portion of the
circulatory system and, according to the studies of O. C. Glaser
(193 1), works basally against the resistance offered by the system
of enclosed tubes. According to the author, objections may be
offered to this view because of its apparent simplicity which does
not seem to take account of the numerous influences which may
temporarily modify the tubal resistance. There are several kinds of
channels in which blood flows: (i) Vessels taking blood from the
heart — arteries. (2) Vessels taking blood to the heart — veins. (3)

2 Kamm, O. Science, vol. 67, p. 199, 1928; J. Am. Ch. Soc, vol. 50, p. 573;
Science, vol. 69, p. 85, 1929.

450

MAMMALIA— PHYSIOLOGY

^^xfernol maxillary

/Posterior auricular
Liricjuo/

Musculan's
Thyroid

Thyrocervicol
Brachial
Left carotid
Vertebral
Costocer vicol
/nternal mammary
M&dio^tinal
Left subclai^ian
Ihhominate

Ductus botalli
Pulmonary
Brorichiol
Ttiorocic aorta

■Coronary
Heart

Intercosto/

■T- Oostr/ca sinistra

Hepatic

Coe/ioc

Superior mesenteric
-Abdominal aorta
-/^brenic

— Ad re no- /umbolis
Suprarenal gland

Reno/

— Kidney ^ ^ „

— Ovarian (or spermatic)
Lumbar

■Inferior mesenteric

//ioiombal/s

-External iliac

-Caudal

-Internal Iliac or tiypo<jastric

-Epigastric

.t^emoral

■Deep femoral

Fig. 244. Arteries of the cat. (Drawn by W. J. Moore.)

MAMMALIA— PHYSIOLOGY

451

jrrS;

Anterior' foc'iot

Trons\/erse
Posferior fac/al
fnterno/ Ju<]Ular
Inferior thyroid

Supra - scopti/or

3ubclov/an

- Costocervicot
Verfebral
Inferno/ mammary

Precavat

Azygos

Intercosfal
Coronary

Postcaval

Phrenic

Hepatic

Veins of liver
Portal

A drenolumbalis

Renal

0\/orion (or spermatic)

Lumbar

I/iolumbo//3

Common iliac

Caudal

fnterno/ iliac or hypogastric

Epigastric

Femoral

Deep femoral

Fig. 245. Veins of the cat. (Drawn by W. J. Moore.)

452

MAMMALIA— PHYSIOLOGY

Vessels conveying blood to tissues and intervening between arteries
and veins — capillaries.^

The heart is a thick, muscular, hollow organ with great blood
vessels originating from the broad anterior part. It is enclosed in a
sac of fibrous tissue lined with epithelium called the pericardium.
It consists of 4 chambers, 2 of which are called auricles and 2
ventricles.

The auricle and ventricle of the right side are completely sepa-
rated from those of the left side. The auricles open into the ven-
tricles by valved apertures and valves guard the openings of the
great vessels. Between the right auricle and right ventricle is the
tricuspid valve. Between the left auricle and the left ventricle is the
mitral or bicuspid valve. Between the auricles is a partition (auricu-
lar septum). Between the ventricles is the ventricular septum.

X i6oo X 750

Fig. 245^. Red and White Corpuscles of Human (Left) and Frog (Right) Blood.

* (Drawn by Norris Jones.)

There are two large veins which empty into the right auricle.
The superior vena cava descends, while the inferior vena cava ascends.
The coronary veins come from the heart substance itself. Into the
left auricle, four pulmonary veins enter, two coming from the right
and two from the left lung.

From the right ventricle arises the large pulmonary artery
which divides into a branch for each lung. From the left ventricle

^ In the portal system (page 453) the capillaries in the liver intervene between the
hepatic portal vein and the hepatic veins.

MAMMALIA— PHYSIOLOGY

453

the large aorta originates. These arteries are guarded by semi-lunar
valves which consist of three pouches with the convex side towards
the ventricle.

Action of the Heart. — The right ventricle pumps blood through
the lungs, while the left ventricle forces it through the rest of the
body. Closely following the contraction of the auricles is the con-

Poncreotico-_
duodenal vein

Doodenurn ■

Pancreas

Post cayal vein

Phrenic vein

— Oo 5 fro- epiploic vein

— Coronary vein
— Portal \^ein

-Dorsal surface
of stomacft

-Oosfro- splenic vein

Anterior mesenteric vein

Posterior mesenteric vein

Spleen

Fig. 246. Portal system of the cat. (Drawn by W. J. Moore, after I. M. Wilder,

Anat. Rec, 191 9.) /

traction of the ventricles and in this case the thick-walled left
ventricle contracts with more force than the right. Contraction
is termed systole. Relaxation is termed diastole. Besides systole
and diastole there is a short passive period in which there is neither
contraction or relaxation.

Pulse. — In men the average frequency of the pulse is from 60 to
70, while in women it varies from 65 to 80 beats per minute. There

454 MAMMALIA— PHYSIOLOGY

is a quite definite correlation between longevity and the rapidity
of the pulse. (See tables, pages 496 and 498.)

Portal Circulation. — The blood which comes to the spleen,
stomach and intestines passes first through the capillaries of these
organs and then by their veins into one, the portal vein, which goes
to the liver and there breaks up into capillaries, then passes from
the liver into the post cava. The wastes are conveyed from the
liver by way of the bile duct which leads into the digestive tube.
But bile acids and salts are extremely important.

The Comparative Anatomy of the Portal Systems. — In a portal
system the blood is collected in capillaries, passes through a vein to
an organ of purification, thence by capillaries to another vein that
brings the purified blood into the heart.

(i) The hepatic portal system consists of the union of veins from
the stomach, intestine, spleen and pancreas, which passes into
the liver as the hepatic portal vein, then breaks up into capillaries,
its blood mingling with the blood brought into the liver by the
hepatic artery. Capillaries in the liver unite to form the hepatic
veins which send the purified blood into the sinus venosus. The
hepatic portal system persists throughout the vertebrates.

(2) The rey^al portal system arises in the Elasmobranchii and
almost completely disappears in the Aves.

Elasmobranchii. The caudal divides into right and left portal veins which pass to the
kidneys. The course thence is to the cardinal veins.

Teleostii. The caudal divides into two branches, of which the right continues

into the corresponding cardinal and the left breaks up in the kid-
ney.

Amphibia. Salamander.

The caudal divides into two renal portal veins. The efferent renal

veins form the postcaval.
Frog.

The femorals each divide into a dorsal and a ventral branch. The
ventral branch, the pelvic vein, unites with its fellow to form the
abdominal vein. The dorsal branch becomes the renal portal,
receives the sciatic and passes to the kidney.

Reptilia. The turtle has no renal portal system. In the lizard the caudal

divides into two pelvics which become the renal portals. As in
the salamanders, the efferent renal veins unite to aid in forming
the postcaval.

MAMMALIA— PHYSIOLOGY 455

Aves. In the birds the renal portal system has almost completely disap-

peared. The two renal portal veins formed by the division of the
caudal send off only a few branches to the kidneys, known as the
efferent renal veins, the main vein passing through the substance
of the kidney and joining the femoral vein from the leg to form the
iliac vein. The two iliacs unite to form the postcaval.

Mammalia. There is no trace of a renal portal system in the mammalia.

Blood. Functions of the Blood. — i. Carries food-stufFs to the
tissues.

1. Carries oxygen to the tissues.

3. Medium of transmission of the internal secretion of certain
glands.

4. Removes waste products from the tissues and carries them to
the organs.

5. Aids in equalizing the temperature and water content of the
body.

Amount of Blood in Per Cent in Different Parts of the Body

Spleen 0.23 per ce

Spinal cord and Brain 1.24 pe/cent

Kidney 1.63 nfer cent

Skin 2.10 ier cent

Intestines 6.30 peTiBent

Bones 8.24 per oent

Heart, Lungs and Blood vessels 22.76 peyxent

Resting muscle 29.20 p/r cent

Liver 29.30 |(gr cent

Chemical Composition of the Blood. (Schmidt)

Water 788.71 pe/cent

Proteins and extractives 191.78 pM^xent

Fibrin (from fibrinogen) 3.93 per cJnt

Hematin (and iron) 7.70 pec/cent

Salts 7.88 per cent

1,000.00 peVsent

Blood constitutes about 7 per cent by weight of the human body,
a man having about 5 liters of blood in his body. Its specific
gravity varies from 1,050 to 1,055 ^^ children and women, and from
1,057 to 1,062 in men. The specific gravity of the corpuscles is
about 1,105, and that of the plasma, about 1,030. The specific
gravity is generally in direct proportion to the hemoglobin percentage

456 MAMMALIA— PHYSIOLOGY

and the volume of (red) corpuscles. According to Schmaltz, blood
with a specific gravity of 1,059 has 100 per cent of hemoglobin, that
with a specific gravity of 10,575 has 90 per cent hemoglobin, while
blood with a specific gravity of 1,049 ^^^^ have a hemoglobin content
of but 60 per cent.

Blood has an alkaline reaction; this is at a maximum after meals
as the acid gastric juice is then in the stomach. The alkalinity is at
a minimum after exercise because of the HCO2 formed by contrac-
tion of the muscles. Blood has a salt taste and a faint smell.
Coagulation of blood is promoted by heat and standing, and re-
tarded by cold and the salts, sodium phosphate, sodium citrate and
magnesium phosphate.

Blood consists of erythrocytes (red corpuscles), leucocytes
(white corpuscles), platelets, hematokonia or blood dust. Salt
solution swells the corpuscles and pure water will dissolve out
hematin from the red ones. Water has no action on the white
ones. We consider the red blood corpuscles as dead and the white
ones as very much alive.

"Thrombocytes, usually spindle shaped, occasionally spherical,
are found in all of the vertebrates except mammals, in which only
thromboplastids (minute, cytoplasmic platelets) are found. Both
thrombocytes and platelets are associated with the clotting of the
blood. Lymphocytes are uniformly present in all classes of verte-
brates. Monocytes or, large mononuclear leucocytes, are also
uniformly present in all vertebrates. In man the neutrophilic leu-
cocytes predominate numerically." (A. B. Dawson.)

The proportion of white to red corpuscles is as i : 300 or as
I : 500. There are many more white corpuscles shortly after meals.
The reds vary in number as one goes from sea level to the mountains.

Size of reds Number of reds

Animal in microns in i cubic mm.

Elephant 9.

Man '].i-i.^ 5,000,000

Monkey 7.0 6,355,000

Guinea Pig 7.48 5,859,000

Dog 7.2 6,750,000

Horse 5.58 7,403,000

Cat 6.2 9,900,000

Spanish Goat 4.25 19,000,000

Napu Deer 2.0

(From RoUett and Bethe in Bohm-DavidofF-Huber's Histology, W. B. Saunders Co.)

MAMMALIA— PHYSIOLOGY 457

Red corpuscles or erythrocytes consist of water, hemoglobin,
nucleoproteid, lecithin, cholesterin and salts of potassium and of
phosphoric acid. The erythrocytes of fishes, amphibia, reptiles and
birds are oval and nucleated and the leucocytes are frequently
found to be without nuclei. The erythrocytes are biconcave discs
in all mammals except the Camelidae in which they are oval^ but in
healthy animals, non-nucleated in adults as in other mammals.^
Sometimes in man after anemia or severe hemorrhage, nucleated
reds are called forth from the red bone marrow where they are
formed in adults. In the embryo, the liver and the spleen produce
nucleated reds, but in the adult the spleen devours worn out reds
and furnishes some lymphocytes. The spleen probably takes some
of the iron from worn out red blood corpuscles while the liver takes
iron and uses hemoglobin in forming bile-pigment, bilirubin. The
thymus, tonsils and other lymphoid glands supply leucocytes,
acting as foci of multiplication for the cells which originate as
myelocytes in the bone marrow.

When blood is treated with Os04 it shows colorless, round disks,
which are unstable, and also granules. The disks are " thrombo-
plastids" or blood platelets.'^ The proportion of red corpuscles to
platelets is as 80 : i or as 20 : i. They are foci where coagulation
of the blood is hastened. F. F. Lucas has photographed blood
platelets with ultra-violet light and discovered that they have
." naked, sticky surfaces " such that they are able to glue themselves
together with available blood corpuscles and facilitate rapid blood
clotting. Howell believes that platelets are more than mechanical
agents in causing coagulation of blood and lymph.

Blood Groups. — In blood transfusions, it is necessary that the
blood of the donor and the recipient be alike, and that the substance
known as a hemolysin be absent. In hemolysis, a substance is
produced which has the power of dissolving the introduced red
corpuscles. Hemolysis does not occur without agglutination
(clumping) (see page 458) and it is therefore only necessary to test

* Since two texts of recent date have published the erroneous statement that Cam-
elidae have nucleated erythrocytes, the question was referred to Dr. W. H. F. Addison
and to Dr. Noback, both of whom reported that they are oval, biconvex and non-
nucleated. A paper by Ponder, Yeager and Charipper, Haematology of the Camelidae,
Zoologica, vol. ii, no. i, Dec. 5, 1928, furnishes additional proof.

* Corson, Irwin and Phillips found (1930) that irradiated ergosterol (Vitamin D)
increased the number of thrombocytes in the blood of rats, and materially shortened
the time of coagulation. Blood calcium was increased.

458 MAMMALIA— PHYSIOLOGY

for the agglutinins, before utilizing the blood of a donor. In 1901,
Landsteiner showed that human beings may be divided into three
groups according to the interactions of their sera and blood cells.
Later his pupils, Decastello and Sturli, added a fourth group.
Blood from two persons of the same group will mix freely, but the
blood from two different groups will clump or agglutinate.

Inagglutinable; contain no agglutino-
gen.

Agglutinated by serum of groups O and
B; contain agglutinogen A.

Agglutinated by serum of groups O and

Landsteiner's Table of the Constitution of the Four Blood Groups
Group Serum Cells

O Agglutinates cells of three other groups;

contains agglutinins alpha and beta.
A Agglutinates cells of groups B and AB;

contains agglutinin.
B Agglutinates cells of groups A and AB;

contains agglutinin. A; contain agglutinogen B.

AB No agglutinative effect; contains no ag- Agglutinated by serum of groups O, A,

glutinin. and B; contain both agglutinogens A

and B.

Moss's classification of blood groups has to some extent replaced
the earlier ones of Landsteiner and Janksy. Hooker and Boyd
of the Evans Memorial Hospital, Boston, have studied (1929) the
chances of establishing a child's paternity by blood grouping tests.
A child's blood may belong to the same or a different blood group
from its mother. Some investigators believe that the characteristics
follow the Mendelian Law and may be inherited from the grand-
parents.^

Lyinph. — Except for those red corpuscles accidentally present
in it, lymph may be considered to be blood minus the erythrocytes.
Lymph bathes every cell and tissue of the body, and mediates inter-
changes between the tissues and circulating blood. It has several
important functions: (i) The conveyance of food and of oxygen
inward from the capillaries to the cells and the external transporta-
tion of the tissues' waste. (2) The absorption of fat from the diges-
tive tube. (3) The lubrication of great serous surfaces. (4) The
upkeep of fluids in the brain and spinal cord. (5) The maintenance

^ Consult K. Landsteiner, The Human Blood Groups, pp. 892-908; R. Ottenberg
and D. Beres, The Heredity of the Blood Groups, pp. 909-920; in Jordan, E. O., and
Falk, I. S., The Newer Knowledge of Bacteriology and Immunology, U. of C. Press,
1928; and the summary by L. H. Snyder, Arch. Path, and Lab. Meth., vol. 4, pp. 215-
257, 1927.

MAMMALIA— PHYSIOLOGY

459

S -Thoracic c/uct

of the optimum composition of the blood, even at the expense of the
constancy of lymph.

Lymph consists of nutritive material absorbed from the walls of
the alimentary canal and colorless food materials in the blood not
yet utilized. After meals the color of lymph becomes whitish from
the admixture of chyle^ and
many fat droplets are pre- ^'

sent. Lymph coagulates
when drawn, since the fibrin
factors are present; but the
process is less prompt and
the clot is less firm than in
the case of blood. Lymph
contains three proteins,
fibrin, serum-globulin, and
serum-albumen. It con-
tains, in common with
plasma, cholesterin, sugar
and inorganic salts. The
proteins are less abundant
than in plasma. The
amount of urea is greater
than in plasma.

Lymphatics. — From the
alimentary canal, materials
pass in part directly into
the blood vessels surround-
ing the canal, and in part

into vessels called lacteah

1 • 1 r J • ^u '^^ Fig. 247. Diagram of paths of absorbed

which are found m the mtes- ^ , 1 ^' , ° ■ ^ ,t^ n

, .... _ , food from the digestive tract, (trom Lonn

tmal villi. Lacteals trans- ^^^ Budington. Courtesy of Silver, Burdett
port chyle to the receptac- and Co., New York.)
ulum chyli of the thoracic

duct. The lymphatics and the lacteals form a simple, branched
vascular tree which opens into the jugular veins at their bases by two
trunks, the left-thoracic duct and right-lymphatic duct. Through-
out the course of the lymphatic vessels are many lymphatic glands
which are the foci of multiplication of white blood corpuscles and
act as strainers for poisons. (Figure 246.)

Flow of Lymph. — No organ corresponding to the heart keeps the

( V h

^-

%

Y

it/

■••to

ft

\

*

H

X

B

\ ■

/

fln

p<..— .

-] — From
r:~Lactea

Sti

ornoc/i

Portal vein ^
From spleen'

%

'Is-

or

A

M-

; /ymph

^esse/s

460 MAMMALIA— PHYSIOLOGY

lymph current in motion. The main cause for its direction from the
extra-vascular spaces toward the veins in the neck is the degree of
pressure to which it is subjected in those spaces as compared with
the small pressure near the ends of the great ducts. Lymph flow
somewhat resembles that of venous blood, but is less regular and
more sluggish, though not so slow as might be supposed.

S-pleen. — While the mammalian spleen may be operatively re-
moved, it serves several important functions: (i) During embryonic
life and even after birth, in cases of anemia, the spleen forms red
corpuscles. (2) It contains large quantities of organic iron and
probably aids in the preparation of hemoglobin. (3) It destroys
old worn-out red corpuscles and takes up pigment and other wastes
from the blood. (4) It increases in size during digestion and after
the fifth hour slowly decreases to normal size. It is excessively
vascular during digestion.

Respiratory System. — In the cat the respiratory system is not
greatly different from that of man. Air inhaled at the anterior
nares goes through the nasal passages and out from the posterior
nares into the naso-pharynx, Lucas ^ finds that in the monkey the
cilia of the septum, the middle concha {turbinate) , and the middle
meatus sweep the mucus downward toward the floor and hence
backward into the naso-pharynx (not upward as senior authors have
claimed). The trachea of the cat consists of forty-five cartilages
(16-20 in man) which are held in place by fibrous membrane which
embeds them. In the cat the trachea is three-fourths of an inch in
diameter and four and one-half inches in length. The lungs consist
of three lobes on each side with a fourth lobe on the right side which
is divided into two parts, and lies a little to the right of the middle of
the body. The cartilaginous rings extend two-thirds of the way
around the trachea, the third not supported by the rings resting
upon the esophagus. The lungs are supported in the chest by paired
bronchi and the pulmonary and bronchial arteries, veins and
lymphatics. The bj-onchi also have incomplete irregularly arranged
cartilaginous rings. Each lung is covered by a delicate serous
membrane, the pleura^ which is reflected over the inner surface of
the thorax. The lung consists of many lobules of air-cells with
extremely thin walls and is richly supplied with minute capillaries
as well as many veins and arteries. In the trachea and the bronchi,

* Lucas, A. M., in Chapter 1 1 of Special Cytology, 2d edition, edited by E. V.
Cowdry, 1931.

MAMMALIA— PHYSIOLOGY

461

the ciliary movement is upward towards the throat. Inhalation of
chloroform stops ciliary activity, while ether does not (Lucas).
Hach found (1925) that morphine slowed the rate of movement
of pollen injected into the trachea of dogs, but that caffein increased
the speed of its transportation.

Respiration. — During the first year of life, the average rate of
respiration in the human infant is about forty-four per minute.
It gradually reduces to a rate of about fourteen or fifteen per minute
in the adult.

Table of Respiration Rates of Various Animals. (Bert ^)

Hippopotamus i per minute

Lion

Horse

Pig

Ox

Dog

Sheep and goat i

Cat 24

Pigeon 30

Eel 50

Rabbit 55

Sparrow 90

Rat (asleep) 100

I

10

10

to

12

10

(<

!<;

15

<(

18

I^

<(

20

18

((

20

«
«
«

«

How Long Can Aquatic Mammals Submerge'^ — It is well known
that by practice it is possible for man to remain submerged for over
two minutes (see page 157). Parker, in some recent observations,
has shown that the Florida manatee can remain submerged sixteen
minutes. The whale, reported to submerge for an hour, has been
found by Parker to remain twenty minutes under water.

Voices of Mammals. — In man, the dog, the sheep, and the horse,
the voice is produced by expiratory blasts of the lungs producing
vibrations of the vocal cords. The pitch of sound and tones depends
on the tension of the vocal cords, a low-pitched tone being produced
by relaxed cords. In the cat, the pig and cattle, the voice is an
inspiratory act. The whale, the dolphin, and the giraffe are mute.

The Excretory System. — The urinary system of the mammal
consists of paired kidneys where solid products of decay that cannot
be eliminated by the lungs are excreted in the urine which passes
from the kidneys by way of the ureters to the ventrally situated

^ Dearborn, G. V. N. 1908. Human Physiology. Lea and Febiger, Philadelphia.

462

MAMMALIA— PHYSIOLOGY

urinary bladder. From thence it is transported by means of the
urethra to the exterior. The kidneys expel water, urea and a little
CO2. The average amount of urine secreted in man per day is
fifty ounces. The lungs exhale CO2 and water with a trace of urea,
while the skin excretes as the lungs do and also functions in place of
the kidneys when they are diseased (see Perspiration, page 428).
The liver, by means of its hepatic portal system (see page 454),
separates out the impurities from the blood and passes them into
the duodenum. Intestinal excretion plays an important role in the
economy of the animal.

Fig. 248. Graafian follicle and ovum of the cat, within the ovary. (Photograph
through the courtesy of Dr. B. F. Kingsbury.)

Reproductive System. — While in the lower vertebrates there is
an extremely close relationship between the urinary and the repro-
ductive system, evidenced in the frog, for instance, by the passage
of sperms through the kidney and out through the common Leydig's
duct, we find that in the mammal, at birth, such connection largely
disappears.

Female. — In the cat there are two small oval ovaries^ which
produce Graafian follicles and send the ova therein contained down
the elongated Fallopian tubes, the lower portions of which, as horns

MAMMALIA— PHYSIOLOGY

463

Protoplaamic
eiop

(cornua) of the bicornuate uterus^ retain the embryos until they
have matured. The body of the uterus in the cat does not receive
the implanted ovum. Subsequent to the extrusion of the ovum, the
follicular epithelium of a Graafian follicle degenerates, collecting in a
mass of cells of a yellowish color called the corpus luteum (see p. 444).
In higher mammals (cow, man) the Fallopian tubes or oviducts
function merely to convey sperm and to carry the eggs to the body
of the uterus. Parker finds that, in reptiles and birds, a proovarian
tract of cilia conducts the sperms upward, and an extensive ab-
ovarian tract propels the ova downward. Parker has recently
(1931) shown that in the rabbit muscular contractions and ciliary
activity together move the sperms upward and the ova downward.
The eflPective stroke of all cilia is toward the uterus. The Fallopian
tubes and the uterus are suspended by the broad ligament attached
to the dorsal abdominal wall.

The delicate round ligament \ ^Acmome

also aids in the suspension of Head ■! M Nucleus

these structures. The body of
the uterus continues posteriorly
to form the vagina. From the
urinary bladder leads the female tliddlePiSce
urethra which ends in the cat at
the vestibule, about one-half inch
from the external opening of
the vagina, the vulva. On the
ventral surface, just posterior to
the opening of the urethra, ap-
pears the clitoris, which is the ji^uvPiece •
homologue of the penis of the
male. Bartholin's glands are
situated lateral to the vestibule
with ducts opening into it. The
vagina, uterus, and the Fallopian
tubes are all lined with mucous
membrane richly supplied with
glands. EndPiece

Male. — The paired testes of

the cat consist of numerous min- ^^^ ^^^^ Diagram of animal sperm
Ute coiled tubules, the seminifer- as in mammals. (After Wilson, The Cell.
OUS tubules, which in each testis Courtesy of The Macmillan Company.)

Head

Neck

Connecting or

— Envelope

; Proxinval CentnoU(c9

, '"dSmi CentHole i^

^ial rvlament

Tall Envelope

464

MAMMALIA— PHYSIOLOGY

unite into a few beneath the elongated epididymis which continues to
form the vas deferens. These canals transport the spermatozoa to
the urethra. By the activity of the ciliated epithelial cells lining the
efferent ducts, the then immotile spermatozoa are slowly passed
toward the epididymis. The penis, by means of which sperms are
transferred, receives the urethra. The prostate glands surround
the urethra dorsolaterally a short distance from the urinary bladder.
They secrete a fluid which serves as a medium for the spermatozoa.
The spermatozoan has a long flagellum, and its activity is affected

by changes (CO2, acidity) in
the seminal fluid, just as the
beat of the cilia may also be
affected. Cowper's glands are
situated posterior to the pro-
state glands and secrete a vis-
cid fluid which passes into the
urethra by a duct from each
gland.

Propagation Rate in Mam-
mals.— In the lower verte-
brates, such as the cod fish, it
is stated that of six million eggs
spawned, less than a third are
fertilized. In birds and mam-
mals, a limited number of eggs
are matured at one time.
Sometimes a single ovum de-
velops at the expense of others.
Marshall quotes Aral to the effect that the ovary of the rat at birth
contains 35,100 ova, which are reduced by degeneration to 11,000
after 23 days, and to 6,000 by the 63d day. Smith and Engle, by
the implantation of anterior hypophyseal substance in infantile
female mice, succeeded in inducing the ripening of ova such that
one of the animals produced twenty young. (See Hypophysis,
p. 448.)

The Nervous System. — There are two main groups of activities
in the vertebrate organism which have determined the general plan
of organization of the nervous system.

Reactions toward the external world consist In the finding and
capturing of food, fighting with other animals, preparing nests or

Fig.

150. Human embryo at six weeks.
(Photo by Newton Miller.)

MAMMALIA— PHYSIOLOGY

465

homes for protection against the physical elements, and many minor
reactions such as changes in heat, light or moisture.

Period of Gestation '

Mammalia

Gestation Period

Condition of Young at Birth

Monotremata

Ant eater

Hatched from eggs. Very
immature.

Marsupialia

Kangaroo

Size of small rat and very help
less. Sheltered in pouch.

Rodentia

Rat

21 days

Eyes closed, small, helpless.

Mouse

21 days

Rabbit

28-32 days

Guinea pig

62-80 days

Development far advanced.
Eats corn in 2 or 3 days.

Ungulata

Blackfaced sheep

21 or 22 weeks

Well advanced but suckling
some time.

Cattle

9 months

Pig

16 weeks

Mare

II months

Elephant

20 months

W'ell advanced.

Camel

45 weeks

Cetacea

Whale

10 months

Porpoise

10 months plus

Young able to follow mother
about.

Carnivora

Cape hunting dog

{Lycaon)

80 days

Lustier than dog.

Wild dog {S. America)

2 mos. (59-63 days)

Young helpless.

Domestic cat

56-63 days

Wild cat

68 days

Lioness

15 to 16 weeks

Tigress

22 weeks

Puma

15 weeks

Brown bear

7 months

Grizzly

8 months

Ferret

40 days

Polecat

40 days

Walrus

I year

Lactation two years.

Primates

Monkeys

7 months

Man

280 days

* Compiled from F. H. A. Marshall, 1922, Physiology of Reproduction.

466

MAMMALIA— PHYSIOLOGY

The internal activities include all the processes related to metab-
olism, the distribution of nutritive material to various parts of the
organism, and the various processes connected with the formation
of the reproductive elements and the nutrition of the embryo.

Sensory Nerves. — The nerve fibers and central mechanisms which
have to do with the stimuli affecting the welfare of the animal in
its surroundings are the somatic afferent or somatic sensory division
of the Nervous System.

Lombdoidal rid<je —
Interpariefal

Zygomatic process
of frontal

Supraorbital ridgs —

Lachrymal
fnfra-orbilol foramen

Nosal capsule
Maxillary

Suprooccipital
Sa(jittal ridge

— -V ¥\ Porie tal

Temporal

Zygomatic process
of temporal bone

— Jj Temporal fossa

^Frontal process
of malor

—Zygomatic arch

ti/lalar

Supraorbital ridge

— Orbit

__Zygomotic process
of maxillary bone

■Lacfirymal foramen
Nasal
— Foramina incisa

— i- — -yf-l- Anterior nores

— Infermoxillory

Fig. 251. Dorsal view of the skull of the cat. (Drawn by W. J. Moore.)

All the nervous structures concerned with impulses arising in
the viscera, in the taste organs, and in the olfactory organ are
closely related and constitute the visceral afferent or viscer0->sensory
division of the nervous system.

Motor Nerves. — All the usual movements of locomotion, of
offense and defense are directed ordinarily in response to stimuli
from without. Somatic movements are also performed in response
to gustatory and olfactory stimuli and have for their object the
capturing of food. In general, while somatic movements may be
called forth by visceral stimuli, they are more typically called forth
by somatic stimuli, and are more precise when they are directed
in response to them.

MAMMALIA— PHYSIOLOGY 467

The nerve centers and peripheral nerves which direct somatic
movements constitute a distinct portion of the Nervous System
which we may call the somatic {efferent) motor division.

The visceral activities consist of contractions of the visceral
muscles, secretory processes and vaso-motor regulation. All these
contribute directly or indirectly to the processes of nutrition in
the widest sense or of reproduction. Just how far they may be
called forth by somatic stimuli is not known. We know that the
sight of food may cause salivary secretion. Respiration is called
forth by rise in temperature within the body. The nerve centers
and fibers which control the activities of the viscera make up the
visceral efferent or viscero-motor division of the Nervous System.

To summarize, in any vertebrate animal there are four kinds of
nervous activity: (i) Reception of somatic stimuli. (2) Direction
of somatic movements. (3) Reception of visceral stimuli. (4)
Direction of visceral movements and activities.

The mammalian brain exhibits marked superiority over that of
the lower vertebrates in the development of large richly convoluted
cerebral hemispheres and a cerebellum not surpassed in any form
except the bird. The olfactory lobes situated ventrally at the ante-
rior portion of the cerebral hemispheres are highly developed in
many of the lower mammals. In common with the reptiles and
birds, the mammals have 12 pairs of cerebral nerves. There are j/
pairs of spinal nerves in man, and 38 pairs in the cat.

Both the brain and the spinal cord consist of gray and white
nervous matter but in the brain the gray is on the outside and the
white is within while in the spinal cord the gray is on the inside and
the white is external. White matter is chiefly composed of nerve
fibers while gray matter is much more vascular and composed of
nerve cells which give rise to nerve fibers. Nerve fibers are non-
medullated — {a) Naked axis cylinder, {b) Axis cylinder with primitive
sheath, and medullated — {c) Primitive sheath absent, {d) Primitive
sheath present. Medullated fibers are present in greater quantity
than non-medullated in the cerebro-spinal system. The mass of
white substance of the brain, spinal cord, and optic nerve has
medullated fibers without the primitive sheath. Both brain and the
spinal cord are covered by three membranes, the outer dura mater
with a thin delicate membrane, the arachnoid^ which serves as a
sheath for the nerves and is separated from the dura mater by a
narrow sub-dural space. A vascular membrane, the pia mater^ is

468

MAMMALIA— PHYSIOLOGY

si

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0

^

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•5

■?

t> ^

to

8

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^1'

o

0
'0

0

"S

V\

a

C

O

SS ^

^^

c^

o
o

MAMMALIA— PHYSIOLOGY 469

loosely connected with the arachnoid by strands of connective tissue
forming a spongy network but there is considerable space between
the two called the sub-arachnoid space. This space contains a fluid
called the cerebro-spinal fluid which differs from ordinary lymph (i)
in its small per cent of proteins, (2) in the absence of cells and (3)
in the absence of a fibrin ferment.

Cerebro-spinal fluid is colorless and alkaline, having a specific
gravity of between 1,006 and 1,008. It consists mostly of water.
The solids include a trace of protein, chiefly globulin; if the mem-
branes of the brain or cord are inflamed, there is much more protein
present. A small amount of carbohydrate as glucose and the salts
found in blood plasma occurs, with occasionally a few leucocytes and
a large quantity of CO2. It contains no antitoxins, opsonins, nor
alexins which are present in blood plasma and in tissue fluid.

Cerebrwn. — Much of the cerebral cortex is occupied by large tri-
angular cells called pyramidal cells, the largest of which is one-six
hundredth of an inch. These cells are agents in the psychic activity
of the cortex.^ Cajal called them psychic cells. The fibers of white
matter of the cerebral hemisphere consist of projection fibers and
association fibers. The projection fibers are those which project the
impulses of the outside world upon the sensorium, or the reverse.
These are cortico-afferent^ leading from lower levels to the cortex, or
cortico-efferent, leading from the cortex to lower levels. The associa-
tion fibers which correlate cortical areas are of two types, the arcuate
which correlate areas of the same hemisphere, and the commissural
which correlate areas of the opposite hemisphere. The most impor-
tant commissures in the mammalian brain are the corpus callosiim
and the anterior^ middle and posterior commissures. The fibers of
the cortex myelinate late, none receiving the medullary sheath in the
human brain until the ninth fetal month. (See page 479.)

Cerebellum. — The cerebellum, important in coordination, con-
sists of an outer clear gray molecularlayer with an inner reddish gray
granular layer. At the junction of these two layers are the large
flask-shaped cells called the Purkinje cells. It is by contact and not
by continuity of structure that nervous impulses are transmitted.
The system of the cerebellum shows not only this but shows that
different parts of the same cell may be supplied with terminal fibers
from quite different sources.

8 "Learning without thought is labor lost; thought without learning is perilous."
Confucius.

470

MAMMALIA— PHYSIOLOGY

Table of Cerebral Nerves and Their Components in Mammals

No.

I.

II.

III.

IV.

VI.

Name

Olfactory
Optic

Oculo-
motor

Patheticus
or Tro-
chlearis

Trigeminal

Abducens

Components

Special viscero-
sensory

Special somatic
sensory

Special somatic
motor

General viscero-
motor

General somatic
sensory

Special somatic
motor

General somatic
sensory

Special viscero-
motor

General somatic
sensory A. Ex-
teroceptive

Cells of Origin

General somatic
sensory B.
Proprio-
ceptive

Special somatic
motor

General somatic
sensory

Nasal mucous

membrane
Ganglion cells of

the retina

III. Nuc. at lev-
el of sup. coll.

Nuc. of Edinger-
Westphal

IV. Nuc. at lev-
el inf. coll.

Motor V nuc.

Semilunar gan-
glion. (Gas-
serian g.)
Periph. br. to
skin, mucous
m. of head;
central br, to
brain

Mesencephalic
V

VI. Nuc. dors,
pons.

Distribution

Mitral cells of olfactory bulb.

External geniculate, pulvinar
of thalamus; superior collicu-
lus.

Superior, inferior, internal rec-
ti and inferior oblique mus-
cles; levator palpebra supe-
rior.

Preganglionic fibers to ciliary
ganglion, postganglionic fi-
bers to intrinsic muscles of
eye.

Mixed with motor fibers of
four muscles.

Superior oblique muscle.

Mixed with motor fibers to
superior oblique muscles.

Mandibularis nerve to tempo-
ral, masseter, external and
internal pterygoid, tensor
palati, tensor tympani, ante-
rior belly of digastric and
mylo-hyoid muscles.

Ophthalmic, maxillary and
mandibular nerves.

Mixed with motor fibers to
masticatory muscles.

External rectus muscle.

Mixed with motor fibers to ex-
ternal rectus muscle.

MAMMALIA— PHYSIOLOGY 47 1

Table of Cerebral Nerves and Their Components in Mammals — Continued

No.

VII.

VIII.

IX.

Name

Facial

X.

Acoustic

Glosso-
pharyn-
geal

Vagus or
Pneumo-
gastric

Components

General viscero-
motor

Special viscero-
motor

General viscero
sensory

Special viscero-
sensory

Special somatic
sensory

General viscero
motor

Special viscero-
motor

General viscero-
sensory

Special viscero-
sensory
Somatic sensory

General viscero-
motor

Special viscero-
motor

General viscero-
sensory

Special viscero-
sensory

General somatic
sensory

Cells of Origin

Salivat. sup.
nuc.

Motor VII nuc.

Geniculate gan-
glion

General gan-
glion

A. Vestibular
ganglion. B.
Spiral gan-
glion of cochlea

Motor IX root.
Nuc. saliva-
tory inf.

Nuc. ambig.

Ganglion pe-
trosal IX

Ganglion
petrosal

Ganglion supe-
rior IX

Dorsal motor
nuc. of X

Nuc. ambiguus

Ganglion
nodosum

Ganglion
nodosum

Ganglion
jugulare X.

Distribution

Preganglionic fibers in chorda
tympani; postganglionic fi-
bers from sub-maxillary gan-
glion to submax. and sub-
lingual glands.

Stapedius, posterior belly of
digastric, stylohyoid muscle.

Sup. petrosal, chorda tympani,
tympanic plexus.

Chorda tympani and lingual
nerve to taste buds on ante-
rior two-thirds of tongue.

Semicircular canals, sacculus,
utriculus.

Organ of Corti of Cochlea.

Preganglionic fibers in tymp.
and sup. petrosal nerve;
postganglionic from otic gan-
glion to parotid gland.

Stylopharyngeus muscles.
(Unstriped pharyng.)

Sensory fibers to pharynx,
posterior one-third of tongue.
(Lingualis IX.)

Tastebuds of post, one-third of
tongue.

Tactile corpuscles of posterior
one-third of tongue.

Preganglionic sympathetic fi-
bers to pharynx, stomach,
heart, lungs, trachea.

Superior and inferior laryngeal
and pharyngeal nerves to
striated muscles of pharynx
and larynx.

Nerves from viscera, larynx,
pharynx, lungs, heart, and
sympathetic connections.

Internal laryngeal nerve.

Ramus auricularis vagi. (Be-
hind ear.)

472

MAMMALIA— PHYSIOLOGY

Table of Cerebral Nerves and Their Components in Mammals — Continued

No.

Name

Components

Cells of Origin

Distribution

XL

Spinal

General viscero-

Dorsal motor

Preganglionic fibers distrib-

accessory

motor

nuc. of X.

uted with the vagus.

Special viscero-

Nuc. ambiguus

Striated muscles of pharynx

motor.

and larynx and rami to tra-
pezius and sterno-cleido-mas-
toid muscles.

XII.

Hypo-

Special somatic

XII. nuc.

Hypoglossiis nerve to muscles

glossal

motor.

of tongue.

In the I, II, III, IV, VI, and VIII nerves the organs of special sense are supplied,
while the V, VII, IX, X, and XI cerebral nerves have visceral functions predominating.

Consult Johnston's Comparative Neurology and article by C. J. Herrick in Refer-
ence Handbook of Medical Sciences, entitled the Cranial Nerves.

The bodies of Purkinje cells are surrounded by the basket ter-
minals of the stellate cells of the molecular layers, while their proto-
plasmic processes are in contact with the efferent fibers that arise
from more distant portions of the nervous system.

Medulla Oblongata. — The medulla oblongata controlling heart
beat and respiration, the enlarged anterior portion of the spinal cord,
sends off the cerebral nerves from the fifth to the twelfth inclusive.
It receives columns of fibers originating in the spinal cord and may
be considered a great switch station for impulses passing up and
down the cord.

Spinal Cord. — In all vertebrates having well-developed limbs
the two regions of the spinal cord with which the nerves of the limbs
are connected are somewhat thicker than the rest of the cord and are
known as the thoracic and lumbar enlargements. Each of the
spinal nerves has a ventral anterior root and a dorsal posterior root
with spinal ganglia, containing nerve cells and fibers which are
usually afferent., conveying impulses from the parts and organs of
the body to the central nervous system. The vetttral root is not
ganglionated and its fibers are efferent, conveying impulses from the
neuron outward. The cranial nerves are twelve in number on each
side in reptiles, birds and mammals. Only the trigeminal or fifth
present a double-rooted arrangement similar to a spinal nerve.
Several however have ganglia comparable to those of the dorsal
roots of the spinal nerves. Besides the fifth or trigeminal these

MAMMALIA— PHYSIOLOGY

473

include the seventh (facial), eighth (auditory), the ninth (glosso-
pharyngeal) and the tenth (pneumogastric).

Origin and Structure of the Neuron. — A neuron consists of a cell
body with all of its processes. The entire nervous system is com-
posed of cells with one or more processes. These cells develop early
in embryonic life from certain ectodermal cells (neuroblasts) of the
neural canal (which is formed by a dorsal invagination of the ecto-
derm). The neuroblasts develop secondary processes, many in the
neural canal, others after wandering from it, and by this process
of budding become nerve cells. The primitive processes continue
to extend until they reach the periphery of the body, are invested
with medullary sheaths supplied by connective tissue of the region
through which they pass, and become nerve fibers. Nerve fiber and
nerve cell are therefore parts of the same histological unit.

The processes are of two kinds: i. («) unbranched; {}?) uniform
in diameter with lateral offshoots called collateral branches. These
are generally the central part of a nerve fiber and are called neurites
or axones. i. Processes which branch soon after leaving cell body
and break up into smaller branches called dendrites. Thus the
neuron consists of a cell body containing a conspicuous nucleus,
nucleolus and cytoplasmic granules, protoplasmic processes called
dendrites, an axis cylinder process which passes into a nerve fiber,
and a final termination in the form of a branching tuft. Golgi's
idea that protoplasmic processes or dendrites subserve nutrition of
the cell is without foundation. Many circumstances show that they
transmit impulses.

The Sympathetic Nervous System consists of a pair of elongated
ganglionated cords extending from the base of the skull to the lumbo-
sacral region, connecting on the one hand by a series of branches to
the spinal nervous system, and on the other hand giving off an irregu-
lar series of branches to the viscera. At its cephalic end, each sym-
pathetic cord is continued in a plexiform manner into the cranial
relationships with certain cranial nerves. Caudally, the two cords
are joined by fine filaments and connected by the coccygeal ganglion.

The sympathetic system rearranges and distributes fibers, derived
from the cerebro-spinal system, to the viscera and vessels of the
splanchnic area. It transmits afferent fibers from the viscera to the
cerebro-spinal system, and sends fibers to the vessels, involuntary
muscles and glands in the course of the somatic divisions of the

474 MAMMALIA— PHYSIOLOGY

spinal nerves. Its fibers are called white rami communicantes
(medullated) and gray rami communicantes (non-medullated).
Sense Organs. —

Kulpe's Classification of Sensations by Organs i"
1. Vision,
1. Audition.

3. Cutaneous.

Cold
Warmth
Pressure
Pain

4. Olfactory.

5. Static sense.

Ampullar (dizziness)
Vestibular

6. Gustatory. (See page 477.)

7. Kinaesthetic.

Muscular

Tendinous

Articular

8. Organic.

Hunger
Thirst
Nausea
Suffocation

9. Reproductive.

Vision depends on the proper function of the complicated eye.
Sensation passes from the layer oirods and cones of the retina through
its nuclear and molecular layers to the ganglion cells from which
nerve fibers transmit the impulse to the optic tracts leading to the
brain. (See p. 468.)

Visual sensations include hue or quality, brightness and satura-
tion. The stimuli are the ethereal vibrations ranging between
400,000 and 800,000 billions per second. Color is stimulated
by the wave length while the height of the wave gives the bright-
ness and the form of the wave determines the degree of saturation.
■It is said that in certain tapestries in Milan there are 1,800 colors
while in some Italian mosaics there are 30,000 colors. ^^

Color Blindness. — Some people are unable to distinguish all of

1° Consult Murchlson, C. 1929. The Foundations of Experimental Psychology.
Clark Univ. Press.

11 Consult Herrick, C. J. 1931. Introduction to Neurology. W. B, Saunders.

MAMMALIA— PHYSIOLOGY

475

on.

the 1 60 color tones. In total color blindness one cannot distinguish
between any other colors than gray. Partial color blindness is the
inability to distinguish between a certain group of colors.

Audition. — The mammalian ear receives sound waves and trans-
mits them by the tympanum to the ossicles and from the ossicles
by way of the vestibule
they pass to the liquid
in the cochlea. The
movement is continued
to the basilar membrane
where vibrations of the
fibers in unison with the
tone affect definite hair
cells and the sensation is ^
transmitted to the brain
by way of the eighth
nerve. (See p. 468.)

The Organ of Corti

in the cochlea of the ear

is the receptor involved

in hearing. Numerous

theories of the activa- , ,

c -i -^ ^ Fig. au. The vertebrate eye. a, aqueous hu-

tion of the constituents ^-^ . . „ i u -^ ; ■,,;..

. ^ mour; c, conjunctiva; C, cornea; ch, choroid; /, ins;

of this organ by the Vl- ^^ j^^^. ^_„^ ^p^j^, ^erve; P, pigment layer; p, pupil;
brations of fibers imbed- r^ retina; r, layer of rods; s, sclerotic; y, vitreous body.
ded in the basilar rnem- (From Kerr. Courtesy of Macmillan and Co., Ltd.)
brane have been ad-
vanced. The human ear is sensitive to vibrations with a frequency
of from thirty to thirty thousand per second.

Hearing in Aquatic Mammals. — The whale., like the seal and the
porpoise, lacks external ears. It has blow-holes on the top of its
head, which are closed by means of elastic cartilage valves. The
cachalot has an external opening, about i inch long in the full-grown
whale. The external auditory tube is closed by bony growth,
protecting the ear drum from the pressure encountered at great
depths. It is claimed by Kellogg that the whale-bone whales now
actually hear through their noses, and that the ear drum is nori-
functional. The bulla, a structure coiled like a conch shell, is said
to receive the sound waves. Whales are able to detect sounds very
readily.

V.

476

MAMMALIA— PHYSIOLOGY

Cutaneous Sensibility. — Besides light touch we have sense organs
for deep pressure sense and pain. Adjacent to each other there are
end organs for sensibility to cold and heat. It is said that there
are over 250,000 cold spots and but 30,000 warm spots. Sometimes
a paradoxical sensation of cold may be aroused by a hot stimulus.
The cheek is relatively insensitive to pain.

^vtox- <y/Qnds

Cochlea^ \

Cowi'ty of ^Ac-jy v<

ty/nponum or drum — r^^J '""

- >

Auc/ifory
ccfno/
ancf
tvo//S

—-Sty/oid pr-Qcess

- • Internal corofid artery

/Auditory tube

Fig. 254. Diagram of the human ear. (After Morris. Courtesy of P. Blakiston's

Son & Co.)

Olfactory Sense. — Olfactory sensations are served by the nasal
mucous me?nbra7te which has end-organs leading to the olfactory
nerves. The end organs for the sense of smell are limited to the
upper part of the nasal cavity. The epithelial layer consists of
columnar supporting cells and several layers of nerve cells which
are elongated in shape and nucleated. The prolongation of the
Q^W peripherally between the columnar cells terminates at the surface
in from six to eight hair-like processes while the central prolongation
continues as a non-medullated nerve fiber to the olfactory lobe where
it arborizes in relation to the dendrites of certain " mitral cells "
whose axones transmit impulses by the olfactory fibers.

Static Sense. — The organs of equilibration are the semicircular
canals of the internal ear.

Gustatory Sense. — The organs of taste consist of sensory cells
found in the taste buds of certain papillae on the tongue. (See page

MAMMALIA— PHYSIOLOGY

477

429.) There are four types of taste: Sweet, sour, salt and bitter.

In eating one receives sensations from taste, smell, cutaneous sense

and temperature sense. The child prefers sweets while sour and

bitter are unpleasant. Children have more taste organs than the

adults since some of the taste buds atrophy as age advances. One

section of the tongue is wholly insensitive to taste. The anterior

portion of the tongue is sensitive to sweet substances, the lateral

portions are sensitive to sour and salt, while

the posterior portion is extremely sensitive to

bitter substances.

Kinaesthetic Sense. — Certain kin aesthetic

sense organs are contained in the skeletal

muscles, tendons and joints and transmit to

the brain knowledge of positions of parts of

the body.

Organic Sensations. — Many subconscious

sensations concerned with visceral activities

are carried to the brain by the aid of organs

connected with the digestive, respiratory and

circulatory systems. Unusual stimuli may

produce thirst, hunger, nausea or suffocation.
Weight of the Brain. — The brain of the

average adult human female weighs 44.5

ounces and that of the male 49.75 ounces.
Cases have been recorded in which the brain

attained a weight of 74.8 ounces, one case

being that of an idiot. The weight of the

brain of the gorilla is 15 ounces. In the

healthy body the relation of the weight of tesy of Henry Holt & Co.)

the human brain to that of the body is 1-41.

Transmission of an Impulse. — From a sense organ in the skin an
impulse passes to the sensory fiber of a spinal nerve, in at the dorsal
(posterior) root to the dorsal horn of the cord and to a spinal sensory
cell. Thence it goes up the dorsal column to the sensory cell of the
optic thalamus. From the optic thalamus it passes to the sensory
cell of the cortex in the localized area indicated by its original source.
Then the impulse to act, beginning at the motor cell of the cortex,
passes across to the motor cell of the corpus striatum (see Figure
256), thence down the anterior ventral colujnn of the spinal cord to
a spinal motor cell in the ventral horn, out at the ventral root of the

Fig. 255. Upper sur-
face of the tongue. /,
circumvallate papillae; 2,
fungiform papillae. (After
Brubaker, from Kellogg,
Animals and Man. Cour-

478

MAMMALIA— PHYSIOLOGY

Afferent or sensory neurone
Gray mafrer /

Spinal cord j ' /n

~\—5k/n

Receptor

White matter

\ Efferent or motor neurone

\
Ad JUS tor neurone

Fig. 256^^. Reflex arc. (Drawn by W. J. Moore.)

-Ef fee for

Olfactory — -^

-Cerebro - cortex

Coudotum

Corpora striata

— Lenticula

— Tfiaiamus

Corpora quodrigennina
nucleus

— -Substantia nigra

'erebei/o - cortex

Olive

Fig. 2565. Chief ganglionic categories. (After Spitzka.)

MAMMALIA— PHYSIOLOGY 479

cord to a spinal nerve and thence to the proper muscle. As many
of the fibers cross to the opposite side, we find that a lesion of the
brain on the right side will cause paralysis on the left side of the body.

Reflex Action. — In a simple reflex, we never find as few as two
neurones involved. The impression from the sensory cell passes
into the spinal cord and from the spinal sensory cell across (by two
or three intermediate neurons) to the spinal motor cell. Thence it
passes to the proper muscles. Sensation and reaction are almost
immediate and the proper movements have been made without
awakening consciousness in the cerebrum until later.

A Triumph of Coordination. — A celebrated pianist has actually
been ascertained by Sir James Paget to have played 5,995 notes in
four minutes and three seconds. Paget estimated that there were
at the rate of 96 transmissions of force from the ends of the nerve
fibers along their course to the brain, in each of the same seconds
during which there were 72 transmissions going out from the brain
along other nerve fibers to the muscles. The notes were played in
due time and place, and with the sentiment of the music. (J. A.
Med. A.)

Fatigue in the Nerve Cell — In some important studies made a
number of years ago (1892) Hodge demonstrated the effects of
fatigue on the nerve cell. He showed that after prolonged stimula-
tion of a nerve fiber its cell body and nucleus tended to shrivel, and
degeneration of the cytoplasm became apparent. The whole
structure might be compared to a shriveled apple. Later studies
by DoUey ^^ confirm Hodge's conclusion. There is only slight evi-
dence of increased CO2 in the nerve fiber after stimulation.

Regeneration in the Nervous System. — Since there is no neu-
rilemma in the spinal cord and in the brain there is no complete
regeneration. The nerves of the body will readily regenerate,
provided the nucleus of the nerve cell is uninjured.

Myelination. — Recently the entire process of myelination of
nerve fibers ^^ has been seen by Speidel (J. of Exp. Zool. in press) in
the transparent tail fin of living frog tadpoles. Individual nerve
sprouts and sheath cells were watched for long periods (ten days to

12 Hodge, C. F. 1892. Jour, of Morphol., vol. 7; Jour, of Physiol., 1894, vol. 17.
Dolley, D. H. 1917. Jour. Comp. Neurol., vol. 27, pp. 299-324.

13 Nerve cells and sheath cells may readily be cultivated in vitro, and the growth of
nerve fibers observed, but the formation of the myelin sheath has never been obtained
in artificial media.

48o MAMMALIA— PHYSIOLOGY

several months). Primitive sheath cells on the early unmyelinated
nerves multiply and migrate to the advancing "myelin-emergent"
sprouts and myelin segments are added distally in an orderly man-
ner. Each segment is formed through the combined action of a
sheath cell and a myelin-emergent fiber. Myelin of a segment first
appears near a sheath cell nucleus and extends progressively in both
directions. Unmyelinated gaps between adjacent myelin segments
may be filled in later by the intercalation of new segments. End-to-
end anastomosis of segments sometimes occurs with complete ob-
literation of the intervening node of Ranvier. A portion of one
segment may be appropriated by another segment, accompanied
by the establishment of a new node. (Courtesy of C. C. Speidel.)

Hibernation and Aestivation in Animals. — Certain amphibia,
reptiles and mammals are able to go into a sleep when the tempera-
ture falls. Hibernation is marked by a reduction of all body proc-
esses to the minimum. For example, the hibernating dormouse
periodically takes a dozen respirations, then ceases breathing for
several minutes. Normally, when awake, it respires at the rate of
80 times a minute. A summer resting period, known as aestivation^
is characteristic of the mudfish {Protopterus) and of certain amphibia,
reptilia, and a few mammals.

Organs That Man Can Lose. — A leg, an arm, an eye, his tonsils,
gonads, spleen, appendix, gall-bladder, part of his lungs, part of
his brain, and as much as twelve feet of his intestine may be re-
moved without serious results*. Entire lobes of the lungs have been
removed, with beneficial result?.

Statistics of Vitality. — Muscles of the human heart are alive 2
hours after normal heart beat and respiration have ceased. The
body muscles are alive 5-6 hours thereafter. Muscles of a rabbit
will live Zyi hours after the death of the animal. Those of a sheep
survive io>^, those of a dog 11^ and those of a cat I2>^, those of a
frog 24-30 hours.

Susceptibility of Mammals to Poison. — The porcupine or
" hedgehog " takes with apparent enjoyment a dose of cantharides
that will kill several persons under excruciating pains. In rabbits
and dogs, morphine causes vomiting and then light sleep, but more
depression in the rabbit. The rabbit can take more morphine than
can a man fifty times the animal's weight. Morphine first causes
wild excitation in the cat and other Felidae and then depression of

MAMMALIA— PHYSIOLOGY 48 1

the intelligence. Small doses of tnorphine produce sleep in the goat,
horse and ass. Amygdalin does not affect dogs, but kills rabbits!
An especial degree of tolerance to atropine is found in the herbivora.*
Atropine effects pass off in rabbits' hearts sooner than in other
animals by the active decomposition of the alkaloid which occurs
in their plasma. Rabbits are not susceptible to belladonna. Rats'
hearts are much less susceptible than rabbits' to digitalis. Doses
of lead and nicotine sufficient to kill a man do not injure the goat.

CHAPTER XXI

Social Life of Animals
Association of Different Species

Living Free. — Free living forms are those that are at liberty to
range independently. They feed upon animals, and are then called
carnivorous^ or they feed upon plants, usually destroying them
although not necessarily causing their death, and are called herbiv-
orous.

Commensalism. (Lat. com^ together; and mensa, table.) —
Commensalism as we shall treat it consists in an association for
mutual benefit less permanent than symbiosis. Commensalism
may be for protection, transportation ov food.

The best known example of commensalism is the case of the
hydroid colony living on the shell of a hermit crab. As the hydroid
furnishes the crab with camouflage and protects it from enemies by
the use of its stinging cells, it renders some service in return for
transportation and for particles oi food broken up by the crab.

Symbiosis. (Gr. syn, together; and bios, life.) — The term
symbiosis has by some been applied to all intimate associations
between organisms (including parasitism); by others to relations
between organisms in which benefits are mutual; and by still others
to plants living within the body of animals in a presumably beneficial
relationship. Until recently, zoologists considered symbiosis in
the broad sense, holding that it refers to ani7nals or plants living
together for mutual benefit. It is now applied to relationship be-
tween plant and animal; animal and animal; or plant and plant; it
always being understood that no parasitism occurs. Lull calls it
the most intimate association for ynutual benefit, an extremely close
commensalism. We shall consider symbiosis in the latter sense.

Symbiosis may be between a green chlorophyll-bearing plant
and an animal; between a chlorophyll-bearing plant and a colorless
one; or between two animals. Bacteria living in the digestive tracts
of animals are to be considered as an example of symbiosis since they
seem beneficial. Certain ruminants, apes, and South American
rodents are able to digest cellulose by means of the Ophryoscolecidae,

482

SOCIAL LIFE OF ANIMALS 483

which are ciliated Protozoa inhabiting their digestive tracts (p. 30).

An example of animal-animal symbiosis is the case of termites
which live in beneficial relationship with the flagellates, Tricho-
nympha and allied genera (p. 29).

Parasitism. (Gr. para, beside; sitos, food.) — In Biology,
parasitism is the condition of an organism which obtains its nourish-
ment wholly or in part from the body of another living organism
and which usually brings about some modifications in both guest
and host. In true parasitism, the bodies of the host and the parasite
must be in temporary or permanent contact other than that in-
volved in preying and capturing. The presence of the parasite
must not be beneficial. Ectoparasites may be temporary such as
plant lice, caterpillars, mosquitoes, flies and the leech; or permanent,
such as bird lice (for the bird), body lice and chigoes (chiggers).
Endo-parasites include intestinal worms like the tapeworm, hook-
worm, and pin- worm; and blood parasites such as the malarial
sporozoan and the filarian worms.

The Effects of Parasitism. — i. On the Parasite. — Any parasite
may undergo some degeneration. In many cases, little remains
but the reproductive apparatus.

1. On the Host. — The host may be very resistant, and by gather-
ing extra food render the parasite harmless; many white blood
corpuscles may be assembled and carry away the organisms. The
host may enclose the parasite in a cyst; it may develop counter
poisons, killing the parasite; or anti-bodies may neutralize the
injurious substance formed by the parasite. The host, for some
time apparently uninjured, may have its resistance so lowered by
the rapid multiplication of the parasites that it will succumb to
what ordinarily might be a minor ailment or injury.^

Association of the Same Species

Colonies. — (i) Certain hydroids have a diverse differentiation
of the individuals. Coelenterate polyps are modified for feeding,
reproduction and locomotion. (2) The " Portuguese Man of War "
has specialized structures for feeding, reproduction and protective
and aggressive activities. (3) Sponges have cellular differentiation
for protection, ingestion, storage, distribution of food and reproduc-

^ See Stunkard, H. W. 1929. Parasitism as a biological phenomenon. Sc.
Men., vol. 28, pp. 349-362, April.

484 SOCIAL LIFE OF ANIMALS

tion. Some biologists are disposed to regard the higher organisms
as colonies of lower forms.

Communities. — (i) Bees have a queen (reproductive), the male
drones (reproductive) and the workers which are only short-lived
laborers. The chosen queen is fed " bee bread." (See Sex Deter-
mination, page 533.) (2) Termites or " White ants." The workers
are small, blind, wingless, pale in color and sexually immature but
with strong jaws. The " soldiers " are blind, wingless, immature but
have highly developed scissors-shaped jaws and an enlarged head,
both heavily chitinized and darker in color than the rest of the body.
The complemental females and males are blind, wingless, and not
completely mature, but may develop to supplement in the produc-
tion of young if the true sexed individuals are not sufficient. The
true or chief females and males are darker in color than the other
castes, winged and with well-developed visual organs. They live
above ground; the others are either subterranean or with covered
tunnels. (3) True ants consist of winged males Q.nd females, workers
and soldiers. We find that there is a social evolution in ants as in
man. (Wheeler.) Foraging or maraudifig ants, like Ecitor, have
officers and scouts. Slave-holding ants, like Polygerus, have become
unable to dig, care for their young, or store up food without slaves.
The herding ants live in beneficial association, keeping aphids for
their milk, " honey dew." The harvester ants store up grains and
seeds. The thief ants {Solenopsis molestd) feed on the larvae and
pupae of larger ants, escaping into burrows too small for the avengers
to follow. The commensal ants include Leptothorax emersoni which
secure food and shelter from Myt-micae brevinoides and in return
act as barbers and manicures, probably removing parasites and
keeping their benefactors more healthy. (Wheeler.)

Gregariousness. — Herds of buffalo, packs of wolves and schools
of whales collect for protection and food. In sheep, a leader or
sentinel is characteristic of such groups. The same is true in many
other animals. Pallas states that the saiga antelopes of Siberia
change sentinels. In the •#nd reindeer, females act as sentinels and
are also said to change places when wearied by standing.

When cattle or even sheep are attacked in the wilds, they form
a circle with the males and the most powerful females directing their
horns outward, while weaker females and the young are huddled in
the center, Man is sometimes less concerned for the welfare of his
own.

SOCIAL LIFE OF ANIMALS 485

Men are not sheep, but they have two of the dominating characteris-
tics of sheep. They are gregarious and they are easily frightened.

— Ramsay MacDonald.

Polygyny (many wives), and Polyandry (many husbands). — In
the ostrich of South America the cock bird lives with five or six
hens {polygyny). All the hens lay their eggs in one nest, but incu-
bation is done by the male alone, and after hatching, the young
chicks follow the father. Each female cowbird mates with several
males {polyandry). The female deposits her eggs in the nest of
another smaller species. (See p. 349.)

Cases in Which the Sexes Live Apart. — In the case of many
antelopes the herds divide according to sex between one pairing
time and another. After the pairing season is over, wild sheep and
other ungulates live in herds composed of one sex only. In Indian
and African elephants the sexes form herds of their own, herds of
females being accompanied by their young and led by a female.
At breeding time a male temporarily takes possession of a herd of
females. Migrating salmon travel separately, shoals of males
appearing first, followed later by the females. The same is true with
the salt-water minnow {Fundulus heteroclitus).

Societies Composed of Different Species. — Different species of
dolphins form groups led by one individual. Wild zebras, asses,
yaks, and horses are sometimes seen together, while wild buffaloes
associate with elephants.

Monogamy. — All species of parrots are monogamous, while
rose-colored starlings, sparrows, house pigeons and mallards are
monogamous, but nest gregariously. In the weaver bird two cou-
ples often share a common nest in which both the hen birds lay their
eggs and hatch them out.

Seasonal Mateships. — Seasonal mating occurs in a number of
beetles, the couples living in associations, not societies. Lions
choose a fresh mate at each pairing time while in some marten species
the two sexes live together until afteriUjg young have been reared.
Foxes live monogamously and the father brings food to the young.
Wolves, foxes, and bears live mated for a short time.

Types of Families, (i) Parent Families. — In the wood-boring
beetles, the parents feed the larvae and watch over the chrysalis.
Both the male and the female of certain species of fishes guard the
nest, the hatched young returning to the nest every evening for two

486 SOCIAL LIFE OF ANIMALS

or three weeks. Parasitic egg-laying. A South American duck
{Metopiana) lays Its eggs in the nests of other birds such as the coot
and sea-gull, while the European cuckoo lays her eggs in the nests of
other birds. The American cowbird has the same habit of seeking
foster parents for her offspring. (See Friedmann, H. 1929. The
Cowbird. C. C. Thomas Pub.)

(2) Father Families. — The male obstetric frog {Alytes obstetri-
cans) carries the eggs with him in a long string wound around his
hind legs until the larvae emerge. The male Rhinodenna carries
the eggs in his gular vocal sac until the metamorphosis of the young
is complete. In some species of frogs the tadpoles are carried on the
back of the male.

The male stickle-back fish builds a nest and entices several
females to deposit their eggs in it. Eggs and young are guarded
by the father. In a number of fish species the male seizes in its
mouth young that have strayed away and brings them back to the
nest. It is said that the male Amia (the bow fin) leads its family of
young for four months.^

(3) Mother Families. — The females of some species of leeches
carry their offspring about, the young attaching themselves to the
body of the mother with their suckers and always returning to her.
The female earwig {Forjicula) guards her eggs and young in a hole
which she digs herself, collecting them together if they get scattered.
The female mole cricket digs a hole for the eggs and guards them,
but turns cannibal occasionally.

In crayfish and spiders the mother carries eggs and young around
with her. Female scorpions carry young on their backs. In a
number of species of fish the females lead their young for some time
after hatching. In some species of Chichlidae the female carries
the eggs in a pocket on the back and the female Pipa (a toad) carries
its young in pouches of skin on its back until metamorphosis has
occurred. ^a^ ^^AitM^M^^ ^p(lU4^^

Female crocodilia watch over the eggs^open them by means of a
well-developed egg tooth, ^|^lead the young to the water. Mother
families are the rule among birds. Mother families are found in the
cat family, in foxes, polar bears, and seals.

(4) Child Families. — Certain processionary caterpillars {Thau-
matopaea) , emerging from the same mass of eggs, remain together

2 Consult Gill, Theodore. 1905. Parental Care Among Fresh Water Fishes.
Smithsonian Rep., pp. 403-531.

SOCIAL LIFE OF ANIMALS 487

permanently. Herring of the same spawning form schools which
remain together permanently.

References on Animal Relationships

Alverdes, F. 1927. Social Life in the Animal World. Harcourt,
Brace & Co., Inc., New York.

BoRRADAiLE, L. A. The Animal and its Environment. Henry Frowde
and Hodder and Stoughton.

Cleveland, L. R. 1926. Symbiosis among animals with special refer-
ence to termites and their intestinal flagellates. Qu. Rev. of Biol.,
vol. I, no. I, pp. 51-60.

DoFLEiN, F. 1914. Das Tier als died des Naturganzen, from R. Hesse
and F. Doflein, Tierbau und Tierleben, Bd. 2. Leipzig and Berlin.

Elton, C. 1927. Animal Ecology. Macmillan Co., New York.

Protection

Masking. — The caddis fly lives in a sand case. Certain crabs
cut off the tunic of a sea squirt and drape it over their carapace.
Others plant sea weed on their backs.

Flounders cover themselves with sand while the toad puffer or
swell fish distends its body with air and escapes many enemies.
Other fishes cover themselves with sea weed.

Color Resemblance. — Temporary alternations of color are due
to the amount of dilation of chromatophores. In the cuttle fish
and the squid we find that blushing occurs if they are irritated,
but they return to normal pale color shortly.

Fishes, such as the flounder and the minnows, are able to adapt
themselves to the background. If they are blinded, color change is
impossible. Frogs, toads and chameleons are able to alter their
pigment {inelanophores) to suit the background, although Ditmars
holds that the chameleon is not immediately successful.

Partridges and ptarmigans change their pigment to suit the
background. The arctic hare changes from brown to white when
winter comes. In the mammals we ^pjjgl that change in color de-
pends on the oxidation of melanin pigment.

Some animals with a brilliant hue are bad tasting. The ex-
creted material makes the color bright. The skunk is an example
of a brightly colored form which has a distinctly obnoxious odor.

Thayer, Poulton and others have emphasized the influence of
coloration on the survival of many animals. Except in the arctic

488

SOCIAL LIFE OF ANIMALS

regions we find that the body Is darker on the parts ordinarily Il-
luminated by the sun and sky, while the most shaded parts are
usually lighter In color.^ In the tiger and the zebra the colors are
broken by lines and the animal blends with Its background. During
the World War, battleships were wonderfully camouflaged by lines
and patches of alternating light and dark color.

Fig. 257. Young fawn in mountain laurel, Monongahela National Forest, W. Va.
(Photo courtesy of U. S. Forest Service.)

Thayer has pointed out that even In the case of some animals
that are quite conspicuous to man and seem to stand out against the
sky, we must remember that the chief enemies of the forms under
consideration are not tall animals. He once convinced a group of
zoologists at Woods Hole, Mass., In a striking manner, by having
them crawl around in the grass, gazing up at life-size card-board
figures of deer.

^ Wild cats are striped on the ventral side and hence almost invisible in the trees
(W. R. B. Robertson).

SOCIAL LIFE OF ANIMALS 489

Mimicry. (Protective Resemblance.) — Some butterflies resem-
ble a leaf, certain beetles mimic the wasp, certain harmless flies
mimic bees and are preserved from destruction by birds. The
walking stick insect resembles twigs. Some harmless snakes resem-
ble in markings venomous forms such as the coral snake. (See
Fig. 176.)

References on Animal Coloration

Beddard, F. E. 1892. Animal Coloration.

Poulton, E. B. 1890. Colors of Animals.

Roosevelt, T. African Game Trails.

Thayer, A. H. 1909. Concealing Coloration in the Animal Kingdom.

Geographical Distribution

A similar environment does not always explain the appearance
of like forms. If we are to accept the theory that all forms are
derived from a common ancestor, we can readily explain some of the
following facts:

(a) The llamas of South America have as their nearest living
relatives the camels living in the deserts of Asia. In Oregon one
finds fossil llamas. {^) The Australian kangaroo has no relatives
nearer than the opossum. Neither is found in its native home, which
was Europe. How did they reach South America and Australia?
(c) The plants of Madagascar are not related to those of Europe
while both plants and animals of North America and Eastern Asia
are similar. Why?

Explanation. — Present barriers have not always existed, and
land connections that once joined continents have disappeared,
separating closely related forms. Climatic changes have also
produced cataclysmic effects.

Dispersal of Small Forms. — In the case of smaller forms, we
find that dispersal is effected quite readily. Protozoa and the eggs
and larvae of numerous worms and Rotifers are transported by
birds and other animals, as well as attached to wind-blown or
floating debris. It is well known that the glochidia of fresh water
mussels are carried long distances attached to the gills and fins of
fishes.

Again, driftwood bears strange companions to far distant islands.
Beebe on his Arcturus voyage counted on one floating log 54 species
of marine crabs, worms and fishes.

490 SOCIAL LIFE OF ANIMALS

•

Barriers. — (i) The salt of the sea proves a barrier to fresh water
animals. Amphibia are almost never found in salt water. It has
been found that the salinity of water determines the species of salt
marsh mosquitoes in a given region, while the Ph of the water is
apparently important in determining the distribution of Arthropod
species and of fishes. Sometimes species changes occur as in the
brine shrimp, Artemia, which alters its characteristics in fresh water

(p. 170)-

(2) Elton quotes various authors who have shown that water

supply is an important limiting factor in determining the ranges of
wild birds and mammals. In the Burmese forests the occurrence of
elephants, bufFalos, tigers, panthers, pigs and monkeys is deter-
mined in dry season by the proximity of water-holes. In the case
of rooting and digging animals, such as pigs and moles, distribution
is determined by softness of the ground which of course depends on
the water supply. In Mesopotamia the black partridge {Franco-
linus vulgaris) is never found more than a hundred yards from water,
which it requires for drinking purposes.

(3) Depth of water proves an effective barrier. Certain of the
shore fishes of Hawaii are not found in the waters of California.

(4) Temperature proves most powerful in preventing the dis-
persal of many animals and plants. Some animals are found in
hot springs or in the Arctic ice, however.

Dr. Nellie Payne has given us important information on the
survival of insects at low temperatures. Consult Payne, N. M,,
1926 (Freezing and Survival of Insects at Low Temperatures,
Quart. Rev. of Biol., vol. i, pp. 270-282). Brues, C. T. (Animal
Life in Hot Springs, Qu. Rev. of Biol., vol. 2, no. 2, pp. 181-203,
June, 1927), has summarized the literature and shown that Ameha
Umax was found in water at 50° to 52° C. (ii2°-i26° F.), while
Ciliates were found in water at 46° C. (115° F.). The crustacean
Cyclops was found in water at 36° C. and turtles appeared in water
at 44° C. (i 1 1° F.). Gudger, E. W. (Snow Worms, Nat. Hist., vol.
23, no. 5, pp. 450-456, 1923), cites cases of Enchytraeid worms and
other annelids besides insect larvae occurring in snow and ice.

(5) Mountain ranges, with the factors of temperature and amount
of oxygen available, prove most effective barriers to many forms.
Thus, in some cases, individuals have been unable to reach new
regions because of barriers; in other instances they reach the new
field but are unable to survive because of lack of adaptation and

SOCIAL LIFE OF ANIMALS

491

extreme competition. In the " Struggle for Existence " they perish.
(6) Winds also prevent some dispersal of certain insects as in the
case of the heavy trade winds. (N. A. Cobb.)

Domestication of Animals

Cat. — The house cats are derived from a single wild species, the
dun wild cat, Felis ynaniculata of Northeast x^frica. There are now
about 30 races of domesticated cats, grouped into two main classes,
the long haired and the short haired. The Mexican hairless cat
and the tailless Manx cat are interesting mutations. (See p. 524.)

Horse. — The horses of today have been traced to two wild
ancestors, Equus przewalski of Northern Asia, from which have been
derived the Oriental, the Arabian, the Mongolian, the North African
and the Eastern European races; the Equus caballus fossilis of
Europe, from which have sprung the German, Norman, English
and West European horses. In South America and in Europe,
the bones of human beings have been found with those of horses.
In Europe, prehistoric horses are associated with human relics of
the Bronze Age. The New World type, Eohippus, has been found
in the Wasatch Mts. of Western North America, in the Eocene
period. It was about the size of a fox with four toes and a fifth
digitary splint on each hind foot. In the middle Eocene, Orohippus
was about 14 inches high, with four toes on its front feet and 3 toes,
but no splints, on the hind feet. In the Oligocene period, Meso-
hippuSy about the size of a dog or coyote, had three toes on all its
feet. In the middle Miocene, Protohippus was the size of a Shetland
pony, with one long toe and two short ones on each foot. In the
Pleistocene, Equus appeared with only one developed toe and splints
of*the second and fourth on each foot. Remains of the Old World
type, Hyracotheriujn, have been found in the London clay and the
Eocene formations of Europe.

Donkeys have been derived from two wild species, the Nubian
desert donkey, Equus taeniopus, and the onager, Equus onager, of
Eastern Asia. The Asiatic wild ass is exceptionally fleet. There
are today three varieties, the largest, called the kiang, found in
Thibet and up to the snow line. The second, the ghorkkar or onager,
found in the plains of Afghanistan, is smaller and silvery white.
The third variety, found in Persia and Syria, is the one described in the
Bible. The African ass is found throughout Northeastern Africa.
It ranges westward on the deserts and is exceedingly speedy.

492

SOCIAL LIFE OF ANIMALS

Dog. — The dog is supposed to be the oldest domesticated animal.
From the savage Australian Bushman to the cultivated people of the
world's greatest cities, we find that the dog is a companion and
servant. He seems happiest in caring for the possessions and person
of his master and will follow and protect the drunken sot or the filthy-
beggar.

There are about 200 breeds of dogs, 50 breeds being sportmg
dogs. Theories of the origin of the dog place his ancestry as from
the wolf or a jackal-wolf hybrid, although there are seven wild
species which may have been contributory. The reputed ancestors
include the jackal of Western Asia, the jackal-wolf of northeast
Africa, the landga of India, the walgie of Thibet, and the coyote
and gray wolf, both of America. Fossils of the American dog are
found in the Southern Appalachian Mountains near the Cumberland
Gap in Eastern Tennessee.

Collie. (Photo by courtesy of James B. Vallely.)

SOCIAL LIFE OF ANIMALS 493

Senator Vest's Eulogy on the Dog

" Gentlemen of the Jury: The best friend a man has in this world may-
turn against him and become his enemy. His son and daughter that he
has reared with loving care may become ungrateful. Those who are
nearest and dearest to us, those whom we trust with our happiness and
our good name, may become traitors to their faith. The money that a
man has he may lose. It flies away from him when he may need it most.
Man's reputation may be sacrificed in a moment of ill considered action.
The people who are prone to fall on their knees and do us honor when
success is with us may be the first to throw the stone of malice when
failure settles its cloud upon our heads. The one absolutely unselfish
friend a man may have in this selfish world, the one that never deserts
him, the one that never proves ungrateful or treacherous, is the dog.

" Gentlemen of the Jury: A man's dog stands by him in prosperity and
poverty, in health and in sickness. He will sleep on the cold ground,
when the wintry winds blow and the snow drives fiercely, if only he may
be near his master's side. He will kiss the hand that has no food to
offer, he will lick the wounds and sores that come in encounter with the
roughness of the world. He guards the sleep of his pauper master as if
he were a prince.

"When all other friends desert, he remains. When riches take wings
and reputation falls to pieces he is as constant in his love as the sun in
its journey through the heavens. If fortune drives the master forth an
outcast into the world, friendless and homeless, the faithful dog asks no
higher privilege than that of accompanying him, to guard him against
danger, to fight against his enemies, and when the last scene of all comes
and death takes his master in its embrace and his body is laid away in
the cold ground, no matter if all other friends pursue their way, there by
his graveside will the noble dog be found, his head between his paws and
his eyes sad, but open in alert watchfulness, faithful and true even to
death." "

* The dog that called forth this tribute to canine affection and fidelity was Drum,
a foxhound, owned in Johnson County, Missouri. He was shot by a man who was
later sued for damages by Drum's owner. Learned counsel were engaged by both
sides and the case was finally tried before a jury in the State Circuit Court, in 1870.
The late U. S. Senator George G. Vest made the closing plea for the plaintiff, the
peroration of which is printed above. Court, lawyers and audience were entranced by
it. Heavy damages were awarded the plaintiff, and Vest's Eulogy on the Dog stands
as the most eloquent and touching tribute ever paid to man's faithful friend. Cour-
tesy of American Humane Education Society, Boston.

494 SOCIAL LIFE OF ANIMALS

Pigs. — Our modern hogs are descended from two wild races, the
European Wild Boar, Sus scro/a, and the species Sus viltatus, found
in Eastern Asia. From the Asiatic form have descended most of
the European races. The Chinese domesticated the hog centuries
ago.

Cattle. — Present races of cattle have descended from two sources,
the wild bayiteng^ Bos sondakus, of South Asia, from which have come
the zebus, the Egyptian longhorns and the Spanish and Alpine cattle
of Europe; and the European wild ox. Bos primigenius, from which
have come the English, North German and Holland cattle. The
latter form, sometimes called the Aurochs, reached a height of 7
feet at the withers. It had horns 6 feet in length, one of which
held three quarts of wine. In India there now live four species of
wild oxen closely related to the aurochs.

Goats are descended from three wild races, Capra aegagrus, of
Western Asia, Capra/a/coneri, and Capj-ajew/aica, of the Himalaya
Mountains.

Sheep originated from three wild sources, Ovis musimon of South
Europe, Ovis tragelaphus of North Africa and Ovis ar-kal of Western
Asia. The last named form was the ancestor of our American races.
The species best known is the Mouflon which is still hunted in the
mountains of Corsica and Sardinia. Early Assyrian drawings show
fat-tailed domesticated sheep. In the Himalayas, one finds the
great guljar or Marco Polo's sheep which ranges 18,000 feet above
the sea in the summer. Old rams are almost white with circling
horns, five feet on the outside curve.

Rabbits. — There are over 70 species of rabbits, and the 15 races
of domesticated rabbits orginated from wild species found in Spain
and Southern France. The original European wild rabbit was
grayish brown.

Pigeons. — All the domestic pigeons descended from a single wild
species, Columba livia, the common rock dove, found in Europe, Asia
and Northern Africa. The Romans were pigeon fanciers 3,000
years ago. Homing pigeons were used by the crusaders who sent
messages back from the wars.

Fowls. — Modern races of chickens are supposed by naturalists to
be descended from the jungle fowl, Galhis bankiva, which is found
through most of the islands adjacent to India. The heavier breeds
are probably descended from the Malayan fowl called the Aseel.

SOCIAL LIFE OF ANIMALS 495

Ducks. — The wild duck, Anas boschos, the ancestor of our domes-
tic species, is found both in China and in Europe.

Geese are the oldest birds tamed by man. The ancestor of our
races is Anas cinereus. The early Egyptians tamed the Nile goose,
Chenalopex egyptiaca.

Peacocks. — Domesticated peacocks have descended from the
wild Indian species, Pavo cristatus.

Turkeys have descended from two wild North American species,
Meleagris gallopavo and a Mexican variety. We now have four wild
sub-varieties. (Robertson.)

Tissue Survival Outside the Body

The pioneer in tissue culture, Dr. R. G. Harrison of Yale, showed
many years ago that fragments of frog embryos isolated from the
organism would develop for a number of days. His classic experi-
ment on the development o{ neuroblasts in a hanging drop paved the
way for much important experimentation. Montrose Burrows was
another important figure in the development of the technique of
tissue culture.

Dr. Alexis Carrel, of the Rockfeller Institute, started the culti-
vation of minute fragments from the heart of a chick embryo on
January 17, 1912.^ Since that time he and his associates have
carefully subdivided the culture, washed it in Ringer's solution and
cultivated it again in a medium composed of diluted plasma.
Carrel states that if the tissues had been able to survive for 16 years
without trimming or hindrance, the mass would now be greater
than that of the solar system. He emphasizes the fact, however,
that cells massed together as a closed system must necessarily under-
go the process of aging.

The immortality of protozoa (see page '^i^^ is due to their ability
to eliminate products of metabolism directly into the outside world.

Carrel mentions the property of cell proliferation found in iris
epithelium and thyroid epithelium, which have been cultured at the
Rockefeller Institute for several years.

5 Carrel, A. 1924. Tissue culture and cell physiology. Physiol. Rev., vol. 4, no.

I, pp. 1-20.

Fischer, A. 1925. Tissue Culture. Wm. Heinemann, London.

Sundwall, J. 1912. Tissue Proliferation in Plasma Medium. Bull. no. 81,
Hygienic Laboratory, U. S. P. H. S.

Willmer, E. N. 1928. Tissue culture from the standpoint of general physiology,
Biol. Rev., vol. 3, no. 4, pp. 271-302.

496 SOCIAL LIFE OF ANIMALS

E. N. Hoppe, 1928 (Tissue Culture of Guinea Pig Cardiac Mus-
cle, Arch. Zellforsch., vol. 7, p. 352), devised a very simple
technique for the continuous cultivation of normal tissue of mam-
mals without the introduction of foreign plasma or other substances.
It is uncomplicated enough to use as a routine experimental pro-
cedure. The author has used it to study the action of toxins on
tissues.

Its superiority over the ordinary technique of tissue cultures lies
in the fact that homologous plasma is used. In ordinary tissue

Table of Longevity
Longevity of Mammals
Animal Reputed Age

Elephant 30 to 80

Horse family 15 to 40

Rhinoceros 37

Hippopotamus 35

Cattle 30

Dogs 30

Lions, tigers 25

Cats 23

Giraffe 20

Sea lions 18

Llama 17

Tropical fruit bat 17

Badger I4

Hare and rabbit 10

Mice and rats 5

Consult P. C. Mitchell, On longevity and relative viability in mammals and birds.
Proc. Zool. Soc. of London, 191 1, pp. 425-548, for a more accurate report on mammals
and birds in captivity. He records data on over 20,000 species.

Longevity of Birds

Animal Reputed Age

Parrot 100

Swan 70

Eagle, owl 68

Golden eagle 60

Pelican 52

Duck 50

Goose 23

Fowl 20

Canary 20

SOCIAL LIFE OF ANIMALS 497

Longevity of Reptiles

Animal Reputed A^

Giant tortoise loo

Indian crocodile loo

American alligator 40

Boa constrictor 23

Sphenodon, lizard 14

Chameleon 4

Consult S. S. Flower, Contributions to Our Knowledge of the Duration of Life
in Vertebrate Animals. III. Reptiles. IV. Birds. Proc. Z06I. Soc. of London, 1925,
p. 911 and p. 1365.

Longevity of Amphibia
Animal Reputed Age

Frog 12 years

Toad 2,^ years

Longevity of Fishes

Eel 60 years (in Roman

ponds)

Longevity of Arthropods

River crayfish 20 years

Ant 15 years

Spider (tarantula) 15 years

Beetle 5 years

Queen bee 5 years

Worker bees 6 to 8 weeks

Longevity of Annelida
Leech 27 years

Longevity of Coelenterata
Sea anemone 59 years — recorded

The Passerine birds are extremely short lived, most of them not exceeding 5
years in captivity.

culture work, bird plasma is added because it lacks the blood platelets
and therefore does not clot so quickly. (See page 457.)

At the spring meetings of the American Association of Anato-
mists in 1929, Dr. W. H. Lewis demonstrated moving pictures of
rabbit ova developing in autoserum. The fertilized eggs were
removed from the uteri at 21 to 71 hours and kept in autoserum,
sometimes augmented by embryonic juice.

498 SOCIAL LIFE OF ANIMALS

Pulse Frequency

That there is a quite definite correlation between longevity
and rate of pulse beat was strikingly manifested to the writer on
comparing his tables with the records furnished in Clark's studies
on the physiology of the heart.^ The rodents with a life span of
from 5 to lo years range in pulse frequency from 2oo to 520 pulse
beats a minute. On the other hand the cat, known to live 23 years,
has a pulse rate averaging about 200, while the dog, with a life span
of 30 years, has a pulse rate of from 105 to 125 per minute. In birds
the canary and the goldfinch, with a longevity of about 20 years,
prove to have a pulse rate of about 1,000 per minute, but ducks and
geese, with a longevity of 30 to 50 years, have a pulse beat of but
150 to 300. In the cold-blooded animals, the pulse rate is much
reduced, but a correlation exists as seen in the crocodile which is
said to live 100 years, and which has a pulse rate of from 22 to 47 a
minute.

Reading this section in galley proof, O. C. Glaser stated that such
a relationship appears to be in harmony with the results obtained
by himself (1931) on the relation between heart beat and age in
fishes, birds, and mammals.

^ Clark, A. J. 1927. Comparative Physiology of the Heart. Macmillan Co.,
N. Y.

CHAPTER XXII

Evolution, Heredity, Eugenics

Biologists recognize the existence of two factors responsible for
the characteristics of living organisms. These are heredity and
environment.

Heredity includes what is handed on from parent to offspring.
Sir Ray Lankester says: " Our body cells are merely a husk to pro-
tect the germ cells until they are set free to multiply and to start
a new individual or husk enclosing in its turn a certain number of
cells of the initial germplasm."

Environment, beginning before birth and continuing until
death, includes all physical and chemical forces, acting from without
on the germ, embryo, larva, and adult. Profound changes are
induced before puberty, and for that matter all through life, as food-
stuffs, temperature, oxygen and other factors stimulate or retard
the glands of the body regulating growth and metabolism.

The development of civilization is said to be dependent upon six
factors: geographic or climatic conditions, race characteristics, food,
social heredity, physical heredity and health. Studies made by the
Army and by the United States Public Health Service indicate that
not more than fifty per cent of our population are physically fit.
It has been demonstrated repeatedly that with improved conditions
of health, vice and crime diminish, civilization advances and the
whole standard of living improves to the point where past luxuries
become the every day equipment of a family.

Germplasm and Somatoplasm. — For centuries observers have
been impressed by the resemblance which children bear to their
parents. There seems to be a transmission which is certain but
which appears to obey no law, apparently affecting insignificant
details and transmitting them with striking fidelity.

Careful study of the body of an organism shows that there are
two kinds of cells, the body cells and the germ cells. The body or
somatic cells are those that differentiate to form the tissues of the
body. The germ cells are those which are destined to give rise later
to an independent organism. Both male and female germ cells

499

500

EVOLUTION, HEREDITY, EUGENICS

arise from primordial cells. Early in embryonic development it is
difficult to tell whether these cells are to form male or female gonads.
Cell Division. — The multiplication of cells by the process of
cell division continues after maturity, and in most cases throughout
life. Cell division consists of direct division or amitosis and, most
commonly, of indirect division or mitosis.

Direct Cell Division — Amitosis. — In this form the nucleus
divides into two daughter nuclei without any apparent preliminary

change in its structure.
The division of the nucleus
may or may not be fol-
lowed by division of the
cell body.

Amitosis is found in
the epithelium of the blad-
der, and in the placenta.
It is apparently normal
in, although not exclus-
ively characteristic of cart-
ilage, tendon and bone-
marrow. Some hold that
Fig. 258. Epithelial cells from ovary of it is a sign of degeneration,
cockroach. (From Bailey's Histology. Courtesy while Others believe it tO
of William Wood & Co.) be a sign of rejuvenation.

In Protozoa (page 42) it
regularly occurs, as does mitosis also, but in the germ cells and
in early embryonic cells division is indirect, e.g. by mitosis.

Indirect Cell Division — Mitosis. — In this form of cell division the
nucleus gives rise to two daughter nuclei, but only after the chro-
matin content has undergone certain characteristic changes.
/. Prophase: (a) As the cell prepares for division there is a
transformation of the nuclear substance involving both physical
and chemical changes. The chromatin loses its net-like arrange-
ment, increases in staining power and eventually forms a definite
number of chromosomes characteristic of the species.

At first the chromatin is transformed into a convoluted, closely
coiled thread, the skein or spireme. In many species a longitudinal
split in the chromosomes becomes apparent at this time. The
closed skein gradually opens, the nuclear membrane disappears, and
the nucleoli are merged in the skein. In some forms the chromo-

Fig. 259. Mitosis. A, resting cell with nucleus and true nucleolus; r, attraction
sphere with two centrosomes. 5, early prophase. Spireme formed; nucleolus still
present; two centrosomes connected by fibers of achromatic spindle to form amphiaster.
C, later prophase. Spireme segmented to form chromosomes; achromatic spindle;
polar rays; nuclear membrane fading. D, end of prophase. Monaster, with mitotic
figure complete; chromosomes aggregated at equator of nucleus; centrosomes connected
by fibrils of achromatic spindle. £, metaphase. Longitudinal cleavage; splitting of
chromosomes to form daughter chromosomes, ep; n, cast-off nucleolus. F, anaphase.
Daughter chromosomes passing along fibrils of achromatic spindle toward centrosomes;
division of centrosomes; if, interzonal fibres or central spindle. G, late anaphase.
Formation of diaster; beginning division of cell body. H, telophase. Reappearance
of nuclear membrane and nucleolus; two complete daughter cells, each containing a
resting nucleus. (From Wilson, The Cell. Courtesy of The Macmillan Co.)

502 EVOLUTION, HEREDITY, EUGENICS

somes develop from the nuclear reticulum without the formation of
a spireme.

The centrosomes move apart and about each centrosphere appears
a group of radiating lines called the aster. Between the centro-
spheres other lines form the spindle. The spindle and asters, stain-
ing lightly, are called the achromatic figure, or arnphiaster.

The chromatin thread {spireme) breaks into segments called
chromosomes^ which group themselves in the equator of the spindle,
forming the chromatic figure called the equatorial plate. ^

II. Metaphase. — The chromosomes which have split lengthwise
now separate into two exactly similar groups. As we shall see later
this equal distribution of chromatin has great significance.

///. Anaphase. — As the chromosomes divide, the daughter
chromosomes draw apart and diverge in two groups to opposite
poles of the spindle. The two masses are connected by a bundle
of achromatic fibers, called intej-zonal connecting fibers. In the later
anaphase stages, the cell membrane shows signs of the constriction
which will later produce two daughter cells.

IV. Telophase. — The entire cell divides into two by a plane
passing through the equator of the spindle. This is often indicated
before division takes place by a peculiar modification of the cyto-
plasm in the equatorial plane outside the spindle.

Each daughter cell receives a group of chromosomes, half of the
spindle, and one aster with its centrosome. The daughter chromo-
somes become thickened, and form a daughter spireme, similar to
that of the mother nucleus.

Then the prophases are to some extent retraced, in inverse order,
the chromosomes returning from the spireme to a chromatic net-
work. The astral rays disappear, and the nuclear membrane
returns.^

^ Heilbrunn, studying the viscosity of protoplasm in the eggs of echinoderms
annelids and molluscs during mitosis, found two maxima of increase, one in the pro-
phase and a second j ust prior to cleavage. Chambers, using the micro-dissection needle,
found also that the viscosity of the aster decreases from the center towards the periph-
ery. (Consult L. V. Heilbrunn, The Colloid Chemistry of Protoplasm. Protoplasma
Monographieren, Geb. Borntraeger, Berlin, 1928, and The Viscosity of Protoplasm.
Quar. Rev. of Biol., vol. 2, pp. 230-248, 1927.)

^ In the sea urchin, 7 successive divisions, giving rise to 128 cells, may occur in 3
hours. During the life of an individual, dividing cells are to be found at all times.
Jolly reported that in the salamander, the prophases took 50 minutes, the metaphase
but 4 minutes, the anaphase 48 minutes, and that reconstruction took but 39 minutes.

EVOLUTION, HEREDITY, EUGENICS 503

Gametogenesis {gametes, spouse; and genesis, root or origin). —
The essential organs for reproduction are the ovaries and the testes.
In the ovary are formed the ova, or eggs, and in the testes are formed
microscopic elements called spermatozoa. Except in a few of the
lower animals, the development of an ovum into a new individual
is made possible only by its fertilization by a spermatozoon. (See
page 506.)

Prior to the process of fertilization there are certain preparatory
changes which have an important bearing on the condition of the
mature eggs and sperms. During these preliminary changes, we
find a series of ?nitoses (see page 500) accompanied by a rather
striking method of reduction in the number of chromosomes such
that only one-half the original number is present in egg and sperm
when fertilization takes place. In the body cells and the early
germ cells, the chromosomes occur in duplicate series, one member
of each series being derived from the male and the other from the
female parent. The gametes (mature germ cells) each contain a
single {hafloid) group, while the fertilized egg (zygote) contains a
diploid group.

Since the chromosomes are the only structures known to be
contributed equally by the two parents and since offspring inherit
equally from both parents, except in regard to sex and sex-linked
characters (see page 535), the chromosomes are believed by most
biologists to be the bearers of the hereditary determiners or genes.
(See page 538.) Correlated with this view is the belief that each
chromosome maintains its individuality through the various phases
of mitosis. Evidently, then, the number of chromosomes would be
doubled at each fertilization without some mechanism for keeping it
constant.

Fogg (Jour. Morphol., 1930, vol. 50) has a new and striking con-
ception of chromatin diminution quite at variance with the texts
and monographs now extant. He holds that the diminution of
chromatin is not directly concerned with genetic variations, and
plays no primary essential part in differentiating the germ line from
the somatic.

In Ephestia, Fogg shows that It is clearly non-genic. It is to be
considered rather as the casting out of residual material sooner or
later in the mitotic stages.

Spermatogenesis (formation of spermatozoa). — The sperma-
togonia undergo a period of multiplication by mitotic divisions (see

504 EVOLUTION, HEREDITY, EUGENICS

page 500) at the end of which they are transformed into Jirst spermato-
cytes. At this time each cell increases in size and like or homologous
chromosomes, which are already split longitudinally, become asso-
ciated in pairs (pseudo-reduction), the usual process being a side-by-
side synapsis, forming a quadruple chromosome known as a tetrad.
Two of the parts are maternal and the other two, paternal in origin.
Any two parts are known as dyads.

Two maturation divisions follow in rapid succession without
further splitting of the chromosomes, and separate the four parts
of each tetrad into different cells. The two maturation divisions
acting as a unit separate the parts of a chromosome that were
derived from one parent from those that were derived from the
other. This reduction (segregation) may occur at either maturation
division. If a tetrad chromosome divides along the lengthwise
split (equationally) at tho. first maturation division, then each dyad
is one-half paternal and one-half maternal in origin. For such
dyads, the second maturation division segregates the maternal part
from the paternal.

On the other hand, those tetrads which separated at the first
maturation division along the line of synapsis give one dyad of
paternal and one dyad of maternal origin. That is, segregation for
such a pair occurs at the first maturation division, and the second
division is consequently equational or longitudinal.^ In either case
the four resultant cells are called spermatids, each containing one-
half the number of chromosomes found in the original spermato-
gonium. But while a complete haploid series is maintained, the
spermatids differ as to the parental source of the various chromo-
somes, now monads, the assortment being a random one. Such a
process of segregation (reduction) is characteristic of the maturation
divisions.

From the spermatids develop the mature spermatozoa, each
with a head which contains the chromosomes, a body, and a slender
tail, used in locomotion. The question of accessory, " sex deter-
mining " chromosomes will be discussed on page c^^Z-

Oogenesis. — As in the development of the male germ cells, we
find that the oogonia undergo a period of multiplication, dividing
by ordinary mitosis (page 500).

At the end of their preliminary mitoses, the oogonia are called
primary oocytes. They rapidly increase in size and their longi-

^ Both divisions are longitudinal.

EVOLUTION, HEREDITY, EUGENICS

505

tudinally split chromosomes meet {synapsis) in pairs, each of which
is composed of one maternal and one paternal chromosome. Thus
a quadruple chromosome {tetrad) is formed as in spermatogenesis.

SPERMATOGENESIS

OOGENESIS

Primordial
Germ Cell

Specmafo qonia

Multiplication Period
(Diploid Number of
Dqad Chromosomes.
Mantj Generations)

Growth Period

(Si^napsis or Union of

Like D II ads to Form

Ha pi old Number of

Tetrad Chromosomes

No DiOisions)

First Oocijte'

Maturation Period
(Two DiOisions. First
Produces Dyad Chromosome^
Second GiOes
Monad Chromosomes
Which Later
Split
Londltudinallu )

r\^ Transformation

\yj\ Period
C^^^j (Applies to
■-^^ t^ale Germ
Cells Onlij)

Primordial
Germ Cell

Ooqonia

Second Oocyte
and First
Polar BodlJ

t^ature Oi/um

and
Polar Bodies

Fertilization and Cleaoaae

Fig. 260. Diagrams of spermatogenesis, oogenesis, and fertilization. Chromo-
somes derived from female are shown in solid color, those from male in outline. Sex-
chromosomes are shown with roughened contours. The diploid complex consists of a
double series, both as to size and shape, with the exception that the male has only one
sex chromosome. Note that it is always derived from his mother. (Courtesy of E.
Carothers, 1931).

Subsequently, in the fi7-st maturation division, the tetrads divide
into dyads, then in the second maturation division they divide into

5o6 EVOLUTION, HEREDITY, EUGENICS

single components, called monads, just as in the development of the
spermatid.

During the first maturation division, the spindle appears near
the periphery, and the nuclear material is divided equally, but the
cytoplasmic material most unequally, so that the resultant budded
''first polar body " is extremely small. It may later divide, but
becomes degenerate and of no significance. The larger cell is called
the secondary oocyte.

In the second maturation division, the members of the dyads of
the secondary oocyte are separated but the cytoplasm is again
unequally distributed and the second polar body is given off. The
larger cell undergoes no further changes (in contrast to the sperma-
tid) but becomes the ^nature egg. Just as in the spermatozoa, we
find that the eggs contain one-half the number of chromosomes
present in the oogonia.^

Fertilization. — In many of the lower animals we find that fertili-
zation takes place after the eggs are laid, but in higher forms, such
as reptiles, birds, and mammals, it occurs in the oviduct of the fe-
male.

In some forms the spermatozoan enters the egg before the polar
bodies are formed, in others it may enter after the first polar body
is formed, but before the second has been produced, and in still
others, maturation of the egg has been completed before a sperma-
tozoan is admitted. Polyspermy is not unknown, but in most
animals only a single spermatozoan penetrates the egg.

The spermatozoan forms a jjiale pronucleus, which unites with
the female pronucleus, and subsequent divisions are by ordinary
mitosis.

Two species of fishes, having different shaped chromosomes, were
hybridized by Dr. Moenkhaus, who showed that there can be no
question that subsequent multiplication of the cells of the fertilized
ovum is accompanied by the equal distribution of chromatin from
each parent.

The chromosomes split longitudinally into two parts, separate,
and group themselves in two clumps around the poles of a delicate
spindle; then the cell divides. Thus by mitotic division beginning

* Carothers, E. E. 1926. The Maturation Divisions in Relation to the Segrega-
tion of Homologous Chromosomes. Quart. Rev. of Biol., vol. i, pp. 4I9-435. The
sections on mitosis and gametogenesis were corrected by Dr. Carothers.

Union of the Hdploid Groups, rertillzalm

Zygote

Division of the Diploid Group Mitosis

:s^-~_'^/}

Reduction of the Diploid Groups to Hdploid. Melosls.

Synapsis Disjunction Haploid Groups. Qametes.

yia.Bb.Cc.Dd. ABCd,

Recombinations in FertlUz<ation.

AbcD. etc

Summary of Chromosome Behavior and Relationship

In the germ cells, egg and sperm, the chromosomes are not paired. The four
shown for illustration are distinguished by relative lengths. The maternal elements
are shown In outline and identified as A, B, C, D; and the paternal in black, as a, b,
c, d. On fertilization the zygote acquires the double or diploid number of chromo-
somes— that is, It now has four pairs, one of each pair from the rriother (egg)
and one from the father (sperm). The constitution of the new individual is, Aa,.
Bb, Cc, Dd. In the course of normal cell division (Mitosis) each member of each
pair divides into two; and each daughter cell has a full complement of chromosomes,
continuing: the composition of the zygote. When new germ cells are being formed
the diploid number is again reduced (Meiosis), the members of each pair going to two
different cells — but the separation is random. Thus, the two new gametes illustrated
show the combinations aBCd and AbcD, sixteen different combinations being possi-
ble for four chromosomes (4-) When fertilization takes place,
with 16 types of sperms and 16 types of eggs, mating Is random and there are 256
possible combinations (16^), of which seven are shown. From Wilson, The Cell in
Heredity and Development, published by The Macmillan Company."

Fig. 261.

5o8

EVOLUTION, HEREDITY, EUGENICS

I, 2, 4, 8, etc., the germinal substance is transformed by " cleavage "
into the new organism.^

Cleavage and Organ Formation.-

C^ P

4.-'*' -;2^-N

^-c=» §=»— /

Gametes

Fig. 262. Reduction Division In Relation
to Sex Determination. (After Gruenberg, Evolu-
tion, published by D. Van Nostrand Co., Inc.)

The chromosomes of the male (light) parent
(P) differ from those of the female parent (dark)
in the form of the Y chromosome. As gametes
are formed, one of each pair of the X chromo-
somes (black) goes to each egg. In the forma-
tion of sperms, however, half get the X chromo-
some and half get the Y chromosome: there is
only one kind of egg, but there are two kinds of
sperms. In the following generation, Fi, the
sperms containing the X chromosomes give rise
to females, and those containing the Y chromo-
somes give rise to males. Both males and
females of this generation, however, derive half
the chromosomes from the father and half from
the mother.

^ Consult the paper by H. B. Goodrich, 1929,
Rev. of Biology, vol. 4, no. i, pp. 83-99, March.

-Subsequent to fertilization
certain changes take place
converting the egg cells
into cells that multiply and
form the embryo. Cleav-
age may be cotnpkfe, and
equa/ as in Amphioxus or
unequal as in the frog.
On the other hand it may
be partial, and either super-
ficial as in the eggs of Arth-
ropods or discoidal as in the
chick.

One of the most fascin-
ating studies imaginable is
that of organ formation
from the primitive embry-
onic state. It is possible
to follow the development
of some invertebrate types
such as worms and molluscs
from the one-cell stage to
the actual development of
complete organs. Their
condition of semi- trans-
parency and the distinctive
colors of certain developing
organs render this task
quite easy. The nervous
system has been traced to
the two-cell stage in Cre-
pidula, a mollusc, by Dr.
E. G. Conklin.

Germinal Layers. —
At the end of cleavage
(segmentation) the egg is

Mendelian inheritance in fish. Qu.

EVOLUTION, HEREDITY, EUGENICS 509

divided up into cells which very early become arranged in two
layers, the outer ectoderm (epiblast) which covers the surface of
the embryo and the inner entoderm (hypoblast) which lines the
interior. Between the ectoderm and the entoderm, a third layer
of cells, the mesoderm (mesoblast), arises, usually coming directly
or indirectly from the entoderm.

The ectoderm gives rise to the epidermis covering the body, the
hair and nails, and to organs derived from the epidermis-nervous
system including the retina, epithelial lining of the mouth and anus,
buccal glands and enamel of the teeth.

The entoderm gives rise to the notochord and the epithelium
lining the alimentary canal and its diverticula-including glands of
the digestive tube, the lungs, bladder, hepatic cells of the liver and
secretory cells of the pancreas.

The mesoderm gives rise to structures lying between the ectoderm
and the entoderm including all connective or supporting tissues
except neuroglia. From it originate striated and most smooth
muscle, blood vessels and lymphatics, peritoneum, skeleton and the
epithelium of the genito-urinary system except the urethra and
part of the bladder.

Theories of Heredity and Evolution. — Hypotheses and theories
of heredity are legion and we shall mention only a few of the older
and less tenable ones before taking up the ones that are believed in
at the present time. The theory of Epigenesis supposed that
development came about through the agency of mysterious external
forces. The theory of Preformation supposed that the germ con-
tained all the parts that were to develop from it. We believe, how-
ever, that the union of the germinal elements gives rise to a new
organism that may have different qualities from the parents. We
recognize the fact that combinations may be produced by the
environment, and that apparently new types may be examples of
reversion and due to the ch7~omatin that has been handed down from
some remote ancestor.

History of the Evolutionary Idea. — Many people have heard so
much of the Darwinian theory of Evolution without getting any
accurate first-hand knowledge of what Darwin said that they are
inclined to believe that Charles Darwin gave us the first idea of
evolution. This is far from the truth, however, since from the time
of the earliest Greeks traditions have been handed down regarding
the origin and development of man.

5IO EVOLUTION, HEREDITY, EUGENICS

The early Greeks and Romans possessed an inborn inquisitive
spirit. They lived on the shores of the Mediterranean where many
interesting natural phenomena were visible daily. Their speculative
inquiry resulted in the formulation of quite definite although fre-
quently erroneous ideas regarding the origin of life, the composition
of matter and the reasons for extinction of some animals while
others survived.

Jhales (624-548 B. C.) is credited by Aristotle with the fol-
lowing beliefs:

I. The earth floats on the water. 1. Water is the material
cause of all things. 3. All things are full of gods; and the magnet
is alive, for it has the power of moving iron.

Thales was the founder of Ionic physical philosophy and there-
fore the founder of Greek philosophy. He discarded the mythical
explanation of things and asserted that a physical element, water,
was the first principle of all things. He was the first to question
the origin of the earth, but believed that God is the mind which
formed all things from water.

Anaximander (611-547 B. C.) suggested the transformation of
aquatic species into terrestrial and the especial adaptation of such
terrestrial forms.

Empedocles (495-345 B. C.) is called the " Father of Evolution,"
because he suggested the possibility of the oj-igtJi of t\\c fittest forms
through chance. He thought that there were four kinds of matter,
fire, air, earth and water, and that these were acted upon by two
opposing forces. Love and Hate. He suggested that the independ-
ent parts of horse and man could fuse to make a Centaur. He was
one of the earliest students of Embryology.

Aristotle (384-322 B. C), the most important of the Greek
philosophers, believed in an internal perfecting tendency. He
postulated a gradation from the mineral to the plant, the plant-like
animal, the lower animals and finally man He said, " Nature
makes only those fit for a purpose and makes those fit for their
several uses." Osborn says,^ " If Aristotle had accepted Empedo-
cles' hypothesis of the origin of the fittest through chance rather
than through design, he would have been the literal prophet of
Darwinism." Aristotle appealed directly to Nature for facts and
stimulated inquiry in anatomy and physiology. As instructor of
Alexander the Great, he secured a subsidy of 800 talents, sufficient

6 Osborn, H. F. 1908. From the Greeks to Darwin. The Macmillan Co.

EVOLUTION, HEREDITY, EUGENICS 511

to support as many as 100 collectors bringing animals and plants
from all over the known world.

Pliny the Elder {i^-'Jf) A. D.) was a Roman who, although of
great learning and an enthusiastic student of Nature, did more than
any of his contemporaries to hiyider the development of the scientific
method and spirit. He prepared 37 volumes of natural history
and published the first cyclopedia. An honest compiler, he per-
petuated much nonsense. Since he was considered an authority
on natural history, his writings turned the minds of people away
from science to books.

From the time of Aristotle to the i6th century, the period of the
Anatomists, Fabricius and Vesalius, anatomy and zoology were at a
standstill.

Galen (130-200 A. D.) was a great Anatomist whose studies on
lower mammals were very carefully made, but who erred in con-
cluding that the human body had the same structure. The writings
of Galen were used as texts, and anatomy was not independently
treated until the field was enriched by the vigorous original work of
Vesalius.

Vesalius (1514-1564 A. D.) published several tables of anatomy
and in 1 543 brought out a work on the Anatomy of the Human Body,
the earliest accurate and authoritative human anatomy.

Studying the human subject, Vesalius raised anatomy to a
degree of accuracy hitherto unknown. Galen, from his studies of
the lower mammals, had taught that the lower jaw of man is divided.
Vesalius showed on the contrary that it is a single bone in man.
Vesalius announced, much to the discomfiture of the theologians^
that man had the same number of ribs as woman. When pressed
too hard, Vesalius said that he would leave the question of an
indestructible " resurrection bone " to be decided by the theologians^
as it was not an anatomical question.

The aim in Biology in the Middle Ages was apparently devoid of
spirit and method. Much of it was in the Medical line. Medical
writers were concerned with healing. They had charms against
disease. The dominant powers thought, even up to the time of
Newton, that the devil possessed the power to give men new ideas.

Nicholas Coperyiicus kept a fearful secret for thirty years, his
idea that the sun and planets do not revolve around the earth, but
that the earth revolves around the sun.

Giordano Bruno was bolder, but after stating a similar belief

512 EVOLUTION, HEREDITY, EUGENICS

he was hunted from one country to another, imprisoned in the
dungeons of the Inquisition at Rome for six years, and finally was
burned alive because he would not recant.

Among the first in the new liberty of the Renaissance was the
great William Haj-vey (i 578-1657). He was graduated from Cam-
bridge and finished his medical education at Padua under the anat-
omist Fabricius. Vesalius, by his studies on the human body and
his observation on the valves of the heart, and Fabricius (1537-
1619), by his studies on the veins of the heart, had paved the way
for Harvey's discovery of the circulation of the blood. Harvey
lectured first on the circulation of the blood in 161 5, completed his
work in 1616, and after years of demonstration before the Royal
College of Physicians finally published his little book on The
Movements of the Heart and of the Blood, in 1628. He established
the fact that the arteries are responsible for the pulse, and that
muscular contraction of the heart causes the circulation of the blood.
He greatly stimulated morphological and physiological work, and
revived the experimental method lost since the Greeks.

John Ray (Wray) (i 628-1 705), a contemporary of Harvey, did
excellent systematic work. He is called the " Father of Modern
Zoology." Ray applied the term species to individuals derived from
similar parents. He noted variations but did not conclude that
they were of constant character.

Just prior to Lamarck, Ray and Linnaeus defined a species^ thus
calling attention to the characteristics of animals and plants. The
idea of the. fixity oi species became the opinion of many biologists as
well as theologians. A few less sheeplike clung to the idea that
species were changeable; and were naturally ripe for the reception
of the evolutionary hypothesis.

Biiffon (1707-1788), while not a contributor to technical scien-
tific literature, was of a philosophical turn and definitely popularized
natural history. In his Histoire Naturelle he set forth the idea of
the gradual production of different types of forms. He noted the ills
of slavery, the presence of rudimentary organs in animals and the fact
that in man a poor quality of food determined degenerative changes.

Linnaeus (1707-1778), a Swede, was the founder of modern,
systematic biologv. He established one principle that is more to his
credit than anything else. He invented Binomial Nomenclature.^

' In 1623, Kaspar Bauhin published a treatise, The Pinax, in which he overthrew the
alphabetical arrangement of plants and started the system of using two names to indi-
cate the plant under consideration.

EVOLUTION, HEREDITY, EUGENICS 513

The names being in Latin, a fixed language, are understood by all
people. Linnaeus was a systematist; Sachs calls him a " classifying,
coordinating, sub-ordinating machine." Sachs states: "Linnaeus'
greatest and most lasting service was in the certainty and precision
which he introduced in the art of describing." He was behind his
own time in Physiology, while his work in Morphology was super-
ficial.

Erasmus Darwin (1731-1802), the grandfather of Charles Dar-
win, was born in England. He was a distinguished physician,
philosopher and poet. Osborn called him the Poet of Evolution.
He asked questions directly from Nature. " Do some of the genera
perish by increased power of the enemies.? " " Do some animals
change in their nature .? " " Why do plants have poisonous juices ? "
" Many plants have arms, spines and stings for protection."

His research and thought helped Charles Darwin. He perceived
the significance of color for protection. "Frogs vary color accord-
ing to environment." He noticed the adaptation o{ limbs to en-
vironment. He saw that the strong males propagate the species and
believed a little in the " Survival of the Fittest." With E. Darwin's
final work in 1802 culminated the ideas of the time. He had not
formulated any theory. He become the pioneer, setting up the
landmarks which served as the guides for subsequent investigations.

Jeanne Baptiste Antoine de Monet — Chevalier de Lamarck (1744-
1829). — The name of Lamarck is intimately associated with x}lvq first
formulated theory of Evolution. He was a contemporary of Eras-
mus Darwin. Many of the views of Lamarck had been anticipated
by E. Darwin. Lamarck advanced a theory in 1809 that accounted
for variations by supposing that environment brought them about
directly or else through the efforts made by the animal to adjust
itself to its environment. Lamarck's theory perforce admitted
the transmission of acquired characters.

Haeckel says: " To Lamarck will always belong the glory of
having worked out for the first time the theory of descent as an
independent scientific theory of the first order and as the Philo-
sophical foundation of the whole science of Biology."

Lamarck's Four Laws of Evolution. —

I. Life by its proper forces continues to increase the volume of
every body which possesses it as well as to increase the size of
its parts up to as great limits as it can bring itself.

514 EVOLUTION, HEREDITY, EUGENICS

2. The production of the new organ or part in the animal body-

results from the supervention of a new need or want which
continues to be felt and of a new movement which this need
initiates and causes to continue.

3. The development of organs and their force or power of action

are always in direct relation to the employment of those
organs. (Law of use.)

4. All that has been acquired, impressed upon or altered in the

organization of individuals during the course of their life is
conserved by the generation and transmitted to new indi-
viduals which have descended from those which have sur-
vived these changes.

Following the death of Lamarck in 1829, the theory of Evolution
was forgotten for a time and ceased to impress the scientific world.
Erasmus Darwin's views were not revived until the time of his
grandson, Charles Darwin.

Cuvier (1769-1832), the founder of Modern Paleontology, was a
keen student of anatomy, beginning with Invertebrates. He is
termed the founder of Comparative Anatomy, as he established a
system of classification based on the comparative' anatomy of
internal organization instead of the superficial external characteris-
tics employed by his predecessors. He defended his erroneous
" cataclysm theory," that periodically a great revolution destroyed
all life on the earth and that a new world of unchangeable species
arose. This theory was later, in 1832, shown to be false by Lyell,
in his " Principles of Geology."

Charles Darwin (1809-18 8 2). — According to Charles Dar.win, in
1858, chance variations afford the opportunity for the factor of
natural selection to pick out those best adapted to survive in the
tremendous struggle for existence and the propagation of species.

Darwin took variations for granted. His long observations,
together with the suggestive work of Malthus on Population, con-
vinced him of the tendency towards over-production in plants and
animals. This, he noted, led to a struggle for existence. He pointed
out the fact that struggle for existence might be between fellows,
when stags fight stags in the clearing, or between foes as in the case
of the mongoose and the snake; or finally it might be a struggle with
fate, as in the case of " two canine animals which in time of dearth
struggle with each other which shall get food and live."

EVOLUTION, HEREDITY, EUGENICS 515

The three processes, overproduction, struggle for existence and
survival of the fittest, result in Natural Selection. Favorable adapta-
tions enable the fit to live while the others perish. Tied up with
these ideas was the one regarding sexual selection, in which Darwin
attempted to show that in the birds, for example, secondary
sexual characters such as brilliant plumage and beautiful songs
attracted the female, who selected or chose the male. This last
factor has been much debated, but we cannot gainsay the very
important point that the healthy and best adapted forms, able to
survive, will be able to reproduce. Certainly vigor exhibits itself
in brighter color and purposeful activity.

Darwin wrote out a sketch of his theory in 1842, and in 1844 gave
his completed theoretical conclusions, showing the paper to his
friends Lyell and Hooker. But the public announcement of his
chief contribution was postponed until 1858, when he shared with
A. R. Wallace the credit for the idea of " evolution " from the
Natural Selection of those j'?/ to survive.

A. R. Wallace (i 822-1913), another Englishman, was so en-
thusiastic after reading Darwin's Journal of the Beagle Voyage in
1845 ^hat he embarked in 1848 on an exploration of the Amazon
and Negro Rivers lasting 4 years. Later, after he had explored in
the Malay Archipelago, he prepared while at Sarawak (1855) a
paper in which he concluded that every species that had come into
existence in Nature was related to a species that preceded it. He,
like Charles Darwin, read Malthus, On Population, and in February,
1858, he sent Darwin a short paper entitled: "The tendency of
varieties to depart from the original type."

Darwin at first thought most unselfishly to present Wallace's
paper to the Linnaean Society without comment. His friends,
including Dr. J. D. Hooker and Sir Charles Lyell, persuaded him
that after 20 years of careful observation had resulted in the for-
mulation of theories backed by many facts unmarshalled by Wallace,
the correct procedure was to present his own views in a paper to be
read at the same symposium.

So far as the oft-quoted idea of the survival of the fit, later para-
phrased into Nietzsche's term the " super-man," is concerned, we
have no finer or more noble instance of the humanity of man to man
than that of Darwin and Wallace, the co-discoverers and crystal-
lizers of the principle of Evolution, vying with each other over the

5i6 EVOLUTION, HEREDITY, EUGENICS

privilege of yielding to the other man the honor and glory of the
public presentation of such a world-shaking hypothesis.

Accordingly, in the spring of 1858, Sir Charles Lyell and Dr.
J. D. Hooker communicated to the Linnaean Society Wallace's
paper just mentioned and brief extracts from Darwin's unpublished
works together with an abstract of a letter to Professor Asa Gray.
The two papers, with the many striking examples supporting Dar-
win's theory, stirred the scientific world.

Polemics were issued by the theologians and more attention was
thus focused than otherwise. The result was that when Darwin
published his book in 1859, the first edition was sold out in a day.
So bitter was the fight waged by prominent theologians that it
took the most strenuous efforts of T. H. Huxley (i 825-1 895), the
" bull-dog of Darwinism," and of other less militant scientists to
turn the tide.

When the average person thinks of " evolution " he is likely to
confine himself to garbled statements of the Darwinian theory.
Recently, when Bateson of England in a public address mentioned
the fact that modern Biologists do not accept in all details Charles
Darwin's theory, the opponents of evolution seized upon the state-
ment and announced that the great biologist denied evolution.
Although all biologists do not agree about the method of evolution
they believe in it as an established law.

A recent paper ^ by Henry Fairfield Osborn, of the American
Museum of Natural History, points out that man has an age-old
history. Man, we find from the discoveries of archeologists, has
always had a religion and a soul. He has always worshipped and
revered something, except of course during his own period of
adolescent outbreak.

Biologists, like other men of science, are neither atheists nor
iconoclastic in their attitude toward religion. As the distinguished
Sir William Bragg said (1928) in an address before the British Asso-
ciation for the Advancement of Science, " Science is not setting forth
to destroy the soul, but to keep body and soul together."

Clark^s Zo'dgenesis Theory. — A. H. Clark of the Smithsonian
Institution has formulated a most stimulating theory which he has
been kind enough to summarize for this text.

8 H. F. Osborn. 1928. Recent discoveries relating to the origin and antiquity of
man. Science, vol. 65, no. 1690, pp. 481-488.

EVOLUTION, HEREDITY, EUGENICS 517

"While within each of the major animal groups or phyla the inter-
relationships of the various included types as they appear in successive
geological horizons are such that they may be represented in the form of a
tree — the so-called phylogenetic tree — there is no real evidence, paleonto-
logical, embryological or structural, that any of the phyla were derived
from any of the others, although all of them must have been derived from
a primitive single cell. Each of the phyla represents a special and definite
structural complex basically different from the structural complex repre-
sented by any other.

"The protozoans differ from all other groups in the complete separa-
tion of the cells after division. The sponges are unique in the more or
less irregular adhesion of the cells after division in the early embryonic
stages. All other groups pass through a gastrula or its equivalent, and
the gastrula is the last stage common to them all.

"It is therefore assumed that, so far as the major groups of phyla
are concerned, evolution was a more or less simultaneous process of
radiation from the gastrula stage, and that the phyla never were con-
nected by intermediate types any more closely than they are at present.

"This conclusion agrees with the determined facts of paleontology
and embryology, and furthermore accords with our interpretation of
conditions on the earth at and subsequent to the first appearance of life."

Significance of the Darwinian Theory. — We owe to Darwin the
first successful vindication of the evolution idea. It was not his
own, nor was he its first champion, yet we think of Darwin and the
Doctrine of Descent together. The central idea of evolution is
that the present is the child of the past and the parent of the future.
It is the idea of progressive change from phase to phase without
loss of continuity. Crampton says, " The Origin of Species has
proved a veritable Magna Charta of Intellectual liberties, for as no
other single document before or since it has released the thoughts of
man from the trammels of unreason, conservatism and dogma."

Darwin's Pangenesis Theory. — Charles Darwin is responsible
also for a theory of inheritance units. He supposed that each cell
of the body throws off little particles which he called gemmules^
which are somehow gathered together in the germ cells. When these
develop, the gemmules reproduce in the body of the new individual
the characters of these cells of the parent from which they were
derived. With this the transmission of acquired characters is per-
fectly natural. The theory is called the pangenesis theory because
it assumes that all parental somatic cells are concerned in the for-
mation of the new individual. It is interesting to note that in spite

51 8 EVOLUTION, HEREDITY, EUGENICS

of the fact that Charles Darwin, like many others, ridiculed La-
marck's laws, particularly the one that suggested the inheritance of
acquired characters which had arisen through a new need, his pan-
genesis theory attempts to explain the inheritance of acquired
characters.

As we have not yet determined the method by which somatic
characters may be transmitted to the germ-cells, we cannot accept
this theory. Our knowledge of the importance of biochemical
systems such as the horrnones may increase to a point where it will
in time be possible to accept a modified gemmule theory.

A. Weismann (1834-19 14) in his book, The Germplasm, pub-
lished in 1893, denied the formation of the germplasm from the body
tissues of the individual, and maintained that its sole origin was
from the germplasm of the parent of the individual. The germplasm,
according to Weismann, is handed on from one individual to the
next descendant unchanged by environment. Since the body cells
are not inherited, there is no possibility of the inheritance of acquired
characters.

His theory is that sexual reproduction ^ is a mechanism for dou-
bling the possible variations in the offspring. In such permutations
and combinations of the qualities of the uniting germplasm, chance
and the factor of natural selection may both become effective.

He believed that the germplasm consists of hereditary units
called detey-minants^ and that still smaller units called biophors are
made up finally of molecules and atoms. As the determinants are
grouped together to form granules of chromatin {idants) making
up the chromosomes {ids), it is quite evident that the microscope
cannot be used to study these units.

Unknown Units. — Other biologists have suggested ultramicro-
scopic units similar to the biophors and determinants of Weismann
and the gemmules of Darwin. De Vries called them pangenes;
Spencer named them physiological units; Galton, stirps; Hertwig,
idioblasts; Naegeli, micellar strands; and Weisner, plasomes. We
accept the fact that there are units which like chemical radicals are
always found united, yet preserve their individuality in different
combinations. How these ultramicroscopic units behave we are
still conjecturing.

Francis Galton (1822-1911). — A law of heredity formulated by

' Amphimixis is biparental parentage. (See page 125.)

EVOLUTION, HEREDITY, EUGENICS 519

Francis Galton in 1889 seemed to some to satisfy the theoretical
requirements.

Gallon's Law of Ancestral Inheritance in essence was that the
two parents between them contribute ^ of each inherited faculty,
the grandparents together contribute ^, the great grandparents
1/8. (The individual, i = ^ plus yi plus 1/8 plus 1/16 and so on.)
Since this theory does not apply to individual cases and takes no
account of prepotencies or the domination of the characters of one
parent, it is not accepted.

Gregor Mendel (i 822-1 884). — The Austrian monk, Gregor
Mendel, having worked for eight years with bees and garden peas,
in 1865 published an account of his work in the Proceedings of the
Natural History Society of Brunn, Moravia, but this was over-
looked until 1900 when De Vries, Correns and Tschermak, inde-
pendently arriving at similar conclusions, brought the earlier work
to light. In 1902, Bateson, an Englishman, pointed out its great
importance and since then we have been much interested in experi-
ments which seem to substantiate the early conclusions and carry
the work on to a point where it is being applied in practical work
with cattle, poultry and plants.

MendeFs First Law: The Law of Dominance. — When mating
occurs between two animals or plants unlike with reference to a
single unit character the " hybrid-character resembles one of the
parent forms so closely that the other either escapes observation
completely or cannot be detected with certainty." The character
of one parent only thus exhibited is called " dominant " while the
other latent character is called " recessive."

If the dominant determiner is absent, and the recessive deter-
miner is duplicated, the recessive character is exhibited. Thus we
may have a " dominance of recessiveness."

When the hybrid offspring of such a cross are in turn crossed
with each other, it is found that 25 per cent will be like the dominant
grandparent, 25 per cent like the recessive grandparent, and 50
per cent like the parents that resemble the dominant grandparent.

We have therefore by crossing two DR's: yi DD plus yi DR

plus X RR.

When a pure dominant is crossed with a mixed dominant
recessive, the offspring will all show the dominant character, though
of course one-half of them are DR's. DD X DR equals 2 DD plus
2 D (R). The DD's are pure and the D (R) is like any other hybrid

520

EVOLUTION, HEREDITY, EUGENICS

and yields the i : 2 : i offspring if two are hybridized. When the
recessive is crossed with a mixed DR we get 2 D (R) plus 2 RR.

Mendelian Inheritance
(Garden Peas)

Dominant
R. round
Y. yellow
T. tall

Recessive

W. wrinkled
G. green
D. dwarf

Pure dominant crossed with pure recessive yields DR hybrids.

Monohybrids.—R X W equals first filial generation: R (W).

Representing the hybridization as followed by crosses of male
and female germ cells bearing the combined R (W) we have by
Punnett's method of squares the following Monohybrids:

Male

R

W

R

R

R

R

W

Female

W

W

W

R

W

F2 generation

This equals RR plus 2 R (W) plus WW.
Likewise DR X DD is expressed:

R R

X = 2 RR plus 2 RW.
R W

Again, dominant-recessive DR X pure-recessive RR equals 2 DR
plus 2 RR as:

R W

X =2 RW plus 2 WW.

w w

Complete dominance is rare, however, as Mendel discovered in the
case of certain peculiar hybrid forms.

{a) The law of dominance is not of universal application.
Mendel found this true in crossing different heights of peas.

{b) There may be an intensification of the characters of one
parent. Brown seeded peas may be darker than the parents.

EVOLUTION, HEREDITY, EUGENICS 521

(c) The cross bred may have a character entirely different from
either parent. The hybrid may possess its own character.

In the case of the Blue Andalusian fowl we have a good example.
The parents are: Dominant — black; recessive — white with black
splashes. The hybrid is blue. When two hybrids are crossed the
offspring are found to be )4 black; ^ splashed white; and }4 blue.

MendeVs Seco7id Law: The Law of Segregation or Puj-'ity of
Gametes^ Called the Law of the Splitting of Hybrids. — Both body
cells and germ cells of the Fi parent, before reduction divisions,
contain the determiners (genes) of both alternative characters and
are hybrid in character, but during maturation the alternative
genes (allelomorphs) are segregated, and we have the law that the
hybrid, whatever its character, produces ripe germ cells which
bear only the pure characters of one parent or the other. A gamete
then is never hybrid with reference to any single character.

Dihybrids. — The usual Mendelian proportion for crosses where
the parents have two pairs of characteristics each is: 9 : 3 : 3 : i.

YR crossed with GW results in offspring in the (first filial)
generation, YR (GW). The germ cells are of four types, excluding
the obviously impossible RW and YG,'" and may be arranged in
squares to indicate the crossing:

Sperm gametes YR: YW: GR: GW:
Egg gametes YR: YW: GR: GW:

YR YR YR YR
YR YW GR GW

YW YW YW YW
YR YW GR GW

GR GR GR GR
YR YW GR GW

GW GW GW GW
YR YW GR GW

While there are sixteen possible combinations, called genotypes,
we must note that recessive characters are latent in the presence of
dominant, so that we have but four types of peas so far as appearance
goes. These are called phenotypes (see page 538).

The possible combinations, when added together, result in 9 YR
plus 3 YW plus 3 GR plus I GW (YWGR is really a YR, and so on).

1" Every germ cell is pure as regards any given character. (See Second Law.)

522 EVOLUTION, HEREDITY, EUGENICS

There may also be a masking of characters. If gray rabbits
are crossed with albinos, the first filial generation are all gray. The
second filial generation become 9 gray, plus 3 black, plus 4 albinos,
(i) Pigmentation is A and albinism is a.^^ (2) Gray is B and black is
b. When these are crossed we get a gray hybrid.

The gray hybrids follow the rule for dihybrids, resulting in 9
AB (gray), plus 3 Ab (black), plus 3 aB, plus i ab (4 albinos). The
albinos are not all the same kind, however, for we have: i aBaB,
2 aBab and i abab.

By crossing each type with a black we get aBaB X Ab — AB
all gray; aBab X Ab — i AB gray plus i Ab black; abab X Ab —
Ab all black.

Trihybrids have three pairs of independently segregating char-
acters.

RYT X WGD produces the hybrid RYT (WGD).

We must eliminate RW, YG and TD as impossible of exhibition
(Second Law), and then we have the following combinations for
male and female germ cells: RYT RYD RGT RGD WYT WYD
WGT WGD.

Placing the male germ cells in a horizontal row and the female
germ cells in a vertical row and superimposing the squares we may
secure 8X8 squares of possible matings or sixty-four matings.

Results: 27 RYT plus 9 RYD plus 9 RGT plus 9 WYT plus 3
RGD plus 3 WYD plus 3 WGT plus i WGD.

Mender s Third Law: The Law of Independent Assortment of
Different Allelomorphs. — " The relation of each pair of different
characters in hybrid union is independent of the other differences
in the two original parental stocks."

This law becomes apparent when we try to follow the inheritance
of more than one character at the same time. Modern investigators
believe that the genes that show independent assortment are located
in different chromosomes (see page 500).

Mendel's Fourth Law: The Law of Recombination. — Mendel
stated that " the constant characters which appear in the several
varieties of a group of plants may be obtained in all the associations
which are possible according to the mathematical laws of combina-
tion." We find that the genes occur in all possible combinations
according to the law of chance.

1^ Where many factors are involved, it is desirable to use R for the dominant char-
acter and r for the recessive, as is done in the case of the discussion of rabbits herewith.

EVOLUTION, HEREDITY, EUGENICS

5^3

Examples of Mendelian Ikheritance in Man

From E. G. Conklin, Heredity and Environment, 1920, pp. :

permission of the Princeton University Press.]

)

Domitjant

Recessive

Hair

curly

straight

dark

light to red

Eye color

brown

blue

Skin color

dark

light

normally pigmented

albinism

Countenance

thick lower lip and prominent chin

normal

Temperament

nervous

phlegmatic

Intellectual capacity

average

very great or very small

General size

normal size

dwarfish

dwarfs with short limbs but normal bodies

normal

and heads

Brachydactyly: short fingers and toes

normal

Syndactyly: webbed fingers and toes

normal

Polydactyly: supernumerary fingers and toes

normal

Skin

keratosis — thickening

normal

epidermolysis — blister form

normal

hypotrichosis — hairlessness and lack of

normal

teeth

Nervous system

normal condition

epilepsy

feeblemindedness

insanity

alcoholism

criminality

hysteria

chorea

St. Vitus' dance

multiple sclerosis

Huntington's chorea

normal

Eyes

cataract

normal

glaucoma

normal

116-118. (By

Ears

normal
normal

deafmutism

otosclerosis (rigidity of tympanum and
hardness of hearing)

524 EVOLUTION, HEREDITY, EUGENICS

References

CoNKLiN, E. G. Heredity and Environment. Princeton Univ. Press.

Metcalf, M. M. 1911. Organic Evolution. Macmillan Co.

Morgan, T. H. 1916. A Critique of the Theory of Evolution. Prince-
ton Univ. Press,

Newman, H. H. 1925. Evolution, Genetics and Eugenics. Univ. of
Chicago Press.

Walter, H. E. 1930. Genetics. Revised edition. Macmillan Co.

De lories' ''Mutations-Theories— In 1901, Hugo De Vries
(1848- ) of Holland announced that his studies of inheritance in
the evening primrose, Oenothera Lamarckiana, had led him to con-
clude that new species arose suddenly by what he called mutation.
These mutants or "sports" explained the origin of a new species in
nature. Some mutants were retrogressive and others progressive.
Later work by R. R. Gates showed that from the cytological basis
the new types came about through analysis of the chromatin. The
appearance of a new type was to be explained by a change in the
chromatin.

Some of the workers with the fruit fly, Drosophila, once sug-
gested that the so-called mutants of De Vries are the emergence of
factors recessive in the ancestral stock and brought out by the
favorable cross. The production of mutations by high temperature,
x-rays, and other physical agents (see page 540) will give new
impetus to cytological correlations.

Examples of mutation include the celebrated Ancon sheep,
which was short legged, many instances of taillessness and horn-
lessness in cattle, and supernumerary or reduced numbers of digits
in various animals.

If we can eventually control the appearance or disappearance of
factors in the germplasm, we will produce an experimental evolution.
If not, we must confine ourselves to selection and to those influences
of environment that tend to bring out the qualities desired.

The Origin of New Species According to Lamarck, C. Darwin,
A. Weismann, Mendel, and De Vries 12

Lamarck. — New species result from variations induced by use and
disuse. Variations are inherited directly or improved in succeeding
generations.

12 Modified from Locy, Biology and Its Makers.

EVOLUTION, HEREDITY, EUGENICS 525

C. Darwin. — Variations assumed. Variations of use are perpetuated
by inheritance. The Jit survive and propagate. Each cell of the body
sends off minute gemmules which enter the germ cells and transmit changes
that have taken place in the individual. (This really admits the inher-
itance of acquired characters.)

Weismann. — Variations are due to permutations and combinations of
the germplasm. Germinal selection takes place in the union of the germ
cells. Germplasm has an unbroken continuity with an extremely complex
organization. Body cells are not inherited.

Mendel. — New species are due to new combinations of chromatin.
Dominance and recessiveness are always to be considered.

Tie Fries. — New species are due to sudden mutations or "sports."
Mutations are sudden variations that breed true. De Vries says, a
mutant is "a change of wide amplitude which tends to be stable because
it involves acquisition of a new unit by the germplasm, but which is
necessarily stable only when the individual possessing it mates with a
similar individual." It has been suggested that mutations may occur
through the addition or subtraction of single characters.

Evidences for Evolution. Paleontology. — In studying the strata
of the earth's crust we find that there is a gradual progression from
types with primitive organization to the highly developed. Many-
groups of animals and plants reached the climax of specialization
at relatively early geologic periods and became extinct.

The evolution of vertebrate classes is more satisfactorily shown
than that of any other group, probably because they represent the
latest phylum to evolve and most of their history coincides with the
period within which fossils are known, while most of the inverte-
brate phyla had already undergone more than half of their evolution
at the time when the earliest fossil remains were deposited.

Fossils Classified. Class i. — Actual remains of recently extinct
animals and plants. («) In Arctic ice — the mammoth, {h) Insects
preserved in resin-amber, (f) MolJusk shells, teeth of sharks, pieces
of buried logs and bones of animals buried in asphalt lakes and peat
bogs have been found in well-preserved condition.

Class 2. Petrified fossils., seen best in plants. Class j. Casts
and impressions. These are the impresses of soft-bodied animals
left in mud which later solidified. The celebrated Pompeian dog
is a striking example. The most remarkable are found in the oily
shales of British Columbia. Even soft invertebrates are found in
casts.

526

EVOLUTION, HEREDITY, EUGENICS

EVOLUTION, HEREDITY, EUGENICS

527

The pedigree of the horse is the best known. Paleontological
evidence is complete for the evolution of the horse from a five-toed
ancestor.'^ The pedigrees of the camel and the elephant are both
worked out quite satisfactorily also. The pedigree of man has been
worked back successfully for many centuries with accompanying
flint weapons and implements.

Man

BONES or HIND LEGS

MonKey

Fig. 264. Hind limb bones of man, monkey, dog, sheep and horse. (After LeConte.

Courtesy of Amer. Mus. of Nat. Hist.)

Evidence from Comparative Anatomy. — If we accept the Prin-
ciple of Evolution it is easy to explain the similarity in make up of
the wing of the bird, the foreleg of the seal and the arm of man, all
of which are " homologous " structures. Likewise, we can explain
the fact that man has 180 vestigial structures which now have no
significance to him. The muscles of the human external ear and the
subcutaneous muscles in the forehead and scalp persist, although
useless.

The nearest allies of man in the quadrumanous species lack a tail.
Man has one at 6 weeks embryonic life, longer than the hinder
limbs. Rarely, a human infant is born with a tail. The tail
muscles persist as vestiges. The vermiform appendix of the cecum,

13 Consult W. D. Matthew, The evolution of the horse. Quart. Rev. of Biol., vol.
I, April, 1926.

528

EVOLUTION, HEREDITY, EUGENICS

functional in the herbivores, is a menace to the health of man. A
little blunt point projects from the inwardly folded margin or helix
of the ear. It is the vestige of the point in lower animals. A tiny
third eyelid is still found in man. Adult man has rudimentary hairs
over most parts of the body. At the sixth fetal month the fetus
has long hair over the body — " lanugo " — which in most cases is
shed before birth.

Evidence from Blood Tests. Precipitation Method. — Freshly
drawn human blood is allowed to clot, then the serum drawn away.
Small quantities of the serum are injected at intervals of one or two

days into the veins of a rabbit and
cause the formation in the rabbit's
blood of an antibody, analogous to
antitoxin obtained from a horse after
injection of diphtheria virus. After
the last injection, the rabbit is al-
lowed to live several days, then is
bled and the serum drained off and
preserved. This is " anti-human "
serum and is a delicate test for hu-
man blood, not only when it is fresh,
but even when in the form of old
and dried blood stains. Into an
" unknown " solution of blood, a
few drops of the anti-human serum
are passed, and, if the stains are hu-
man blood, a white precipitate is
formed and thrown down, but if
the stains are of some domestic
animal — pig, sheep or fowl — no such
reaction (precipitation) occurs. This
test is used in the detection of crime. Nuttall and others have
shown that if sufficiently strong solutions be used and time enough
be allowed, a relationship between the blood of all mammals is
made evident.

Nuttall says: " The evidence which I published upon my tests
with precipitins shows that reactions obtained with the blood of
Simiidae (Manlike apes) closely resemble those obtained with
human blood, the bloods of Cercopithecidae (Old World monkeys)
came next, followed by those of Cebidae and Hapalidae (New World

F^MliK

Fig. 265. Vestigial pelvic girdle
and hind limbs of the python.
(From Romanes, Darwin and After
Darwin. Courtesy of Open Court
Publishing Co.)

EVOLUTION, HEREDITY, EUGENICS

529

monkeys and marmosets) which gave but slight reactions with
antihuman serum, whilst the blood of Lemuroidea gave no indication
of blood relationship."

Evidence from Embryology. — All animals, even man, begin as a
single cell, and develop in a parallel manner for a short time. We
have considerable evidence to support the Recapitulation Theory

Turtle N.

C?o/eus

F'rom inside

Eog/e

f^t-om ins'ide

Young
Duoonq ^

Hor^e N.j.^

^- Otori'a
)■ SeQ Lion

Ape

P/ica,
Semilunari-s

Man .Man

Fig. 266. Illustrations of the nictitating membrane in the various animals. (From
Romanes, Darwin and After Darwin. Courtesy of Open Court Pub. Co.)

530

EVOLUTION, HEREDITY, EUGENICS

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EVOLUTION, HEREDITY, EUGENICS 531

that the history of the individual is a recapitulation of the history
of the race, but we cannot escape the observation that there are
notable differences, each species introducing its own specializations.

Evidence from Classification. — The very assumption underlying
classification is that the closest fundamental similarities between
animals are found in those forms most closely related, and that the
greatest differences are found in those forms that are distantly
related. That we can place the animal kingdom in an orderly
progressive series is an indication of such a thing as Evolution.

Evidence from Geographic Distribution. — The evolutionary
theory furnishes an explanation of the phenomena of distribution
of animals and plants. A species arises at one place and spreads out
over large areas, becoming modified as it goes, and new species are
formed from old through modification after isolation from the parent
stock. We find cosmopolitan groups, those with the widest dis-
tribution being the ones to whom no barriers are sufficient to check
migration; such as parasitic worms carried by man and other ani-
mals; and birds able to span large bodies of water (Newman).
Restricted groups are those to which barriers are readily set up, and
are frequently the only remnants of a once successful fauna or flora.
Again the faunas and floras of continental islands are what we should
expect on the basis of former land connection with the nearest
continent, since they are like those of the nearest mainland and
include types most readily blown there by wind or carried on floating
debris.

Chief Sources of the Foregoing Summary

Darwin, C. Origin of Species. D. Appleton and Co.

Newman, H. H. 1925. Evolution, Genetics and Eugenics. U. of Chi.

Press.
NuTTALL, G. H. F. Blood Immunity and Blood Relationship. Camb.

Univ. Press.
Scott, W. B. 191 i. The Theory of Evolution. Macmillan Co.
Thomson, J. A. 1909. Darwinism and Human Life. Henry Holt &

Co.

Sex Determination, — The theories of sex determination afford an
opportunity to test the relative importance of the chromosomes as
opposed to environmental influence. Since there are but two sexes,
it must be conceded at the start that any theory of sex determination
will appear to be right, one-half of the time.

^2^ EVOLUTION, HEREDITY, EUGENICS

One of the earliest known theories of sex determination, first put
forth by Aristotle, is based on the alternate functioning of the ovaries
and on evidence from pregnancies after one ovary has been removed.
The right ovary is supposed to produce eggs that develop into males.
Experiments with mammals and statistics from hospitals prove this
theory worthless. The age and vigor of the parents have also been
shown to be of no importance.

In cattle, Thury, Russell and later Raymond Pearl have pro-
duced considerable evidence to prove that matings which take place
at the beginning of heat produce a preponderance oi females, while
those taking place in the period of heat produce males. In pigeons
the eggs produced in the early part of the breeding season will
develop into males, while those from the latter part of the breeding
season develop \x\to females. Whitman and Riddle have brought
out this fact most clearly.

Riddle believes that sex is a quantitative modifiable character.
The males have a higher rate of metabolism, than the females. He
concludes ^'^ that from the egg-stage onward through embryonic and
adult life the oxidizing powers of the male tend to exceed those of
the female, and that it is this tendency which ultimately decides
whether male or female shall develop. According to Riddle the two
diverse chromosome combinations which ordinarily determine sex
really accomplish this by thus providing an " internal genetic pull
toward a lower or a higher metabolic rate." This genetic tendency
can, however, be overridden by means which specifically establish
an opposed rate of metabolism over prolonged periods, particularly
over early and critical periods in the differentiation of sex.

As Riddle has pointed out (Science, 1927. vol. 65, page 139),
Goldschmidt (Science, 1926, n. s., vol. 64, page 299) has made no
reference to the earlier work of Riddle when (Science, 191 2, n. s.,
vol. 35, page 462) he first gave evidence for his quantitative theory
of sex. Riddle gladly credits Goldschmidt with the discovery that
the genes influencing sexuality in the autosomes were not of equal
potency in certain races of moths (see Goldschmidt's Enzyme
Theory, page 534).

Certain Germans, including Pryll, Zolner, Ismer and Siegel,
published papers during the Great War, indicating that earlier ova
develop into males while the later, more mature and possibly better

1^ Riddle, O. 1916. Sex control and known correlations in pigeons. Amer. Nat.,
vol. 50, pp. 385-410.

EVOLUTION, HEREDITY, EUGENICS S33

nourished ova produce females. Statistical studies negative this
hypothesis and indicate that the sexes are. about evenly distributed
regardless of the lunar cycle.

Schenck suggested that the ripe eggs develop into males and the
unripe into females. He fed women nitrogenous food, induced
complete metabolism and males appeared, part of the time, of
course. In wasps and other insects it is well known that an abun-
dance of food induces greater numbers of females. In bees the
queen is procured by special " bee bread." H. D. King has shown
that neither food nor temperature is a factor in sex determination
in the frog.

In Rotifers, D. D. Whitney and others have shown that a larger
number of male grandchildren are produced by feeding the female a
green unicellular organism, while if she is fed a colorless organism,
the offspring are practically all females. ShuU and Ladoff showed
that oxygen excess produced males but Whitney contended that
oxygen was not a factor.

Robinson advanced the theory that the adrenals determine the
sex of the offspring, maintaining that an excess of adrenalin pro-
duces males, and that a smaller amount causes the development of
females. He based his conclusions on fifty clinical cases. Experi-
ments do not prove his theory, however.

That there is an intimate relation between the genital glands and
the adrenals, the pituitary and the thyroids, cannot be denied. To
prove a specific physiological basis for the generally accepted action
of the chromosomes is a most difficult problem.

The Accessory or Sex Determining Chromosome. ^^ — In 1891,
Henking found in the Hemipteran Pyrrhocoris a "peculiar chroma-
tin-element " which passes undivided to one pole while the other
eleven chromosomes are equally divided. He labeled it "X," and
finally termed it a "nucleolus."

In 1901, McClung recognized the chromatin nucleolus of Henk-
ing as a chromosome which he traced (in the grasshopper Xiphidiu?n)
into the first spermatocyte, where it passed undivided to one pole,
then divided in the second spermatocyte, giving rise to two types of
spermatozoa. McClung was the first to suggest the bearing of two
kinds of spermatozoa on the determination of sex, and in 1902 he
called the sex chromosome the " accessory chromosome."

15 Consult General Cytology, Chicago Press, 1924, and Wilson, E. B., The Cell,
1925, Macmillan and Co.

534 EVOLUTION, HEREDITY, EUGENICS

Miss N. M. Stevens and E. B. Wilson, working independently
on insects, and Boveri, working on sea-urchins, found that all of the
eggs at maturity have one extra or accessory or so-called " X-
chromosome." The sperms are of two types, one-half containing
the X-chromosome and the other half lacking it. Wilson clarified
matters in 1905, showing that the female has in each of her body cells
one more chromosome than the male, her chromosome groups con-
taining two X-chromosomes, and those of the male containing but
one^ while other chromosomes are distributed identically in the two

sexes.

Following some earlier work by others, faulty in technique. Von
Wini water demonstrated in 191 2 that in man there are 48 chromo-
somes in the female and 47 in the male. Oogenesis results in the
appearance of 24 chromosomes in each matured egg (23 plus X);
but after spermatogenesis, one-half the sperms have 23 plus X, and
the other half have only 23. The egg fertilized by the sperm with
the X-chromosome develops into a female, while the other type of
sperm without an accessory chromosome produces a male at fertili-
zation. Painter has also found the Y-chromosome, and concludes
that the male has 46 plus X, plus Y; and the female has 46 plus 2 X.
The Y-chromosome has apparently no significance except as the
bearer of somatic characters.

Goldschmidfs Enzyme Theory of Sex Determination. — Gold-
schmidt has attempted to reconcile the fact that the gonads pro-
duce hormones which apparently under certain circumstances are
able to override the influence of the chromosome constitution,
producing intersexes or even reversing the sex completely.

Goldschmidt suggests that the X-chromosome carries the gene
(factor) of an enzyme-producing character which determines female-
ness, while the Y-chromosome, or possibly the cytoplasm, carries
the gene of a male-determining enzyme. In the fertilized egg with
two X-chromosomes, the female enzyme is present in double
quantity and produces a female. If but one X-chromosome is
present, the cytoplasm (or possibly the Y-chromosome) produces an
enzyme which " overpowers " the female producer and a male
results. Goldschmidt and others have stressed the point that the
variability of intersexual types depends on the degree of strength
of the two sex-producing factors or enzymes, these varying in speed
of action. (See Goldschmidt, R., 1916, Science, n. s., vol. 43, p. 98.)

EVOLUTION, HEREDITY, EUGENICS S3S

Sex-Linked Characters. — Along with the accessory chromosome
go certain " sex-linked " characters. Morgan has shown that there
are more than loo such characters in the fruit fly. In man, we
know of five which appear in the male when simplex and in the
female when duplex with reference to accessory chromosomes.
These are Gowers muscular atrophy, haemofhilia (slow clotting of
blood), color blindness or Daltonism (red from green), nightblindness^
and neuritis optica (progressive atrophy of the optic nerve). These
sex-linked characters require two determiners for t\\Q female, and but
one for their appearance in the male. It is interesting to recall the
fact that Charles Darwin long ago noted that male albino cats with
blue eyes are usually deaf.

Identical vs. Fraternal Twins. — It has long been known that
there are two kinds of twins, one type like ordinary sisters, brothers,
or brother and sister, coming from different eggs, and c^W^d fraternal
twins; while the other kind, produced by the division of one egg cell,
always appear to have the same characteristics and are always of
the same sex. These last are called identical twins and furnish
evidence that goes far towards substantiating the theory of sex
determination before cell division. Likewise, studies on the arma-
dillo, which produces from one ovum four identical offspring of the
same sex, would seem to clinch the matter as to the time of sex
determination.

Earlier workers were wont to rely upon the types of fetal mem-
branes in determining the origin of twins. The assumption that
all monochorional twins are monozygotic and all dichorial twins are
dizygotic has met with considerable opposition, since several remark-
able exceptions to the rule have been reported. In a paper by
Curtius (1930), three strikingly identical sets of dichorial twins are
reported as monozygotic. In these cases, it is probable that the
twinning took place during early cleavage, possibly as far back as
the four-cell or the eight-cell stage. It could not have occurred at
the two-cell stage, as this is not equational. Newman (1931) has
discussed such remarkable cases, and pointed out that studying the
finger prints of twins should be regarded only as a final check on
diagnoses.

References on Twins

Curtius, Fr. 1930- Nachgeburtsgefunde bei Zwilligen und Ahnlich-

keite-diagnosis. Arch. f. Gynakologie, Bd. 140, Heft 2 u. 3.
Newman, H. H. 1917. The Biology of Twins. Chicago Press.

S36 EVOLUTION, HEREDITY, EUGENICS

Newman, H. H. 1923. The Physiology of Twinning. Chicago Press.
Newman, H. H. 1931- The finger prints of twins. Jour, of Genetics,

vol. 22, no. 3.
Newman, H. H. 1931- Palm print patterns in twins. Jour, of Her.,

vol. 22, no. 2, pp. 41-48.
Patterson, J. T. 1927. Polyembryony in animals. Qu. Rev. of Biol.,

vol. 2, no. 3, pp. 199-426.

Hermaphroditism and the Free-Martin. — Sex intergrades or
hermaphrodites are found in many of the Invertebrate Phyla, and in
all classes of vertebrates. Crew has described an instance of sex
reversal in a frog which changed from a normally functioning female
to a male that was capable of fertilizing eggs and had 774 offspring,
all females. Crew also described a fowl that changed from a fertile
female to a fertile male. Riddle reported sex reversal in the pigeon.

Intersexuality in the lower mammals is quite common. It has
been described in cattle, sheep, pigs, goats and rabbits. Some of
the most interesting studies have developed in connection with
"free-martins." The "free-mariin" known for years to stock
breeders, is an incomplete female born co-twin with a male.

The chorionic membranes of the two embryos are fused together
and the blood vessels anastomosed so as to produce a common
circulation. The testis of the bull calf develops more rapidly than
the ovary and its embryonic interstitial gland supposedly exercises a
masculinizing influence.

Tandler and Keller (1916) and Lillie (1916 and 1917) independ-
ently showed that in the free-martin the twins come from two eggs.
They concluded that the free-martin is a female whose gonads have
been transformed into a testis-like organ by male hormones from
her twin brother. Willier has said, " the primordium of each male
structure developed in the free-martin gonad is present in the ovary
at the time of sex differentiation." Bissonnette has shown that the
free-martin began as a female and developed as such for some time,
then became modified in the male direction internally, though almost
never externally.

References on Free-Martins

Bissonnette, T. H. 1924. The development of the reproductive ducts
and canals in the free-martin with comparison of the normal.
Am. Jour, of Anat., vol. 22, no. 2, pp. 267-345.

EVOLUTION, HEREDITY, EUGENICS 537

Crew, F. A. E. 1923. Studies in intersexuality. I. A peculiar type
of developmental intersexuality in the male of the domesticated
mammals. Proc. Roy. Soc, B, vol. 95, pp. 90-109. II. Sex reversal
in the fowl. Proc. Roy. Soc, B, vol. 95, pp. 256-278.

DoMM, L. V. 1927. New experiments on ovariotomy and the problem
of sex inversion in the fowl. Jour. Exp. Zool., vol. 48, pp. 31-174.

Hartman, C. G. 1920. The free-martin and its reciprocal in the
opossum, man, dog. Science, n. s., vol. 52, pp. 469-471.

LiLLiE, F. R. 1917. The free-martin: a study of the action of sex
hormones. Jour. Exp. Zool., vol. 23.

LiLLiE, F. R. 1923. Supplementary notes on twins in cattle. Biol.
Bull., vol. 44, pp. 47-78.

WiLLiER, B. H. 1 920. Structures and homologies of free-martin gonads.
Jour. Exp. Zool., vol. 23y PP- 63-127.

Hen-Feathering in the Seabright Bantam. — We have elsewhere
referred (see p. 444, Internal Secretions) to the work of Goodale and
others in removing the ovary from the fowl, with the result that
the bird took on the plumage and the behavior of the cockerel.
T. H. Morgan, having observed that the cockerel of the Seabright
bantam is normally hen-feathered, performed experiments (1915)
which he thought furnished sufficient evidence that hen-feathering
in the male was due to endocrine action from luteal cells in the
testes. Roxas showed (1926) by cross transplantation of the testes
of Seabright and Leghorn fowls that no special hormones are pro-
duced by the hen-feathered Seabright bantam, as the soma of the
Seabright bantam reacts to either the male or the female hormone
by hen-feathering. Domm (1927) ovariotomized Leghorn fowls,
and noted that a compensatory testis-Iike organ developed on the
right side, but that subsequently the plumage became hen-like.
This state resembled that of the Seabright bantam, in which the
sexually male bird is hen-feathered. Riddle (Anat. Rec, 1925, vol.
30, pp. 365-384) had previously shown that when the ovary was
removed in the bird testicular tissue developed.

Danforth (1928), having made exchange grafts between hen-
feathered and cock-feathered male bantams, has shown that the
differential factor is inherent in the skin.

References on Hen-Feathering

Danforth, C. H. 1928. Proc. Soc. Exp. Biol, and Med., vol. 26, p, 86.
Domm, L. V. 1927. Jour. Exp. Zool., vol. 48, pp. 31-174,

538

EVOLUTION, HEREDITY, EUGENICS

Morgan, T. H. 1915. Proc. Soc. Exp. Biol, and Med., vol. 13, p, 31.
RoxAs, T. A. 1926. Jour. Exp. Zool., vol. 46, p. S^.

Genes. — Johannsen has given the name genes to those hereditary-
germinal factors that may sometimes need to combine to produce
a visible somatic character. Genotypes are individuals having the
same germinal composition, while phenotypes are a group of in-
dividuals with similar external
features. Genes may act in
single pairs or in several pairs.
Plural genes may be alike in
separate effects but cumula-
tively may produce another
effect. Again they may be
compleynentary or supplemen-
tary to other factors or they
may be lethal.

1 2 A 2 B 2 C Chromosome Maps and

Fig. 268. Crossing over during syn- Crossing Over. — Morgan and

apsis of homologous paternal and maternal j^j^ coworkers have adequately
chromosomes. The segments indicate the
assumed linear arrangement of the genes
with allelomorphic genes opposite each
other. I, pair of chromosomes which have
entered and emerged from the synaptic
state without any crossing-over; Ila, chro-
mosomes winding about each other at r /o ^\ •

TTi • f u u of genes (Sturtevant) is one

synapsis; iib, separation or these chromo- ® ^ .

somes, involving breaking at the points of that furnishes a satisfactory

crossing; Ik, their emergence from synap- explanation of SUch phenomena

sis with the members of the pairs of allelo- as linkage and recombination

morphic genes interchanged. (After Wil- jnvolved in the " croSS-OVer."

son, homWoodrxiS, Foundations of Biotozy. t > 1 ir r ^l 7*

r \ f Tk i\/r 1! n \ Janssens theory ^^ of the chtas-

Courtesy ot 1 he Macmillan Co.) •' ■'

matype was elaborated by Mor-
gan and his students, who suggested that when the paired chromo-
somes are side-by-side at synapsis (Fig. 260) the /«c/orj' of the two
chromosomes may become exchanged. If two genes are close to-
gether, crossing-over of the two factors is unlikely to occur, but
as the distance between them increases, the chances of crossing-over
are much greater. By this means, Sturtevant, Bridges and others

demonstrated that Roux's con-
ception of the chromosomes as
a linear series of smaller bodies
was the correct one. The
theory of linear aggregation

1^ Janssens, F.
ibid., 34, 1928.

1909. La theorie de la Chiasmatypie. La Cellule, Tom. 25; also

EVOLUTION, HEREDITY, EUGENICS 539

have been able to locate factors in particular chromosomes, map-
ping out their relative positions.'^ Bridges has recently emphasized
the probability that the genes are possessed of tremendous catalytic
activity.

Lethal Factors. — It has been found that in the fruit fly (Dro-
sophila) a number of lethal factors are in the X-chromosome.
Females with the lethal factor in both X-chromosomes will die;
and males with the lethal factor in their single X-chromosome
likewise die. The males that survive are those that lack the X-
chromosome and its lethal mutant factor. Lethal factors exist in
some other chromosomes besides the accessory or X-chromosomes.

Non- Disjunction. — In 1913, Bridges discovered that unexpected
individuals obtained in his breeding experiments with white-eyed
Drosophila might be explained by assuming that the X-chromo-
somes did not disjoin and go to the two poles during maturation
division of the egg but remained attached to each other, and passed
to one pole. This would leave the other pole without any X-chromo-
some and in the resultant eggs one-half would possess two X-
chromosomes, while the other half lacked the X-chromosome.
Cytological evidence supported the hypothesis.

Parthenogenesis. — In parthenogenesis the offspring may be
male, female, or parthenogenetic females. In the Hymenopera
fertilized eggs develop into females and unfertilized eggs into males.
In the Rotifers and Daphnids the fertilized eggs produce females,
but during parthenogenesis males come from small thin-shelled eggs
while females develop from larger glycogen-laden eggs. Even in
the frog, Parmenter has found that parthenogenetic eggs develop
into males and females.

Evidence For and Against the Inheritance of Acquired Characters.
/. Are Somatic Acquirements Transferred as Such to the Germ
Cells? — Weismann cut off the tails of mice for nineteen generations
without effect on future generations. Blood transfusion refuted the
Pangenesis theory. There may be passive transmission of certain
dyes, syphilis, white diarrhea, pebrine, and Texas fever. There is

17 But H. Przibram (Quanta in biology, Proc. Roy. See. of Edinburgh, vol. 49, pt.
3, pp. 224-231, 1929) suggests that crossing-over may be regarded as a "crosswise sub-
stitution of atoms or groups of atoms, the chain of genes remaining unbroken." (Con-
sult T. H. Morgan, The Theory of the Gene. Yale Univ. Press, New Haven, Conn.,
1926, and C. E. McClung, The chiasmatype theory of Janssens. Qu. Rev. of Biol., vol.
2, PP- 344-366, 1927-)

540 EVOLUTION, HEREDITY, EUGENICS

no certainty about maternal inheritance of tuberculosis, but it is
possible that there is inherent predisposition. Antitoxins and im-
mune bodies may apparently be transmitted through the egg.

Monstrosities in fishes and echinoderms by alteration of the salt
constituency of the water are not heritable. Roberts increased the
size of vestigial wings in a race of Drosophila by high temperature.
Under normal temperature the effect did not persist. Castle and
Phillips transplanted guinea-pig ovaries, black to white, demonstrat-
ing that the soma has no influence in determining color of the off-
spring. Griffith found that direction of rotation of rats is specific
in the type of disequilibration produced. Kammerer supplied light
stimulus to cave animals and procured eye development. Pictet
fed gypsy moths walnut instead of oak leaves, and induced a lighter
color, which persisted for only two generations. Johannsen proved
that the effect of parental starvation wears off in just a few genera-
tions.

II. Can Environment Induce Mutations? — Arsenic, quinine, mor-
phine, alcohol, ether, and other poisons affect the first generation
only in Drosophila.

Plough (1917), by two consecutive days' exposure of the females
to high temperature (31.5° C), was able to increase the percentage
of crossing over in chromosomes II and III of Drosophila. His
study showed that crossing over in Drosophila does not take place
in the early oogonial divisions. He considers that his work does
not bear on mutations but explains the mechanism of crossing over.
Mavor (1921) x-rayed female Drosophila and produced non-
disjunction (page 539) of the X-chromosomes, as shown by an
increased number of exceptional males and exceptional females in
the first generation. These females continued to produce ex-
ceptional offspring! Later (1924) as a special case of non-disjunc-
tion, he produced gynandromorphs. Mavor and Svenson (1924)
increased the percentage of crossing over in chromosomes II and III
of Drosophila by x-raying the virgin females one day prior to mating.
Little and Bagg (1924) used x-rays on mice, with results suggest-
ing induction of a new gene. MuUer (1927) exposed sperms of
Drosophila to rather heavy doses of x-rays and produced " gene
mutations " in a large number of the germ cells. He succeeded in
producing with the treated sperms a number of familiar mutants
such as " white eye " and " forked bristles " as well as other en-

EVOLUTION, HEREDITY, EUGENICS 541

tirely new mutants. Mutations were produced with x-rays In
barley and corn by Stadler, and in tobacco by T. Goodspeed.

Blakeslee produced mutations in Datura by exposing the parent
plants to cold at flowering time. Goldschmidt (1929) by subjecting
early larval stages of Drosophila to high temperature (37° C.)
secured quite definite mutations. Further important studies have
been carried on by I|il\^fyki4^^3^ Jollos (1930), who claims to produce
increasingly graded effects by continued exposure to the same high
temperature.

///. Is There Parallel Induction or Independent Simultaneous
Modification of Germplasm and Soma? — Stockard and Papanicolau
used alcohol fumes on guinea pig parents, producing corneal irritation
and opacity in their eyes; their offspring showed a different type of
defect. Types of defects appearing in the offspring were abortion
and stillborn litters, nervous disorders, eyelessness and mon-
opthalmicum asymmetricum, and body deformations. Parents
were unaffected. McDowell and F. Hanson have made important
studies on alcoholic effects in mammals, and R. Pearl has concluded
that in the fowl alcohol kills the unfit germ cells.

Standfuss, working with butterflies, and Fischer and Schroder,
with moths, produced melanism by use of extreme temperature.
Some of the offspring showed the character. Harrison and Garrett
induced melanism in Lepidoptera by adding manganese sulphate
and lead nitrate to their diet, and found melanism appearing in
certain of the subsequent broods. Schroder reported success in
modifying the pupation instinct in certain caterpillars, and feeding
habits in others, with the acquirements transmitted. Tower re-
ported modifications in the potato beetle, as a result of temperature
and humidity regulation, which were inherited if applied during the
germ cell maturation period, but not if treated at other times.

Brown-Sequard produced nervous disorders apparently heritable
by injuring sciatic nerve, spinal cord, or brain of guinea pigs. But
an epileptic condition is often found in the species.

Kammerer extended the area of yellow on the European sala-
mander by use of a yellow background. The effect persisted in the
offspring, regardless of any kind of background. Castle suggested
simple selection as the cause. Kammerer also was able practically
to change reciprocally the species Salamandra atra and S. maculosa^
not only in reproductive habits, but in other respects as well. Modi-
fications: i. Number of young greatly reduced (2-7); 2. Intrauterine

542 EVOLUTION, HEREDITY, EUGENICS

fats of eggs and embryos approached that of black salamander; 3.
Color almost totally black. (These characters persisted.)

Guyer and Smith injected pulped rabbit lenses into fowls, and
injected serum from those treated into pregnant rabbits, without
effect on the adult; the offspring showed nearly 15 per cent defective
eyes, suggesting antibodies. The defects were transmitted in
reciprocal in-'and-out crosses through nine generations. Szily,
J. Huxley, and other investigators have criticized the experiment
severely, and efforts at repetition on the part of several have failed
to procure similar results.

Sumner used a cold room on mice to produce shorter tails and
feet. Offspring from gestation at ordinary temperature showed the
character in three cases, but in the fourth the appearance was
reversed. Pavlov trained mice to come for food at ringing of a bell;
the number of lessons was reduced from 300 in the first generation
to 100 in the second, 30 in the third, and 10 in the fourth. In later
generations as few as five lessons were required. Others have not
found training effects inherited.

References

Detlefsen, J. A. 1925. The Inheritance of acquired characters.

Phys. Review, 5, pp. 244-278.
GoLDscHMiDT, R. 1929. Experimentelle Mutation und das Problem

der sogenannten Parallel-induktion. Biol. Zbl., 49.
JoLLOs, V. 1930. Studien zum Evolutionsproblem. Biol. Zentr., Bd.

50, H. 9, S. 541-554-
Mavor, J. W. 1921. On the elimination of the X-chromosome from the

egg of Drosophila melanogaster by X-rays. Proc. Soc. Exp. Biol, and

Med., vol. 18, pp. 301-304.
Muller, H. J. 1927. The Problem of Genie Modification. Z. indukt.

Abstammungslehre, Supplbd. i.
Plough, H. 1917. The effect of temperature on crossing over in

Drosophila. Jour. Exp. Zool., vol. 24, no. 2, pp. 147-209.

Is There Such a Thing as Inheritance of Disease? — We must at
once distinguish between (i) prenatal infection; (2) prenatal injury
to the germ or the embryo; (3) the inheritance of weakness predis-
posing to disease; and, finally, (4) true inheritance due to germinal
transmission.

1. Prenatal Infection. — This may occur through the mother in
utero or by the infection of either egg or sperm. In all probability,

EVOLUTION, HEREDITY, EUGENICS 543

the majority of cases are those of actual infection before birth.
It has been shown that in the fowl the eggs may be infected while
in the oviduct with the organisms causing bacillary white diarrhea.
There has been some argument over the filterability of the tubercu-
losis germs, but it is quite probable that even if a child escapes
prenatal infection, it will become diseased shortly after birth.

2. Prenatal Injury to the Germ Cells or the Embryo. — Besides
weakening the embryo, it has been found that drugs and alcohol
may produce anomalies of the brain and eyes, particularly, and in
guinea pigs it has been proved that the germ cells may be affected
so that the effect will persist for several generations. A mother
with goiter may produce defective and goitrous children.

3. Inheritance of Weakness Predisposing to Disease. — Almost
any system may be subject to weakness inheritance. The blood-
forming organs may be weak and a family line may be unable to
resist minor diseases that would ordinarily not prove fatal. A
defective pancreas may predispose to diabetes, or one may inherit a
general weakness of body, particularly of brain, that predisposes
to the use of a stimulant, such as alcohol or some drug.

4. Inheritance through the Germinal Substance. — Insanity,
feeble-mindedness, idiocy and allied mental diseases are apparently
transmitted through the germs. They may appear in the offspring
from two family lines in which the defect has been recessive (not
apparent) for several generations. It is therefore wise to know the
defects in both strains before marriage, and avoid the production
of children defective or abnormal.

Five types of defects are closely tied up with the germinal
determiners producing sex. These are Gower's muscu/ar atrophy;
he?nophilia {slow clotting of blood); color blindness or Daltonism
(inability to distinguish red from green); night-blindness; and a
peculiar disease, neuritis optica, causing atrophy of the optic nerve.
Males inherit these defects and females may transmit them without
showing the abnormality. In order to produce them in females it
requires a double dose of the determiner. (See page 534.)

Maternal Impressions. — One of the oldest superstitions is the
one that if a pregnant mammal is obsessed or frightened by seeing
a deformed or peculiarly marked animal, the offspring will resemble
the object of interest. The only truth in the idea of maternal
impressions lies in the influence of foods and of the emotions on the
nutrition of the very early embryo. As reports of maternal im-

544 EVOLUTION, HEREDITY, EUGENICS

pressions are usually based on accidents long after the organs and
systems of the embryo are developed past the probability of being
affected by slight nutritional disturbance, the maternal impression
idea must be dismissed as unproved.

Eugenics, — The old cry of the politician (seeking a heavy labor
vote) that we must infuse new blood into our land to prevent the
decay incident to inbreeding of the race becomes less forceful when
we view in an unprejudiced way the important work of Doctor King
and others in connection with the problem of inbreeding. ^^ Doctor
King has definitely proved that in the white rat it is possible to
select within a Hne, until, by a long continued process of inbreeding,
a stock far superior to the original was produced. We have much
evidence also from the long continued inbreeding of race horses and-
hunting dogs, as well as the vast amount of work on plants.

It matters little whether we are able to determine exactly the
acquired characters that are inherited, if we do not exert ourselves
to control both the germplasm and the environment. Certainly
degeneration may occur. As Sancho Panza said, " we are as God
made us, and some of us even worse."

Believing that there has been an evolution in the differentiation
of races, we are attempting to apply our knowledge of heredity to
increase the number of superior beings. But these superior persons
must be given something besides mere education. As the Iron
Duke said, " Gentlemen, If you are only going to educate the
children, you are only going to make them clever devils."

With the forces of evil rampant, and with the descendants of
reputable people taking on all of the vices and but few of the virtues
of certain savages who are trying to make the world a chaos, it
would seem that drastic measures must be taken.

Children are shot down in our streets by warring gangsters,
and still the so-called "intelligentsia" continue to demonstrate to
their own children the depths to which people will descend, people
who are not willing to conform to the laws of common decency
merely because some one has said that it is "fashionable" to
break laws. Meanwhile the social aristocracy of our land continue
to live decently, and to deplore the degradation of the social
climbers who think they are having a "perfectly swell time."

'8 Dahlberg, G. 1929. Inbreeding in man. Genetics, vol. 14, no. 5, pp. 421-454.
East, E. M., and Jones, D. F. 1919. Inbreeding and Outbreeding. J. B. Lippincott
&Cq.

EVOLUTION, HEREDITY, EUGENICS 545

Negative Eugenics. — One important factor in negative eugenics
consists in the regulation of immigration by the exclusion of idiots,
insane, and otherwise inferior persons from our country. Segrega-
tion of some of our unfit, so that they are not menaces to society,
is another measure in favor at present. Sterilization of the most
defective individuals is now legal in a number of states. This
measure consists in either searing or severing the Fallopian tubes of
the female, and in the male the operation of vasectomy, i.e., severing
the vas deferens. In neither case does the person lose the benefits
of the internal secretions (page 444) but the defectives are unable to
reproduce.

Positive Eugenics. — Education is the foremost agency in positive
eugenics. By lectures and tracts, the American Eugenics Society
is attempting to have as many persons as possible fill out records of
their family pedigrees and send them to the Eugenics Record Office,
Cold Spring Harbor, L. I. It is also encouraging those best fitted
to do so to produce four children per family.

APPENDIX

Wave-length

Ultraviolet radiation 0-39001;^

Extreme region 0-200

Gamma rays (arbitrary limits) o to o.oimju
Rontgen rays (arbitrary limits) o.oi to ^om/j.

Middle or intermediate region 200-300

Near region 300-390

Visible radiation 390-77omM

Violet 390-430

Blue 430-470

Blue-green 470-500

Green 500-530

Yellow-green 530-560

Yellow 560-590

Orange 590-620

Red 620-770

Infra-red radiation 0.77-co fi

Near region O'V?"" ^o

Infra-red photography to ifi
Fluorite prism to lo/x
Rock salt prism to 2om

Intermediate region 20-500

Selective reflection from rock salt to 50/u
Selective reflection from potassium chloride to 6l/x
"Restrallen" method up to 354M
Electric oscillator method up to 500M

Extreme region 500-00

Electric waves such as that radiant energy studied by Herz,
that used in wireless electric circuits, that resulting from high
frequency currents, and that due to ordinary alternating
currents complete a long range of wave-lengths to beyond
12 km. in wave-length.

The More Acctu-ate Eqtiivalents Used for Exacting Computations.

I cubic inch of water = 251.889 grains

I inch = 25.4001 miUimeters

3600

I yard = meter

3937

I U. S. wine gallon = 3785.33 cubic centimeters or

3785.33 grams of pure water

I meter = 39.370432 inches

I fluid ounce = 29.5737 cubic centimeters

I liter = 33.8 14 fluid ounces

I pint (O.) = 473.179 cubic centimeters

I milliliter (cc.) = 16.23 minims

I gram = 15.43235639 grains

I grain = 64.7989 milligrams

I apothecary ounce = 31.1035 grams

I ounce (av.) = 28.35 grams

I pound (lb.) = 453.592 grams

I kilogram (Kg.) = 2.20462 pounds

546

GLOSSARY

Absorption (Lat. absorbere, to swallow down): the process by which liquid food or
other substances are taken through cell wails.

Adaptation (Lat. adaptere, to fit): changes in organisms which fit them to their environ-
ment.

Afferent (Lat. ad, to; jero, bear) fibers: those conveying stimuli to sense organs, brain
or spinal cord.

Albu'men (Lat. albumen, white of egg): protein residing in white of egg.

Allan'tois (Gr. alias, sausage; eidos, form): membranous organ growing out of the hind
gut in the embryos of reptiles, birds and mammals, and serving for respiration
and excretion.

Altricial (Lat. altrix, nurse) : birds that are helpless on hatching.

Am'nion (Gr. amnos, a lamb): membranous sac which encloses the embryos of reptiles,
birds and mammals.

Amphib'ian (Gr. amphi, both; bios, life): animals able to live on land and water.

Anat'omy (Gr. ana, up; temno, cut): the science of gross bodily structure.

Ar'tery (Gr. aer, air; tereo, keep): vessels conveying blood from the heart to the organs.

Ax'on (Gr. axon, axis): main outgrowth of a neuron.

Blas'tomere (Gr. blastos, embryo; meros, part): a cell produced by segmentation of a
fertilized egg.

Blas'topore (Gr. blastos, embryo; poros, passage): the external opening of a gastrula.

Bias 'tula (Gr. blastos, germ): the stage at the end of segmentation when the embryo
is a hollow sphere with no opening.

Bronchus, pi. bronchi (Gr. bronchos, windpipe) : one of the two large subdivisions of the
trachea.

Calorie (Lat. calere, to be hot) : amount of heat required to raise one kilogram of water
one degree Centigrade.

Capillary (Lat. capillus, a hair): the microscopic blood vessels uniting arteries with
veins.

Carbohy'drate (Lat. carbo, coal; Gr. hydro, water): food stuffs made of carbon, hydro-
gen and oxygen, the hydrogen and oxygen being in the same proportion as water.

Carniv'orous (Lat. caro (carnis), flesh; vo'rare, to eat): flesh-eating animals and plants.

Car'tilage (Lat. cartilago, gristle): the elastic animal tissue forming parts of organs or
bones.

Caud'al (Lat. cauda, tail): pertaining to the tail.

Cell (Lat. cella, a small room): the unit of living things. A mass of protoplasm in-
closing a nucleus, and usually inclosed in a cell wall.

Cellulose (Lat. cellula, a little cell): an organic substance found in the walls of plant
cells, and in the Tunicates.

Cere (Lat. cera, wax): a fleshy growth at the base of the bill of some birds.

Chitin (Gr. chiton, a gown or tunic) : the outer covering of the bodies of insects and
other animals.

Chlor'ophyll (Gr. chloros, green; phullon, leaf): the green substance enabling green
plants to utilize sunlight to build up food.

547

548 GLOSSARY

Chrom'atin (Gr. chroma, color): a stainable constituent of the nucleus.

Cil'ium (Lat.ci/iicm, an eyelid with eyelashes): a tiny hair-like protoplasmic projection

attached to the surface of a cell.
Cocoon (Lat. concha, shell): the hairy or silken covering of the pupa of some insects;

the egg case of spiders and earthworms.
Coe'lom (Gr. koilos, hollow): the body cavity; location of organs.
Coleop'tera (Gr. coleos, sheath; -pteron, wing): an order of insects with hard wing covers

over the flying or true wings: the beetle.
Conjuga'tion (Lat. con, with; jngare, to join): the temporary union of two similar cells

for the purpose of exchanging nuclear protoplasm.
Cor'puscle (Lat. corpusculum, a little body): the floating cells in the blood.
Cor'tex (Lat. cortex, bark): the fleshy portion of a root surrounding the central cylinder

and covered by epidermis.
Crusta'cea (Lat. criista, a crust): a class of invertebrates characterized by a hard exo-

skeleton, as crayfish.
Cytoplasm (Gr. kytos, vessel; plasma, anything formed): the form of protoplasm making
up the main part of a cell. It incloses the nucleus, and is inclosed by the cell
wall. The protoplasm of a cell excluding the nucleus.
Den 'tine (Lat. den{t)s, a tooth): the inner portion of a tooth.
Dermis (Gr. derma, skin): the true skin, lying beneath the epidermis.
Di'aphragm (Gr. diaphragma, a partition wall): the sheet of muscle separating the chest

cavity from the abdominal.
Diges'tion (Lat. digestio, the dissolving of food): the preparing of food for absorption.
Dip'tera (Gr. di, twice; pteron, wing): an order of insects having only two wings, as fly

and mosquito.
Ec'toderm (Gr. ectos, outside; derma, skin): the outer layer of cells of animals.
Ec'toplasm (Gr. ectos, onts\de; plasma, thing moulded): the outside layer of unicellular

organisms.
Em'bryo (Gr. embryon, an embryo): an organism within the egg membrane.
Embryol'ogy (Gr. embryon, an embryo; logos, a talk or discourse): the study of the

early development of organisms.
Encyst'ment (Gr. en, in; kystis, a bladder): the inclosing in a resistant covering; forming

of a cyst.
En'docrine system (Gr. endon, within; krinein, to separate): all the tissues of internal

secretion; the ductless glands.
Endoderm (Gr. endon, within; derma, skin): the inner layer of cells in animals.
En'doplasm (Gr. endon, W\\i\{\r\; plasma, substance): the inner portion of the protoplasm

in unicellular animals.
En'dostyle (Gr. endon, within; stulos, pillar): ventral glandular groove in the pharnyx

of Amphioxus.
En'zyme (Gr. en, in; %yme, leaven): a substance secreted by organisms which induces

chemical changes, as digestion.
Ephemer'ida (Gr. ephemeros, for a day): an order of insects which live only a few hours.
Epiph'ysis (Gr. epiphusis): the bony disk or pad, derived from a separate center of

ossification, found at either extremity of limb bones and vertebrae.
Epithel'ium (Gr. epi, upon; thele, teat): a sheet of tissue covering or lining a surface.
Eryth'rocyte (Gr. eruthros, red; kutos, cell): a red blood-corpuscle.
Eugen'ics (Gr. eugenes, well-born): the study of heredity for improvement of off"spring.

GLOSSARY 549

Evolu'tion (Lat. e, out; who^ roll): organic descent.

Excre'tion (Lat. excretus, separated out): waste products removed from the protoplasm.
Excur'rent (Lat. ex, out; currere, to run) stem: a stem extending from base to tip with-
out dividing, as spruce and cedar.
Exhal'ant (Lat. ex, out; halo, breathe) pore: the central opening at the top of a sponge

through which water passes outward.
Ex'oskeleton (Gr. ex, out; skeleton, a dried body): outer covering of animals.
Exten'sors (Lat. ex, out; tendo, stretch): muscles which straighten an appendage at the

joint, as arm.
Fe'ces {\^a.t:. faeces, dregs): wastes from the digestive system; excrement.
Fertiliza'tion {hat. ferti lis, from/ero, bear): the union of the sperm nucleus with the

egg nucleus to form a new organism.
Fibrin'ogen {^x. fibre, a fiber): the blood substance inducing clotting by the production

of fibers when exposed to air.
Flagel'lum (\^at. flagellum, a whip): a long protoplasmic projection, used chiefly for

locomotion.
Flex'ors {hat.flexus (flecto), bend): muscles that bend the joints; those which oppose

the extensors.
Func'tion (Lat. functio, performance): the normal action of organisms.
Gall (Lat. gaila, gallnut): a growth produced on certain leaves by the action of insects;

the bile.
Gan'glion (Gk. ganglion, tumor): an aggregation of nerve cell-bodies.
Gene (Gr. genos, origin): heredity factors which segregate according to Mendelian

principles.
Gen'us (Lat. genero, beget) : a group of organisms containing one or more species.
Giz'zard (Lat. gigeria, cooked entrails of poultry): the muscular chamber for grinding

food in birds.
Glomer'ulus (Lat. glomero, make a ball): minute rounded bodies in the cortex of a

kidney; a knot of blood vessels; a Mapighian body.
Glot'tis (Gr. glotta, tongue): the tracheal opening.
Glu'cose (Gr. glykys, sweet): constituent of sucrose found in fruits; the product of the

digestion of starch.
Gly'cogen (Gr. glykys, sweet; gen, producing): animal starch stored in the liver.
Go'nad (Gr. gonos, reproduction): an organ of sexual reproduction (ovary or testis).
Hab'itat (Lat. habito, inhabit): dwelling-place; region of activity.
He'moglobin (Gr. haima, blood; L. globus, round) : the red coloring matter in blood, con-
cerned with the transport of oxygen.
He'morrhage (Gr. haima, blood; rhegnymi, break): the discharge of blood from a

ruptured blood vessel.
Hemip'tera (Gr. hemi, half; pteron, wing): an order of insects whose wings are hard

anteriorly and membranous posteriorly.
Hered'ity (Lat. heres, a hair): the passing on of characters of parents or other ancestors

to offspring.
Hiberna'tion (Lat. hiems, winter): a death-like torpor and rigidity brought about by

extreme cold in some animals.
Histology (Gr. histos, web; logos, discourse): the study of tissues and cells.
Homop'tera (Gr. homos, same; pteron, wing): a group of insects with wings of the same

texture throughout as contrasted with Hemiptera.

550 GLOSSARY

Hor'mones (Gr. hormaein, to excite): substances secreted directly into the blood in one

part of the body which incite action in another part of the body.
Humor (Lat. humere, to be moist): the transparent liquids of the eyeball.
Hymenop'tera (Gr. hymen, a membrane; pteron, wing): an order of insects (including

bees) with membranous wings.
Ichneu'mon (Gr. ichneuo, hung): a hymenopterous insect which lays its eggs on the

larvae of other insects or in them; a helpful parasite.
Immu'nity (Lat. immunis, free from duty): the condition which prevents a person from

contracting infectious diseases.
Incis'or (Lat. incido, cut into): a cutting tooth.
Insectiv'ora (Lat. insectum, insect; voro, to eat): order of insect-eating vertebrates,

including moles.
Inser'tion (Lat. insertus, from in, in; sero, join): the place of attachment of a muscle.
Integ'ument (Lat. in, in; tego, cover): an outer covering or envelope, as the skin.
Intes'tine (Lat. intestinus, internal): the alimentary canal in vertebrates between the

stomach and the anus.
I'ris (Gr. iris, rainbow): the colored portion of the eye.
Irritabil'ity (Lat. irritabilis, from irrito, excite): reaction to stimuli.
Joint (Lat. y««^o, join): meeting-place of two bones; an articulation.
Lep'idop'tera (Gr. lepis, scale; pteron, wing): the order of insects characterized by scaly

wings, as moths and butterflies.
Leu'cocyte (Gr. leiikos, white; kutos, vessel): a white blood-corpuscle.
Lig'ament (Lat. ligare, to bind): a band of tissue binding one bone to another.
Lip'oid (Gr. lipos, fat; eikos, like): a substance found in the nervous system which is

dissolved by anaesthetics or narcotics.
Locomo'tion (Lat. locus, place; motus from moveo, move): movement from one place to

another.
Lymphat'ic (Lat. lympha, clear water): a vessel conveying lymph.
Mala'ria (Lat. malus, bad; a^T, air): a disease caused by parasitic protozoons which

live in the mosquito, Anopheles, during part of their life history, and part in the

blood of man to which they are transmitted only by the bite of this mosquito.
Mam'mary (Lat. mamma, breast) glands: the milk-secreting glands, characteristic of

mammals.
Man'dible (Lat. mandere, to chew): the cutting part of the mouths of crustaceans.
Marsu'pials (Gr. marsipion, a little pouch): an order of mammals having a pouch in

which the young are carried, as opossum, kangaroo.
Medus'a (Gr. medousa, the gorgon): a name given to the main free-swimming type of

Coelenterate, the jelly-fish.
Mes'entery (Gr. mesas, middle; enteron, intestine): tissue which suspends the intestine

from the dorsal wall of the abdomen.
Metamor'phosis (Gr. meta, beyond; morphe, form): a life history in which the organism

passes through abrupt changes of form, as the butterfly, frog.
Mesotho'rax (Gr. mesos, middle; thorax, thorax): the middle section of the thorax of an

insect.
Metab'olism (Gr. meta, beyond; ballein, to throw): the chemical processes which take

place in a living organism.
Migra'tion (Lat. migro, move): moving from one locality to another, as birds, salmon.

GLOSSARY 551

Mim'icry (Gr. mimikos, imitative): resemblances in form or color shown by some
organisms to other objects, to protect themselves.

Mito'sis (Gr. mitos, thread): the processes in typical nuclear division.

Mollusks (Lat. mollis, soft): a group of animals having soft bodies, usually covered by
one or two shells.

Morphol'ogy (Gr. morphe, form; logos, discourse): study of structure and form.

Motor (Lat. moveo, move) fibers: nerve fibers which convey impulses to the muscles,
producing motion.

Mu'cous (Lat. mucus, slime) membrane: the lining of the alimentary canal and respira-
tory tract.

My'osin (Gr. myo, muscles): the form of protein found in muscle.

Myriop'oda (Gr. myrioi, ten thousand; /)o«j, foot): a group of crustaceans having four
legs on each segment.

Neuroblast (Gr. neuron, sinew; blastos, germ): an embryonic nerve cell.

Neu'ron (Gr. neuron, sinew): a nerve cell with all its processes.

No'tochord (Gr. notos, the back; chorde, a string): a rod of cells in all vertebrate em-
bryos.

Nour'ishment (Lat. nutrio, nurse or feed): growth-promoter; food.

Nu'cleus (Lat. nucleus, a kernel): specialized protoplasm.

Nutri'tion (Lat. nutrio, nurse or feed): that which promotes growth.

Odona'ta (Gr. odontos, toothed): an order of insects, including dragon flies and damsel
flies.

Oesoph'agus (esophagus) (Gr. oiso, will bear; phagein, to eat): the alimentary canal
between the pharynx and stomach.

Oper'culum (Lat. operculum, lid): the gill cover in fishes.

Optic (Gr. optikos, sight) nerve: nerve which conducts stimuli from retina to brain.

Or'ganism (Gr. organon, instrument): a living body.

Or'thogen'esis (Gr. orthos, straight; genesis, descent): evolution in a definite direction.

Orthop'tera (Gr. orthos, straight; pteron, wing): a group of insects whose outer wings
meet in a straight line in the middle of the back, as grasshoppers and crickets.

Osmo'sis (Gr. osmos, pushing): the passing of soluble substances through a moist
membrane, the greater movement being towards the denser liquid.

Par'asite {Gr. para, beside; sitein, to feed): an animal or plant which lives upon another
living organism injuring its host.

Parathyroid (Gr. para, beside): a small ductless gland near the thyroid controlling the
calcium metabolism of the body.

Pec'toral (Lat. pectus, breast) girdle: the bones which support the anterior limbs of
vertebrates and attach them to the trunk.

Pericar'dium {Gr. peri, around; cardia, heart): the membranous sac inclosing the heart.

Perios'teum (Gr. peri, around; osteon, bone): the membrane which adheres to and
covers the bones.

Peristal'sis (Gr. peri, around; stalsis, constriction): the squirming motion in the in-
testine caused by its muscles.

Perspira'tion (Lat. per, through; spiro, breathe): the watery secretion of the per-
spiratory glands.

Pha'gocytes (Gr. phagein, to eat; cytos, sac): the white corpuscles of the blood which
act as scavengers.

SS2 GLOSSARY

Photosyn 'thesis (Gr. p/tos, light; synthesis, nutting together): food-making by green

plants in presence of sunlight.
Phylum (plural phyla) (Gr. phulon, tribe): one of the main groups of the animal king-
dom; about twelve groups are recognized.
Physiol 'ogy (Gr. physis, nature; logos, discourse): the study of the life processes of

organisms.
Pin'eal (Lat. pinea, a pine cone): an organ of doubtful function situated anterior to the

corpora quadrigemina of the brain.
Plas'ma {Gr. plasma, formative material): the liquid portion of the blood of vertebrates.
Plecop'tera (Gr. plectos, plaited; />/fro«, wing) : an order of insects having plaited wings,

as stone flies.
Poi'son (Lat. potto from poto, drink): any substance harmful to the system of an

organism.
Polyp (Gr. polus, many; pons, foot): the sessile type of Coelenterate having numerous

tentacles.
Por'tal (Lat. porta, gate) vein: the large vein that carries blood to the liver.
Pro'tein (Gr. protos, first): a compound of oxygen, hydrogen, carbon and nitrogen, with

traces of other elements.
Pseudopod'ium (Gr. pseudes, false; pous, foot): a projection of protoplasm used by

protozoons for locomotion.
Pro'toplasm' (Gr. protos, first; plasma, form): the physical basis of life; the living sub-
stance contained in organisms.
Pro'tozoon (plural protozoa) {Gv. protos, first; zoon, animal): a unicellular animal.
Pty'alin (Gr. ptyalon, spittle): the enzyme in saliva changing starch to sugar.
Pylor'us (Gr. pyloros, gate-keeper): stomach-intestinal opening.
Rapto'res (Lat. rapere, to ravish) : an order of birds having sharp hooked beaks and

strong, sharp talons; birds of prey.
Reces'sive (Lat. re, back; cedo, yield) characters: those not appearing in a hybrid,

owing to the dominance of other characters.
Rec'tum (Lat. rectus, straight): the terminal portion of the alimentary canal.
Re 'flex (Lat. re, hack; ^ecto, bend) action: non-mental action.
Re 'genera 'tion (Lat. re, again; genero, beget): restoration of a lost part by growing a

new one, as the tentacle of a hydra.
Reproduc'tion (Lat. re, again; pro, before; duco, lead): begetting like; like producing

like.
Respira'tion (Lat. re, again; spiro, breathe): oxidation of protoplasm releasing energy

and producing carbon dioxide.
Ret'ina (Lat. rete, net): the black inmost layer of the eyeball which receives the stimuli

of light rays and conducts them to the brain through the optic nerve.
Ru'minant (Lat. rumen, throat): an animal which chews its cud, as cow.
Sali'va (Lat. saliva, spittle): the natural moisture in the mouth secreted by the salivary

glands.
Sclerot'ic (Gr. skleros, hard) coat: the tough outer coat of the eyeball.
Scute (Lat. scutum, scale): one of the large scales on the snake's abdomen.
Scutel'lum (Lat. dim. oi scutum, shield): the shield-shaped cotyledon lying under the

embryo in grains.
Sex ual (Lat. sexus, sex) reproduction: a new individual arising from the union of an

egg and sperm.

GLOSSARY 553

So'ma (Adjective, somatic) (Gr. soma, a body): the part of the organism limited to its

individual life; non-reproductive.
Sperm (Gr. sperma, from speiro, sow): the male element in sexual reproduction.
Sphinc'ter (Gr. sphiggo, bind tight): a circular band of muscle which closes an aperture

by its contraction.
Spu'tum (Lat. sputus, from spuo, spit): expectorated matter characteristic of certain

diseases.
Steap'sin: a digestive ferment found in the pancreatic juice which assists in the di-
gestion of fats.
Ster'ile (Lat. sterilis, barren): free from bacteria of every kind; infertile.
Stig'ma (Gr. stigma from stizo, prick): any agent that excites to organic action.
Stom'ach (Gr. stomachos from stoma, mouth): the sac or enlarged portion of the di-
gestive tract between the esophagus and intestine.
Sucto'ria (Lat. suctus, from sugo, suck): an order of insects which have sucking mouths,

as fleas.
Su'ture (Lat. sutura, from siio, sew): the joining of two bones by mutually serrated

edges, forming an immovable articulation, as in the bones of the skull.
Symbio'sis (Gr. syn, together; bios, life): the close relationship of two organisms for

mutual benefit.
Tar'sus (Gr. tarsos, any flat surface): the ankle; the scaly part of a bird's leg; the

terminal segment of an insect's foot.
Ten'don (Lat. tendo, stretch): the connective tissue ending of a muscle which attaches

it to other structures.
Ten'tacle (Lat. tento, touch, try): a jointed flexible appendage of the head used for

touch, grasping, or motion; a feeler.
Tes'tis (Lat. testis, a testicle): an organ in a male animal where sperms are produced.
Thy'roid (Gr. thureos, shield; eidos, form) gland: a large ductless gland on the outside

of the trachea below the larynx which secretes thyroxin (C15H11O4NI4).
Tra'chea (Gr. tracheia, windpipe): the air passage from the pharynx to the lungs; an

air tube in insects and spiders.
Tra'cheole (dim. oi tr aches): one of the fine branches of the Tracheae.
Trichinel'la (Gr. thrix, hair): a small round worm sometimes found in pork living as a

parasite, and the cause of trichinosis in man.
Tri'chocysts (Gr. thrix, hair; kystis, bag): dart-like organs of offense and defense found

in Paramecium.
Tro 'chanter (Gr. trochanter, from trecho, run): the second joint of an insect's leg.
Tryp'sin (Gr. tripsis, a rubbing): an enzyme of the pancreatic juice.
Tur'gid (Lat. turgeo, swell): distended with air or liquid; swollen.
Ungula'ta (Lat. unguis, nail): a group of mammals characterized by hoofs.
Ure'a (Gr. oiiron, urine): a nitrogenous compound (CO(NH2)2), the chief waste product

discharged in mammalian urine.
Ure'ter (Gr. oureter, from ouron, urine): a tube, one of two, leading from the kidneys to

the bladder and carrying off the nitrogenous waste in the urine.
U'ropod (Gr. oura, tail; pod, from pous, foot): the modified swimmerets on either side of

the last segment of a crayfish. These, together with the telson (the modified last

segment), make up an appendage useful in swimming backwards.
Ven'tricle (Lat. ventriculus, a little belly): one of the lower chambers of the heart.

554 GLOSSARY

Vermi'form (Lat. vermis, worm', forma, form) appendix (Lat. ad, to; pendo, hang): a
slender tubular pouch of the large intestine near its juncture with the small
intestine.

Ver'tebrates (Lat. verto, turn): the group of animals having backbones.

Villi (Lat. villus, a hair): the minute projections -which cover the lining of the small
intestine; organs of absorption.

Vis'cera (Lat. viscus, an organ of a cavity of the body): the organs of the abdominal
cavity.

Vi'tamin (Lat. vita, life): certain substances in foods necessary for the proper func-
tioning of vital processes.

Vivip'arous (Lat. vivo, live; pario, bear): producing young alive, as cat, man.

Zy'gote (Gr. zygon, joined together): the cell produced by the fusion of gametes in
sexual reproduction.

Zy'mase (Gr. zyme, a ferment): the ferment; a digestive enzyme.

TABLE OF THE ELEMENTS.
Symbols — Atomic Numbers — Atomic Weights.

At.

At.

At.

At.

Symbol number

weight

Symbol

number

weight

Aluminum

Al

13

26.97

Mercury

Hg

80

200.61

Antimony

Sb

51

21.77

Molybdenum

Mo

42

96.0

Argon

A

18

139-91

Neodymium

Nd

60

144.27

Arsenic

As

33

74.96

Neon

Ne

10

20.2

Barium

Ba

56

137-37

Nickel

Ni

28

58-69

Beryllium

Be

4

9.02

Nitrogen

N

7

14.008

Bismuth

Bi

83

209.00

Osmium

Os

76

190.8

Boron

B

5

10.82

Oxygen

0

8

16.000

Bromine

Br

35

79.916

Palladium

Pd

46

106.7

Cadmium

Cd

48

112. 41

Phosphorus

P

15

31.027

Calcium

Ca

20

40.07

Platinum

Pt

78

195-23

Carbon

C

6

12.000

Potassium

K

19

39.096

Cerium

Ce

58

140.25

Praseodymium Pr

59

140.92

Cesium

Cs

55

132.81

Radium

Ra

88

225.95

Chlorine

CI

17

35-457

Radon

Rn

86

222

Chromium

Cr

24

52.01

Rhenium

Re

75

188.7

Cobalt

Co

27

58.94

Rhodium

Rh

45

102.91

Columbium

Cb

41

93-1

Rubidium

Rb

37

85-44

Copper

Cu

29

63-57

Ruthenium

Ru

44

101.7

Dysprosium

Dy

66

162.52

Samarium

Sm

62

150.43

Erbium

Er

68

167.7

Scandium

Sc

21

45.10

Europium

Eu

63

152.0

Selenium

Se

34

79-2

Fluorine

F

9

19.00

Silicon

Si

14

28.06

Gadolinium

Gd

64

157.26

Silver

Ag

47

107.880

Gallium

Ga

31

69.72

Sodium

Na

11

22.997

Germanium

Ge

32

72.60

Strontium

Sr

38

87.63

Gold

Au

79

197-2

Sulfur

S

16

32.064

Hafnium

Hf

72

178.6

Tantalum

Ta

73

181.5

Helium

He

2

4.000

Tellurium

Te

52

127-5

Holmium

Ho

67

163-5

Terbium

Tb

65

159-2

Hydrogen

H

I

1.008

Thallium

Tl

81

204-39

Indium

In

49

114.8

Thorium

Th

90

232.15

Illinium

11

61

Thulium

Tm

69

169.4

Iodine

I

53

126.932

Tin

Sn

50

118.70

Iridium

Ir

77

I93-I

Titanium

Ti

22

47-90

Iron

Fe

26

55-84

Tungsten

W

74

184.0

Krypton

Kr

36

82.9

Uranium

U

92

238.17

Lanthanum

La

57

138.90

Vanadium

V

23

50.96

Lead

Pb

82

207.22

Xenon

Xe

54

130.2

Lithium

Li

3

6.940

Ytterbium

Yb

70

173-6

Lutecium

Lu

71

175-0

Yttrium

Y

39

89.0

Magnesium

Mg

12

24.32

Zinc

Zn

30

65-38

Manganese

Mn

25

54-93

Zirconium

Zr

40

91.22

Masurium

Ma

43

INDEX

Numbers refer to pages. Bold face numbers indicate Figures and Tables.

ABDOMINAL PORES, 236

Abel, 445

Abomasum, 434

Absorption, 109

Acanthocephala, 96

Acarina, 201

Accessory chromosome, ^23

Acid secreting glands, octopus, 158

Ackert, 93

Actinozoa, 6^

Action of the heart, 453

Adaptation of fishes, 261

Adaptation of leech, 117

Adaptations of reptilia, 332

Adhesive pads, 310

Adipose, 426, 436

Adrenals, 447

Aedes, 189

Aelosomatidae, 105

African buffalo, 407

African crocodile, 309

African "hairy frog," 291

African lung-fishes, 252

African wart hog, 401

African Wild Ass, 400, 491

Age, Piltdown Man, 416

Aglossa, 293

Agglutination, 458

Akeley, 414

Albatross, 339

Albino rat, 393

Alcohol and snake-bite, 329

Allen, 444

Alligator snapping turtle, 305

Alpaca, 402

Alpha hormone, 449

Alpine marmot, 392

Alpine race, 417

Alpine salamander, 267

Alternate functioning of the ovaries, 532

Alternation of generations in Obelia, 59,
60-61

Aluminium, 440

Alveolar theory, 8

Ambulacral plates and pores, 132

Ambystoma, 268

Ameba proteus, 22

Amenenhat I, lion-hunter, 381

American alligator, 309

American bison, 407

American black snake, 315

American caribou, 403

American "chameleon," 313

American crocodile, 309

American eagle, 345, 346

American elk or wapiti, 402

American golden plover, 342, 366

American goshawk, 346

American hook-worm, 92

American monkeys, 412

American moose, 402, 404

American porcupines, 394

American woodcock, 343

Amia calva, 242

Amitosis, 500

Amitosis in the cockroach, 500

Ammocoetes, 223

Amnion and Allantois, 302

Amniota, 302

Amphibia, 265-301; classification, 265;
characteristics, 265; economic impor-
tance, 300; fossil relatives, 300

Amphidiscs, 50

Amphioxus, 214

Amphioxus Theory, 217

Amphipoda, 173

Amphitrite, 104

Amphiumidae, 267

Amylopsin, 432

Anabolism, 8

557

558

INDEX

Anaconda, 314

Anadramous fishes, 263

Anamniota, 302

Anaphase, 501

Anas boschos, 495

Anatomy, 526

Anatomy and Physiology of Birds, 354

Anatomy of lobster, 164

Anaximander, 510

Angel-shark, 228

Angora goat, 405

Anguillulidae, 91

Anguis fragilis, 309

Animal starch, 43 ^

Annelida, 100-120; characteristics, 100;

economic importance, 1 19-120
Annelid Theory, 219
Annulata, 100
Annulated snake, 316
Anophelines, 189, 190, 191
Anseri formes, 339
Antelope, 404, 406
Anthropoid ape, 413
Ant lion, 185
Anti-venin serum, 329
Ants, 197
Anura, 269
Aortic arches, 109
Aphids, 185
Aphrodite, 102
Apoda, 266
Apoidea, 198
Appendix, 430
Aptera, 178
Apteryx, 335
Aquatic mammals, 423
Arachnida, 201
Arachnid Theory, 218
Araneida, 201
Archeopteryx, 370
Archeornis, 371
Archeornithes, 334
Archi-Annelida, 100, loi
Archosauria, 331
Arctic fox, 388
Arctic tern, 366
Arenicola, 104
Aristotle, 510

Aristotle's lantern, 138

Armadillo, 397

Army worm, 186

Arrow poison from toads, 301

Arsenic, 439

Artemia fertilis, 170

Artemia salina, 170

Arterial circulation of skate, 233

Arterial system of salamander, 294

Arteries of cat, 450

Arteries of frog, 280

Arthropoda, 163-219; classification, 163;

characteristics, 163
Arthropod Theory, 218
Artiodactyla, 41, 401
Ascaris lumbricoides, 88, 89
Ascending colon, 433
Asiaric badger, 387
Asiatic buffalo, 407
Asiaric holy apes, 413
Asiatic Wild Ass, 400, 49I
Asp, 318

Aspidium, for tape-worm, 81
Association of the same species, 483
Asterias forbesii, 130, 131
Astylosternus, 291
Atlantic flying fish, 244
Atlantic green turtle, 304
Atoke, 118
Atoll, 66

Atomic weights, See Appendix

Audition, 475

Aurelia, 62

Aurochs, 494

Australian ant-eater, 376

Australian black snake, 319

Australian lung-fish, 252

Australian race, 417

Auto-catalysts, 440

Autolytus, 102

Autotomy, 139

Aves, 334-372; classificarion, 337; fossil rel-
atives, 370; economic importance, 368;
speed of flight, 368; migrarion in, 366

Axis for coral colony, 64

Axolotl, 268

Axone, 473

Aye-aye, 412

INDEX

559

BABOONS, 413

Badger, 387

Badger skunk, 387

Bagg, 540

Balanoglossus, 210

Balanus, 171

Baleen, 428

Baleen whales, 410

Baltimore oriole, 366

Baly, 436

Bankia, 150

Banta, 170

Banting, 445

Barba amarilla, 323

Barbour, 328

Bark lice, 179

Barn owl, 349

Barncacles and colors, 173

Barracuda, 243

Barred owl, 349

Barriers, 490

Basilar membrane, 475

Bataillon, 299

Bateson, 516

Bauhin, K., antedated Linnaeus, 512

Bayer, 29

Bay lynx, 381

Bdelloura, 72

Beaded lizards, 310

Beaks of birds, 356

Bean weevil, 195

Beche de mer, 14I

Bed-bug, 184

Belted king fisher, 350

Beri-beri, 442

Best, 445

Beta hormone, 449

Big-eared bat, 380

Bilateral symmetry, in Echinodermata,
1 40

Bile, 43^

Bilirubin, 457

Binary fission, 26

Binomial nomenclature, Bauhin, 512

Biology, I

Biophors, 518

Bios, 443

Bird-lime, 154

Bird Migration, 366

Bird of paradise, 351

Bird Songs, 363

Birds as insect enemies, 200

Bishop, 268

Bissonnette, 367, 536

Biting lice, 179

Black, D., 417

Black bear, 384

Black duck, 341

Black fish, 411

Black fox, 388

Black-head in turkeys, 29

Black rat, 393

Black-tongue, 443

Black widow spider, 203

Bladder-worm of Cestodes, 79

Blakeslee, 54 1

Blastula, 160

Blattidae, 180

Blind-worm, 309

Blood calcium, 457

Blood Groups, 457

Blood of Camelidae, 457

Blood, of fish, 254; man, 452; snake, 327

Blood platelets, 457

Blue Andalusian fowl, 520

Blue-bird, 352

Blue crab, 175

Boa constrictor, 315

Bobolink, 353

Bob-white, 343

Body louse, 185

Body sensations, 477

Bone, 426

Bonito, 251

Book-lice, 179

Boring sponges, 51

Boron, 440

Bot-fly, 188

Botryllus gouldii, 211

Bowen, 6

Bow fin, 241

Brachiopoda, 127

Bradley, 440

Bragg, 516

Brain, earthworm, 115

Branchinecta packardii, 171

560

INDEX

Branchiopoda, 170

Branchiostoma, 214

Branchipus, 170

Bridges, 539

Brine shrimp, 170

Brittle stars, 135

Britton, temperature extremes, 260

Bromine, 440

Brooks, 3

Brook trout, 243

Brouzas, 418

Brownell, 447

Brown Kodiak Bear, 384

Brown Orang-utan, 413

Brown rat, 393

Brown-Sequard, 541

Brow spot, frog, 273

Brues, 490

Bruno, 511

Brush tongued parrots, 349

Bryozoa, 127

Bubonic plague and rat fleas, 194

Buccal glands, 359

Buckland, toads in stone, 300

Buddha images in mussel, 150

Budding in Coelenterata, 69

Buffalo-moth, 195

Buffon, 512

Bufonidae, 270

Bulbus cordis, 282

Bull-frog, 272

Bull head, 244

Bumble-bees, 198

Burrell, 374

Burrowing owl, 349

Burrows, 495

Bursa Fabricii, 361

Bushmaster, 321

Butcher bird, 353

Butterfish, 21:9

Butterflies, 187

Butterfly wings, color in, 188

Button, of rattlesnake, 327

CABBAGE BUG, 184
Cabbage butterfly, 188
Cacique, 366
Cacpnema radicicola, 91

Caddice fly, 185, 186, 487

Caimans, 309, 326

Calcareous sponges, 47

Calciferous glands, 107

California condor, 347

California ground squirrel, 390, 391

California sea lion, 389

Caligus mutabilis, 172

Camels, 401

Cameos, 152

Canada lynx, 380, 382

Cannibalism of lobster, 168

Cannon, 448

Cantharides, 196

Cape buffalo, 407

Cape viper, 320

Capuchin or "ring-tail" monkey, 412

Carbon, 9

Carbohydrates, 8, 436

Carbon tetrachloride in nematosis, 97

Carcajou, 385

Cardiac muscle, 427

Cardiac stomach, starfish, 132

Care of the young of Reptilia, 327

Carinatae, 334, 337

Carnivora, 380

Carnivorous, 482

Carothers, 505, 506

Carotin, 442, 505

Carpet beetles, 194

Carrel, A., 495

Cartilage, 426

Casselberry, 330

Cassowary, 335

Cat, 491; and birds, 200

Catadramous fishes, 264

Catalysts, 10, 436, 440

Cattalo, 408

Cattle, 494

Cattle tick, 201

Caucasian race, 417

Caudata, 266

Cave-fishes, 244

Cave salamander, 268

Caviar, 24 1

Cecum of snake, 326; of cony, 398; of

cat, 432
Cells and tissues, 424

INDEX

561

Cell division, 500

Cell wall, 5

Centipedes, 177

Central nervous system of lobster, 167

Centrosome, 5

Cephalochorda, 214

Ceratitis capitata, 193

Cercaria, 78

Cerebellum, 469

Cerebral cortex, 469

Cerebral nerves of fishes and amphibia,

290
Cerebro-spinal fluid, 469
Cerebrum, 469
Cetacea, 410
Chaetopoda, 100, loi
Chaetopterus, 103
Chalcid fly, 196
Chalk, 25

Chambers, micro-dissection needle, 502
Chameleons, 313
Chamois, 405
Chandler, A., 98
Characteristics of Craniata, 221
Characteristics of Cyclostomata, 22
Characteristics of skate, 227
Cheeta, 382
Chelonia, 304, 331
Chemical characteristics of protoplasm,

435
Chemical composition of the blood, 455

Chemical elements of protoplasm, 437

Chenopodium for tapeworm, 81

Chevrotain, 401

Chiasmatype, 538

Chief ganglionic categories, 478

Child, axial gradient theory, 83-84

Child families, 486

Chilodon, 35

Chlmaeroid fish, 227, 230

Chimney swift, 352

Chimpanzee, 414

Chinese alligator, 309

Chipmunk, 390, 392

Chlroptera, 379

Chltin, composition of, 205

Chiton, 151

Chlorine, 438

Chlorocruorin, 109

Chloroform and snakes, 329

Choanocytes, 49, 53

Chondrostel, 240

Chordata, classification of, 209

Chromatin diminution, Fogg, 503

Chromosomes, definition of, 7; behavior,

507; maps, 538
Chromatophores, 254
Chrysidoldea, 198
Chrysomelidae, 195
Chyle, 433, 459
Chyme, 430
Cicada, 184
Clllata, 30

Circulatory system, 449
Circulatory system of lobster, 165; Rep-

tllla, 327
CIrcumvallate papillae, 429
Cirripedia, 171
Civets, 383
Cladocera, 170
Clam, 144
Clark, A. J., 498
Clark's zoogenesis theory, 516
Claspers of male skate, 237
Classification, 12-20
Classification of insects, 178
Claws, 428
Claws of birds, 356
Cleavage, 508
Cleavage, frog's egg, 296
Clepslne, 118
Cleveland, 29
Click-beetle, 195
Cliona, 51
Clltellum, 106
Clothes moth, 187
Cobb, 87
Cockatoos, 349
Cockroaches, 180
Cocoons, earthworm, 113
Cocoons, of Planaria, 74
Cod, 251

Codling moth, 186
Cod liver oil, 438
Coe, 86
Coecilians, 266

562

INDEX

Coelenterata, 17, 18, 54-70; characteris-
tics, 54; economic importance, 69-70

Coker, 368

Cold spots, 476

Coleoptera, 194

Cole, 141

Collar cells, 49, 53

Collared peccary, 401

Collateral branches, 473

Colloids, 8, 435

Colloid goitre, 445

Colonies, 483

Coloration of fishes, 253

Color blindness, 474, 535

Color in fossil butterflies, 188

Color of birds, 356

Color resemblance, 488

Colpoda cucullulus, 33

Colubrinae, 315

Colugo, 377

Columbae, 344

Columba livia, 494

Columnar epithelium, 425

Commensalism, 482

Commercial sponge, 48

Common toad, 270, 271

Communities, 489

Comparative anatomy of the portal sys-
tems, 454

Comparison of vertebrates and inver-
tebrates, 209

Compound eyes of Crayfish, 168

Conditioned response, 118

Conepatl, 386

Congo eel, 267

Conjugation, earthworm, 112

Conjugation in paramecium, 33, 34

Conldin, 152, 508

Connective tissues, 426

Contact-odor sense of Crayfish, 167

Coordination, 479

Copeland, 118, 158

Copepoda, 171

Copernicus, 511

Copper, 438

Copperhead snake, 321, 322

Corals, 64, 65, 79

Coral islands, formation of, 65

Coral reef, 6s

Coral snake, 319, 320

Cormorants, 339

Corrodentia, 179

Cort, 93

Cortex, cerebral, 469

Cotton-boll weevil, 196

Cotton mouth moccasin, 321, 322

Cotton spinners, 137

Cottontail rabbits, 395

Cotylosauria, 330

Cowdry, 6

Coyote or prairie wolf, 388

Crampton, 517

Crane fly, 192

Craniata, 221

Crepidula, 152, 508

Crested newt, 267

Cretinism, 445

Crew, F. A. E., 536

Cristatella, statoblast of, 127

Cristispira, 29

Crocodilia, 309

Cro-Magnon man, 416

Crop, 107

Crop, leech, 116

Crop of birds, 359

Crop rotation, 200

Crossing over, 538

Crossopterygii, 240

Cross-section Amphioxus, 213

Crotalus cerastes, 323

Crow, 352

Crustacea, 165, 170

Cryptobranchus, 294

Cryptobranchus, arteries, 294

Cryptobranchus, veins, 293

Cryptocotyle lingua, 78

Crystalline style, 144

Ctenoid scales, 234

Ctenophora, 66

Cuban boa, 315

Cuban toad, 273

Cubical epithelium, 425

Cuckoos, 349

Culex, and bird malaria, 189

Culicidae, 189, 190, 191

Curtis, 82

INDEX

5^3

Curtius, 535

Cutaneous sensibility, 476
Cuticle, 107
Cuvier, 514
Cyanea arctica, 68
Cycloid scales, 254
Cyclops, 96, 171
Cyclostomata, 221, 222
Cyclostomes, 222
Cynthia partita, 211
Cypris, 170
Cytoplasm, 5

DADDY-LONG-LEGS, 201
Danforth, C, 537
Daphnia pulex, 171
Darters, 339
Darwin, C, 119, 515
Darwin, E., 513

Darwin's Pangenesis Theory, 517
Dawson, A. B., 456
Dawson, J. A., 41, 43
Decapoda, 165, 173
Dendrites, 473
Dendrocoela, 72
Dengue, 191
Depth of water, 490
Dermal teeth, 231, 253
Dermis, 427
Desor's larva, 220
Determinants, 518
Detlefsen, 542
Detweiler, 299
Development of Aurelia, 63
Development of backboned animals, 530
Devonian Age, 264
De Vries' " Mutations-Theorie," 524
Diadem spider, 203

Diagram of animal sperm, 463; matura-
tion, 505
Diamond back rattlesnake, 323
Diamond back terrapin, 305
Dichorial twins, 535
Dictophyme renale, largest nema, 92
Diffusion, 5

Digestion in the Ruminant, 433
Digestive system, 428
Digestive system of birds, 359

Digestive system, grasshopper, 183

Digestive system of lobster, 165

Digestive system of skate, 232

Digitalis and amphibia, 301

Digitigrade, 422

Dihybrid, 521

Dinobryon, 28

Dinosauria, 331

Diopatra, 102, 103

Diphycercal tail, 255

Diploid, 503

Dipnoi, 250

Diptera, 188

Direct cell division, 500

Discoidal, 508

Dispersal of small forms, 482

Dissected grasshopper, 182

Distribution, earthworms, 117

Dobson fly, 185

Dodds, G., 171

Dodos, 344

Dog, 491

Dogfish, 225

Dogs (domestic), 388

Doliophis, 319

Dolley, D., 479

Dolley, W., 193

Dolphin, 410

Domesticated reindeer, 403

Domestication of animals, 491

Domm, 444

Do mother snakes swallow their young?,

329
Donkeys, 491
Doodle bug, 109
Dormouse, 394
Dorsal hearts, 109
Dorsal pores, iii
Dorsal view of dogfish brain, 238
Dourine, 29
Draco volans, 311, 312
Dracunculus medinensis, 96
Dragon flies, 179
Drosophila melanogaster, 192
Drum-fish, 253
Duck, 339, 495
Duck-bill, 374
Du Chaillu, 414

5^4

INDEX

Ductus botalli, 294, 450
Dugong, 409
Dyads, 504, 505
Dytiscidae, 194

EAGLE RAYS, 227

Earthworm, cross section, 114

Earthworm, internal anatomy, 108

Earwigs, 180

Ecaudata, 269

Ecdysis, 205

Echinodermata, 129-141; economic im-
portance, 141; characteristics, 130;
classification, 129

Echinorhynchus gigas, 96

Ecology, 3

Economic gain from crayfish, 169

Economic importance, amphibia, 300

Economic importance of Amphioxus, 216

Economic importance of birds, 368

Economic importance of fishes, 261

Economic importance of Porifera, 51-52

Economic importance of Reptilia, 332

Economic importance of Tunicates, 213

Economic importance, starfish, 135

Economic loss from crayfish, 169

Ectoderm, 55, 58, 509

Ectoparasites, 483

Edema, amphibian, 274

Edentata, 396

Edible birds' nests, 365

Edwards, Vinal, 297

Eels, 245

Effects of parasitism, 483

Egg case of skate, 237

Eggs of humming bird, 351

Egyptian wild cat, 382

Eider duck, 340

Eigenmann, cave fishes, 244

Elapine snakes, 317

Elasmobranchii, 225

Electric eel, 260

Electric ray, 227

Electropaxes, 230

Elephant bird, 335

Elephantiasis, 95

Elephants, 398, 399

Elephant seal, 389

Elephas Africanus, 399

Elephas Indicus, 399

Elytra, 102

Embryology of pond snail, 160

Embryology of the barnacles, 173

Empedocles, 510

Emu, 335

Emys europaea, 306

Enchytraeus albidus, 105

Encystment, 43

Endocrine glands, 10

Endoderm, 55, S8, 509

Endo-parasites, 483

Endosecretory glands with a duct, 444

Endosecretory glands without a duct, 445

Endostyle, tunicate, 212

Enemies of lobster, 168

Engle, 448

Ensis, 149

Entameba buccalis, 27

Entameba histolytica, 26

Entameba intestinalis, 26

Enterokinase, 432

Entomostraca, 170

Environment, 499

Enzymes, 10, 440

Eoanthropus dawsoni, 416

Eohippus, 491

Epeira, 202

Ephemerida, 179

Ephestia, 503

Epidermal sense organs, 115

Epidermis, 427

Epigenesis, 509

Epiphysis, 448

Epithelium, 424

Epitoke, 118

Equatorial plate, 501

Equilibrium of crayfish, 168

Equus, 491; caballus fossilis, 491; prze-

walski, 491
Erythrocytes, 456
Esophageal papillae, 326
Esophagus, 430

Eugenics, 544; Record Office, 545
Euglena, 28
Eugyra, 211
Eumenidae, 197

INDEX

56s

Euplexoptera, 180
European badger, 387
European "green lizard," 310
European hookworm, 93; red deer, 403;

wild boar, 494
Evidence from comparative anatomy, 526
Evidences for evolution, 525
Evisceration in sea cucumber, I40
Evolution, 3, 525
Evolution of the horse, 526
Examples of Mendelian inheritance in

man, 523
Excretory system, 166, 363, 461
Excretory system of Reptilia, 327
Exophthalmic goitre, 445
Eyes, of leech, 117

FAIRY SHRIMP, 170
False coral, 127
False coral snake, 319
Fangs, rattlesnake, 321
Fascia, 275
Father families, 486
Fatigue in the nerve cell, 479
Fats, 9, 436
Fat-tail sheep, 404
Feathers, 355
Fer-de-l.ance, 322
Ferret, 385, 386
Fertilization, 505, 506
Fibrillar theory, 8
Fibro-cartilage, 426
Fibrous tissue, 426
Field mouse, 394
Fierasfer, 259
Fig-wasp, 196
Filaria bancrofti, 95
Filaria perstans, 95
Filiform papillae, 429
Finger prints, 535
Finger sponge, 48
Fire-toad, 270
First polar body, 505
Fischer, 495
Fish, 224-264
Fish ducks, 340
Fissipedia, 380
Fitness to survive, 10

Flagellates, 27
Flamingoes, 340
Flatfishes, 249
Fleas, 194
Flesh-fly, 188
Flicker, 350
Flint, 25, 52
Floated oysters, 150
Florida manatee, 409
Flow of lymph, 460
Fluorine, 438
Fly-catcher, 352
Flying dragon, 311
Flying foxes, 379
Flying frog, 272
Flying mammals, 423
Flying squirrels, 390, 392
Fly-wing, vibration of, 188

Fogg. S°3
Follicle mite, 201

Food of the lobster and crayfish, 168
Foraminifera, 25
Fossil Coelenterata, 68
Fossil man, 415
Fossil Nemas, 98
. Fossil relatives of birds, 370
Fossil sponges, 52
Fossils classified, 525
Four day chick embryo, 372
Four-eyed fish, 258
Fowls, 494
Fox bats, 379
Free-martin, 536

Freezing and resuscitation of fishes, 260
Friedmann, the cowbird, 486
Frigate birds, 339
Frog, arteries, 280; brain, 288; heart, 282;

muscles, 276
Fruit bats, 379
Fruit flies, 193
Functions of the blood, 457
Function of Zoology, i
Fundulus heteroclitus, female, 246
Fungi-form papillae, 429

GABOON VIPER, 320
Galapagos penguin, 338
Galen, 511

S66

INDEX

Gall flies, 197

Gall gnats, 192

Gallinae, 343

Gallstones, 432

Gallus banklva, 454

Galton's Law of Ancestral Inheritance,

519
GaltsoflF, 145

Gamble, 105

Gambusia affinis, 245

Gametogenesis, 503

Gannets, 339

Ganoid scales, 241, 253, 254

Ganoin, 254

Gape-worm, 92

Gar pikes, 24I

Gases, as repellents, 199

Gastric juice, 431

Gastric mill, 165, 173

Gastric pouches, Aurelia, 62

Gastrula, 160

Gates, R. R., 521

Gavial, 308

Ga vials, 309

Geckos, 310, 311

Geese, 339, 495

Gemmules, 50

Genes, 7, 440, 538

Genital pore, leech, 116

Genotypes, 521, 538

Geoduck clam, 149

Geographical distribution, 489

Geranium and Japanese beetle, 200

Germ cells, 423

Germinal elements, 509

Germinal epithelium, 425

Germinal layers, 297, 508

Germplasm, 499

Ghost crab, 176

Giant fibers, 115

Giant leech, 118

Giant tortoise, 304

Giant water bug, 184

Giardia muris, 29

Gibbons, 413

Gila monster, 310

Gills, clam, I45; crayfish, 166

Giraffes, 404

Gizzard, 107, 359

Glacier bear, 384

Glands, 425

Glandular epithelium, 425

Glaser, echinoderms, 138

Glaser, heart and pulse frequency, 449,

498
Glass snake, 310
Glochidium, 146, 147
Glycogen, 8,431,444
Glycosuria, 448
Goats, 494
Goby, 247
Goffin, R., 297
Goiter, 445
Goldberger, 443
Golden eagle, 345
Golden pheasant, 343
Gold-fish, 244
Golgi apparatus, 6
Goldschmidt, R., 532
Goldschmidt's enzyme theory, 534
Gonads, of Aurelia, 62
Good ale, 444
Goodrich, H., 508
Goose fish, 249
Gordiacae, 96
Gorillas, 4I4

Gower's muscular atrophy, 535
Grantia, 49
Granular theory, 8
Grave, B., 151
Gray, Geo. M., 298
Gray marmot, 390
Gray rami communicantes, 474
Gray wolf, 388
Great ant eater, 396, 397
Great Auk, 337
Great bustard, 341
Great crowned pigeon, 344
Great horned owl, 349
Great musk shrew, 377
Great white shark, 225
Grebe, 337
Greene, 135
Green frog, 272
Green-glands of lobster, 166
Green lizard, 310

INDEX

567

Green turtle, 304
Gregariousness, 484
Gregory, W. K., 219
Grey, Z., 247
Grizzly bear, 384, 385
Ground beetle, 194
Ground hog, 390
Ground spiders, 202
Group of ratite birds, 336
Guano, 368
Gudernatsch, 445
Guinea worm, 96
Guljar, 494
Gulls, 338

Gustatory sense, 476
Guyer, M., 542
Gyrinidae, 194

HADDOCK, 251

Hag-fishes, 222

Hague, 139

Hair, 428

Hair-necks, 93

Hairworm, 96

Hake, 250

Halibut, 251

Hammerheaded bat, 379

Hanson, 541

Haploid, 503

Hares, 396

Hargitt, C, 70

Harlequin snake, 320

Harp seal, 389

Harrison, R. G., 299, 495, 54I

Hartman, 447

Harvey, W., 512

Harvey, E. N., animal light, 261

Haversian canal, 426

Hawks-bill turtle, 304

Head fish, 247

Head kidney, 258

Heads of coral snake and rattler, 321

Hearing in aquatic mammals, 475

Hearing of crayfish, 167

Heart, 452

Heart beat of the frog, 285

Heart of pigeon, 362

Hectocotylized arm, 156

Heidelberg jaw, 415

Heilbrunn, 138; viscosity of protoplasm,

502
Heliozoa, 25
Hell-bender, 267
Helminthicides, 97
Hematokonia, 456
Hemichorda, 210
Hemlptera, 184
Hemolysis, 457
Hemophilia, 120, 535, 543
Hen-feathering in the Seabright Bantam,

537
Hen's egg, 372
Hepatic portal system, 234
Herbivorous, 482
Herding ants, 484
Heredity, 499-545
Hermaphroditism, in Turbellaria, 82; and

free-martin, 536
Hermit crabs, 175
Herons, 340

Herrick, C. J., 472, 474
Herrick, F. H., 346
Herring, 244
Hesperornithiformes, 371
Hess, 112
Hesperornis, 371
Hessian fly, 192
Heterodera schachtii, 91
Heterotricha, 30
Hexapoda, 177
Hexylresorcinol, 97
Hibbard, 6
Hibernation and aestivation in animals,

480
Hind limb bones of dog, sheep and horse,

527

Hippopotamus, 401
Hirudin, 116
Hirudinea, 100, 115
Hirudo medicinalis, 115
Histology, 423
Histology of hydra, 58
Histology, stomach, 278
Histomonas meleagridis, 29
History of the evolutionary idea, 509
Hoactzin, 371

568

INDEX

Hodge, W,, 97

Hodge, C. F., 479

Hog, 401

Holocephali, 227

Holostei, 241

Holotricha, 30

Homo diluvii testis, 300

Hog- nosed snake, 316

Homing pigeons, 344

Homing instinct, 418-419

Hominidae, 415

Homoptera, 184

Honey, 198

Honey-bag, 205

Honey-bees, 198, 199

Hooded seal, 389

Hooker, 515

Hoppe, E., 496

Horn-bills, 350

Horse-hair worms, 96

Horned rattlesnake or sidewinder, 325

Horned toad, 311

Horned viper or asp, 320

Horny sponges, 47

Horse, 400, 491, 526

Horse-fly, 188

Horse-shoe crab, 203

House-fly, 188

Howling monkey, 412

How long can mammals submerge?, 461

Hubrecht and the pilidium, 220

Hudson seal, 394

Human embryo at six weeks, 464

Human ear, 476

Humming-bird, 350, 351

Hurst, 45

Huxley, J., 54a

Huxley, T., 516

Hyaline cartilage, 426

Hydra, 55

Hydrogen, 9

Hydroids, 58

Hydrophinae, 317

Hydrozoa, 54

Hyena, 383

Hylidae, 270

Hymenoptera, 196

Hypersecretion of the thyroids, 445

Hypodermis, 107
Hypophysis, 448
Hypotricha, 30
Hyracotherium, 491
Hyrax, 398

IBEX, 405, 406
Ibis, 340

Ichneumonidae, 197
Ichthyopterygia, 331
Ichthyornis, 371
Idants, 518

Identical vs. fraternal twins, 535
Idioblasts, 518
Ids, 518

Immigration, 545
Inbreeding, 544
Incurrent pores, 50
Indian buffalo, 407
Indian rat snake, 315
Indirect cell division, 500
Infra-red, 44I
Infusoria, 30

Inheritance of acquired characters, 539
Inheritance of disease, 542
Inheritance through the germinal sub-
stance, 543
Inheritance of weakness, 543
Insecta, 177
Insecticides, 199
Insectivora, 376

Insulin, fishes, 256; mammals, 445
Internal anatomy of spider, 202
Internal organs, frog, 277
Internal view, heart, 282
Invertebrates versus vertebrates, 210
lodin, 439

lodin, in parthenogenesis, 139
Iron, 440

Irradiated ergosterol, 443
Isopoda, 173
Isoptera, 179

JACKALS, 388
Jack hare, 396
Jaguar, 380, 381
Janssens, 538
Japanese beetle, 195

INDEX

569

Java ape-man, 415
Javelin bat, 379

Jay, 352

Jejunum, 430
Jerboa, 395
Johnston, J. B., 472
Jollos, 542
Jones, 114

Jumping mice, 394, 395
June bug, 195
Just, 138

KAMM, O., 449

Kammerer, 541

Kangaroos, 376

Katabolism, 8

Katydids, 180

Keber's organ, 146

Kendall, 445

Killer "whale," 410

Kinaesthetic sense, 477

Kindred, J., 141

King cobra, 318

King crab, 203

Kingfisher, 350

King snake, 316

King vulture, 347

K^iwi, 335

Knutti, R., 45

Kofoid, 27

Kohler, 421

Kommodo lizard, 312

Krait, 319

Kiilpe's classification of sensations, 474

LACERTILIA, 309

Lace-winged flies, 185
Lacteals, 433, 459
Lady-bird beetles, 194
Lake trout, 243
Lamarck, 513
Lamarck's four laws, 514
Lampreys, 223
Land leeches, 117
Landsteiner, 458
Langdon, 115
Lanugo, 429
Large intestine, 433

Large mouth black bass, 248

Larval ascidian, 212

Lateral line organs, 239

Lateral neural blood vessels, 1 1 1

Lateral view of Amphioxus, 214

Law of segregation, 521

Leaf-nosed bats, 379

Leaf-rollers, 186

Leopard, 381

Leathery turtle, 304

Lecane inermis, eggs of, 125

Lecithin, 436

Leeches, 115

Leishmaniasis, 29

Lemmings, 394

Lemurs, 412

Leodice, 102

Leonard, 97

Lepas, 171

Lepas anatlfera, 172

Lepidonotus, 102

Lepidoptera, 186

Lethal factors, 539

Leucocytes, 456

Lewis, 299, 497

Leydig's duct, 289-295

Ligula, 83

Lillie, 139

Limestone pyramids, 25

Limicolae, 34I

Limnoria, 174

Limulus, 203, 204

Linin, 5, 7

Linnaeus, 2, 512

Linton, E. 81

Lion, 381, 383

Lipase, 431

Lipins, 436

Little, C, 540

Little brown bat, 380

Liver, 431, 444

Liver fluke, 74, 75

Living and non-living matter, 4

Living free, 482

Llama, 402

Loa loa, 95

Lobosa, 25

Lobster, 165

570

INDEX

Locomotion of Ameba, 23; fishes, 253

Locusts, 1 80-1 8 1

Loeb, artificial parthenogenesis, 134, 299

Long-eared owl, 349

Long-eared sunfish, 248

Longevity of amphibia, 497; annelida,
497; arthropods, 497; birds, 496;
coelenterata, 497; fishes, 497; mam-
mals, 496; reptiles, 497

Longhorns, 494

Longipennes, 338

Long-nosed gar, 241

Long snouted Echidna, 374

I-oon, 337

Lubber grasshopper, 180

Lucas, A. M., 460

Lumbricidae, 105

Luna moth, 187

Lure-crops, 91

Lyell, 514, 515
Lymph, 458-460
Lymphatics, 459
Lymph of fishes, 257
Lymphocytes, 456
Lynch, R., 123
Lyre bird, 351

MACAQUES, 413
Macaws, 349
Mackerel, 249
Macrochires, 350
Madreporite, 130
Magnesium, 438
Malacostraca, 170, 173
Malay gavial, 309
Malay tapir, 4C0
Male-determining enzyme, 534
Mallard duck, 341
Mallophaga, 179
Malpighian tubules, 183
Malthus, 10, 514
Maltose, 429
Mammalia, 373-419
Mammalia-physiology, 420-481
Mammals as migrants, 418
Mammoth, 408
Manatee, 409
Mandarin duck, 340

Manganese, 440
Mantis shrimp, 175
Man. vs. the higher apes, 420
Marco Polo's sheep, 494
Marmoset, 412
Marsupialia, 375
Marsupium, I46
Masking, 487
Massasauga, 323
Mastigameba, 7, 45
Mastigophora, 27
Mastodon, 408
Maternal impressions, 543
Mathews, 135
Maturation divisions, 505
Mavor, 540
May-flies, 179
McCarrison, 439
McClendon, 445
McClung, 533
McDowell, 541
Mead, A., 135
Meal moth, 186
Meal worm, 196
Mecoptera, 185
Mediterranean fruit fly, 193
Mediterranean race, 417
Medulla oblongata, 472
Megascolecidae, 105
Melanophores, 254, 487
Meleagris gallopavo, 495
Melia, 175
Mellanby, 439
Mendelian inheritance, 519
Mercaptan, 387
Mermis subnigrescens, 96
Mermithidae, 96
Merostomata, 207
Mesenterial filaments, 67
Mesoderm, 509
Mesoglea, of Hydra, 55, 58
Mesoglea, of sponge, 49
Mesohippus, 491
Mesonephros, 258
Metabolism, 8
Metamorphosis of frog, 296
Metaphase, 501
Metazoa, 4, 13, 46

INDEX

571

MetchnikoflF, 170
Methods of insect control, 199
Metoncholaimus pristiurus, 97, 98
Micellar strands, 518
Mictic rotifera, 125
Midges, 193
Mid-wife toad, 270
Migration in fishes, 263
Migration of storks, 366
Milk snake, 316
Miller, N., 271, 464
Millikan, 440
Millipeds, 177
Mimicry, 489
Mineral salts, 9, 437
Mink, 385
Mitochondria, 6
Mitosis, 501
Mitral cells, 476
Mnemiopsis, a comb jelly, 66
Moa, 335

Mocking bird, 354
Moenkhaus, 506
Mola mola, 249
Mole cricket, 180
Molgula arenata, 211
Molgula manhattensis, 211
Mollusca, 142-162; economic importance,
161; classification, 142; characteristics,

143
Molluscan growth, 160
MoUuscoidea, 127
Monads, 506
Monarch butterfly, 188
Mongolian race, 417
Mongoose, 383
Monitor, 312
Monochorional twins, 535
Monocytes, 456
Monoecious, 11 1
Monogamy, 485
■ Monotremata, 373
Monstrosities in fishes, 54O
Moore, C. R., 444
Morgan, 299, 537, 538
Morphology, 2
Morula, 160
Moss's classification of blood groups, 458

Mother families, 486

Motor nerves, 466

Mouflon, 494

Moulting, in Arthropoda, 205

Mountain ranges, 490

Mourning dove, 345

Mouse lemur, 412

Mouth, 428

Mucous tissue, 426

Mud crab, 176

Mud-eel, 268

Mugger, 309

Mugger crocodile, 309

Mule, 400

Mule deer in velvet, 403

Muller, 540

Mummichogs, 245

Muridae, 392

Murine opossum, 376

Muscles of frog, 276

Muscle substance, 426

Muskellunge, 245

Musk-ox, 406

Musk-rat, 394

Mussel with Buddha images, 150

Mustelidae, 384

Mutation, 524

Mya, 149

Myelination, 479

Myriapoda, 177

Myristic acid, 443

Mytilus edulis, I48

Myxedema, 445

Myxinoids, 222

NAILS, 428

Nais, 104, 105

Naked bat, 379

Narwhal, 410

Nasal mucous membrane, 476

Neanderthal man, 416

Nectar from rhododendron, 199

Necturus, 268

Necturus, branchial vessels, 267

Necturus maculosus, 269

Negative eugenics, 545

Negri bodies, not protozoa, 45

Negroid race, 417

57^

INDEX

Nelson, 144

Nemas, 87-99; characteristics, 87; classi-
fication, 87; longevity, 88

Nemathelminthes, 87

Nematocysts, 54, 55, 57

Nemerteans, 85

Nemertean Theory, 220

Neornithes, 334

Neoteny, 268

Nephridiopore, in

Nereis, loi

Nerve cells, 424

Nerve net in Coelenterates, 67

Nervous system, earthworm, 112; lobster,
166

Nervous system of ascaris, 90; of birds,
364; of mammals, 464-480

Nest and eggs of humming bird, 351

Neuritis optica, 535

Neuroblasts, 495

Neuro-epithelium, 425

Neuroptera, 185

Neurotoxin, 328

Nicotine, and the goat, 481

Nictitating membrane in various animals,

529

Nietzsche's super-man, 515
Nighblindness, 535
Nile goose, 495
Nile monitor, 312
Nine-banded armadillo, 397
Noctiluca scintillans, 27
Noguchi, 328
Non-disjunction, 539
Non-striated, 426
Nordics, 417
Norman, 135
Norris, H. W., 237
North American beaver, 392
North American otter, 385
North American prong-horn, 404
Northern fur seal, 389
Nose monkey, 413
Notochord, 209
Nuclear membrane, 7
Nuclear substance, 5CX3
Nucleolus, 7

Nucleus, 7
Nummulites, 25

OBELIA, 58, 59

Ocelot, 380
Odonata, 179
Odontoglossae, 340
Ogliole, 64

Old World monkeys, 413
Olfaction in the bee, 207
Olfactory sense, 476
Oligotrichida, 30
Omasum, 434
Ommatidia, 168
Onager, 491
Onychophora, 175
Oogenesis, 500, 505
Operculum, 152
Ophidia, 313
Ophiuroidea, 135
Ophryoscolecidae, 30; 482
Opisthoglypha, 316
Opossum, 376
Orb weaver, 202
Orca, 410

Organ of Bojanus, 145

Organ of Corti, 475

Organ formation, 508

Organic sensations, 477

Organs of internal secretion, 444

Organs that man can lose, 480

Orohippus, 491

Oroteidae, 268

Orthoptera, 180

Osborn, H. F., 416, 510

Osburn, R. C, 128

Osculum, 50

Osmotic pressure, 5

Osphradium, 147

Ostia, sponge, 50; grasshopper, 183

Ostracoda, 170

Ostrea, 150

Ostrich, 335

Otocysts, molluscan, 147

Ovaries, 55, ni

Ovary, 444

Ovum of the cat, within the ovary, 462

Owl monkey, 412

INDEX

573

Oxygen, 9

Oxyuris vermicularis, 90

Ox warble attacking man, 189

Oyster, 150

Oyster crabs, 175

Oyster, opened by starfish, 135

PACK RAT, 393

Paddlefish, 240

Painted crabs, 175

Painted terrapin, 305

Painter, T., 534

Palatal folds, of Crocodilia, 326

Paleontology, 525

Palinurus vulgaris, 175

Palolo worms, loi, 102, 1 18

Paludicolae, 34I

Pancreas, 432, 445

Pancreatin, 445

Pangenes, 518

Papanicolau, 54I

Paramecium caudatum, 31; 30-36

Parasites of the Annelida, 118

Parasitic castration, 96

Parasitic egg-laying, 486

Parasitism, 483

Parathyroids, 446

Parental care, in Amphibia, 299

Parent families, 485

Parker, 50, 51

Parker, on senses of fishes, 258

Parmenter, 299

Paroquets, 349

Parrots, 349

Parthenogenesis, 539

Parthenogenesis, in Amphibia, 299; in

Echinodermata, 134, 135
Passenger pigeons, 344, 345
Passeres, 351
Pasteur, i
Patten, W., 218
Pavement epithelium, 424
Pavlov, 542
Pavo cristatus, 495
Payne, N., 490
Peacock, 495
Pea-fowls, 344
Pearl, R., 532, 541

Pearl-oyster, 148

Pecten, the scallop, 147

Pedicel! ariae, 130

Pedipalpi, 202

Pel, 417

Peking skull, 417

Pelicans, 339, 340

Pellagra, 443

Pelodera pellio, 118

Penguins, 338

Pennant's marten, 385

Pennock, S. S., and starling, 368

Peptone, 431

Perches, 247

Pcre de Chaudin, 417

Peridinians, 28

Perihaemal system, 134

Period of gestation, 463

Periosteum, 426

Peripatus, 177

Perissodactyla, 400

Peritricha, 30

Persian lamb, 404

Perspiration, 428

Petrels, 338

Petrified fossils, 525

Petromyzontia, 223

Pfiffner, 447

Phalangidae, 201

Phalaropes, 342

Phenotypes, 521, 538

Philpott, 328

Phoebe, 352

Pholas, 151

Phoronidea, 128

Phosgene and snakes, 329

Phosphorescent organs, fishes, 260

Phosphorus, 438

Photophores, 254

Photosynthesis, 436

Phrynosoma, 313

Phyllobates limbatus, 273

Phyllopoda, 170

Physiological units, 518

Physiology, 3

Physostomous teleosts, 264

Piano playing, speed of, 479

Pici, 350

574

INDEX

Pickerel, 245

Pigeon hawks, 345

Pigeons, 494

Pigeon's milk, 359

Pigment of sponges, 48

Pigmy rattlesnake, 2-3

Pigs, 494

Pike, 245

Pilidium, 85, 220

Pilot black snake, 316

Piltdown man, 416

Pineal body, 448

Pine marten, 385

Pine mouse, 394

Pinnipedia, 389

Pin-worm, and appendicitis, 90

Pipa, 269

Pipe fish, 246

Pipe-moss, 52

Piranha, 243

Pisces, 224-264; classification, 224; char-
acteristics, 224; economic importance,
261-263; migration, 263; fossil rela-
tives, 264

Pithecanthropus erectus, 415

Pituitary body, 448

Pit vipers, 321

Placenta, 303

Placoid scales, 253

Placuna placenta, 150

Planaria, 72

Plant eating beetle, 195

Plantigrade, 422

Plant-lice, 185

Plants and animals, 12

Plasomes, 518

Plastids, 6

Platyhelminthes, 17, 18, 71-84; charac-
teristics, 71

Platypus, 374, 375

Plecoptera, 179

Pliny the Elder, 511

Plough, 540

Plover, 342

Plural genes, 538

Podophyra, a suctorian, 35

Poison glands, fishes, 254

Poison of female mosquito, 191

Poisonous Amphibia, 300

Poisonous honey, 199

Poisonous reptiles, 328

Poisonous spiders, 203

Polar bear, 384

Pollock, 251

Polyandry, 485

Polycirrus, blood-worm, 104

Polydon, 240

Polygordius, loi

Polygyny, 485

Polynoe, 102

Polypterus bichir, 240

Polyspermy, 506

Porcupine fishes, 247

Porifera, 17, 18,47-53

Porocytes, 50

Porphyrin, 109

Porpoise, 410, 411

Portal circulation, 454

Portal system, 453, 454

Portuguese Man of War, 60, 61

Positive eugenics, 545

Potassium, 438

Potato beetle, 195

Pouched gophers, 394

Prairie-chicken, 343

Prairie dogs, 390, 392

Prawn, 175

Praying mantis, 180

Precious corals, 70

Precipitin reaction, 435

Preformation, 509

Prenatal infection, 542

Prenatal injury, 543

Primary oocytes, 505

Primates, 411

Principles of population, 10

Proboscidea, 398

Processionary caterpillars, 487

Proglottid, 79

Propagation rate in mammals, 464

Prophase, 501

Prostomium, 100, 106

Protective resemblance, 488

Proteins, 8-435

Proteroglypha, 317

Protohippus, 491

INDEX

575

Protoplasm, 4, 7, 8, 9, 10
Protoplasm, chemical elements, 9
Protoplasm, properties, 8
Protoplasm, structure of, 7
Protozoa, 17, 21-46; characteristics, 21;

economic importance, 46
Proventriculus of birds, 359
Przibram, 539
Pseudopodia, of Hydra, 57
Pseudopodia, of protozoa, 7, 22
Psittaci, 349
Psychic cells, 469
Ptarmigans, 344
Ptyalin, 429
Puff adder, 320
Puffer fish, 248
Pulse, 453

Pulse frequency, Glaser, 498
Puma, 380

Purple death adder, 319
Purple martins, 354
Pycnogonida, 203
Pygopodes, 337
Pyloric cecae, 256
Pyloric ceca, starfish, 132
Pyloric sphincter, 430
Pyloric stomach, starfish, 132
Pyralidina, 186
Pyramidal cells, 469
Python, 314

QUAGGA, 400
Quanta in biology, 539

RABBITS, 395, 494

Rabies, 45

Raccoon, 383

Race mixture and the evolution of man,

418
Races of man, 417
Radial nerve of starfish, 135
Radiolaria, 25
Radula, of gastropods, 158
Rails, 34I
Rana goliath, 273
Rana pipiens, 273-291
Rand, H. W., spiracles, 231
Ranidae, 271

Ratitae, 334, 336

Rat-tailed larva, 193

Rattle of the rattlesnake, 327

Rattler preparing to strike, 324

Ray, J., 512

Rays, 229

Rectal ceca of birds, 360, 361

Rectal gland, 231

Rectigrade, 423

Rectum, earthworm, 109

Rectum of birds, 360

Red ant, 197

Red coral, 64

Red fox, 387

Red-bellied terrapin, 305

Red-headed woodpecker, 350

Redi, I

Red kangaroo, 376

Red mite, 201

Red pocket gopher, 395

Red sponge, 48

Red squirrel, 391

Red wolf, 388

Reduction division and sex determination,

508
References on animal coloration, 489;

animal relationships, 487; birds, 369;

bird songs, 363; endocrines, 449;

ruminant stomach, 434
Reflex arc, 478
Reflex action, 479
Regal python, 314
Regeneration in Annelida, 119
Regeneration in Hydra, 68
Regeneration in Planaria, 83
Remoras, 247

Renal portal system of skate, 234
P.ennin, 431

Reproductive system, cat, 462
Reproductive system of birds, 363, 364
Reproductive system of lobster, 166
Reproductive system of reptilia, 327
Resistance of amphibia to poisons, 301
Respiration, amphibian, 285; cat, 460;

fish, 253; insect, 206; bird, 362; lobster,

166; reptile, 326
Reticulum, 433
Reticular theory, 8

576

INDEX

Reticular tissue, 426

Retractor bulbi muscles, 293

Rhabditis, alternation of generations in,

90
Rhabdocoela, 72
Rhea, 335
Rhinoceroses, 4C0
Rhinoceros beetle, 195
Rhodeus amarus, 247
Rhomaleum micropterum, 180
Ribbon snake, 315
Richards, conduction of nerve impulse,

159
Riddle, O., 532, 537

Right whales, 410

Ringed gecko, 311

Ringhals, 319

Ring necked snake, 316

Robber crabs, 175

Rock borer, 151

Rock crabs, 175

Rock pigeon, 344

Rock wallabies, 376

Rocky mountain bighorn, 405

Rocky mountain goat, 405

Rodentia, 389

Rotifer, 122

Rowan, 367

Royal jelly, 198

Royal purple, 152 1

Roxas, 537

Ruffed grouse, 343

Rumen, 433-434

Russell's viper, 320

Ruthven, 315

SABELLARIA, 118

"Saber-tooth" cats, 380

Sacculina, 172

Sacred African crocodile, 309

Sacred beetle, 195

Sagartia, 68

Sailfish, 251

Saki monkey, 412

Salamandrinae, 267

Salientia, 269

Salivary glands, 428-429

Salmon, 242

Salpa cabotii, 211

Salt water crocodile, 309

Sampson, 138

Sand collar snail, 153

Sandhill crane, 341

Sand natter, 320

Sandpipers, 343

San Jose scale, 185

Santonin, 97

Sarcodina, 22

Sauropterygia, 331

Saururae, 370

Sawfish, 227

Scab parasite, 201

Scale insects, 184

Scales of fishes, 2S4

Scallop, 1 49

Scarlet king snake, 316

Schistosoma, 77

Schroder, 54I

Scolex, 79

Scolopendra, 177

Scorpaenoid fish, 257

Scorpion flies, 185

Scorpionidae, 201

Scott, E. L., 445

Scutigera forceps, 177

Scyphozoa, phosphorescence in, 61

Sea anemone, 63

Sea basses, 247

Seabright bantam, 537

Sea-cucumber, 137

Sea egg, 137

Seahorse, 247

Sea lizard, 312

Sea slug, 137

Sea snake, 317

Seasonal mateships, 485

Sea squirt, 213

Sea urchins, chiseling rocks, 136

Second polar body, 500, 505

Secretary birds, 348

Secretory granules, 6

Segregation, 545

Selachii, 225

Seminal receptacles, iii, 113

Sense of smell in birds, 365

Sense organ, Arthropoda, 207

INDEX

577

Senses of crayfish, 167

Senses of fishes, 258

Senso, from toadskins, 301

Sensory nerves, 466

Serpula, 104, 118

Sertularia, "air-plant," 69

Sesamoid bones, 426

Setae, 106

Seventeen year locust, 184

Sex determination, 531

Sex determining chromosome, 533

Sex in Cladocera, 170

Sex-linked characters, 535

Sexual dimorphism, Triton, 267

Sharks, 225

Sharks of various types, 226

Shark suckers, 250

Sharp-shinned hawk, 345

Sheep brain, ventral view, 468

Sheep, 494

Shelford, herring sensitivity, 260

Short-nosed sturgeon, 241

Short-tailed shrew, 377

Shrews, 377

Shrike, 353

Shrimp, 175

ShuU, 123

Sidewinder or horned rattler, 325

Significance of the Darwinian theory, 517

Siliceous sponges, 47

Silicon, 438

Silk- worm moth, 187

Singing earthworms, 115

Siphonophora, 60, 61

Sirenia, 409

Sirenidae, 268

Skate, 227

Skate sucker, 118

Skeleton of birds, 357-358

Skeleton of Cistudo, 306

Skeleton of garden toad, 292

Skeleton, of gorilla, 415

Skin, 427

Skinks, 312

Skin of fishes, 253

Skull of the cat, 466

Skunk, 387

Slave making ants, 197, 484

Sleeping sickness, 29

Slime tube, earthworm, 113

Sloths, 397

Smallest adult snake, 323

Smallest lizard, 312

Small intestine, 430-359-360

Smell and taste of crayfish, 167

Smilodon, 380

Smith, H., 236

Smith, P. E., 448

Smoky shrew, 378

Smooth muscle, 426

Snake tongue, 326

Snapping turtle, 304

Social life of animals, 482-489

Societies, 485

Sodium, 438

Soft shell clam, 149

Soft-shelled turtle, 305

Solitary wasps, 197

Somatic cells, 423

Somatic sensory, 466

Somatoplasm, 499

Sound producing organs of drum-fish, 253

Sound production, fishes, 253

South American lung-fish, 252

South American tapir, 400

Spade-foot toad, 270

Spanish mackerel, 251

Sparrow, 353

Sparrow hawks, 345

Spectacled cobra, 317

Speed of flight, 368

Speidel, 479

Spermaries, 55

Spermatheca, 184

Spermatogenesis, 503

Spermatogonia, 500

Spermatophores, earthworm, 113

Sperm whales, 410

Spicules, 47, 49. 51. 5^

Spider crab, 176

Spider monkey, 413

Spinal cord, 472

Spinal nerves, 467

Spiny ant-eater, 373, 374

Spiracles, 183

Spiral valve, 255

/^'

578

INDEX

Spireme, 501

Spleen, 460

Sponge, 50

Sponge fisheries, 52

Sponges, characteristics, 47; classification,

47; pigment of, 48; symmetry of, 48
Spongilla, 50

Spontaneous generation, I
Spoonbill, 341
Sporocysts, 75
Spotted salamander, 268
Squamata, 309
Squash bug, 184
Squirrel monkey, 412
Squirrels, 390
Stalked barnacles, 172
Starfish, 131
Star-nosed mole, 378
Static sense, 476
Statistics of vitality, 480
Statoblasts, 49, 50
Steganopodes, 339
Stegocephalia, 300
Stegomyia fasciata, 192
Steinach, 444
Steller's sea-cow, 409
Sterilization, 545
Stewart, 139
Sticklebacks, 246
Stigmata, 183
Stiles, and hookworm, 93
Stirps, 518
Stockard, 54I
Stomach, 430
Stomach-intestine, 109
Stomach poisons, 199
Stone flies, 179
Storks, 340
Stough, 115
Stratum corneum, 427
Stratum malpighi, 427
Striated muscle, 427
Stridulation, in fishes, 253
Strong, O. S., 289
Strong, R. M., 357
Strongylidae, 92
Structure of the cell, 4-7
Structure of the neuron, 473

Stunkard, 78, 483

Sturgeon, 24I

Sturtevant, A., 538

Suberites domuncula, 52

Subneural gland, 212

Suctoria, 30

Sulphur, 9, 438

Sulphur-bottom whale, 410

Sumner, 542

Sun bitterns, 34I

Sundwall, 495

Superheating flour mill insects, 200

Suprarenals, 446

Surinam toad, 269

Surra, 29

Susceptibility of birds to poison, 365

Susceptibility of mammals to poison, 480

Susceptibility of snakes to poison, 329

Swallow, 354

Swans, 339

Sweat glands, 427

Swift, 311

Swingle, 447

Swordfish, 249

Symbiosis, 482

Symbiosis between termites and protozoa,

29
Symbiosis of Radiolaria, 26
Sympathetic nervous system, 473
Synapsis, 504, 505
Synapta, 137
Synura uvella, 28
Syrinx, 362
Syrphus fly, 193

TABLE OF CEREBRAL NERVES,

470-472
Table of longevity, 496
Table of respiration rates, 461
Taenia solium, 78
Tails of fishes, 255
Takamine, 447
Tamandua, 396
Tapirs, 399
Tardigrada, 204
Tarpon, 242
Tarsi er, 412
Tasmanian marsupials, 376

INDEX

579

Taste buds, 477

Taxonomy, 2

Teeth, 428

Teleostomi, 240, 242

Telophase, 501

Temperature, 490

Temperature in birds, 355

Tennant, 138

Teredo navalis, 151

Termites, 179

Terns, 338, 339

Terrapins, 304

Testis, 444

Tetrad, 446, 504, 505

Texas rattlesnake, 323, 324

Thales, 510

Thamnophis, garter snake, 315

Theories of heredity and evolution, 509

Theories of the origin of vertebrates, 216-

220
Therapsida, 300, 331
Thibetan Yak, 407
Thief ants, 484
Thoracic duct, 433
Thorn-headed worms, 96
Three banded armadillo, 397
Three-toed sloth, 397
Thresher shark, 225
Thrips, 180
Thrombocytes, 456
Thymus, 446
Thyroid, 445
Thyroxin, 445
Thysanoptera, 180
Thysanura, 178
Ticks, 194

Tiedemann's vesicles, 132, 133
Tiger, 381
Tiger beetle, 194
Tiger salamander, 268
Tinamous, 335

Tissue survival outside the body, 495
Toads in stone, 300
Tongue, 429

Tongue in the humming bird, 359
Tongue in the woodpecker, 359
Top minnow, 245
Tortoises, 304

. Toucan, 350
Touch of crayfish, 167
Toxicity of snake venoms, 328
Transmission of an impulse, 477
Treatment of snake bite, 329
Tree crickets, 180
Tree frogs, 270
Trematoda, 74
Trembley, 68, 70
Trepang, 141
Trichinella spiralis, 95
Trichinellidae, 95
Trichinosis, 95
Trichocephalus, 94
Trichocysts, 32
Trichoptera, 185
Trichuridae, 93
Tri hybrids, 522
Trilobites, 207
Trochelminthes, 1 21-126
Trochophore in Annelida, loi
Trochophore larva, of Rotifera, 125
Trochophore, molluscan, 146
Troost's terrapin, 305
Tropic birds, 341
Tropisms, 25
True buffaloes, 407
True crickets, 180
True pigeons, 344
True seals, 389
Trumpeter swan, 339
Trypanosoma gambiense, 29
Trypsinogen, 432
Tse-tse fly, 29
Tubifex, 105
Tubinares, 338
Tularemia, in rabbits, 396; in ruffed

grouse, 343
Tuna, 249
Turacin, 356
Turbellaria, 71, 72
Turkeys, 495
Turkey buzzard, 347
Turtles, 304
Tussock moth, 187
Twins, Lumbricus, 113
Two-humped Bactrian camel, 402
Two-spined stickelback, 246

580

INDEX

Types of families, 485
Types of nests, 365
Typhlosole, 107, 114, I45
Tympanum, grasshopper, 183
Tyrian purple, 152

UHLENHUTH, 445

Ultra-violet, 44I

Ungulata, 397

Unguligrade, 422

Unio gibbosus, 148

Unsaturated fats, 437

Upper surface of the tongue, 477

Urea, 279

Urinogenital system of male bull-frog,

286; female, 287
Urinogenital system of male skate, 235;

female, 236
Urochorda, 211
Urodela, 266
Uroglena, 28

VAMPIRE BATS, 379

Van Beneden, 90

Varanus komodoensis, 312

Vasa efferent! a, 289

Veins, frog, 281

Veliger, 146, 160

Venous circulation of skate, 234; sala-
mander, 295; cat, 451

Ventral view of dogfish brain, 239

Ventral view of nervous system of frog,
289

Venus, the quahog, 144

Vergil and bee culture, 198

Vermiform appendix, 430

Vermilion spotted newt, 267

Verrill, 86, 102

Vertebrate embryos with their mem-
branes, 302

Vertebrate eye, 475

Vesalius, 511, 512

Vespoidea, 197

Vestigial hind limbs of the python, 328

Viperidae, 320

Virginia deer, 402

Visceral sensory, 466

Vision in birds, 364

Vision of crayfish, 167
Vision of fishes, 259
Vischer, J. P., 173
Visual sensations, 474
Vitality, statistics of, 480
Vitamins, 10, 44I-443
Voice box of birds, 362
Voice of Reptilia, 327
Voices of mammals, 461
Vocal sacs of frog, 285

WALKING STICKS, 180

Wallace, A. R., 516

Wall lizard, 310

Walrus, 389

Wandering albatross, 368

Wanderoo, 4 13

Warbler, 354

Ward, 99

Warm spots, 476

Wasps, 197

Water-borne goitre, 445

Water fleas, 170

Water moccasin, 321

Water shrew, 377

Water snakes, 315

Water- tiger, 194

Water vascular system, starfish, 132, 133

Weasel, 385

Weight of the brain, 477

Weights and measurements. Appendix

Weismann, A., 518

Wells, 88

West India Boa, 4, 314

Whale sharks, 225

Wheat germ oil, 444

Whirligig beetle, 194

White Ass, 400

White breasted nuthatch, 354

White fish, 242

White-lipped peccary, 401

White rami communicantes, 474

White whale, 411

Whitney, 124

Why birds migrate, 367

Wild banteng, 494

Wild boar, 401

Wild ox, 406

INDEX

581

Wild turkeys, 343

Willier, 536

Willmer, 495

Wilson, 8, 171

Wilson's snipe, 343

Window-glass shell, 150

Winds, 491

Wisent, 406

Wolverine 385, 386

Wood-boring ship worm, 150

Woodchuck, 390

Woodpecker, 350

Wood rat, 393

Wood terrapin or turtle, 306

Woodthrush, 352

Woodward, 138, 139

Worm snake, 314

Wren, 354

X-CHROMOSOME, 534
Xerophthalmia, 44I
Xiphidium, 533

Y-CHROMOSOME, 534

Yellow algal cells, 26

Yellow-bellied sapsucker, 350

Yellow bellied terrapin, 305

Yellow cells, of earthworm, 107

Yellow-fever mosquito, 192

Yellow hammer, 350

Yellow jackets, 197

Yellow perch, 252

Yerkes, 421

Yolk granules, 5

Young brown thrashers, 353

Young Cooper's hawk, 347

Young fawn in mountain laurel, 488

Young nymph of May-fly, i79

ZEBRA, 400
Zebu cattle, 407
Zinc, 440
Zoogeography, 3
Zoonerythrin, 48

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