tion, 141; Discontinuous and continuous variation, 141; Congeni-

tal and acquired variation, 142; Determinate variation, 150; The

causes of variation, 154, 156; Variation as related to amphimixis

and parthenogenesis as mutations of de Vries, 154.

CHAPTER X.-HEREDITY.

Hereditary variancy defined, 163; Atavism or reversion, 166;

Telogony, 166; Prenatal influences, 167; Not all transmission is

heredity, 168; Determination of sex, 170; Homologies and analo-

gies, 172; Vestigial organs, 174; Significance of vestigial organs,

181; Heredity and its "laws," 181; Galton's law of ancestral in-

heritance, 184; Mendel's law of alternative inheritance, 187;

Modification of Mendelism, 188.

CHAPTER XI.-INHERITANCE OF ACQUIRED CHARACTERS.

The Lamarckian principles of evolution, 196; Neo-Lamarckism

and Neo-Darwinism, 197; Acquired characters, 198; Effects of use

and disuse, 199; Environmental modifications not inherited, 200;

Examples of non-inheritance of acquired characters, 201; Heredity

unproved, 203; Convergence of characters and parallelism, 204;

Actual effects of environment, 205; Ontogenetic species, 206.

CHAPTER XII.-GENERATION, SEX, AND ONTOGENY.

Generation and ontogeny, 211; Spontaneous generation or abio-

genesis, 212; Simplest modes of generation, 213; Parthenogenesis,

215; Differentiation of reproductive cells, 217; Simplest many-

celled animals, 218; Effects of sex, 220; Sex dimorphism, 221;

The life cycle, 223; The egg, 224; Numbers of young, 225; Em-

bryonic and post-embryonic development, 227; Developmental

stages, 229; Continuity of development, 231; Metamorphosis or

apparent discontinuity, 234; Significance of facts of develop-

ment, 234; Divergence of development, 234; The duration of

life, 240; Death, 241.

CHAPTER XIII.-FACTORS IN ONTOGENY, AND EXPERIMENTAL

DEVELOPMENT.

Processes in ontogeny, 244; Extrinsic and intrinsic factors, 245;

Mechanism versus vitalism, 246; Functions of protoplasm, 247;

Ultimate structure of protoplasm, 248; Theories of organic units,

250; Cell division, 251; Mitosis, or karyokinesis, 252; Somatic and

germ tissues, 257; Reproduction in protozoa, 260; Maturation,

264; Fertilization, 267; Cleavage, 269; Reduction of the chromo-

somes, 269; Preformation versus epigenesis, 276; Examples giving

evidence for each, 278; Mechanism versus vitalism, 281; Artificial

parthenogenesis, 283; Regeneration and regulation, 285.

CHAPTER XIV.-PALEONTOLOGY.

Fossils and thei: significance, 289; Fossil-bearing rocks and

their origin, 292; Geological epochs, 296; Conditions of extinct

life, 297; Divergent types and synthetic types, 299; Parallelism

between geologic and embryonic series, 300; Orthogenesis, 301;

Significance in evolution of the facts of paleontology, 301; Dur-

ation in time of species, 302; History of the vertebrates, 305;

Man, 307.

CHAPTER XV.-GEOGRAPHICAL DISTRIBUTION.

Zoögeography, 309; Relation of species to geography, 311;

Laws of distribution, 314; Species debarred by barriers, 315 ;

Species debarred by inability to maintain their ground, 315;

Species altered by adaptation to new conditions, 315; Effects of

barriers, 316; Faunas and faunal areas, 316; Remains of animal

life, 322; Subordinate remains of provinces, 323; Faunal areas of

sea, 323; Analogies between language and fauna, 325; Geographic

distribution and the theory of descent, 326.

CHAPTER XVI.-ADAPTATIONS.

The principle of fitness and general adaptations, 327; Origin

of adaptations, 327; Types and classification of species adapta-

tions, 328; Adaptations for food-securing, 329; Adaptations for

self-defense, 330; Adaptations brought about by rivalry, 331;

Adaptations for defense of young, 338; Special adjustments to

surroundings, 343.

CHAPTER XVII.-PARASITISM AND DEGENERATION.

Parasitism defined, 347; Kinds of parasitism, 348; Simple

structure of parasites, 350; Gregarina, 351; Parasitic hemospor-

idia: the cause of malarial fevers, 351; Tapeworm and other flat

worms, 354; Trichina and other round worms, 355; Sacculina, 358;

Parasitic insects, 359; Parasitic vertebrates, 361; Parasitic plants,

362; Degeneration through quiescence, 363; Degeneration through

other causes, 363; Immediate causes of degeneration, 366; Ad-

vantages and disadvantages of parasitism and degeneration, 367.

CHAPTER XVIII.-MUTUAL AID AND COMMUNAL LIFE AMONG ANI-

MALS.

Man not the only special animal, 369; Animal societies, 369;

Commensalism, 370; Symbiosis, 373; Symbiosis between animals

and plants, 376; Social life, gregariousness, 380; Solitary and com-

munal bees and wasps, 383; The honey-bee community, 387; Ants,

391; Termites, 394; Division of labor the basis of communal life,

395; Advantages of communal life, 397.

CHAPTER XIX.-COLOR AND PATTERN IN ANIMALS.

Color among animals, 398; Protection by color, 400; Protection

of color, 402; Significance of color and pattern, 404; Table of in-

sect colors, 405; General protective resemblance, 406; Variabie

protective resemblance, 407; Special protective resemblance, 411;

Warning colors, 416; Terrifying appearances, 418; Directive col-

oration, 419; Recognition marks, 420; Mimicry, 421; Criticism and

general considerations of the theory of protective and mimicking

color pattern, 424.

CHAPTER XX.-REFLEXES, INSTINCT, AND REASON.

Irritability, 426; Nerve cells or fibers, 427; Brain or sensorium,

427; Mechanical reflexes, 428; The tropism theory, 429; The

theories of the method of trial and error, 429; Instincts, 430; In-

stincts of feeding, 432; Instincts of self-defense, 433; Instinct of

play, 435; Climatic instincts, 436; Environmental instincts, 438;

Instincts of courtship, 438; Instincts of reproduction, 439; In-

stincts concerned with the care of the young, 439; Variability of

instinct, 442; Reason, 443; Mind, 448.

CHAPTER XXI.-MAN'S PLACE IN NATURE.

Post-Darwinian conception of humanity, 452; Man's place

among the other animals, 453; Classification of the primates, 455;

Evidences from comparative anatomy of man's relation to lower

animals, 456; Special physiological evidence, 457; Evidence from

embryology, 460; Evidence from paleontology, 461; Conclusions

from ethnology, 462; The earliest man, 464 The genealogy of

man, 466; Theology and Darwinism, 467.

CHAPTER V.-NATURAL SELECTION AND STRUGGLE FOR EXIST-

ENCE: SEXUAL SELECTION.

Natural selection the chief determining agent in adaptation, 57;

Adaptation to conditions of life, 58; The crowd of animals, 59;

Reproduction by multiplication, 59; Numbers of individuals al-

most stationary, 60; Struggle for existence, 60; Discriminate

death, 61; Natural selection, 62; Interdependence of species, 63;

Animal and plant invasions, 64; Doctrine of Malthus, 67; Limits

to the capacity of natural selection, 68; Survival of the existing,

69; Actual standing of Darwinism, 70; Secondary sexual dif-

ferences, 71; Classification of secondary sexual characters, 72;

Theory of sexual selection, 75; Criticisms of the theory, 77; The

sexual selection theory largely discredited, 78.

CHAPTER VI.-ARTIFICIAL SELECTION.

Natural selection and artificial selection, 80; Steps in the pro-

duction of new races, 81; Selected traits quantitative, 81; Race

traits qualitative, 84; Hybridization, 88; Plant amelioration, 90;

Work of Luther Burbank, 90; Panmixia, or cessation of selection,

104; Reversal of selection, 104; Transmission and heredity, 105;

Artificial selection and natural selection, analogous processes,

106; Race-forming by sports, 107.

CHAPTER VII.-VARIOUS THEORIES OF

DESCENT CONTROL.

SPECIES-FORMING AND

Segregation of isolation, 108; Geographic and physiologic iso-

lation, 109; Romanes's championship of physiologic isolation, 109;

The Lamarckian theory of species-transformation, 111; Ortho-

genetic evolution, 112; Species-forming by mutation, 114; The un-

known factors of evolution, 115.

CHAPTER VIII. GEOGRAPHIC ISOLATION AND SPECIES-FORMING.

Migration and faunal distribution, 117; Closely related species

not found in the same region, but in contiguous regions, 120; The

American warblers, 120; Barriers, 122; The Hawaiian Drepanidæ,

124; Adaptive and non-adaptive characters, 127; The American

orioles, 128; Species traits not necessarily useful, 129; The persist-

ence of the sufficiently fitted, 130.

CHAPTER IX.-VARIATION AND MUTATION.

Actuality and extent of individual variation, 131; Darwin's

laws of variation, 137; Quetelet's determination that fluctuating
variation follows the law of probabilities, 140; Discontinuous varia-