600 



INDEX 



Hookworm, 179 



Hormones, 431, 433, 452, 464, 473, 521 



Horn, 98 



Hornbills, 507 



Horned toads, 384 



Hornets, 295 



Horns, 53 



Horse, 416, 421, 474, 507, 525 



foot bones, 415 



foreleg, 52 

 Horsehair snake, 181 

 Horseshoe crab, 303 

 Host, 170, 497 

 House centipede, 269-270 

 House fly, 288 



foot, 274 

 Hovering, 398 

 Human parasites, 169, 170, 172, 175, 179-181, 



246, 281, 283, 284, 288, 301 

 Human skeleton, 319 

 Humerus, 319, 321, 361, 388, 391 

 Humidity, 501 

 Hummingbirds, 397, 507 

 Hundred-legged worms, 269 

 Hunger, 445, 501 

 Huronian period, 511, 512 

 Huxley, 517 

 Hyollela, 262 

 Hyallela dentata, 262, 500 

 Hybridization, 106, 522, 531 

 Hybrids, 530, 531. 533 

 Hydatid cysts, 169 



Hydra, 111, 134-141, 143, 151, 429, 444, 496 

 Hydra oligactis, 138 

 Hydra viridissima, 134, 141 

 Hydranths, 150 

 Hydration, 460 



Hydrochloric acid, 65, 322, 461 

 Hydrogen, 18 



Hydrogen-ion concentration, 479 

 Hydroids, 143, 144, 146, 150, 151, 261, 494, 495, 



513 

 Hydrophobia, 555 

 Hydrozoa, 143 

 Hyenas, 413 

 Hygiene, 6, 492 

 Hyla versicolor, 367 

 Hymenoptera, 287, 291 

 Hyoid arch, 375 

 Hypermetamorphosis, 281, 451 

 Hypodermis, 231, 437 

 Hypomere, 450 

 Hypopharynx, 273 

 Hypophysis, 311, 396 

 Hypostome, 134, 136 

 Hyracotherium, 525 



I-beam principle, 393 

 Ibex, 507 

 Ice fish, 356 

 Icerya purchasi, 289 

 Ichneumon flies, 291 

 Ichthyology, 5 



Ichthyophis, 367 



Ichthyosaurus, 446 



Identical twins, 538 



Idiacanthus ferox, 357 



Idiosyncrasy, 489 



Iguanas, 384 



Ileum, 322, 519 



Iliac artery, 339, 409 



Iliac vein, 339, 409 



Ilium, 321, 388 



Imago, 281 



Immunity, 490-^92 



Impulse, nervous, 101 



Inbreeding, 536 



Incisors, 407 



Income and outgo, organism, 430 



Incomplete metamorphosis, 279, 280, 450 



Incubation, 403 



Incurrent canals, 129, 130 



Incus, 330, 331, 410 



Independent effectors, 468, 469 



Indirect response, 56 



Individuality, 130, 432, 453, 489 



Infection, 489-492 



Infusoria, 79, 83-84, 87 



Ingestion, 32-34, 39, 65, 71, 102, 131, 138, 148, 

 161, 168, 177, 196, 230, 246, 298, 311, 312, 

 321, 336, 352-353, 368, 382, 384 



Inheritance, abnormalities, 536 

 acquired characters, 517, 536 

 disease, 488, 537 

 (See also Genetics) 



Inherited immunity, 491 



Ink sac, 222 



Inner cell mass, 419 



Inner chamber, eye, 332, 333 



Inner ear, 330-331, 341, 354 



Inorganic matter, 16 



Insanity, inheritance, 536 



Insect powders, 289 



Insecta, 271, 305 

 Insectivora, 411, 412 



Insects, 111, 118, 271-295, 304, 433, 440, 442, 

 447, 463, 466, 473, 478, 480, 481, 499, 504, 

 510, 514, 537, 539, 540, 552 

 Insertion, muscle, 443 

 Inspiration, 32, 33, 35, 71, 463 



(See also Respiration) 

 Instars, 279 



Instinct, 257, 299, 305, 355, 369, 470-472, 475 

 Integration, 431, 447 

 Integument, 318 

 (See also Skin) 

 Intelligence, 299, 305, 355, 370, 371, 472-475 

 Interaction of genes, 534 

 Interambulacral plates, 203 

 Intercellular differentiation, 93 

 Interlamellar junctions, 211 

 Intermediate hosts, 170 

 Internal gills, 373 

 Internal secretions, 366, 431, 464 

 Internal skeleton, 307, 316 



International Commission on Zoological Nomen- 

 clature, 546 

 Interoceptors, 445 



