640 



ANIMAL BIOLOGY 



Physiological state, 57, 74, 142, 165, 239, 499, 501 



Physiology, 5, 486, 582-583 



Pia mater, 375 



Pig, embryo, 548 

 foot bones, 436 



Pigeons, 418, 422 

 anatomy, 407 

 limb skeletons, 404 



Pigment cells, 356, 365 



(See also Chromatophores; Eyespots) 



Pigment layer, eye, 338, 339 



Pigment spots, 151, 201, 320 



Pike, scale, 353 



Pilidium, 187 



Pill bugs, 266 



Piltdown man, 453 



Pincer, 255 



Pine marten, 537 



Pineal body, eye, or gland, 343, 346, 367, 376, 399 



Pinna, 336, 424 



Pinnipedia, 436 



Pisces, 340, 350-364 

 (See also Fishes) 

 Pit vipers, 398 

 Pithecanthropus, 452 

 Pituitary body or gland, 408, 492, 493 

 Pituophis sayi, head, 390 

 Place of origin, 528 

 Placenta, 430, 444-447 

 Placoid scale, 344, 345, 353, 354 

 Planaria maculata, 169 

 Planarians, 159-165, 478, 491, 494 

 Planes of metabolism, 483 

 Plankton, 358, 506, 511 

 Plant galls, 291 



Plant Hce, 107, 289, 290, 491-492 

 Plantigrade foot, 436 

 Plants, compared with animals, 41 

 contrasted with animals, 42 

 relations to animals, 505 

 Planula, 151, 152 

 Plasma, 236, 330 



membrane, 29, 30 

 Plasmagel, 65, 66 

 Plasmalemma, 63, 65, 66 

 Plasmasol, 65, 66 

 Plasmodium, 91 

 Plasmodium vivax, 91 

 Plasmosome, 30 

 Plastids, 30, 32 

 Plastron, 400, 401 

 Platyhelminthes, 166, 574 

 Platyhelminths, 166-177 

 (See also Flatworms) 

 Pleasure, 501, 502 

 Plestiodon septentrionalis, head, 390 

 Pleural cavity, 427 

 Pleurohrachia bachei, 156 

 Pliny, 579 



Ploughshare bone, 403 

 Plover, and crocodile, 523 



golden, 418 

 Plumage, 414 

 Plumatella, 192 

 Plumatella repens, 192 



Pneuma, 581, 582 



Pocket mice, 445 



Podophrya, 84 



Poikilothermous animals, 484 



Poison claws, 214, 274, 306 



Poison glands, 303, 387, 398 



Polar bodies. 111, 112, 114, 116, 444 



Polarity, 119, 243, 496 



Poles, egg cell, 120, 378 



Polian vesicles, 197, 209 



Polistotreme stouti, 341 



Pollen, 297 



Polyandry, 419, 521 



Polyaxon spicules, 132, 133 



Polycelis, 167 



Polychaeta, 247 



Polygordius, 246, 247 



Polygyny, 419, 521 



Polymorphism, 149, 160, 152, 298, 299, 459, 672 



Polyps, 144-150, 162, 153 

 compared to madusa, 144 



Polypterus, 350 



Polypterus senegalus, 351 



Polypus bimaculatus, 227 



Pond communities, 507 



Porcupines, 436 



Porifera, 129-135, 573. 575, 576 

 (See also Sponges) 



Porospora, 84 



Porpoises, 441 



Portal systems, 346 



Portal veins, 428 



Portuguese man-of-war, 145, 150, 475 



Position, organs of, 473 



Positive response, 56 



Postembryonic development, 478 



Posterior chamber, eye, 338, 339 



Potassium, 19 



Potato beetle, 290 



Potential energy, 15, 38, 458, 480, 481 



Potential immortality, 97, 479 



Prairie chicken, 537 



Prairie dogs, 535 



Praying mantis, 279 



Precaval vein, 346 



Precocial young, 417, 420 



Predatism, 526 



Preformation theory, 581, 583 



Pressure sensations, 473 



Priapulus caudatus, 262 



Primates, 429, 437 



Primordial germ cells, 109-112, 475 



Priority, 60, 576 



Prismatic layer, 214 



Proboscidea, 441 



Proboscis, 169, 185, 186, 278, 662, 574 



Procoracoid, 400 



Proctodeum, 379, 466 



Proglottid, 169, 170 



Pronephric duct, 323, 331, 332 



Pronephric tubules, 331, 332 



Pronephros, 332, 342, 494 



Pronghorn, 537 



Pronuclei, 114, 116 



