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 



