INDEX 



579 



Neuroptera, 252 

 Neutron, 38 

 Newts, 380 

 Nomeus, 126 

 Notochord, 300, 526 

 Nucleoli, 21 

 Nucleus, 19, 21 

 Nuptial flight, bees, 234 

 Nymph, 216 



Obelia, 123 



Octopus, 284 



Odonata, 242 



One-celled animals, 84 



Onychophora, 268 



Oogenesis, 495 



Ophiuroidea, 294 



Opossums, 429, 430, 431 



Orangutan, 454 



Organ, 70 



Organ systems, 71 



Organic compounds, 46 



Organizer, embryonic, 538 



Ornithology, 16 



Orthoptera, 243 



Osmosis, 56 



Osteichthyes, 370 



Ostrich, 419 



Otoliths, 328 



Ovary, 122 



Oviparous reproduction, 369 



Ovoviviparous reproduction, 369 



Owls, 11, 415 



Oysters, 277 



Paleontology, 16, 558 

 Pandas, 437 

 Pangenesis, 490 

 Paramecium, 101 

 Parapodia, 176 

 Parasite, 164 

 Parasite eggs, 165 

 Parasitology, 16 

 Parathyroid glands, 358 

 Passenger pigeon, 466 

 Pathogenic protozoa, 92 

 Peacock, 547 

 Pearl formation, 277 

 Pedicellaria, 290 

 Pelagic zone, 470 

 Pelecypoda, 271 



Pellicle, 101 



Peripatus, 268 



Peristalsis, 170, 330 



pH value, 42 



Phoronidea, 266 



Physalia, 125 



Physical sciences, 9 



Physiology, 15 



Pill bug, 196 



Pinworm, 163 



Pit vipers, 390, 391 



Pitocin, 363 



Pitressin, 363 



Pituitary gland, 362 



Pituitrin, 363 



Placenta, 427 



Planaria, 135 



Plant lice, 251 



Plasma membrane, 19, 51, 55 



Plasmodium, 96 



Plastids, 21 



Platyhelminthes, 134 



Plecoptera, 243 



Poliomyelitis, 6 



Polyp, 123 



Porcupines, 448 



Porifera, 109 



Pork tapeworm, 149 



Porpoises, 443 



Portuguese man-o-war, 125 



Potato beetles, 248 



Praying mantis, 244 



Precocious young, birds, 412 



Predators, 483 



Preformation, 489 



Primates, 449 



Proboscidea, 444 



Proboscis worms, 268 



Progesterone, 362 



Proglottids, 147 



Protective coloration, 130, 371 



Protective mimicry, 222 



Proteins, 49 



Proton, 38 



Protoplasm, 21, 47 



Protozoa, 84 



Protozoology, 16 



Pseudopodia, 85 



Pupa, 215 



Purkinje, 34 



Pyorrhea, 92 



