754 



Neural arch, 422 

 crests, 639 

 folds, 636, 656, 666 



(medullary) plate, 624, 635, 

 656 

 groove, 635 

 spine, 424 



vessels of earthworm, 167 

 Neurilemma, 513 

 Neurocyte, 506 

 Neurofibrils, 512 

 Neuroglia, 512 

 Neurohumours, 472 

 Neuromast organs, 344 

 Neuron, 511 

 Neuroneme, 48 

 Neuropodium, 176 

 Neuropore, 624 

 Neuroptera, 254 

 Newts, 548 



Nictitating membrane, 389 

 Nipple, 527 

 Nitrogenous w^aste, 8, See also 



Excretion 

 Nodes of Ranvier, 512 

 Nomina conservanda, 707 

 Non-cellular animals, 78 

 Non-disjunction, 698 

 Nostrils. See Nares, external 

 Notidani, 583 

 Notochord of chick, 649 

 of dogfish, 315 

 of frog, 351, 634 

 of lancelet, 302, 624 

 Notonecta, 250 

 Notopodium, 176 

 Notum, 228 



Nourishment of young stages, 670 

 Nuclear division, 688 



membrane, 501 

 Nucleic acid, 501, 699 

 Nuclein, 501 

 Nucleoplasm, 499, 501 

 Nucleus, 15, 4g8, 501 

 Nutrition, holozoic, holophytic, sap- 

 rophytic, 41 

 of Amceba, 26, 31 

 of Paramecium, 48. See also Food. 

 Nuthatch, 721 

 Nyctotherus, 60 

 Nymph, 246 



Obelia, 102, iii 

 hydranth of, 103 

 medusa of, 105, 106, 107 



reproduction of, 106 

 Obturator foramen, 406, 436 



INDEX 



Ocelli, 247 



Occipital condyles, 352, 426. See 



also Skull 

 Octopus. 193, 285 

 Odonata, 250 

 Odontoid process, 424 

 (Esophageal pouches, 162 

 (Esophagus or gullet of cockroach, 

 232 

 of crayfish, 203 

 of dogfish, 223 

 of earthworm, 162 

 of frog, 365 

 of pigeon, 406 

 of rabbit, 440 

 of snail, 267 

 of swan mussel, 276 

 (Estridae, 259 

 (Estrus, 457, 471 

 Offspring, 3 

 Olecranon, 358 

 Olfactory bulb and tract, 460 

 capsules. See Nasal capsules 

 lobes, 336, 387, 415, 460, 608 

 membrane, 534 

 organs of cockroach, 236 

 of crayfish, 215 

 of dogfish, 340 

 of frog, 391 

 of pigeon, 415 

 of rabbit, 469 

 of snail, 269 

 of snake, 593 

 of swan mussel, 28 1 



pit, 307 

 Oligochaeta, 184 



Olynthus, 82, 84, 85 

 Omentum, 324, 420 

 Ommatidia, 213 

 Omosternum, 357, 563 

 Oncosphere, 129 

 Onychophora, 219 

 Oocyst of malaria parasite, 77 

 Oocytes of Hydra, 100 

 Oogamy, 39 

 Oogenesis, 694 

 Ookinete, 73, 77 

 Ootheca, 238 

 Opalina, 81 



ranarum, 60, 61 

 Open circulatory system, 208 

 Operculum, of tadpole, 637 



of fishes, 546 



of nematocyst, 91 



of snails, 266 

 Ophiothrix, 297 

 Ophiuroidea, 297 

 Opisthosoma, 222 



