INDEX 



Musculature, ql atinclkis, 421 



Mussel, fresh-water, 370, 378, 379, 606; 



marine, 379 

 Mutation.s, 204, 651 

 Mutualism, 291 

 Mya. 379, 380 

 Myelencephalon, 87, 102 

 Myelin sheath, 69 

 Myosin, 27, 1 13 

 Myolis, 584 

 Myriapoda, 478 

 Myiilus, 379 

 Myxine, 555 



Nacre, 379 



Nacreous layer, 377 



Naiads, of dragonflies, 460, 462, 485; of 

 hemimetabolous insects, 455 



Nasal cavity, 48, 60 



Nasal epithelium, 109 



Nasal pharynx, 48 



Nalnx, 571 



Natural sciences, 7 



Natural selection, 611, 636; Theory of, 647 



Nauplius larva, of Branchiopoda, 438 



Nautiloids, 388, 623 



Nautilus, 388, 625 



Neanderthal man, 639, 642 



Neanderthaloids, generalized, 642 



Near-sightedness, 105 



Necalor amencami.s, 352 



Neck, 91 



Nedurus, 214, 328, 377, 564 



Nematocvsts, 285; as independent effectors, 

 289, 523; of hvdras, 289, 290; of Physalia, 

 303 



Nematoda, 216, 348-353 



Nematodes, molting in, 529; parasitic, 351- 

 353; parthenogenesis in, 535; reproductive 

 system, 533 



Nematogen, 270, 271 



Nemertinea, 216, 219, 221, 314, 340-343,341, 

 513, 532 



Neoblasts, 412 



Neognathae, 578 



Neopilina, 394 



Neornithes, 577 



Nephridia, blood supply to, 521; common 

 features of, 519; in relation to coelom, 521; 

 in reproduction of annelids, 533; of anne- 

 lids, 519; of brachiopods, 364; of Branchio- 

 sloma, 552; of crayfish, 432, 433; of earth- 

 worm, 408, 485; of invertebrates, 519; of 

 Nereis, 400; of onychophores, 483, 485; of 

 pelecypods, 374, 519; of squid, 390 



Nephridiostome, of Trypanosyllis, 520 



Nephron, 58, 83, 129 



Nereis, 398-401, 402, 405, 406, 409, 410, 412; 

 .V. dumeriln, 400; N. virens, 397, 398, 399 



Nerve cell, see Neuron 



Nerve endings, 69, 1 1 1 



Nerve fibers, 68, 89, 96 



Nerve impulse, 95, 96; all-or-none, 99, 100, 

 111; graded, 99 



Nerve net, of coelenterates, 525 



Nerve tracts, 103 



Nerves, 69, 89, 96; autonomic, 90, 101, 115 

 117; cranial, 89; mixed, 101; parasympa- 

 thetic, 90, 115; spinal, 90; svmpathetic, 90, 

 115, 121 



Nervous coordination, 87, 522 525; basic 

 mechanisms of, 95-101 



Nervous system, 69, 87-90, 153; central, 69, 

 87-89, 101; localization of function in, 101- 

 105; peripheral, 69, 89-90, 101; of annelids, 

 523, 524; of arthropods, 525; of ascidians, 

 547; of brachiopods, 364; of Branchiostoma, 

 552; of Bugula, 358; of crayfish, 431, 433, 

 434; of earthworm, 409, 410; of inverte- 

 brates, comparative, 523; of locust, 448, 

 451; of mollusks, 525; of nematodes, 349, 

 351; oi Nereis, 400; of pelecypods, 374; of 

 planarians, 318-320, 319; of Saccoalossus, 

 542; of squid, 390; of starfish, 494; of tape- 

 worm, 336 



Nervous tissue, 68-69 



Neural crest, 154 



Neural folds, 154 



Neural plate, 153, 167 



Neural tube, 154 



Neuro-effector junction. 1 13 



Neurohumor, 113, 115, 121 



Neurohypophysis, 118 



Neuromotor system, 251 



Neuromuscular junction, 98, 113 



Neuron, 68, 89, 96; afferent, 98; bipolar, 69; 

 efferent, 98, 115; multipolar, 69 



Neurons, of annelids, 524; of Hydra, 295; of 

 planarians, 320; of sponges, 280, 522, 523 



Neurosecretory cells, 525; of crustaceans, 435, 

 456; of insects, 456, activation of, 457; of 

 mammalian brain, 527 



Neurosecretory mechanisms, of an insect, 526 



Neurosensory cells, 109; of Hydra, 295, 297 



Neurula, 153 



New Zealand, 425, 567, 579 



Niacin, see Nicotinic acid 



Niche, in natural community, 608 



Nicotinic acid, 33 



Night blindness, 31 



Nile River, 558 



Nine-banded armadillo, 209 



Nitrogen, 79 



Nitrogenous wastes, 38, 79 



Nocliluca, 243 



Non-adaptive characteristics in evolution, 653 



Non-disjunction, 206 



Non-striated muscle, 52, 67, 90, 101, 115 



Noradrenaline, 113 



Norepinephrine, 113, 115, 121 



697 



