INDEX 



831 



Mussels, 633, 635 



locomotion, 636 

 Mutation, 407, 408, 409-411 



effects, 412 



evolution, 408, 787, 792 



rate, 410 

 Mutualism, 93-96 

 Myelencephalon. 707 

 Myelin sheath, 282, 283, 298 

 Myoglobin, 119, 121 

 Myomeres, 166 

 Myopia, 322, 330 

 Myriapoda, 663 

 Myrmeleon, 598 

 Mysis, 575, 578 

 Mytiliis californicus, 434 

 Myxedema, 262, 263 



N 



Naiads, 565 



Nails, 126, 129, 131, 132, 769 



Nais, 227 



Nasal cavities, 235, 237 



Nasal septum, 270 



Natural selection. 791 



Nauplius, 575, 578 



young stage, 78 

 Nautilus, 322, 630, 631, 633, 646-648 

 Nautilus pompilius. 647 

 Neanderthal man, 772 

 Nearsighted eye, 322. 330 

 Neathes brandti, 554 

 Necator americanus, 524, 525 

 Nectary, 54 

 Necturus, 683. 684 

 Nekton. 74, 77 

 Nemathelminthes. 519 

 Nematocysts. 466, 474, 475 

 Nematode galls, 523 

 Nematodes, 519, 520, 797 



ecology of, 532 

 Nematomorpha, 530. 797 

 Nemertinea, 534-538, 797 

 Neoteny, 340 

 Nephridia, 548, 549, 574 

 Nephritis, 243, 251 

 Nereis limbata, 567 



virens, 565-567, 798 

 Nerocystis, 56 

 Nerve cells, 164, 282, 283, 285, 288, 293 



course of, in spinal nerves, 289 



fatigue of, 286 



motor, 285, 287, 295, 301 



sensory, 285, 287, 295. 301 

 Nervous system. 155, 156. 279-308 



annelid, 554, 562 



Ascaris, 522 



bird, 744-748 



central, 291, 298 



crayfish, 583, 584 



Nervous system — (Continued) 



development of, 300, 370 



earthworm, 284 



frog, 704 



grasshopper, 284 



human, 291 



hydra, 284 



insect. 610, 617 



mollusk, 639 



peripheral. 291 



planarian, 284, 503 



starfish, 657 

 Nervous tissue. 107, 121, 123 

 Nest building, weaver bird, 738 

 Neural arch, 142 

 Neural crests, 370 

 Neural folds, 370 

 Neural groove, 372 

 Neural plate, 363. 367, 370 

 Neural tube, 370, 372 

 Neurenteric canal, 372 

 Neurilemma, 282, 283 

 Neuron, 122, 280, 281, 285, 292, 293, 299, 



300, 372 

 Neuroptera, 593 

 Neutrons, 14, 16 

 Neutrophils, 202, 205-208, 209 

 Newts, 683-685. 688 



metamorphosis of, 686 

 Niacin, 171 



Nictitating membrane, 786 

 Nissl or tigroid bodies. 122, 281 

 Nitrogen, 168, 199, 224-226 

 Nitrogen cycle. 78. 82 

 Noctiluca, 428, 433, 435 

 Noses, 70 



Nosopsyllus fasciatus, 97 

 Nostrils, 234 

 Notochord, 140, 141. 362, 363. 366, 367, 



370. 372, 373, 662-665, 784 

 Nuchal ligament of horse. 114 

 Nucleolus, 33, 34, 39, 42, 53 

 Nucleus, 33, 34. 37, 53 



importance of. 34 



reproduction. 39 

 Nudibranchs, 643 

 Nutrition. 168-194 

 Nymphs, 596, 597 



O 



Obelia. 478. 480. 481 



life cycle. 479 



reproduction. 481 

 Ocelli, 601, 602 



Octopus, 631, 633, 642, 645, 647 

 Octopus vulgaiis, 647 

 Odocoileus virginianus, 766 

 Odonata, 593 

 Olfactory lobe, 705 

 Olfactory organs, 314, 315 



