INDEX 



605 



Nematodes, free-living, 177, 178, 467 



Nemerfinea, 1S3, 544, 547 



Nemertines, 183-184, 437, 441, 442, 407 



Neornithes, 376 



Neoteny, 374 



Neotropical reeion, 604, 506 



Nephridia, 190, 231, 232, 2CS, 313, 315, 442, 466 



Nephridiopore, 231, 232, 245 



Nephros, 442 



Nephrostome, 231, 232, 326 



Nereis, 243 



Nereis vircns, 242 



Nerve, 104. 158, 159 



cells, 29, 100, 101, 136, 137, 444 



center, 166 



cord, 122, 158, 193, 197, 304. 312-315, 377 



endings. 318 



fibers, 100, 101, 136 



net, 138, 430, 444, 408, 470 



ring, 178, 179, 197 

 Nerves, 313 



Nervous activities, 238, 467 

 Nervous impulse, 101, 238 

 Nervous stimulus, 238 



Nervous system, 56, 103, 104, 158-160, 167, 175- 

 176. 184, 186, 189, 197, 213, 218-220, 222, 

 225. 233-234, 254, 276-278, 298, 304, 307,311. 

 312, 327-328, 341, 352, 368-369, 380, 395, 

 408-409, 443-445, 467-468, 472, 544, 545 

 Nervous tissues, 101, 121 

 Nervures, 274 

 Nests, birds, 403, 475 

 Neural arch, 317 

 Neural groove, 355, 356. 418 

 Neural tube, 317, 356, 372 

 Neurilemma, 100 

 Neurocoel, 307 



(Sec also Neural tube) 

 Neuroglia, 435 

 Neuromotor center, 85 

 Neuromuscular cells, 131, 443 

 Neuromuscular mechanism, 136 

 Neurons, 238, 444 

 Neuroptera, 290 

 Newts, 364-366 



Nictitating membrane, 369, 396, 409, 519 

 Nidicolae, 404 

 Nidifugae, 404 

 Night blindness, 537 

 Nighthawk. beak, 399 

 Nitrogen, IS 



cycle, 458, 459 

 Noctiluca, 81 

 Noetiluca scintillans, 80 

 Nomenclature, 58-59, 543, 546 

 Nonmetals, 8 

 Nostrils, 364, 379, 383 

 Notochord (chorda). 122, 300, 310, 312-314, 316, 



317, 336, 372, 377, 4.38, 545 

 Nuclear membrane, 29, 30 

 Nuclear sap, 30 

 Nucleolus, 29, 30 

 Nucleoplasm, 28 



Nucleus, 29, 30, 31, 46, 47, 64, 79, 84, 86, 100, 

 112, 113, 116-119, 127 



Nudibranchs, 221 



Nurse cells, 111, 162,237 



Nymphs, 279 



Garfish, 358 

 Ohelia, 150 

 Obstetrical frog, 366 

 Oceanic distribution, 503 

 Ocelli, 272, 273, 277 

 Octopus, 217, 222, 223, 225 

 Oculina, 152 

 Odonata, 289 

 Oecium, 188, 189 

 Oil, 421 



gland, 98, 318, 400, 439 



{See also Sebaceous gland) 

 Old age, 433 

 Olfactory bulb, 340, 410 

 Olfactory cells, 149 

 Olfactory lobes, 328, 337, 340, 341, 351, 368-370, 



381, 395, 409 

 Olfactory membrane, 329, 410 

 Olfactory organ, 222, 272, 277, 329, 353 

 Olfactory sac, 336, 341, 353 

 Olfactory tentacles, 218, 219 

 Olfactory tract, 340 

 Oligochaeta, 243 

 Oligochaets, 229-240, 243-244 

 Omasum. 416 

 Ommatidium, 254, 255 

 Oniscus asellus, 262 

 Ontogeny, 116, 267 

 Onychophora, 268-209, 304, 305 

 Oocyst, 88 



Oocytes, 107, 109, 110, 530, 538 

 Oogenesis, 107, 109, 110 

 Oogonium, 107, 109 

 Ookinete, 88 

 Opalina, 83 

 Opalina ranarum, 84 



Operculum, 220, 244, 344, 346, 351, 362, 373 

 Ophioderma, 202 

 Ophiopluteus, 206 

 Ophiuroidea, 201-202 



(See also Brittle stars) 

 Opossums, 505, 509 

 Optic lobes, 328, 337, 340, 341, 351, 36S. 370, 381, 



395, 409 

 Optic nerves, 223, 254, 255, 333 

 Optic tract, 395 

 Optimum, 55, 79 

 Oral funnel, 310, 311 

 Oral groove, 69, 70 

 Oral hood, 314, 315 

 Oral ring, 314 

 Oral sucker, 166, 373 

 Oral tentacles, 205 

 Oral valves, 352 

 Orang-utan, 422, 506 

 Order, 58 



Ordovician period, 511-514 

 Organelles, 85, 435 

 Organic matter, 16 



