INDEX 



473 



Nasa obsoleta, 375 



Natural immunity, 83, 84 



Natural Science, 2 



Natural selection, 390 



Near-sightedness, 227 



Necturus, i6g 



Nemathelminthes, 10^, 106, 125, 262, 



263, 296, 309 

 Nematocyst, 101, 133, 258, 259 

 Nemertinea, 105, 106, 125 

 Neoplasms, 294 

 Nephridia, 184 

 Nereis, 140, 166, 195, 374 

 Nerve fibers, 210, 212, 234-236 

 Nerve impulse, 233, 234, 235 

 Nerve net, 67, 210 

 Nerve tracts, 212 

 Neural crest, 217, 220, 221 

 Neural tube, 147, 217, 218, 220, 271, 



273 

 Neuroid transmission, 238, 2sg, 240 



Neurology, 52 



Neuromotor system, 68, 209 



Neuromotorium, 67, 68 



Neuron, 210, 211 



Neuropore, 220, 412 



Nitrogen, 7, 41-45 



Nitrogen cycle, 43, 44, 45 



Nitrogen-fixing bacteria, 44 



Noctiluca, 99 



Non-pathogenic, 74 



Notochord, 114, 7/5, 116, 146, 747 



Nuclear membrane, 29, 30 



Nucleo-proteins, 307 



Nucleus, 29, 30, 38, 3g, 63, 305, et seq. 



Nutrition, 42-44, 52, 57, 66, 153 



Nutritive mechanism, 153 



Obelia, 102, 260, 261 



Obligatory anaerobes, 81 



Octopod, 112 



Oculo-motor nerve, 223 



CEsophagus, 134, 153, 159, 160, 274, 



410 

 Old age, 298-302 

 Olfactory epithelium, 224 

 Olfactory lobes, 2ig 

 Olfactory nerve, 223, 224 



Olfactory sense, 223 



Ontogeny, 130 



Onychophora, 112, 113, 125 



Oocyte, 315, 316, 317 



Oogenesis, 315, 316 



Oogonia, 315, 316 



Ootid, 316, 317 



Operculum, 7/7, 769 



Ophiuroidea, 109 



Opossum, 120 



Optic lobes, 218, 279 



Optic nerve, 223, 226 



Oral cavity, 159, 760 



Oral groove, 6^, 66, 71 



Order, 96 



Organ systems, 50 



Organelle, 47 



Organic Chemistry, 10 



Organic compounds, 45 



Organic evolution, 388-419 



Organization, 300-302 



Organs, 47 



Origin of life, 418 



Orthogenesis, 395 



Os uteri, 201 



Osculum, 99, 700 



Osmosis, j5, 59, 244 



Osmotic pressure, 34, 33, 36, 37, 56, 245 



Otoliths, 233 



Ovary, 92, 195, 796, 79^, 200, 201, 259 



Oviducts, 197, ig8 



Oviparous animals, 195, 276 



Ovum, 90, 794, 197, 200, 201, 246, 251, 



2S3, 234, 236, 305, 315, 316, 318. 



See also Gametes. 

 Oxidation, 42, 38, 60, 79, 176, 190, 



235, 418 

 Oxygen, 7-9 18, 34, 41, 42, 45, 60, 79, 



81, 87, 166, 172-177. 235, 373 

 Oxygen concentration gradients, 379 

 Oxyhaemoglobin, 175, 176 

 Oyster, iii, 240 



Paddle fish, 414 

 Paleobotany, 397 

 Paleontology, 396 

 Paleozoology, 396 



