Index 



879 



Neurones, sensory, 454, 455 



soma of, responses in, 798 



transmission between, 789 

 polarity in, 790 

 Neurosecretory cells, 768 

 Niacin, requirements of, 126 

 Nicotine, action of on heart, 561 

 Nicotinic acid. See Niacin. 

 Nitrogen, content of, in relation to metab- 

 olic rate, 229 



excretion of, 187-208 



distribution of products, 190-200 

 protein, conclusions on, 201 



requirements of, 115-122 



sources of, 113 

 Nitrogenous products, chemical nature of, 



187-190 

 Noctiltica, 10 



bioluminescence in, 661 

 Nocturnal activity, eye adaptation to, 398 

 Nucleic acid metabolism, products of, 189, 



203 

 Nutrition, 112-143 



oxygen consumption and, 236 



specific factors in, 122-136 



summary of, 136 



unknown factors in, 135 

 Nymphs, metamorphosis of, 732 

 Nystagmus, 522 



Ocean, salinity of, 9. See also Sea water. 

 Ocelli in arthropods, 391 



in flagellates, 383 

 Octopine, 617 



Octopus, electrocardiogram in, 554 

 Oculomotor nucleus, facilitation in, 801 

 Odonata, gills in, 215 

 Odor, chemical structure and, 466 

 classification of, 460 

 receptors for. See Olfaction and Chemo- 

 receptors. 

 Olfaction, receptors for, 451, 453, 459 

 activation of, 465 

 in insects, 450 

 sensitivity of, 457 

 thresholds of, 458 

 See also Chemorecevtion. 

 Oligochaeta, osmoregulation in, 36 

 Ommatidia, 763, 764 



in compound eye, 387, 389, 390 

 Onchidium, osmotic adjustment in, 12, 13 

 Opalinidae, water entrance in, 43 

 Ophiuroidea, luminescence in, 664 

 Ophryoscolecidae, water intake in, 44 

 Opossum, body temperature in, 363, 364 

 Optic nerve activity', retinal activitv and, 

 433 

 discharge, measurement of visual 

 functions by, 431 



Optic nerve, electrical activity of, 428-435 

 Orange, transient, 411 

 Organ of Corti, 475 



Orientation, equilibrium, in vertebrates, 520 

 in flying insects, 523 

 photoreceptors and, 381-405 



in arthropods, 393 

 to gravity, 5 1 5 

 Ornithine cycle, 188 



phylogeny of, 201 

 Ornithorhynchtis, motor cortex in, 837 

 Ornithuric acid, excretion of, 189 

 Orthokinesis, 449 



Orthoptera, phonoreception in, 498, 499 

 Osmoregulation, 8, 14-20 

 by exclusion of water, 19 

 by storage of water, 18 

 in Crustacea, 20-33 

 in fish, 46-52 

 in land arthropods, 55 

 in reptiles, birds, and mammals, 58-62 

 simple types, 14 

 summary of conclusions, 62-66 

 Osmotic behavior, nitrogen excretion in 



relation to, 201 

 Osmotic characteristics of various animals, 



63 

 Osmotic concentration, adjustment to me- 

 dium, 10-14 

 with volume regulation, 13 

 without volume regulation, 10 

 of cytoplasm of Protoza, 39 

 regulation to medium, 14-20 

 water content of tissues and, 8 

 Osmotic pressure, definition, 6 

 methods of measuring, 8 

 Osmotic regulation. See Osmoregulation. 

 Ossicles, Weberian, 486 

 Ostariophysina, phonoreception in, 486 

 Osteichthyes, respiratory responses in, 266 

 Ovary, androgen production by, 744 

 effect of gonadotropins on, 741 

 estrogen production by, 745 

 Ovulation, gonadotropins and, 741 

 Oxidation, sources of, 268 

 Oxygen, availability of, efFects of, 209 

 capacity, 306 



altitude and, 316 

 consumption, activity and, 237 

 age and, 228 

 cihary activity and, 651 

 dependence on oxygen tension, 244 

 determination of, 224 

 habitat and, 239 

 in Gammarus, 32 

 in hibernation, 372 

 levels of, 223-244 

 nutrition and, 236 

 relation to oxygen tension, 244-254 



