INDEX 



819 



Octopus 



optic lobes, 529 

 reactions of, 528 

 vision of, 575 

 vulgaris, 202 

 Ocular movements, 689 

 involuntary, 690 

 voluntary. 692 



in amphibians, 345, 694 

 birds, 425. 695 

 chelonians, 374 

 fishes, 278, 693 

 lacertilians, 368 

 mammals. 497, 696 



co-ordination of, 693 

 reptiles, 694 

 snakes, 393 

 tension, diencephalon and, 560 

 diurnal rhythm in, 14, 561 

 Oculiferous tubercle, in harvestmen, 

 215 

 j errymanders, 216 

 sea-spiders, 217 

 Oculoir.otor centres, 534 



nuclei, 535, 699 

 Ocydpoda ippens, 205 

 Odonata, 220, 225 

 eyes of, 222, 225 

 See also Aeschna. Anax. 

 Odontoceti, 446 



Odontosyllis, bioluminescence in, 741 

 (Edicnenius, pecten, 412 

 Oil-droplets, colour vision and, 631 



occurrence of, 631, 656 

 Okapi (Okapia), nictitating membrane, 



496 

 Olfactory centres, 543 

 sense, of bees, 588 

 birds, 600 

 fishes, 598 

 gastropods, 574 

 insects, 581 

 mammals, 601, 733 

 reptiles, 599 

 predominance of, 103 

 spatial judgments and, 667 

 Oligochaetes, 190 



bioluminescence in, 739 

 conditioning of, 573 

 nervous system, 519 

 ocelli, 190 

 See also Lumbricus. 



Ommatidial angle, 172, 173 

 eye. See Compound eyes, 

 simple, 159 

 Ommatidium, 155 

 Ommatin, 123 

 Ommin, 123 

 Ommochromes, 123 

 Onchidiuyn, 199 



accommodation in, 590 

 eyes of, 148, 199 

 homing ability of, 575 

 Oniscus, metabolic rhythm in, 15 

 Ontogeny of vertebrate eye, 239, 240 

 Onychophores, 204 

 eyes of, 205 



degenerate, 724 

 nervous system, 521 

 vision of, 578 

 See also Peripatus. 

 Operculum (pupillary). 612 

 in catfishes, 304, 329 

 flat-fishes. 329 

 mammals, 469, 470 

 selachians, 287 

 Ophidians, 353 



accommodation in, 648 

 colour training of, 628 

 eyes of, 373 j^., 385 



degenerate, 731 

 fundi, PL X 

 irides, PI. IX 



ocular movements, 694, 695 

 olfactory sense in, 599 

 pineal organ, 716 

 pupils, contractile, 612 

 refraction of, 629 

 vibi'atory sense in, 599 

 vision of, 599 

 visual acuity of, 661 

 field, binocular, 682 

 Ophiops, eyelids in, 366, 367 

 Ophiotettix, 223 



Ophisauriis ventralis, fundus, 362 

 Ophiuroidea, 184 



Ophrycessa superciliosa, iris, PL V 

 ' Ophthalmic artery, in anurans, 340 

 j in placentals, 498 



[ Opiliones. See Phalangida. 

 j Opisthobranchs, 196 

 ! neuro -secretory cells, 552 



Opisthoproctus, 324 

 j tubular eyes of, 324 

 1 visual field, binocular, 680 



