820 



INDEX 



Opossum, 437 



Australian, lateral geniculate body, 489, 

 490 

 pupils, 612 

 eye of, 605 

 mouse, ciliary muscles, 439 



visvial cells, 441 

 Virginian, 439 



ciliary muscles, 439 

 colour blindness of, 633 

 fundus, PI. XIII 

 nictitating membrane, 441 

 optic axis, 688 

 retinal circulation, 440 

 tapetum, 440, 608 

 visual acuity of, 665 

 Optic axis, 675, 688 



chiasma. See Chiasmal decussation, 

 disc, characteristics in 

 birds, 410 

 chelonians, 372 

 crocodilians, 378 

 lacertilians, 362 

 marsupials, 440 

 monotremes, 436 

 placentals, 486 

 polypterini, 320 

 selachians, 288 

 snakes, 390 

 Sphenodon, 381 

 teleosts, 310 

 urodeles, 347 

 ganglia, in arthropods, 523, 524, 525 

 lobes, of arthropods, 521, 525, 526, 584 

 of birds, 535 



cephalopods, 528, 529, 576 

 fishes, 534 

 mammals, 535 

 reptiles, 535 

 norve, characteristics in 

 anurans, 344 

 birds, 422 

 crocodilians. 378 

 dipnoans, 313 

 holosteans, 322 

 lacertilians, 366 

 lamprey, 270 

 monotremes, 436 

 placentals, 486, 488 

 selachians, 288 

 snakes, 392 

 Sphenodon. 383 

 teleosts, 310 



Optic nerve, characteristics in 

 urodeles, 350 

 decvissation of fibres. See Chiasmal 



decussation, 

 septal system of, 487 

 pedicle, in selachians, 290 

 pits, 239 

 thalamus, 538 

 vesicles, 239, 537, 711 

 Optical system, of vertebrates, 605, 638 



duplicated, 641 

 Optics of compound eye, 170 

 Optomotor reaction, 568 

 in crustaceans, 578 

 insects, 73, 583, 584 

 colour vision and, 587 

 light -differences and, 585 

 visual acuity and, 588, 589 

 spiders, 580 



vertebrates, colour vision and, 623 

 movement, perception of, and, 

 706 

 Orang-utan, 443 



See also Apes, Primates. 

 Orbicularis oculi, in placentals, 492 

 Orbit, characteristics in 

 anurans, 346 

 birds, 423, 424, 425 

 chelonians, 375 

 crocodilians, 378 

 hammerhead shark, 327 

 lacertilians, 368 

 lamprey, 270 

 monotremes, 437 

 placentals, 497 

 selachians, 290 

 snakes, 393 

 Sphenodon, 383 

 teleosteans, 312 

 Orbital axis, 675, 676 



ganglion. See Ciliary ganglion, 

 nerves, in placentals, 5i31 

 sinus, in rabbit, 500 

 Orca. See Whale, killer 

 Orectolobus, pupil, 286 

 Organelle, 129 



Orientation angle, in menotaxis, 61 

 to light, 27 



methods of, 31 



See Phototaxis, etc. 

 of insects, 67 

 of plants, 27 

 polarized, 66 



