834 



INDEX 



Shrew, visual cells, 482 

 Shrike. See Lanius. 

 Shrimps, 206 



eyes of, 163, 206 



luminescence in, 740, 743, 746 



See also Crago, etc. 

 Sialia, fundus, 410, PL XII 

 Sign-stimuli, in insects, 588 



in vertebrates, 664 

 Siluridae, blinded, dermal sensitivity in, 

 114 



degenerate eyes in, 725 



uveal tract, 299 



visual cells, rhythmic migration of, 19 



See also Anieiurus. 

 Simenchelys parasitica, 734 



eyes of, 735 

 Simians, 443 



See Anthropoidea. 

 Simiidse, 443 



See also Apes, anthropoid. 

 Simocephalus, conditioning of, 578 

 Simple eyes, 129 

 composite, 152 

 ommatidial, 159 

 Sinapsis alba (white inustard), helio- 



tropism in, 38 

 Sinus gland, in crustaceans, 552, 553 



photoperiodic changes and, 19 

 Siphonops, eyes of, 730 

 Siren, eyes of, 349 

 Sirenians, 446 



lacrimal gland lacking, 493 



lens, 474 



ocular adnexa, 502 



pupils, 472 



refraction of, 639 



retinal vascularization, 480 



retractor bulbi, 495, 496 



visual acuity of, 654 

 Size, perception of, 667, 701 

 Skunk [Mephitis), 445 



nictitating membrane absent, 493 



optic axis, 688 

 Sleep -movements in plants, 9, 10 

 Sleep-rhythms in mammals, 13 

 Sloth, 445 



2-toed, 445, 607 

 pupils, 612 



3-toed, 445 

 Slow eyes, in insects, 584, 706 

 Slow-worm. See Anguis. 

 Slugs, 196, 197 



Slugs, eyes of, 197 



vision of, 574 



See also Gastropods, Li?nax. 

 Smell. See Olfactory sense. 

 Snails, 196, 198 



conditioning of, 575 



eyes of, 197 



reproductive cycle in, 17 



vision of, 574 



See also Gastropods, Helix. 

 Snakes. See Ophidians. 



river-. ^See Homalopsinae. 



sea-. See Hydrophinse. 



tree-. See Dryophis, etc. 

 Snipe, visual field, binocular, 685 

 Soemmerring, D. W., 258, 259 

 Soleidfo, 328 



cornea, 296 



ocular movements of, 693 



scleral cartilage, 294 

 Solenogastres, 196 



sense organs of, 197 

 Solenopsis, compound eyes of, 172, 225 

 Solifugaj, 216 



Sondermann, canals of, 473 

 Souslik, 445 



colovir vision in, 634 



retina, 485 

 Space, perception of, in insects, 589 



in vertebrates, 666 

 Spadella, 194 



ocellus of, 135, 152, 194 

 Spalax, degenerate eyes of, 733 

 Spatial judgments, 700 

 " Spectacle," primary, 265, 266 

 in cyclostomes, 265 



secondary, 255, 266 

 in lizards, 366 

 snakes, 385, 392 

 teleosts, 312 

 Spectral sensitivity of honey-bee, 585 

 Sphcerodactylus, fusion frequency in, 252 



argus, visual cells, 365' 



parkeri, visual cells, 252, 365 

 Sphceroma lanceolata, 206 

 Sphenisciformes. See Impennes. 

 Spheniscus, visual field of, 685 

 Sphenodon punctatus, 379 



accommodation in, 651 



ciliary region, 380 



colour vision of, 628 



eyes of, 380 j^f. 



fovea, 382, 659 



