INDEX 



843 



Woodlice, 206 



eyes of, 206 

 lacking, 729 



See also Annadillidiuni, Oniscus. 

 Woodpecker. See Dendrocopus, 



Melanerpes. 

 Worms, 186 



bilateral symmetry in, 186, 517 



bioluminescence in, 739, 745 



eyes of, 187 



nerve -net, 515, 518 



nervous system, 518 



receptor-effector system, 514 



segmented. See Annelids. 



unsegmented, 187 



phototactic reactions of, 572 

 See also Platyhelminthes, etc. 



vision of, 572 

 W-substance in amj^hibians, 97 



X 



Xanthophores, 88 



in corneal epithelium of fishes, 295 

 Xanthophyll, 119 



in human macula, 122 

 Xanthnsia, foveal pit, 365 

 pupils, 359 

 visual cells, 252, 364 

 Xenarthra, 445 



cornea, keratinized, 456 

 retinal vascularization, 480 

 visual cells, 482 

 Xenopus Icevis, 334, 337 



colour changes in, 91, 98 



pineal organ and, 719 

 iris, 337 



migration of pigment absent, 614 

 reproductive cycle in, 17 

 retina, 343 



Xerus. See Squirrel, African. 

 Xiphias, 294 



dilatator muscle, 303 



optic nerve, 311 



scleral ossicles, 294 

 Xiphosura, 212 



neuro -endocrine system, 552 



See also Limulus. 

 X-organ, in crustaceans, 552, 553 



in myriajDods, 552 



Zaglossus. See Echidna. 

 Zamenis, visual field, binocular, 684 

 Zebra (Equus zebra), 444, 446 

 corpora nigra, 469 

 See also Equidse. 

 Zeis's glands, in elejshant, 491 

 Zenaidura macroura, reproductive cycle in. 



18 

 Zenion, eyes of, 323 

 Zonosaurus, eyelids, 367 

 Zonular fibres, characteristics in 

 anurans, 335 

 ■ birds, 410 



lacertilians, 361 

 monotremes, 436 

 placentals, 475 

 selachians, 285 

 snakes, 389 

 Sphenodon, 381 

 See also Suspensory ligament. 

 Zonurus giganteus, visual field, binocular, 



682 

 Zoraptera, 220 



Zosterops japonica, reproductive cycle in, 

 18 



