522 INDEX 



Parietal 

 organs, 



connection with epiphysis, 276 

 continuity with epiphysis, 275 

 disappearance of in adult animal, 282 

 of embryo viper, 284 

 of Iguatiid.?, 275 

 nerves of, 230, 258, 263, 403 

 of Petromyzon, 187 

 pigmentation of, 68 

 sensitivity to light and heat, 6 

 separation from epiphysis, 228, 274 

 of Sphenodon, 253, 369 

 pit, 181, 182, 220 

 plate, 181, 182, 470, 471 

 plug, 69, 181, 188, 259, 260, 266, 369 

 region of brain, 180, 183 

 scale of Lacerta muralis, 72, 273, 274, 282 

 spot, 71, 74, 181, 229, 273, 274 

 hour-glass shaped, 274 

 Pars 



intercalaris, 180, 186 

 iridica retina;, 61 

 Patella, 48, 147 

 Paterina, 92 



Pecten, 148, 149, 356, 357, 379 

 Peduncles of pineal organ 

 inferior, 417 

 lateral, 417 

 superior, 417 

 Pelias berus, 284 

 " Pellucida," 189 



of parietal sense-organ, 69 

 Pelycepoda, 147 

 Pentastomida, 131 

 Perineural epidermic cells, 131, 132 

 Perineurium, persistence of, 279 

 Peripatus, 



cerebral grooves of, 114 

 eyes of, 112, 113, 114 

 Perch, pineal organs of, 217 

 Permian strata, Stegocephala of, 237 

 Petromyzon 

 fluviatalis, pineal organs of, 28, 184, 187, 

 468 

 unequal size of habenular ganglia, 185, 



187 

 white pigment of pineal eye, 64 

 planeri, pigmentation of pineal eye, 68 

 Petromyzontia, 344 

 Phacops latifrons, 137, 366 

 Phsospheres, 118, 126 



post-nuclear, 131 

 Phallusia, larva of, 5, 175 

 Pharyngolepis, 331 

 Phascolosoma, paired ocelli of trochophore 



larva, 91 

 Pholidosteus, 208, 245, 329, 468 

 Phoronida, 91 

 Phosphate of lime, deposit of in retinal 



cells, 71 

 Phosphorescence of eye-spots, 82 

 Photospherion, 24 

 Phragmacone, 354 

 Phragmoceras, 151 

 Phrynocephalus, 273 



Phrynosoma, 275 



Phyllopoda, 363 



Pia arachnoid, thickening of, 456 



Pia mater, 307, 310 



Pigment, 



absence of in skin of cave-dwelling 

 animals, 227 



absence of over parietal organ, 188, 282 



around terminal vesicle, 207 



in accessory parietal organs, 245 



balls, 75, 254 



black, 62, 81 



brown, 75 



of degenerating tissues, 63 



in end-vesicle of cave-dwelling animals, 

 227 



in epidermis over parietal organ, 283 



epithelial, 75 



in eye of Phallusia, 175 



in eyes of Arachnids, Crustacea, Insects, 

 67 



functions of, 61 



of interstitial tissue, 62, 389 



layer, 346 



in lens of parietal organ, 62, 247, 255, 

 271 



in median eyes of Euscorpius, 133 



in median eyes of Limulus, 125 



of membranes of brain, 62 



mesodermal, 75 



migration of, 60, 72 



in parietal scale, 274 



of parenchymal cells, 62, 389 



red, 66, 81 



in retina of parietal organ, 70, 254, 255 



of sensory organs, 7 



spot(s) of Amphioxus, 179 

 of Planaria, 25 



subepithelial, 60 



uveal, 60 



waste (usufruct), 62 



white, 63, 65, 70, 190 



yellow, 62 

 Pigment cells, 11, 14, 18, 19, 48, 49, 50, 52, 



57 



around parietal organ, 275 



branched, 69 



in eyes of Dytiscus, 118, 119 



hexagonal, 61, 78 



inter-retinular, 119, 120 



of intrusive mesenchyme, 61 



of pineal body, 59 

 Pigment granules, 



coarse, 57 



fine, 57 



formation of, 1 1 



movements of, 57 



of pineal organ, 399 



of retina, 6 



white, 70, 190 

 Pigmentation, 



absence of in region of parietal spot, 72, 



73> 134 



of ciliary region, 78 



of developing retina, 79 



of iris, 78 



