GENERAL INDEX 
Plastron, muscles attached to the, 270 
a of Thelyphonus, 143 
Platyhelmia, 475 
Pleuron, 410, 415 
Plexus, of Auerbach, 447 
A choroid, 38, 45, 49, 103 
my hypogastric, 3 
Polycheta, 357, 895 
Pores, abdominal, 430 
Porifera, 473 
Pouch, formation of gill, 165, 166 
Prestwichia, 24, 25, 249, 351 
Principle of concentration and cephalization, 51 
+s embryology, 455 
Pristiurus, 424 
Progress, law of, 19 
53 result of, 56 
Pronephros, 389, 397, 419, 424, 449 
Prosencephalon, 48 
Prosoma, 52 
Protopterus, 148 
Protostraca, 27, 396, 417 
a dominance of, 28 
Protozoa, 166, 479 
Pseudoniscus, 25, 249 
Pteraspis, 29, 30, 275, 326, 343, 344, 350 
Pterichthys, 29, 31, 239, 326, 351 
Pterygoid, pedicle of, 295 
Pterygotus, 25, 27, 56, 170, 191, 221, 235, 238, 249, 276 
Ptychodera, 494, 495 
Ramus branchialis profundus of facial nerve, 311 
»  communicans, 2, 3 
Raphe, 46 
Recapitulation, law of, 434, 456, 498 
Regeneration of nerves, 469 
Reptiles, dominance of, 21 * 
Retina, compound, 71 
» development of, 101 
» inversion of, in Vertebrates, 114 
» inverted, 70 
» layers of compound, 73 
33 a in Crustacean eye, 100 
» of lateral eye of Ammoccetes, 93, 95, 1[1 
» Musca, 89 
»  Pecten and Spondylus, 114 
» upright compound, 72 
Wg ” simple, 69 
Rhabdites, 69, 81 
Saccus vasculosus, 244, 322 
Scales, 345 
539 
