GENERAL INDEX 533 



Plastron, muscles attached to the, 270 



,, of Thelyphonus, 143 

 Platyhelmia, 475 

 Pleuron, 410, 415 

 Plexus, of Auerbach, 447 



choroid, 38, 45, 49, 103 



„ hypogastric, 3 

 Polychseta, 357, 395 

 Pores, abdominal, 430 

 Porifera, 473 



Pouch, formation of gill, 165, 166 

 Prestwichia, 24, 25, 249, 351 

 Principle of concentration and cephalization, 51 



,, embryology, 455 



Pristiurus, 424 

 Progress, law of, 19 



„ result of, 56 

 Pronephros, 389, 397, 419, 424, 449 

 Prosencephalon, 48 

 Prosoma, 52 

 Protopterus, 148 

 Protostraca, 27, 396, 417 



,, 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 brauchialis 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 



„ ,, in Crustacean eye, 100 



,, of lateral eye of Ammoccetes, 93, 95, 111 

 Musca, 89 



,, Pecten and Spondylus, 114 



,, upright compound, 72 

 ,, simple, 69 

 Rhabdites, 69, 81 



Saccus vasculosus, 244, 322 

 Scales, 345 



