INDEX. 



651 



Oncliidium, eye of, 394 



Opercular bones, 487 



Operculum, of Teleostei, 62; Acipeuser, 



• 88 ; Lepidosteus, 96, 98 ; Amphibia, 111 



Ophidia, development of, 173; arterial 

 system of, 633 ; venous system of, 539 



Optic chiasma, 354, 405 



Optic cup, retinal part of, 402; ciliary 

 portion of, 403 



Optic lobes, 352 



Optic nerve, development of, 405 ; compa- 

 rative development of, 411 



Optic tlialami, development of, 355 



OjJtic vesicle, of Elasmobrancbii, 46 — 48 ; 

 Teleostei, 59, 410; Petromyzon, 73, 76; 

 Acipenser, 87; Lepidosteus, 94; Chick, 

 141; Eabbit, 190; general development 

 of, 353; formation of secondary, 401; 

 obliteration of cavity of, 402 ; compara- 

 tive development of, 410 ; of Lepidosteus 

 and Teleostei, 410. See also ^Eye^ 



Ora serrata, 402 



Orbitosphenoid region of skull, 470 



Organs, classification of, 323; derivation 

 of from germinal layers, 324 



Orycteropus, placenta of, 207 



Otic process, of Axolotl, 480; of Frog, 

 481 et seq. 



Otoliths, 422 



Oviposition, of Amphioxus, 1 ; Elasmo- 

 branehii, 33; Teleostei, 55; Petromy- 

 zon, 69; Amphibia, 100; Keptilia, 167 



Ovum, of Amphioxus, 1; Pyrosoma, 19; 

 Elasmobrauchii, 33 ; Teleostei, 55 ; 

 Petromyzon, 68 ; Myxine, 82 ; Acipen- 

 ser, 84; Lepidosteus, 91; Amphibia, 99; 

 Chick, 121; Eeptilia, 167; Mammalia, 

 177; of Porifera, 610; migration of in 

 Ccelenterata, 611; Vertebrata, 614 



Palatine bone, of Teleostei, 478; origin 

 of, 488 



Pancreas, Acipenser, 91 ; general develop- 

 ment of, 633 



Pancreatic cffica, of Teleostei, etc. 632 



Papillaj, oral, of Acipenser, 89; Lepidos- 

 teus, 95 



Parachordals, 466 



Parasphenoid bone, 488 



Parepididymis, 597 



Parietal bones, 487 



Paroophoron, 597 



Parovarium, 597 



Pectoral girdle, 492; of Elasmobranchs, 

 493; of Teleostei, 493; of Amphibia 

 and Amniota, 493 ; comparison of with 

 pelvic, 500 



Pecten, eye of, 394 



Pecten, of Ammocoetes, 410; of Chick, 

 412; Lizard, 413; Elasmobranchs, 413 



Pedicle, of Axolotl, 480; of Frog, 481 



Pclobates, branchial apertures of, 112; 

 vertebral column of, 458 



Pelodytes, branchial chamber of, 112 



Pelvic girdle, 497; of Fishes, 497; Am- 

 phibia and Amniota, 498 ; of Lacerti- 

 lia, 499; of Mammalia, 499; compari- 

 son with pectoral, 500 



Penis, development of, 599 



Peribranchial cavity, of Amphioxus, 6 ; of 

 Ascidia, 15; Pyrosoma, 20 



Pericardial cavity, of Pyrosoma, 21 ; Elaa- 

 mobranchii, 40; Petromyzon, 77; gene- 

 ral account of, 514; of Fishes, 516; of 

 Amphibia, Sauropsida and Mammalia, 

 517 



Perichordal formation of vertebral column, 

 458 



Perilymph of ear, 430 



Periotic capsules, ossifications in, 489, 

 490 



Peripatus, nervous system of, 337; eye of, 

 395 ; excretory organs of, 567 



Peritoneal membrane, 514 



Petromyzon, development of, 63; affini- 

 ties of, 68, 69; general development 

 of, 72; hatching of, 73; comparison of 

 gastrula of, 233 ; branchial skeleton of, 

 2,59, 471 ; cerebellum of, 350 ; pineal 

 gland of, 357; pituitary body of, 359; 

 cerebrum of, 361; auditory organ of, 

 426; olfactory organ of, 439; compari- 

 son of oral skeleton of with Tadpole, 

 482; pericardial cavity of, 515; abdo- 

 minal pores of, 515; venous system of, 

 535; excretory organs of, 577; segmen- 

 tal duct of, 577; pronephros of, 577; 

 mesonephros of, 577 ; thyroid body of, 

 625; postanal gut of, 636; stomodiseum 

 of, 639 



Phosphorescence of larvse, 301 



Phylogeny, of the Chordata, 271; of the 

 Metazoa, 316 



Pig, placenta of, 209 ; mandibular and 

 hyoid arches of, 484 



Pineal gland, of Petromyzon, 76 ; Chick, 

 145 ; general development of, 356 ; nature 

 of, 356, 358 



Pipa, brood-pouch of, 100 ; metamorpho- 

 sis of, 114; yolk-sack of, 115; vertebral 

 column of, 458 



Pituitary body, of Rabbit, 191; general 

 development of, 358 ; meaning of, 359 



Placenta, of Salpa , 24 ; Elasmobrauchii, 54 ; 

 of Mammaha, 193 ; villi of, 195 ; de- 

 ciduate and non-deciduate, 198 ; com- 

 parative account of, 198 — 216 ; charac- 

 ters of primitive type of, 199 ; zonary, 

 205 ; nou-deciduate, 207 ; histology of, 

 215; evolution of, 216 



Placoid scales, 326 



Planorbis, excretory organs of, 562 



Planula, structure of, 303 



Pleural cavities, 518 



Pleuronectidffi, development of, 65 



Pneumatocoela, characters of, 271 



