viii CONTENTS OF VOLUME II. 



Chapter VIII. Aves. Pp. 120—166. 



Segmentation and formation of the layers, pp. 120 — 138. General history of 

 the germinal layers, pp. 138 — 140. General development of the embryo, pp. 140 

 — 150. Fcztal memlranes, pp. 154 — 165. Amnion, pp. 154—158. Allantois, 

 pp. 169, 160. Yolk-sack, pp. 161—165. 



Chapter IX. Reptilia. Pp. 167 — 176. 



Lacertilia, pp. 167 — 173. Segmentation and formation of the layers, pp. 167 

 — 171. General development of the embryo, p. 172. Embryonic membranes and 

 yolk- sack, pp. 172—173. Ophidia, pp. 173, 174. Chelonia, pp. 174, 175. 



Chapter X. Mammalia. Pp. 177 — 228. 



Segmentation and formation of the layers, pp. 177 — 188. General growth of 

 the embryo, pp. 188 — 192. Embryonic membranes and yolk-sack, pp. 193 — 198. 

 Comparative history of the Mammalian foetal membranes, pp. 198 — 215. Com- 

 parative histology of the placenta, pp. 215, 216. Evolution of the placenta, 

 pp. 216 — 218. Development of the Guinea-pig, pp. 218 — 221. The human embryo, 

 pp. 221—226. 



Chapter XI. Comparison of the formation of the germinal layers 



AND of the early STAGES IN THE DEVELOPMENT OF 



Vertebrates. Pp. 229 — 257. 



Formation of the gastrula, pp. 229 — 242. The formation of the mesoblast and 

 of the notochord, pp. 243—249. The epihlast, pp. 249—252. Formation of the 

 central nervous system, pp. 250 — 252. Formation of the organs of special sense, 

 p. 252. Summary of organs derived from the three germinal layers, pp. 252 — 254. 

 Growth in length of the Vertebrate embryo, pp. 254 — 256. The evolution of 

 the allantois and amnion, pp. 256, 257. 



Chapter XII. Observations on the ancestral form of the Chordata. 



Pp. 258—273. 



General considerations, pp. 258—262. The medullaiy canal, pp. 262, 263. 

 The origin and nature of the mouth, pp. 263—266. The cranial flexure, pp. 266, 

 267. The postanal gut and neurenteric canal, pp. 267 — 269. The body-cavity and 

 mesoblastic somites, p. 269. The notochord, pp. 269, 270. Gill clefts, pp. 270, 

 271. Phylogeny of the Chordata, pp. 271—273. 



Chapter XIII. General Conclusions. Pp. 274—319. 



I. Mode of origin and homologies of the germinal layers, pp- 274— 



297. Formation of the primary germinal layers, pp. 275, 276. Invagination, 

 pp. 276, 277. Delamination, pp. 277—279. Phylogenetic significance of delami- 

 nation and invagination, pp. 280—285. Homologies of the germinal layers, 

 pp. 285, 286. The origin of the mesoblast, pp. 286—297. 



II. Larval forms : their nature, origin, and affinities. Preliminary 



considerations, pp. 297—299. Types of larvas, pp. 299—316. Phylogenetic con- 

 clusions, pp. 316, 317. General conclusions and summary, pp. 317, 318. 



