viii CONTENTS OF VOLUME IT. 



CHAPTER VIII. AYES. Pp. 120166. 



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. Foetal membranes, pp. 154 165. Amnion, pp. 154158. Allautois, 

 pp. 159, 160. Yolk-sack, pp. 161165. 



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. 172173. Opliidla, 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. 221226. 



CHAPTER XI. COMPARISON OF THE FORMATION OF THE GERMINAL LAYERS 



AND OF THE EARLY STAGES IN THE DEVELOPMENT OF 



VERTEBRATES. Pp. 229257. 



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

 of the notochord, pp. 243249. The epiblast, pp. 249252. 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. 

 Pj>. 258273. 



General considerations, pp. 258262. The medullary canal, pp. 262, 263. 

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

 267. The postanal gut and ueurenteric 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. 271273. 



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. Imagination, 

 pp. 276, 277. Delamination, pp. 277279. Phylogenetic significance of delami- 

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

 pp. 285, 286. The origin of the mesoblast, pp. 286297. 



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



considerations, pp. 297299. Types of larva?, pp. 299 316. Phylogeuetic con- 

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



