viii CONTENTS OF VOLUME II. 



CHAPTER VIII. AVES. Pp. 145 201. 



Segmentation and formation of the layers, pp. 145 166. General history of 

 the germinal layers, pp. 166 169. General development of the embryo, pp. 169 

 180. Fatal membranes, pp. 185 199. Amnion, pp. 185 191. Allantois, 

 pp. 191193. Yolk-sack, pp. 193199. 



CHAPTER IX. REPTILIA. Pp. 202 213. 



Lacertilia, pp. 202 --209. Segmentation and formation of the layers, pp. 202 

 207. General development of the embryo, p. 208. Embryonic membranes 

 and yolk-sack, pp. 208 210. Ophidia, p. 210. Chelonia, pp. 210 212. 



CHAPTER X. MAMMALIA. Pp. 214 274. 



Segmentation and formation of the layers, pp. 214 227. General growth of 

 the embryo, pp. 227 232. Embryonic membranes and yolk-sack, pp. 232 239. 

 Comparative history of the Mammalian foetal membranes, pp. 239 257. Com- 

 parative histology of the placenta, pp. 257 259. Evolution of the placenta, 

 pp. 259 261. Development of the Guinea-pig, pp. 262 265. The human 

 embryo, pp. 265 270. 



CHAPTER XL COMPARISON OF THE FORMATION OF THE GERMINAL 

 LAYERS AND OF THE EARLY STAGES IN THE DE- 

 VELOPMENT OF VERTEBRATES. Pp. 275 310. 



Formation of the gastrula, pp. 275 292. The formation of the mesoblast 

 and of the notochord, pp. 292 300. The epiblast, pp. 300 304. Formation of 

 the central nervous system, pp. 301 304. Formation of the organs of special 

 sense, p. 304. Summary of organs derived from the three germinal layers, pp. 

 304 306. Growth in length of the Vertebrate embryo, pp. 306 309. The 

 evolution of the allantois and amnion, pp. 309, 310. 



CHAPTER XII. OBSERVATIONS ON THE ANCESTRAL FORM OF THE 



CHORDATA. Pp. 311 330. 



General considerations, pp. 311 316. The medullary canal, pp. 316, 317. 

 The origin and nature of the mouth, pp. 317 321. The cranial flexure, pp. 321, 

 322. The postanal gut and neurenteric canal, pp. 322 325. The body-cavity 

 and mesoblastic somites, p. 325. The notochord, pp. 325, 326. Gill clefts, 

 PP- 3 2( 5, 327. Phylogeny of the Chordata, pp. 327 329. 



CHAPTER XIII. GENERAL CONCLUSIONS. Pp. 331 388. 



I. Mode of origin and homologies of the germinal layers, pp. 331 



360. Formation of the primary germinal layers, pp. 332, 333. Imagination, 

 PP- 333 335- Delamination, pp. 335 338. Phylogenetic significance of delami- 

 nation and invagination, pp. 338 345. Homologies of the germinal layers, 

 PP- 345' 346- The origin of the mesoblast, pp. 346 360. 



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

 considerations, pp. 360 362. Types of larvre, pp. 363 --384. Phylogenetic 

 conclusions, pp. 384, 385. General conclusions and summary, pp. 385, 386. 



