CHAPTER I. CEPHALOCHORDA. Pp. 1-8. Segmentation and formation of the layers, pp. 1-3. Central nervous system, pp. 3, 4. Mesoblast, p. 5. General history of larva, pp. 6-8. CHAPTER II. UROCHORDA. Pp. 9-39. _Solitaria_, pp. 9-23. Development of embryo, pp. 9-15. Growth and structure of free larva, pp. 15-19. Retrogressive metamorphosis, pp. 19-23. _Sedentaria_, p. 23. _Natantia_, pp. 23-28. _Doliolidæ_, pp. 28, 29. _Salpidæ_, pp. 29-34. _Appendicularia_, p. 34. Metagenesis, pp. 34-38. CHAPTER III. ELASMOBRANCHII. Pp. 40-67. Segmentation and formation of the layers, pp. 40-47. Epiblast, p. 47. Mesoblast, pp. 47-51. Hypoblast and notochord, pp. 51-54. General features of the embryo at successive stages, pp. 55-62. The yolk-sack, pp. 62-66. CHAPTER IV. TELEOSTEI. Pp. 68-82. Segmentation and formation of the layers, pp. 68-73. General history of the layers, pp. 73-75. General development of the embryo, pp. 76-81. CHAPTER V. CYCLOSTOMATA. Pp. 83-101. Segmentation and formation of the layers, pp. 83-86. Mesoblast and notochord, pp. 86, 87. General history of the development, pp. 87-97. Metamorphosis, pp. 97-100. Myxine, p. 100. CHAPTER VI. GANOIDEI. Pp. 102-119. _Acipenser_, pp. 102-110. Segmentation and formation of the layers, pp. 102-104. General development of the embryo and larva, pp. 104-110. _Lepidosteus_, pp. 111-119. Segmentation, pp. 111, 112. General development of embryo and larva, pp. 112-119. General observations on the embryology of Ganoids, p. 119. CHAPTER VII. AMPHIBIA. Pp. 120-144. Oviposition and impregnation, pp. 120, 121. Formation of the layers, pp. 121-124. Epiblast, pp. 125-127. Mesoblast and notochord, pp. 128, 129. Hypoblast, pp. 129-131. _General growth of the embryo_, pp. 131-143. Anura, pp. 131-141. Urodela, pp. 141-143. Gymnophiona, p. 143. 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. _Foetal membranes_, pp. 185-199. Amnion, pp. 185-191. Allantois, pp. 191-193. Yolk-sack, pp. 193-199. 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. Comparative 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 XI. COMPARISON OF THE FORMATION OF THE GERMINAL LAYERS AND OF THE EARLY STAGES IN THE DEVELOPMENT OF VERTEBRATES. Pp. 275-310.