X TABLE OF CONTENTS. 



of the auditory involution, 157. The otic vesicle, 157. The mem- 

 branous labyrinth, 158, 159. The osseous labyrinth, 159, 160. Com- 

 parison of ear with eye, 160, 161. The organ of smell, 161, 162. 

 The olfactory lobes and nerves, 162. The visceral arches and visceral 

 clefts, 162 167. Superior maxillary, and frouto-nasal processes, 

 164, 165. Fate of first visceral cleft, 165, 166. The meatus audi- 

 torius externus, 166. The tympanic membrane, 166. The Eustachian 

 tube and tympanic cavity, 165, 166. The fenestra ovalis and rotimda, 

 166. The columella, 166, 167. The vascular system, 167 170. The 

 aortic arches, 167, Changes in the heart, 167, 168. The venous 

 system, 169, 170. The meatus venosus, cardinal veins and ductus 

 Cuvieri, 169, 170. The alimentary canal, 171 185. Folding in of 

 the splanchnopleure, tail-fold, 171, 172. The mesentery, 172, 173. 

 (Esophagus and stomach, 173. The intestine, 174. The postanal 

 gut, neurenteric canal and proctodaeum, 174 176. The lungs, 

 176 178. The liver, 178 181. The pancreas, 181. The thyroid 

 body, 181, 182. The spleen, 182. The growth and blood-vessels of the 

 allantois, 182 184. The mesollast, 185 193. The muscle-plates, 

 186 189. The intermediate cell-mass and Wolffian body, 189 193. 

 A typical Wolffian tubule, 193. Change of position of Wolffian duct, 

 193. Summary, 193, 194. 



CHAPTER VII. 



The Changes which take place on the Foubth Day, pp. 195231. 



Appearance on opening the egg, 195. Growth of amnion, 195, 196. 

 The vitelline duct, 196. Increase of cranial flexure and tail-fold, 196 

 198. The first appearance of the limbs, 198. The growth of the 

 brain, 200. The face, 202. Changes in the nasal pits, 202. The sto- 

 modseum and mouth, 202, 203. The cranial nerves, 203. Clianges in 

 the mesohlastic somites, 204 212. The membranous vertebral 

 column, 205. The secondary segmentation of the vertebral column 

 and foiTuatiou of the permanent vertebras, 205 207. Recapitulation, 

 207, 208. The changes in the notochord, 208211. Ossification of 

 vertebrffi, 209, 210. The changes in the muscle plates, 211, 212. 

 Wolffian body and duct, 212214. The Miillerian duct, 214 218. 

 The kidney and ureter, 218 220. The ovaries and testes, 220 223. 

 Fate of the embryonic urinogenital organs, 223, 224. Chaflges in the 

 arterial system, 224 226. Changes in the venous system ; veins of 

 the liver, 226 229. Changes in the heart ; the ventricular septum, 

 229, 230. Summary, 230, 231. 



