TABLE OF CONTEXTS. ix 



CHAPTER VII. 



GENERAL DEVELOPMENT OF THE TRUNK FROM STAGE K TO THE 

 CLOSE OF EMBRYONIC LIFE, pp. 140 — 155. 



External epiblast. — Division into separate layers. Placoid scales. Formation 

 of their enamel. Lateral line. — Previous investigations. Distinctness of lateral 

 line and lateral nerve. Lateral nerve a branch of vagus. Lateral line a thick- 

 ening of epiblast. Its greater width behind. Its conversion into a canal by its 

 cells assuming a tubular arrangement. The formation of its segmental apertures. 

 Mucous canals of the head. Their nerve-supply. Eeasons for dissenting from 

 Semper's and Gotte's view of lateral nerve. Muscle -plates. — Their growth. Con- 

 version of both layers into muscles. Division into dorso-lateral and ventro- 

 lateral sections. Derivation of limb-muscles from muscle-plates. Vertebral 

 column and notochord. — Previous investigations. Formation of arches. Forma- 

 tion of cartilaginous sheath of notochord and membrana elastica externa. Dif- 

 ferentiation of neiu'al arches. Differentiation of haemal arches. Segmentation 

 of cartilaginous sheath of notochord. Vertebral and intervertebral regions. 

 Notochord. 



CHAPTER YIII. 



DEVELOPMENT OF THE SPINAL NERVES AND OF THE SYMPATHETIC 

 NERVOUS SYSTEM, pp. 156 173. 



The spinal nerves. — Formation of posterior roots. Later formation of 

 anterior roots. Development of commissure uniting posterior roots. Sub- 

 sequent development of posterior roots. Their change in position. Develop- 

 ment of ganglion. Further changes in anterior roots. Junction of anterior 

 and posterior roots. Summary. General considerations. — Origin of nerves. 

 Hypothesis explaining peripheral growth. Hensen's views. Later investigations. 

 Gotte. Calberla. Relations between Annelidan and Vertebrate nervous systems. 

 Spinal canal. Dr Dohrn's views. Their difficulties. Hypothesis of dorsal 

 coalescence of lateral nerve cords. Sympathetic nervous system. — Development of 

 sympathetic ganglia on branches of spinal nerves. Formation of sympathetic 

 commissure. 



CHAPTER IX. 



DEVELOPMENT OF THE ORGANS IN THE HEAD, pp. 174 216. 



Development of the Brain, pp. 174 — 183. General history. Fcre-brain. 

 — Optic vesicles. Infundibulum. Pineal gland. Olfactory lobes. Lateral 

 ventricles. Mid-brain. Hind-brain. — Cerebellum. Medulla. — Previous in- 

 vestigations. Huxley. Miklucho-Maclay. Wilder. Organs of sense. 



