40 



NERVOUS SYSTEM OF VERTEBRATES. 



the rapid growth of those parts of the brain which are destined to 

 become large and important in the aduk. One result of these 

 forces is the appearance early in embryonic life of certain bends 



Fig. 19. — The history of the neuromeres in the bony fish and the chick. A, B, C, 

 three stages in the development of the bony fish, as seen from the right side. D, E, 

 the brain of the chick. After Hill. The letters c. e. g. mark corresponding fur- 

 rows in the chick brain; ep. i, ep. 2, anterior and posterior epiphyses; inf. inferior 

 lobe; p. com., posterior commissure. The neuromeres are indicated by Arabic 

 numerals. 



or flexures. These are illustrated in the figures which show the 

 neuromeres (Figs. 18, iq) and also in Figure 20. In the neck 

 region, owing to the bending of the head, the brain is bent down- 



