148 



THE DEVELOPMENT OF THE CHICK 



FIG. 83. Five stages in the history of the neuromeres of the brain of the 

 chick. (After Hill.) All figures drawn from preparations of the embryonic 

 brain dissected out of the embryo. 



A. Neural groove in an embryo with 4 somites. Right profile view, x 44, 



B. Brain of a 7 s embryo, 26 hours old. Dorsal view; the three anterior 

 neuromeres are practically obliterated, x 44. 



C. Brain of 14 s embryo. Dorsal view, x 44. The neuromeres have 

 now disappeared in the mid-brain region. 



D. Right side of the brain of a chick embryo, 47 hours old. x 44. 



E. Right side of the brain of an embryo, 80 hours old. x 17. 



1-11, Neuromeres 1 to 11. Ill, V, VII, interneuromeric grooves. A'f., 

 Root of acustico-facialis (seventh and eighth cranial nerves), au. vs., Audi- 

 tory pit. ep., Epiphysis. r., Groove between the tel- and diencephalon. 

 s., Groove between the par- and synencephalon. Tr., Root of trigeminus. 



