4/8 'Journal of Comparative Neurology and Psychology. 



ni ec 



Fig. 14. Section from same series as Fig. 13, passing tbrougli tlie tip of the 

 anterior head cavity on the left side and in front of this cavity on the right 

 side. X 150. 



Fig. 15. Squalus ac, 42 somites. Left view of a model of the brain, meso- 

 derm, ganglia and mesectoderm derived from the neural crest. The auditory 

 pit with the ectoderm bordering it are also shown, x ^0. The boundaries of 

 the mesoderm are marked in black lines. 3, //, 5, somites of Van Wijhe's 

 series. 



