Gl. 



20 mm. embryo. 

 Text-fig. 10. 



,Sio 



; Sp.Gn2 

 vro 



50 mm. stage. View of the occipital region. Three ventral roots 

 are included in the skull, v 1-v 9, and the next, v 10, joins a dorsal 

 root to form the first mixed nerve. 



