c6 NERVOUS SYSTEM OF VERTEBRATES. 



downward in front of the gill slit. It has been suggested that 

 the epibranchial placodes represent ancestral sense organs whose 



Vagus root gang, 



Accessory root (^ang. 



IX root gang. 



Cong petros. 

 N tymp 



Br to 

 carotid plexus 



Sympathetic. 



Fig. 32.— Reconstruction of the peripheral nerves in 

 17. 5 mm. long. From Streeter. 



Fronep 



a six weeks human embryo, 



