THE CEPHALIC NEUROMERES. 



op.tr. . 



h.ri 



p.n 



FIG. 66. Same from the hasmal surface, showing on the left the more superficial neurones, fiber tracts, 

 nerve roots, and commissural fibers; on the right, the deeper ones. Note the great extension backward of the 

 fibers arising from the optic nerve, op. tt, and from the giant nerve cells of the optic ganglia, op. g 4 , and olfactory 

 lobes, ol. c l and ol. c 3 . 



