198 



^OOLOGY 



SECT- 



IS rounded and placed at the end of a hollow stalk : a shorter 

 offshoot of the roof of the diencephalon may perhaps represent 

 a rudimentary pineal eye. Behind the pituitary body is a saccus 



P> 



FIG. 818. Salmo fario. Dorsal (A), ventral (B), and lateral (C) views of brain. BG, or Bas G. 

 corpora striata ; ch, crossing of optic nerves ; G. p, pineal body ; HH, cerebellum ; Hyp. 

 pituitary body ; Inf. infundibulum ; L. ol. olfactory lobes ; Med, spinal cord ; MH, optic lobes ; 

 NH, medulla oblongata ; Pall, pallium ; Sv. saccus vasculosus ; Tr. Opt. optic tracts ; U, L, 

 lobi inferiores ; VH, prosencephalon ; IX, cerebral nerves ; XII, 1, first spinal (hypoglossal) 

 nerve ; #, second spinal nerve. (From Wiedersheim's Vertebrata.) 



vasculosus (s. v.). The optic nerves do not form a chiasma, but simply 

 cross one another or decussate (Ch.) on leaving the brain, the 

 right nerve going to the left, and the left nerve to the right eye. 



