XIII 



PHYLUM CHORDATA 



213 



body (hp.) is rounded and placed at the end of a hollow stalk • a 

 shorter offshoot of the roof of the diencephalon may perhaps 



ME 



VEiPall) 



IW 



-Med, 



E^M vLSv m 



Fig. 866.— Salmo fario. Dorsal (A), ventral (B), and lateral (C) views of brain. BG., Bas. Q. 

 corpora striata ; ck, crossing of optic nerves ; G. p, pineal body ; fiH. cerebellum ; I/^p, 

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

 Nff. medulla oblongata ; Pall, pallium ; Sv. saccus vasculosus ; Tr. Opt. optic tracts ; [/, L. 

 lobi inferiores ; VH, prosencephalon ; / — X, cerebral nerves ; X//, 1, first spinal (hypoglossal) 

 nerve; 3, second spinal nerve. (From Wiedersheim's Vertehrata.) 



represent a rudimentary pineal eye. Behind the pituitary body 

 is a saccus vasculosus (s, v.). The optic nerves do not form a 

 chiasma, but simply cross one another, or decussate (Oh-), on 

 VOL. II O 



