XIII 



PHYLUM CHORDATA 



213 



body (bp.) is rounded and placed at the end of a hollow stalk : a 

 shorter offshoot of the roof of the diencephalon may perhaps 



SgpM 



FIG. 866 -Salmo fario. Dorsal (A), ventral (B), and lateral (C) views of brain. BG., Bas. G. 

 corpora stSata; ch, crossing of optic nerves; G. p pineal body; HE. cerebellum ; Hyp, 

 pituitary body Inf. infundibulum ; L. oL olfactory bulbs ; Med, spmal cord ; ME. optic lobes , 

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

 lobi inferiores ' VII, prosencephalon ; r~X, cerebral nerves ; XII, 1, first spinal (hypoglossal) 

 nerve ; 2, second spinal nerve. . (From Wiedersheim's Vertebrata.) 



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 (Ch-\ on 



VOL. II 



