90 



BRAIN AND BODY OF FISH 



the reader to contrast the pattern of the three members of this 

 group. The medulla of the turbot is remarkably broad anteriorly, 

 and this feature is particularly evident in the serial sections ; the 

 somatic-sensory lobes are large and project more prominently as 



Brill 



PLATE 17. 



Turbot. 



Halibut. 



p.e.b. — Primitive end-brain, op.l. — Optic lobe, c.l.m. — Cerebellum, a.t. — Acoustic 

 tubercle, s.s.l. — Somatic-sensory lobe. v.l. — Vagal lobe. l.i. — Lobus inferior. 

 s.v. — Saccus vasculosus. p.g. — Pituitary gland. o.n. — Optic nerves, 

 decussating. 



one passes caudaUy when they become separated from each other 

 and round a somewhat quadrilateral rhomboid fossa ; the lateral 

 margins of which bulge somewhat through the inward projection 

 of the small facial lobes. The motor nuclei of the vagal or the nuclei 

 ambigui are very well-developed. When the lining of the ventricles 

 is closely examined the epithelium is seen to be much thickened and 

 the lower angle of the ventricle is V-shaped and occupied by a fan- 



