140 



COMPARATIVE AN ATOM v. 



remains in an embryonic condition, and can hardly be said to have a 

 physiological function ; the brain of those Fishes in which this con- 

 dition is retained probably acts mainly as a reflex machine, 

 and there is little doubt that the mental processes 



ol 



FIG 113A. LONGITUDINAL VERTICAL SECTION THROUGH THE ANTERIOR PART OF 

 THE TELEOSTEAN BRAIN. (Founded on a figure of the Trout's brain by Rabl- 

 Riickhard.) 



2Vo, roof of the optic lobes ; Tl, torus longitiulinalis ; Cp, posterior commissure ; 

 Op, pineal gland, with a cavity (Gfp 1 ) in its interior ; Ep, Ep, the ependyma, 

 which lines the walls of the ventricles ; t, point at which the epithelial roof of 

 the secondary fore-brain (pallium. Pn) becomes continuous with the lining of the 

 anterior wall of the pineal tube: the former is folded inwards at / ; J'.cm, 

 common ventricle of the secondary fore-brain ; V.t, third ventricle ; B.ol, N.ol, 

 olfactory bulb and nerve ; C.st, corpus striatum, which was formerly taken to 

 represent the whole of the prosencephalon, and which lies on either side of the 

 middle line; Ch. n.opt, optic chiasma ; Ci, inferior commissure (Gadden) ; ''//, 

 liorizontal commissure (Fritsch) : J, infundilmlnm ; If, II 1 , hypophysis; Sv, 

 siicciis vaseulosus : Li, lobi infcriores ; Aq, aqueduct of Sylvius; tr, trochlear 

 nrrvc ; 1'itl, \':il villa ccrebclli. 



which take jilacc in the cortical gray substance of the 

 brains of higher Vertebrates do not obtain in them. 



The mid -brain r.nd cerebellum arc by far the largest 

 portions of Ihc brain (Figs. 114 and llo, MIT, ////), while the 

 thalamencepnalon is depressed between Ihe prosencephalon and 



