144 



( '( )MPA i; ATI VE AX ATOM V. 



The brain of Anura, and still more that of Gymnophiona, 

 reaches a much higher stage than that of Urodeles, which 

 retains to a greater extent a resemblance to the brain of Fishes. 

 In Rana, moreover, the fore-parts of the hemispheres in the 

 region of the oll-irtnry lobi-s an- fused together in the middle line; 

 in Urodeles and Protopterus they remain distinct throughout. In 

 < Vratodus the hemispheres are fused together dorsally, and in 

 Ganoids ventrally. 



Olfactory lobes may be largely (Amphibia, Polypterus, 

 Ceratodus), only moderately (Sturgeons), or not at all (Protopterus)- 

 developed. 



Reptiles. 



The brain of Reptiles reaches a considerably higher stage of 

 development than that of the forms already described, and this is 



-71 



\\ 



Fn:. 110. J 



Pii.ixmvoitM (yi//;/jm-//w;////- i. 

 P, from tin- ventral side.) 



A, from the dorsal. 



/'//. ccivlir;il hemispheres, narrowing anteriorly to pa^s into the olfactory tracts (7V") 

 and the olfactory lobes (Lol) ; ZII, thalaniencepbalon, with the hypophysis (H) ; 

 .I///, oiitic lohes, eni'iri'Ii'il In-hind liy t lie roots of the optic, tracts i T/-p) ; HH, 

 cerebellum; X7I, nifdulln. ohlon^nta ; /'///, I'mnth vinti'icle; A', spinal cord; 

 /, olfactory nerve ; //. optic nerve, with cliiasnia \/'/i/', ; III, oculomotor; //', 

 tro'-hle;ir nerve ; i'\ tipsi division, of the trigeminal, with its special ganglion (6? 1 ); 

 /"-', r 3 , second and tliird divisions of the trk'eniin.'il, arising from a common root 

 (V) mid ganglion (G-) ; VI, aliduccnt ; /'//, /"///, facial and auditory nerves, 

 arising from a common root ; IX, X, XI, elossopharyngeal, vagus, and spinal 

 accessory: />'/<, // .v/<, lirst and second spinal nerves; BK, Varolian bend. 



most pronounced by 

 another to a 



greater 



the individual parts 

 extent, and 



coming 



to overlie one 



of both the peripheral and basal poi 



by the larger development 

 tions of the hemispheres. 



