CHAP. XVI.] 



SOME OTHER MAMMALS. 



265 



and lower Vertebrates have almost ceased to exist. The 

 transverse depression which divides the two bodies into 

 four (' corpora quadrigemina '), though present in all Quad- 

 rupeds, divides them variously. Thus in nearly all the 

 lower classes, as well as in most Rumi- 

 nants and Solipedes, the anterior segments 

 are larger than the posterior (fig. 81) ; 

 while in Carnivora and in some of the 

 Cetacea, such as the Porpoise (fig. 77), the 

 posterior segments are usually the larger. (Soiiy.) A, olfactory 

 In many Quadrupeds, however, the anterior Hemisphere ^ ce- 

 and the posterior segments are nearly equal rebeiium ; H, spinal 

 in size. The degree of development of the 

 posterior segments seems to be often in accordance with 

 that of the Cerebellum with which they are in close 

 structural connection. 



FIG. 79. 



PIG. 80. 



'la 



FIG. 79. Cerebellum of the Cat, upper and posterior aspect. (Ferrier.) 

 FIG. 80. Cerebellum of the Dog, upper and posterior aspect. (Ferrier.) 



The Cerebral Hemispheres, narrowed in front, are 

 more or less elongated and ovoid in form except in Seals, 

 Porpoises and Dolphins (figs. 77, 101), in which the 

 transverse diameter of these segments may even exceed 

 the longitudinal. They are relatively small in the lower 

 orders of Quadrupeds, as may be seen from the figure 



