CHAP. XVII.] THE BRAIN OF QUADRUMANA. 303 



sphere that are most characteristic of the Primates, and 

 offer the most striking differential features from other 

 Mammalia." The posterior part of the ' Hippocampal 

 Fissure,' named ' Calcarine ' by Huxley (fig. 120, /. c), 

 is peculiar to Man and the Quadrumana. It sometimes 

 persists deeply marked in the lowest forms, when every 

 other trace of a fissure except the Sylvian has disappeared. 

 The Sylvian, however, is found in lower Mammals, and 

 the ' Calloso-Marginal,' which is usually very distinct 

 among Quadrumana (fig. 120, a. cm), seems also to exist 

 in the great majority of Mammals. 



The part of the outer face of the Hemisphere known in 

 Man as the ' Supra-Marginal Lobule' (figs. 133, 142, tf fc 8 ), 

 existing above the posterior end of the fissure of Sylvius, 

 was said by Gratiolet to be invariably absent, in the great 

 ' man-like' Apes. But, according to Prof. Rolleston,* " the 

 development of this part is very frequently asymmetrical 

 on the two sides of the same brain, and its development 

 in any two human brains, taken at hap-hazard, is pretty 

 sure to present the greatest differences." It would seem, 

 moreover, that a simple representative of this structure is 

 unquestionably to be found in the Chimpanzee, that it is 

 better developed in the Orang (fig. 121, b 3 , and posterior 

 thereto), and that it is larger still in the Gorilla (fig. 117): 

 so that the supposition as to its absence in these creatures 

 was a mistake, and we certainly have not in this direction, 

 as Gratiolet thought, a differentiating mark between the 

 brain of the great Apes and that of Man. 



The several Convolutions will not now be further referred 

 to, but the names of many of them may be ascertained 

 by a careful study of figs. 115121. Although the 

 letters and numbers affixed to corresponding parts in these 

 several representations of the brain of the Chimpanzee, 

 * Loc. cit., p. 212. 



