1905.] 



BEAIN OF THE BLACK APE. 



25 



Baboon, it is nevertlieless important to point it out, particularly 

 so in view of the second brain, which may or may not invalidate 

 the general applicability of the above statement as to the brain of 

 Cynopithecus. 



The question of course as to the second brain is, whether its 

 differences are variations in an adult brain or are due to youth or 

 sex, or both. This smaller ape only lived for six months in the 

 Society's Gardens, and as there is no fui-ther evidence as to its age, 

 it is impossible to be certain upon the point. I am disposed, how- 

 ever, to think that this small brain is comparatively undeveloped, 

 and the differences which it shows from the larger bi'ain would 

 have lessened with age. 



Text-fig. 12. 



The same Brain as that represented in text-fig. 11 (lateral aspect). 



a. Inferior occipital fissure ; P. Parallel fissure. 

 Other lettering as in text -fig. 11. 



These differences, it wiU be observed, can be mostly explained on 

 that view. The simple calcarine fissure is simply minus the top 

 bar of the T, which will ultimately appear ; the Sylvian fissure 

 has not yet grown sufiiciently far back to meet the parallel 

 fissure ; the lower portion of the inferior temporal sulcus is 

 undeveloped ; a further growth forward of the operculum would 

 alter the bending of the intraparietal fissure and perhaps shift 

 forward the direction of the internal parieto-occipital. In fact, 

 all the peculiarities of the smaller Cynopithecus brain may con- 

 ceivably be explained on this view. 



If this be correct, we can draw the interesting inference that 

 the Semnopithecine brain is relatively to the Macacine at a lower 

 level. If, on the other hand, the differences between the two 

 brains are variations of completely adult structure, it is no longer 



