Chap. VII. Structure of the Brain. 199 



unknown agencies which induced them were to act in a more 

 constant manner, aided by long-continued intercrossing. Such 

 variations come under the provisional class, alluded to in our 

 second chapter, which for the want of a better term are often 

 called spontaneous. Nor do I pretend that the effects of sexual 

 selection can be indicated with scientific precision ; but it can be 

 shewn that it would be an inexplicable fact if man had not been 

 modified by this agency, which appears to have acted powerfully 

 on innumerable animals. It can further be shewn that the 

 differences between the races of man, as in colour, hairiness, 

 form of features, &c, are of a kind which might have been 

 expected to come under the influence of sexual selection. But in 

 order to treat this subject properly, I have found it necessary to 

 pass the whole animal kingdom in review. I have therefore 

 devoted to it the Second Part of this work. At the close I shall 

 return to man, and, after attempting to shew how far he has 

 been modified through sexual selection, will give a brief summary 

 of the chapters in this First Part. 



Note ox the PvESemblances and Differences in the Structure 

 and the Development of the Brain in Man and Apes. By 

 Professor Huxley, F.R.S. 



The controversy respecting the nature and the extent of the differ- 

 ences In the structure of the brain in man and the apes, which arose 

 some fifteen years ago, has not yet come to an end, though the subject 

 matter of the dispute is, at present, totally different from what it was 

 formerly. It was originally asserted and re-asserted, with singular 

 pertinacity, that the brain of all the apes, even the highest, differs from 

 that of man, in the absence of such conspicuous structures as the 

 posterior lobes of the cerebral hemispheres, with the posterior cornu of 

 the lateral ventricle and the hippocampus minor, contained in those 

 lobes, which are so obvious in man. 



But the truth that the three structures in question are as well deve- 

 loped in apes' as in human brains, or even httei ; and that it is character- 

 istic of all the Primates (if we exclude the Lemurs) to have these parts 

 well developed, stands at present on as secure a basis as any proposition 

 in comparative anatomy. Moreover, it is admitted by every one of the 

 long series of anatomists who, of late years, have paid special attention to 

 the arrangement of the complicated sulci and gyii which appear upon 

 the surface of the cerebral hemispheres in man and the higher apes, 

 that they are disposed after the very same pattern in him, as in them. 

 Every principal gyrus and sulcus of a chimpanzee's brain is clearly 

 represented in that of a man, so that the terminology which applies to 

 the one answers for the other. On this point there is no difference of 

 opinion. Some years since, Professor Bischoff published a memoir 70 on 

 the cerebral convolutions of man and apes; and as the purpose of 

 my learned colleague was certainly not to diminish the value of the 



70 'Die Grosshirn-Windungen des MenscheD ;' ' Abhandlungen dor K 

 Bayerischen Akademie.' Bd. x,, 1868. 



