THE DESCENT OR ORIGIN OF MAN 205 



If we imagine three lines of descent proceeding from a com- 

 mon stock, it is quite conceivable that two of them might 

 after the lapse of ages be so slightly changed as still to 

 remain as species of the same genns, while the third line 

 might become so greatly modified as to deserve to rank as 

 a distinct Sub-family, Family, or even Order. But in this 

 case it is almost certain that the third line would still retain 

 through inheritance numerous small points of resemblance 

 with the other two. Here, then, would occur the difficulty, 

 at present insoluble, how much weight we ought to assign 

 in onr classifications to strongly marked differences in some 

 few points — that is, to the amount of modification under- 

 gone; and how much to close resemblance in numerous 

 unimportant points, as indicating the lines of descent or 

 genealogy. To attach much weight to the few but strong 

 differences is the most obvious and perhaps the safest 

 course, though it appears more correct to pay great atten- 

 tion to the many small resemblances, as giving a truly 

 natural classification. 



In forming a judgment on this head with reference to 

 man, we must glance at the classification of the Simiadse. 

 This family is divided by almost all naturalists into the 

 Catarrhine group, or Old World monkeys, all of which are 

 characterized (as their name expresses) by the peculiar 

 structure of their nostrils, and by having four premolars in 

 each jaw; and into the Platyrhine group or New World 

 monkeys (including two very distinct sub-groups), all of 

 which are characterized by differently constructed nostrils, 

 and by having six premolars in each jaw. Some other 

 small differences might be mentioned. Now man unques- 

 tionably belongs in his dentition, in the structure of his 

 nostrils, and some other respects, to the Catarrhine or Old 

 World division; nor does he resemble the Platyrhines more 

 closely than the Catarrhines in any characters, excepting 

 in a few of not much importance and apparently of aa 

 adaptive nature. It is therefore against all probability that 

 some New World species should have formerly varied and 



