200 THE DESCENT OF MAN 



late period; and thus they reveal the old lines of descent 

 or of true affinity. 



We can further see why a great amount of modification 

 in some one character ought not to lead us to separate widely 

 any two organisms. A part which already differs much from 

 the same part in other allied forms has already, according to 

 the theory of evolution, varied much; consequently it would 

 (as long as the organism remained exposed to the same ex- 

 citing conditions) be liable to further variations of the same 

 kind; and these, if beneficial, would be preserved, and thus 

 be continually augmented. In many cases the continued 

 development of a part, for instance, of the beak of a bird, 

 or of the teeth of a mammal, would not aid the species in 

 gaining its food, or for any other object; but with maa we 

 can see no definite limit to the continued development of the 

 brain and mental faculties, as far as advantage is concerned. 

 Therefore in determining the position of man in the natural 

 or genealogical system, the extreme development of his brain 

 ought not to outweigh a multitude of resemblances in other 

 less important or quite unimportant points. 



The greater number of naturalists who have taken into 

 consideration the whole structure of man, including his 

 mental faculties, have followed Blumenbach and Cuvier, 

 and have placed man in a separate Order, under the title 

 of the Bimana, and therefore on an equality with the orders 

 of the Quadrumana, Oarnivora, etc. Recently many of our 

 best naturalists have recurred to the view first propounded 

 by Linnaeus, so remarkable for his sagacity, and have placed 

 man in the same Order with the Quadrumana, under the title 

 of the Primates. The justice of this conclusion will be ad- 

 mitted; for, in the first place, we must bear in mind the 

 comparative insignificance for classification of the great de- 

 velopment of the brain in man, and that the strongly marked 

 differences between the skulls of man and the Quadrumana 

 (lately insisted upon by Bischoff, Aeby, and others) appar- 

 ently follow from their differently developed brains. In the 

 second place, we must remember that nearly all the other 



