AFFINITIES AND GENEALOGY. 145 



ological condition, are by far the most serviceable for classifica- 

 tion; for they can hardly be due to adaptations within a 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 exciting condi- 

 tions) 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 man we can see no definite limit to the con- 

 tinued 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 de- 

 velopment 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 con- 

 sideration 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, 

 Carnivora, &c. 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 or 

 this conclusion will be admitted: for in the first place, we must 

 bear in mind the comparative insignificance for classification 

 of the great development of the brain in man, and that the 

 strongly-marked differences between the skulls of man and the 

 Quadrumana (lately insisted upon Bischoff, Aeby, and others, 

 apparently follow from their differently developed brains. In 

 the second place, we must remember that nearly all the other 

 and more important differences between man and the Quadrumana 

 are manifestly adaptive in their nature, and relate chiefiy to the 

 erect position of man; such as the structure of his hand, foot, 

 and pelvis, the curvature of his spine, and the position of his 

 head. The family of Seals offers a good illustration of the small 

 importance of adaptive characters for classification. These 

 animals differ from all other Carnivora in the form of their 

 bodies and in the structure of their limbs, far more than does 

 man from the higher apes; yet in most systems, from that of 



11 



