Ciiai>. VI. Affinities and Genealogy. 149 



the water, and yet they will not be brought any nearer to each 

 other in the natural system. Hence we can see how it is that 

 resemblances in several unimportant structures, in useless and 

 rudimentary organs, or not now functionally active, or in an 

 embryological condition, are by far the most serviceable for clas- 

 sification; 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 con- 

 ditions) 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. Becently 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 ot 

 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 by Bischoff, Aeby, and others) 

 apparently follow from their differently developed brains. In 

 I he 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 chiefly to the 

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



