mental atmosphere in which the two children are respectively nurtured; "—Ibid. p. 178.
Now, since so little in man that is mental is inborn, and so much is acquired, deductively it seems probable that Mr. Buckle is right. It may, however, be argued, that since survival of the fittest has caused in different environments the various races of mankind to differ as regards their physical characters, it is highly likely that it has caused them to differ as regards their mental characters also. But here crops up that old and fertile source of error, the idea that the mind is an organ, not merely the product of the functional activity of an organ. The mind is the product of the functional activity of the nervous tissue, mainly of the brain, and therefore is comparable, not to other organs, but to the products of their functional activities, using the words in their widest sense. The brains of various races differ in size and shape, and may differ structurally in many other respects, not as yet observed by us, and these differences have possibly or probably for their concomitants mental differences of more or less importance, but it is doubtful whether these latter are of the kind commonly supposed.
We have seen that organic evolution consists essentially of a process of gradual structural modification, whereby evolving species are brought into harmony with environments gradually increasing in complexity. Counting from unicellular organisms, the process began with the evolution of multicellular organisms, was continued by the evolution of complex and heterogeneous shapes and structures in multicellular organisms, and is proceeding by the evolution, in the higher of them, of an immense power of varying in response to stimulation from the environment, by means of which they are placed in closer correspondence with it. Contempora-
