ing compromise between the two diverse heredities, the one seems largely to prevail over the other in certain parts, yet it is difficult to suppose that there is not a minute interrelation between all the parts: and perhaps the significant fact that every mulatto, though darker or lighter, is at least brown, not purely black or purely white, gives us the best key to the true nature of the situation.
So far, I have been tacitly but intentionally taking for granted the very principle which I set out to prove, in order fully to put the reader in possession of the required point of view. The question now arises, Where in this series of events is there room for any fresh element to come in? Can any man ever be anything other than what some of his ancestors have been before him? And, if not, how is progress or mental improvement possible? That men have as a matter of fact risen from a lower to a higher intellectual position is patent. That some races have outstripped other races is equally clear. And that some individual men have surpassed their fellows of the same race and time is also obvious. How are we to account for these facts without admitting that new elements do at sundry times creep in by chance, in the false and unphilosophical sense of the word? How can we get advance unless we admit that exceptional children may be born from time to time with brains of exceptional functional value, wholly uncaused by antecedents in any way?
The answer to this question is really one of the most important in the whole history of mankind. For on the solution of the apparent paradox thus propounded depend two or three most fundamental questions. It is by this means alone that we can account, first, for the existence of great races like the Greeks or the Jews. It is by this means alone that we can account, secondly, for genius in individuals. And it is by this means alone that we can account, thirdly, for the possibility of general progress in the race. It is surprising, therefore, that the question has so little engaged the attention of evolutionary psychologists at the present day.
There are only two conceivable ways in which any increment of brain-power can ever have arisen in any individual. The one is the Darwinian way, by "spontaneous variation"—that is to say, by variations due to minute physical circumstances affecting the individual in the germ. The other is the Spencerian way, by functional increment—that is to say, by the effect of increased use and constant exposure to varying circumstances during conscious life. I venture to think that the first way, if we look it clearly in the face, will be seen to be practically unthinkable: and that we have therefore no alternative but to accept the second. Deeply as I feel the general importance of Darwin's theory of "spontaneous variation" (using the words in the sense in which he always used them), it seems to me that that theory can not properly be applied to the genesis of a nervous system, or of any part of a nervous system, and that in this case we must rather come