was to assert the claims of one of what may be called the "pre-efficients" 1 of eminent men, the importance of which had been previously overlooked ; and I had yet to work out more fully its relative efficacy, as compared with those of education, tradition, fortune, opportunity, and much else. It was therefore with no ordinary interest that I studied M. de Candolle's work, finding in it many new ideas and much confirmation of my own opinions ; also not a little criticism (supported, as I conceive, by very imperfect biographical evidence,)' of my published views on heredity. I thought it best to test the value of this dissent at once, by limiting my first publication to the same field as that on which M. de Candolle had worked-namely, to the history of men of science, and to investigate their sociology from wholly new, ample, and trustworthy materials. This I have done in the present volume ; and I am confident that
I Or, "all that has gone to the making of." The word was suggested to me.
2 Reference may be made to a short review by me of M. de Candolle's work, in the Fortnightly Review, March 18-11