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462 was, fifty years later, to be the most important basis of the work upon which he was to spend his life, the most secure support of that doctrine of descent which was founded by Lamarck in the very year of Darwin's birth, and which was at that time received with warm approbation by his grandfather, Erasmus Darwin.

Of all the naturalists of the nineteenth century Charles Darwin has certainly had the greatest success and the most powerful influence. We often, indeed, call the last forty years the "Darwinian age." And if we investigate more closely the causes of this unexampled success we will see, as I have repeatedly said, that they depend upon three important services rendered: (1) The total reform of the theory of descent or doctrine of Lamarck; (2) the founding of the new theory of natural selection, the special Darwinian theory; and (3) the development of the science of the evolution of man, that most important deduction from the theory of descent, which far exceeds in significance all other problems of the doctrine of evolution.

I shall to-day, before this zoological congress, speak only of the last-named service of Darwin, and do this for the especial purpose of showing critically the certainty to which we have attained in our present knowledge of the origin of man and of the various branches of his genealogical tree. That this is one of the most important of all scientific questions is to-day no longer disputed. For all other problems which the human mind can investigate and understand are conditioned chiefly by the psychological theory of perception, and this again depends upon the animal nature of man, upon his origin, his development, and his mental powers. With good reason, then, did the greatest zoologist of our century, Thomas Huxley, characterize this problem as the "question of questions for mankind," as the "problem which underlies all others and is more deeply interesting than any other." This was done in 1863 in the second of those three masterly essays which for the first time thoroughly examined the "Evidence as to man's place in nature" in the light of the Darwinian theory; the first, treating of the anthropoid apes, the second of the relations of man to the next lower animals, the third of some fossil human remains. Darwin himself, in 1859, in his principal work, On the Origin of Species, had purposely avoided referring to these consequences of his doctrine except in a brief, significant, passing allusion that, by its means, light would be thrown on the origin of man and his history. Later (1871) in his famous work on The Descent of Man, and Selection in Relation to Sex, Darwin brought forward in a most able manner, both the morphological and the historical as well as the physiological and psychological side of this problem.

I had myself, in 1886, in my Generelle Morphologie, estimated the importance of the "history of the development of organisms as bearing upon anthropology," and especially remarked that the fundamental biogenetic law held good for man also; with him, as with all other organisms, there is the most intimate causal connection between