Nor is this surprising, when we see what a little way the knowledge of human evolution has spread even among the very students of Nature. Even in most works devoted to the Natural History, Anatomy, Physiology, Ethnology, and Psychology of Man, it is evident at a glance that their authors, if not ignorant, have at least a very superficial knowledge of human germ-history, and that tribal history lies far beyond them. The name of Darwin is, indeed, in every mouth. But few persons have really assimilated the theory of descent, as reformed by him few have made it part of themselves. To Show how far even biologists of repute are from thoroughly understanding the history of evolution, no more remarkable recent instance can be found than the well-known address, on The Limits of Natural Knowledge, delivered by the celebrated physio logist, Du Bois Reymond, in 1873, before the naturalists assembled at Leipzig. This eloquent address, the source of such triumph to the opponents of the theory of evolu tion, the cause of such pain to all friends of intellectual advance, is essentially a great denial of the history of evolution. No thoughtful naturalist will disagree with the Berlin physiologist when, in the first half of his address, he explains the limits of natural knowledge, as they are at present set to man by his vertebrate nature. But it is equally certain that every monistic naturalist will protest against the second half of the address, in which, not only is another limit, assumed to be different (but in reality identical), indicated for human knowledge, but the con elusion is finally drawn, that man will never pass over these limits We shall never know that Ignorabimus!