XX PREFACE TO THE FIRST EDITION. 



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 oj 

 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- 

 clusion is finally drawn, that man will never pass over 

 these limits : " We shall never know that ! Ignorabimus ! " 



As the unanimous thanks of the Ecclesia militans have 



