GENERAL 



been of great importance in the isolation of species 

 at any rate in the animal world. 



The views of Auguste Weismann, Darwin's most 

 distinguished follower among biologists, must also 

 fall under consideration, not only in relation to his 

 controversy with the Lamarckians. 



Thereafter we must ask whether there are still 

 any ''unknown factors" in organic evolution, or 

 whether those named suffice to explain the facts. 



But prior to our study of the factors of organic 

 evolution we must devote a chapter to the princi- 

 ples, everywhere unquestioned, which render it 

 possible. These are the correlative and contrasted 

 principles of heredity and variation. Here, again, 

 we shall discover that recent work has been of 

 great significance, and, in relation to heredity, we 

 shall have to note the rediscovery of the brilliant 

 but obscure work quietly done by an Austrian 

 abbot, Gregor Mendel, some forty years ago, thrown 

 into the background by the Origin of Species and 

 the controversy that followed its publication, but 

 recently revived and amplified by the work of 

 Hugo de Vries, of Amsterdam, and William Bate- 

 son, of Cambridge. 



After attempting duly to discuss heredity and 

 variation, and the factors of organic evolution, 

 we must devote ourselves for a few pages to the 

 recent study of the inference from organic evolu- 

 tion which so immediately concerns us viz., the 

 origin of man. Here we shall discover at least 

 three new lines of evidence for which Spencer 

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