14 THE THEORY OF EVOLUTION 



emphasize the distinction between the two aspects 

 of Darwin's work. His argument, supported by the 

 amazing mass of proof, which had been gathered 

 through twenty laborious years, gradually con- 

 vinced scientific men that the theory of evolution 

 offered by far the most probable and satisfactory 

 solution of the problems of the living world. On 

 the other hand, Darwin's explanation of the evolu- 

 tionary process, commonly known as the theory of 

 :4 Natural Selection," won no such universal accept- 

 ance and has been a subject of controversy, more 

 or less acrimonious, from the time of its first pro- 

 mulgation to the present day. On the other hand, it 

 must be recognized that Natural Selection played 

 a very important part in bringing about the general 

 acceptance of evolution, for it was the first sugges- 

 tion of a reasonable and intelligible factor in pro- 

 ducing the transformation of species. Huxley's 

 account of his own attitude of mind is well adapted 

 to explain this. He tells us that before 1858, he 

 had no definite opinions on the subject and this 

 for two reasons: "firstly, that up to that time, the 

 evidence in favour of transmutation was wholly 

 insufficient; and, secondly, that no suggestion re- 

 specting the causes of the transmutation assumed, 

 which had been made, was in any way adequate 

 to explain the phenomena.' 3 l Huxley was never 

 fully satisfied with the doctrine of natural selection, 

 but, nevertheless, that doctrine had a large share 



1 Life and Letters, Vol. II. 



