S8 NATURAL SELECTION AND 



tance of natural selection." This statement will 

 doubtless cause great satisfaction to the Duke 

 of Argyll ; but I do not know what proof can 

 be given for its truth, except the opinion of 

 Professor Geddes himself, of Mr. Herbert 

 Spencer, and of a few American biologists ; 

 according to biologists such as Mr. Russel 

 Wallace, Professor Weismann, and Mr. E. B. 

 Poulton, the tendency is now all the other way. 

 And this is admitted by Mr. Grant Allen (in 

 spite of his admiration for Spencerian psycho- 

 logy) in a very remarkable review of Professor 

 Weismann's papers On Heredity, in the 

 Academy of February i, 1890. In any case, 

 there is this difference between natural selec- 

 tion and the other alleged factors of organic 

 evolution, that they are speculations, more or 

 less metaphysical in character, whereas natural 

 selection is a fact ; it is a cause actually at 

 work in nature, and the only question is, 

 whether it is able or not to explain all the 

 phenomena. On the other hand, Mr. Spencer's 

 " differentiation and integration," Professor 

 Geddes's see-saw of "anabolism and katabo- 

 lism," Mr. Cope's " bathmism" or growth-force, 

 which acts by means of retardation and acceler- 



