DE VniES' "MUTATION" g3 



As to the nature of these causes, natural 

 selection is dumb. For its purpose, variation 

 IS simply assumed to be a fact, and Darwin's 

 acknowledged ignorance as to how variation 

 is brought about is expressed in the term 

 "spontaneous variation." Until variation has 

 played its part by producing new and various 

 forms, selection has no function or office to 

 perform. Then it simply decides which forms 

 shall survive by destroying the rest. As Wi- 

 gand has pointed out, selection does not do 

 more than determine the survival of what is 

 offered to it, and does not create anything 

 new. As DeVries very strikingly puts it, *'It 

 is only a sieve, and not a force of nature, no 

 direct cause of improvement, as many of Dar- 

 win's adversaries, and unfortunately many of 

 his followers also, have so often asserted. It 

 is only a sieve which decides which is to live 

 and which is to die ... . With the single steps 

 of evolution it has nothing to do. Only after 

 the step has been taken, the sieve acts, elimi- 

 nating the unfit.'' Thus Prof. Cope's point 

 that Darwin's theory does not explain the 

 "origin" of the fittest, is well taken, or as Mr. 

 Arthur Harris puts it, "Natural selection may 

 explain the survival of the fittest, but it can- 

 not explain the arrival of the fittest." 



It was around this question of the "causes" 



