462 Evolution and Adaptation 



determine, whether, if after several mutations have succes- 

 sively appeared in the same direction, there would be an 

 established tendency to go on in the same direction in some 

 of the future mutations. But here again we must wait until 

 we have more data before we attempt to build up a theory 

 on such a basis. 



The attacks on the Darwinian school by the followers of 

 the modern school of experimentalists are with few exceptions 

 based on the assumption that the natural selectionists pre- 

 tend that their principle is a sort of creative ior-ee, — a factor 

 in evolution in the sense of being an active agent. This 

 assumption of the selectionists has led many of them to ig- 

 nore a fundamental weakness of their theory, namely, the 

 origin of the variations themselves, although Darwin did 

 not overlook or ignore this side of the problem, or fail to 

 realize its importance, as have some of his more ardent, but 

 less critical, followers. They have contented themselves, as a 

 rule, with pointing out that certain structures are useful, and 

 this has seemed to them sufficient proof that the structures 

 must have been acquired because of their value. In contrast 

 to this complacency of the selectionists, we find here and 

 there naturalists who have, from time to time, insisted that 

 the scientific problem of evolution is not to be found in the 

 principle of selection, but in the origin of the variations 

 themselves. It will be clear, from what has been said, that 

 this is our position also, and for us adaptation itself does not 

 appear to be any more a problem that can be examined by 

 scientific methods, than the lack of adaptation. Th£-caus£§_ 

 ( of the change of whatever kind should be our immediate quest. 

 The destruction of the unfit, because they can find no place 

 where they can exist, does not explain the origin of the fit. 



Over and beyond the primary question of the. origin of the 

 adaptive, or non-adaptive, structure is the fact that we find 

 that the great majority of animals and plants show distinct 

 evidence of being suited or adapted to live in a special envi- 



