156 Evolution and Adaptation 



standard of successive generations could ever be raised be- 

 yond the most extreme fluctuating variation. At least this 

 appears to be the case if individual, fluctuating variations be 

 the sort selected, and it is to this kind of variation to which 

 Weismann presumably refers. Without discussing this point 

 here, let us examine further what Weismann has to say. He 

 thinks that while in each form there may be a very large 

 number of possible variations, yet there are also impossible 

 variations as well, which do not appear. " The cogency, the 

 irresistible cogency as I take it, of the principle of selection 

 is precisely its capacity of explaining why fit structures al- 

 ways arise, and this certainly is the great problem of life." 

 Weismann points out that it is a remarkable fact that to-day, 

 after science has been in possession of this principle for 

 something over thirty years, " during which time she has bus- 

 ily occupied herself with its scope, the estimation in which 

 the theory is held should be on the decline." " It would be 

 easy to enumerate a long list of living writers who assign to 

 it a subordinate part only in evolution, or none at all." 

 " Even Huxley implicitly, yet distinctly, intimated a doubt 

 regarding the principle of selection when he said : ' Even if 

 the Darwinian hypothesis were swept away, evolution would 

 still stand where it is.' Therefore he, too, regarded it as 

 not impossible that this hypothesis should disappear from 

 among the great explanatory principles by which we seek 

 to approach nearer to the secrets of nature." 



Weismann is not, however, of this opinion, and believes 

 that the present depression is only transient, because it is only 

 a reaction against a theory that had been exalted to the 

 highest pinnacle. He thinks that the principle of selection 

 is not overestimated, but that naturalists imagined too quickly 

 that they understood its workings. " On the contrary, the 

 deeper they penetrated into its workings the clearer it ap- 

 peared that something was lacking, that the action of the 

 principle, though upon the whole clear and representable, yet 



