MUTATION AND SMALL VARIATION xxxix 



of mutations both numerous and minute, we should wish 

 to know how such mutations are to be distinguished from 

 continuous variations. To say, with de Vries, that 

 selection of individual differences is powerless to raise 

 permanently the mean of a species, seems perilously like 

 begging the question. As soon as the mean had been 

 permanently raised, the result would be claimed as a 

 mutation.' x The position is as follows. Darwin assumed 

 that selection of minute differences would permanently 

 raise the mean of the species. De Vries and others 

 believe they have proved that selection of certain 

 minute differences cannot thus raise the mean. Should 

 this conclusion be hereafter established it is obvious that 

 the variational material for evolution would be reinforced 

 by no new category. The only effect would be to reduce 

 the old category. The power which Darwin and others 

 believed to reside in minute variations generally would 

 be shown to exist in a part and not the whole of these. 

 Our knowledge would be widened by the revelation of 

 weakness in the part taken away, not by the strength of 

 the part left behind ; and there would be no justification 

 for speaking of the variations included in the latter as 

 Mutations. 



I should have thought that Bateson, instead of urging 

 upon us the facts we had learnt so long ago, would have 

 had his own eyes opened by the blue Andalusian, and that 

 he would have been driven to realize the uselessness for 

 evolution of many a result which the breeder can attain. 

 He might even have been led to include in the category 

 of things valueless for the study of evolution not only 

 composite forms which cannot be depended upon to 

 reproduce themselves by heredity, but also the great mass 

 of teratological phenomena — supernumerary toes and 

 1 Nature, vol. lxxv, 1907, April 18, p. 579. 



