No. 506] DARWIN AND MUTATION THEORY 



87 



considerable proof that it is itself a mutant Prom 

 (Ei/ntlicni gniuriiflora, and none whatever for the asser- 

 tion, often made, that it is a hybrid. As at least nine 

 of its mutants have also bred true through many genera- 

 tions in pedigree cultures and doubtless had been con- 

 stant forms for a long time in a state of nature, there 

 appears to be no ground for Darwin's fear that, granting 

 the occurrence of mutation, the mutants would be liable 

 to speedy extermination through inability to propagate 

 Of course this would not be the case with even a single 

 self-fertilizing plant and it would not he true with ani 

 mal mutants if, like plant mutants, they were produced 

 in numbers by the mutating stock. As to swamping by 

 intercrossing, it has been shown that, under Mendel's 

 law, in the extreme case of the production of a solitary 

 mutant obliged to cross, with the parent form, if it pos- 

 sesses characteristics having a certain relation to the 

 parent, it can establish a race like itself and even sup- 

 plant the parent form, if it is only as well fitted for the 

 battle of life as is the progenitor/" 



If Darwin had known these facts he would not have 

 written, or he would have greatly amended, the following 

 passage: 



through an internal force or tendency into, for instance, one furnished 

 with wines, will he almost compelled to assume, in opposition to all 



denied that such abrupt and great changes of structure are widely dif- 

 ferent from those which most species apparently have undergone. He 

 will further be compelled to beheve that many structures beautifully 

 adapted to all the other parts of the same creature and to the surround- 

 ing conditions, have been suddenly produced; and of such complex and 

 wonderful co-adaptations, he will not be able to assign a shadow of an 

 explanation. He will be forced to admit that these great and sudden 

 transformations have left no trace of their action on the embryo. To 

 admit all this is, as it seems to me, to enter into the realms of miracle, 

 and to leave those of science. 31 



Of course Mr. Darwin was not entirely oblivious to the 

 fact that every important advance in knowledge must 



80 See Lock's "Variation, Heredity and Evolution," 1906, p. 205. 

 ""Origin of Species," 6th ed., p. 204. See also, ibid., p. 202. 



