cox, DARWIN AND THE MUTATION THEORY 435 



have been thought by Darwin entirely independent of selection, he gave it 

 as his judgment, as late as 1875, that 



"It is certain that the Ancon and Mauchamp breeds of sheep, and almost certain 

 that the Niata cattle, tm-nspit and pug-dogs, jumper and frizzled fowls, short-faced 

 tumbler pigeons, hook-billed ducks, &c., suddenly appeared in nearly the same 

 state as we now see them. So it has been with many cultivated plants." ' 



Now, considering, as I said a moment ago, that Mr. Darwin's theory of 

 the origin of species by means of natural selection has for its main foundation- 

 stones facts derived from observation of the effects of man's selection among 

 domesticated animals and plants (without which, indeed, he admitted that 

 he had no actual proof of the operation of natural selection), it is difficult 

 to realize the state of mind which led Mr. Darwin to add to the sentence 

 just quoted the following caution: 



"The frequency of these cases is likely to lead to the false belief that natural 

 species have often originated in the same abrupt manner. But we have no evidence 

 of the appearance, or at least of the continued procreation under nature, of abrupt 

 modifications of structure; and various general reasons could be assigned against 

 such belief." 



I am not aware that Mr. Darwin ever presented definite and convincing 

 reasons for the sharp demarkation here attempted, and, indeed, I can not 

 see how the state of knowledge in his time could have justified his doing so, 

 for, as I have already stated, mutations had not been much looked for 

 among feral plants and animals. In fact, by absolutely excluding from his 

 theory the idea that mutation could occur under nature, Mr. Darwin, by 

 the force of his great authority and influence, would have prevented a care- 

 ful weighing of the pros and cons, if the human mind had at that time been 

 prepared to weigh them. It is practically only since the Darwinian hypoth- 

 eses have themselves been subjected to prolonged scrutiny, and since de 

 Vries and a few others entered upon detailed experimental examination of 

 this particular subject, within the last twenty years, that the matter can be 

 said to have received anything like scientific treatment. 



But, after all, Darwin was not wholly prejudiced against a belief in the 

 occurrence of mutations in nature, for he several times expressed the opinion 

 that the establishment of such a fact would in some ways be an advantage 

 to the evolution theory. For instance, in a letter of August, 1860, to W. H. 

 Harvey, he says : 



"About sudden jumps: I have no objection to them — they would aid me in 

 some cases. All I can say is that I went into the subject and found no evidence to 

 make me believe in jumps; and a good deal pointing in the other direction." - 



1 "Animals and Plants Under Domestication," 2d ed., 1875, Vol. II, pp. 409-10. 



2 " More Letters," Vol. I, p. 166. See also, " Life and Letters," 1886, Vol. II, p. 333. 



