1865.] DUKE OF ARGYLL. 21/ 



through sexual selection. The duke may think this insuffi- 

 cient, but that is another question. All analogy makes me 

 quite disagree with the Duke that the difference in the beak, 

 wing and tail, are not of importance to the several species. 

 In the only two species which I have watched, the difference 

 in flight and in the use of the tail was conspicuously great. 



The Duke, who knows my Orchid book so well, might 

 have learnt a lesson of caution from it, with respect to his 

 doctrine of differences for mere variety or beauty. It may be 

 confidently said that no tribe of plants presents such grotesque 

 and beautiful differences, which no one until lately, con- 

 jectured were of any use ; but now in almost every case I 

 have been able to show their important service. It should 

 be remembered that with humming-birds or orchids, a modi- 

 fication in one part will cause correlated changes in other 

 parts. I agree with what you say about beauty. I formerly 

 thought a good deal on the subject, and was led quite to 

 repudiate the doctrine of beauty being created for beauty's 

 sake. I demur also to the Duke's expression of '' new 

 births." That may be a very good theory, but it is not mine, 

 unless indeed he calls a bird born with a beak y^th of an 

 inch longer than usual " a new birth ; " but this is not the 

 sense in which the term would usually be understood. The 

 more I work the more I feel convinced that it is by the 

 accumulation of such extremely slight variations that new 

 species arise. I do not plead guilty to the Duke's charge 

 that I forget that natural selection means only the preserva- 

 tion of variations which independently arise.* I have ex- 

 pressed this in as strong language as I could use, but it would 

 have been infinitely tedious had I on every occasion thus 

 guarded myself. I will cry " peccavi " when I hear of the 

 Duke or you attacking breeders for saying that man has 



* " Strickly speaking, therefore, Mr. Darwin's theory is not a theory on 

 the Origin of Species at all, but only a theoiy on the causes which lead to 

 the relative success and failure of such new forms as may be born into the 

 world." — Scotsman y Dec. 6, 1864. 



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