Correspondence on Biology, etc. 



enables us to understand two groups of fa<;ts which I have 

 never been able to work out satisfaxitorily by the old method. 

 These two facts are : (1) the total, or almost total, disap- 

 pearance of many useless organs, and (2) the continuous 

 development of secondary sexual characters beyond any con- 

 ceivable utility, and, apparently, till checked by inutility. It 

 explains both these. Disuse alone, as I and many others 

 have always argued, cannot do the first, but can only cause 

 regress^ion to the mean, with perhaps some further regression 

 from economy of material. 



As to the second, I have always felt the difficulty of 

 accounting for the enormous development of the peacock's 

 train, the bird of paradise plumes, the long wattle of the 

 bell bird, the enormous tail-feathers of the Guatemalan 

 trogon, of some humming-birds, etc. etc. etc. The begin- 

 nings of all these I can explain a« recognition marks, and 

 this explains also their distinctive character in allied species, 

 but it does not explain their growing on and on far beyond 

 what is needful for recognition, and apparently till limited 

 by absolute hurtfulness. It is a relief to me to have " ger- 

 minal selection " to explain this. 



I do not, however, think it at all necessary to explain 

 adaptations, however complex. Variation is so general and 

 so large, in dominant species, and selection is so tremend- 

 ously powerful, that I believe all needful adaptation may be 

 produced without it. But, if it exists, it would undoubtedly 

 hasten the process of such adaptation and would therefore 

 enable new places in the economy of nature to be more 

 rapidly filled up. 



I was thinking of writing a popular exposition of the new 

 theory for Nature, but have not yet found time or inclina- 

 tion for it. I began reading " Germinal Selection " with a 

 prejudice against it. That prejudice continued through the 

 first half, but when I came to the idea itself, and after some 



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