The Wallace-Darwin Correspondence 



Hurstpier point. March 19, 1868. 



Dear Darwin,— I should very much value a large photo- 

 graph of you, and also a carte for my album, though it is 

 too bad to ask you for both, as you must have so many 

 applicants. 



I am sorry I shall not see you in town, but shall 

 look forward with pleasure to paying you a visit in the 

 summer. 



I am sorry about the Primulas, but I feel sure some such 

 equally good case will some day be discovered, for it seems 

 impossible to understand how all natural species whatever 

 should have acquired sterility. Closely allied forms from 

 adjacent islands would, I should think, offer the best 

 chance of finding good species fertile iriter se; since even 

 if Natural Selection induces sterility I do not see how it 

 could affect them, or w^hy they should always be sterile, 

 and varieties never. 



I am glad you have got good materials on sexual selec- 

 tion. It is no doubt a difficult subject. One difficulty to 

 me is, that I do not see how the constant minute varia- 

 tions, which are sufficient for Natural Selection to work 

 with, could be sexually selected. We seem to require a 

 series of bold and abrupt variations. How can we imagine 

 that an inch in the tail of a peacock, or a quarter of an 

 inch in that of the bird of paradise, would be noticed and 

 preferred by the female ? 



Pray let me see what your son says about the sterility 

 selection question. I am deeply interested in all that con- 

 cerns the powers of Natural Selection, but, though I admit 

 there are a few things it cannot do, I do not yet believe 

 sterility to be one of them. 



In case your son has turned his attention to mathematical 

 physics, will you ask him to look at the enclosed question, 



203 



