The Wallace-Darwin Correspondence 



male bird become more and more brilliant by sexual selec- 

 tion, and a good deal of that colour is transmitted to the 

 female till it becomes positively injurious to her during 

 incubation and the race is in danger of extinction, do you 

 not think that all the females who had acquired less of 

 the male's bright colours or who themselves varied in a 

 protective direction would be preserved, and that thus a 

 good protective colouring would be acquired ? If you 

 admit that this could occur, and can show no good reason 

 why it should not often occur, then we no longer differ, 

 for this is the main point of my view. 



Have you ever thought of the red wax-tips of the Bomby- 

 cilla beautifully imitating the red fructification of lichens 

 used in the nest, and therefore the females have it too ? Yet 

 this is a very sexual-looking character. 



We begin printing this week. — Yours very faithfully, 



Alfred R. Wallace. 



P. S.— Pray don't distress yourself on this subject. It 

 will all come right in the end, and after all it is only an 

 episode in your great work. — A. R. W. 



9 St, Mark's Crescent, N.W. October 4, 1868. 



Dear Darwin, — I should have answered your letter 

 before, but have been very busy reading over my MSS. 

 the last time before going to press, drawing maps, 

 etc. etc. 



Your first question cannot be answered, because we have 

 not, in individual cases of slight sexual difference, sufficient 

 evidence to determine how much of that difference is due to 

 sexual selection acting on the male, how much to natural 

 selection (protective) acting on the female, or how much 

 of the difference may be due to inherited differences from 

 ancestors who lived under different conditions. On your 

 second question I can give an opinion. I do think the 



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