72 MAN [CHAP. VIII 



Letter 439 his dog ! and will inquire about it. By the way, Mr. Trimen 

 tells me that as a boy he used to paint butterflies, and that 

 they long haunted the same place, but he made no further 

 observations on them. As far as colour is concerned, I see I 

 shall have to trust to mere inference from the males displaying 

 their plumage, and other analogous facts. I shall get no 

 direct evidence of the preference of the hens. Mr. Hewitt, 

 of Birmingham, tells me that the common hen prefers a 

 salacious cock, but is quite indifferent to colour. 



Will you consider and kindly give me your opinion on 

 the two following points. Do very vigorous and well- 

 nourished hens receive the male earlier in the spring than 

 weaker or poorer hens ? I suppose that they do. Secondly, 

 do you suppose that the birds which pair first in the season 

 have any advantage in rearing numerous and healthy off- 

 spring over those which pair later in the season ? With 

 respect to the mysterious cases of which you have given me 

 so many, in addition to those previously collected, of when 

 one bird of a pair is shot another immediately supplying its 

 place, I was drawing to the conclusion that there must be in 

 each district several unpaired birds ; yet this seems very 

 improbable. You allude, also, to the unknown causes which 

 keep down the numbers of birds ; and often and often have I 

 marvelled over this subject with respect to many animals. 



Letter 440 To A. R. Wallace. 



The following refers to Mr. Wallace's article U A Theory of Birds' 

 Nests," in Andrew Murray's Journal of Travel, Vol. I., p. 73. He here 

 treats in fuller detail the view already published in the Westminster 

 Review, July, 1867, p. 38. The rule which Mr. Wallace believes, with 

 very few exceptions, to hold good is, "that when both sexes are 

 of strikingly gay and conspicuous colours, the nest is ... such as to 

 conceal the sitting bird ; while, whenever there is a striking contrast of 

 colours, the male being gay and conspicuous, the female dull and obscure, 

 the nest is open, and the sitting bird exposed to view." At this time 

 Mr. Wallace allowed considerably more influence to sexual selection (in 

 combination with the need of protection) than in his later writings. 

 The following extract from a letter from Mr. Wallace to Darwin (July 23rd, 

 1877) fixes the period at which the change in his views occurred : " I am 

 almost afraid to tell you that in going over the subject of the colours of 

 animals, etc., etc., for a small volume of essays, etc., I am preparing, I have 

 come to conclusions directly opposed to voluntary sexual selection, and 



