62 MAN [Chap. VIII 



Letter 430 and long afterwards be transferred to the female. Thirdly, 

 characters may arise in either sex and be transmitted to both 

 sexes, either in an equal or unequal degree. In this latter 

 case I have supposed that the survival of the fittest has come 

 into play with female birds and kept the female dull-coloured. 

 With respect to the absence of spurs in the female gallinaceous 

 birds, I presume that they would be in the way during incu- 

 bation ; at least I have got the case of a German breed of 

 fowls in which the hens were spurred, and were found to 

 disturb and break their eggs much. With respect to the 

 females of deer not having horns, I presume it is to save the 

 loss of organised matter. In your note you speak of sexual 

 selection and protection as sufficient to account for the 

 colouring of all animals, but it seems to me doubtful how far 

 this will come into play with some of the lower animals, such 

 as sea anemones, some corals, etc., etc. On the other hand 

 Hackel x has recently well shown that the transparency and 

 absence of colour in the lower oceanic animals, belonging to 

 the most different classes, may be well accounted for on the 

 principle of protection. 



Some time or other I should like much to know where 

 your paper on the nests of birds has appeared, and I shall be 

 extremely anxious to read your paper in the Westminster 

 Review? Your paper on the sexual colouring of birds will, I 

 have no doubt, be very striking. Forgive me, if you can, for 

 a touch of illiberality about your paper. 



Letter 431 



To A. R. Wallace. 



March 19th, 1868. 



The Variation of Animals and Plants having been published on 

 Jan. 30th, 1868, Mr. Darwin notes in his diary that on Feb. 4th he 

 "Began on Man and Sexual Selection." He had already (in 1864 and 

 1867) corresponded with Mr Wallace on these questions — see for 

 instance the Life and Letters, III., p. 89; but, owing to various interrup- 

 tions, serious work on the subject did not begin until 1869. The following 

 quotations show the line of work undertaken early in 1868. 



Mr. Wallace wrote (March 19th, 1868) : " I am glad you have got 

 good materials on sexual selection. It is no doubt a difficult subject. 

 One difficulty to me is, that I do not see how the constant minute 

 variations, which are sufficient for Natural Selection to work with, 



1 See Descent of Man (1901) p. 402. 

 3 Westminster Review, July, 1867. 



