To John Jenner Weir   27 February [1868]

My dear Sir

I must thank you for y^r paper on Apterous Lepidopt: which has interested me exceedingly, & likewise for the very honourable mention which you make of my name.¹ It is almost a pity that y^r paper was not published in some journal in which it w^d have had a wider distribution. It contained much that was new to me. I think the part about the relation of the wings & spiracles & trachæ might have been made a little clearer.² Incidentally you have done me a good service by reminding me of the rudimentary spurs on the legs of the partridge;³ for I am now writing on what I have called sexual selection. I believe that I am not mistaken in thinking that you have attended much to birds in confinement, as well as to insects. If you c^d call to mind any facts bearing on this subject with Birds, insects or any animals—such as the selection by a female of any particular male—or conversely of a particular female by a male—or on the rivalry between males—or on the allurement of the females by the males—or any such facts, I sh^d be most grate⁠⟨⁠ful⁠⟩⁠ for the information if you w^d have the kindness to communicate it.

Pray believe me— | my dear Sir | yours very faithfully | Ch. Darwin

P.S. I may give an instance of class of facts, that Barrow asserts, that a male Emberiza(?) at the Cape has immensely long tail-feathers during breeding season; & that if these are cut off, he has no chance of getting a wife.⁴ I have always felt an intense wish to make analogous trials, but have never had an opportunity, & it is not likely that you or anyone would be willing to try so troublesome an experiment. Colouring or staining the fine red breast of a bull-finch, with some innocuous matter into a dingy tint w^d be an analogous case, & then putting him & ordinary males with a female.

A friend promised, but failed, to try a converse experiment with white pigeons, viz to stain their tails & wings with magenta or other colours & then observe what effect such a prodigious alteration would have on their courtship.⁵ It w^d be a fine trial to cut off the eyes of the tail-feathers of male-peacocks, but who w^d sacrifice the beauty of their bird for which reason to please a mere naturalist!

C. D