My dear Sir

I hardly know which of your 3 last letters has interested me most.—²

What splendid work I shall have hereafter in selecting & arranging all your facts. Your last letter is most curious all about the bird-catchers & interested us all.— I suppose that the male chaffinch in “pegging” approaches the captive singing-bird, from rivalry or jealousy— if I am wrong please tell me; otherwise I will assume so.—³

Can you form any theory about all the many cases which you have given me & others which have been published, of when one of pair is killed, another soon appearing? Your fact about the bullfinches in your garden is most curious on this head.⁴ Are there everywhere many unpaired birds? What can the explanation be?—

M^r. Gould assures me that all the nightingales which first come over are males, & he believes this is so with other migratory birds.—⁵ But this does not agree with what the bird-catchers say about the common Linnet, which I suppose migrates within the limits of England.—

In your penultimate letter you tell me about gay caterpillars, & the facts seem to me highly satisfactory, but you speak as if they were few.— Would it not save you labour if I were to forward this letter to Wallace, & ask him for its return?⁶

Many thanks for very curious case of Pavo nigripennis— I am very glad to get additional evidence; I have sent your fact to be inserted, if not too late, in four foreign editions which are now printing⁷

I am delighted to hear that you approve of my Book— I thought every mortal man w^d find the details very tedious & have often repented of giving so many.— You will find Pangenesis stiff reading & I fear will shake your head in disapproval: Wallace sticks up for the great god Pan like a man.—⁸

The fertility of hybrid-canaries w^d. be a fine subject for careful investigation.⁹

Yours most truly obliged | C. Darwin