We remain here till April 1st, and then hurrah for home and quiet work. LETTER 438. TO J. JENNER WEIR. 4, Chester Place, N.W., March 27th [1868]. I hardly know which of your three last letters has interested me most. What splendid work I shall have hereafter in selecting and arranging all your facts. Your last letter is most curious--all about the bird-catchers--and interested us all. I suppose 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. Can you form any theory about all the many cases which you have given me, and others which have been published, of when one [of a] pair is killed, another soon appearing? Your fact about the bullfinches in your garden is most curious on this head. (438/1. Mr. Weir stated that at Blackheath he never saw or heard a wild bullfinch, yet when one of his caged males died, a wild one in the course of a few days generally came and perched near the widowed female, whose call-note is not loud. "Descent of Man" (1901), page 623.) Are there everywhere many unpaired birds? What can the explanation be? Mr. Gould assures me that all the nightingales which first come over are males, and he believes this is so with other migratory birds. But this does not agree with what the bird-catchers say about the common linnet, which I suppose migrates within the limits of England. Many thanks for very curious case of Pavo nigripennis. (438/2. See "Animals and Plants," Edition II., Volume I., page 306.) 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 printing. I am delighted to hear that you approve of my book; I thought every mortal man would find the details very tedious, and have often repented of giving so many. You will find pangenesis stiff reading, and I fear will shake your head in disapproval. Wallace sticks up for the great god Pan like a man. The fertility of hybrid canaries would be a fine subject for careful investigation. LETTER 439. TO J. JENNER WEIR. Down, April 4th [1868].