That on parrots[43] contained most new matter to me, and interested me extremely; that in the Geographical Journal[44] strikes me as an epitome of the whole theory of geographical distribution:  the comparison of Borneo and New Guinea, the relation of the volcanic outbursts and the required subsidence, and the comparison of the supposed conversion of the Atlantic into a great archipelago, seemed to me the three best hits.  They are both indeed excellent papers.—­Believe me yours very sincerely,

CHARLES DARWIN.

Do try what hard work will do to banish painful thoughts.[45]

P.S.—­During one of the later French voyages, a wild pig was killed and brought from the Aru Islands to Paris.  Am I not right in inferring that this must have been introduced and run wild?  If you have a clear opinion on this head, may I quote you?

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5 Westbourne Grove Terrace, W. January 31, [1865?].

Dear Darwin,—­Many thanks for your kind letter.  I send you now a few more papers.  One on Man is not much in your line.  The other three are bird lists, but in the introductory remarks are a few facts of distribution that may be of use to you, and as you have them already in the Zoological Proceedings, you can cut these up if you want “extracts.”

I hope you do not very much want the Aru pig to be a domestic animal run wild, because I have no doubt myself it was the species peculiar to the New Guinea fauna (Sus papuensis, Less.), a very distinct form.  I have no doubt it is this species, though I did not get it myself there, because I was told that on a small island near, called there Pulo babi (Pig Island), was a race of pigs (different from and larger than those of the large islands) which had originated from the wreck of a large ship near a century ago.  The productions of the Aru Islands closely resemble those of New Guinea, more than half the species of birds being identical, as well as about half of the few known mammals.

I am beginning to work at some semi-mechanical work, drawing up catalogues of parts of my collection for publication.

I enclose my “carte.”  Have you a photograph of yourself of any kind you can send me?  When you come to town next, may I beg the honour of a sitting for my brother-in-law, Mr. Sims, 73 Westbourne Grove?—­Yours very sincerely,

ALFRED R. WALLACE.

P.S.—­Your paper on Lythrum salicaria[46] is most beautiful.  What a wonderful plant it is!  I long to hear your paper on Tendrils and hear what you have got out of them.  My old friend Spruce, a good botanist and close observer, could probably supply you with some facts on that or other botanical subjects if you would write to him.  He is now at Kew, but almost as ill as yourself.—­A.R.W.

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Down, Bromley, Kent, S.E.  February 1, 1865.