My dear Sir,—­I am much obliged for your letter of Oct. 10th from Celebes, received a few days ago:  in a laborious undertaking, sympathy is a valuable and real encouragement.  By your letter, and even still more by your paper in the Annals,[28] a year or more ago, I can plainly see that we have thought much alike and to a certain extent have come to similar conclusions.  In regard to the paper in the Annals, I agree to the truth of almost every word of your paper; and I daresay that you will agree with me that it is very rare to find oneself agreeing pretty closely with any theoretical paper; for it is lamentable how each man draws his own different conclusions from the very same fact.  This summer will make the twentieth year (!) since I opened my first note-book on the question how and in what way do species and varieties differ from each other.  I am now preparing my work for publication, but I find the subject so very large, that though I have written many chapters, I do not suppose I shall go to press for two years.

I have never heard how long you intend staying in the Malay Archipelago; I wish I might profit by the publication of your Travels there before my work appears, for no doubt you will reap a large harvest of facts.

I have acted already in accordance with your advice of keeping domestic varieties, and those appearing in a state of nature, distinct; but I have sometimes doubted of the wisdom of this, and therefore I am glad to be backed by your opinion.  I must confess, however, I rather doubt the truth of the now very prevalent doctrine of all our domestic animals having descended from several wild stocks; though I do not doubt that it is so in some cases.  I think there is rather better evidence on the sterility of hybrid animals than you seem to admit:  and in regard to plants, the collection of carefully recorded facts by Koelreuter and Gaertner (and Herbert) is enormous.  I most entirely agree with you on the little effect of “climatic conditions” which one sees referred to ad nauseam in all books:  I suppose some very little effect must be attributed to such influences, but I fully believe that they are very slight.  It is really impossible to explain my views in the compass of a letter as to causes and means of variation in a state of nature; but I have slowly adopted a distinct and tangible idea—­whether true or false others must judge; for the firmest conviction of the truth of a doctrine by its author seems, alas, not to be the slightest guarantee of truth.

I have been rather disappointed at my results in the poultry line; but if you should, after receiving this, stumble on any curious domestic breed, I should be very glad to have it; but I can plainly see that the result will not be at all worth the trouble which I have taken.  The case is different with the domestic pigeons; from its study I have learned much.  The Rajah has sent me some of his pigeons and fowls