summer will make the 20th 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 Kolreuter and Gaertner (and Herbert,) is ENORMOUS. I most entirely agree with you on the little effects of "climatal 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), on the 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!...
CHARLES DARWIN TO J.D. HOOKER. Moor Park, Saturday [May 2nd, 1857].
My dear Hooker,
You have shaved the hair off the Alpine plants pretty effectually. The case of the Anthyllis will make a "tie" with the believed case of Pyrenees plants