My dear Sir, I am much obliged for your letter of October 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 ('On the law that has regulated the introduction of new species.'--Ann. Nat. Hist., 1855.) in the Annals, 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 dare say 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 facts. This 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 becoming glabrous at low levels. If I DO find that I have marked such facts, I will lay the evidence before you. I wonder how the belief could have originated! Was it through final causes to keep the plants warm? Falconer in talk coupled the two facts of woolly Alpine plants and mammals. How candidly and meekly you took my Jeremiad on your severity to second-class men. After I had sent it off, an ugly little voice asked me, once or twice, how much of my noble defence of the poor in spirit and in fact, was owing to your having not seldom smashed favourite notions of my own. I silenced the ugly little voice with contempt, but it would whisper again and again. I sometimes despise myself as a poor compiler as heartily as you could do, though I do NOT despise my whole work, as I think there is enough known to lay a foundation for the discussion on the origin of species. I have been led to despise and laugh at myself as a compiler, for having put down that "Alpine plants have large flowers," and now perhaps Imay write over these very words, "Alpine plants have small or apetalous flowers!"...
CHARLES DARWIN TO J.D. HOOKER.
Down, [May] 16th [1857].
My dear Hooker, You said--I hope honestly--that you did not dislike my asking questions on general points, you of course answering or not as time or inclination might serve. I find in the animal kingdom that the proposition that any part or organ developed normally (i.e., not a monstrosity) in a species in any HIGHor UNUSUAL degree, compared with the same part or organ in allied species, tends to be HIGHLY VARIABLE. I cannot doubt this from my mass of collected facts. To give an instance, the Cross-bill is very abnormal in the structure of its bill compared with other allied Fringillidae, and the beak is EMINENTLY VARIABLE. The Himantopus, remarkable from the wonderful length of its legs, is VERY variable in the length of its legs. I could give MANY most striking and curious illustrations in all classes; so many that I think it cannot be chance. But I have NONE in the vegetable kingdom, owing, as I believe, to my ignorance. If Nepenthes consisted of ONE or two species in a group with a pitcher developed, then I should have expected it to have been very variable; but I do not consider Nepenthes a case in point, for when a whole genus or group has an organ, however anomalous, I do not expect it to be variable,--it is only when one or few species differ greatly in some one part or organ from the forms CLOSELYALLIED to it in all other respects, that I believe such part or organ to be highly variable. Will you turn this in your mind? It is an important apparent LAW (!) for me.
Ever yours, C. DARWIN.