Thanks also for your own (136/1. See note in Letter 135.) and Bates' letter now returned. They are both excellent; you have, I think, said all that can be said against direct effects of conditions, and capitally put. But I still stick to my own and Bates' side. Nevertheless I am pleased to attribute little to conditions, and I wish I had done what you suggest--started on the fundamental principle of variation being an innate principle, and afterwards made a few remarks showing that hereafter, perhaps, this principle would be explicable. Whenever my book on poultry, pigeons, ducks, and rabbits is published, with all the measurements and weighings of bones, I think you will see that "use and disuse" at least have some effect. I do not believe in perfect reversion. I rather demur to your doctrine of "centrifugal variation." (136/2. The "doctrine of centrifugal variation" is given in Sir J.D. Hooker's "Introductory Essay to the Flora of Tasmania" (Part III. of the Botany of the Antarctic Expedition), 1859, page viii. In paragraph 10 the author writes: "The tendency of varieties, both in nature and under cultivation...is rather to depart more and more widely from the original type than to revert to it." In Sir Joseph's letter to Bates (loc. cit., page lii) he wrote: "Darwin also believes in some reversion to type which is opposed to my view of variation." It may be noted in this connection that Mr. Galton has shown reason to believe in a centripetal tendency in variation (to use Hooker's phraseology) which is not identical with the reversion of cultivated plants to their ancestors, the case to which Hooker apparently refers. See "Natural Inheritance," by F. Galton, 1889.) I suppose you do not agree with or do not remember my doctrine of the good of diversification (136/3. Darwin usually used the word "divergence" in this connection.); this seems to me amply to account for variation being centrifugal--if you forget it, look at this discussion (page 117 of 3rd edition), it was the best point which, according to my notions, I made out, and it has always pleased me. It is really curiously satisfactory to me to see so able a man as Bates (and yourself) believing more fully in Natural Selection than I think I even do myself. (136/4. This refers to a very interesting passage in Hooker's letter to Bates (loc. cit., page liii): "I am sure that with you, as with me, the more you think the less occasion you will see for anything but time and natural selection to effect change; and that this view is the simplest and clearest in the present state of science is one advantage, at any rate. Indeed, I think that it is, in the present state of the inquiry, the legitimate position to take up; it is time enough to bother our heads with the secondary cause when there is some evidence of it or some demand for it--at present I do not see one or the other, and so feel inclined to renounce any other for the present.") By the way, I