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