(216/2.

Sir Joseph Hooker's Presidential Address at the British Association Meeting.) Shall we have the pleasure of seeing you there?
I am engaged in negociations about my book.
Hoping you are well and getting on with your next volumes.
(216/3.

We are permitted by Mr.Wallace to append the following note as to his more recent views on the question of Natural Selection and sterility:-- "When writing my "Darwinism," and coming again to the consideration of this problem of the effect of Natural Selection in accumulating variations in the amount of sterility between varieties or incipient species twenty years later, I became more convinced, than I was when discussing with Darwin, of the substantial accuracy of my argument.
Recently a correspondent who is both a naturalist and a mathematician has pointed out to me a slight error in my calculation at page 183 (which does not, however, materially affect the result), disproving the 'physiological selection' of the late Dr.Romanes, but he can see no fallacy in my argument as to the power of Natural Selection to increase sterility between incipient species, nor, so far as I am aware, has any one shown such fallacy to exist.
"On the other points on which I differed from Mr.Darwin in the foregoing discussion--the effect of high fertility on population of a species, etc .-- I still hold the views I then expressed, but it would be out of place to attempt to justify them here." A.R.W.

(1899).) LETTER 217.

TO C.LYELL.Down, October 4th [1867].
With respect to the points in your note, I may sometimes have expressed myself with ambiguity.