My dear Mr. Poulton,--Many thanks for sending me Weismann's additional Essays,[20] which I look forward to reading with much pleasure. I have, however, read the first, and am much disappointed with it. It seems to me the _weakest and most inconclusive_ thing he has yet written. At p. 17 he states his theory as to degeneration of eyes, and again, on p. 18, of anthers and filaments; but in both cases he fails to _prove_ it, and apparently does not see that his panmixia, or "cessation of selection," cannot possibly produce _continuous_ degeneration culminating in the total or almost total disappearance of an organ. Romanes and others have pointed out this weakness in his theory, but he does not notice it, and goes on calmly throughout the essay to _assume_ that mere panmixia must cause progressive degeneration to an unlimited extent; whereas all it can do is to effect a reduction to the average of the total population on which selection has been previously worked. He says "individuals with weak eyes would not be eliminated," but omits to notice that individuals with strong eyes would also "not be eliminated," and as there is no reason alleged why variations in _all directions_ should not occur as before, the free intercrossing would tend to keep up a mean condition only a little below that which was kept up by selection. It is clear that some form of selection must always co-operate in degeneration, such as economy of growth, which he hardly notices except as a possible but not a necessary factor, or actual injuriousness. It appears to me that what is wanted is to take a number of typical cases, and in each of them show how Natural Selection comes in to carry on the degeneration begun by panmixia. Weismann's treatment of the subject is merely begging the question.--Yours faithfully, A.R. WALLACE. * * * * * TO PROF. POULTON _Parkstone, Dorset. August 29, 1892._