generation; nor does he attach, I think, sufficient weight to the cases of what I have called unconscious selection by man: in these cases races are modified by the preservation of the best and the destruction of the worst, without any isolation. I sympathise with you most sincerely on the state of your eyesight: it is indeed the most fearful evil which can happen to any one who, like yourself, is earnestly attached to the pursuit of natural knowledge. LETTER 227. TO F. MULLER. Down, March 18th [1869]. Since I wrote a few days ago and sent off three copies of your book, I have read the English translation (227/1. "Facts and Arguments for Darwin." See "Life and Letters," III., page 37.), and cannot deny myself the pleasure of once again expressing to you my warm admiration. I might, but will not, repeat my thanks for the very honourable manner in which you often mention my name; but I can truly say that I look at the publication of your essay as one of the greatest honours ever conferred on me. Nothing can be more profound and striking than your observations on development and classification. I am very glad that you have added your justification in regard to the metamorphoses of insects; for your conclusion now seems in the highest degree probable. (227/2. See "Facts and Arguments for Darwin," page 119 (note), where F. Muller gives his reasons for the belief that the "complete metamorphosis" of insects was not a character of the form from which insects have sprung: his argument largely depends on considerations drawn from the study of the neuroptera.) I have re-read many parts, especially that on cirripedes, with the liveliest interest. I had almost forgotten your discussion on the retrograde development of the Rhizocephala. What an admirable illustration it affords of my whole doctrine! A man must indeed be a bigot in favour of separate acts of creation if he is not staggered after reading your essay; but I fear that it is too deep for English readers, except for a select few. LETTER 228. TO A.R. WALLACE. March 27th [1869]. I have lately (i.e., in new edition of the "Origin") (228/1. Fifth edition, 1869, pages 150-57.) been moderating my zeal, and attributing much more to mere useless variability. I did think I would send you the sheet, but I daresay you would not care to see it, in which I discuss Nageli's Essay on Natural Selection not affecting characters of no functional importance, and which yet are of high classificatory importance. Hooker is pretty well satisfied with what I have said on this head. LETTER 229. TO J.D. HOOKER. Caerdeon, Barmouth, North Wales, July 24th [1869].