Sitaris and Meloe (158/2. Sitaris and Meloe, two genera of coleopterous insects, are referred to by Lubbock (op. cit., pages 63-64) as "perhaps...the most remarkable cases...among the Coleoptera" of curious and complicated metamorphoses.) seem very good. You have put the whole case of metamorphosis in a new light; I dare say what you remark about poverty of fresh-water is very true. (158/3. "We cannot but be struck by the poverty of the fresh-water fauna when compared with that of the ocean" (op. cit., page 64).) I think you might write a memoir on fresh-water productions. I suggest that the key-note is that land-productions are higher and have advantage in general over marine; and consequently land-productions have generally been modified into fresh-water productions, instead of marine productions being directly changed into fresh-water productions, as at first seems more probable, as the chance of immigration is always open from sea to rivers and ponds.
My talk with you did me a deal of good, and I enjoyed it much.
LETTER 159. TO J.D. HOOKER. Down, January 13th [1863].
I send a very imperfect answer to [your] question, which I have written on foreign paper to save you copying, and you can send when you write to Thomson in Calcutta. Hereafter I shall be able to answer better your question about qualities induced in individuals being inherited; gout in man--loss of wool in sheep (which begins in the first generation and takes two or three to complete); probably obesity (for it is rare with poor); probably obesity and early maturity in short-horn cattle, etc., etc.
LETTER 160. TO A. DE CANDOLLE. Down, January 14th [1863].
I thank you most sincerely for sending me your Memoir. (160/1. Etude sur l'Espece a l'occasion d'une revision de la Famille des Cupuliferes. "Biblioth. Univ. (Arch. des Sc. Phys. et Nat.)," Novembre 1862.) I have read it with the liveliest interest, as is natural for me; but you have the art of making subjects, which might be dry, run easily. I have been fairly astonished at the amount of individual variability in the oaks. I never saw before the subject in any department of nature worked out so carefully. What labour it must have cost you! You spoke in one letter of advancing years; but I am very sure that no one would have suspected that you felt this. I have been interested with every part; though I am so unfortunate as to differ from most of my contemporaries in thinking that the vast continental extensions (160/2. See Letters 47, 48.) of Forbes, Heer, and others are not only advanced without sufficient evidence, but are opposed to much weighty evidence. You refer to my work in the kindest and most generous spirit. I am fully satisfied at the length in belief to which you go, and not at all surprised at the prudent reservations which you make. I remember well how many years it cost me to go round from old beliefs. It is encouraging to me to observe that everyone who has gone an inch with me, after a period goes a few more inches or even feet. But the great point, as it seems to me, is to give up the immutability of specific forms; as long as they are thought immutable, there can be no real progress in "Epiontology." (160/3. See De Candolle, loc. cit., page 67: he defines "Epiontologie" as the study of the distribution and succession of organised beings from their origin up to the present time. At present Epiontology is divided into geography and palaeontology, "mais cette division trop inegale et a limites bien vagues disparaitra probablement.") It matters very little to any one except myself, whether I am a little more or less wrong on this or that point; in fact, I am sure to be proved wrong in many points. But the subject will have, I am convinced, a grand future. Considering that birds are the most isolated group in the animal kingdom, what a splendid case is this Solenhofen bird-creature with its long tail and fingers to its wings! I have lately been daily and hourly using and quoting your "Geographical Botany" in my book on "Variation under Domestication."
LETTER 161.