Page 153 Pages 131-32 On splitting up of old geographical provinces.
Long before Owen published I had in MS. worked out the succession of types in the Old World (as I remember telling Sedgwick, who of course disbelieved it).
Since receiving your last letter on Hooker, I have read his introduction as far as page xxiv (87/4. "On the Flora of Australia, etc.; being an Introductory Essay to the Flora of Tasmania": London, 1859.), where the Australian flora begins, and this latter part I liked most in the proofs. It is a magnificent essay. I doubt slightly about some assertions, or rather should have liked more facts--as, for instance, in regard to species varying most on the confines of their range. Naturally I doubt a little his remarks about divergence (87/5. "Variation is effected by graduated changes; and the tendency of varieties, both in nature and under cultivation, when further varying, is rather to depart more and more widely from the original type than to revert to it." On the margin Darwin wrote: "Without selection doubtful" (loc. cit., page viii).), and about domestic races being produced under nature without selection. It would take much to persuade me that a Pouter Pigeon, or a Carrier, etc., could have been produced by the mere laws of variation without long continued selection, though each little enlargement of crop and beak are due to variation. I demur greatly to his comparison of the products of sinking and rising islands (87/6. "I venture to anticipate that a study of the vegetation of the islands with reference to the peculiarities of the generic types on the one hand, and of the geological conditions (whether as rising or sinking) on the other, may, in the present state of our knowledge, advance other subjects of distribution and variation considerably" (loc. cit., page xv).); in the Indian Ocean he compares exclusively many rising volcanic and sinking coral islands. The latter have a most peculiar soil, and are excessively small in area, and are tenanted by very few species; moreover, such low coral islands have probably been often, during their subsidence, utterly submerged, and restocked by plants from other islands. In the Pacific Ocean the floras of all the best cases are unknown. The comparison ought to have been exclusively between rising and fringed volcanic islands, and sinking and encircled volcanic islands. I have read Naudin (87/7. Naudin, "Revue Horticole," 1852?.), and Hooker agrees that he does not even touch on my views.
LETTER 88. J.D. HOOKER TO CHARLES DARWIN. [1859 or 1860.]
I have had another talk with Bentham, who is greatly agitated by your book: evidently the stern, keen intellect is aroused, and he finds that it is too late to halt between two opinions. How it will go we shall see. I am intensely interested in what we shall come to, and never broach the subject to him. I finished the geological evidence chapters yesterday; they are very fine and very striking, but I cannot see they are such forcible objections as you still hold them to be. I would say that you still in your secret soul underrate the imperfection of the Geological Record, though no language can be stronger or arguments fairer and sounder against it. Of course I am influenced by Botany, and the conviction that we have not in a fossilised condition a fraction of the plants that have existed, and that not a fraction of those we have are recognisable specifically. I never saw so clearly put the fact that it is not intermediates between existing species we want, but between these and the unknown tertium quid.
You certainly make a hobby of Natural Selection, and probably ride it too hard; that is a necessity of your case. If the improvement of the creation-by-variation doctrine is conceivable, it will be by unburthening your theory of Natural Selection, which at first sight seems overstrained-- i.e., to account for too much. I think, too, that some of your difficulties which you override by Natural Selection may give way before other explanations.