My dear Hooker

Many thanks for your Review, which I shall read with greatest interest.² I quite agree about Lyell’s letters to me, which though to me interesting have afforded me no new light.— Your letters, under the geological point of view have been more valuable to me. You cannot imagine how earnestly I wish I c^d. swallow continental extension, but I cannot; the more I think (& I cannot get the subject out of my head), the more difficult I find it. If there were only some half-dozen cases, I sh^d. not feel the least difficulty, but the generality of the fact of all islands (except 1 or 2) having a considerable part of their production, in common with one or more mainlands, utterly staggers me.— What a wonderful case of the Epacridæ! It is most vexatious, almost humiliating to me that I cannot follow & subscribe to the way in which you strikingly put your view of the case. I look at your facts (about Eucalypti &c) as damning against continental extension, & if you like, also damning against migration, or at least of enormous difficulty.— I see the grounds of our difference (in a letter I must put myself on an equality in arguing) lies in my opinion that scarcely anything is known of means of distribution. I quite agree with A. Decandolles (& I daresay your) opinion that it is poor work putting together the merely possible means of distribution;³ but I see no other way in which the subject can be attacked; for I think that A. Decandolles argument that no plants have been introduced into England except by man’s agency, of no weight.—⁴ I cannot but think that the theory of continental extension does do some little harm as stopping investigation of means of dispersal, which whether negative or positive seem to me of value: when negatived, then everyone, who believes in single centres, will have to admit continental extensions.—

I agree about much greater chance of extermination on isl^ds.—but the (I think) (I have got lists) invariability of rule that on all islands there are naturalised mammifers, in some cases of some hundred years duration, in some degree weakens your argument.— I do not understand your argument why Java & Borneo beasts did not migrate; I wish I did.— Nor yet entirely about about specific centres; but I have entered both points in my note Book to ask you, when we meet; for you have of late taken enormous trouble for me.— I see from your remarks that you do not understand my notions, (whether or no worth anything) about modifications,—I attribute very little to the direct action of climate &c.—

I suppose in regard to specific centres, we are at cross purposes; I sh^d. call that kitchen garden, in which the Red Cabbage was produced, or the Farm in which Bakewell made the Short-Horn Cattle,⁵ the specific centre of these species! and surely this is centralisation enough!—

I thank you most sincerely for all your assistance; & whether or no my Book may be wretched you have done your best to make it less wretched. Sometimes I am in very good spirits & sometimes very low about it. My own mind is decided on the question of origin of species but good Heavens how little that is worth.

I have not read Austen with attention. Tyndall’s pamphlet is capital & has made me finally give up a cherished opinion, but which was much shaken before:⁶ I cannot but think, that Tyndall underrate the effect of the actual movement of the particle, in planes parallel to the pressing surfaces which he shows does take place, as pressure without extension produces no effect.

I must now look at all the cases of foliated schists which I have described, as metamorphosed cleaved rocks with segregation & crystallization along the planes of cleavage, (as along the planes of division caused by movement in obsidian lava- streams); I formerly thought that,⁷ —but I wont bore you—

so my dear Hooker, farewell & may you & M^rs. Hooker have a delightful tour. Adios | C. Darwin

My M.S. will not be ready till your return.—