My dear Lyell

It was extremely kind of you to take so much trouble to tell me about Haldeman’s paper, which I read several years ago & abstracted, & I have just looked at my abstract.² I well remember thinking it a very clever paper; but I did not find much of any actual use to me. I think I have quoted him in my large Book about ranges of varieties; but in my present condensed volume, I have not alluded to the paper. The speculations approach mine & Wallace’s, but did not on any point seem to me identical. Some remarks on the young of some fresh-water shell struck me most, apparently a modified sea-mollusc.—³

You ask about specific centres, if you change terms into specific areas, my theory quite requires them; i.e. it is, I think, next door to an impossibility that the same species should have been formed identically the same in any two areas. This point is discussed in my volume.—⁴

I am working very hard, but get on slowly for I find that my corrections are terrifically heavy, & the work most difficult to me. I have corrected 130 pages; & the vol: will be about 500. I have tried my best to make it clear & striking; but very much fear that I have failed, so many discussions are, & must be, very perplexing.— I have done my best. If you had all my materials, I am sure you would have made a splendid Book. I long to finish, for I am nearly worn out.

My dear Lyell | Ever yours most truly | C. Darwin