My dear Lyell

Your letter contained much news for me.—   It is indeed most important that the Cambrian or Barrandes primordial should be getting so much separated (in spite of Murchison) from Lower Silurian: I did not at all know this.¹

I fear it is not very likely that I shall be up on 16^th (I have written to J. Lubbock)² though I sh^d. much like to hear the paper & discussions, for, I am sure that you will both be sorry to hear that Etty is ill with remittent Fever.³ There is at present no cause for anxiety, though she is very ill, & the Fever is sure to run on for a fortnight or three weeks, and anxiety always knocks me up.—

I have sent for Canadian Naturalist;⁴ if I cannot procure a copy I will borrow yours.— I had letter from Henslow this morning who says that Sedgwick was on last Monday night to open a battery on me at Cambridge Phil. Soc^y. —⁵ Anyhow I am much honoured by being attacked there & at Royal Soc. of Edinburgh.—⁶ With respect to Aster, I remember long ago reading curious paper by Asa Gray & another on Aster, in which they give cases of two forms so very distinct that they must consider them specifically distinct, & yet perfectly united by intermediate varieties or links & they admit that in almost every other case that this suffices to upset two species as distinct.—⁷ But I do not think it worth while to contradict single cases. Nor is it worth while arguing against those who do not attend to what I state. A moment reflexion will show you that there must be (on our doctrine) large genera not varying—see p. 56 on this subject in 2^d Edit of Origin—   Though I do not there discuss case in detail—

It may be sheer bigotry for my own notions, but I prefer to the Atlantis my notion of plants & animals having migrated from old to new world or conversely when climate was much hotter by approximately the line of Behring’s Straits.⁸ It is most important as you say to see living forms of plants going back so far in time. I wonder whether we shall ever discover the flora of dry land of the Coal period & find it not so anomalous as the swamp or coal-making flora!

I am working away over the blessed Pigeon manuscript;⁹ but from one cause or another I get on very slowly,—chiefly from my abominable stomach.—

This morning I got letter from Acad. Nat. Sc. of Philadelphia, announcing that I am elected a Correspondent;¹⁰— I do not suppose that this is much of honour; but it shows that some naturalists there do not think me such a scientific profligate as many think me here.—

Ever | My dear Lyell | Yours gratefully | C. Darwin

What a grand fact about extinct Stags horn worked by man!—¹¹