More Letters Of Charles Darwin Volume 1 A Record Of His Work In
Chapter 203
The Lyells have been here, and were extremely pleasant, but I saw them only occasionally for ten minutes, and when they went I had an awful day [of illness]; but I am now slowly getting up to my former standard. I shall soon be confined to a living grave, and a fearful evil it is.
I suppose you have read Tyndall. (179/1. Probably Tyndall "On the Conformation of the Alps" ("Phil. Mag." 1864, page 255).) I have now come round again to Ramsay's view, (179/2. "Phil. Mag." 1864, page 293.) for the third or fourth time; but Lyell says when I read his discussion in the "Elements," I shall recant for the fifth time. (179/3. This refers to a discussion on the "Connection of the predominance of Lakes with Glacial Action" ("Elements," Edition VI., pages 168-74). Lyell adheres to the views expressed in the "Antiquity of Man" (1863) against Ramsay's theory of the origin of lake basins by ice action.) What a capital writer Tyndall is!
In your last note you ask what the Bardfield oxlip is. It is P. elatior of Jacq., which certainly looks, when growing, to common eyes different from the common oxlip. I will fight you to the death that as primrose and cowslip are different in appearance (not to mention odour, habitat and range), and as I can now show that, when they cross, the intermediate offspring are sterile like ordinary hybrids, they must be called as good species as a man and a gorilla.
I agree that if Scott's red cowslip grew wild or spread itself and did not vary [into] common cowslip (and we have absolutely no proof of primrose or cowslip varying into each other), and as it will not cross with the cowslip, it would be a perfectly good species. The power of remaining for a good long period constant I look at as the essence of a species, combined with an appreciable amount of difference; and no one can say there is not this amount of difference between primrose and oxlip.
(PLATE: HUGH FALCONER, 1844. From a photograph by Hill & Adamson.)