Relates plan for an appendix to his Journal of researches which will include facts of species of birds' being different in different islands of the Galápagos and also of the lizards and tortoises on the islands. Asks JSH whether he can supply parallels in the plant life.
Saturday, 3 Nov
My dear Henslow
I am preparing an appendix to my Journal, in which I mean to add a few remarks on some of the subjects, which I have there discussed.— You may recollect how often I have talked over the marvellous fact of the species of birds being different, in those different islands of the Galapagos.— Lately I have gained some curious facts, bearing on the same points, regarding the lizards & tortoises of those same islands; & now I want to know whether you can tell me anything about the plants.— Pray understand, I do not want you to take any trouble in giving me names &c &c.— all I want is to know whether in casting your eye over my plants, how many cases (for you told me of some one or two) there are of near species, of the same genus,;—one species coming from one island, & the other from a second island.—
If there are any number of these cases you can mention to what natural families they belong. (or the genera if you happen to know them).— Also how near the species are;—whether they require comparison to be distinguished; or whether, merely in any natural classification, they would follow one after another. I have already given you trouble enough about this same Galap: Arch: but all I now want is for you to answer me, as far as your present knowledge goes; & in doing this, I apprehend it will not take up more than a hour, & it will (if such be the fact with the plants) support my case of the birds & Tortoises in a glorious manner.—
Many thanks for your letter, which I received some time.— Leonard Jenyns will see about the Savings Bank.—
Will you have the kindness to write pretty soon, as I believe (but am not sure) I shall go to press with the appendix immediately,—
Ever yours most truly | Chas. Darwin
I have written to you on a torn piece of Paper without perceiv<ing> it.
- f1 429a.f1A summary of this letter, taken from a sale catalogue, was printed in Correspondence vol. 7, Supplement. It was dated [before 27 October 1838]. Since then a facsimile of the original has been acquired by CUL; the text is reprinted here, with a corrected date.
- f2 429a.f2CD's supplementary remarks appear as the Addenda to the first edition of Journal of researches, pp. 609--29. They cover a range of topics, but principally geology.
- f3 429a.f3In an earlier letter to Henslow, CD mentioned the birds of the Galápagos, suspecting them to be `very curious' (see Correspondence vol. 1, letter to J. S. Henslow, [28--9] January 1836 and n. 2). Observations by CD on the diversity of mocking-birds and finches and their differences on the different islands appeared in Journal of researches, pp. 461--2 and 475. A fuller account of Galápagos birds, including illustrations of finches, was given in Journal of researches 2d ed., pp. 378--81, 394--5. For comment on the status of Galápagos finches in CD's exposition of his species theory, see Correspondence vol. 12, letter from [C. P.], 29 April 1864 and n. 3.
- f4 429a.f4In the Addenda to Journal of researches, p. 628, CD recognised that his own research had not been extensive enough to prove that each island had species of lizard and tortoise distinct from those of other islands. However, CD quoted Gabriel Bibron's identification of different species of tortoise from different islands, and of two species of the marine iguana, Amblyrhynchus, within the archipelago (ibid., p. 628).
- f5 429a.f5Henslow's reply has not been found, but an extract from it is quoted in Journal of researches, p. 629: `there are several instances of distinct species of the same genus, sent from one island only: that is, whilst the genus is common to two or three islands, the species are often different in the different islands. In some cases the species seem to run very close to each other, but are, I believe, distinct.' Henslow qualified his reply by saying that he had not yet examined the material in detail. The growing evidence of divergent populations of both animals and plants in the Galápagos caused CD to regret `not having procured a perfect series in every order of nature from the several islands' and to explain that he had not anticipated while on the Beagle `that islands in sight of each other should be characterized by peculiar faunas' (ibid., p. 629).
- f6 429a.f6Henslow arranged the collection of CD's Galápagos plants, now in the herbarium of the Department of Plant Sciences, Cambridge University, and described a small part of it (see J. S. Henslow 1837, 1838). CD continued for several years to encourage Henslow to describe the plants (see Correspondence vol. 2, letters to J. S. Henslow, [November 1839] and [22 January 1843]). Joseph Dalton Hooker eventually identified them (see Correspondence vols. 3 and 4), and observations arising from those identifications were added to Journal of researches 2d ed., pp. 392--3, 395--8. For CD's notes on his collection of plants during the Beagle voyage, see D. M. Porter 1987.
- f7 429a.f7The letter from Henslow has not been found.
- f8 429a.f8Leonard Jenyns was Henslow's brother-in-law and responsible for the descriptions of fish in Zoology.