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Darwin Correspondence Project

From A. R. Wallace   8 [April] 18681


March 8th. | 1868

Dear Darwin

I am sorry you should have given yourself the trouble to answer my ideas on Sterility—2 If you are not convinced, I have little doubt but that I am wrong; and in fact I was only half-convinced by my own arguments,—and I now think there is about an even chance that Nat. Select. may or not be able to accumulate sterility. If my 1st prop. is modified to,—the existence of a species and a variety in the same area, it will do just as well for my argument.3 Such certainly do exist. They are fertile together, and yet each maintains itself tolerably distinct. How can this be, if there is no disinclination to crossing?

My belief certainly is that number of offspring is not so important an element in keeping up population of a species, as supply of food and other favourable conditions,—because the numbers of a species constantly vary greatly in different parts of its area, whereas the average number of offspring is not a very variable element.

However I will say no more but leave the problem as insoluble, only fearing that it will become a formidable weapon in the hands of the enemies of Nat. Selection.

While writing a few pages on the northern Alpine forms of plants on the Java mountains I wanted a few cases to refer to like Teneriffe, where there are no northern forms and scarcely any alpine. I expected the volcanoes of Hawaii would be a good case, and asked Dr. Seemann4 about them. It seems a man has lately published a list of Hawaaian plants and the mountains swarm with European alpine genera & some species!.5 Is not this most extraordinary and a puzzler. They are I believe truly Oceanic islands in the absence of mammals and the extreme poverty of Birds & Insects and they are within the tropics.

Will not that be a hard nut for you when you come to treat in detail on Geog. distribution.

I enclose Seemann’s note, which please return when you have copied the list if of any use to you.6

Many thanks for your carte which I think very good. The large one had not arrived when I was in town last week.7

Sir C. Lyell’s Chap. on Oceanic Is. I think very good.8

Believe me Dear Darwin | Yours very faithfully | Alfred R. Wallace—


Wallace evidently wrote ‘March’ accidentally. The month is established by the relationship between this letter and the letter to A. R. Wallace, 6 April [1868].
See letter to A. R. Wallace, 6 April [1868]. For Wallace’s argument that hybrid sterility could result from natural selection, see the letter from A. R. Wallace, 1 March 1868 and enclosure. For George Howard Darwin’s rebuttal of some points of the argument, and Wallace’s rejoinder, see the enclosure to the letter to A. R. Wallace, [21 March 1868], and the letter from A. R. Wallace, 24 March [1868].
Wallace refers to the first proposition of his argument on the selection of sterility (see enclosure to letter from A. R. Wallace, 1 March 1868).
Berthold Carl Seemann.
Wallace refers to the article ‘Enumeration of Hawaiian plants’, by Horace Mann (Mann 1866). The article was reprinted as a book (Mann 1867), a notice of which appeared in Journal of Botany 5 (1867): 314 (the journal was edited by Seemann). Wallace later remarked that the plant list was ‘inaccurate, or greatly exaggerated’ (see ML 2: 9).
The enclosure has not been found.
CD had arranged for a large photograph of himself to be sent directly to Wallace by the photographer Ernest Edwards, and personally sent a carte de visite (see letter to A. R. Wallace, [21 March 1868]).
Wallace refers to Lyell 1867–8, 2: 402–32. For earlier remarks by CD and Wallace on the book, see the letter to A. R. Wallace, [21 March 1868], and the letter from A. R. Wallace, 24 March [1868].


Lyell, Charles. 1867–8. Principles of geology or the modern changes of the earth and its inhabitants considered as illustrative of geology. 10th edition. 2 vols. London: John Murray.

Mann, Horace. 1866. Enumeration of Hawaiian plants. Proceedings of the American Academy of Arts and Sciences 7 (1865–8): 143–235.

Mann, Horace. 1867. Enumeration of Hawaiian plants. Cambridge, Mass.: Welch, Bigelow, and Company.

ML: More letters of Charles Darwin: a record of his work in a series of hitherto unpublished letters. Edited by Francis Darwin and Albert Charles Seward. 2 vols. London: John Murray. 1903.


If CD is not convinced by his notes on sterility, ARW has little doubt that he is wrong. In fact he was only half-convinced by his own arguments.

Modifies his first proposition [a species varies occasionally in two directions, but owing to free inter-crossing the variations never increase] and further discusses the subject.

Encloses Berthold Seemann’s notes on flora of the Hawaiian Islands. Presence of European alpine species in Hawaiian volcanoes is a "hard nut" for geographical distribution [but see ARW’s Island life (1880), p. 323].

Letter details

Letter no.
Alfred Russel Wallace
Charles Robert Darwin
Sent from
Source of text
DAR 106: B57-8
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 6104,” accessed on 27 October 2021,

Also published in The Correspondence of Charles Darwin, vol. 16