WCP1893

Letter (WCP1893.1783)

[1]

4 Chester Pl[ace] R[egent's]. Par[k] N.<W>

Saturday [21 March 1868]1

My dear Wallace

I have sent your query to Cambridge to my son2. He ought to answer it, for he got his place of 2d wrangler,3 chiefly by solving very difficult problems.— I enclose his remarks on two of your Paragraphs: I sh[oul]d. like them returned some time for I have not studied them, & l[et] me hear your impression.— 4

I have told E[rnest]. Edwards5 to send <one> of my large Photographs to you addressed to 76½ Westbourne Grove "not to be forwarded".— When at home I will send my carte.—

[2] The sterility is a most a<wkward> problem. I can see so far <but I> [MS damaged] am hardly willing to admit all your assumptions & even if they were all admitted, the process is so complex, & the sterility (as you remark in your note) so universal, even with species inhabiting quite distinct countries (as I remark in my Chapter),6 together with the frequency of a difference in reciprocal unions, that I cannot persuade myself that it has been gained by natural selection, any more than the difficulty of grafting distinct genera, & the impossibility of grafting distinct Families.

You will allow, I suppose, that the capacity of grafting has not been directly acquired through natural selection.—

[3] <I think> [MS damaged] that you will be pleased <with> [MS damaged] the 2d vol. or Part of Lyell’s Principles, just out—7

In regard to sexual selection. A girl sees a handsome man, & without observing whether his nose or whiskers are the tenth of an inch longer or shorter than in some other man, admires his appearance & says she will marry him. So I suppose with the pea-hen; & the tail has been increased in length merely by on the whole presenting a more gorgeous appearance. J. Jenner Weir8, however, has given me some [one illeg. word crossed out] facts showing that birds apparently admire details of plumage.—

Yours most sincerely | C. Darwin [signature]

A circled pencil annotation adds the date "March 1868" in the top left-hand corner of page 1. The exact date of 21 March 1868 has been established by the Darwin Correspondence Project see DCP-LETT-6033.
Darwin, George Howard (1845-1912). Astronomer and mathematician and 2nd son of Charles Robert Darwin.
At the University of Cambridge, a Wrangler refers to a student who gains first-class honours in the third year of an undegraduate degree in mathematics. The highest scoring student is the Senior Wrangler and the second highest scoring student is the Second Wrangler. George Darwin held the place of Second Wrangler in 1868. (Darwin, F. 1916. Memoir of Sir George Darwin. In Stratton, F. J. M & J. Jackson (Eds.) The Scientific Papers by Sir George Howard Darwin. Vol. 5. Cambridge: Cambridge University Press. p.xii.)
See enclosure WCP1893.4433.
Edwards, Ernest (1837-1903). British photographer who invented the heliotype process of photomechanical reproduction.
See Darwin, C.R. 1868. The Variation of Animals and Plants Under Domestication. 2 vols. London: John Murrary, Vol. 2. pp.185-186.
Lyell, C. 1868. Principles of Geology, 10th edition. 2 vols. London, UK: John Murray.
Weir, John Jenner (1822-1894). British amateur entomologist, ornithologist and civil servant.

Enclosure (WCP1893.4433)

[1]

5

"The result is, that in this area hybrids will not increase so rapidly as before."1

The fact, that the two forms of the Species have become slightly sterile together, implies that in this "certain definite area" after some period after the epoch when the observations are supposed to begin the total number of individuals is less than it was initially. At this period these individuals consist of the two pure forms and a certain number of hybrids. Outside the "area" the number of individuals will be the same as at first, and [2] the population will consist of the two pure forms and hybrids.—

It is in the number of these hybrids that the decrease of population in the "area" arises, and that outside the area the population is kept up.— Thus inside the area there will be a deficiency, and this which may and certainly will be made up; this may take place in one of two ways— or in a combination of them— viz (1) by invasion from the outside (2) by greater numbers of the families of the pure forms surviving, thro’ [3] being less crowded. Now as the Struggle will take place between the young animals inside the area & old ones outside— it appears almost certain that invasion will take place. Thus if we suppose all the animals in the "area" to crowd together to yield to the external pressure— the area (the space occupied by the physiological variety) may be said to decrease in size. According to Mr. Wallace’s argument this area is to be the reservoir from which the inter-sterility of the two forms all over the country is [4] to flow. And this area will continue to decrease. Thus although the races inside the area are purer than those outside they continually diminish in numbers.

[5]

13

It is assumed that there are no cross unions between AS BS.— This seems unfair[.] For as AS & AF are indistinguishable to one another & also BS BF[,] there is no reason to suppose that AS will not couple as often with BS as AF with BF (unless the disinclination be assumed so great as prevent it entirely).

Now after the first generation the offspring of the S’s may be represented by

AS + BS + (AB)S & (AB)S = 0 [6] & the offspring of the F’s by AF + BF + (AB)F[.] Also in these two expressions AS = AF-BS = BF & (AB)F is not = 0

.:. The offspring of the F’s will be more numerous than of the S’s— Thus there will be a decrease of population among the S’s. And the effect is the same as in the first case

George Darwin quotes from ARW's notes on sterility see WCP1889.4067.

Published letter (WCP1893.5980)

[1] [p. 204]

4 Chester Place, Regent's Park, N W. March 19-24, 1868.

My dear Wallace, — I have sent your query to Cambridge to my son. He ought to answer it, for he got his place of Second Wrangler chiefly by solving very difficult problems. I enclose his remarks on two of your paragraphs: I should like them returned some time, for I have not studied them, and let me have your impression.

I have told E. Edwards to send one of my large photographs to you addressed to 76½ Westbourne Grove, not to be forwarded. When at home I will send my carte.

The sterility is a most (? puzzling) problem. I can see so far, but I am hardly willing to admit all your assumptions, and even if they were all admitted, the process is so complex and the sterility (as you remark in your note) so universal, even with species inhabiting quite distinct countries (as I remarked in my chapter), together with the frequency of a difference in reciprocal unions, that I cannot persuade myself that it has been gained by Natural Selection, any more than the difficulty of grafting distinct genera and the impossibility of grafting distinct families. You will allow, I suppose, that the capacity of grafting has not been directly acquired through Natural Selection.

I think that you will be pleased with the second volume or part of Lyell's Principles, just out.

In regard to sexual selection. A girl sees a handsome man, and without observing whether his nose or whiskers are the tenth of an inch longer or shorter than in some other man, admires his appearance and says she will marry him. So, I suppose, with the pea hen; and the tail has been increased in length merely by, on the whole, presenting a more gorgeous appearance. Jenner Weir, however, [2] has given me some facts showing that birds apparently admire details of plumage. — Yours most sincerely, C. DARWIN.

Please cite as “WCP1893,” in Beccaloni, G. W. (ed.), Ɛpsilon: The Alfred Russel Wallace Collection accessed on 29 March 2024, https://epsilon.ac.uk/view/wallace/letters/WCP1893