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Darwin Correspondence Project

To Gustav Jäger   9 September 1869

Down. | Beckenham | Kent. S.E.

Sep. 9 1869

Dear Sir

I lately received, but I do not know by whom sent, a copy of yr “Darwinsche Theorie,” & I hope that you will allow me to express the admiration & interest which it has excited in me.1 I must also thank you very sincerely for the manner in which you speak of my works. I am well aware that your generosity leads you to form much too high an estimate of what I have done; but it is deeply gratifying to receive the sympathy of so experienced an observer as yourself. As I am a very poor German scholar, I have as yet read only a portion; but I have already found many observations & incidental remarks of especial interest to me.

The case of the male silver pheasant who was rejected by the females when despoiled of his ornaments will be very useful to me to quote in what I am now writing. I wish you had specified a little more in detail in what manner the plumage was injured.2 If you have yourself observed any analogous facts with mammals or birds, & would be so obliging as to communicate them I shd feel particularly grateful.

Pray believe me dear Sir, with my best thanks & sincere respect | yours very faithfully | Charles Darwin.

P.S. I will venture to trouble you with one other question, on the chance of your having bred last year the Pavo spiciferus: I am very anxious to know whether the spurs in this Species are developed earlier or later in life, or at about the same period, as in the male of Pavo muticus.3

It wd be necessary to compare birds of the 2 species hatched last summer; for the spurs are quite small during the first year.

I fear that there is no chance of yr possessing both sexes of the mandrill baboon,—


There is an annotated copy of Jäger [1869] in the Darwin Library–CUL (see Marginalia 1: 429). This copy was evidently sent by Eduard Koch, who had informed CD about Jäger’s work (see letter from Eduard Koch, 17 June 1869, and letter to Eduard Koch, 22 June [1869]). Darwin later received another copy from Jäger himself (Correspondence vol. 18, letter to Gustav Jäger, 17 February 1870); this copy is now in the library of the Linnean Society. CD’s letter did not reach Jäger and was eventually returned after several months; CD then resent it, enclosed in his letter to Jäger of 17 February 1870 (Correspondence vol. 18).
Jäger had described a male pheasant who, after his ornamental plumage was spoiled, was superseded by a rival in competition for females (Jäger [1869], p. 59). CD cited this example in Descent 2: 120.
The Burmese peafowl (Pavo spiciferus) is now P. muticus spicifer. CD discussed the development of spurs in P. cristatus (the Indian peafowl) and P. muticus (the green peafowl) in Descent 1: 290, n. 28.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 26 vols to date. Cambridge: Cambridge University Press. 1985–.

Descent: The descent of man, and selection in relation to sex. By Charles Darwin. 2 vols. London: John Murray. 1871.

Jäger, Gustav. [1869.] Die Darwin’sche Theorie und ihre Stellung zur Moral und Religion. Stuttgart: Julius Hoffman.

Marginalia: Charles Darwin’s marginalia. Edited by Mario A. Di Gregorio with the assistance of Nicholas W. Gill. Vol. 1. New York and London: Garland Publishing. 1990.


Admires GJ’s book [Die Darwin’sche Theorie (1869)].

Asks about plumage of rejected male pheasant.

Letter details

Letter no.
Charles Robert Darwin
Gustav Jäger
Sent from
Source of text
Frau Dr. Hildegard Jaeger (private collection)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 6885,” accessed on 22 January 2020,

Also published in The Correspondence of Charles Darwin, vol. 17