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Darwin Correspondence Project

To Moritz Wagner   13 October 1876

Down, | Beckenham, Kent [Bassett, Southampton.]

Oct. 13. 1876

Dear Sir

I have now finished reading your essays, which have interested me in a very high degree, notwithstanding that I differ much from you on various points.1 For instance several considerations make me doubt whether species are much more variable at one period than at another, except thro’ the agency of changed conditions,2 I wish however that I could believe in this doctrine, as it removes many difficulties. But my strongest objection to your theory is that it does not explain the manifold adaptations in structure in every organic being,—for instance in a Picus for climbing trees & catching insects,—or in a Strix for catching animals at night, & so on ad inifinitum.3 No theory is in the least satisfactory to me unless it clearly explains such adaptations. I think that you misunderstand my views on isolation. I believe that all the individuals of a species can be slowly modified within within the same district, in nearly the same manner as man effects by what I have called the process of unconscious selection; as has happened with our English race horse or our English pointer-dogs.4 I do not believe that one species will give birth to two or more new species, as long as they are mingled together within the same district. Nevertheless I cannot doubt that many new species have been simultaneously developed within the same large continental area; and in my ‘Origin of Species’ I endeavoured to explain how two new species might be developed, although they met and intermingled on the borders of their range.5 It would have been a strange fact if I had overlooked the importance of isolation, seeing that it was such cases as that of the Galapagos Archipelago, which chiefly led me to study the origin of species.6 In my opinion the greatest error which I have committed, has been not allowing sufficient weight to the direct action of the environment, i.e. food, climate, &c., independently of natural selection. Modifications thus caused, which are neither of advantage nor disadvantage to the modified organism, would be especially favoured, as I can now see chiefly through your observations, by isolation in a small area, where only a few individuals lived under nearly uniform conditions.

When I wrote the ‘Origin,’ and for some years afterwards, I could find little good evidence of the direct action of the environment; now there is a large body of evidence, and your case of the Saturnia is one of the most remarkable of which I have heard.7 Although we differ so greatly, I hope that you will permit me to express my respect for your long-continued and successful labours in the good cause of natural science.

I remain, dear Sir, yours very faithfully, | Charles Darwin.

Footnotes

CD had received a copy of Wagner’s multi-part essay on species formation in September 1876 (Wagner 1875; see letter to Karl von Scherzer, 22 September 1876 and n. 1). CD’s heavily annotated copy is in the Darwin Pamphlet Collection–CUL.
Wagner, in line with his primary claim that isolation was the efficient cause of speciation, argued that the variability of species was greater when the opportunities for migration, both active and passive, were increased (see Wagner 1875, pp. 451–2).
Picus is a genus of woodpeckers; Strix is a genus of owls.
CD discussed the process of unconscious selection in Origin, pp. 34–40, using English pointer dogs, racehorses, and other domesticated animals as examples.
In Origin, p. 173, CD discussed cases in which allied species met and intermingled at the limits of their geographical range, and yet remained distinct. In such cases, he argued, one species did not give rise to the other, but rather both were descended from a common stock.
On the role of the Galápagos islands, especially its species and varieties of birds, in shaping CD’s views on transmutation, see M. J. S. Hodge 2010.
Wagner gave the case of cocoons from a moth, Saturnia luna (a synonym of Actias luna, the luna moth), that were transported from Texas to Switzerland, and developed into adults with a completely different colour pattern. Wagner believed that a new species had thus been formed and gave it the name Saturnia bolli (see Wagner 1875, pp. 491–2).

Bibliography

Hodge, M. J. S. 2010. Darwin, the Galápagos and his changing thoughts about species origins: 1835–1837. Proceedings of the California Academy of Sciences 4th ser. 61 (Supplement II, no. 7): 89–106.

LL: The life and letters of Charles Darwin, including an autobiographical chapter. Edited by Francis Darwin. 3 vols. London: John Murray. 1887–8.

Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.

Wagner, Moritz. 1875. Der Naturproceß der Artbildung. Das Ausland, 31 May 1875, pp. 425–8; 7 June 1875, pp. 449–52; 14 June 1875, pp. 473–5; 21 June 1875, pp. 490–3; 28 June 1875, pp. 513–16; 19 July 1875, pp. 570–5; 26 July 1875, pp. 589–93.

Summary

Comments on essays by MW [Das Ausland, May 1875]. Criticises his theory of isolation as source of species change: "But my strongest objection to your theory is that it does not explain the manifold adaptations in structure in every organic being". Believes MW has misunderstood his views: "I believe that all the individuals of a species can be slowly modified within the same district … I do not believe that one species will give birth to two or more new species, as long as they are mingled together within the same district."

Letter details

Letter no.
DCP-LETT-10643
From
Charles Robert Darwin
To
Moritz Friedrich (Moritz) Wagner
Sent from
Bassett Down letterhead
Source of text
DAR 148: 198; LL 3: 159
Physical description
2pp inc

Please cite as

Darwin Correspondence Project, “Letter no. 10643,” accessed on 28 September 2021, https://www.darwinproject.ac.uk/letter/DCP-LETT-10643.xml

Also published in The Correspondence of Charles Darwin, vol. 24

letter