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Darwin Correspondence Project

To H. G. Bronn   5 October [1860]

Down Bromley Kent [Eastbourne]

Oct. 5

Dear & much respected Sir

I ought to apologise for troubling you; but I have at last carefully read your excellent criticisms on my Book.—1 I agree with much of them, & wholly with your final sentence.2 The objections & difficulties, which may be urged against my view, are indeed heavy enough almost to break my back; but it is not yet broken! You put very well & very fairly that I can in no one instance explain the course of modification in any particular instance. I could make some sort of answer to your case of the two Rats;3 & might I not turn round, & ask him, who believes in the separate creation of each species, why one Rat has a longer tail or shorter ears than another? I presume that most people would say that these characters were of some use or stood in some connection with other parts; & if so, natural selection could act on them. But as you put the case, it tells well against me. You argue most justly against my question, whether the many species were created as eggs or as mature &c;4 I certainly had no right to ask that question.—

I fully agree that there might have been as well 100,000 creations as 8 or 10, or only one. But then on the view of 8 or 10 creations, (i.e. as many as there are distinct types of structure) we can on my view understand the homological & embryological resemblances of all the organisms of each type; & on this ground almost alone I disbelieve in the innumerable acts of creation.—   There are only two points on which, I think, you have misunderstood me: I refer only to one Glacial period as affecting the distribution of organic beings: I did not wish even to allude to the doubtful evidence of Glacial action in the Permian & Carboniferous periods.5 Secondly, I do not believe that the process of development has always been carried on at the same rate in all different parts of the world.6 Australia is opposed to such belief.— The nearly contemporaneous equal development in past periods I attribute to the slow migration of the higher & more dominant forms over the whole world; & not to independent acts of development in different parts.—   Lastly, permit me to add that I cannot see the force of your objection, that nothing is effected until the origin of life is explained:7 surely it is worth while to attempt to follow out the action of Electricity, though we know not what electricity is.

If you should at any time do me the favour of writing to me, I should be very much obliged if you would inform me, whether you have yourself examined Brehm’s sub-species of Birds;8 for I have looked through some of his writings, but have never met an Ornithologist who believed in his w〈orks.〉 Are these sub-species really characteristic of certain different regions of Germany?

Should you write, I should much like to hear how the German Edition sells.—

With my once more sincerely expressed gratitude & with entire respect | I beg leave to remain | Dear & Honoured Sir | Yours sincerely & respectfully | Charles Darwin

CD note:9

Bronn’s Criticisms for New Edit of Origin.

Objects that I cannot precisely say why *two species of Rats [interl] Hare & rabbit assumed by selection their several [interl] present characters— very true I can in no case say this— we know so little of use of parts & laws of correlation.— *But I confess, I thus evade every special difficulty. Why one gets round & another pointed leaves. [added]

Objects that in case of two varieties still living in abundance side by side how can intermediate vars *have been exterminated [above del ‘be living’]— But are there such cases, excluding such vars. as albinoe.— Do not they inhabit distinct countries or stations— surely this is the general rule.—

Do you believe in Brehms sub-species. Have you seen them?10

Thinks that varieties arising from external conditions are linked together by intermediates—not those produced by n. selection.—

Why of two cells, primordial, one got volition & sensation & one did not.—

Says I ought to answer [‘ho’ del] whether my primordial forms were created as eggs or full-grown &c.— Admits that vegetable-cell wd. come first.

I think Schiodte says the eyes not so completely gone, at least from more related to those of external world [n‘ del] near entrance of cave—11 [ave-Rat regained some sight’ del]12

I shd never suppose with respect to his supposed changes in 2 Rats, that first longer or shorter tail & larger [interl] ears were acquired, but that all were modified together.—

*Might I not ask Creationist why tail longer or ear shorter? I could not ask this of him who believes that God makes his creation different for mere variety—like man fashions a pattern for mere variety. [added pencil]

Objects there might 〈have be〉en 100,000 creations as well as one; I agre〈e, b〉ut then these would not have borne signs of common descent in homologies & embryology & rudimentary organs.

Some mistake about my supposing several glacial periods— Permian & Chalk.—

“Why shd the process of development have always carried on same rate in all different parts of world?” I do not believe so— N. Zealand & Australia.

** I cannot see force of your objection because one cannot explain origination of life— **the far grandest problem of any [interl] why it wd not be gain to explain or account for forms; if this could be done — so we [o` del] do not know what electricity is, but we trace its action.— [del pencil]

I fully agree to your final sentence—& I fully admit the many awful difficulties in my view.

Certainly, as he grants 〈    〉 that both yet descended from one common parent.

As I cannot justify my opinions in any one single case, so I need not in any.—is as [over ‘very’] true *as it is [above del ‘& very’] severe.—

Though I can in no single instance, (except by conjecture, as longer legs of Hare for fleetness & not for [form]—longer ears to hear with) explain changes [‘with’ del] yet the structure &c led me to conclusion.— Laws of Variation will hereafter be made out far clearer.


CD had received a copy of the first part of Bronn’s German translation of Origin in April 1860 (see letter to H. G. Bronn, 10 April [1860]); he received the third and final part in July (see letter to H. G. Bronn, 14 July [1860]). An incomplete copy of the book (Bronn trans. 1860) is in the Darwin Library–CUL. At CD’s suggestion, Bronn had added to the translation a final chapter giving his own comments on CD’s views (see letter to H. G. Bronn, 4 February [1860]). CD refers to reading this final chapter. The chapter, however, was removed from CD’s copy. It has not been located in the Darwin Archive, and nor has the translation made for CD by Camilla Ludwig, the Darwins’ governess. Notes relating to Bronn’s criticism are tipped into CD’s copy (see CD note, above). It seems probable that CD did not read much of the German text since all but a few of the pages in his copy are uncut. He addressed Bronn’s final chapter of criticisms at length, however, in the third edition of Origin.
Bronn trans. 1860, p. 520: ‘Nur aus dem Widerstreite der Meinungen wird die Wahrheit hervorgehen und der Urheber dieser Theorie selbst zweifelsohne noch die grosse Befriedigung erleben, der Naturforschung einen neuen Weg geöffnet zu haben.’ [nly out of the conflict of opinions will the truth be forthcoming, and the originator of this theory will himself no doubt experience the great satisfaction of having opened a new path for scientific research.’]
Bronn trans. 1860, pp. 504–5. Bronn discussed the case of the two species of rat, the black or house-rat (Rattus rattus) and the brown or Norway rat (R. norvegicus). Bronn asked how CD’s theory could account for their derivation—either one from the other or both from some ancestral progenitor. Differences between the two—colour and the length of ears and tail—did not appear to provide any selective advantage to either. Moreover, no forms intermediate between the two had ever been identified. CD mentioned the case in the third edition of Origin, admitting that he could ‘give no definite answer to such questions’ (Origin 3d ed., pp. 140–1; Peckham ed. 1959, p. 232). See also CD note, above.
In Origin, p. 483, CD asked: ‘Were all the infinitely numerous kinds of animals and plants created as eggs or seed, or as full grown?’ Bronn explored this question further, asking whether these original forms were created simultaneously or successively in time. ‘Obviously either an entire nature-system must have been created at once or they must have developed gradually from a point in the far distant past.’ (translated from Bronn trans. 1860, p. 515). Perhaps because of Bronn’s criticisms, the passage in Origin was amended in the third edition to include the sentence: ‘Undoubtedly these same questions cannot be answered by those who, under the present state of science, believe in the creation of a few aboriginal forms, or of some one form of life.’ (Origin 3d ed., p. 517).
Bronn referred to ‘viele Eiszeiten’ (Bronn trans. 1860, p. 517).
Bronn trans. 1860, p. 517. See also Origin, p. 313.
Bronn trans. 1860, p. 519. Bronn had made the same point in his review of Origin (Bronn 1860a). CD had been careful to omit from the tenets of his theory of species change any reference to the origin of life itself.
CD had studied Brehm 1831 closely when he was writing the chapter on ‘Variation under nature’ for his ‘big book’ on species (Natural selection). See Correspondence vol. 6, letters to E. W. V. Harcourt, 19 August [1856] and 23 August [1856]. He mentioned Christian Ludwig Brehm’s reputation for describing as species birds that other naturalists only recognised as varieties, yet he also noted that ‘Brehm was a laborious observer’ (Natural selection, p. 114).
The note is tipped into CD’s copy of Bronn trans. 1860 (Darwin Library–CUL). The final page was marked in pencil by CD: ‘168’. The meaning of this number is unclear.
See n. 8, above.
CD refers to Jörgen Matthias Christian Schiödte’s study of blind cave insects. CD cited Schiödte [1849] in Origin, p. 138.
The reference is to Benjamin Silliman Jr’s study of the blind rats of the Mammoth Cave in Kentucky (Silliman 1851). See letter from Benjamin Silliman Jr, 27 October 1860.


Brehm, Christian Ludwig. 1831. Handbuch der Naturgeschichte aller Vögel Deutschlands. Ilmenau: Bernh. Friedr. Voigt.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Natural selection: Charles Darwin’s Natural selection: being the second part of his big species book written from 1856 to 1858. Edited by R. C. Stauffer. Cambridge: Cambridge University Press. 1975.

Origin 3d ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 3d edition, with additions and corrections. By Charles Darwin. London: John Murray. 1861.

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.

Schiödte, Jörgen C. [1849]. Bidrag til den underjordiske Fauna. Det Kongelige Danske Videnskabernes Selskabs Skrifter. Naturvidenskabelig og Mathematisk n.s. 2 (1851): 1–39. [Vols. 6,8]


Answers HGB’s criticism of Origin.

Explains HGB’s case of differences in rats by adaptation.

CD’s view explains homological and embryological resemblances of each type.

Does not believe all development is at same rate. Cites Australian forms.

Does not see force of objection that origin of life must be explained.

Asks if C. L. Brehm’s subspecies of birds are really characteristic of regions of Germany.

Letter details

Letter no.
Charles Robert Darwin
Heinrich Georg Bronn
Sent from
Eastbourne Down letterhead
Source of text
Cleveland Health Sciences Library (Stecher collection)
Physical description
3pp & Adraft 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 2940,” accessed on 16 June 2021,

Also published in The Correspondence of Charles Darwin, vol. 8