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Darwin Correspondence Project

To G. H. Lewes   7 August [1868]1

Dumbola Lodge. | Freshwater | Isle of Wight

Aug. 7th

My dear Mr Lewes.

I have found very little to say, as you will soon discover; & the little is very badly said.—2 I have not noticed what I admire, but I must be permitted to say that on the second reading I have admired the whole, even much more than I did the first time.

The articles strike me as quite excellent, & I hope they will be republished; but I fear that they will be too deep for many readers.

Shd. I have anything to remark on any future article, I will write.

Accept my cordial thank for the kind & honouring way in which you allude to my work, & for the great pleasure which I have derived from reading the whole.—

Pray think a little over the verbal distinction of the action of the medium in causing variability & in leading to the preservation of the best adapted forms.

This surely is an important distinction; & it drives me half mad to see them brought all under one expression.—

Yours very sincerely | C. Darwin


Letter to G. H. Lewes

Aug. 7 1868.— against organs having been formed by direct action of medium in distinct organisms.—4

Chiefly Luminous & Electric Organs & Thorns—

p. 76. I have also in my own mind always taken I trust nearly the same view, as you maintain, about the luminous organs of insects or the electric organs of fishes; but if you maintain that these organs are the direct results of the conditions of life, or the medium independently of natural selection I cannot follow you.5

In my opinion there will always be confusion, in every discussion, as long as the action of the external & internal conditions of of life in causing variability or modification are confounded or mixed up with natural or artificial selection.— In the formation for instance of the breed of pouter pigeon; the conditions cause the successive variations, but man makes the breed by selection; and this distinction equally holds under nature, though the conditions [instead] of the will of man here determine the kind of selection. I could almost as soon admit that the whole structure of, for instance, a woodpecker, had thus originated; circumstances which cannot directly affect structure seems to me ought to impossible. Such organs as those above specified seem to me much too complex and generally too well & so complexly coordinated with the whole organisation, for the admission that they result from conditions independently of named selection. The impression which I have taken studying nature is strong, that in all cases if we could collect all the forms which have ever lived, we shd have a clear gradation from some most simple beginning. If similar conditions sufficed without the aid of natural selection to give similar parts or organs, independently of blood relationship, I doubt much whether we shd have that striking harmony between the affinities, embryological development, geograph. distrib, & geolog. succession of all allied organisms. We shd be much more puzzled than we now are how to class in a natural method many forms. It is puzzling enough to distinguish between resemblance due to descent & to adaptation; but (fortunately for naturalists) owing to the strong power of inheritance, & to excessively complex causes and laws of variability, when the same end or object has been gained, somewhat different parts have generally been modified, or modified in a different manner, so that the resemblances due to descent & adaptation can commonly be distinguished.

I shd like just to add, that we may understand each other, how I suppose the luminous organs of insects for instance, to have been developed, but I depend on conjectures; for so few luminous insects exist that we have no means of judging, & [through] the preservation to the present day of slightly modified forms, of the probable gradations, through which the organs have passed.6 Moreover we do not know of what use these organs are. We see that the tissues of many animals as certain centipedes in England are liable, under unknown conditions of food, temperature, &c, to become occasionally luminous; just like the pyrophorus mixture gives in [churned] Bog   Such luminosity having been advantageous to certain insects, the tissues, I suppose, become specialised for this purpose in an intensified degree, in certain insects in one part in other insects in other parts of the body. Hence I believe that if all extinct insect-forms could be collected, we shd have gradations from the Elateridæ7 with their highly & constantly luminous thorax’s & from the Lampyridæ8 with their highly luminous abdomens to some ancient insects, occasionally luminous like the centipede.

I do not know but suppose that the microscopical structure of the luminous organs in the most different insects is nearly the same, and I should attribute to inheritance from a common progenitor that the similarity of the tissues, which under similar conditions, allowed them to vary in the same manner, & thus through natural selection for the same general purpose, to arrive at the same result.

Mutatis mutandis I shd apply the same doctrine to the electric organs of fishes; but here I have to make in my own mind the violent assumption that some ancient fish was slightly electrical without having any special organs for the purpose. It has been stated on evidence not trustworthy, that certain reptiles are electrical. It is, moreover, possible that the so-called electric organs, whilst in a condition not highly developed may have subserved some distinct function: at least, I think Matteucchi cd detect no pure electricity in certain fishes provided with the proper organs.—9

In one of your letters you alluded to nails, claws, hoofs, &c.10 From their perfect coadaptation with the whole rest of the organisation, I cannot admit that they could have been formed by the direct action of the conditions of life. H. Spencer’s view that they were first developed from inherited skin, the result of pressure on the extremities, seems to me probable.11

In regard to thorns & spines, I suppose that stunted and [small] hardened processes were primarily left by the abortion of various appendages, but I must believe that their extreme sharpness & hardness is the result of fluctuating variability & “the survival of the fittest.” The precise form, curvature & colour of the thorns I freely admit the to be the result of the laws of growth of each particular plant, or of their conditions internal & external. It wd be an astounding fact if any varying plant suddenly produced, without the aid of reversion or selection perfect thorns. That natural selection would tend to produce the most formidable thorns will be admitted by everyone who has observed the distribution in S. America & Africa (vide Livingstone) of thorn-bearing plants, for they always appear where the bushes grow isolated & are exposed to the attacks of mammals.12 Even in England it has been noticed that all spine-bearing & sting-bearing plants are palatable to quadrupeds, when the thorns are crushed.— With respect to the Malayan climbing Palm, what I meant, to express is that the admirable hooks were perhaps not first developed for climbing; but having been developed for protection were subsequently used and perhaps further modified for climbing.13

As the view which you have taken on the subject here discussed seems firmly fixed, I do not suppose that anything which I have written, even supposing it mainly true, will have much influence; for I know by my own experience that a conclusion slowly arrived at cannot be quickly changed. But I have liked to say my say, & I hope it will not trouble you too much to read and consider it; but this discussion ought to have been been much fuller.


The year is established by the date on the draft enclosure.
See enclosure. Lewes had asked CD to comment on his articles in the Fortnightly Review on the theory of the origin of species by natural selection (Lewes 1868b), as he intended to turn them into a book (see letter from G. H. Lewes, 26 July 1868).
The original enclosure has not been found. A version of the draft transcribed here was also published by Francis Darwin in ML 1: 306–8.
In Lewes 1868b, Lewes argued that resemblances between organisms were not proof of common descent. He gave the examples of ‘widely-diffused spicula, setae, spines, hooks, tentacles, beaks, feathery forms, nettling-organs, poison-sacs, luminous organs etc.’ as having ‘the obvious impress of being due to a community of substance under similar conditions rather than to a community of kinship’ (Lewes 1868b, p. 625).
See n. 6, below. The note beginning ‘p. 76.’ was begun on the verso of the first sheet of the draft enclosure and continued on a separate sheet. The first sentence of the draft was crossed out, but read as follows: If you mean that in distinct animals, parts or organs, such for instance as the luminous organs of insects or the electric organs of fishes, are wholly [interl] the result [after del ‘direct’] of the external & internal conditions, to which the organs [interl] have been subjected, [‘to which … subjected,’ interl] in so direct and inevitable a manner that they wd be developed whether of use, or not to their possessor, I cannot admit.
In Lewes 1868b, p. 76, Lewes had written, ‘In noctilucae, earth-worms, molluscs, scolopendra, and fire-flies, we may easily suppose the presence of similar organic conditions producing the luminosity; it requires a strong faith to assign Natural Selection as the cause.’
The Elateridae are the family of click beetles.
The Lampyridae are the family of fireflies.
See Origin 4th ed., p. 224, and Pauly 2004, s.v. electric organs. CD refers to Carlo Matteucci.
See letter from G. H. Lewes, 2 March 1868.
CD refers to Herbert Spencer and to Spencer 1864–7, 2: 297. CD’s annotated copy of Spencer 1864–7 is in the Darwin Library–CUL (see Marginalia 1: 769–73.
See Variation 2: 296–7. CD refers to David Livingstone and Livingstone 1857; see also Correspondence vol. 8, letter to Daniel Oliver, 24 [September 1860] and n. 3.
In Lewes 1868b, p. 78, Lewes quoted a passage from Origin 4th ed., p. 235, as an example of CD’s giving weight to ‘organic laws’ rather than natural selection. The passage in Origin 4th ed. reads: A trailing palm in the Malay Archipelago climbs the loftiest trees by the aid of exquisitely constructed hooks clustered around the ends of the branches, and this contrivance, no doubt, is of the highest service to the plant; but as we see nearly similar hooks on many trees which are not climbers, the hooks on the palm may have arisen from unknown laws of growth, and have been subsequently taken advantage of by the plant undergoing further modification and becoming a climber. In Origin 5th ed., pp. 241–2, CD altered the second part of the passage to read: but as we see nearly similar hooks on many trees which are not climbers, and which there is reason to believe from the distribution of the thorn-bearing species in Africa and South America, serves [sic] as a defence against browsing quadrupeds, so the hooks on the palm may first have been developed for this object, and subsequently been taken advantage of by the plant as it underwent further modification and became a climber. For CD’s observations on the paucity of vegetation other than thorn bushes in the valleys of Patagonia, see Journal of researches 2d ed., p. 179.


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

Journal of researches 2d ed.: Journal of researches into the natural history and geology of the countries visited during the voyage of HMS Beagle round the world, under the command of Capt. FitzRoy RN. 2d edition, corrected, with additions. By Charles Darwin. London: John Murray. 1845.

Livingstone, David. 1857. Missionary travels and researches in South Africa; including a sketch of sixteen years’ residence in the interior of Africa, and a journey from the Cape of Good Hope to Loanda on the west coast; thence across the Continent, down the river Zambesi, to the Eastern Ocean. London: John Murray.

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.

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.

Origin 4th ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 4th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1866.

Origin 5th ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 5th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1869.

Pauly, Daniel. 2004. Darwin’s fishes. An encyclopedia of ichthyology, ecology, and evolution. Cambridge: Cambridge University Press.

Spencer, Herbert. 1864–7. The principles of biology. 2 vols. London: Williams & Norgate.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Thinks GHL’s articles are quite excellent; hopes they will be republished.

Discusses adaptation. Doubts whether similar conditions without selection can produce similar organs independent of blood relationship: "resemblances due to descent and adaptation can commonly be distinguished".

Discusses luminous insects, electrical organs of fish,

thorns and spines.

Letter details

Letter no.
Charles Robert Darwin
George Henry Lewes
Sent from
Source of text
DAR 52: A1–4, DAR 185: 42
Physical description
3pp, encl (copy) 7pp & Adraft 10pp

Please cite as

Darwin Correspondence Project, “Letter no. 6308,” accessed on 3 August 2020,

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