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 thanks 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
[Enclosure]
No XVI p. 368
I have not seen Baer’s original statement, only an abstract; but I think his arguments for the identity of the guinea-pig & aperea are weak. Isid. G. St Hilaire makes out a strong case against their identity. I can now add from Denny that their pediculi are (almost or quite) generically different. It seems to me rash to trust in Baer’s view.3
p. 372— Near bottom. Sentence about “specifically” & “genetically” distinct seems to me obscure (and this is something wonderful in your writing;) a clear minded person conversant with the subject to whom I shewed the sentence could not understand it.4
No XVIII p. 627. This page also does not strike me as very clear; when you speak of “fundamental characters” being similar any one would suppose that you meant homological.5
No XVIII. p 627 (Near bottom) You will find in the Origin a discussion, which I was compelled greatly to abbreviate, on analogical resemblances, not due to community of descent. I hope you will take the trouble just to look at this, owing to what you say at p. 625 & especially at p. 75 in No XIX.6 I think you will see that I do not attribute all organic resemblances to community of kinship: I wish I had published more on this subject.
No XIX p. 64. I think a sentence ought to be added that the mystery which perplexes naturalists is why one, for instance, of two closely allied plants is greatly affected by a slightly higher temperature & not the other.7
p. 68. You will never, I think, get rid of the term rudimentary organ for what evidently would be an organ if it could act. A violin with broken strings would by every one be called an instrument tho’ at that time not capable of yielding music.8
p. 76 I quite agree & have always thought that such facts as the tendency to ramification in many parts of various organisms was simply due to the same so-called inorganic laws having acted on them.9
p. 76. I have also in my own mind always taken nearly the same view, I think, 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 result of the conditions of life or the medium, independently of natural selection, I cannot follow you. In my opinion there will always be confusion in every discussion, as long as the action of the external & internal conditions of life in causing variability is mixed up with either natural or artificial selection. In the formation of a breed of pigeons for instance, the conditions cause the successive variations, but man makes the breed by selection; & this distinction equally holds good under nature, though the conditions here determine what kind of variation shall be preserved. I could almost as soon admit that the whole structure of a woodpecker had originated from the action of the medium, as that organs so complex & so well co-ordinated to the whole organization as the luminous or electric organs should have thus originated. The impression which I have taken from the study of nature is strong that in all cases, if we cd collect all the forms which have ever lived, we shd have a close gradation from some most simple beginning. If similar conditions sufficed without the aid of selection to give similar parts or organs, independently of blood relationship, I doubt much whether we should have that striking harmony which we almost everywhere see, between the affinities, embryological development, geographical distribution, & geological succession of all allied organisms. We shd be much more puzzled than we are to class in a natural method the many existing & extinct forms. It is puzzling enough to distinguish between resemblances due to descent & to adaptation through selection; but (fortunately for naturalists) owing to the strong power of inheritance & the excessively complex causes & laws of variability, when the same end or object has been gained, somewhat different parts have generally been modified, or modified in a somewhat different manner, so that the resemblances due to descent & adaptation can usually be distinguished.
I shd. like to add, that we may understand each other, how, as I suppose, the luminous organs of insects, for instance, have been developed; but I must depend on conjecture, for so few luminous insects exist that we have no means of judging through the preservation of ancient slightly modified forms, of the probable gradations through which these organs have passed.10 Nor do we know of what use they are. We see that the tissues of many animals, as of certain centipedes, are liable under unknown conditions of food, temperature &c, occasionally to become luminous, like the inorganic pyrophorous mixtures. Such luminosity having been in some way advantageous to certain insects, the tissues as I suppose become specialized for this purpose in a regular manner & in an intensified degree, in one part of the body in some kinds & in other parts in other kinds. Hence I believe if all extinct insect-forms cd be collected we shd have a perfect gradation from the Elateridæ with their highly luminous thorax & from the Lampyridæ with their highly luminous abdomen to some ancient insect, which was occasionally luminous like the centipede.11 I do not know, but I suppose that the microscopical structure of the luminous organs in these two families is nearly the same, & I shd attribute to inheritance from a common progenitor that similarity in their tissues, which under similar conditions caused them to vary in the same manner, & thus through natural selection for the same general purpose, to arrive at the same result.12
Mutatis mutandis I shd apply the same doctrine to the electric organs of fishes; but here I have to make the violent assumption that some ancient fish was occasionally slightly electrical without having any special organs for this purpose. It has however been stated, but on evidence not trustworthy that certain reptiles are thus electrical. It is possible that the so-called electric organs of fishes, whilst partially developed, may have sub-served some distinct function; at least I am nearly sure that Matteucci cd detect no free electricity in certain fishes provided with the proper organs.13
In one of your former letters you alluded to nails, claws &c.14 From their perfect co-adaptation with the rest of the organization I cannot believe that they cd have been formed simply by the direct action of the medium. H. Spencer’s view that they were first developed from indurated skin, the result of pressure on the extremities, seems to me probable.15
In regard to thorns & spines, I suppose that stunted & somewhat hardened processes were primarily left by the abortion of various appendages, but I must believe that their extreme sharpness is the result of fluctuating variability & the “survival of the fittest”. The precise form, colour &c of the thorns I freely admit to be the result of the laws of growth of each particular plant & of the medium. It wd be an astounding fact if any varying plant suddenly bore perfect thorns without the aid of reversion or selection. That natural selection wd tend to produce formidable thorns will be admitted by every one 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 thus exposed to the attacks of mammals.16 In this country 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 was that the hooks were not perhaps first developed for climbing; but having been formed for protection were subsequently used & further modified for climbing.17
As the view which you have taken on the subject here discussed seems firmly fixed, I do not suppose 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, though too briefly & very badly done, & I hope it will not trouble you to read & consider it.—
C. Darwin
Footnotes
Bibliography
Baer, Karl Ernst von. 1864–76. Reden gehalten in wissenschaftlichen Versammlungen und kleinere Aufsätze vermischten Inhalts. Part 1: Reden. Part 2: Studien aus dem Gebiete der Naturwissenschaften. Part 3: Historische Fragen mit Hülfe der Naturwissenschaften. St Petersburg: H. Schmitzdorff.
Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 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.
Geoffroy Saint-Hilaire, Isidore. 1854–62. Histoire naturelle générale des règnes organiques, principalement étudiée chez l’homme et les animaux. 3 vols. Paris: Victor Masson.
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.
Lewes, George Henry. 1868b. Mr. Darwin’s hypotheses. Fortnightly Review n.s. 3: 353–73, 611–28; 4: 61–80, 492–509.
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.
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.
Summary
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.
- DCP-LETT-6308
- From
- Charles Robert Darwin
- To
- George Henry Lewes
- Sent from
- Freshwater
- Source of text
- DAR 185: 42; Argyll Papers, Inveraray Castle (NRAS 1209/985)
- Physical description
- ALS 3pp, encl
Please cite as
Darwin Correspondence Project, “Letter no. 6308,” accessed on 26 September 2022, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-6308.xml
Also published in The Correspondence of Charles Darwin, vol. 16