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Darwin Correspondence Project

To J. D. Hooker   3 and 4 August [1866]1

Down.

Aug. 3rd.

My dear Hooker

Manny thanks for Acropera & about the book. I will take your letter seriatim.2 There is good evidence that S.E. England was dry land during glacial period. I forget what Austin says but mammals prove, I think, that England has been united to the Continent since the glacial period.3 I don’t see your difficulty about what I say on the breaking of an isthmus: if Panama was broken thro’, wd. not the fauna of the Pacific flow into the W. Indies, or vice versâ, & destroy a multitude of creatures.4 Of course I’m no judge, but I thought De Candolle had made out his case about small areas of trees—5 You will find at P. 112 3rd. edit. Origin a too concise allusion to the Madeira flora being a remnant of the tertiary European flora.6

I shall feel deeply interested by reading your botanical difficuties against occasional immigration. The facts you give about certain plants such as the Heaths are certainly very curious. I thought the Azores flora was more boreal: but what can you mean by saying that the Azores are nearer to Britain & Newfoundland than to Madeira? on the Globe they are nearly twice as far off.7 With respect to sea-currents, I formerly made enquiries at Madeira but cannot now give you the results but I remember that the facts were different from what is generally stated; I think that a ship wrecked on the Canary Islands was thrown up on the coast of Madeira.8 You speak as if only land shells differed in Madeira & Po. Santo: does my memory deceive me that there is a host of representative insects?9

When you exorcise at Nottingham occasional means of transport, be honest, & admit how little is known on the subject.10 Remember how recently you & others thought that Salt-water would soon kill seeds.11 Reflect that there is not a coral-islet in the ocean which is not pretty well clothed with plants: & the fewness of the species can hardly with justice be attributed to the arrival of few seeds, for coral-Islets close to other land support only the same limited vegetation.12 Remember that no one knew that seeds wd remain for many hours in the crops of birds & retain their vitality; that fish eat seeds & that when the fish are devoured by birds the seeds can germinate &c &c—13 Remember that every year many birds are blown to Madeira & to the Bermudas. Remember that dust is blown 1000 miles over the Atlantic.14 Now bearing all this in mind, wd it not be a prodigy if an unstocked Island did not in the course of ages receive colonists from coasts, whence the currents flow, trees are drifted, & birds are driven by gales. The objections to islands being thus stocked are, as far as I understand, that certain species & genera have been more freely introduced & others less freely than might have been expected. But then the sea kills some sorts of seeds, others are killed by the digestion of birds & some wd be more liable than others to adhere to birds feet; but we know so very little on these points that it seems to me that we cannot at all tell what forms wd probably be introduced & what wd not.15

I do not for a moment pretend that these means of introduction can be proved to have acted; but they seem to me sufficient, with no valid or heavy objections, whilst there are, as it seems to me, the heaviest objections, on geological & on geographical-Distribution grounds, (p. 387, 388, Origin) to Forbes’ enormous continental extensions.16 But I fear that I shall & have bored you.—

Yours ever affect— | C. Darwin.

P.S. Murray will not bring out, & be hanged to him, the new Edit. of Origin, though all printed off, till November.—17 I have persuaded him to send Lyell a copy; I do not suppose you wd. care to have your copy at once; if you did, I would ask Murray, but for some reason, he does not seem much to like sending out the copies.—18

Dont answer unless you like, for you must be very busy.—

P.S. Here is a bad job, the Acropera has not arrived.— I hope it was not sent off, as soon as you thought. I sent this evening (Friday) but no parcel at Station. If not there tomorrow it must be lost. It is a bad job for me & for you, if the plant is valuable.—19

P.S. 2d. As you were asking about Books on “Origin”; a very good Zoologist Claus has just published one, with my name on title-page—the subject being an investigation of the amount of individual variability in the Copepodous Crustaceans & he shows it is wonderfully great in many organs & that some co existing vars, are apparently passing into distinct species.—20

[pointing hand]

Acropera all safe Saturday morning

Footnotes

The year is established by the relationship between this letter and the letter from J. D. Hooker, 31 July 1866. In 1866, 4 August was a Saturday.
See letter from J. D. Hooker, 31 July 1866 and n. 2. Robert Alfred Cloyne Godwin-Austen considered the presence of mammals in the area of the English Channel and North Sea during the glacial and post-glacial periods, and showed their distribution during the ‘new Tertiary’ period in a map, in Austen 1851, pp. 131–5.
CD refers to Alphonse de Candolle. See letter from J. D. Hooker, 31 July 1866 and n. 5.
CD’s enquiry about sea currents to the Atlantic islands, and the response, have not been found. The only ship wrecked in the Canary Islands between 1836 and 1866 was the British steamship Niger. The Niger was wrecked at Santa Cruz, Tenerife, on 12 June 1857, but no records of its drifting thereafter have been found, nor any contemporary records of wrecks at Madeira. (Hugh Brown, International Registry of Sunken Ships, personal communication; see also The Times, 5 September 1857, p. 8.)
Representative species, in contemporary terminology, were similar but distinct species in different localities (see also Correspondence vol. 8, letter to C. J. F. Bunbury, 9 February [1860] and n. 4). The representative species of insects in Porto Santo and Madeira were discussed in Wollaston 1856, pp. 122–4; the representative land shells of the two islands were discussed in Wollaston 1856, pp. 128–35. There is an annotated copy of Wollaston 1856 in the Darwin Library–CUL (see Marginalia 1: 876–9). For more on representative species, see Affolter 1980, p. 7.
In his lecture at the British Association for the Advancement of Science meeting at Nottingham in August 1866, Hooker considered the evidence for both Edward Forbes’s ‘Atlantis’ and CD’s ‘occasional transport’ hypotheses about how similar species arrived at different points of the globe, referring to the latter as ‘trans-oceanic migration’ (J. D. Hooker 1866a, pp. 51, 75–6). For further information on the lecture and its publication, see the letter from J. D. Hooker, [24 July 1866], n. 4. For more on CD’s position on geographical distribution, see Correspondence vol. 6, and, this volume, letter to J. D. Hooker, 30 July [1866] and n. 7.
The fact that seeds could survive immersion in seawater was included in Hooker’s lecture as one of CD’s ‘many powerful arguments’ for trans-oceanic migration (J. D. Hooker 1866a, p. 51). On Hooker’s earlier disbelief in the ability of seeds to remain viable after contact with salt water, see Correspondence vol. 13, letter to J. D. Hooker, 22 and 28 [October 1865], n. 11. The results of CD’s experiments on the resistance of seeds to salt water are given in his paper ‘On the action of sea-water on the germination of seeds’, read on 6 May 1856 at the Linnean Society (Collected papers 1: 264–73), and in Origin, pp. 358–61.
In his lecture, Hooker reported CD as pointing out that coral islands, which had not ever been connected with continents, were well stocked with plants, and that oceanic islands were poor in plant species, lacking whole groups of continental plants, which would not have been the case had there been continental extension (J. D. Hooker 1866a, p. 51). See also Origin, pp. 360–1, 388–90.
See J. D. Hooker 1866a, p. 51. See also Origin, pp. 361–2, 387.
See J. D. Hooker 1866a, p. 51. On birds being blown to Bermuda and Madeira, see Origin, p. 90. In 1832, CD noted that dust from Africa fell on vessels in the Atlantic ocean (Journal of researches, p. 4). See also Correspondence vol. 2, and CD’s paper ‘An account of the fine dust which often falls on vessels in the Atlantic Ocean’, read on 4 June 1845 at the Geological Society of London (Collected papers 1: 199–203).
CD noted that islands supported fewer species of plants than equivalent continental areas in Origin, pp. 389–90. CD’s own experiments on seeds showed that species differed in their capacity to survive immersion in salt water (see Correspondence vol. 5, letters to Gardeners’ Chronicle, 21 May [1855] and 21 November [1855]). On CD’s interest in the distribution of seeds by adhesion to birds’ feet, see Correspondence vol. 13, letter from Alfred Newton, 27 October 1865, n. 5.
CD refers to the third edition of Origin and to Edward Forbes’s hypothesis of continental extension. See also letter from J. D. Hooker, 31 July 1866 and nn. 1 and 9.
CD refers to the fourth edition of Origin. See letter from John Murray, 18 July [1866].
Charles Lyell was probably named by CD in a now missing list of people who were to receive advance copies of the fourth edition of Origin (see letter to John Murray, 15 July [1866] and n. 3). On Murray’s inclination to dispatch presentation copies in November 1866, see the letter from John Murray, 23 July [1866].
CD had been informed by Hooker that a specimen of Acropera would be despatched on Wednesday 1 August, for collection at Bromley railway station (see letter from J. D. Hooker, 31 July 1866 and n. 22).
The reference is to Claus 1866, a paper on the copepods of Nice; there is a lightly annotated copy in the Darwin Pamphlet Collection–CUL. In his interpretation of copepod morphology and variations, Carl Friedrich Claus referred to CD’s transmutation theory; the subtitle of the paper may be translated, ‘An essay on the characteristics of the form and their variation “in the Darwinian sense’”.

Summary

Answers JDH’s questions on connection of SE. England and continent,

on the effect of breaking the Isthmus of Panama,

and on Madeira flora as remnant of Tertiary flora.

Cautionary remarks for JDH on his "Insular floras" speech, designed to strengthen case of "occasional migration" theory.

Letter details

Letter no.
DCP-LETT-5174
From
Charles Robert Darwin
To
Joseph Dalton Hooker
Sent from
Down
Source of text
DAR 115: 295, 295b
Physical description
8pp

Please cite as

Darwin Correspondence Project, “Letter no. 5174,” accessed on 20 October 2017, http://www.darwinproject.ac.uk/DCP-LETT-5174

Also published in The Correspondence of Charles Darwin, vol. 14

letter