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Letter 1980

Darwin, C. R. to Lubbock, John

[1 Nov 1856]

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    Discusses arthropod structure and the nature of the corium.

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Sunday

Dear Lubbock

I have written to Hooker to enquire. The case has been described in Linn: Transactions.— Many of Spallanzanis experiments seemed to show that plants have been produced without pollen; but the subject has been discussed backwards & forwards of late years,—& largely by Gærtner in his Beitrage zur Kenntniss &c. But I cannot possibly spare this Book for about a fortnight. for I am using it daily.

I think your explanation of the inner saddle perfectly satisfactory; it is in fact Continuous with inner membrane of carapace, like the outer saddle is with the outer membrane of carapace.—

But I demur vehemently to your calling the under membrane of carapace “Corium” [DIAGRAM HERE] under & I suppose thin membrane of carapace upper & thick membrane of carapace The “corium”, I apprehend, wd be represented by the dotted line between these two membranes, & at each moult, would form a new upper & a new under membrane. Corium or true skin will never, I imagine, be freely exposed to water or air; its very nature, I apprehend, is to be covered with epidermis or chitine membrane, which it generates at each fresh moult.—

Your's very sincerely | C. Darwin

No doubt the corium itself is double or a fold

Would not longitudinal section of posterior end, together with tranverse section make things clearer?.— [DIAGRAM HERE] outer saddle old carapace new carapace Corium new carapace old carapace inner saddle

This would show how both inner & outer saddle were moulted together. You could give true outline longitudinally of carapace.

    Footnotes Add

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    f1 1980.f1
    Dated by the discussion of Lubbock's work on Daphnia (Lubbock 1857), which CD communicated to the Royal Society on 22 December 1856 (see letter to John Lubbock, 27 October [1856], n. 2). The first Sunday after the letter to John Lubbock, 27 October [1856], was 1 November 1856.
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    f2 1980.f2
    In Lubbock 1857, pp. 96–7, Lubbock described all the known cases in which agamic seeds had been found in plants, including that reported by John Smith, curator of the Royal Botanic Gardens at Kew, of the germination of seeds of Coelebogyne ilicifolia apparently without the presence of pollen (J. Smith 1841).
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    f3 1980.f3
    Spallanzani 1769. CD had read this work in 1839 (Correspondence vol. 4, Appendix IV, 119: 4a).
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    f4 1980.f4
    Gärtner 1844. Lubbock stated that Karl Friedrich von Gärtner doubted the truth of such observations (Lubbock 1857, p. 97).
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    f5 1980.f5
    CD was working on his chapter on crossing (Natural selection, pp. 35–91), in which Gärtner 1844 was frequently cited. He finished the chapter on 16 December 1856 (‘Journal’; Appendix II).
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    f6 1980.f6
    Lubbock's observations on the internal structure of the ephippium led him to believe that during the process of moulting the new carapace of Daphnia was formed between the upper and lower surfaces of the old carapace and that the new carapace was formed around a thin membrane, the corium (Lubbock 1857, p. 87).
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    f7 1980.f7
    Lubbock included both longitudinal and transverse sections in his plate of the carapace (Lubbock 1857, Pl. VII, figs. 4 and 5).
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