To John Lubbock [1 November 1856]1
I have written to Hooker to enquire. The case has been described in Linn: Transactions.—2 Many of Spallanzanis experiments seemed to show that plants have been produced without pollen;3 but the subject has been discussed backwards & forwards of late years,—& largely by Gærtner in his Beitrage zur Kenntniss &c.4 But I cannot possibly spare this Book for about a fortnight. for I am using it daily.5
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”6 [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?.—7 [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.
Discusses arthropod structure and the nature of the corium.
Please cite as
Darwin Correspondence Project, “Letter no. 1980,” accessed on 25 February 2017, http://www.darwinproject.ac.uk/DCP-LETT-1980