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.