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Letter 6851

Darwin, C. R. to Lubbock, John

3 Aug 1869

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    Sexual differences in Labidocera darwinii, in Entomostraca, and Myriapoda.

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Aug 3d. 1869

My dear Lubbock

I am at home again & thank Heavens at work again; & I want very much to plague you with 2 or 3 questions.

I write to mention, (& perhaps give woodcut) as curious sexual difference, the right-hand antenna in ♂ Labidocera, Darwinii as described by you in Annal & Mag Vol. XI. (1853) Pl. I. Now will you tell me in a few words the character of the left-hand antenna, which resembles both antennæ in ♀.— May I say that these antennæ consist of ``simple tapering joints less in number than in the right-hand antenna?'' Or are the joints equally numerous, though different in form?

In the Crustacean which has the right-antenna modified, is one of the hinder thoracic legs generally or only sometimes converted into a forceps? & is this forceps on the same right side of the body with the modified right antenna?

Lastly, I can find no account of any secondary sexual differences in the Myriapoda, except that it is said (I know not  do you know? whether on good authority) that in Lithobius the female has a pair of pincers or forceps at entrance of vulva.— Do you know whether the males ever differ from ♀s in size, colour, jaws for fighting, or prehensile organs?

I have looked at the sentence in the Origin about which you wrote, but I find that I do not so expressly imply that Agassiz believes in descent or derivation of species: I have, however, by mere good luck altered the sentence in the new Edit. of Origin.—

Have you settled anything about Mr Powell.

Pray forgive me for troubling you & believe me | My dear Lubbock | Yours most truly | Ch. Darwin

P.S. One other question: in such Entomostraca as you know are the males larger than the females, as is the case with the stalk-eyed & sessile-eyed crustaceans?

    Footnotes Add

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    f1 6851.f1
    The Darwins arrived home from Wales on 31 July 1869 (see `Journal' (Correspondence vol. 17, Appendix II)).
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    f2 6851.f2
    CD discussed sexual differences in the antennae of the copepod species Labidocera darwinii in Descent 1: 329, and reproduced part of the plate that accompanied Lubbock's description of the organism in Annals and Magazine of Natural History (Lubbock 1853).
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    f3 6851.f3
    Lithobius is a genus of centipedes in the arthropod subphylum Myriapoda.
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    f4 6851.f4
    See letter from John Lubbock, 2 July [1869]. In Origin 4th ed., pp. 532--3, CD wrote: As the embryonic state of each species and group of species shows us more or less completely the structure of their less modified ancient progenitors, we can see why ancient and extinct forms of life should resemble the embryos of our existing species, their descendants. Agassiz believes this to be a law of nature; but I am bound to confess that I only hope to see the law hereafter proved true. He altered this in Origin 5th ed., p. 534, to read: As the structure of the embryo generally shows us more or less plainly the structure of its less modified and ancient progenitor, we can see why ancient and extinct forms so often resemble the embryos of existing species in the same class. Agassiz believes this to be a universal law of nature; and I hope to see it hereafter shown in most cases true.
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    f5 6851.f5
    CD refers to Henry Powell. See letter from John Lubbock, 20 July [1869] and n. 2.
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    f6 6851.f6
    Entomostraca was formerly used to refer to all crustaceans other than Malacostraca (Leftwich 1973).
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