Thanks AD for his paper on "Morphology of the Arthropoda" [Rep. BAAS 37 (1867) pt 2: 82], a deeply interesting subject.
Suggests he examine specimens of Scalpellum.
Fritz Müller thinks CD is mistaken, but CD cannot persuade himself he was wrong in his observations on Balanidae [Living Cirripedia 2: 105].
Down. | Bromley. | Kent. S.E.
I thank you sincerely for having sent me your paper on the morphology of the Arthropoda, which I was very curious to read. It is a most deeply interesting subject, & if you finally succeed in showing how far the head-organs are homologous in the various classes, you will indeed have achieved a triumph in science.— Allow me to thank you cordially for the generous & much too honourable manner in which you refer to my work.—
If you could get fresh specimens of Scalpellum (Cirripedia), you would probably succeed in finding just-hatched larvæ in the sack; & these larvæ are so large that they are excellent for observation.
I cannot yet quite persuade myself that the view which I have taken in my vol. on Balanidæ p. 105, of the homologies of the appendages is wrong. I still believe (though Fritz Müller writes to me that he thinks I am mistaken) that I saw in the anterior-lateral horns of the Carapace, the prehensile antennæ in process of development. I sincerely wish you success in your studies, than which nothing can be more interesting.
I received some time ago a valuable memoir from you on certain ancient fossil insects, for which I am much obliged.
When you next see Prof. E. Häckel, pray give him my kindest remembrances.
With the most sincere respect, I remain | Dear Sir | Yours very faithfully | Ch. Darwin
- f1 5698.f1CD refers to a paper read by Dohrn on 5 September 1867 at the annual meeting of the British Association for the Advancement of Science (Dohrn 1867; see also Report of the thirty-seventh meeting of the British Association for the Advancement of Science held at Dundee, Transactions of the sections, p. 82, for a brief summary of the paper). CD's lightly annotated copy of Dohrn 1867 is in the Darwin Pamphlet Collection--CUL.
- f2 5698.f2Dohrn had claimed to have found that the carapace and head-plate in the larval forms of the crustacean genus Cuma and the insect genus Phryganea (caddis-flies) were homologous structures that became the branchial apparatus in adult Cuma and the antennae in adult Phryganea (Dohrn 1867, p. 86). Earlier, Fritz Müller had argued that larval stages in insects were acquired rather than inherited, but did not completely discount the possibility of a common ancestry for Crustacea and Insecta (F. Müller 1864, pp. 80--1; Dallas trans. 1869, pp. 118--21; Müller expanded his argument considerably for the English translation).
- f3 5698.f3Dohrn wrote that the application of Darwinian principles would solve difficulties that had beset studies of the morphology of arthropods for more than fifty years (Dohrn 1867, p. 86).
- f4 5698.f4CD had used Scalpellum vulgare and Balanus balanoides to illustrate the earliest larval stage of cirripedes in Living Cirripedia (1854), pp. 670--1, and plate 29, figs. 8 and 9.
- f5 5698.f5In Living Cirripedia (1854), pp. 104--5, CD described seeing an `articulated organ' within both the minute curved horns (frontal filaments) and great lateral horns (frontolateral or anterior lateral horns) of the larva of Scalpellum vulgare; he argued that these became the first and second antennae, respectively, and that the second antennae developed into the prehensile antennae of the final larval stage (usually called `pupa' by CD, but `cypris' became the accepted term; see Living Cirripedia (1851), pp. 9--10). For CD's view of the importance of homological relations for classification, see Correspondence vol. 4, Appendix II, pp. 391--9. CD's interpretation led to a long-standing debate with James Dwight Dana on the homologies of larval and adult organs (see Correspondence vols. 4 and 5 and Newman 1993, pp. 372--4). Müller's letter on the subject has not been found, but in 1865, CD had asked Müller to investigate observations made by August David Krohn that were at odds with CD's interpretation of cirripede morphology (see Correspondence vol. 13, letter to Fritz Müller, 10 August ). However, Müller, like Krohn, found the prehensile antennae were formed from the foremost limbs (in CD's terminology, the uniramous natatory legs; see Living Cirripedia (1854), pp. 670--1, and plate 29, figs. 8--10), not the anterior lateral horns, as CD believed (see Krohn 1860, p. 427, and F. Müller 1864, pp. 61--2 (Dallas trans. 1869, pp. 90--2)). For a comparison of CD's homologies with modern ones, see Newman 1993, p. 373 and fig. 7.
- f6 5698.f6The reference is to a paper on a newly discovered fossil insect that, according to Dohrn, demonstrated a link between Hemiptera and Neuroptera (Dohrn 1866, p. 334). CD's heavily annotated copy is in the Darwin Pamphlet Collection--CUL.
- f7 5698.f7Dohrn was Ernst Haeckel's student and assistant at Jena (Correspondence vol. 14, letter from Ernst Haeckel, 28 January 1866 and n. 7).