Ɛpsilon

From A. A. W. Hubrecht   2 December 1879

Leiden

2 Dec. 1879

Dear Sir,

Up to now I have shamefully neglected to send you my sincerest thanks for the kind and encouraging letter with which you replied to the impertinent appeal I made upon you to criticise an unripe hypothesis of mine.1 According to your advice and my own conviction I have provisionally put it back in its corner/drawer to see whether in time facts may be gleaned either supporting or invalidating it.

Since then I sent you a short account of the results I arrived at, regarding the affinities of the different genera of Nemerteans2

The anatomy of this group discloses other highly interesting facts, the principal of which I suppose to be the discovery of a central nervous system situated entirely above the intestine.3 Central in its character because down to the furthermost extremity of the tail a continuous and equal sheath of nerve cells accompanies a central bundle of fibres in the so called lateral nerves, which latter merge into one another in the tail by a commissure situated above the anus.

The internal segmentation of these animals as well as some other points in their anatomy leads me to the conclusion that here we have a group much more nearly related to the primitive intermediate forms between invertebrate and vertebrate than are either the more modern ancestors the annelids (whose “Bauch Mark” offers so strong an objection but can in its turn be easily derived from such forms of Nemerteans as is f. ex. Drepanophorus) or the original candidates for this honour: the ascidians.4

Within a few weeks I hope to prezent to our royal Society paper on this subject which you will permit me to send you.5

ADraft

2
Hubrecht probably sent his short paper ‘Vorläufige Resultate fortgesetzter Nemertinen-Untersuchungen’ (Preliminary results of continuing research on Nemerteans; Hubrecht 1879), but it has not been found in the Darwin Archive–CUL. Nemertea is the phylum of ribbon worms.
3
See Hubrecht 1879, p. 474.
4
Bauchmark: abdominal or ventral nervous cord (German). Drepanophorus is a genus of the class Enopla (armed nemerteans). Some researchers believed that annelids (segmented worms) were the ancestors of vertebrates while others, including CD, thought that ascidians (sea squirts) were the most likely ancestors (see, for example, Correspondence vol. 23, letter from Anton Dohrn, 7 February 1875, and letter to Anton Dohrn, [after 7 February 1875]). A major morphological difference between invertebrates and vertebrates is the location of the nerve cord, which is ventral in the former and dorsal in the latter.
5
Hubrecht’s paper ‘Zur Anatomie und Physiologie des nervensystems der Nemertinen’ (On the anatomy and physiology of the nervous system of nemerteans) was published in the Verhandelingen van de Koninklijke Akademie van Wetenschappen (Hubrecht 1880). No copy has been found in the Darwin Archive–CUL.

Please cite as “DCP-LETT-12339A,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-12339A