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Darwin Correspondence Project

From F. M. Balfour   [20 March – 14 April 1875]1

Stazione Zoologica | Napoli

Dear Mr. Darwin

I have given your message to Claus and also the specimens.2

The only suggestion which he can make about the one with a central disc from wh. rays pass out, is that it may be the statoblast of some fresh water Polyzoon.3 He does not however feel at all confident about it.

He thinks that the other organism, consisting of a sculptured test open at one end, is the shell of some Rhizopod probably one of the Arcellidae—4 He refers for figures to an article of Schultze’s in the tenth volume of the Archiv. fùr Micro. Anatomie.5

Professor Claus also begged me to send you his kind remembrances; & to tell you that he hopes soon to send you a copy of a paper upon ‘the Anatomy & development of Argulus foliaceus’, & also of a work on the ‘Phylogeny of the Crustaceans’.6

I was unwell for nearly a week after my arrival here, & unable to go to the station or I would have written you earlier about these organisms.

I remain | Yours very truly | F. M. Balfour

CD annotations

Top of letter: ‘(Keep)’ pencil


The date range is established by the reference to Carl Friedrich Claus, who visited the Naples zoological station from 20 March until 14 April 1875 (Groeben 1982, p. 104 n. 18).
The message from CD and the specimens have not been identified.
Polyzoa, a former class of compound animals, is roughly equivalent to the modern phylum Ectoprocta (bryozoans). Statoblast was the name coined by George James Allman to describe the reproductive gemmae of some Polyzoa, which were surrounded by an opaque investment (Allman 1855, p. 118).
Arcellidae is a family of rhizopods in the class Lobosa (amoebas).
Franz Eilhard Schulze’s two-part paper ‘Rhizopodenstudien’ appeared in the Archiv für mikroskopische Anatomie 10 (1874): 328–50, 377–400. Figures appeared in tables 26 and 27, some of which showed the rough ovoid test or shell with encrusted grains of sand and an opening at one end (tab. 26, figs. 8–10).
CD’s copy of Claus’s paper, ‘Ueber die Entwickelung, Organisation und systematische Stellung der Arguliden’ (On the development, organisation, and systematic place of the Argulidae; Claus 1875), is in the Darwin Pamphlet Collection–CUL. His copy of Claus’s book, Untersuchungen zur Erforschung der genealogischen Grundlage des Crustaceen-Systems (Research towards the discovery of the genealogical foundation of the Crustacea; Claus 1876), is in the Darwin Library–Down. Argulus foliaceus (the carp louse) is a species in the parasitic crustacean family Argulidae (fish lice).


Allman, George James. 1855. On the signification of the so-called ova of the Hippocrepian Polyzoa, and on the development of the proper embryo in these animals. Report of the 25th meeting of the British Association for the Advancement of Science (1855), Transactions of the sections, pp. 118–19.

Claus, Carl Friedrich. 1875. Ueber die Entwickelung, Organisation und systematische Stellung der Arguliden. Zeitschrift für wissenschaftliche Zoologie 25: 217–84.

Groeben, Christiane, ed. 1982. Charles Darwin 1809–1882, Anton Dohrn 1840–1909: correspondence. Naples: Macchiaroli.


Gives Carl Claus’s identifications of the organisms sent by CD.

Letter details

Letter no.
Francis Maitland Balfour
Charles Robert Darwin
Sent from
Naples Zoological Station
Source of text
DAR 58.1: 149
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 9203,” accessed on 24 July 2021,

Also published in The Correspondence of Charles Darwin, vol. 23