From George Busk 7 November 1869
32 Harley St
Nov 7 1869
My dear Darwin
The Polyzoan creatures you saw emerging from the cells of the main polypidom appear to me to be parasites— There can be no doubt that the principal growth as seen in Fig 1–5 &c is a species of Sertularia, though I am unable at the moment to give it a name if it have one.1
The vacated cells of this growth have been taken possession of by a minute species of ctenostomatous Polyzoa2—usually as it would seem or at any rate frequently in pairs as in Fig 3—but also in many cases singly—Fig 2–4— 6, 7. And it is remarkable that the parasite seems to be always affixed at about the same point in the empty sertularian cell (Fig 3 & 4). It is a curious, but as you well know not unexampled instance of “necessary parasitism”.3
Another instance though of a very different kind of this kind of parasitism among the polyzoa is that which I have described under the name of Bugula Ditrupæ which appears invariably to grow from the upper part of the shell of a species of Ditrupa in Madeira.4
Besides this “necessary” guest however—the sertularian is much infested with a Campanularia and a small sponge.5
Believe Me | Yours very truly | Geo Busk
Footnotes
Bibliography
Busk, George. 1852. Account of the Polyzoa, and Sertularian zoophytes, collected in the voyage of the Rattlesnake, on the coasts of Australia and the Louisiade Archipelago.In Narrative of the voyage of H. M. S. Rattlesnake commanded by the late Captain Owen Stanley during the years 1846–1850, including discoveries and surveys in New Guinea, the Louisiade Archipelago, etc., by John MacGillivray, vol 1. London: T. & W. Boone.
OED: The Oxford English dictionary. Being a corrected re-issue with an introduction, supplement and bibliography of a new English dictionary. Edited by James A. H. Murray, et al. 12 vols. and supplement. Oxford: Clarendon Press. 1970. A supplement to the Oxford English dictionary. 4 vols. Edited by R. W. Burchfield. Oxford: Clarendon Press. 1972–86. The Oxford English dictionary. 2d edition. 20 vols. Prepared by J. A. Simpson and E. S. C. Weiner. Oxford: Clarendon Press. 1989. Oxford English dictionary additional series. 3 vols. Edited by John Simpson et al. Oxford: Clarendon Press. 1993–7.
Summary
The Polyzoa CD saw emerging from cells of a particular growth appear to be parasites. The main growth is a species of Sertularia; the minute parasites take possession of vacated cells.
Letter details
- Letter no.
- DCP-LETT-6975
- From
- George Busk
- To
- Charles Robert Darwin
- Sent from
- London, Harley St, 32
- Source of text
- DAR 160: 382
- Physical description
- ALS 2pp
Please cite as
Darwin Correspondence Project, “Letter no. 6975,” accessed on 23 April 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-6975.xml
Also published in The Correspondence of Charles Darwin, vol. 17