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Darwin Correspondence Project

From George Busk   16 October 1871

32 Harley St

Oct 16 1871

My dear Darwin.

Having at length reached home I return your M.S. which appears to me to convey a perfectly correct account of the defensive organ of the Polyzoa—1 I have made one or two verbal alterations and do not at all like the use of the word Corallines for these creatures—2

I have looked into Smitts papers but have been unable to find anything bearing more directly on the point of homology than the following “—Organa illa secundaria coloniæ (setæ—ooæcia—avicularia et vibracularia soboles) quae gemmificatione secundaria sæpissime supra zooæcia oriuntur, Quamvis etiam zooæciorum modo gemmificatione primaria oriri possint. Immo etiam modificationes ejusdem typi atque zooæciorum videri possint” and in another place he describes the vibracularia & Avicularia) as arising by gemmation & fission, & as altogether corresponding with the polype-cells in other species—”— But this is perhaps sufficient to indicate his assent to their homologous nature.3

In order to show you what I look upon as transitions between vibracula & avicularia I enclose One or two figures—one of a species collected by yourself in the Falkland Islands. in which this quasi transition appears to be clearly manifested.4

Hoping I have not inconvenienced you by keeping the paper so long

I am | Yours very truly | Geo Busk


CD probably sent Busk a draft of the section relating to marine Polyzoa that he added to Origin 6th ed., pp. 192–4. The former class Polyzoa contained the present-day phyla Ectoprocta (bryozoans) and Endoprocta. See letter to George Busk, 13 September [1871].
The term coralline once applied to the seaweed Corallina and plant-like compound animals like the Polyzoa; it is no longer used in zoology (OED).
Busk refers to Fredrik Adam Smitt. See letter from George Busk, 10 September 1871 and n. 7. The Latin passage is from Smitt 1867, p. 468, and may be translated: ‘Those secondary organs of the colony (setae—ooecia—avicularian and vibracularian shoots) that most often arise beyond the zooecia by secondary gemmation can however also arise simply by primary gemmation of the zooaecia. Indeed, modifications of the same type can be seen even in zooaecia.’ In Origin 6th ed., p. 193, CD described the lid of a zooid as homologous with the movable mandible of the avicularium. For more on Smitt’s description of zooid formation and colonial growth in bryozoans, see Schopf and Bassett 1973.
The enclosures have not been found. For the specimens that CD gathered in the Falkland Islands and elsewhere, see R. D. Keynes ed. 2000; on his investigation of the ‘corallines’ on and shortly after the Beagle voyage, see ibid., pp. xiii–xvii.


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.

Origin 6th ed.: The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 6th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1872.

Smitt, Fredrik Adam. 1867. Bryozoa marina in regionibus arcticis et borealibus viventia recensuit. Öfversigt af Kongliga Vetenskaps-akademiens Förhandlingar 24: 443–87.


Returns CD’s MS [for Origin 6th ed.] on the defensive organs of the Polyzoa, with his comments.

Letter details

Letter no.
George Busk
Charles Robert Darwin
Sent from
London, Harley St, 32
Source of text
DAR 160: 384
Physical description
ALS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 8012,” accessed on 28 March 2023,

Also published in The Correspondence of Charles Darwin, vol. 19