To George Busk 2 September [1871]1
Sept 2d
Busk.
I am going to beg a great favour of you. I mentioned to you that Nitsche quotes your conclusion that the avicularium is a modified zooïd.2 Now I want to know whether you infer this from analogous position manner of development & other general reasons, or whether, any gradations now exist between the 2 states. It is in relation to gradation that I make these enquiries, & I just want to say either that no gradation is known to exist between an avicularium & a zooid, or to give a few words explaining the nature of any such gradation. Perhaps you have discussed this subject in your paper. Transact of Micro Soc. 1847 to which you refer in your Catalogu..— e3If so can you lend me for short time a copy?—
I remember Some considerable time ago thinking how odd it was that allied Polyzoa, should possess avicularia or vibracula; & I idly speculated whether the movable lower jaw of the former could have been modified into a vibraculum.4 Therefore I was delighted the other day by reading your discussion. (p 104 Catalogue) from which I infer that these organs (which in these extreme states of development differ most widely appearance), graduate into each other so completely that in Lepralia it is almost doubtful which term ought to be used.— I shd. much like to quote you on this head.5 Does the pointed end of the moveable mandible ever project a little beyond the fixed beak; & in such cases does it assume to some extent the shape of a vibraculum; for this wd be the first step towards conversion? again when there does exist what must be called a true vibraculum, is there ever any trace or rudiment at the base of upper beak for this would form a last stages of conversion? Does what I have here said at all express your belief? I shd be greatly obliged for a little information. I am preparing a new Edit of the Origin, in which I shall insert in [answer] of Mivart’s book— a new chapter, chiefly on the subject of gradation, & first appearance of organs,6
Pray forgive me, if you can, pestering letters | of this nature
Footnotes
Bibliography
Busk, George. 1847. Observations on the Shepherd’s Purse coralline of Ellis (Notamia bursaria, Fleming). Transactions of the Microscopical Society of London 2 (1849): 110–21.
Busk, George. 1852–4. Catalogue of marine Polyzoa in the collection of the British Museum. 2 vols. London: printed by order of the Trustees.
Busk, George. 1853. Remarks on the structure and function of the avicularian and vibracular organs of the Polyzoa; and on their value as diagnostic characters in the classification of those creatures. [Read 23 November 1853.] Transactions of the Microscopical Society of London n.s. 2 (1854): 26–33.
Nitsche, Hinrich. 1871. On some interesting points concerning the mode of reproduction of the Bryozoa. Quarterly Journal of Microscopical Science n.s. 11: 155–62.
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.
Summary
Is preparing a new edition of Origin [6th ed. (1872)] and asks GB for information on the gradations between the vibracula and avicularia of the Polyzoa and on what he bases his opinion concerning the homology of the avicularium with the zooid.
Letter details
- Letter no.
- DCP-LETT-7921
- From
- Charles Robert Darwin
- To
- George Busk
- Sent from
- Down
- Source of text
- DAR 96: 88
- Physical description
- ADraft 2pp
Please cite as
Darwin Correspondence Project, “Letter no. 7921,” accessed on 28 March 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-7921.xml
Also published in The Correspondence of Charles Darwin, vol. 19