From George Busk 10 September 1871
Taynuilt | Argyleshire
Sept 10th 1871
My dear Darwin
Your letter has re⟨ac⟩he⟨d⟩ me in this rem⟨o⟩te latitude or should have had an earlier reply.1
My notion with respect to the relationship between the vibracular & avicularian organs & the ordinary cells & their contents of the Polyzoon is conceived somehow in this sense—that the mandible or vibra⟨cu⟩lum as the case may be represents the moveable lip of the cheilostomatous cell-mouth and consequently that the av⟨i⟩cularian cell might be ⟨re⟩garded as homologous with that inhabited by the nutritive & reproductive zooid.2
I have never however noticed any like a transition from the zooid itself into an avicularian or vibracular organ, although I conceive it is quite probable that the contents of the avicularian cell—for instance, the brushlike organ, seen in some cases &c—may be homologous with the ord⟨in⟩ar⟨y⟩ zooid.3
As regards a transitio⟨n⟩ or gradation between ⟨ ⟩ avicularia & vibra⟨cula⟩ I could were I at home furnish you with several instances, whose names I cannot at the moment recall—whilst the ordinary vibraculum maybe represented thus
Another will p⟨r⟩esent this form
and sometimes the beak is still more produced.4
With respect to the opposite or fixe⟨d⟩ beak—such a thing ⟨is b⟩y no means universally ⟨pre⟩sent even in well marked ⟨vibr⟩acula especially when ⟨the m⟩andible is rounded, so
or |
that its presence or absence is not of high importance. In the larger & more perfect vibracula as in Scrupocellaria and Caberea5—the seta is received in a deep groove but suc⟨h a⟩ groove is not essential in all cases & in many instances, more especially in the Lepraliæ it would be impossible, when the moveable member is removed, as in fossil s⟨p⟩ecies to determine, in all cases, from the appearance of the o⟨rgan⟩ whether the organ had been furnished with a vibracul⟨um⟩ or a true mandible.—6
I think but am not sure that Smitt has made some remarks with regard to these organs pertinent to your queries— when I get home I will see & send you his pape⟨r⟩—7
Am Yours very truly | Geo Busk
CD annotations
Footnotes
Bibliography
Busk, George. 1852–4. Catalogue of marine Polyzoa in the collection of the British Museum. 2 vols. London: printed by order of the Trustees.
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
Replies to CD’s queries about the homologies of the avicularian and vibracular organs of Polyzoa and gives examples of gradations between the two.
Letter details
- Letter no.
- DCP-LETT-7930
- From
- George Busk
- To
- Charles Robert Darwin
- Sent from
- Taynuilt
- Source of text
- DAR 160: 383
- Physical description
- ALS 5pp damaged †
Please cite as
Darwin Correspondence Project, “Letter no. 7930,” accessed on 23 April 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-7930.xml
Also published in The Correspondence of Charles Darwin, vol. 19