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

ADraft

1
The year is established by the relationship between this letter and the letter from George Busk, 10 September 1871.
2
No earlier letter to Busk from CD about Hinrich Nitsche has been found; CD was last in London in mid-July 1871 (letter from G. H. Darwin, [17 July 1871], n. 1). Nitsche cited Busk 1853 in Nitsche 1871, p. 162. CD cites both Busk and Nitsche in Origin 6th ed., p. 193. For more on avicularia, see the letter to Alexander Agassiz, 1 June [1871], n. 3.
3
Busk referred to his paper in the Transactions of the Microscopical Society of London (Busk 1847) in his Catalogue of marine Polyzoa in the collection of the British Museum (Busk 1852–4, 2: 104).
4
For more on vibracula, see the letter to Alexander Agassiz, 1 June [1871], n. 3. The former class Polyzoa included the present phyla Ectoprocta (bryozoans) and Endoprocta.
5
The quotation in Origin 6th ed., p. 194, is from Busk’s catalogue of Cheilostomata (Busk 1852–4, 2: 104). The genus Lepralia is now considered unrecognisable as no type species was given (for more on synonymy, see Philip Bock, Recent and fossil Bryozoa, bryozoa.net/library/harmernotes/lepralia.html (accessed 29 October 2010)). For more on the Cheilostomata, see Hayward and Ryland 1998–9). Long, thin mandibles that extend well beyond the palate of the avicularium are now referred to as setiform and are considered as transitional to the bristles of vibracula.
6
CD inserted a chapter titled ‘Miscellaneous objections to the theory of natural selection’ into Origin 6th ed., responding to, in particular, the criticisms of St George Jackson Mivart in his Genesis of species (Mivart 1871a).

Manuscript Alterations and Comments

0.1 Sept 2d] added pencil
0.2 Busk] added pencil
1.1 great] interl
1.1 mentioned] after del ‘sp’
1.1 to you] interl
1.3 analogous] after del ‘ge’
1.3 manner of development] interl
1.4 any] after del ‘things that’
1.4 It is … gradation. 1.7] added
1.5 either] inter
1.8 to which … Catalogue.] interl
1.9 copy] after del ‘report’; before del ‘of your paper’
2.1 I remember] transposed from after ‘ago’
2.1 thinking] after del ‘specul’
2.2 or] over ‘&’
2.2 I] after del ‘as’, above del ‘an’
2.2 idly] ‘y’ over ‘e’
2.2 speculated] above del ‘speculated I wondered’; deleted ‘speculated’ has ‘ed’ over ‘ion’
2.3 a vibraculum] above del ‘the latter.’
2.5 (which] parenthesis over comma
2.6 most widely] above del ‘so many’; below del illeg
2.6 appearance)] after del ‘greatly in’
2.6 so completely] interl
2.6 that] after del ‘, so’
2.7 ought to] above del ‘shd’
2.7 I shd.] after del ‘Does the movable’
2.8 pointed] after del ‘move’
2.10 a vibraculum] ‘a’ inserted before del ‘the’
2.10 step towards] above del ‘step of’
2.10 again] after ‘And’ del pencil
2.11 there does exist] interl
2.11 what … called] interl above del ‘a’
2.11 a true] interl pencil
2.11 vibraculum,] comma after del ‘does exist’
2.12 at the base] interl; transposed pencil from after ‘beak’
2.12 upper] pencil; after del pencil ‘a’, above del ‘the’
2.12 for this] pencil; below del pencil ‘which’
2.12 form a] ‘a’ pencil, above del pencil ‘one of the’
2.13 have] interl
2.13 said] above del ‘say’
2.13 belief.] above del ‘views’
2.13 greatly] above del ‘utterly’
2.15 in [answer] … book— 2.16] transposed pencil from after ‘organs,’

Please cite as “DCP-LETT-7921,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-7921