The date is based on the suggestion in the text that Brent may recently have read CD’s discussion of the possible relation of the behaviour of ducks to the dispersal of plants and animals in Origin, pp. 383–8. See n. 2, below.

Brent was a noted pigeon-fancier and breeder of domestic poultry. He had assisted CD in his investigations of pigeons and fowls since 1856 (see Correspondence vols. 6 and 7). Brent’s remarks suggest that he was commenting on CD’s view that young molluscs or floating plants could become attached to ducks’ feet while they were swimming and thus be transported elsewhere. CD had been actively investigating means of geographical dispersal since 1855 (see Correspondence vols. 5 and 6). The results of his study are summarised in Origin, pp. 383–410, where an experimental trial on young molluscs clinging to ducks’ feet is mentioned: ‘I suspended a duck’s feet, which might represent those of a bird sleeping in a natural pond, in an aquarium’ (Origin, p. 385). The experiments, carried out in 1857 and 1859, are recorded in CD’s Experimental book, pp. 22–3 (DAR 157a).

The number of CD’s portfolio of notes on the means of dispersal of plants and animals.