Has heard CD is much interested in questions relating to varieties and species. Mentions a case of a seminal variety of Colletia spinosa, described by John Lindley, which appears identical with another wild species of Colletia from S. America. Hopes CD will one day "enlighten us very much" on "the laws of species". There are many different views on the limits of species; M. F. Dunal made 50 species of Solanum which George Bentham considers are all varieties of S. nigrum.

Is interested by what CD tells him about his researches and speculations on species, variation, and distribution. Hopes he will not give up the idea of publishing his views. Advises CD on need for caution and candour. Raises some difficulties with "specific centre" theory of distribution.

CD writes on geographical distribution – "a grand game of chess with the world for a board".

Gives his hypothetical explanation why zoology of Cape [of Good Hope] is not so peculiar as its botany: it was once a group of islands – later united.

Tries hard to set forth the difficulties of his [species] theory.

Tells CJFB in confidence of his theory of the glacial epoch and its effect on plant distribution, such as identical species being found on summits of mountains in the tropics. Invites him to attack his "doctrine".

Adds comments to a list of Cape of Good Hope plants which are also European and gives some additions to the list [see Natural selection, p. 552].

On geographical dispersal of plants. Would be interested in CJFB’s views on representative species and on his hypothesis of a mundane cold period, which CD cannot prove geologically, but thinks, if it explains many facts of geographical distribution, may be admitted as probable. Hooker and Alphonse de Candolle do not agree with him.

No summary available.