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".

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.

Responds to CJFB’s criticisms of the Origin [see 2669].

If CD’s theory is a satisfactory explanation of the "principles of Homology, and of Embryology, and Rudimentary organs", the difficulty in imagining the transitions between classes of beings should not weigh against the understanding it provides such large classes of facts. Defends natural selection against criticism that it is not a vera causa. Comments on "Degeneracy", extinction of intermediate forms, and the effect of theory in natural history in opening up new fields of inquiry and giving rational instead of theological explanations of facts.