Encloses letter from Ehrenberg [762], who wants information on deep-sea soundings from JDH’s voyage, and on isolated islands.

Encloses Ehrenberg letter, Galapagos seaweed, and specimens of Conferva.

H. Denny would like specimens of Antarctic Pediculi.

Encloses pamphlet from Ehrenberg who asks about deep-sea soundings from JDH’s voyage.

Acknowledges note and parcel for Ehrenberg.

Considers why different areas have different numbers of species. Gives an example opposing JDH’s view that paucity of species results from vicissitudes of climate. CD has concluded that species are most numerous in areas that have most often been divided, isolated from, and then reunited with, other areas. Cannot give detailed reasons but believes that "isolation is the chief concomitant or cause of the appearance of new forms".

Writes about canal shares EAD holds as trustee.

Origin of Antarctic brash ice.

Further on case of Lycopodium: does JDH know any genera of plants whose species are variable in one continent but not in another? Discussion on variations between floras as regards species richness, and factors affecting geographical distribution. On species, CD expects "that I shall be able to show even to sound naturalists that there are two sides to the question of the immutability of species; – that facts can be viewed and grouped under the notion of allied species having descended from common stocks". Mentions books and papers for and against species mutability. CD believes past absurd ideas arose from no one’s having approached subject on side of variation under domestication.

Would like to see Clarke’s paper

and would welcome visit from JDH.

Would like JDH to visit. Regrets he will not be fit to visit JDH.

Sends thanks for money.

Comments on treatment prescribed by his father.

Encloses notes by John Higgins with investment advice. Discusses advisability of investing in farmland in Lincolnshire. Cites advice of Sir John Lubbock concerning purchase of land.

Returns notes on mule yaks [see Natural selection, p. 438]

and sends queries on silkworms.

A bed is ready any time HF will come.

Instructions for JDH’s trip to Down.

Change in train times.

Asks WBC if he will examine a specimen of calcareous rock.

[Notes on conversations with J. D. Hooker.] Geographical distribution; diffusion and distribution of species. Island and mountain floras; means of migration (high-roads, icebergs).

Thanks for botanico-geographical remarks. CD greatly appreciates JDH’s valuable generalisations.

Questions on JDH’s sketch comparing floras of Australia, New Zealand, and western S. America; wishes to know botanical relations between other southern islands. Botanico-geographical discussions and comments on books sent by JDH.

Arranges a time for visiting HF.

Sends specimens of a Tertiary sandstone from Tierra del Fuego in which there are leaves; CD thought they were beech. What is JDH’s opinion?

Asks whether JDH can make sense of a note on silicified wood.

Has read Vestiges [of creation (1844)]; "his geology strikes me as bad, & his zoology far worse".

Would like to see lists [of plants] from Society and Sandwich Islands.

Doubts JDH’s information regarding imagination of mother affecting offspring.

Would like copy of "Galapagos flora" when published ["Plants of the Galapagos Archipelago", Trans. Linn. Soc. Lond. 20 (1851): 163–233].

Will keep JDH’s Pacific island notes till his return.

Mainly news of the three children.

CD sends queries on chemical composition of various Beagle mineral specimens.