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".

Referring to a correspondent who had written about Pelargonium plants whose leaves had become regularly edged with white, CD reports that nearly all the young leaves of box-trees he had planted have become symmetrically tipped with white. Though these facts seem trivial, CD believes the first appearance of any peculiarity which tends to become hereditary deserves being recorded.

Asks whether salt and carbonate of lime (in the form of seashells) would act upon each other if slightly moistened and left in great quantities together. The question occurs from CD’s having found in Peru a great bed of recent shells that were mixed with salt, decayed and corroded "in a singular manner". Mentions, as relevant to the value of seashells as manure, that they are dissolved more rapidly by water than any other form of carbonate of lime.

Writes about canal shares EAD holds as trustee.

CD and Emma request transfer of some shares to E. A. Darwin.

Says AM’s letters on glacial action not publishable since they do not give facts. Suggests readings on the subject of glaciers. Expresses doubts about AM’s theory that Scandinavian glaciers brought the boulders he was studying.

Discusses a specimen of Mexican obsidian with an unusual laminated structure.

Asks whether LJ can throw light on this subject: "What are the checks and what the periods of life by which the increase of any given species is limited?" CD has been driven to conclude that species are mutable; allied species are co-descendants from common stocks.

Has been discussing wills and other legal matters with his father.

Discusses the connection between climate and vegetation. Believes that an equable climate is unfavourable to increase of species either by importation or modification of existing forms; illustrates his view with reference to particular floras. Hopes to acquire facts to support CD’s idea that isolation is important in producing new forms. Considers the floras of islands some of which do have distinctive species but others of which do not. Agrees that the wide ranges of cryptogams are a consequence of their means of dispersal. Asks for references to works on original creation and species mutability in order to get the best notions of "the (mad) theories of some men from Lamarck’s twaddle upwards".

Has never heard of species of same genus [of parasites] being found on both birds and mammals, or different genera and species being found on animals in the domestic and wild states. Implications of this for relationship of aperea and guinea-pig.

Believes JDF’s discoveries in the structure of glacier ice will explain the structure of many volcanic masses. Will JDF’s views throw any light on the primary laminated rocks?

Discusses HD’s information that same species of birds at remote stations have identical parasites. Urges him to investigate N. American land-bird parasites.

Is deeply interested in everything connected with geographical distribution, and the differences between species and varieties.

Sends notes on Infusoria for Ehrenberg.

Comments on distribution of species in natural orders that have local distributions. Intermediate forms between species of Lycopodium.

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.

Mexican specimen of laminated obsidian.

Comments on Forbes’s publication comparing lava streams and glaciers. Mentions ice-action theories of a young German.

Differences in variability of species within a single genus. Further observations on Lycopodium.

Interested in Humboldt’s river with different floras on opposite banks, and other unexplained cases of very local distributions.

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

Considers the transmutation of corn is well worth investigation ‘even if it should prove to be only a history of error’.

On checks to increase of species and the observations which led him to regard species as mutable in form. Would welcome "at some future time" LJ’s criticism of the "sketch" of his conclusions.