Believes, with CD, that extinction may be an important factor in explaining plant distributions, but sees no reason why the several species of a genus must ever have had a common or continuous area. "Convince me of that, or show me any good grounds for it … and I think you would carry me a good way with you". It is just such people as AG that CD has to satisfy and convince.

Feels that the crossing of individuals is important in repressing variation and perhaps in perpetuating the species, but instances some plants in which it cannot, apparently, take place.

Representative species may complicate tabulation of varieties.

Questions for Mr Anderson about horse colouring in Norway.

Has been writing an "audacious little discussion" to show that "organic beings are not perfect, only perfect enough to struggle with their competitors".

Finds CD’s results [of his survey of well-marked varieties from A. P. and Alphonse de Candolle’s Prodromus systematis naturalis regni vegetabilis (1824–73)] "very curious and suggestive". Thinks the Labiatae will present an obstacle to him as it is a very large and distinct order with well-defined species and genera. Would like to see him tackle more volumes of Candolle’s Prodromus, as his case can only be established by evidence from mundane plants. CD should beware of generalising from local species variability. A comparison of C. C. Babington’s and G. Bentham’s [British] Floras [Babington Manual of British botany (1843, 4th ed., 1856); Bentham Handbook of British flora (1858)] would be invaluable. Suggests CD write to Ferdinand Müller and Charles Moore in Australia. Moisture favouring extension of species is important for CD’s view.

Hybrid varieties of pheasant and common fowl. Reply to CD queries.

Writes of the extension to Down House.

Is glad WED is in the sixth [form]. Discusses WED’s intention to become a barrister.

Will be grateful for facts from Mr Linton on numbers of eggs from goldfinch–canary crosses.

CD finds Alphonse de Candolle very useful, though JDH has low opinion.

CD argues for accidental introductions explaining some odd distributions, e.g., New Zealand vs Australian plants.

CD’s method.

Diverging affinities in isolated genera.

Sexes of algae.

Will attend to any subject in Jamaica about which CD wants information.

Crithagra brasiliensis and canary refused to pair.

A collection of Jamaican land Mollusca will be presented to the British Museum.

Hurricanes are a considerable influence on diffusion of birds and insects.

Enumerates fossil mammals known in Secondary strata.

Lack of angiosperm plants in rocks older than Chalk is no reason to anticipate rarity of warm-blooded quadrupeds.

CD will advise W. F. Daniell on collecting.

Asks THH question on flow of glaciers after ice has been fractured and fragmented.

CD had to leave Royal Society lecture [joint paper by THH and J. Tyndall, "On the structure and motions of glaciers", Philos. Trans. R. Soc. Lond. 147 (1857): 327–46] before the end because of headache.

CD will advise Daniell not to apply for Royal Society grant.

CD’s experiment: fish fed seeds, which germinated when voided.

Sends specimens of Tortrix, which illustrate the extraordinary variation of markings in two or three species. In every family of Lepidoptera there seem to be species extremely prone to vary and in some localities they vary more than in others.

CD is "as ignorant of mechanics as a pig", but glaciers have interested him greatly. Hopes to hear that JT’s experiments with ice will explain the freezing together of ice below the freezing point.

The variations of Peronea caused A. H. Haworth and J. F. Stephens to create 30 or 40 species based on colour and markings. HD was first to be convinced these would be reduced to two.

Discusses species that closely resemble one another;

cites species that differ in variation in different localities;

in some double-brooded species the broods differ markedly in size and colour.

Encloses his list of varieties of Peronea.

Discusses the ranges of alpine species in U. S. and considers the possible migration routes of such species from Europe.

Lists those U. S. genera which he considers protean and describes the U. S. character of some genera which are protean in Europe.

Describes how he distinguishes introduced and aboriginal stocks of the same species.

The species of Mollusca at Mauritius are almost all different from those of surrounding islands, which confirms the belief that the islands were elevated from the ocean rather than separated from the continent by volcanic action.

HCW is trying to define what CD means by "variable" genera.