Informs CD that the "dishonest mollusks" were collected in May 1855 in Porto Santo. Describes some Madeira species. Though believing in "species" more and more, these may be "mere insular modifications".
Has done New Zealand flora calculations. Results support CD’s theory of necessity of crossing. Trees tend to have separate sexes.
Agassiz has informed him that the mice and rats of Mammoth Cave are American in type.
Alludes to CD’s doubt of the principle that "progress of life on the globe is parallel with the development in different tribes". Outlines his own ideas on the "unfolding of the type-idea" and its "parallelism with the law of development in the embryo".
Notes on the comparative rarity of intermediate forms between species, and the varying relationships those forms may have to one or both species between which they are intermediate.
His experience confirms CD’s view that some species and even some genera of Brachiopoda are consistently more variable than others, and that such variable forms are variable in all localities and at all periods. Similarly a species that shows a lack of variability does so at all points in time and space. Discusses the causes of variability. [See Natural selection, p. 106.]
Variability of certain features within insect 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.
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.
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.
Comments on transport of ducks to Jamaica by hurricanes,
fish feeding on seeds,
and sterility of birds in captivity.
Sends account of his successful experiments in feeding wheat seeds to minnows.
Suggests CD use the common origin of the French "chef" and the English "head" or "évêque" and "bishop" to illustrate the parallels between extinction and transitional forms in language and palaeontology [see Natural selection, p. 384].
Reports on wheat in the stomach of fish he caught.
JDH cites W. H. Harvey’s observations on Fucus and David Don’s on Juncus as examples of variations that are independent of climate. There are many such cases. Gives his working scheme for categorising variation.
Lists groups of insects absent from the Madeiran fauna.