Summary

Thomas Bell thinks John Lindley superior for Royal Society Medal. CD agrees, but demurs at Medal going to same branch of science two years in succession.

Perplexed about Albany Hancock’s qualifications compared with J. O. Westwood’s.

Death of H. De la Beche.

Summary

Encloses two sets of notes [see 1761 and 1762]. EB believes that as a general rule species do not inter-mix in nature whereas varieties, descendants of a common stock, do. Origin of varieties. Geographically separated species are sometimes obviously distinct and sometimes apparently identical. EB does not believe that species or races of independent origin need necessarily differ. Local distribution of species of black cockatoo contrasts with the widespread white cockatoo. The occurrence of distinct but related species in different regions of a zoological province, preserved because of geographical barriers. Instances of interspecific hybrids and intraspecific sterility. Local varieties of species. Varieties are subdivisions of the main branches of the tree of organisms, dividing irregularly but remaining independent of the twigs from another branch.

Summary

Reports on his experiments on action of sea-water on seeds and the bearing of his investigations on the theory of centres of creation and Edward Forbes’s theory of continental extensions to account for distribution of organic forms. CD’s experiments confirm germination powers were retained after 42 days’ immersion by seven out of eight kinds of seeds.

Summary

Comments on the ease with which different species of Felis can be tamed.

Asian species of wild cattle.

Variation in colour of jackals.

Discusses the difficulties of differentiating between varieties and species. EB recommends Herman Schlegel’s definition of species [in Essay on the physiognomy of serpents, trans. T. S. Traill (1843)]. Problems of defining species of wolves and squirrels. Pigeons and doves afford an illustration of "clusters of species, varieties, or races". Various pigeons have local species in different parts of India and Burma, some of which interbreed where their ranges cross; as do the local species of Coracias [see Natural selection, p. 259].

[CD’s notes are an abstract of this memorandum.]

Summary

Notes on Lyell’s Principles, vol. 2.

EB does not believe in connecting links between genera; there is no tendency to gradation between groups of animals.

Does not believe shortage of food can directly produce any heritable effect on size.

Comments on significance of variations discussed by Lyell. Variation in dentition and coloration.

Behaviour of elephants and monkeys.

When varieties are crossed EB considers that the form of the offspring, whether intermediate or like one or other of the parents, depends upon how nearly related the parents are.

Thinks that in the struggle for existence hybrids, and varieties generally, must be expected to give way to the "beautiful & minute adaptation" of the pure types.

Colours of Indian birds.

Vitality of seeds.

Variation among palms.

Fauna of Malaysia and New Zealand. Ranges of bird species.

[Memorandum originally enclosed with 1760.]