The year is established by the reference to the journal Mind; see n. 2, below.

The first issue of the journal Mind: a Quarterly Review of Psychology and Philosophy was published in January 1876. It contained Henry Sidgwick’s article ‘The theory of evolution and its application to practice’ (Sidgwick 1876). On p. 64, Sidgwick stated, ‘Moral sentiments, it is said, are impulses that tend to the maintenance of society; hence a tribe in which they were accidentally developed would tend to be victorious over other tribes in the struggle for existence.’ He then provided an account of how this view was incompatible with utilitarian ethics. In Descent 2d ed., pp. 130–1, CD had questioned how moral qualities could have arisen in a tribe when those who would be willing to risk their lives for others would perish in larger numbers than the others. He concluded that people would aid others at first out of self-interest, and that if continued over many generations this habit would be inherited, which would strengthen feelings of sympathy.

CD stayed with his brother, Erasmus Alvey Darwin, in London from 27 April until 3 May 1876 (CD’s ‘Journal’ (Appendix II)).

Leonard Darwin, an officer in the Royal Engineers, had been planning to come home on leave from his post at Malta in the second half of May; see letter to C. S. Wedgwood, 20 April 1876 and n. 8. In the event, he came to Down on 8 May 1876 (Emma Darwin’s diary (DAR 242)).