To Charles Lyell   12 June 1867

Lyell’s letter has not been found. He had evidently written for further information or clarification following CD’s letter to him of 9 June [1867], concerning the variability of primroses and cowslips. In the tenth edition of Principles of geology, Lyell mentioned that CD had in the summer of 1867 completed experiments suggesting that the common oxlip was a hybrid between the primrose and the cowslip, and that the primrose and the cowslip were themselves distinct species (C. Lyell 1867–8, 2: 324). CD probably advised omitting mention of experiments suggesting that oxlips, cowslips, and primroses could be produced from the seed of a single plant (see n. 4, below).

In the fourth edition of Origin, CD omitted sentences giving the primrose and the cowslip as examples of doubtful species, and mentioning Karl Friedrich von Gärtner’s unsuccessful attempts to cross the primrose and the cowslip, that appeared in the first edition of Origin, pp. 49 and 247.

The Darwins visited London from 17 to 24 June 1867 (CD’s ‘Journal’ (Correspondence vol. 15, Appendix II)).

CD refers to William Herbert, and probably to John Stevens Henslow and Hewett Cottrell Watson. All three are cited in ‘Specific difference in Primula’, pp. 441–2, and Forms of flowers, pp. 60–1, as claiming to have produced cowslips, oxlips, and primroses from the seed of a single plant. In ‘Specific difference in Primula’, p. 441, CD wrote that ‘dimorphism not being formerly understood, the seed-bearing plants were in no instance protected from the visits of insects’.