Grateful for Siebold’s wonderful facts [C. T. E. von Siebold, On a true parthenogenesis in moths and bees (1856), trans. by W. S. Dallas (1857)].
Vitality of spermatozoa.
Hybridisation of bees. Bees are in one respect his greatest theoretical difficulty.
CD still convinced about the relation of cement receptacles and ovarian tubes [in Crustacea].
Birth of C. W. Darwin.