The date is established by the reference to the payment for lectures (see n. 2, below).

George Murray Humphry was professor of human anatomy at Cambridge; Alfred Newton was professor of zoology and comparative anatomy; Charles Cardale Babington was professor of botany. CD recorded a payment to Francis of £7 7s. (i.e. 7 guineas) on 8 May 1869 in his Classed account books (Down House MS).

Francis was working towards a degree in natural sciences at Cambridge, following which he planned to study medicine at St George’s Hospital, London (ODNB). According to university regulations at the time, candidates obtaining honours in the mathematical or classical tripos could be admitted to the examination in natural sciences in the following Michaelmas (autumn) term. Francis sat examinations for the mathematical tripos in January 1870 and for the natural sciences tripos in December 1870 (Cambridge University calendar 1870, 1871).

Vermiform appendage: appendix. In Descent 1: 27–8, in a discussion of rudimentary organs, CD noted that small hard bodies such as seeds could cause inflammation in the vermiform appendage and even result in death.