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Darwin Correspondence Project

From Francis Darwin   [before 4 January 1870]1

University “Pitt” Club

My dear Father

I spoke to Humphrey about the os coxygis, he said that he had never heard of there being more bones in ♀; but as such small bones are very apt to get lost in macerating &c, it is impossible to judge by comparing ♂ & ♀ skeletons.2 There are 3 ♀ subjects in the dissecting room & he says that he will get the point looked at   He says he has read some where that there are more segments in the coxyx of the embryo than there are afterwards but he can not give his authority. It will be rather hard on the female sex if what Haeckel says it true.3

Your affec son | F Darwin

I have been coaching with another man while Stuart is measling, & he says I have a chance of the wranglers but I don’t think I have4


The date is established by the starting date of the final examination for the mathematical tripos, the first Tuesday after 30 December, which was 4 January in 1870 (Cambridge University calendar 1870, p. 26; see n. 4, below).
No letter from CD requesting Francis to put a question to George Murray Humphry has been found. CD evidently asked about the number of bones in the coccyx (os coccyx or tailbone) in men and women.
In Natürliche Schöpfungsgeschichte (Haeckel 1868b, p. 235), Ernst Haeckel had noted that in human females the vestigial tail, composed of three to five small vertebrae, was usually one vertebra longer than in males.
James Stuart had been third wrangler at Cambridge in 1866, that is, he was third in the final examination for the mathematical tripos (Cambridge University calendar 1866). Stuart was coaching Francis for the same examination; his replacement while he was ill with measles has not been identified. Francis was ranked fifth in junior optimes (third-class honours) for the examination in 1870 (Cambridge University calendar 1870).


Humphrey does not think more bones in female os coccyx than in male. Because of maceration it is impossible to compare male and female skeletons. Has another coach while Stuart ill.

Letter details

Letter no.
Francis Darwin
Charles Robert Darwin
Sent from
Source of text
DAR 274.1: 18
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 6520F,” accessed on 18 May 2022,

Also published in The Correspondence of Charles Darwin, vol. 24 (Supplement)