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Darwin Correspondence Project

To P. B. Mason   31 March [1871]

Down. | Beckenham | Kent. S.E.

March 31st

My dear Sir

I am very much obliged for your prompt information.1 In the next Edit. of my Book, I will certainly quote on your authority the statement about the hair on the back; it is quite new to me.—2 No doubt the proportion of hairy backs out of even 100 children at the Hospital in Ormond St, would add immensely to the value of the statement; but I can hardly hope that you could persuade any medical man to take so much trouble.

Your suggestion is very good about the size of male infants, & my blindness equally bad.3 I suppose that I shall find in Dr. Duncan’s paper in Transact. of R. Socy. of Edinburgh, the actual weights of male & female infants; as I imagine he could not have overlooked this in giving the weights of infants from mothers of different ages.—4 Nevertheless I can hardly think that your solution, though it certainly ought not to be neglected, can apply to the whole case, as male infants for some years after birth die at a greater rate than female infants.

With cordial thanks | Pray believe me | Yours sincerely | Ch. Darwin


In Descent 2d ed., pp. 19–20, CD recounted Mason’s information on children with hairy backs, noting that he had received the information from ‘a surgeon to a hospital for children’ (ibid., p. 20).
Mason had suggested that the larger size of male infants was a factor influencing the number of male stillbirths (see letter from P. B. Mason, 29 March 1871 and n. 3).
CD refers to James Matthews Duncan (see letter from P. B. Mason, 29 March 1871 and n. 4). CD had referred to Duncan 1866 in Descent 1: 174. The paper did not, however, give any statistics regarding the sex and weight of children.


Descent 2d ed.: The descent of man, and selection in relation to sex. By Charles Darwin. 2d edition. London: John Murray. 1874.

Descent: The descent of man, and selection in relation to sex. By Charles Darwin. 2 vols. London: John Murray. 1871.


Thanks him for information on children with hairy backs.

Discusses paper by J. M. Duncan on the relative weights of male and female infants.

Letter details

Letter no.
Charles Robert Darwin
Philip Brookes Mason
Sent from
MR 31 71
Source of text
American Philosophical Society (Mss.B.D25.391)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 7647,” accessed on 27 October 2021,

Also published in The Correspondence of Charles Darwin, vol. 19