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Darwin Correspondence Project

To Frederick Howlett   21 September [1878]

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

Sept. 21st

Dear Sir

I am sorry to say that I cannot throw a gleam of the obscurest light on your difficult problem, which has sometimes occurred to me as a most perplexing one.— But in fact we do not know enough of the meaning of the shape or size of the blood corpuscles or of scarcely any histological characters, for anyone to speculate on the subject.1

I shd. doubt about the peculiar shape of the corpuscles in the Camelidæ being due to inheritance from a remote progenitor; & most of the points which you specify as being alike in camels & ostriches could be accounted for, as it appears to me, more probably by adaption to similar conditions, rather than to inheritance from a, common ancestor, extremely remote in time.2

Thanking you for your very courteous expressions | I remain, Dear Sir | yours faithfully | Ch. Darwin


Howlett’s letter to CD has not been found. Howlett, a clergyman, was interested in microscopy.
The red blood cells of camelids and ostriches are oval; the shape is unusual for mammals, but not for birds (see Gulliver 1875).


Gulliver, George. 1875. Observations on the sizes and shapes of the red corpuscles of the blood of vertebrates, with drawings of them to a uniform scale, and extended and revised tables of measurements. [Read 15 June 1875.] Proceedings of the Zoological Society of London (1875): 474–95.


Cannot explain the peculiarities of the blood corpuscles of the Camelidae; maybe similarity between camels and ostriches arises from adaptation rather than common ancestry.

Letter details

Letter no.
Charles Robert Darwin
Frederick Howlett
SP 21 78
Source of text
William Patrick Watson Rare Books (dealer) (catalogue 22 (2018), item 20)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 11701F,” accessed on 27 September 2021,