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Darwin Correspondence Project

From J. W. Clark   25 June 1875

18 High Street. | Southampton.

June 25. 1875.

Dear Sir,

In reference to your remarks upon the dilations of the pupils of the eye through fear, in your work on “The Expression of the Emotions”, I beg to send you the following, hoping, that it may be of service to you—1 I distinctly recollect observing, & remarking upon, the largely dilated pupils in an Irish water-spaniel, a black retriever, & within the last few days, in a fox-terrier which I have lately observed to ensure the correctness of my former observations.2 In the History of British India (Edinburgh Literary Library ed. 1843) page 32 I find this passage as descriptive of a horse’s fear of a lion—3

“.... his quivering limbs & large dilated eyes exhibit the depth of uncontrolled dismay ....”

The dilation I venture to think refers to the pupils (& not simply to the eyelids) because I have observed it in a donky not infrequently when frightened.

I shall hope to obtain some fuller & more exact information on this point; meanwhile I hope you will excuse the liberty I take in thus writing to you, and believe me to remain your sincere well-wisher & admirer, | J. W. Clark.

CD annotations

Top of letter: ‘(Expression)’ square brackets in original


In Expression, pp. 303–4, CD wrote that he had only one example of pupils dilating with fear.
A note was added to Expression 2d ed., p. 321, citing the examples of pupil dilation given by Clark in this letter and the letter from J. W. Clark, 16 September 1875. Clark’s name was given incorrectly as T. W. Clark in the note. Expression 2d ed. was published after CD’s death using CD’s notes.
The passage is from Historical and descriptive account of British India, from the most remote period to the conclusion of the Afghan war (H. Murray et al. 1843, 3: 31).


Expression 2d ed.: The expression of the emotions in man and animals. By Charles Darwin. 2d edition. Edited by Francis Darwin. London: John Murray. 1890.

Expression: The expression of the emotions in man and animals. By Charles Darwin. London: John Murray. 1872.


Observations of fear in animals marked by dilation of pupils.

Letter details

Letter no.
Joseph Warner Clark
Charles Robert Darwin
Sent from
Source of text
DAR 161: 154
Physical description
3pp †

Please cite as

Darwin Correspondence Project, “Letter no. 10030,” accessed on 19 September 2021,

Also published in The Correspondence of Charles Darwin, vol. 23