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Darwin Correspondence Project

From Alexander Agassiz   4 March 1872


March 4, 1872.

Many thanks for the copy of the new edition of the “Origin of Species,” which I have just received from you.1 There are several points, especially in Embryology, which I shall take some other occasion to write you about, which may be of general interest.2 I am getting on toward the end of the Report on Echini from the deep sea of Florida, and hope to be able to send you a copy before long.3 The number of young I have been compelled to examine has led me to modify my views of the nature of genera, species, and in fact of all subdivisions. I cannot find anything that is stable, the greater the material in space and number (age) the more one is adrift to get a correct diagnosis of a genus or a species, and the gradual passage in Echini of the most widely separated groups leaves in my mind but little doubt that our classification is nothing but the most arbitrary convenient tool, depending upon the material at our command at a special time. The generalizations to which I am led from the careful study of such a small group as the Echini I shall publish at the end of my “Revision of the Echini” and as the Plates for the descriptive part are far advanced, I hope I shall not be long delayed.4 We have excellent news from the Hassler Expedition from Rio.5 Not much was expected from the dredging on this side of Cape Horn owing to the lateness of the season, but the single haul made off the Barbados must have been a wonderful catch of which I trust we shall hear and see more by and by.


Agassiz’s name appears on CD’s presentation list for Origin 6th ed. (Appendix IV).
No such letter has been found.
Agassiz inserted portions of his earlier ‘Preliminary report on the Echini and starfishes dredged in deep water between Cuba and Florida Reef’ (A. Agassiz 1869) into his Revision of the Echini (Agassiz 1872–4; see p. 371).
Agassiz devoted the first three parts of his Revision of the Echini (Agassiz 1872–4) to descriptions of particular species of Echinus and notes on synonymy, and the fourth part to a general discussion of the genus. He also produced a volume of ninety-four plates.
Alexander Agassiz’s father, Louis Agassiz, embarked on the Hassler expedition to South America in December 1871 (Marcou 1896, 2: 181–91; see also letter to Asa Gray, 15 January 1872, n. 2). Rio: Rio de Janeiro.


Agassiz, Alexander. 1869b. Preliminary report on the Echini and star-fishes dredged in deep water between Cuba and the Florida Reef, by L. F. de Pourtales, Assist. U.S. Coast Survey. Bulletin of the Museum of Comparative Zoology at Harvard 1 (1863–9): 253–307.

Agassiz, Alexander. 1872–4. Revision of the Echini. 4 parts and an atlas of plates. Cambridge, Mass.: University Press.

Marcou, Jules. 1896. Life, letters, and works of Louis Agassiz. 2 vols. London and New York: Macmillan and Co.

Origin 6th ed.: The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 6th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1872.


Thanks for new [6th] edition of Origin.

Is working on Echini.

The more material he gets the less easy it is to diagnose a genus or species. Has little doubt that "classification is nothing but the most arbitrary convenient tool, depending upon the material at our command at a special time".

Letter details

Letter no.
Alexander Agassiz
Charles Robert Darwin
Sent from
Cambridge Mass.
Source of text
G. R. Agassiz ed. 1913, p. 119

Please cite as

Darwin Correspondence Project, “Letter no. 8236,” accessed on 19 October 2019,

Also published in The Correspondence of Charles Darwin, vol. 20