“It may be doubted whether any character can be named which is distinctive of a race and is constant.”
volume I, chapter VII: "On the Races of Man", page 225 http://darwin-online.org.uk/content/frameset?pageseq=238&itemID=F937.1&viewtype=image
The Descent of Man (1871)
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Charles Darwin 161
British naturalist, author of "On the origin of species, by… 1809–1882Related quotes

Source: The Number-System of Algebra, (1890), p. 3; Reported in Robert Edouard Moritz. Memorabilia mathematica; or, The philomath's quotation-book https://archive.org/stream/memorabiliamathe00moriiala#page/81/mode/2up, (1914), p. 263

The Comic
1870s, Society and Solitude (1870), Books, Letters and Social Aims http://www.rwe.org/comm/index.php?option=com_content&task=category§ionid=5&id=74&Itemid=149 (1876)

Source: Sanitary Economy (1850), p. 28-29
Context: It has been among the visions of some dreaming philosophers that human life is capable of almost indefinite extension. The great Condorcet was one of these. He thought that by the removal of the two causes of evil—poverty and superfluity—by destroying prejudices and superstitions, and by various other operations, which he considered the purification of mankind, but which other people would call their pollution, the approach of death would by degrees be farther and farther indefinitely protracted. It is desirable that the practical views entertained by sanitary reformers should be kept widely distinct from any such theories, the character of which has been well drawn by Malthus when he says—"... Though I may not be able in the present instance to mark the limit at which further improvement will stop I can very easily mention a point at which it will not arrive."

Speech given to the Imperial Institute (11 November 1895), quoted in "Mr. Chamberlain On The Australian Colonies", The Times (12 November 1895), p. 6
1890s
Anatol Rapoport, "Outline of a probabilistic approach to animal sociology: I." The Bulletin of mathematical biophysics 11.3 (1949): p 183
1940s

Lectures XI, XII, and XIII, "Saintliness"
1900s, The Varieties of Religious Experience (1902)