![Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. Volume. 2. 1st edition. Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. Volume. 2. 1st edition.](http://darwin-online.org.uk/converted/scans/1871_Descent_F937.2(online)/1871_Descent_F937.2_318.jpg)
Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. Volume. 2. 1st edition.
![Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. Volume. 2. 1st edition. Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. Volume. 2. 1st edition.](http://darwin-online.org.uk/converted/scans/1871_Descent_F937.2(online)/1871_Descent_F937.2_094.jpg)
Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. Volume. 2. 1st edition.
![The Project Gutenberg eBook of The Descent of Man and Selection in Relation to Sex, by Charles Darwin The Project Gutenberg eBook of The Descent of Man and Selection in Relation to Sex, by Charles Darwin](https://www.gutenberg.org/files/36520/36520-h/images/fig28.png)
The Project Gutenberg eBook of The Descent of Man and Selection in Relation to Sex, by Charles Darwin
![Wallace, A. R. 1876. The geographical distribution of animals; with a study of the relations of living and extinct faunas as elucidating the past changes of the Earth's surface. Volume 1. Wallace, A. R. 1876. The geographical distribution of animals; with a study of the relations of living and extinct faunas as elucidating the past changes of the Earth's surface. Volume 1.](http://darwin-online.org.uk/converted/Ancillary/1876_GeographicalDistribution_S718.1/geographicaldist01wall_fig001.jpg)