![Darwin, C. R. 1874. The descent of man, and selection in relation to sex. London: John Murray. 2d ed.; tenth thousand. Darwin, C. R. 1874. The descent of man, and selection in relation to sex. London: John Murray. 2d ed.; tenth thousand.](http://darwin-online.org.uk/converted/scans/1874_Descent_F944(online)/1874_Descent_F944_676.jpg)
Darwin, C. R. 1874. The descent of man, and selection in relation to sex. London: John Murray. 2d ed.; tenth thousand.
![Lyell, Charles. 1863. The geological evidences of the antiquity of man with remarks on the origin of species by variation. 3rd edition, revised. London: John Murray. Lyell, Charles. 1863. The geological evidences of the antiquity of man with remarks on the origin of species by variation. 3rd edition, revised. London: John Murray.](http://darwin-online.org.uk/converted/scans/1863_Lyell_A282(online)/1863_Lyell_A282_497.jpg)
Lyell, Charles. 1863. The geological evidences of the antiquity of man with remarks on the origin of species by variation. 3rd edition, revised. London: John Murray.
![Darwin, C. R. 1874. The descent of man, and selection in relation to sex. London: John Murray. 2d ed.; tenth thousand. Darwin, C. R. 1874. The descent of man, and selection in relation to sex. London: John Murray. 2d ed.; tenth thousand.](http://darwin-online.org.uk/converted/scans/1874_Descent_F944(online)/1874_Descent_F944_171.jpg)
Darwin, C. R. 1874. The descent of man, and selection in relation to sex. London: John Murray. 2d ed.; tenth thousand.
![Darwin, C. R. 1874. The descent of man, and selection in relation to sex. London: John Murray. 2d ed.; tenth thousand. Darwin, C. R. 1874. The descent of man, and selection in relation to sex. London: John Murray. 2d ed.; tenth thousand.](http://darwin-online.org.uk/converted/scans/1874_Descent_F944(online)/1874_Descent_F944_268.jpg)