![Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. vol. 1. Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. vol. 1.](http://darwin-online.org.uk/converted/scans/1871_Descent_F937.1(online)/1871_Descent_F937.1_158.jpg)
Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. vol. 1.
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(PDF) Love bites: male frogs (Plectrohyla, Hylidae) use teeth scratching to deliver sodefrin precursor-like factors to females during amplexus
![Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. vol. 1. Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. vol. 1.](http://darwin-online.org.uk/converted/scans/1871_Descent_F937.1(online)/1871_Descent_F937.1_072.jpg)
Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. vol. 1.
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