They occur in Darwin's Descent of Man (1871) and The Expression of the Emotions in Man and Animals (1872), and in Huxley's Evidence as to Man's Place in Nature (1863).
These occurrences can be found in Darwin's Descent of Man (1871) and The Expression of the Emotions in Man and Animals (1872), alongside Huxley's Evidence as to Man's Place in Nature (1863).