1. Charles Darwin, The Origin of Species, a Variorum Text, ed. Morse Peckham (Philadelphia, 1959), p. 164, sentence 13.
2. C. Darwin and A. R. Wallace, Evolution by Natural Selection (Cambridge, 1958). See the ?Sketch of 1842.?
3. Darwin, The Origin of Species, p. 202, sentence 227.
4. Ibid., p. 178, sentence 95.11.e.
5. Ibid., p. 267, sentence 382.65.0.50.369.