[82] I have not attempted to give a history of the development of the theory. For a more minute study of the theory, I must refer the reader to the writings of Engels, Seligman, Ferri, Ghent, Bax, and others quoted in these pages.
[83] Capital, Vol. I, page 406 n. (Kerr edition).
[84] Liebknecht, Memoirs of Karl Marx, page 91.
[85] Charles Darwin and Karl Marx, A Comparison, by Edward Aveling, London, 1897.
[86] See Thorold Rogers, The Economic Interpretation of History, second edition, 1891, pages 10-12.
[87] For various reasons, chief of which is that it would take me too far away from my present purpose, I do not attempt to develop the serious consequences of these events to Europe. See The Economic Interpretation of History, Chapter I, for a brief account of this.
[88] Ancient Society, or Researches in the Lines of Human Progress from Savagery through Barbarism to Civilization, by Lewis H. Morgan. New edition, Chicago, 1907.
[89] Darwin, The Descent of Man, second edition, page 163.
[90] Mutual Aid a Factor of Evolution, by Peter Kropotkin, pages 5-6.
[91] Idem, page 74.