has been called Knowledge Memes or Science Memes. He also contributed to evolutionary culture theory more broadly by contributing to initial discussions surrounding the generalization of Richard Dawkins' evolutionary vehicles in memetics research. In relation to Richard Dawkins' theory of replicators, Hull introduced the notion of interactors. He was Dressler Professor in the Humanities Emeritus at Northwestern University. Bibliography Hull, D. L. (1964) Consistency and monophyly. Syst. Zool. 13:1-11. Hull, D. L. (1965) The effect of essentialism on taxonomy: two thousand years of stasis. Br. J. Philos. Sci. 15: 314-326; 16: 1-18. Hull, D. L. (1966) Phylogenetic numericlature. Syst. Zool. 15:14-17. Hull, D. L. (1967) Certainty and circularity in evolutionary taxonomy. Evolution 21:174-189. Hull, D. L. (1968) The operational imperative—sense and nonsense in operationalism. Syst. Zool. 17:438-457. Hull, D. L. (1969) Morphospecies and biospecies: a reply to Ruse. Br. J. Philos. Sci. 20:280-282. Hull, D. L. (1970) Contemporary systematic philosophies. Annu. Rev. Ecol. Syst. 1:19-54. Hull, D. L. (1973) Darwin and His Critics: The Reception of Darwin's Theory of Evolution by the Scientific Community. Cambridge, MA: Harvard University Press; reprinted by the University of Chicago Press, 1983, . Hull, D. L. (1974) Philosophy of Biological Science. Englewood Cliffs: Prentice-Hall, ; translated into Portuguese (1975), Japanese (1994). Hull, D. L. (1976) Are species really individuals? Syst. Zool. 25:174-191. Hull, D. L. (1978) A matter of individuality. Philos. Sci. 45:335-360. Hull, D. L. (1978) The principles of biological classification: the use and abuse of philosophy. Vol. 2, pp. 130–153. Proceedings of the Biennial Meeting of the Philosophy of Science Association. Hull, D. L. (1979) The limits of cladism. Syst. Zool. 28:416-440. Hull, D. L. (1980) Individuality and selection. Annu. Rev. Ecol. Syst. 11:311-332. Hull, D. L. (1981) Kitts and Kitts and Caplan on species. Philos. Sci. 48:141-152. Hull, D. L. (1981) Metaphysics and common usage. Behav. Brain Sci. 4:290-291. Hull, D. L. (1983) Karl Popper and Plato's metaphor. pp. 177–189 in N. I. Platnick, and V. A. Funk, eds. Advances in Cladistics, Vol. 2 Columbia University Press, New York. Hull, D. L. (1983) Thirty-one years of Systematic Zoology. Syst. Zool. 32:315-342. Hull, D. L. (1984) Cladistic theory: hypotheses that blur and grow. pp. 5–23 in T. Duncan, and T. F. Stuessy, eds. Cladistics: perspectives on the reconstruction of evolutionary history. Columbia University Press, New York. Hull, D. L. 1984. Can Kripke alone save essentialism? A reply to Kitts. Syst. Zool. 33:110-112. Hull,