tapeworms; Pappas (1981, loc. cit.) used 12-dayold tapeworms; while Pappas (1984, loc. cit.) and the current study used 6-day-old tapeworms), or different species of intermediate hosts. It has been shown that tapeworms of different ages differ physiologically and/or biochemically (e.g., Mettrick and Cannon, 1970, Parasitology 61: 229243; Watts and Fairbairn, 1974, Journal of Parasitology 60: 621-625; Coles and Simpkin, 1977, International Journal for Parasitology 7: 127128; Pappas et al., 1983, loc. cit.; Pappas, 1984, loc. cit.) and that the intermediate host in which cysticercoids are reared may affect the physiological properties of the adult tapeworms (Mettrick and Rahman, 1984, loc. cit.). Thus, when comparing the results of experiments which use different strains of H. diminuta, and which may also use different aged tapeworms and species of intermediate hosts, discrepancies in the data are to be expected.