Two cultures of C. parasporogenes, apparently descendents of Mclntosh''s original culture, consist of smooth colony types, resembling Mclntosh''s description of the species, and rough types characteristic of C. sporogenes. 3 of 9 cultures supposed to be C. sporogenes consist of similar S and R types. S types recovered from both C. parasporogenes and C. sporogenes readily revert to R form characteristic of C. sporogenes. Quantitative differences in antigenic content of S and R types were found, but the differences were not greater than between S and R types of many spp. Since colony structure and antigenic content are the Only differences which have been indicated between C. parasporogenes and C. sporogenes, and since C: parasporogenes is shown to produce, by variation, C. sporogenes, it is suggested that C. parasporogenes is an invalid species.