Reports of studies conducted on the survival time of the cysts of Entamoeba histolytica are frequently found in the literature of this parasite (Yorke and Adams, 1926, Jones and Newton, 1950, and Chang, 1950), but the survival time of the trophoxoites of E. histolytica in culture is seldom discussed (Tsuchiya, 1945). The work reported here was therefore undertaken in the hope that a detailed te...