[Origin of sac-shaped walls in Entamoeba invadens cultures during the encystment process].

Changes in the population of trophozoites, cysts and bag-shaped walls in an encysting culture of Entamoeba invadens were determined. The results indicated that bag-shaped walls do not play a precursor role in the encystation of the organism. Samples of cells from encysting cultures were stained in vivo with Calcofluor M2R. Microscopic observations indicated also that bag-shaped walls do not play a precursor role in the formation of the cyst. It was suggested that bag-shaped walls arise from an abnormal response of some trophozoites when the culture is transferred to the encystation medium.