The cytoplasmic division of Entamoeba histolytica trophozoites has been studied in culture in a medium which is a modification of the CLG medium of McDade and Shaffer. The entire process has been recorded on motionpicture film. Contacts between two trophozoites which are suggestive of conjugation have been repeatedly observed.
The process of division consists of a simple binary fission in which a narrow band is formed between the dividing cells. This band becomes streched and then separates rather suddenly. A thin, hairlike connection sometimes persists between the daughter cells for a period of time. The whole division process is usually completed within 3 to 8 minutes.
On several occasions a single trophozoite has been seen to divide into three and this has also been recorded on film. Sometimes the three daughter cells are all the same size; but, in other instances, one of the daughter cells is much smaller than the other two. It is suggested that this may explain the occurrence of very small amebae in 48- to 72-hour cultures of large race strains of E. histolytica in routine Shaffer-Frye and CLG media.
Present address: The Lutheran General Hospital, 1775 Dempster Street, Park Ridge, Illinois.
The authors wish to express their appreciation to Mrs. Britt Werner for valuable assistance in these studies.