Electron Microscope Studies of Reproducing and Interkinetic Toxoplasma

SYNOPSIS. The reproduction of Toxoplasma gondii has been investigated in osmium fixed and sedimented mouse peritoneal exudate. The material was obtained 9 days after intraperitoneal inoculation with the Beverley strain. Predominantly intracellular organisms were seen in various phases of multiplication and indicated the occurrence of three different modes of reproduction. One is a schizogonic cycle, whereby at least four progenies are delineated within a rosette‐shaped, multinucleated Toxoplasma cell. They subsequently separate to become individual parasites. The second mode is considered as a special type of schizogony that results in the production of only two merozoites within one parent cell. This process previously has been designated as endodyogeny. Finally, the observations suggest division by binary fission as a third type of reproduction. From these results, it is possible to relate the genus Toxoplasma, previously regarded as a protozoon of uncertain classification, to the class Sporozoa.