Stages of Merogony in Multinucleate Merozoites ofEimeria magnaPérard, 1925*

SYNOPSIS. Stages of merogony of Eimeria magna were observed with the electron microscope in schizonts in ultrathin intestinal sections from white rabbits killed 4 days after inoculation. Some of the mature schizonts observed had uninucleate merozoites, whereas others had multinucleate ones. In each of the latter were rough endoplasmic reticulum, mitochondria, micronemes, refractile bodies, and occasionally, lipid droplets; some nuclei had a nucleolus. In the interior of some multinucleate merozoites, anlagen of daughter merozoites were observed. Each anlage was associated closely with a nucleus. In some of these nuclei, a cone-shaped pole of a spindle was directed toward the anlage. Each early anlage consisted of an inner membrane complex with a rhoptry anlage. A Golgi complex frequently was seen at the base of the anlage. One multinucleate merozoite, still attached to the residual body, had a merozoite anlage. In later stages of merogony, the anlagen were longer and each had a conoid. In one such merozoite, 2 merozoite anlagen were observed in close association with an eccentric intranuclear spindle, and 1 anlage had a Golgi adjunct. Another merozoite had an eccentric spindle and associated centrioles, but no visible anlagen. The finding of stages of merogony in multinucleate merozoites of E. magna indicates that these might represent a further schizogonic generation occurring in the original parasitophorous vacuole.