[Genesis of merozoites in the coccidia, Eimeria necatrix. Ultrastructural study].

Second generation schizonts of Eimeria necatrix were studied with the aid of the electron microscope. Differentiation of daughter merozoites is associated with the last mitosis, which is not significantly different from the earlier ones. The merozoites develop at the periphery of the schizont. The conoid and 22 subpellicular microtubules, probably induced by centrioles, and the inner membranes complex and the rhoptry anlagen which seem to be produced by the Golgi apparatus, appear close to each nuclear pole, just near the schizont membrane. These organelles are the first to appear in the merozoite anlagen. Then, nucleus, dictyosome and multimembranous vescles enter the budding merozoites. Micronemes, probably originating from Golgi apparatus, and amylopectin granules are produced later, when daughter merozoites separate from the residuum. The genesis of these various organelles and the relation between the last mitosis and differentiation are discussed.