[Ultrastructure of chronic reticuloendothelial forms of Isospora of sparrows].

Mononucleated reticulo-endothelial stages of Isospora from Sparrows were studied by T. E. M. during the winter period when the extra intestinal infection is chronic. Results show a very slow evolution from merozoite to trophozoite stage, a transformation of the parasite nucleus and a characteristic reaction of the host cell. These observations are discussed in relation to what is known of hypnozoite and chronic schizogony of Plasmodium.