Eimeria tenella and E. necatrix: a third generation of schizogony is an obligatory part of the developmental cycle.

The latter part of endogenous development of Eimeria tenella and E. necatrix was examined in sections of cecal tissue taken from chickens infected either by giving oocysts orally or by injecting merozoites into the cecum. The findings, with 3 strains of E. tenella and 1 of E. necatrix, indicate that the majority, if not all, of the parasite populations undergo a third generation of schizogony and then embark upon gametogony.