This interpretation of facts was combated especially by A. Schneider (1892) and by Labbé, but has, nevertheless, proved true, apart from the circumstance that Schuberg succeeded in discovering the hitherto unknown _Coccidium_ form in the intestine of the mouse; and that, moreover, Léger confirmed the fact that there are no Arthropoda in which Eimeria are not found together with coccidia. The question was finally settled by experiments made by Léger with the coccidia of _Scolopendra cingulata_, by Schaudinn and Siedlecki with those of _Lithobius forficatus_, and by Simond with the coccidia of the rabbit. On Simond’s suggestion the sickle-shaped germs corresponding to the sporozoites, which are formed by endogenous sporulation, are generally termed merozoites; and in accordance with Schaudinn’s suggestion, those individuals which form merozoites are termed schizonts, and those which produce spores are called sporonts. In contradistinction to sporogony (exogenous sporulation), the term schizogony (endogenous sporulation) is used. The more minute examination of these processes at last led to the discovery of sexual dimorphism, of copulation and of alternation of generations in the coccidia. Schuberg was the first to consider the possibility of copulation in coccidia; in addition to the formations which now are termed merozoites, he observed very diminutive bodies (“microsporozoites”) in the coccidia of the intestine of the mouse, which were able eventually to copulate. Labbé confirmed this observation in some of the species, and Simond expressed the opinion that bodies termed “chromatozoites” occurred in all coccidia. Copulation itself was then observed by Schaudinn and Siedlecki (1897). The copulating bodies were termed gametes. As, however, they differed considerably one from the other, the males were called microgametes (_i.e._, the microsporozoites of Labbé and the chromatozoites of Simond) and the females macrogametes. After copulation was completed sporogony took place, and in the cycle of development of one species this regularly alternated with schizogony (asexual multiplication). Schaudinn in 1900 described in detail the life-cycle of _Eimeria_ (_Coccidium_) _schubergi_. The recognition of this unsuspected complicated process was bound to effect reforms in the classification of the coccidia; and all the forms that had been regarded as developmental stages (_Eimeria_, etc.) had to be reconsidered.