In the present paper, the characteristics of the genus Schizotrypanum were analyzed and their relationship to those of other digenetic flagellates considered. It is to be believed that proper evidence has been brought forward to establish that genus on a firm basis. Schizotrypanum has peculiar morphological characters which assimilate it to Leishmania in the intracellular period and to Trypanosoma in the blood stage. Flagellates belonging to that genus are characterized not only by the morphology of the trypanosome form, but also by the evolution in the vertebrate's organism. In S. cruzi, as in S. pipistrelli, multiplication takes place in the tissues by binary division of the intracellular leishmania forms, the blood trypanosomes do not multiply. Trypanosoma never presents in the mammalian host an evolution morphologically and ecologically identical to that of Schizotrypanum. S. cruzi is rather like the pathogenic trypanosomes by the morphology of the blood form and by its virulence, often fatal to man to various animals; it differs however, from these by its evolution in the insect, and its mechanism of transmission, which are common to the non-pathogenic trypanosomes. S. cruzi cannot be rigorously included in either of these groups, as it is easily distinguished both by its morphology, and by its biology. The combination of its biological and morphological characters perfectly justifies the maintaining of Chagas' genus and assigns to it an intermediate position between Leishmania and Trypanosoma. This appears to be the best case, if not the only justifiable one, for the demembration of the genus Trypanosoma. The recognition of Schizotrypanum in an independent status is based upon a rigid systematic basis and imposes itself as a comprehensive and quite useful means of coordinating the members of the intricate family Trypanosomidae.