This peripheral blood smear comes from a patient with malaria. This infection happens to be with Plasmodium vivax. At the arrow is a RBC with a malarial parasite in the shape of a ring. Three other RBC's in this smear are also infected with a ring trophozoite. The rarely seen sexual phase of this organism, the gametocyte, is shown. Speciation of Plasmodium can be done, albeit with difficulty, by identification of subtle morphologic variations in the appearance of these parasites.