In 1900, the Italian zoologist Giovanni Battista Grassi categorized "Plasmodium" species based on the timing of fever in the patient; malignant tertian malaria was caused by "Laverania malariae" (now "P. falciparum"), benign tertian malaria by "Haemamoeba vivax" (now "P. vivax"), and quartan malaria by "Haemamoeba malariae" (now "P. malariae").