The Evolutionary Significance of the Protozoan Parasites of Monkeys and Man

Abstract

The protozoa of monkeys and man are in this paper divided into: amoebae, intestinal flagellates, intestinal ciliates, trypanosomes, leishmanias, malarial parasites, babesias, and doubtful protozoan parasites. In all, 25 species are listed from man and 19 from monkeys. Of the 19 from monkeys 14 are indistinguishable morphologically from protozoa described from man. Three species of ciliates and 1 babesia occur in monkeys but not in man. Two species of amoebae, 2 of intestinal flagellates, 3 of leishmanias, an Isospora and a Sarcocys-tis occur in man but not in monkeys. When protozoa of other lower animals are compared with those from man it is found that practically all of them are distinguishable morphologically as distinct species. The evident close relationships of these protozoan parasites indicate a common ancestry of their human and monkey hosts and furnish evidence in favor of the hypothesis that monkeys and man are of common descent.