Class II. MASTIGOPHORA, Diesing 50 Sub-class. FLAGELLATA, Cohn emend. Bütschli 50 Order. _Polymastigina_, Blochmann 52 Genus. _Trichomonas_, Donné, 1837 52 _Trichomonas vaginalis_, Donné 52 _Trichomonas intestinalis_, R. Leuckart, 1879 = _Trichomonas hominis_, Davaine, 1854 54 Genus. _Tetramitus_, Perty, 1852 57 _Tetramitus mesnili_, Wenyon, 1910 57 Genus. _Lamblia_, R. Blanchard, 1888 57 _Lamblia intestinalis_, Lambl, 1859 57 Order. _Protomonadina_, Blochmann 60 Family. _Cercomonadidæ_, Kent emend. Bütschli 61 Genus. _Cercomonas_, Dujardin emend. Bütschli 61 _Cercomonas hominis_, Davaine, 1854 61 _Monas pyophila_, R. Blanchard, 1895 62 Family. _Bodonidæ_, Bütschli 63 Genus. _Prowazekia_, Hartmann and Chagas, 1910 63 _Prowazekia urinaria_, Hassall, 1859 63 _Prowazekia asiatica_, Castellani and Chalmers, 1910 65 _Prowazekia javanensis_, Flu, 1912 66 _Prowazekia cruzi_, Hartmann and Chagas, 1910 66 _Prowazekia weinbergi_, Mathis and Léger, 1910 66 _Prowazekia parva_, Nägler, 1910 66 Family. _Trypanosomidæ_, Doflein 66 Genus. _Trypanosoma_, Gruby, 1843 67 Historical 67 General 69 Morphology 70 _Trypanosoma gambiense_, Dutton, 1902 72 _Trypanosoma nigeriense_, Macfie, 1913 76 _Trypanosoma rhodesiense_, Stephens and Fantham, 1910 76 General Note on Trypanosomes with Posterior Nuclei 83 _Trypanosoma cruzi_, Chagas, 1909 83 _Trypanosoma lewisi_, Kent, 1881 88 _Trypanosoma brucei_, Plimmer and Bradford, 1899 93 _Trypanosoma evansi_, Steel, 1885 95 _Trypanosoma equinum_, Voges, 1901 96 _Trypanosoma equiperdum_, Doflein, 1901 97 _Trypanosoma theileri_, Bruce, 1902 98