As regards the higher forms of protozoa it must suffice to allude to the _Cercomonas hominis_ of Davaine, found in the dejections of cholera patients, to the _Cerc. urinarius_ of Hassal and _C. saltans_ of Ehrenberg, to the _Trichomonas vaginalis_ of Donné, detected in the vaginal mucus, and to the _Balantidium coli_ of Claparède and Lachmann, originally found by Malmsten in the human colon. The _Balantidium_, or _Paramæcium coli_, has frequently been observed in the evacuations of fever patients, and it has also been found by Dr Treille in patients suffering from the Cochin-China diarrhœa. Monads have also been found in the stomach and intestines of the hog and various other animals. Infusorial parasites are particularly abundant in batrachians, the _Bursariæ_ of frogs and toads being familiar to every helminthologist. BIBLIOGRAPHY (No. 41).--_Arloing_ (and _Tripier_), in ‘Gaz.-hebd.,’ 1873, p. 574 (quoted by Davaine).--_Balbiani_, ‘Compt. Rend. Soc. Biol.,’ 1867, p. 103 (quoted by Davaine and Bastian).--_Bastian_, “On the Nature of the so-called _Sarcina ventriculi_,” ‘Brit. Med. Journ.,’ Feb. 3, 1872.--_Idem_, “On Heterogenesis in its relation to certain Parasitic Diseases,” ‘Brit. Med. Journ.,’ Feb. 24 and April 20, 1872 (see part iv, p. 417, with figs. from Balbiani).--_Beale, L._, “Entozoon-like bodies in Muscles,” in the ‘Microscope in Medicine,’ 4th edit., p. 485, 1878.--_Idem_, “Bacterium Hypothesis of Contagium,” _ibid._, pp. 313-321.--_Burnett, W. T._, “On Psorospermia, Mermithes, &c.,” in a paper entitled ‘Reviews and Records in Anat. and Physiol.,’ in ‘Amer. Journ. of Sci. and Arts,’ vol. xviii, 2nd ser., p. 104, 1854.--_Carter, H. V._, “On Spirilla,” quoted by Sanderson in ‘Brit. Med. Journ.,’ Nov. 17, 1877, p. 700.--_Cobbold_, “Remarks on Spurious Entozoa found in Diseased and Healthy Cattle,” ‘Path. Soc. Trans.,’ vol. xvii, p. 452, 1866, and ‘Lancet,’ Jan. 27, 1866, p. 88; see also Prof. J. Gamgee’s work on the ‘Cattle Plague.’--_Idem_, “On Worm-like Organisms in the Mitral Valve of a Horse,” ‘Veterinarian,’ Sept., 1877.--_Idem_, “On Psorospermiæ in the Eye of the Cod (Morrhua),” ‘Linnean Society’s Proc.,’ May, 1862, and in ‘Intellectual Observer,’ 1862, p. 199.--_Cohn_, ‘Nova Acta,’ xxiv, s. 103 (quoted by Leuckart), Bd. i, s. 139.--_Creplin_, ‘Wiegmann’s Archiv,’ 1842, s. 61.--_Davaine_, l. c., 2nd edit., “Synops. xxi” (with bibliog. refs.), 1878.--_Donné_, ‘Cours de Microscopie,’ Paris, 1847, p. 157.--_Dressler_, quoted by Leuckart, Bd. i, s. 141.--_Drummond_, ‘Edin. Phys. Rep.,’ 1852,--_Dufour_, ‘Ann. des Sci. Nat.,’ 1837.--_Dujardin_, ‘Traité’ (l. c., see Bibl. No. 1).--_Eberth_, ‘Zur Kentniss Bacteritischer Mykosen,’ 1872.--_Eimer_, ‘Ueber Psorospermien,’ 1870.--_Gairdner_, ‘Edin. Phys. Soc. Rep.,’ 1853.--_Gluge_, “Cysts in Sticklebacks,” ‘Bullet. Acad. Roy. des Sci. de Bruxelles,’ 1838.--_Gubler_, ‘Mem. Soc. Biol.,’ 1859, p. 657, and in ‘Gaz. Méd.,’ 1858, p. 61.--_Harz, C.