1. The enzymes hexokinase, aldolase and triosephesphate dehydrogenase have been demonstrated in crude extracts of Z. ventriculi. 2. Pyruvate formation from 3-phosphoglyceric acid has also been obtained with crude extracts. 3. The fermentation of glucose by whole cells of Z. Ventriculi has been shown to be inhibited by iodoacetate but not by fluoride. 4. With toluene-treated cells of Z. ventriculi pyruvate is fermented mainly to CO2 and acetaldehyde, with the formation of smaller amounts of acetein, lactate and acetate. 5. The evolution of CO2 from pyruvate by toluene-treated cells has been shown to be sensitive to the inhibitors of a yeast-type carboxylase. 6. At pH 4.9 whole cells of Z. ventriculi ferment pyruvate quantitatively to equimolar amounts of acetate, H2 and CO2. 7. Formic hydrogenlyase, formic dehydrogenase and hydrogenase have been demonstrated with washed-cell suspensions of Z. ventriculi. 8. The formic hydrogenlyase system has been shown to be sensitive to the inhibitors of the formic hydrogenlyase system in E. coli. 9. On the basis of these findings, a scheme for the fermentation of glucose by Z. ventriculi has been propsed which accounts for the fermentation balances obtained by earlier workers. 10. The results indicate that Z. ventriculi is unique in being the only organism which possesses both a yeast-type carboxylase and a elastic reaction for the metabolism of pyruvate