1. At 5°C. no germination took place.
2. At 25°C. and at 37°C. germination occurs if the hydrogen ion concentration of the broth is kept between pH 5 and pH 10, but not at higher or lower pH values.
3. The completion of the spore cycle likewise requires a hydrogen ion concentration between pH 5 and pH 10.
4. The spores can germinate when the pH value is 10, although after germination the vegetative cells multiply only to a very slight extent and soon pass into spores.
5. The slight growth and multiplication of vegetative cells in broth of pH 10 suggest that the formation of endospores in this medium must be caused largely by the unfavorable reaction of the medium rather than by the accumulation of metabolic products.
6. Automatic adjustment of the medium seems to play a rôle in the completion of the spore cycle.
7. The results are not only of theoretical importance but they have a practical application to the preservation of food by canning and by other methods.