1. The increase in bacteria, phage concentration, and gelatinase concentration in cultures of B. megatherium has been determined.
2. With lysogenic cultures the phage concentration, gelatinase concentration, and bacteria concentration increase logarithmically at first. The phage and gelatinase concentration then decrease while the bacteria concentration increases to a maximum.
3. The results are the same with sensitive cultures if the ratio of phage to bacteria is small. If the ratio of phage to bacteria is large phage, gelatinase, and bacteria concentration all increase at first and then decrease. The maximum rate of increase coincides approximately with the maximum rate of oxygen consumption of the culture.
4. 60–90 per cent of the phage is free from the cells.
5. The amount of phage produced is determined by the combined phage and not by the total phage.
6. Phage is produced during growth of the cells and not during lysis.
7. In a very narrow range of pH near 5.55 no increase in bacteria occurs but large increases in phage may be obtained.