1. The "sludge" phage obtained by Clark and Clark answers all requirements for pronouncing it identical with the classical bacteriophage.
2. The "sludge" phage failed to produce lysis in any of the 102 human pathogenic streptococci tested.
3. Numerous attempts to induce regeneration of various lytic principles by human streptococci resulted in failure.
4. It was possible, however, to "train" erysipelas streptococci to regenerate a lytic principle active against 76 per cent of strains of this group.
5. The erysipelas phage showed remarkable specificity.