Abstract
As a basis for future work some of the more common colony variations of Streptococcus are described. Little concerning the sequence of colony types is clear, but it is apparent that most of the colony variations described for other bacteria occur also in this group. The S type colony is clear cut; the R type, not so definite; there are many intermediate types. In fluid media, agglutination is associated with R types. Certain variations also parallel colony types diplococcic, Gram-positive, regular cells are of S type: long-chained, irregular, Gram-variable forms are of R types. In natural infections, virulence seems also to parallel types, S type being virulent; R types, relatively avirulent.