1. The classification of fusobacteria into types, as suggested by Slanetz and Rettger on the basis of their cultural and biochemical characteristics, was confirmed. The following additional data are presented: the behavior of types I, II, and III in several previously untested carbohydrates; the final pH in 1 per cent glucose broth; the hydrolysis of starch; the failure to decompose sodium hippurate and citrates; the absence of pathogenicity for several types of experimental animals; and the absence of fibrinolysin and of proteolytic enzymes.
2. By the use of a technic described in the text, it was possible to grow the anaerobic fusobacteria in mass cultures.
3. With the methods of Heidelberger and Kendall, immunologically type specific proteins were extracted from fusobacteria types I, II, and III. This observation, which is in a sense an extension of the work of Lancefield on Streptococcus hemolyticus, group A, represents the second instance of a bacterial protein functioning as a determinant of bacterial types.
4. Preliminary data indicate that group specificity depends upon a carbohydrate which is extractable by the methods of Heidelberger and Avery.