Classification of the bacteria follows Breed et al. (1948). Synonymy in most cases was taken from the same source. Names of bacteria preceded by the symbol [cross] are either not listed by Breed et al. or are stated by them to be insufficiently characterized for definite classification. Use of asterisk is explained in footnote 3, page 4. Phylum SCHIZOPHYTA Class SCHIZOMYCETES Order EUBACTERIALES Family PSEUDOMONADACEAE * =Pseudomonas aeruginosa= (Schroeter) Migula _Natural vectors._--_Blaberus craniifer_, U.S.A. (Wedberg et al., 1949). _Blatta orientalis_, U.S.A. (Olson and Rueger, 1950). _Blattella germanica_, U.S.A. (Olson and Rueger, 1950; Janssen and Wedberg, 1952). _Periplaneta americana_, U.S.A. (Bitter and Williams, 1949, 1949a; Olson and Rueger, 1950). _Experimental vectors._--_Blattella germanica_, U.S.A. (Herms and Nelson, 1913). Cockroaches, U.S.A. (Longfellow, 1913). * =Pseudomonas eisenbergii= Migula _Natural and experimental vectors._--_Blatta orientalis_, Italy (Cao, 1906). * =Pseudomonas fluorescens= Migula _Natural and experimental vectors._--_Blatta orientalis_, Italy (Cao, 1898, 1906; Spinelli and Reitano, 1932). _Periplaneta americana_, U.S.A. (Gier, 1947): The organism was pathogenic to the cockroach when injected. [cross] =Spirillum periplaneticum= Kunstler and Gineste _Habitat._--_Periplaneta americana_, France? (Kunstler and Gineste, 1906): From intestinal tract. [cross] =Spirillum α, β, and γ= Dobell _Habitat._--_Blatta orientalis_, England (Dobell, 1911, 1912): From hind gut. =Spirillum= sp. _Habitat._--_Blatta orientalis_, U.S.S.R. (Zasukhin, 1930): From intestinal tract. Cockroaches, Venezuela (Tejera, 1926): From digestive tract. * =Vibrio comma= (Schroeter) Winslow et al. _Experimental vectors._--_Blatta orientalis_, Italy (Cao, 1898; Spinelli and Reitano, 1932). _Blattella germanica_, Orient (Toda, 1923); Germany (Jettmar, 1927). _Periplaneta americana_, Philippine Islands (Barber, 1914); Netherlands (Akkerman, 1933); Formosa (Morischita and Tsuchimochi, 1926). _Periplaneta australasiae_, Formosa (Morischita and Tsuchimochi, 1926). * =Vibrio metschnikovii= Gamaléia _Experimental vectors._--_Blatta orientalis_, Italy (Cao, 1898, 1906). =Vibrio tyrogenus= (Flügge) Holland _Synonymy._--_Vibrio_ of Deneke. _Experimental vectors._--_Blatta orientalis_, Italy (Cao, 1898): The organism passed through the intestinal tract unchanged. [cross] =Vibrio Types I and II= Heiberg _Habitat._--Water. _Natural vectors._--Cockroaches, India (Pasricha et al., 1938): The vibrios were found in 16 or 17 percent of 94 cockroaches and resembled _Vibrio comma_ in their morphology and their main biochemical reactions; however, serum-agglutination reactions differed. =Vibrio= sp. _Habitat._--_Blatta orientalis_, U.S.A. (Leidy, 1853): From intestine. Family RHIZOBIACEAE =Chromobacterium violaceum= (Schroeter) Bergonzini _Synonymy._--_B. violaceus._ _Habitat._--Water.