RHODO-THIOBACTERIA 151 



Within recent years Bavendamm has succeeded in making 

 artificial cultures of a species of " RJiabdochroniathim.'" If 

 the spindle shape which is the distinguishing feature of this 

 organism were maintained in an artificial culture, a very 

 important fact would have been established, and the difference 

 of form, if permanent, would have sufficed to give this type 

 of organism generic rank. But Bavendamm describes the 

 organisms cultivated by him as made up of dull red rods of 

 irregular shape and of varying dimensions. The length 

 varied from short rods to lengths of 58/x. The spindle shape 

 is only one of numerous other forms. It seems probable, 

 judging from Bavendamm's figures and description, that he 

 had under observation an organism probably of the type of 

 Beggiatoa roseo-persicina that reacts to artificial conditions 

 by the production of a large number of pleomorphic forms. 

 Or, alternatively, they may have been variant forms such 

 as are commonly seen in the cultivation of the acetic acid 

 bacteria, such as, for example, Bacillus aceti. The terms 

 Rhahdomonas and Rhabdochromatiiini may have their uses for 

 descriptive purposes, but we are not justified in using them 

 with generic or even specific rank. In the following descrip- 

 tion the terms are retained merely as labels. They designate 

 organisms that in all probability are phases in the life-histories 

 of pleomorphic species, that have been described under other 

 names ; our knowledge is not yet sufficiently advanced to 

 determine the identity of the organisms of which they are 

 the phases. 



Rhabdochromatium koseum (Cohn), Winogradsky. 



Literature. — Cohn (10), 1875 ; Warming, 1875 ; Zopf 

 (i), 1882, and (3), 1895 ; Winogradsky (2), 1888 ; Mitro- 

 phanow, 1893; Migula, 1894, 1895, 1900; Butschli 

 (4), 1902 ; Nadson (2), 1903 ; Kolkwitz (3), 1909 ; 

 Lauterborn (7), 1915; Bergey, 1923. 



Description. — ^This is the Rhahdomonas rosea of Cohn and of 

 Bergey. It is composed of spindle or rod forms, of unequal thick- 

 ness. Average thickness, 3 — 5jLt. Some attain the length of 35/i. 



