140 RUTH L. PHILLIPS 



the organisms used for food were B. coli, B. cereus, and B. pro- 

 teus. These were chosen because of the common occurrence of 

 B. coU in bodies of water in which Paramecium is found in nature, 

 and because B. cereus and B. proteus are such frequent sapro- 

 phytes and might, therefore, be expected to be occasional com- 

 ponents of the food of Paramecium. The pure cultures of these 

 organisms were obtained from the laboratory stock of the De- 

 partment of Bacteriology. The following descriptions of the 

 bacteria used include such features as morphology, nature of the 

 agar colonies, staining reactions, and reactions with various 

 media. These features should be an aid to one who wishes to 

 work with such bacteria in determining whether the types he has 

 isolated are the same as those here described. It is fully realized 

 that with the present lack of detailed knowledge of the sapro- 

 phytic bacteria, such a description can only be an aid in identi- 

 fication and cannot be considered as a key to these types of 

 bacteria. 



Indol formation could not be determined, owing to trouble 

 with the reagents. 



Organism A. Belongs to Bacterium class III, group II, the Rhino- 

 sclermatis group of Chester. Isolated from a one- to three-day hay 

 infusion. 



Morphology: short rod, nearly spherical, grows in chains, non- 

 motile. 



Agar colonies: round, moist, glistening, granular, edge sharply de- 

 fined and broadly lobed as in colon type, non-chromogenic. 



Staining reactions: capsulated, pleomorphic, show bipolar staining, 

 Oram negative. 



Gelatin: not liquefied, growth uniform, line of puncture beaded. 



Litmus milk: neutral to slightly alkaline. 



Bouillon : sediment at bottom, cloudy. 



Dextrose bouillon: no acid, no gas, heavy membrane at bottom, 

 cloudy. 



Lactose bouillon : no acid, no gas, slight sediment at bottom, cloudj'. 



Saccharose bouillon: no acid, no gas, cloudy. 



Mannite bouillon: no acid, no gas, cloudy. 



Organism B. Did not grow well after the first few transfers, and 

 died before the characteristics could be determined. 



Organism C. Belongs to class XV, group II B, the subtihs group 

 of Chester. Isolated from a nine- to fourteen-day hay infusion. 



Morphology: short rod, some short chains noted, cndospores cen- 

 tral, markedly motile. 



