HETEROTROPHIC BACTERIA REQUIRING COMBINED NITROGEN 145 



aggregations of protoplasm at the periphery. The protoplasm is rapidly con- 

 verted into peculiar globular, highly refractile bodies, particularly on glucose 

 agar. Shadow and transparent forms appear early. The spores are central, 

 excentric or sub-terminal, oval to cylindrical, measuring usually 0.75 to 1.12 

 by 1.5 to 2ju. Spores vary greatly in shape, being sometimes round, sometimes 

 rectangular, often reniform. Growth on solid media as thick pultaceous mass, 

 on liquid media as turbidity with little or no scum formation. 



Bacillus megatherium De Bary 



Bacillus petasites Gottheil 



Bacillus ruminatus Gottheil 



Group VII. Round terminal spored group 



Small, actively motile organisms, measuring 0.5 to 0.75 by 1.5 to 3ju, often 

 forming long threads in old cultures. Protoplasm homogeneous. Spores sub- 

 terminal or terminal, round, thicker than the organisms from which they spring, 

 measuring 1 to 1.5ju in diameter. 



Bacillus pseudotetanicus (Kruse) Migula 



(Bacillus pseudotetanicus var. aerobius Kruse) 

 Bacillus fusiformis Gottheil 



Group VIII. Cylindrical terminal spored group 



Small, thin, actively motile organisms, measuring 0.37 to 0.5 by 2.5 to 4/z. 

 Slightly larger on glucose agar but no change in character of protoplasm. Spores 

 terminal, cylindrical, measuring usually 0.75 by 1.12 to 1.5/*. 



Bacillus circulans Jordan 



Bacillus brevis Migula 



Bacillus terminalis Migula 



Group IX. Central spored group 



L^ng, actively motile organisms with pointed ends, measuring 0.37 to 0.5 by 

 1.12 to 4ju. Slightly larger on glucose agar, but no change in character of proto- 

 plasm. The spores develop in the middle of the rods, which become spindle- 

 shaped. The spores are large, cylindrical, measuring 0.6 to 0.8 by 1.12 to 1.5/x. 



Bacillus centrosporus Ford and associates 



Bacillus laterosporus Ford and associates 



A summary of the characteristic points of the spore-forming bacteria, 

 recognized by A. Meyer and his associates is given in table 13. 10 



Occurrence of aerobic, spore-forming bacteria in the soil. By the use 

 of gelatin plates the three most common spore-forming bacteria in the 

 soil can be readily recognized by speed of gelatin liquefaction and type of 

 colony. Except for the non-spore forming Bad. fluorescens, Bac. 

 mycoides is the most rapid liquefier; it produces large filamentous to 

 rhizoid colonies. Bac. cereus liquefies gelatin almost as rapidly as Bac. 



10 Stapp, 1920 (p. 213). 



