54 BACTERIOLOGY. 



4. Genus: Planococcus (Migula). Single cells, 



spherical, hut usually showing aggregations 

 of two of four cells. Division in two direc- 

 tions of space. Motile organs are present 

 in the form of one or two long wavy fla- 

 gella. Endospore formation does not occur. 

 Only a few species are known of this genus. 



5. Genus: Planosarcina (Migula). Single cells, 



spherical, division in three directions of 

 space. Usually the cells remain in appo- 

 sition as diplococci or tetracocci, less fre- 

 quently as distinct packet forms. Motile 

 organs are present in the form of shorter or 

 longer flagella. Endospore formation does 

 not occur. Only three species have been 

 described. 

 2. Family: Bacteriacece. 



Cells which in their free state occur as cylin- 

 drical rods which divide only in one direction 

 of space, that is, at right angles to the long 

 axis of the cylinder. Cells may be very short, 

 so that it is difficult to differentiate them from 

 the coccacese. Division occurs in some species, 

 as far as observation has demonstrated, not in 

 the division of a cell into two daughter cells, 

 but in each large rod a number of cell divi- 

 sions in various stages are usually seen. 

 1. Genus: Bacterium (Ehrenberg, Migula). 

 shorter or longer cylindrical cells, some- 

 times threads of considerable length with- 

 out flagella. Endospore formation has been 

 demonstrated in a number of species, in 

 others it is absent. 



