BACTERIA. 57 



takes place in only one plane. Usually the cells remain united together after division, 

 producing chains or diplococcus forms. No endospores have been noted. 



Genus : Micrococcus (HALLIER) COHN. 



The cells are globular and do not possess any organs of locomotion. Cell division 

 takes place in two planes at right angles. If the cells remain attached together after 

 cell division, merismopedia plates are formed. The plates give the appearance of a 

 regular flat mass of cells. No endospores have been noted in this genus. 



Genus: Sarcina GOODSIR. 



The cells are globular and do not possess any organs of locomotion. Cell division 

 takes place in three planes, all perpendicular to each other. Its cells remain attached 

 after division; cube-like packets are formed. The composition of the media some- 

 times prevents this typical cube formation. 



Genus : Planococcus MIGULA. 



The cells are globular. Cell division takes place in two planes at right angles 

 similar to genus Micrococcus. The cells of this genus are motile, possessing one or 

 two long flagella. No endospores are produced in this genus. 



Genus : Planosarcina MIGULA. 



The cells are globular. Cell division takes place in three planes as in Sarcina. 

 Cells are motile, having only one flagellum on each. Cells usually remain united in 

 twos and in tetrads and seldom form packets as Sarcina. 



II. Family: Bacteriaceae MIGULA. 



The cells are cylindrical in shape. They vary in length from short almost spherical 

 bodies to very long rods. Cell division takes place in one direction in a plane perpen- 

 dicular to the long axis of the cell. Some of the members of this family remain attached 

 together, forming threads, while others separate from each other soon after fission. 



Genus: Bacterium EHRENBERG. 



The cells are cylindrical, of longer or shorter length. Threads are frequently 

 formed. The cells do not possess any organs of locomotion. Endospores are produced 

 in some few species, but in the majority no such formation occurs. It is possible that 

 endospore formation occurs only under certain environmental conditions. 



Genus : Bacillus COHN. 



The cells are cylindrical, of longer or shorter length. The rods are sometimes 

 oval in shape. Cells are motile and possess flagella which are distributed over the 

 entire surface. Endospore formation occurs with marked regularity. The bacteria 

 in this genus are motile only during certain periods of their life. This period varies 

 greatly in length and occurs only in the vegetative stage. 



Genus : Pseudomonas MIGULA. 



The cells are cylindrical, of longer or shorter length. The cells are motile and 

 possess polar flagella. These flagella may vary from one to twelve in number. The 

 formation of endospores in this species is claimed by some. If they occur, it is ex- 

 tremely rare. Occasionally certain species in this genus form themselves into threads 

 or chains. 



III. Family : Spirillaceae MIGULA. 



The cells are wound in the form of a spiral or representing the portion of a turn of 

 a spiral. In the latter case, if the cells remain attached together in the form of a 



