28 Bacteria 



BACTERIA. 



1. Family COCCACE^E. Cells globular, becoming slightly elongate 



before division. Division in one, two, or three directions of 

 space. Formation of endospores very rare. 



(A) Without flagella. 



1. Streptococcus. Division in one direction of space, producing 



chains like strings of beads. 



2. Micrococcus. Division in two directions of space, so that 



tetrads are often formed. 



3. Sarcina. Division in three directions of space, leading to the 



formation of bale-like packages. 



(B) With flagella. 



1 . Planococcus. Division in two directions of space, like micro- 



coccus. 



2. Planosarcina. Division in three directions, like sarcina. 



2. Family BACTERIACE^E. Cells more or less elongate, cylindric, and 



straight. They never form spiral windings. Division in one 

 direction of space only, transverse to the long axis of the cell. 



(A) Without flagella. 



1. Bacterium. Occasional endospores. 



(B) With flagella. 



2. Bacillus. Flagella arising from any part of the surface. 



Endospore-formation common. 



3. Pseudomonas. Flagella attached only at the ends of the cell. 



Endospores very rare. 



3. Family SpiRiUvACE^. Cells twisted spirally like a corkscrew, or 



representing sections of the spiral. Division only transverse 

 to the long diameter. 



1 . Spirosoma. Rigid ; without flagella. 



2. Microspira. Rigid ; having one, two, or three undulating 



flagella at the ends. 



3. Spirillum. Rigid ; having from five to twenty curved or un- 



dulating flagella at the ends, 



4. SpirochcKta. Serpentine and flexible. Flagella not observed ; 



probably swim by means of an undulating membrane. 



4. Family MYCOBACTERIACE^. Cells forming long or short cylindric 



filaments, often clavate-cuneate or irregular in form, and at 

 times showing true or false branchings. No endospores, but 

 formation of gonidia-like bodies due to segmentation of the cells. 

 No flagella. Division at right angles to the axis of rod in fila- 

 ment. Filaments not surrounded by a sheath as in Chlamydo- 

 bacteriaceae. 



1. Mycobacterium. Cells in their ordinary form, short cylindric 



rods often bent and irregularly cuneate. At times Y- 

 shaped forms or longer filaments with true branchings 

 may produce short coccoid elements, perhaps gonidia. 

 (This genus includes the Corynebacterium of Lehmann- 

 Neumann.) No flagella. 



2. Actinomyces. Cells in their ordinary form as long branched 



filaments; growth coherent, dry or crumpled. Produce 

 gonidia-like bodies. Cultures generally have a moldy 

 appearance, due to the development of aerial hyphae. No 

 flagella. 



5. Family CHLAMYDOBACTERIACE^. Forms that vary in different 



stages of their development, but all characterized by a sur- 

 rounding sheath about both branched and unbranched threads. 

 Division transverse to the length of the filaments. 



