BACTERIA 113 



Genus : Thiothrix Winogradsky. 



The cells are non-motile and the threads are attached to some object. The 

 threads are surrounded by a delicate sheath and the cells contain sulphur granules. 

 Gonidia are produced at the end of the threads. These gonidia are motile and finally 

 attach thepiselves to some object, and, according to some authors, bend at right 

 angles in the middle and grow into new threads. 



Genus: Beggiatoa Teevisan. 



The threads are not surrounded by a sheath and are formed of flat cells. The 

 cells are not attached (Fig. 88). This genus moves by means of an undulating mem- 

 brane similar to Oscillaria. As the organism moves, it rotates on its long axis and 

 swings its free ends, (jonidia are unknown and reproduction takes place by a 

 division and separation of the threads. 



II. Family: Rhodobacteriaceas (Winogradsky's classification, artificial). 



The cells contain bacteriopurpurin and on this account may be red, rose, or violet. 

 Sulphur granules may also be included within the cells. 



I. Subfamily. ' 

 The cells are united into colonies. Cell division takes place in three directions of 



space. 



Genus: Thiocystis Winogradsky. 



The colonies are small, compact, and enveloped either singly or in groups by a 

 gelatinous cyst. The colonies are also capable of breaking up and the cells moving 

 about. 



Genus: Thiocapsa Winogradsky. 



The cells are globular in shape and spread out on a substratum in flat colonies. 

 These colonies are surrounded by a common gelatinous secretion similar to a capsule. 

 The cells are non-motUe. 



Genus: Thiosarcina Winogradsky. 



The colonies form packets similar to the genus Sarcina of the Eubacteria. The 

 cells are non-motile. 



II. Subfamily Lamprocystaceae. 



The cells are formed into families. Cell division takes place first in three then in 

 two directions of space. 



Genus: Lamprocystis Schroter. 



The cells in the beginning are solid, then hollow, becoming perforated like a net. 

 They separate into smaU groups and become motile. 



III. Subfamily Thiopediacese. 



The cells are united into colonies. Cell division takes place in two directions of 

 space. 



Genus: Thiopedia Winogradsky. 



The families are formed similar to tubes and are composed of cells arranged in 

 fours and capable of motility. 



IV. Subfamily Amoebobacteriaceae. 



The cells are united into colonies. Cell division takes place in one direction of 

 space. 



