450 GENERAL SYSTEMATIC BACTERIOLOGY 



and occurring in pairs. One species, Rhodothece pendens Molisch is 

 described. 



This name was also introduced by Orla-Jensen (1909, p. 334) to 

 replace the older name Thiothece, as the fifth genus of the family Rho- 

 dobaderiaceae. In this sense the name is probably invalid. 



Buchanan (1918, p. 471) included this as the fifth genus of the tribe 

 Chromatieae with the description: 



Cells usually spherical and in pairs, each surrounded by a spherical or an 

 ellipsoidal capsule. Non-motile. Cells not united into families. Cells contain 

 bacteriopurpurin and sulphur granules. 



The type species is Rhodothece pendens Molisch. 



Bergey et al. (1923, p. 404) followed Buchanan. 



Rhodovibrio. A generic name used by Molisch (1907, p. 21) to 

 include those bacteria containing bacterio-purpurin, without sulfur 

 granules, with cells short, comma shaped, actively motile by means of 

 a single terminal flagellum. One species Rhodovibrio parvus Molisch 

 is described. 



Buchanan (1907, p. 21) included this as the sixth genus of the sub- 

 family Rhodobacterioideae with the description: 



Cells short, comma shaped, free, actively motile by means of a single terminal 

 flagellum. 



The type species is Rhodovibrio parvus Molisch. 



Bergey et al. (1923, p. 407) followed Buchanan. 



Rickettsia. A generic name proposed by Da Rocha Lima (1916, 

 p. 567) for the organism causing typhus fever. The description was 

 elaborated by Arkwright, Bacot and Duncan (1919, p. 76). Enlows 

 (1920, p. 79) gives the following summary: 



Very small, 0.3 to 0.5iu by 1.5 to 2^. Morphologically like a coccus, diplococcus 

 or a short bacillus. Gram-negative. Not acid fast. Stains well by Giemsa, 

 appearing as small dots, paired cocci or bipolar staining bacilli with an unstained 

 central part. Not motile. Occurs sparsely in blood films. Not successfully 

 grown on artificial media. 



Prowazek regards this organism as a protozoon largely because it is insect 

 borne, and Da Rocha Lima seems rather inclined to this view on account of its 

 peculiar staining reactions. Arkwright, Bacot, and Duncan, however, regarded 

 its Giemsa staining reactions as quite like those of other bacteria. They con- 

 clude: "Nevertheless this class of microorganism and its associated diseases 

 appear to have sufficiently distinct characteristics to justify the retention of the 

 name Rickettsia for the present." They state that Da Rocha Lima found these 

 bodies in the midgut of lice (Pediculus humanus) fed on trench fever patients, 



