148 



OUTLINES OF BACTEEIOLOGY 



structure. The shape of another species, described by Hinze, is seen 

 in Fig. 85. This, on account of its motility, was named Thiophysa 

 volutans. The diameter of this form varies from 7 fi to 18 /x. This 

 group has not been extensively studied ; it is doubtful whether the 



Pig. 85. — Thiophysa volutans. (a) and (6) lu process of division. (After Hinze.) 



various species included in this group are really members of the same 

 family, in the sense of being phylogenetically connected. 



IV. Purpur-bacteria. The purpur-bacteria are characterised by 

 having a colouring matter inside the cells. The name hacteriopwrpwrin 

 has been given to this colouring matter by Ray Lankester. The 

 chief forms of purpur-bacteria are the following ; 



1. Chromatium okenii (Fig. 86a). A cylindrical cell 10-15 /i long 



and 5 /i broad. The motility of this form is due to the 

 possession of one cilium. 



2. Monas Warmingii (Fig. 86J). This is not unlike Chromatium 



okenii in appearance, differing slightly in size and shape. 



Fig. 86. — (a) Chromatium okenii ; (6) Monas Warmingii ; (c) Spirillum volutans. 

 (After Cohn.) 



i. Spirillum volutans (Fig. 86c). There is a good deal of con- 

 fusion with regard to this species. The organism commonly 

 called by this name is in reality Spirillum giganteum, which 

 does not contain sulphur, though a large quantity of fat and 

 volutin is commonly present. The species originally called 

 Spirillum volutans has never been isolated and has not 

 recently been observed. It is, therefore, doubtful whether 

 it should be included in this group. 



