SPIRILLUM RUBEUM 177 



a wine-red colour, which, however, does not extend to the 

 surface, and hence the pigmentation does not appear to de- 

 pend on the action of oxygen. Light exercises an inhibitory 

 influence on its production. On agar a white layer first 

 forms, which later becomes rose-red. Only small red islets 

 appear on potato ; in bouillon growth occurs, as also in the 

 water of condensation from serum. The microbes grow 

 both at room temperature and that of the incubator. 



