1 86 BACTERIOLOGY. 



produced by Micrococcus prodigiosus, being peach- 

 blossom red, and insoluble in water, alcohol, etc. 

 Examined spectroscopically it shows a strong ab- 

 sorption in the yellow, and a weaker band in the 

 green and blue, as well as a darkening in the more 

 refrangible half of the spectrum. In the cocci, 

 especially of the older vesicles, dark granules are 

 to be seen, which consist of sulphur. The micro- 

 organisms occur on the surface of marshes, or on 

 water in which algae are rotting. They form a 

 rose-red, blood-red, violet-red, or violet-brown 

 scum ; and sometimes in such quantity that whole 

 marshes and ponds may be coloured blood-red by 

 them. 



Beggiatoa mirabilis, Cohn. Threads dis- 

 tinguished from others of this genus by their 

 breadth, which may reach 30 \L. They are motile, 

 bent and curled in various ways, and rounded at 

 the ends. Around the threads isolated cells have 

 been observed, " macrococci," but spiral forms are 

 as yet unknown. The threads are filled with 

 sulphur granules. They occur on sea water, form- 

 ing a white gelatinous scum on decomposing 

 alg^e, etc. 



METHODS OF EXAMINING SPECIES OF BEGGIATOA. 



The articulation of the threads is best demonstrated by 

 staining with an alcoholic solution of methyl-violet, fuchsine, 

 or vesuvin ; or by treating with sodic sulphate, or warm 

 glycerine. 



