THE LEUCO-THIOBACTERIA 121 



and Griffiths) ; Austria and Czecho-Slovakia (Molisch). It 

 has also been recorded from Ireland, Denmark, Russia, and 

 South Africa. Its presence has been frequently noted in lake 

 deposits of vegetable debris and diatomaceous muds ; and in 

 vegetable debris in marshes. Distribution is probably world- 

 wide. 



AcHROMATiUM MOBILE (Lauterborn), 1915. 



Syn. Microspira vacillans (Gicklhorn). 



Literature. — Lauterborn (7), 1915 ; Gicklhorn (i), 1920 ; 

 Bersa (i), 1920 ; Utermohl, 1923 ; Koppe, 1923. 



Description. — The general appearance of this organism is 

 Lauterborn placed it in the genus Achro- 

 later writers 



shown in Fig. 16 

 matium, but 

 have consideredits differences 

 sufficiently marked to merit 

 the formation of a new genus, 

 Utermohl, and Koppc 

 gave it the generic name of 

 Macromonas, and what is 

 apparently the same organ- 

 ism is described by Gickl- 

 horn (i) under the name of 

 Microspira vacillans. Pend- 

 ing a more comprehensive 



Fig. 16. — Microspira vacillans. 

 X 700. 



investigation the organism is best retained in the genus in 

 which it was placed by Lauterborn. 



Microspira vacillans {as described by Gicklhorn).* 



The organism is a single ellipsoidal cell, som^ewhat bent in 

 the middle (Fig. 16), measuring 12 — 30^^ X 8 — 14/x. It con- 

 tains numerous globules of sulphur, and in addition two or 

 three large bodies showing a bluish tinge. These, according 



* This writer's work was not available, and the statement about the 

 composition of these bodies is made on the strength of the title of Bersa's 

 work Uber das Vorkommen von kohlensaurem Kalk in einer Gnippe von 

 Schwefelbakterien. 



