144 SULPHUR BACTERIA 



formation that he observed at a depth of 13 metres in Lake 

 Mohilni. He adduces this fact, together with the fact that 

 sulphur bacteria collect round an algal filament which is 

 liberating oxygen, in proof of his contention that the genus 

 Chromatium is aerobic and not anaerobic, as reported by 

 Bredemann. 



[d) Chromatium Okenii forma gracile. 



Syn. Chromatium gracile (Strzeszewski). 



Literature. — Strzeszewski (i), 191 3. 



Ellipsoidal cells 2 — 6ft X I — 1*3/^. Single cells appear 

 colourless, but in masses, red. 



Habitat. — Sulphur springs in Krakau (Poland). 



Chromatium Warmingi (Cohn), Migula. 



Literature. — Cohn (10), 1875 ; Warming, 1875 ; Engel- 

 mann (10), 1888 ; Ewart, 1897 ; Bavendamm, 1924. 



Description.— This is a doubtful species. The name is 

 usually given to a Chromatium with the measurements 15 — 20/x, 

 X 8)u.. The shape is thus slightly different from that of the 

 normal Chromatium Okenii. Cohn named it after Warming, 

 but Warming himself sketches it as one of the many forms 

 assumed by Bacterium sulfuratiim. It is also claimed that its 

 motility is greater than that of Chromatium Okenii. Each 

 individual has a single large polar cilium, which is probably 

 compound. Bavendamm states that sulphur globules collect 

 in the cells only during division, when they increase in numbers, 

 and travel to the opposite ends of the dividing cells. Baven- 

 damm succeeded in obtaining pure cultures of this organism, 

 and as the cells in such cultures differed in size from the normal, 

 he named this variant Chromatium W armingii forma minus. 

 The same investigator also observed the development of buds 

 which in some cases had extended their lengths, and become 

 attached to similar buds from neighbouring cells. The pro- 

 cess is regarded by this writer as being possibly the first 

 phase of a sexual method of reproduction (see Fig. 29). The 

 probability is greater that the formation of the buds is a new 



