RHODO-THIOBACTERIA 163 



are enveloped in slime (Fig. 40), but they differ in being globular 

 in shape. They are arranged either as diplococci or as short 

 chains. Each cell measures 1-8 — 2-3/x in diameter, and its 

 slimy envelope 3 — 14/x.. Single cells do not show colour. The 

 colouring matter is stated to be a mixture of bacteriopurpurin 

 and bacteriochlorin (see Chap. XIII.). The cells are non- 

 motile. One species is known, Rhodothece pendens. 



Genus 3. — Rhodothiosarcjna (Ellis). 



Literature.- — Winogradsky (2), 1888 ; Schroeter (i), 1889 ; 

 Migula (3), 1897; Issatchenko (2), 1914; Bergey, 

 1923 ; Bavendamm, 1924. 



One species in the genus. It corresponds to the Sarcina 

 of the Euhacteriacece, but differs from that genus in being 

 coloured, and in containing sulphur. The formation of 

 packets of cocci, resembling bales of cotton, is a distinctive 

 feature. So far as is known the organisms which are made 

 up of packets of cocci in regular formation do not exhibit 

 pleomorphic variations. 



Rhodothiosarcina rosea (Schroeter), Ellis. 



Described under the name of Sarcina rosea by Schroeter. 

 Cells 2 — 2"5jU. in diameter. Bright rose-red in colour. 

 Habitat. — In water containing H2S in solution. 



Family 5. — Thiocapsacem (Winogradsky). 



Literature. — Winogradsky (2), 1888. 



Coloured sulphur bacteria, each being a community of 

 independent cocci enclosed in a common envelope of slime. 

 The members of this group are perhaps phases in the life- 

 histories of other organisms. 



Remarks on the Division of Cocci. 



It has been shown in Chap. VI. that organisms which 

 normally form clusters of globular cells, and apparently divide 

 in three planes, may under certain circumstances appear as 

 uni- and diplo-cocci, when the number of planes in which 

 division occurs is impossible to determine. Among the 

 Euhacteriacece an organism made up of cocci disposed in 



