124 SULPHUR BACTERIA 



Description. — The cells are ellipsoidal, sometimes pointed, 

 or considerably flattened. The membrane is sharply defined, 

 and the plasma is made up of delicate strings which traverse 

 the whole cell. In some the plasma may be massed all at one 

 end, leaving a large vacuole in the remainder of the cell. The 

 sulphur globules are soluble in 90 per cent, alcohol, and 

 insoluble in hydrochloric, nitric, and acetic acids. Also, the 

 peripheral plasma contains dull green, round, or oval, or some- 

 times angular, plates of varying sizes. The poorer the cells 

 become in their content of sulphur, the more numerous are 

 these plates. They are regarded as some form of reserve 

 material. The cilia are numerous, and peritrich, each about 

 a third of the length of the cell, and o-Jix in thickness. Re- 

 production is by transverse fission. 



Hinze distinguishes two species : — 



Thiovuhtm majus, between 1 1 X 9fx and 18 X iJix. 

 ,, minus ,, g-6 x 7-2/x and 11 x gfji. 



Thiovulum Mulleri (Warming). 



Literature. — Warming, 1876 ; Migula (3), 1900 ; Molisch 

 (5), 1912 ; Hinze (6), 1913 ; Bavendamm, 1924. 



Description. — In 1876 Warming described and depicted an 

 organism, which he named Monas MiiUeri, that belongs 

 indubitably to the same group as Thiovulum. Thus the 

 generic name Monas * has prior claim, but as this name is 

 already applied to a genus of one of the Flagellate groups, it 

 may conveniently be ignored. 



The cells are ellipsoidal or globular (Fig. 18). Tire size 

 varies from 6'3ju. to i2-8ju. in length, and from 5-6/x to 15/x in 

 breadth. Hinze has recommended that the species Thiovulum 

 MiiUeri be limited to such members as are within the dimensions 

 4*9 — I2ju,in length. The suggestion is not to be recommended, 

 for there is obviously no specific distinction between the micm- 

 bers of these dimensions and those immediately shorter or 



* Monas. — The term is applied to a division of Flagellates, a group which 

 is divided according to the number and position of the flagella or cilia. 

 The genus Monas is distinguished by the possession of one flagellum. 



