no SULPHUR BACTERIA 



is shown in Fig. lid. The threads, except in very young stages, 

 are not uniformly thick. The following measurements were 

 obtained from a typical example : base 2/x, middle 3 — 4/x, and 

 apex i-8/i. The septa were I/a apart. 



Habitat.— Found by Molisch in sea-water from Trieste 

 containing decomposing Algse ; and by Bavendamm in similar 

 material from the neighbourhood of Berlin, and from the 

 briny wells of Sperenberg (Brandenburg, Prussia). 



Thiothrix marina (Molisch), 1907. 



Literature. — Molisch (5), 1907 ; Bavendamm, 1924. 



Description .^This species forms a white pellicle on the same 

 material as that on which 77?. aniiuJata thrives. Bavendamm 

 considers it to be identical with Th. tenuis^ that is, Th. nivea. 



The threads are relatively long and thin, being 0-8 — i'3ju, 

 thick and 130 — 300/x, sometimes up to 500/i., long. 



Thiothrix violacea (Ellis). 



In all systems of classification of the sulphur bacteria, the 

 first division is based on the presence or absence of colour. 

 This procedure is satisfactory in the majority of cases, as the 

 distinction is felt to be a natural one, and its utility is obvious. 

 The author has, however, found in Fossil Marsh, near Glasgow, 

 a coloured Thiothrix. A difficulty in the allocation of this 

 species thus arises. In its structure and life-history it is a 

 typical Thiothrix, and yet being coloured, it should find a 

 place in the Rhodo-thiohacteria. It is proposed to place this 

 organism provisionally in the genus Thiothrix, on account of 

 its obvious relationship. 



Description. — ^Violet coloured, uniformly thick filaments, 

 showing sheath-formation. Reproduction by fission, and 

 possibly by cndospores. The threads are approximately 3^ 

 thick and are found attached basally to various objects in the 

 bed of a stream containing domestic sewage. There is no 

 special anchoring cushion of slime. Transverse walls (of 

 slime) are not visible in young threads, but they appear 

 in old threads, and also in threads that have lost their 



