lyo 



SULPHUR BACTERIA 



took the form of rod-shaped or spindle-shaped units, united 

 to form a net somewhat of the same kind as Hydrodictyon. 

 It differs from the preceding genus in the absence of a 

 well-defined substantial slime covering. The same or a 

 similar organism was found by Winogradsky, and given generic 

 rank under the name of Thiodictyon. If we accept the fact 

 of a wide pleomorphism in the sulphur bacteria we should rank 

 Thiodictyon as another instance of the phenomenon. Whilst, 

 however, it is possible that the majority of the forms observed 

 by Lankester on the caddis worms examined by him were 

 pleomorphic forms of one organism, it is also possible that 

 there may have been two or even three species present and that 

 the organism known as Thiodictyon was one of them. 



Thiodictyon elegans (Winogradsky). 

 Literature.^ A?, for the genus. 



Description. — The rods form at first a compact mass, and 

 are united to one another by their ends. Later they extend to 



Fig. 46. — Thiodictyon elegans. Rod-shaped cells in process, spread to 

 assume arrangement shown in completed state in B. X 1500. 



form a net-like arrangement (Fig. 46). Under unfavourable 

 conditions, the net arrangement is abandoned, and the units 

 move inwards so that compact formation is once more assumed. 

 Multiplication of the rods takes place by division, or a small 

 number of units may be liberated after division has taken place. 

 These grow into larger colonies. The cells are 5/i by I'^fx long 

 before division, but become longer during the course of the 

 division. They are coloured a very faint red. In the peripheral 

 plasma are a number of small sulphur granules. 



