io8 



SULPHUR BACTERIA 



nivea. The last-named investigator divided one species into 

 three on the sole basis of differences in the thickness of the 

 threads. As all these different forms were found in the same 

 medium, and as numerous intermediates were also present, 

 the subdivision of the species is not warranted. 



Fig. io. — Thiothrix nivea. X looo. 

 a, b, c- — Thiothrix nivea. Shows young filaments with slime cushions at 



the base of each. 

 d. — Thiothrix tenuis. Filament from the free end of which " conidia" are 



in process of liberation. Four of these are shown at point of separation 



from the parent filament. 



Note on the Variant forms of Thiothrix nivea. 



The following figures are supplied by Winogradsky as 

 the distinguishing marks of the three " species " mentioned 

 by him : — 



