THE LEUCO-THIOBACTERIA 



131 



a denser material which functions as a protective covering, 

 and in its substance are short uncoloured rods, containing 

 sulphur globules each about i|/x in thickness and about 2-5jLt 

 in length. The bacteria are confined to the surface layers 

 and in the centre the material is more fluid (Fig. 23 a and b). 



&\ . 



•^. 





a 









V. 





Fig. 23. 



a. Thiobacillus Bovistus. x 5. 



c. Pseitdomonas bipunctatus. X 1500. 



b. Thiobacillus Bovistus. 



d. Pseudoinonas retijornians. 



The slimy globules are white in reflected, and dark or blue- 

 black in refracted light. Under certain conditions the slime 

 disappears and the bacteria are set free. 



We must regard this organism as one in which the zoogloea 

 condition is permanent, that condition being probably best 

 adapted to its mode of life. The slight differentiation in the 



9* 



