THE CULTURE OF THE SULPHUR BACTERL4 65 



sulphur bacteria had also increased, and at its close had im- 

 parted a tinge of their colour to the various objects in the pool. 



i 6 



Time in weeks 



4 6 



Time in weeks. 



4 6 



Time in weeks. 



Fig. s. 



10 



The rise in the .hydrogen sulphide content is an indication 

 that the supply by the saprophytes was greater than the 



5 



