BOOKS AND CURRENT LITERATURE 137 



One of the iiuich-disciissed questions arising in the study of the 

 filter bed flora is the physiological influence of green algae on the de- 

 velopment of bacteria. It has been suggested that the oxygen liberated 

 b}' them during photosynthesis may exercise a retarding effect on bac- 

 terial growth. Decrease in nutritive supply in water due to algal 

 activity has also been advanced as a retarding influence. Hattori 

 states that in his investigations there were evident no such physiological 

 connections between algal and bacterial flora. The absence of organic 

 material in the filtered water appeared to be one of the greatest factors 

 concerned in lowering the bacterial count. 



Numerous tables are included in the paper setting forth the chemical 

 reaction and constituents of the water supplied to twelve Japanese 

 cities, the efficiency of their water systems as shown by bacterial count 

 of filtered and unfiltered water, the species of algae and bacteria found 

 during different months of the years of investigation, together with 

 weather conditions and other valuable data. There are also illustra- 

 tions of rmmerous species of algae and diatoms. — J. G. Brown. 



