in ACTION OF SUNLIGHT ON WATER 97 



D. EFFECT OF SUNLIGHT ON WATER. 



(1) Fill a tall glass cylinder with tank water, and expose 

 it to active sunlight for several hours, having first removed 

 a sample from the surface by means of a sterile pipette 

 (Sample A). 



(2) Having allowed the sun to act on the water for 

 several hours, remove a second sample from the surface, 

 and another from the depth (Samples B and C). 



Now work up these three samples in the usual manner, 

 using not more than 1 to '12 cc. 



Compare the results : 



Sample A contains most organisms ; 

 Sample B fewest. 



The sun has little or no action on the Bacillus fluor- 

 escens liquefaciens, if the latter should be present 

 in the water. 



