Huff: KESPONSK OF MICRO-ORCANJSiMS TO COl'PER SULPHATE 421 



The first treatment cut the number down to an average of about 100 

 standard units per cubic centimeter, and the second treatment elimi- 

 nated them ahnost completely. About the time of the third treat- 

 ment they increased to 100 standard units per cubic centimeter, but 

 were completely ehminated by this treatment, and scarcely a trace 

 of them occurred again until late in October when Aphanisomenon 



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Eig. 4. Effect of copper sulphate upon certain blue-green algae and protozoa. 



appeared, running at times to about 100 standard units per cubic 

 centimeter, but never found in much larger numbers. Frequent ap- 

 plication of small quantites of copper sulphate in a couple of small 

 bays found to be favorite breeding places for blue-green algae 

 doubtless helped materially in keeping these forms in check and 

 prevented their spreading to other parts of the lake. 



The only protozoa that were at all common at the weir where the 

 water leaves the lake were Ceraiium, Dinobryon, Vorticella, and 

 Uroglena. The response of these forms to the copper treatment is 



