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THE AMERICAN NATURALIST [Vol. LIV 



in this portion of the river. Seven years later, the 

 greater amount of sewage was diverted to another outlet. 

 Two years after this diminution of pollution we find that 

 the molluscan fauna has returned in as great number of 

 individuals as were found there before pollution began. 

 In other words, it required but two years (possibly less, 

 as the river was not examined in 1918, one year after the 

 conditions changed) for the river to become pure enough 

 to provide a favorable environment for molluscan life. 

 It has been reported that the sturgeon is again resorting 

 to the lower portion of the river for spawning purposes, 

 after an absence of several years, due to the heavy pollu 

 tion of the water. The rapid return to a favorable con- 

 dition is partly due to the lower falls in the river which 

 abundantly aerates the water before it is mixed with the 

 small amount of sewage now flowing into the stream. 



It may be affirmed without successful contradiction 

 that wherever sewage pollution occurs, sooner or later 

 the animal life will be affected, and finally driven out. 

 As this condition seriously concerns our food and game 

 fishes, which form so large a part of the meat food of our 

 population, it is a situation that demands immediate at- 

 tention and early remedy. That the fauna recovers so 

 <|iiickly al't.T pollution ceases is a matter of great interest 

 and satisfaction, showing what favorable returns may be 

 expected when these matters are taken up in all earnest- 

 ness by municipalities and commonwealths. 



Pollution in the Genesee River 

 Since writing the above account of the effect of sewage 

 pollution on the molluscan life of the river, Mr. John F. 

 Skinner, principal assistant engineer of the Rochester 

 Department of Engineering, who has been connected with 

 this department for upwards of twenty-eight years, has 

 kindly read the paper and has indicated several inac- 

 curacies in the historical matter, besides adding much in- 

 formation of value concerning the sewage disposal of the 

 city. The following data are all supplied by Mr. Skinner : 



