No. 631] 



ANIMAL LIFE AND SEWAGE 



1 53 



ural History Survey under the direction of Dr. S. A. 

 Forbes, for the purpose of ascertaining the effect in the 

 Illinois Eiver of the large volume of polluted water from 

 the Chicago Drainage Canal, into which all of the sewage 

 of the city of Chicago is discharged. 2 In other places, 

 studies of a similar character are being carried on. 



In New York State, the Genesee River, at Rochester, 

 has afforded a striking example of stream pollution, of 

 the effect of this pollution on the animal life in the river, 

 and of the final return of this life after the amount of 

 pollution was notably reduced. It has been the writer's 

 good fortune to visit Rochester every two or three years 

 (sometimes oftener) and to be able to study the condition 

 of the Genesee River during a period of nearly thirty 

 years. Collections were made before, during, and after 

 pollution, permitting comparisons to be made of the life 

 in the river during these several periods of varying con- 

 ditions. 



The animal life in a body of water has been little used 

 as an indicator of the degree of pollution. Fish, espe- 

 cially young fish, have been used and are good indicators 

 because they cannot live in water polluted to any large 

 degree. The relative resistance of different species of 

 fish has been well shown by Shelford in a recent paper. 3 

 The writer is convinced that mollusks are also good in- 

 dicators of degrees of pollution. The intimate relation 

 of fish to the propagation of river mussels (Unionidae), 

 so largely used in the manufacture of pearl buttons, is 



also seriously affected by stream pollution. 



The polluted portion of the Genesee River studied 

 (which was also the place of maximum pollution) lies 

 below the lower falls (Driving Park Avenue bridge), a 

 large sewer discharging some distance below these falls 

 just above the spot known locally as Brewer's landing, 

 near Norton Street, on the east side of the river. Several 



2 See Forbes and Richardson, "Some Recent Changes in Illinois Biology," 

 Illinois Natural History Survey, Bulletin, XIII, pp. 139-156, 1919. 



3 Bull. XIII., Hi. Nat. Hist. Surv., pp. 25-42, 1918. 



