276 ILLINOIS ACADEMY OF SCIENCE 



enter the stream from gas works, tanneries, and manu- 

 facturing plants above the lower falls. 



Collections made in 1892, before pollution became not- 

 ably apparent, included nine species of gastropod mol- 

 lusks, three being water breathers and six air breathers, 

 These species were identified as: 



Musculium transversum 



Musculium partumeiiim 



Bythinia tentaculata 



Planorhis trivolvis 



PJiysa gyrina 



PJiysa sayii 



Physa heterostropha ('=oneida) 



Galba catascopium 



Galba caperata 



Individuals were notably abundant, thickly covering 

 the rocks and the shore. In 1897 it was observed that the 

 sewage was increasing in volume and pollution was be- 

 coming more noticeable, the water looking like very 

 heavy, greasy dish water. The river was visited and ex- 

 amined at short intervals from 1898 to 1919. Each year 

 it was noted that pollution was rapidly increasing. In 

 1907, the water-breathing mollusks, Musculium and By- 

 thinia, had succumbed and none could be found. The 

 air-breathers, Galba, Planorbis, and Physa, still held out, 

 though reduced in number of individuals. An examina- 

 tion made in 1910 failed to discover a single living mol- 

 lusk of any species. Apparently the water had reached 

 such a state of concentrated pollution that even the air- 

 breathing mollusks, which normally come to the surface 

 to take free air, could not adapt themselves to this most 

 unfavorable environment and were either killed or com- 

 pelled to migrate down the river to a point where pollu- 

 tion was less deadly. During the following years, 1910 

 to 1913, the river was visited but no mollusks were found. 



During the summer of 1912, Mr. Gr. C. Whipple, pro- 

 fessor of Sanitary Engineering in Harvard University, 

 made a study of the effect of the sewage pollution on cer- 

 tain animal and vegetal life in the Genesee Eiver (Fisher, 



