34 Nvav Yokk Stvtk 



the resistance falls. It was not possible to determine the effect of 

 this factor on the breeding of the fish; but this is evidently a subject 

 of very great importance. 



It would be possible to bring together data concerning the effect 

 of other kinds of waste on aquatic life, but this would prolong the 

 present discussion too greatly and the instances already elaborated 

 are adequate to show the general questions involved. 1 think they 

 are also sufficient to demonstrate the value of biological tests in 

 securing a proper estimate of the effects of stream pollution, and the 

 ways in which biological studies may be utilized in the solution 

 of the problem. 



