567 



Table III 



Indicating the relative resistance of the more common species of fishes to be 

 taken in the tcaters of Northern Illinois, together with data as to the best type 

 of ecological environment for each species. In column 2 the resistance of the least 

 resistant species is arbitrarily taken to be unity. 



While in Table III only eighteen species of fishes are listed, the 

 comparative resistance of other species may be estimated by compar- 

 ine- their resistance with that of some one of the listed si)ecies. By 



