The meaning of other combinations of symbols will be obvious 

 to the reader. 



Acknowledgments 



The \jriters were fortunate in obtaining the assistance of 

 experts in the identification of certain groups of organisms. The 

 Sphaeriidae were identified by Dr. Victor Sterki, Nev; Philadelphia, 

 Ohio; various other molluscs bj'- J. P. E. Morrison, University of 

 Wisconsin; the Hirudinea by Dr. John A. Miller, of Ohio State 

 University; and the Oligochaeta bj"- Dr. Frederick H. Krecker of Ohio 

 University. Specimens of Cambarus propinquus were identified by 

 Dr. Edwin P. Greaser of the Musseum of Zoology, University of 

 Michigan. The valuable contributions of these investigators are 

 gratefully acknowledged. 



Data and discussion 

 Qualitative data 

 Organisms taken in quantitative dredges 



Nematoda 



1. Nematoda , 



Oligochaeta 



2. Tubifex sp. 



3. Limnodrilus sp , 



Hirudinea 

 h. Herpobdella punctata (Leidy) 



5, Dina fervida (Verrill) 



6. Glossiphonia stagnalis (Linnaeus) 



7. Glossiphonia fusca Gastle 



8, G'lossiphonia nepheloidea (Graf) 



256 



