74 



COMMUNITIES OF LARGE LAKES 



and bottom. Accordingly the conditions on the bottom at various 

 depths are roughly shown in Table IX. 



TABLE IX 



I. THE LIMNETIC COMMUNITY 



(Station i ; List I) 



Chicago is famous for its good water supply. However, if one fastens 

 a small sack of miller's bolting-cloth under an open water tap for an 

 hour in summer and examines the contents of the sack with the naked 

 eye and then with the microscope, he will be of the opinion that he has 

 not been straining drinking water but stagnant ditch water. He finds 

 small microscopic plants in great numbers (75), as well as large numbers 

 of small animals, most of the larger ones dead. Every person drinking 

 water from a lake or river drinks the small plants and animals. If 

 every one of the 2,000,000 persons in Chicago drank a quart of unfiltered 



by the United States Fish Commission, and Doctor Stimpson of the Academy pub- 

 lished a brief note on the invertebrate forms found in the lake, but never gave more 

 than a hint of the work, as the collections were all burned with the Academy's build- 

 ing. Subsequently, collections were made by the State Laboratory of Natural His- 

 tory, and later by the Fish Commissioners of Michigan. In the summer of 1902, the 

 University of Chicago and the Academy of Sciences made a single-day excursion, 

 but no report was ever published. 



