Types of Aquatic Environment 



Such lakes, when their basins lie above the level of 

 the permanent water table, may sometimes be drained 

 by sinking wells through the soil of their beds. This 

 allows the escape of their waters into the underlying 

 limestone. Sometimes they drain themselves through 

 the widening of their underground water channels. 

 Always they are subject to great changes of level conse- 

 quent upon variation in rainfall. 



Enough examples have now been cited to show how 

 great diversity there is among the fresh-water lakes of 

 North America. Among those we have mentioned are 

 the lakes that have received the most attention from 

 limnologists hitherto ; but hardly more than a beginning 

 has been made in the study of any of them. Icthyolo- 

 gists have collected fishes from most of the lakes of the 

 entire continent, and plancton collections have been 

 made from a number of the more typical : from Yellow- 

 stone Lake by Professor Forbes in 1 890 and from many 

 other lakes, rivers and cave streams since that date. 



Lakeside laboratories On the lakes above mentioned 

 are located a number of biological field stations. That 

 at Cornell University is at the head of Cayuga Lake. 

 That of the Ohio State University is on Gibraltar Island 

 in Lake Erie, near Put-in-Bay, Ohio. That of the Uni- 

 versity of Pittsburgh is on the shore of the same lake 

 at Erie, Pennsylvania. The biological laboratories of 

 the University of Wisconsin are located directly upon 

 the shore of Lake Mendota, and a special Lake Limno- 

 logical Laboratory is maintained at Trout Lake. The 

 University of Florida at Gainesville is conveniently near 

 to a number of the solution lakes of northern Florida. 

 Elsewhere there are other lakeside research stations 

 among which we may mention the following: 



That of the University of Michigan is on Douglas 

 Lake in the northern end of the southern peninsula of 

 Michigan. 



