Muttkowski—The Fauna of Lake Mendota. 433 
probably by virtue of their resistance to anaerobic conditions 
that they attain their eminence. But in every instance it is 
rather the stenoplastic species which may dominate than the 
euryplastic one. 
On the basis of physiological, physical, and biotic aspects it 
is possible to divide the lake into the various habitats listed. 
The following summary presents in briefest form the major 
evidence. The animals can be included in this summary only 
according to habitus and type, not according to species. 
28—S. A. L. 
