DISTRIBUTION OF SPECIES. (59 



abyssal fauna, and in a pool the distinction between the limnetic 

 and littoral regions is lost. 



In Lake Winnebago, as I have indicated in a former paper 

 (Marsh '99, p. 181), in spite of its great size there is an inter- 

 mingling of littoral and limnetic forms. Cladocera like Eury- 

 cercus which are ordinarily considered strictly littoral are com- 

 mon in the limnetic regions, and, on the other hand, limnetic 

 forms like Diaptomus and the limnetic species of Cyclops may 

 be found in the littoral region. In this lack of distinction be- 

 tween the limnetic and littoral forms, Lake Winnebago is like 

 an enormously overgrown puddle. 



