(J4- PLANKTON OF V/INNEBAGO AND GREEN LAKES. 



some of the shallow lakes. D. Ashlandi has never been found 

 outside the Great Lakes, and certain bodies of water immedi- 

 ately connected with them. D. oregonensis is typical of the 

 shallow lakes, but occurs in some lakes that would naturally be 

 classed with the deep lakes, like Lake Mendota. 



Epischura lacustris is not confined to any class of lakes, but 

 is more common in the deep lakes. 



Lirmwcalanus macrurus is found only in the large deep lakes- 

 O'f the lakes within the limits of Wisconsin, only Green lake 

 and Lake Geneva seem to furnish the necessary environment of 

 low temperature with a certain amount of circulation. 



I have already discussed the distribution of Cyclops hrevi- 

 spinosus and Cyclops pulchellus. Of the species of Cyclops, 

 C. pulchellus is, generally speaking, characteristic of the deep 

 lakes. The other species are common to both classes of lakes. 

 C. brevispinosus, C. pulchellus, and C. prasinus are limnetic in 

 habit, C. Leuclcarti is common to both the limnetic and the lit- 

 toral regions, while C. fuscus, C. albidus, and C. serrulatus are- 

 littoral species. 



Of the cladocera, Leptodora, Daphnda hyalina, Bosmina,. 

 Diaphanosoma, and Chydorus are common to all classes of 

 lakes, but Bosmina is much more numerous in the deep lakes,, 

 and Leptodora and Diaphanosoma are found in greater num- 

 bers in the larger lakes. Daphnia pulicaria is found for the 

 most part in the small deep lakes, while Eurycercus, which oc- 

 curs in such numbers in the plankton of Lake Winnebago, i& 

 never found in the limnetic collections of the deep lakes. 



Peculiar to the abyssal fauna of Green lake are Mysis and 

 Pantoporeia which are also abundant in the abyssal fauna of 

 the Great Lakes. 



To sum up, while most of the constituents of the plankton 

 are common to all classes of lakes, some few species are confined 

 strictly to one class of lakes, while some of the others may be- 

 considered characteristic of one class, although found in small 

 numbers in other classes. The following may be considered 

 characteristic of the deep lakes: Ceratium, Notholca longi- 



