(50 PLANKTON OF WINNEBAGO AND GREEN LAKES. 



CHAPTER IV. 



DISTRIBUTION OF SPECIES. 



GEOGRAPHICAL DISTRIBUTION. 



The ease with which plankton forms can be carried from 

 place to place makes it unlikely that any lake will have a pecu- 

 liar fauna or flora. The agencies by which this distribution 

 is brought about have been fully discussed in other papers. 

 Except, then, as the physical conditions are distinctly differ- 

 ent, we should expect uniformity rather than diversity. As 

 has been intimated already, ther^ is a distinct difference be- 

 tween the constituents of the plam-.con of the Great Lakes and of 

 smaller bodies of water, and in the smaller bodies there is a 

 marked difference between the deep lakes and the shallow lakes. 

 1 have already discussed the distribution of Cyclops brevispi- 

 nosas and Cyclops pulchellus, the first, as a rule, being confined 

 to the shallow lakes and the latter to the deep ones. 



Diaptomus oregonensis is common to all the shallow lakes. 

 Diaptomus minutus is not found in Lake Winnebago and the 

 lakes immediately connected with it ; it occurs in the deep lakes, 

 but is not strictly confined to them, as it may be found in others, 

 especially in those that are further north. 



Cedar lake, Washington county, is peculiar in being, the only 

 lake in the state in which I have found Diaptomus siciloides. 

 This is common in the states to the south and west of us, and 

 it seems probable that it may be found in other lakes in Wis- 

 consin. 



Pelican lake is, I believe, the only lake of any size, which 

 does not have large numbers of Diaptomus. I made a large num- 



