20 PLANKTON OF WINNEBAGO AND GREEN LAKES. 



I have, however, found it in other lakes in the summer. It 

 occurred in August, 1901, in both Shawano and Stone lakes 

 in small numbers. In August of both 1900 and 1901 it was 

 found in large numbers in Birch lake, I have found it also in 

 Cedar lake in March and June. It is evident then that Anuraea 

 aculeata may occur at any time of the year, and I see no reason 

 why in Lake Winnebago it should be limited to the colder 

 months, for the conditions of Shawano lake are very similar 

 to those of Lake Winnebago. 



Anuraea quadridentata Ehrenberg. 



Anuraea quadridentata I have not found in Lake Winnebago. 

 It appeared in Green lake in 1901 from February through the 

 month of April. 



Polyarthra platyptera Ehrenberg. 



Polyarthra is a perennial form in Lake Winnebago. Gen- 

 erally speaking the numbers are greater from July to October, 

 but in one year there was a very large production in February 

 and March. 



In Green lake it occurs from June through the month of 

 October. I have never found it in the winter months. 



The European authors speak of Polyarthra as a perennial. 

 The occurrence in Green lake would seem to be somewhat pecu- 

 liar, and I cannot see what circumstances in Green lake should 

 be more unfavorable to it than in Lake Winnebago. 



Triarthra longiseta Ehrenberg. 



Triarthra is never found abundantly in either lake. In 

 both it is found from June to November, and only occasionally 

 in the winter months. 



Notholca longispina Kellicott. 



NotJiolca longispina is much more numerous in Green lake 

 than in Lake Winnebago. In both lakes it may occur at any 

 time of the year, with no pronounced maximum period. The 

 largest single collection in Green lake was in February, 1900. 



