ON THE LIMNETIC CRUSTACEA OF GREEN LAKE. 
BY C. DWIGHT MARSH, 
Professor of Biology in Ripon College . 
WITH PLATES V TO XIV. 
The investigations on which this paper is based were com¬ 
menced in August, 1893. At that time I constructed a vertical 
net, which could be closed at any depth. With this net I made 
twelve series of five meter hauls in a little more than twenty- 
four hours. My object was to determine the facts in regard to 
the diurnal migration of limnetic Crustacea,— a migration which 
I was certain, at that time, took place. The material obtained 
in these collections was carefully counted, the results tabulated, 
and reduced to percentages, and a report on the subject was 
made at the summer meeting of the Wisconsin Academy, in 
June, 1894, and a brief resume was published in the American 
Naturalist in the same year. 
So far as difference of diurnal distribution was concerned, the 
experiments gave only negative results, but certain facts in 
regard to the general vertical distribution of the different 
species came out very clearly. It seemed to me probable, how¬ 
ever, that the distribution might not be the same on different 
days, and, in all probability, would differ greatly in the differ¬ 
ent seasons. At that time, very little had been published 
in regard to the occurrence of the entomostraca in different 
seasons. It seemed to me that if a systematic series of collec¬ 
tions could be made throughout the year, the results would be 
very interesting. The matter was brought to the attention of 
the trustees of Ripon College, who recognized its importance, 
and made a special appropriation to pay the necessary expenses 
of the investigation. 
