188 Marsh—Limnetic Crustacea of Green Lake . 
Of plants, the only one besides diatoms, which occurred in 
any abundance was the Anahaena already mentioned. In 1896 
this appeared in the latter part of June, and continued well 
through August. In other years, I have found it present only 
during a very short time. I have notes also of a red alga that 
was found in considerable abundance about the middle of 
August. In one of the March collections there was also an un¬ 
determined green alga. 
Rotifera were of course present in large numbers, but no at¬ 
tempt was made to keep any record of them. Notholca longi- 
spina was found throughout the year, sometimes in great abun¬ 
dance. 
Ceratium occurred quite constantly in the collections from 
June to the latter part of October, and in 1896, until the middle- 
of November. 
From May throngh the year, Diptera are occasionally found 
in the collections. This is what one would expect, for the 
larvae are found in the bottom fauna. 
METHOD OF COUNTING. 
The method used in counting was somewhat different from 
that used by other authors, and a method that perhaps could 
not be used so successfully in collections containing a large 
amount of vegetable material. The alcohol in the bottles was 
largely replaced by glycerine in order to have the material in a 
medium that would not evaporate rapidly. I had prepared for 
me a glass plate sixteen centimeters in diameter, ruled with con¬ 
centric circles a centimeter apart. The circles were divided by 
diameters a into eight segments. The plate was mounted on 
a tripod such as is used in leveling gelatine plates in bacterio¬ 
logical work, and carefully leveled. The collection was then 
poured as nearly as possible upon the exact center of the plate. 
Ordinarily it would spread with great uniformity upon the 
plate. The fractional part of the whole counted depended upon 
the numbers of the species under consideration. Commonly I 
counted only one-eighth of the JDiaptomi. Of the species present 
in smaller numbers, I would ordinarily count all on the plate. 
In any case all parts of the plate were examined in order to de- 
