596 Wisconsin Academy of Sciences^ Arts, and Letters, 
moved for biological studies, a little chloroform was added to 
the remainder of the catch as a preservative, and it was then 
taken to the laboratory for evaporation. 
The other method consisted of towing behind a boat a net 
of coarser bolting cloth than was used in connection with the 
pump. Cloth of the texture used allowed the greater part of 
the plant matter to pass through and retained the Crustacea which 
are larger organisms. The nets were weighted down so that they 
sank to a level of about five feet below the surface. 
The history of the plankton catches examined follows: 
Sample 
Date of collection Source 
Method of collection 
1913 
A 
Oct. 
11 — Oct. 
25 Mendota 
Pumping 
B 
Oct. 
4 — Nov. 
1 Mendota 
Pumping 
C 
Oct. 
18 —Nov. 
5 Mendota 
Tow nets 
D 
Nov. 
l_Nov. 
5 Mendota 
Tow nets 
E 
Dec. 
3 
Mendota 
Skimming 
1914 
154 
April 
1915 
Monona 
Tow nets 
5138 
Sept. 
18 — Oct. 
2 Mendota 
Tow nets 
It will be noticed that samples to inclusive and 
5138 are composites of the catches from a number of days, a 
microscopical examination having shown that they contained the 
same organisms and for this reason they were mixed. Sample 
consists of a series of pump catches made in deep water; 
it contains a preponderence of vegetable matter. The diatom 
Fragilaria predominates. The next most abundant alga is 
Microcystis. A fairly large number of Crustacea are present. 
Sample “B” is a composite of pump catches made at the 
shore and therefore in shallow water; it contains a greater^ 
proportion of plant material than the preceding sample, Fragi¬ 
laria again being the chief constituent. Microcystis is rather 
common. A few Crustacea, are present. Samples and 
“D” are tow net catches made in the deeper waters of Lake 
Mendota; they consist^ chiefly of animal matter in which the 
Crustacea predominate. Daphnia, Diaptomus and Cyclops consti¬ 
tute by far the greater part of the material in sample ‘ ^ C. ^ ’ The 
