’ Schuette—-Biochemical Study of Lake Mendota Plankton 595 
dividual algal specimens have been examined chemically by 
Hyams and Richards^^' by Turner® and by Whipple and Jack- 
son/ so far as is known to the writer this is the first attempt 
in this direction in which composite catches of fresh water 
plankton have been examined from a chemical standpoint. 
Material 
During the period extending from October 25 to December 
Sj 1913, five catches were obtained which were considered typi¬ 
cal of the various kinds of plankton collected during the sur¬ 
vey. Soon after the ice left Lake Monona in the following 
spring a favorable opportunity presented itself for the col¬ 
lection of a catch of Crustacea which consisted entirely of Daph- 
nia. These were then included in this study for comparative 
purposes. To date about four hundred plankton catches 
have been made. The collecting season begins soon after the 
ice leaves the lakes and closes shortly before the freeze-up. 
All samples were collected by two methods: first, by pumping 
up water from different levels of the lake and straining it 
through a plankton net, and, second, by using tow nets. In 
the former a fairly large volume of water was pumped through 
two rubber hose immersed at varying depths below the surface. 
One tube was immersed just below the surface and the other 
one meter down. With the hose in these positions tiie water 
was pumped for ten minutes. The hose were then immersed 
tv/o meters deeper and the pump again operated for ten min¬ 
utes. This successive change of level was made until a depth 
of twenty meters had been reached which was as near the bot¬ 
tom of the lake at the station where all pump catches were made as 
could be made without danger of contamination with mud. 
As the water left the pump it was strained through a very fine 
bolting cloth plankton net. The material was concentrated in the 
bucket of the net and was then washed into a jar with dis¬ 
tilled water. Representative samples of the material were re- 
2 Isabel F. Hyams and Ellen H. Richards, Notes on Oscillaria proliflca 
(Greville). Technology Quarterly 14, 302, (1901) ; 15, 308 (1902) ; 17, 
270 (1904). 
3 B. B. Turner, The chemical composition of Oscillaria proliflca. J. Am. 
Chem. Soc. 38, 1402-1417 (1916). 
* Geo._C. Whipple and D. D. Jackson, Asterionella: its biology, its chemis¬ 
try and its effect upon water supplies. Jour. N. E. Water Works Assoc. 
14, 1-25 (1899). 
