515 
prairies. Its waters are discharged into the upper end of the 
eastern arm of Quiver Lake, and are impounded for a varying 
length of time before reaching the river. No channel defined 
by the configuration of the bottom traverses the lake, and since 
its area is relatively large in comparison with the discharge of 
Quiver Creek, the tributary waters are subject to considerable 
impounding when the lake is free from vegetation. When, 
however, vegetation is abundant, a fairly well-defined channel, 
through which the discharged waters make their way with per- 
ceptible movement, is kept open through the matted growths. 
The impounding period is thus reduced for the channel water 
under such conditions. 
Collections were made in Quiver Creek, near Topeka, IIl., 
above McHarry’s mill-pond, from September 1, 1896, to April 
20, 1897, at intervals of ten days, by Mr. W. R. Deverman, who 
kindly volunteered this service for the Station. A tow-net of 
No. 20 silk was used, but no exact quantitative method was 
adopted, so that these collections are available only for quali- 
tative comparisons. 
The catch consisted largely of silt in the form of quartz 
grains and coarsely comminuted vegetable debris, with rela- 
tively few plankton organisms. 
The several catches were uniformly diluted, and ihe plank- 
ton organisms counted in a uniform fraction of a cubic centi- 
meter of the dilution from each catch. The various species 
detected and their monthly averages in numbers are given in 
the appended table. The figures have but slight quantitative 
value, though they will serve to illustrate in a general way the 
composition of the plankton and its seasonal changes, and will 
also afford a sufficient basis for a comparison of the constituent 
organisms of the plankton of Quiver Creek, Quiver Lake, and 
the river, though not for a comparison of their relative num- 
bers per cubic meter in each of the three situations. 
The plankton of Quiver Creek, as shown in the table, may 
be characterized as largely tycholimnetic, that is, composed of 
littoral species, shore-loving and bottom forms. This is seen 
