186 
mining the seasonal and local production of plankton. The 
primary source of the food of the plankton les in the water 
and in the gases and inorganic salts dissolved therein, the oxy- 
gen, the carbon dioxid, the nitrates, and the phosphates being 
usually regarded as of prime importance to the growth of chlo- 
rophyll-bearing organisms. The phytoplankton, which utilizes 
these inorganic materials, then becomes itself the food for the 
zooplankton. These inorganic substances, the primary food 
supply, are thus indices of the capacity of the water for the 
production of plankton. 
With the inauguration of the work of the Biological Sta- 
tion at Havana arrangements were made whereby collections 
of water taken by the Station staff from the river and some 
of the adjacent lakes were sent to the Chemical Department 
of the University of Illinois, at Urbana, for analysis. In 
1895 the Chemical Survey of the waters of the state was es- 
tablished at the University under the direction of Prof. A. W. 
Palmer, and in September of that year regular shipments for 
analysis from the Illinois River and from Quiver Lake were 
made at intervals of one week, and in January of the following 
year Spoon River was added to the collection points. These 
collections were continued throughout the period of our oper- 
ations at Havana. In September, 1897, collections were insti- 
tuted in Thompson’s Lake, and from that time on the samples 
for chemical analysis were taken at the same time and place 
as the plankton and, like that, by the plankton pump. After 
the date above named a fortnightly interval corresponding 
to the plankton interval was made between collections in 
Quiver Lake, though the weekly interval was continued in Ili- 
nois and Spoon rivers. August 16, 1896, a disastrous fire in the 
chemistry building of the University destroyed many of the 
records, and this fact accounts for the absence of data of the 
analyses in the months of the year prior to the fire and for 
some other gaps in the record. Special collections were made 
during the last twenty months of our operations for the deter- 
mination of the oxygen and carbon dioxid dissolved in surface 
