Judaij—Limnological Apparatus. 
581 
semi-rotary, or clock pump and half-inch (1.25 cm.) garden 
hose are employed. The pump is attached to a framework 
consisting of half of a box as shown in fig. 6. The supporting 
box is made of fairly heavy boards so that the pump does 
not require an extra crate for shipment. A calibrated line 
is attached to the intake end of the hose so that the depth 
at which the water is obtained for the catch can be readily 
ascertained. 
In the spring of 1911, a study of the chemical composi¬ 
tion of the net plankton of Lake Mendota was begun. It 
requires at least 5 grams of dry plankton for an analysis 
and it is ususally necessary to strain from 10,000 to 20,000 
liters of water to obtain this amount. For obtaining large 
quantities of water from different depths, the apparatus 
shown in Plate XXXVI, figs. 1 and 2, is used. It consists of a 
small gasoline engine, the kind used in operating the ordi¬ 
nary milk separator, and two brass vane pumps, all mounted 
on a firm metal base when in operation. The engine is at¬ 
tached to the base with bolts so that it can be readily de¬ 
tached from the latter when the apparatus is put into or 
taken out of the launch. 
