572 Wisconsin Academy of Sciences, Arts, and Letters. 
mately by counting the number of strokes made with the 
pump for each catch. A more accurate method of procedure 
is to place the net in a pail which bears a calibration mark 
and the desired amount of water is pumped into the net. 
At first the water is pumped into the net very slowly and 
carefully so that the organisms will not be forced through 
the meshes of the net. The end of the discharge hose should 
be held so that the stream will strike the surface of the water 
as soon as a Sufficient amount is pumped into the pail. A 
very convenient size of pail to use is a 12 quart one made 
of galvanized iron, with a 10 liter mark on the inside. Ten 
liters of water are sufficient for a catch in a lake that is rich 
in plankton but, if it is desirable to strain a larger quantity 
for a catch, the pail may be emptied and filled a second or a 
third time. 
The catch is concentrated in the bucket and is then trans¬ 
ferred to a bottle for preservation. If further concentration 
is desirable the material is transferred from the plankton 
bucket to a strainer made out of an eight dram (30 cc.) 
homeopathic vial, short form. In making the strainer, the 
bottom of the vial is removed by means of a file and a hot 
wire and a piece of No. 20 bolting cloth is tied over the 
mouth of the vial with heavy thread. Unless the catch is a 
very large one, substantially all of the water is removed 
from it and the material may be transferred from the strainer 
to an eight dram (30 cc.) homeopathic vial with 95 per cent 
alcohol. Enough water usually remains with the material 
to reduce the strength of the alcohol to 75 per cent, or 80 
per cent, which is about the proper strength for preserva¬ 
tion. 
In this method of concentration some of the smaller or¬ 
ganisms are lost through the meshes of the bolting cloth on 
the strainer, but it serves very well for the plankton Crus¬ 
tacea. If it is desirable to avoid the loss of the smaller 
organisms captured by the net, it is best to transfer the ma¬ 
terial from the plankton bucket into a wide-mouth bottle 
with distilled water and a wash bottle. Then enough 95 
per cent alcohol is added to make the strength of the mix¬ 
ture about 50 per cent. After standing a few hours most of 
the supernatant liquid may be siphoned off and the catch 
transferred to a 30 cc. homeopathic vial with 95 per cent 
