go MIDLAND NATURALIST. 
temporarily into a jar some Utricularia. This plant has its leaves 
provided with little bladders in which entomostraca and small water 
insects are caught in large numbers and removed from the scene of 
their ravages. These little bladders are very numerous and I have 
found at times as many as half a dozen small insects captured in a 
single one. 
The jars in which filamentary algae such as Spirogyra, 
Mougeotia, Zygnema, CEdogonium and others are grown give better 
results when the bottom of the vessel is covered with about an inch 
of clear washed sea-sand. In some manner not quite evident, I 
have found that jars with sand in them are not so likely to decay 
by bacteria. To clean the sand it is sufficient to allow a stream of 
hot water to drip on it in the jar for half an hour. If the sand had 
ever been present where Oscillatoria or other Myxophyceae had 
been it should be disinfected by soaking over night in formalde- 
hyde and subsequent washing with cold and hot water in turn. 
The water which is used in the aquaria should be ordinary 
pump or tap water,—the former being preferable. If tap wáter is 
used it should be allowed to run quite a while, at least five or ten 
minutes before the jar is filled. The water standing in pipes takes 
up, especially in presence of carbon dioxide, small and often inap- 
preciable quantities of iron, lead, or other metals, in solution, pro- 
bably not from the metal, but from the ever present oxides and rust. 
These minute quantities of metallic salts are very destructive espe- 
cially to the conjugatae and unicellular plant forms. Hard water, 
or water with lime in solution is also not the best for the above- 
mentioned plants. The hardness of the water can be almost totally 
removed after a time by the introduction into the jar of one or 
several young green plants of Chava. This plant has a large per- 
centage of lime in its cell wall and cell contents, and grows best in 
water when lime is present: and it serves well to eliminate it frora 
the aquaria. This is probably the reason why Chlorophyceae in the 
presence of Chara react more promptly in accommodating themselves 
to their environment when put in the fresh water of the laboratory 
Some of the plants introduced into the laboratory jars from the 
field will take kindly to their environment if the water is not there- 
after changed and the precautions and methods of treatment as 
outlined are followed. Others will disappear for the time and later 
come back in greater or less abundance most of them passing easily 
