MIDLAND NATURALIST. 89 
It is, however, best to keep the Oscillatoria out of the laboratory as 
completely as possible, because if tolerated in but one jar it will 
almost unaccountably spread to all the others until it has become so 
prevalant that no plant can be raised or kept in the laboratory until 
the whole room has been thoroughly and completely disinfected. I 
have found this plant a greater enemy to the laboratory and aqua- 
rium than any and all bacteria together. The latter, as a rule, have 
definite periods of growth and for a long time their ravages are in- 
terrupted, but the Oscillatoria is always present and never ceases its 
ravages. Hot water is not sufficient to kill the plant. Some of the 
congeners of this plant are known not only to exist but actually to 
thrive in the almost boiling water of Some of the springs and 
geyser basins of Vellowstone Park. 
Bacterial decomposition can best be prevented by avoiding the 
introduction into the jar of too much of the collected specimen. 
But a small amount of any given specimen should be put into a jar, 
about a cubic inch of plant mass to the gallon. Nature will often 
subsequently grow plants in larger proportion both in laboratory 
and the field than this, but nature has also already gradually 
accommodated the plants to the environment, and this accommoda- 
tion has not been effected when we start a new culture. 
It is advisable to have small aquaria. The jars should not 
ordinarily be larger than six gallons capacity and the best results 
have been found to take place in one or two gallon vessels. Aquaria 
of twenty gallon capacity are good for raising crustacea entomo- 
straca, worms, insects and even higher animals but these are among 
the greatest enemies to the algae. Cladophora also develops beyond 
all bounds in large vessels once it has gained access, and usually 
spreads so rapidly as to choke out more desirable plants. 
Large insects in an aquarium should be removed. No good 
ever comes of their presence, and many destroy plant life. Water 
snails are very destructive and reproduce very rapidly. Good crops 
of desirable plants will result after Branchypus, or water shrimps 
have disappeared, but their presence ina jar of plants is not desirable, 
and with the organic matter which they consume they certainly 
consume a considerable amount of unicellular algae and reproduc- 
tive stages of higher algae. Entomostraca and small crustacea are 
great enemies to growth of plants and it is very difficult to get rid 
of them because of their small size. 
A good check can be put upon them, however, by introducing 
