298 THE MICROSCOPE. 
the collector should exile from his gatherings as speedily as pos- 
sible. This is the water snail and all its relatives. Carefully 
pick out every aquatic mollusk, and do it quickly, if you care 
anything about the welfare of the aquarium. Also search for 
those little jelly masses in which the eggs are deposited, and 
eject them as speedily. These hatch out in a warm room with 
surprising alacrity, and before the microscopist knows it the 
aquarium will be swarming with the unwelcome little fellows, 
and they will do as their parent did; they will eat by day and 
by night and go on forever, like Tennyson’s brook. They will 
flourish at the expense of the plants, which in a short time will 
be nothing but shreds and strings and decaying particles, while 
the aquarium will be abundantly supplied with snail excrement. 
If the plants are wanted in good condition and consequently the 
animals, carefully eject all the water snails and their eggs. This 
may be done by a little daily attention for a short time, when 
there will be no further danger. If the eggs are allowed to re- 
main, the young snails will soon have the upper hand, for they 
are too small and too easily concealed to be successfully con- 
tended with. 
All the plants mentioned are useful in the microscopical 
aquarium, but Myriophyllum is the most desirable. It will thrive 
and help other plants as well as animals to thrive. Its finely 
divided leaves afford a shelter for innumerable forms of life. 
They are an excellent place to seek for Diatoms and various 
Algee; indeed among them are to be found representatives of 
the fresh water microscopic creatures, both vegetable and animal, 
Ceratophyllum comes next so far as desirability is concerned, and 
after it there is little choice among the larger aquatic plants. 
When caught, how are the creatures to be studied? A famous 
artist was once asked how he mixed his brilliant colors. “ With 
brains, sir,” he said ; “ with brains.” Microscopic creatures are to 
be studied in the same way. 
There are many complex devices afforded to facilitate this 
object, all of which may be commendable for their special pur- 
poses, but the simpler the device the better are the results, as a 
rule, and the more easily managed they are the more satisfactory. 
Many are to be found in the books, but the three little contriv- 
ances which I described in THE Microscope for May, 1887, are 
all that I have in use for every kind of microscopic life, and I 
have found them all that are needed. 
