146 AQUATIC MICROSCOPY FOR BEGINNERS. 



localities in his neighborhood; he must collect Ihem 

 aided only by faith and a tin dipper, and until he 

 reaches his microscope he can see them by the eye of 

 faith alone. Here the pocket-lens is a delusion. 



There is an enemy to the microscopical aquarium 

 which, when full-grown, is entirely visible to the un- 

 aided vision, and one that the collector should exile from 

 his gatherings as speedily as possible. This is the 

 water-snail. Carefully pick out every aquatic mollusk, 

 and do it quickly, if you care anything about the wel- 

 fare- 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 un- 

 welcome little fellows, and they will do as their parent 

 did; they will eat by day and by night and go on for- 

 ever, like Tennyson's brook. They will flourish at 

 the expense of the plants, which in a short time will 

 be nothing but shrgds and strings and decaying parti- 

 cles, while the aquarium will be abundantly supplied 

 with little cylindrical masses of snail excrement. If 

 the plants are wanted in good condition and conse- 

 quently the animals, carefully eject all the water-snails 

 and their eggs. This maybe done by a little daily 

 attention for a short time, when there will be no 

 further danger. If the eggs are allowed to remain, 

 the young snails will soon have the upper hand, for 

 they are too small and too easily concealed to be suc- 

 cessfully contended with. 



All the plants mentioned are useful in the micros- 

 copical aquarium, but Myriophyllum is the most desir- 

 able. It will thrive and help other plants as well as 



