98 THE AQUARIUM. 



intended to remain, and the rest of the water should be syphoned 

 on. This is best effected by means of a piece of feeding-bottle 

 tubing, a water-can full of tap water being placed at a higher level 

 than the aquarium, such as on the top of a pair of steps, the 

 shorter end of the tube being in the can, the longer in the aqua- 

 rium. By this means the minimum disturbance of the contents is 

 effected, and the water more readily settles down bright. 



This done, the aquarium is ready for its animal life ; and in 

 the selection of the various members of the happy family no small 

 degree of care is requisite, otherwise the many are apt to suffer for 

 the benefit of the few, for numbers of aquatic insects are most 

 voracious and carnivorous, even cannibalistic in their habits. The 

 first selection should be directed to molluscs. A few water-snails 

 are indispensable ; not only do they keep the plants within bounds, 

 and by their excreta form a suitable soil for continued healthy 

 growth, but by browsing on the glass sides clean away the confer- 

 void growths, which would otherwise speedily obscure the view. 

 The best for the purpose we find to be Li?jmea auricularia^ which 

 may be found crawling on the bottom of most muddy ditches. It 

 has a very wide-mouthed shell, and is often prettily blotched and 

 marked ; its food consists almost entirely of the minute confervse, 

 which are apt to grow too luxuriantly if the aquarium is exposed 

 to strong daylight. It is preferable to the larger Limnea stagnalis, 

 which is generally recommended, for the latter will attack the 

 growing plants. Z. stagnalis is known at once by its larger size 

 and longer corkscrew-pointed shell. Another genus of useful 

 snails is Flanorbis, known by its wheel- or "ammonite "- like shell. 

 Two species — F. corneus and P. marginatus — are most frequently 

 met with, and both are excellent for our purpose. Another snail 

 is interesting, but less often come across — Paludiiia vivipara — 

 known by its resemblance to the familiar periwinkle, and, like it, 

 possessing a horny scale or shield, called the operculum, with 

 which, when the animal retires within, the mouth of the shell is 

 closed. It also has a peculiar elephant-like proboscis, at the 

 extremity of which the mouth is placed. This snail is generally 

 found upon wooden stakes or posts which stand in deepish water, 

 and may be captured by running the hand along the surface, when 

 they may be felt and detached where they cannot be seen. 



