24 



THE AQUARIUM. 



acquire limbs so the gills are absorbed, and they become 

 minature replicas of their parents. The eggs of these 

 creatures afford a capital study in embryology, for the 

 enveloping membrane is so clear that all the stages of 

 development may be clearly seen by the aid of a good lens. 



Newts may be purchased of the dealers in aquaria, or 

 what is much better, sought for in ponds ; but, when 

 introduced into the tank, provision should be made to 

 enable them to quit the water for a time when they are 

 desirous of so doing, for it must be remembered that 

 they are amphibious animals. It will also be necessary 

 to prevent their climbing out of the tank. This may be 

 effected by fastening strips of glass or perforated zinc 

 flat on the top-rail of the framework, so that they over- 

 hang for about two inches inside. 



Molluscs are very useful in the 

 aquarium, provided that care is 

 taken in the selection of species, 

 and that too many specimens 

 are not introduced. They are 



Plauorbis cornciis. i i r i i • 11 



vegetable feeders, and materially 

 assist in checking the otherwise too-rapid growth of coit- 

 fervce on the glasses. If the specimens are too large or 

 too numerous, however, they will check it altogether. 



The best species to select from are the following : — 

 Lynincea peregi'a^ Planorbis corneiis^ Plauorbis viarginatus, 

 Bithynia tentaculata, and Cyclas cornea. For large tanks 

 Lymncea stagnalis may also be used, but in small structures 

 its appetite is too great to allow the plants a chance of 

 increase ; it has also a fondness for animal substances. 

 Planorbis <:<?r;z^?/j" is popularly known as the Trumpet Snail, 

 and mostly in demand for aquaria. Planorbis marginatiis 

 is less known, though equally common. It has a very 



