HELIX BOMBEZ. 



THE FHESH-WATEE WHELK. 



AQTJABUJM. 



best adapted for the globe. In shape it is rounder and 

 more slender than the trumpet-snail, and appears more 

 elongated or drawn out. 



Besides the above, there are two others worth mentioning — 

 the " Swan-muscle," plentiful in the NewEiver - 



and the river Lea; and the Fresh- water 

 Whelk, to be found at the bottoms of ditches. 



The accumulation of the green stuff on the 

 sides of the tank is frequently accelerated by 

 too strong a glare of light being allowed to play through 

 the sides. This may be avoided by shading the side of the 

 tank next the window 

 with green tissue paper, 

 which wiU not obstruct 

 the light, but merely 

 subdue it. Moreover, as 

 says Mr. Lloyd, "It is 

 not the mere placing of 

 a quantity of plants, 

 and then a quantity 

 of fish, &c., in a vessel 

 of water that constitutes an aquarium ; there must be dis- 

 crimination used between those plants that will thrive and 

 give off the least amount of mucous or slimy matter, and that 

 win also thrive in an artificial state, and those that wiU not ; 

 the same may also be said of the fish, &c. Quantity is also 

 another great point ; for it is to be borne in mind that the 

 object is to have such a balance as will keep the water in a 

 state of purity, so that it shaE not require changing. The 

 exact quantity of each to keep up this balance has not been 

 determined, and, indeed, nothing but actual experience will 

 demonstrate it." 



In hot summer weather the decomposition of your plants 

 win, of course, be more rapid than in mild weather — indeed, it 

 win sometimes happen that, despite the industry of your 

 scavengers, the confervce wiU accumulate too fast for them. If 

 this happens, you had better give them some assistance. Tie 

 a piece of sponge to a bit of cane, or make a little mop of wash- 

 leather, and once or twice a week pass it thoroughly over the 

 interior surface. 



Under such circumstances, too, the water will reqviire to be 

 frequently changed — how frequently you will easily under- 

 stand by its condition. While it is perfectly clear, do not touch 



