THE BUTTERFLY VIVARIUM. 17 



pretty pebbles, or a little sand, on which, in spring 

 and autumn, a sprinkling of watercress-seed may- 

 be strewed, which, in the earlier period of its 

 growth, will produce the effect of a small submarine 

 lawn or grass-plot. But the plants must be taken 

 out as they begin to get large, or they would soon 

 fill up the tank. I believe I have stated, in another 

 place, that it is necessary to put in a few Pond Snails 

 to act as scavengers, by consuming all scraps of 

 decaying vegetation, and so keeping the water clean 

 and healthy ; but this point cannot be too much 

 impressed, even at the risk of repetition. 



In arranging the land portion, a layer of drainers, 

 full three inches deep, consisting of small pieces of 

 broken flower-pots, bricks, etc., should be put in, 

 before the earth is added, in order that portions of 

 the earth may remain sufficiently dry for such plants 

 and insects as would be injured by too much mois- 

 ture. The planting may then commence, according 

 to the following instructions, and, when complete, 

 the little crystal palace is ready for the reception of 

 its interesting tenants. 



Common grasses may form the staple of the 

 plantation, putting in a few nice closely-grown 

 tufty roots, and sowing grass-seed between, of the 

 smaller and low-growing kinds. Other plants may 



c 



