62 THE AQUARIUM. 



adjustment of certain relations between the animal 

 and vegetable kingdoms, very important to our pre- 

 sent purpose. Two small gold-fish were placed in a 

 glass receiver, a small plant of Valisneria Spiralis 

 being planted at the same time in some earth, be- 

 neath a layer of sand in the same vessel. All went 

 on well by this arrangement, without any necessity 

 for changing the water ; the oxygen given off by the 

 plant proving itself sufficient for the supply of its 

 animal co-tenants, and the water therefore remaining 

 clean and pure, until some decayed leaves of the 

 valisneria caused turbidity. To remedy this evil, he 

 brought to bear the results of previous observations 

 on water in natural ponds under analogous circum- 

 stances ', and, guided by these observations and their 

 results, he placed a few common pond-snails in the 

 vessel containing his gold-fish and plant of valisneria. 



" The new inmates, immediately upon their intro- 

 duction, began to feed greedily upon the decaying 

 vegetable matter, and all was quickly restored to a 

 healthy state. They proved, indeed, of still further 

 advantage, for the masses of eggs which they depo- 

 sited evidently presented a kind of food natural to 

 the fishes, which was eagerly devoured by them, so 

 that the snails became not only the scavengers, but 

 also the feeders of the little colony. And so this first 

 of true aquaria prospered; the animals and plants 

 proving of mutual value and support to each other. 



"By the culture of some of our most beautiful 

 fresh- water plants, in glass aquaria, many of the wild 

 beauties of Nature, in some of her most pleasing and 



