CHAPTER IV. 



THE VEGETATION OE THE MAEINE AQTJAEIUM. 



As the forest must be planted before its denizens 

 can luxuriate in its shades, so the submarine 

 shrubbery of the Aquarium must be perfected before 

 the aquatic animals can be introduced. Por it has 

 been shown, in tracing the history of the experi- 

 ments which resulted in the establishment of the 

 principles that regulate the formation of Aquaria, 

 that it is by plants only that a supply of oxygen 

 can be kept up, suflficient for the health and 

 existence of all forms of animal life beneath the 

 water.* It is necessary, also, that the rays of sun- 

 light should fall upon the foliage directly through 

 the surface of the water ; and when an Aquarium, 

 with its plants, is placed in a position to receive the 

 light in this manner, their fronds may be observed 

 giving forth the gas in small silvery bubbles and 

 corruscations, which have a brilliant and gem-like 

 appearance. 



* Analogous principles are at work in our fields and forests, 

 but we have now only to do with, the submarine production of 

 oxygen. 



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