PLANTS FOR. 23 



cumstances it is essential that fresh oxygen should 

 be supplied, either by fresh water or by passing it 

 through the water. This last may be done by 

 means of a pair of bellows with an India-rubber 

 tube attached to the nozzle. An occasional blow 

 through the bellows will act as pleasantly on the 

 animals as a walk in the parks on the infant popu- 

 lation of London, or a visit to the sea-side. In 

 the Dublin Zoological Gardens, an arrangement has 

 been made by which the whole of the Aquavivaria 

 in that establishment are connected by a tube with a 

 single pair of bellows. From this long tube, branches 

 pass off, and open into each tank ; and one puff of 

 the bellows supplies air to the whole of the tanks. 

 The passing of the air into the tanks has a very 

 pretty effect, and visitors are so fond of blowing 

 the bellows, that Dr. Ball, who described this 

 arrangement at the last meeting of the British 

 Association at Cheltenham, stated that the autho- 

 rities of the Gardens had found it entirely unne- 

 cessary to employ any of the men in the Gardens 

 to pump in the air. 



CHAPTER IY. 



t 



PLANTS FOE THE AQTJAVIVARIUM. 



THE plants to be employed for the Aqua- 

 vivarium must be all aquatic plants, or those which 

 live with the greater part of their stems and leaves 

 in the water. Others may be employed to orna- 

 ment any rock-work out of the water, or to 

 ornament the sides of the Aquavivarium ; but 

 these, it should be recollected, do not supply 

 oxygen to the water, or take away its carbonic 

 acid. 



