FRESH-WATER AQUARIUM. 63 



succession in the week and onr tank is exposed to the sun's 

 rays for three hours each day near an open window, we 

 may then, with safety, introduce the fish, whilst, in dull 

 weather, it will require longer preparation. 



Let it be always borne in mind, that the smaller the fish, 

 the easier it will be to keep them properly and without 

 trouble. Large fish, that is to say, fish of over five inches 

 in length, arc too large for any but a tank of four or five 

 feet in length, and arc more apt to die from the unnatural 

 confinement than smaller ones. I have also found that 

 small fish, after being caught, and before introduction into 

 an Aquarium, will bear travelling any distance better than 

 large ones. 



Fish are known from living entirely in the water; hence, 

 such animals as came out of the water at any time, for 

 instance, frogs and lizards, cannot be termed fish, but 

 belong to a .class that has been named Amphibia. Fish arc 

 provided with orgaus of respiration, called gills, that ob- 

 viate the necessity of their coming out of the water to 

 perform the process of breathing; so that if, in an Aqua- 

 rium, we observe the fish come to the surface to breathe, 

 as gold-fish will when kept in a globe, we may be sure that 

 something is wrong; either the animals arc in too great 

 number for the dimensions of the tank, or there is not 

 sufficient vegetation to supply the oxygen for their suste- 

 nance. 



The following arc the fish that will be found most suit- 

 able for a fresh-water collection. I have tried many of 

 them, and can recommend these : 



The gold carp (Cyprinus auratus). is one of the hand- 



