232 MARVELS OF THE ANIMAL WORLD 



not only will they thrive in small tanks or glass 

 bowls, but they will do equally well both indoors 

 and out in the open. Great care, however, must 

 be taken not to overcrowd them, and not more 

 than two small specimens should be placed in a 

 bowl measuring a foot across or else they will 

 probably die for lack of a sufficient supply of 

 oxygen in the water for their needs. A sure sign 

 that the water is not sufficiently aerated is when 

 the fish continually come to the surface in order 

 to take a gulp of air through their mouths ; and 

 although this state of affairs can be remedied by 

 withdrawing some of the water with the aid of a 

 syringe and then squirting it back again, yet, after 

 all, such a method is but a makeshift, and it is 

 far better to remove some of the inmates of the 

 aquarium so that those which remain may have 

 plenty of room. 



The fish are able to endure great extremes of 

 heat and cold, but for breeding purposes they do 

 best in warm water, a temperature of eighty 

 degrees, or even ninety degrees, not being too high 

 for their well-being. In factory towns they are 

 frequently kept in tanks filled with the warm water 

 discharged from the steam-engines, and although 

 the supply of water is usually cut off on Sundays, 

 with the result that its temperature becomes 

 greatly reduced (especially during the winter 

 months), and does not rise until the engines com- 

 mence working again, yet, nevertheless, the fish 

 do not appear to be in any way inconvenienced 

 thereby. In an outdoor pond they will even 



