US GENERAL MANAGEMENT OF 



bo disposed to perform their duty of cleaning the glass, 

 therefore, we must assist them ; and for this purpose, as 

 I have before mentioned, I have found a good instrument 

 to be a piece of sponge attached to the end of a rod 

 of wood, with which we can scrub the glass to our satis- 

 faction, until it assumes a clearness that allows us to 

 observe the habits and motions of the contained animals. 

 The glass will sometimes, if neglected for any length of 

 time, be found to have young shoots of Ulva or Entcro- 

 morpha growing upon it ami which sometimes the sponge 

 will not sufficiently remove. We can then use a brush, 

 such as a tooth or nail brush, for this purpose. 



Often, if we happen to have several dull days without 

 sufficient sunshine, we shall observe the plants and ani- 

 mals to assume a sickly appearance, the fish coming to 

 the surface to breathe, and everything looking bad ; and 

 things will continue to get worse if not attended to. 

 The water will, on such occasions, need aerating ; and 

 this can be done cither by taking some out with a pitcher 

 and pouring it back, or, still better, by having a con- 

 trivance which I have used for the purpose for some 

 time. It consists of a chemist's bell-glass that has a 

 hole at the "end, usually occupied by the knob, into which 

 we insert a cork that is perforated with a hole and has 

 a piece of glass tube fixed in it. This glass tube is 

 turned downwards as the glass stands at an acute angle 

 and is drawn out to a fine point, so that it allows the 

 passage of only a small amount of water. We now invert 

 the bell-glass, and, suspending it over, fdl it with water 

 removed from, the tank. The water is at once forced, by 



