FEESH-WATEB AQUABIA. 235 



half-a-crown each. Ordinary propagating glasses inverted and held in 

 position by a base turned out of a block of wood make very good tanks ; 

 small hand glasses, of about four inches diameter, placed on the top 

 of hyacinth vases are also very useful, and are not unornamental. Pickle 

 bottles, earthenware pans, and other such like ordinary vessels may 

 frequently be used as auxiliaries with advantage. 



The best water to use is generally that in which the animals have 

 been found thriving, but such as is ordinarily supplied by water-works 

 is admirable for aquarium purposes, being in many casesfiltered stream 

 water. Rain water will do for many things, but pump water is to be 

 altogether avoided. 



The bottom of the tank should be covered with about an inch of 

 grit and fine gravel, on which it is well to place some pieces of rook or 

 rough stone. It is better to avoid limestone in any form, and use slaty 

 or siliceous stones only. Resting and hiding places are thus formed 

 for the animals, and plants are better preserved from being uprooted. 



I consider the American weed Anacharis Alsinastrum) the best for 

 aquaria, as none thrives so well or affords better food. It, moreover, 

 furnishes a good example under the microscope of the circulation of 

 cell contents, and the quantity of oxygen given off by it when freely 

 exposed to the sun's rays is very great, the bubbles of gas ascending 

 from it in continuous streams. The Anacharis also requires no care in 

 removing and planting; any scraps thrown into the tank will soon send 

 down rootlets from the joints and anchor themselves among the 

 gravel ; and even if any of the larger burrowing mollusks are kept in the 

 tank, the plants, though being constantly uprooted, will still con- 

 tinue to grow. Microscopic treasures are frequently to be met with 

 on it in abundance, but perhaps not so many in number as on the 

 Water Millfoil, [Myriophyllum,) which is another very good plant for an 

 aquarium. Chara and Nitella are also good. Vallisnena .spiralis is very 

 pretty and interesting, but it requires a rather deep tank, and its roots 

 must be kept properly embedded among the stones at the bottom. I 

 have kept Nitella for two years without it having at any time had its 

 roots embedded 



I have always found my aquaria do best when placed before a 

 window where they may have the direct rays of the sun for a good part 

 of the day ; the plants are thereby induced to grow vigorously, and 

 these and the pieces of rock afford ample shade for those animals that 

 require it. However, if it is not convenient to have it in such a posi- 

 tion any other will do. provided a fair amount of light can get to it. 

 There may be nevertheless a disadvantage in an excess of direct 

 sunlight. It causes the glass sides of the vessi 1 to become covered 

 with confervoid growth, which although useful both as food stuff 

 and for the evolution of oxygen, considerably obstruct the \ i 

 through the glass, a desideratum, especially if a tank microscope is 

 one of the possessions of the proprietor of the aquarium. 



Water should be added from time to time to replace what bae be< d 

 lost by evaporation and other causes, so as to keep the level about 



