REARING ANIMALS AND MAKING COLLECTIONS 461 



if the animals in it live naturally in quiet water. Among 

 the more available plants for use in aquaria are the fol- 

 lowing: 



" Waterweed, Elodea canadensis. 



" Bladderwort, Utricularia (several species). 



44 Water -starwort, Callitriche (several species). 



44 Watercress, Nasturtium officinale. 



44 Stoneworts, Chara and Nitella (several species of 

 each). 



44 Frog-spittle or water-silk, Spirogyra. 



44 A small quantity of duckweed, Lcmna, placed on the 

 surface of the water adds to the beauty of an aquarium. 



FIG. 168. Battery -jar aquarium. (From Jenkins and Kellogg.) 



4 4 When it is necessary to add water to an aquarium on 

 account of loss by evaporation, rain water should be used 

 to prevent an undue accumulation of the mineral-water 

 held in solution in other water. ' ' 



Making collections. Much is to be learned about 

 animals by 44 collecting " them. But the collecting 



