MOUNTING AND PRESERVING OBJECTS. 8S 



few fresh-water molluscs in to keep down the growth of 

 confervae, especially such as feed on decayed vegetable 

 matter, as Planorbis carinatus, Paludina vivipara, or Am- 

 phibia glutinosa. When bubbles of oxygen gas appear, 

 fish, water insects, etc., may be introduced. 



Marine aquaria require more skill than those for fresh 

 water, but for temporary purposes, the plan described by 

 Mr. Highley, in Dr. Beale's How to Work with the Micro- 

 scope, is excellent. He fills a number of German beaker 

 glasses with fresh sea-water, and places them in a sunny 

 window. He then drops in each one or two limpet shells 

 from which the animals have been removed, and upon 

 which small plants of Enteromorpha and Ulva are growing. 

 In a short time the sides of the jars next the light become 

 coated with spores. He keeps the other sides clean with 

 a piece of wood or sponge, so as to observe the small 

 marine animals which may now be placed in the beakers. 

 In this way a collection will keep healthy for months. 

 After the sides are covered with spores, the sea-weeds 

 may be removed, and the jars placed on a table at such a 

 distance from the window that the light impinges only 

 on the coated half, taking care that there is sufficient light 

 to stimulate the spores to throw off bubbles of oxygen 

 daily. 



Prawns, fish, actiniae, etc., may be fed on shreds of beef 

 which has been pounded and dried, and then macerated 

 in sea-water for a few minutes. All dead animals, slime, 

 or effete matter should be removed by wooden forceps, 

 etc , as soon as noticed. 



