282 NATURE STUDY AND LIFE 



feeding first on the gelatinous matter of their envelope, 

 they soon begin to eat the slimes in the aquarium and 

 grow with great rapidity ; hind legs appear, fore legs 

 come, the tail is absorbed, and the little toads emerge from 

 the water, all within little more than a month from the 

 time the eggs are laid. 



To do this in the schoolroom, have some of the chil- 

 dren arrange two or three aquaria (glass, earthenware, 

 wood, or iron may be used, but tin, lead, zinc, galvanized 

 iron, copper, and other metals should be avoided, since 

 they may poison the water and kill the tadpoles) as nearly 

 as possible like the pond from which the eggs are taken. 

 Have the water not more than two to four inches deep in 

 the deepest part, and let the bottom slope up gradually 

 to the surface at one end. This will enable the tadpoles 

 to find any depth of water they wish and afford a place 

 for them to come out gradually into the air at the proper 

 time. In fact, the bottom of the aquarium may be made 

 of sand, gravel, and moss-covered stones from a fairly 

 clean pond. It is necessary also to have plenty of green 

 algae and water plants, duck's-meat, stonewort, bladder- 

 wort, milfoil, water cress, or the like, to oxygenate the 

 water properly, furnish food, and take up the excretions of 

 the growing tadpoles. If the aquarium is large enough, 

 a water hyacinth is an excellent plant to have growing 

 in it for this latter purpose. If the tadpoles do not keep 

 the water perfectly clear, a fresh-water mussel or two 

 will accomplish this. Give them a window with sunlight 

 a good part of the day ; as they grow, let the children 

 carry any surplus back to the pond, and avoid over- 

 crowding by allowing about an inch of water surface to 



