228 FISH CULTURE 



vourable circumstances, and would hold them 

 for a year. A pond sixty by twenty feet de- 

 veloped only 10,000 green frogs. 



Ordinarily, tadpoles of the common bull- 

 frogs hatched one season do not develop into 

 frogs until late in the spring, or early in the 

 summer, of the following year; therefore the 

 bottom of the tadpole pond should in this case 

 have soft mud, at least a foot or two deep, and 

 also grasses as resting places for the tadpoles. 

 Tadpoles develop into frogs more quickly, and 

 with less danger of loss, when they have some- 

 thing on which they may occasionally rest. 



Leopard frogs spawn in April and the eggs 

 are fertilised as they issue from the female. 

 They pass from her in a string-like mass that 

 almost instantly combines into a ball, which in 

 a short while is from three to four times the 

 size of the frog. Each egg is surrounded by 

 a nearly colourless, gelatinous material, in 

 which each egg is plainly discernible, and is 

 black in colour when perfectly fresh. There 

 are about 3,500 to a liquid quart. As the eggs 

 approach development there occur several 

 marked changes in colour. Sometimes the 



