

THE ANIMALS OF THE FRESHWATER AQUARIUM 97 



the water at the breeding season. The eggs of the two species 

 may be readily distinguished by the fact that while those of the 

 common frog float, those of the water-frog sink to the bottom 

 of the pond. In both the eggs are numerous : 1000-2000 in the 

 common frog ; 5000-10,000, it is said, in the water-frog. In 

 both cases each egg is surrounded by a sphere of jelly, which 

 diminishes the risk of drying up. Those of the common frog 

 are black and white, those of the water-frog grey and pale yellow. 

 If spawn is collected, only a small amount should be taken, and 

 it should be lifted carefully from the water so as not to damage 

 the eggs. In the ponds the eggs of the common toad may also 

 be found. These are laid in long strings, not masses, and the 

 eggs being entirely black, the whole has the appearance of strands 

 of wet wool (cf. vol. i. p 128). 



The spawn should be placed with clean water in a dish ; an 

 ordinary pie-dish does perfectly, if no aquarium be available. 



The rate of hatching varies with the temperature, but may 

 be expected from a week to a fortnight after laying. The eggs 

 do not all hatch at once, and as a general rule a considerable 

 proportion do not hatch at all. It is therefore well to remove 

 the little tadpoles as they hatch, by means of a pipette or watch- 

 glass, to a clean dish. In this a small amount of waterweed 

 should be placed, and unless the receptacle is large it is advisable 

 to change the water frequently. As the tadpoles grow older they 

 should be supplied with small pieces of meat or white of egg, but 

 if kept in an aquarium with other forms of life they will prob- 

 ably find abundance of food for themselves. The water should 

 not be allowed to get foul, and care should be taken to avoid 

 overcrowding, which induces disease. The tadpoles are very 

 intolerant of heat, and to leave a vessel containing them in full 

 sunshine in a warm room is to court disaster. If these few 

 simple rules are borne in mind there is no difficulty in rearing 

 the animals through the metamorphosis, when the little frogs 

 should be given their liberty. 



The whole course of development is completed in about three 

 months, and as in natural conditions the little frogs take the 

 opportunity of wet weather to quit their native pools, a thunder- 

 storm in the middle of summer is sometimes followed by the 

 VOL. ii. 7 



