1010 THE STORY OF THE UNIVERSE 



It is well known that frogs and toads generally go 

 in the spring to lay their eggs in streams and ponds. 

 A batrachian of Brazil and the hot regions of South 

 America, the Cystignathus ocellatus, no doubt fearing 

 too many dangers for the spawn if deposited in the 

 open water, employs the artifice of hollowing, not far 

 from the bank, a hole the bottom of which is filled by 

 infiltration. It there places its eggs, and the little 

 ones on their birth can lead an aquatic life while 

 being guaranteed against its risks. 



Many beings live permanently in a burrow; rep- 

 tiles snakes or lizards are to be placed among 

 these. Among others, the Lacerta stirpium arranges 

 a narrow and deep hole, well hidden beneath a 

 thicket, and retires into it for the winter, when cold 

 renders it incapable of movement and at the mercy 

 of its enemies. Before giving itself up to its hibernal 

 sleep, it is careful to close hermetically the opening 

 of the dwelling with a little earth and dried leaves. 

 When spring returns and the heat awakens the rep- 

 tile, it comes out to warm itself and to hunt, but never 

 abandons its dwelling, always retiring into it in case 

 of alarm and to pass there cold days and nights. 



Darwin has observed and described how a little 

 lacertilian, the Conlophus subcristatus, conducts its 

 work of mining and digging. It establishes its bur- 

 row in a soft tufa, and directs it almost horizontally, 

 hollowing it out in such a way that the axis of the 

 hole makes a very small angle with the soil. This 

 reptile does not foolishly expend its strength in this 

 troublesome labor. It only works with one side of 

 its body at a time, allowing the other side to rest. 



