432 CLASS REPTILIA. 



the eggs of birds. These eggs swell greatly in the water 

 after being laid. The experiments of Spallanzani have 

 proved that they could support thirty-five degrees of heat 

 without undergoing any alteration, and without ceasing to be 

 productive. 



The frogs feed on the larvae of aauatic insects, on worms, 

 small mollusca, flies, &c., and always choose a prey which is 

 living and in motion. Every dead or motionless animal is 

 rejected by them. To obtain this prey, they remain fixed in 

 one situation with wonderful patience, watching it until they 

 believe it to be sufficiently near : then they dart upwards, 

 with the rapidity of lightning, putting out their tongue to 

 catch it by means of the viscous fluid which invests that 

 organ. This fluid retains it, while the two points of the bi- 

 furcation of the tongue seem to twist around it. When this 

 prey is once thus seized, it is speedily swallowed. According 

 to Daudin, the frogs sink it into the oesophagus with the 

 thumbs of their anterior extremities. Sometimes, however, 

 this gluttony is punished. Roesel presented a wasp to a 

 frog which he had reared. The reptile immediately swallowed 

 it ; but presently he began to struggle, and succeeded, by 

 great efforts, in re-gorging it, but, doubtless, not without 

 having been severely stung. 



From the peculiar nature of the aliment of frogs, some 

 naturalists have reasoned, not without justice, that they 

 ought not to be persecuted in gardens. In fact, they are use- 

 ful in such places, by destroying an immense quantity of those 

 small slugs which are so detrimental to young plants of every 

 species. 



Daudin tells us that they also devour the spawn of fresh 

 water fishes when they get near them. 



Our countryman Townson, has made some curious experi- 

 ments on the faculty possessed by frogs of absorbing water 

 by the surface of their bodies. He is convinced that these 



