varied as the songs of the birds, and more ventriloqtiistic. These 

 are wholly the cries of the male Frogs, and cease when the mates 

 have been found and have spawned ; and to assist in producing them 

 many species have gular air-sacs, which are connected with the vocal 

 organs and furnish the power required for the loud and insistent 

 utterances. The great ear-drums correlated with this vocal power 

 are conspicuous in many species. 



The reproductive habits of Frogs are various. All of our com- 

 mon species lay their eggs in water, the eggs being fertilized as 

 they are laid. As the eggs are laid they are inclosed in a gelatinous 

 envelope secreted by the female. This swells and protects the eggs 

 from injury, from being fed upon, from the direct rays of the sun, 

 and in some species it serves to float the eggs at the surface of the 

 water, where oxygen is most abundant; finally, the envelope serves 

 as food for the young frogs. The mouth of the tadpole is small and 

 provided with a horny beak, which takes the place of the teeth which 

 are not yet developed. The tadpole feeds on algae that cover stones, 

 and on the flesh of dead animals. The long, spirally coiled intestine, 

 which can be seen on the under side of the animal, is an adaptation 

 to its prevailingly herbivorous diet, which requires a prolonged 

 digestion. 



The tadpole usually lives in the water for two or three months 

 before it takes to land. In the Bullfrog, however, the transformation 

 (see TOAD) does not take place until the second summer. 



In many tropical Frogs the reproductive habits are much modi- 

 fied. One species (PhyUobates trinitatis) of Venezuela and Trinidad 

 carries its tadpoles on its back, to which the young attach themselves 

 by means of their suckers. A frog of the Seychelles Islands lives in 



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