AMPHIBIANS. 



97 



tion is also necessary to assist the pulmonary respiration, or 

 respiration by means of the lungs, but it cannot take place 

 unless the exterior of the skin is moist. It can readily, then, 

 be seen how essential it is that the skin should be continually 

 moist. But as the frog cannot always have access to water, it 

 has been provided with a kind of portable reservoir which 

 contains pure and tasteless water, and by means of which the 

 animal is able to keep its skin, even in dry places, in the 



Fig. 79. Common Frog (Eana tempobaria). 



necessary state of dampness. The frog when captured will 

 often discharge the contents of this reservoir. 



When the aquarium-keeper has carefully watched the de- 

 velopment of the egg into the tadpole, and the tadpole into 

 the perfect batrachian; when he has noticed its curious 

 tongue and its manner of feeding ; and when he has knowledge 

 of its cutaneous respiration and portable reservoir, he will 

 come to the conclusion that the common and often despised 

 frog is indeed a very interesting and extraordinary animal. 

 The tanks in which frogs are kept should be covered. 



