254 



HOW DO WE CLASSIFY ANIMALS? 



now insectivorous in its diet, becomes provided with tiny teeth and 

 a mobile tongue, instead of the horny jaws used in scraping off 

 algae. After the tail has been completely absorbed and the legs 

 have become full grown, there is no further structural change, 



and the metamorphosis is 



complete. 



Practical Exercise 14. Make a 

 series of diagrams to show changes 

 in methods of breathing in the frog, 

 from hatching to adult. 



Compare the metamorphosis of 

 a frog with an insect. Can you 

 find four stages in each : egg, larva, 

 pupa, adult? 



Toad. One of the nearest 

 relatives of the frog is the com- 

 mon toad. Its ugly appear- 

 ance has given it a bad name. 

 Toads do not cause warts, and do much good in our gardens by 

 eating harmful insects. Their eggs are laid in strings, and like those 

 of the frog, are deposited in fresh- water ponds. As many as eleven 

 thousand eggs have been laid by a single toad. The egg-laying 

 season of the toad is later than that of the frog. Toad tadpoles 

 differ from those of the frogs, by being darker in color, and 

 having a more slender tail and a relatively larger body. 



Other amphibians. The tree frogs or tree toads are familiarly 

 known to us in the early spring as the " peepers " of the swamps. 

 They are among the earliest of the frogs to lay their eggs. During 



L. W. Brownell 

 How does a toad differ from a frog? 



L. W. Brownell 



Why is the red salamander an amphibian? 



