THE FROG. 97 



THE FROG S RELATIVES. 



Frogs, with toads and salamanders, belong to that class 

 of vertebrates called Batrachia. What are the points of 

 difference between frogs and toads? " The toad is exceed- 

 ingly useful as a destroyer of noxious insects. It is noc- 

 turnal in its habits, is harmless, and can be taken up with 

 impunity, though it gives out an acrid fluid from its skin, 

 which may poison the eyelids." 



How does a tree -toad differ from a common toad? 

 Should we say tree-toad, or tree-frog ? Take a tree-toad 

 from green leaves, and put it into a white-lined box ; cover 

 the box with a pane of glass. Is the tree-toad's color 

 affected by this change of surroundings? 



Salamanders are often found in cellars, and under rotten 

 logs, and in springs. They are often wrongly called 

 lizards. Lizards are scaly, and are true reptiles, and are 

 related more nearly to the snakes aud turtles. Salaman- 

 ders have smooth bodies ; they are harmless (as also are 

 lizards). If you find one, examine it carefully. Salaman- 

 ders also develop from a tadpole stage. Some salamanders 

 are viviparous. If kept in the dark, they sometimes fail 

 to complete their development. The mud-puppy, a large 

 salamander found in our rivers, retains its gills through 

 life. 



The frogs and toads (tailless Batrachia) rank higher 

 than the salamanders (tailed Batrachia), having passed 

 through the salamander stage and gone on to a higher, in 

 which they have more perfect organs. 



In studying insects, we observed that insects pass through 

 a worm-like stage, and that they rank higher than worms. 



