THE ALLIES OF THE FROG 



349 



the eyelids. The dark-colored eggs are laid in long strings, 

 like a string of beads, in shallow water, usually in April, in 

 the latitude of New York. They hatch in two or three 

 weeks into small black tadpoles, which transform and become 

 minute toads within 

 about two months. 



Use as Food. Sev- 

 eral different species 

 of the larger frogs, the 

 bullfrog and the green 

 frog especially, are 

 frequently caught for 

 market. The hind legs 

 of frogs are by many 

 considered a great 

 delicacy. 



Amphibians of the 

 Past. Since the am- 

 phibians are the lowest 

 animals having limbs 

 similar to those of 

 mammals, man has 

 been much interested 

 in their beginnings. 

 The first fossil remains 

 of amphibians date to 

 that period of the 



earth's history when there was a very luxuriant growth of 

 tropical fern-like trees. During this time there were many 

 regions where movements of the earth's crust caused these 

 forests to be covered by water and turned into coal. The 

 swamps of that time are the coal beds of today, and the 

 period is known as the Carboniferous Age, or Age of Coal 

 Plants. Though fishes and many invertebrate forms were 



Fig. 178. Photograph of a tree frog on the 

 bark of a tree. (Natural size) 



