DELAWARE COUNTY FROGS. 1 3 



— the cricket frog- and the swamp tree frog. At the most, 

 then, we have ten kinds of frogs and tree frogs. It is not a 

 large list, and one might, with good fortune, succeed in meet- 

 ing members of all the species in a single j^ear. However, 

 two or three of them are rare, or at least seldom seen. 



Perhaps every one knows, by this time, that all frogs, as 

 well as the toads and other batrachians, begin life as tadpoles, 

 or pollywogs. The eggs are laid in slow-flowing streams, in 

 ponds, in pools, ditches or swamps. They are in the form of 

 blackish, shot-like specks, enclosed in masses of clear jelly. 

 This jelly is of nearly the same specific gravity as water. 

 Sometimes the masses float about in the water, sometimes 

 they rest upon the l)oltom. The heat of the sun seems to 

 have some sort of action on certain kinds of frog spawn, 

 causing it to become lighter, much after the manner of various 

 algae, which, as the sunlight strikes them, generate gases that 

 bring them to the surface. In the case of the alg^e the gas is 

 largely oxygen, which is generated by the sunlight in the 

 living cells furnished with the green substance called chloro- 

 ph^'ll. In the spawn the bubbles are in all probability carbon 

 dioxide ("carbonic acid"), the gas that is such a constant 

 product of vital activity in animal life. 



The eggs are at first approximately globular. They soon 

 become indented on one side and each gradually' uncurls a flat 

 tail. The "head" — which is in reality the body — begins 

 to shape itself, the tail continues to grow, the tadpole, in 

 short, to assume its proper form. After due preparation the 

 tadpole eats its way out of the surrounding jelly and swims 

 freely about. The jelly itself finally disappears. What 

 becomes of it? Sometimes it liquefies to a large extent, but 

 other times it may possibly be eaten by the tadpoles, in whole 

 or in pari. However this may be in the case of frogs, I have 

 found that the jelly about the eggs of the water newt, when 

 Jiept in a cup of water until the tadpoles appeared, and there- 

 after, was f[uickly and completely devoured liy those tad- 



