34 STORY OF THE AMPHIBIANS 



reject the use of tlie lung, yet in the more aquatic 

 kinds it has much degenerated or never developed, 

 and these creatures die when out of the water as 

 quickly as many fishes. Since these show a tendency 

 to have weak limbs they are likely degenerate forms 

 that have lost their high estate by laziness. 



In all tadpoles which develop into land-haunters 

 the limbs begin to appear about the time the lungs 

 develop. It is remarkable that these limbs should be 

 almost complete in all their parts before they come 

 forth from under the skin, where for a time they 

 form a small stump. It is one of those " shortened 

 up " processes of Nature of which we shall find so 

 many from this on. In the tadpoles of the frog- 

 forms, modern demands have reached back so far as 

 to grow out the hind limbs first, but in all others it 

 is the fore limb that first shows. In frog-forms the 

 tail soon departs — is not lost — but is absorbed into the 

 body — as the limbs grow. In all others it remains, 

 and has vertebrae (joints of the back-bone) form in 

 it. There is never any vertebrae in the tail of the 

 tadpole of the frogs, which have only horny jaws, and 

 are rather more vegetable-eating than the other forms. 

 It is said, however, that they have teeth before they 

 have the beaks. In all tadpoles the gape is small — 

 the mouth rather sucking. Those of toads, like the 

 eggs, are always much blacker than those of frogs. 

 It is impossible here to outline any further means of 

 recognizing the various kinds of tadpoles. But an 

 expert naturalist will know many if not all of them 

 by some peculiarity. Those of frog-forms show only 



