84 OUTLINES OF NATURAL HISTORY. 



ters, and it possesses a very long and mucli-convoluted 

 intestine. 



After a whUe the limbs commence to appear, two j)airs 

 of these being proper to the adult animal. The first to 

 become visible externally are the hind-limbs (fig. 37, c) ; 

 whilst the fore-limbs are developed within the chamber 

 which contains the gills, and do not make their appear- 

 ance till later. The tail, however, still remains ; and it is 

 not till the development of the limbs has become consid- 

 erably advanced that the tail begins gradually to diminish 

 in size and to dwindle away. Finally, the animal takes 

 to the land, and, no longer needing its tail to swim with, 

 this organ is completely absorbed, and the adidt thus 

 becomes "tailless." 



Coincident, however, with the sprouting forth of the 

 limbs and the diminution of the tail is a more important 

 internal change, by wliich the animal is enabled to leave 

 the water, and betake itself to the dry land. At first, as 

 we have seen, the animal breathes by gills, and cannot 

 exist out of the water. After a period, however, lungs, 

 adapted for breathing air directly, are developed, and the 

 animal now loses its gills altogether. It now ceases to be 

 an inhabitant of the waters, and, changing its medium, 

 it becomes terrestrial in its habits, though still capable of 

 taking to the water when necessary. The fully -grown 

 Frog, therefore, differs from the young Frog, or Tadpole, 

 in breathing by lungs instead of by gills, in having two 

 pairs of well-developed limbs, and in not possessing a tail. 

 It may be added that the adult Frog Uves upon animal 

 matter, slugs, insects, and the like, instead of vegetable 

 food, and that its alimentary canal is much shorter and 

 more simple than that of the young. 



The fully-grown Frog (fig. 38) has a short body, a broad 

 head, wide mouth, and long muscular legs. The fore-legs 

 are much shorter than the hind-legs, and terminate in four 

 toes each. The hind-legs, on the other hand, are greatly 

 developed, and terminate in five long toes, which are 

 "webbed," or united by a membrane, so that they consti- 

 tute very efficient and powerful swimming-organs. 



