390 MANUAL OF ZOOLOGY. 



as is the case with the Urodela. Even after the first appear- 

 ance of the limbs the tail is still retained as an instrument of 

 progression but as the limbs become fully developed, the 

 tail gradually is absorbed (fig. 151, d), until in the adult it has 

 wholly disappeared. 



The development of the Frog is thus a good illustration of 

 the general zoological law that the transient embryonic stages 

 of the higher members of any division of the animal kingdom 

 are often represented by the permanent condition of the lower 

 members of the same division. Thus the transitory condition 

 of the young Frog in its earliest stage, when the branchiae are 

 external, is permanently represented by the adult perenni- 

 branchiate Urodela, such as the Proteus or the Siren. The 

 final stage, again, when the gills have disappeared and the limbs 

 have been developed, but the tail has not been wholly absorbed, 

 is represented by the caducibranchiate Urodela, such as the 

 common Newt. 



The order Anoura comprises a considerable number of 

 forms, but may be divided into the three sections of the 

 Pipidce, Bufonidce, and Ranidce. In the Pipidce, or Surinam 

 Toads, there are rarely teeth, and the mouth is destitute of a 

 tongue. A singular and hideous species (Pipa Americana) is 

 the best known, and it inhabits Brazil and Surinam. In the 

 aberrant form Dactylethra the upper jaw is furnished with 

 small teeth, and the three inner toes of the hind-feet are fur- 

 nished with nails, as is the case with no other Amphibian, 

 except Salamandra unguiculata amongst the Urodela. This 

 curious form is found at the Cape of Good Hope and in Moz- 

 ambique. 



In the Toads, or Bufonidce, a tongue is present, but the 

 jaws are not armed with teeth. The tongue agrees with that 

 of the Frogs in being fixed to the front of the mouth, whilst it 

 is free behind, so that it can be protruded for some distance 

 from the mouth. The hind-limbs are not disproportionately 

 developed, whilst the toes are only imperfectly webbed, and 

 the toes of the fore-limb are free. The common Toad (Bufo 

 vulgaris) is an excellent example of this family. 



In the Ranidce. the tongue has the same form as in the 

 Toads, but the upper jaw always carries teeth. The hind- 

 limbs are much larger than the fore-limbs, and are fitted for 

 leaping, whilst the toes are webbed. The toes of the fore- 

 limbs are free. The common Frog (Rana temporaria) is a 

 good example of the typical Ranidce; but the Tree-frogs (Hyla) 

 are adapted for a wholly different mode of life, having the toes 

 pf all the feet furnished with terminal suckers, by the help of 



