ORDERS OF AMPHIBIA. 441 



contained in a gill-cavity, protected by a flap of integument, 

 which differs from the gill-cover of fishes in never developing 

 any opercular bones or branchiostegal rays. Within the bran- 

 chial chamber thus formed the fore-limbs are budded forth, but 

 the hind-limbs are the first to appear, instead of the fore-limbs, 

 as in 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 is gradually absorbed (fig. 190, 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, Bufonidcz, and JRanida. 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 this 

 curious Amphibian the eggs are placed by the male on the 

 back of the female, in the integument of which, in cell-like 

 cavities, the eggs are hatched and the young developed. In 

 the aberrant form Dadylethra 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 

 Mozambique. 



In the Toads, or Btifonidce, 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 skin is warty and glan- 

 dular. The common Toad (Bufo vulgaris] is an excellent 



