276 ZOOLOGY * ECT - 



membranes, the trunk short, the tail absent, and the hind- much 

 larger than the fore-limbs. In the Toads, such as the common 

 British Bufo vulgaris, and the tree-frogs (Hyla\ the webs between 

 the hind-toes are reduced or absent, and in many species of 

 Hyla the toes end in rounded sucking-discs. 



In the Gymnophiona (Fig. 890) the body is greatly elongated and 

 snake-like, the head is small and not depressed, and the limbs are 

 absent. There is no tail, the anus (an.) being at the posterior end of 

 the body on the ventral surface. The Stegocephali, or Labyrmtho- 

 donts as they are frequently called, were mostly salamander-like, 



FIG. 889. Saiamandra maculosa. (After Cuvier.) 



having long tails and well-developed limbs : some, 

 however, were snake-like and limbless and probably 

 retained their external gills throughout life. They 

 varied in length from 10 centimetres to several 

 metres. 



The skin of Amphibia is soft and usually slimy owing 

 to the secretion of the cutaneous glands, which is some- 

 times poisonous. In some forms, such as Bufo and 

 Saiamandra, there are large swellings on the sides of 

 the head, formed of aggregated glands and called parotoids. In 

 the larvae and in the adult aquatic Urodeles lateral sense-organs 

 are present, and impressions on the cranial bones show these 

 organs to have been well developed in the Stegocephali. The 

 colour of the skin is often very brilliant : the Spotted Sala- 

 mander is yellow and black, and many Frogs are green and 

 gold, scarlet and black, and so on. The green colour of Tree- 

 frogs is protective, serving to conceal them among the foliage 

 of the plants on which they live. The brilliant and strongly 

 contrasted hues of the spotted Salamander and of some frogs 

 are instances of " warning colours " ; the animals are inedible 



