AMPHIBIA 227 



nervous system.' The Indians of Columbia, it is said, use the 

 secretion of Dendroh' ates tincto'rius for poisoning arrows to shoot 

 monkeys. That this secretion protects these amphibians from 

 their enemies (the "glass snake" is an exception) is evident from 

 the fact that "a dog that has once been induced to bite a toad 

 suffers so severely that it will not repeat the experiment." The 

 handling of the tree-frogs irritates both nose and eyes. Many 

 of the most poisonous amphibians (as Salaman'dra maculo'sa, 

 Bom'hinator, and Dendroh' ates) are conspicuously marked with 

 yellow and black. The horned frog of South America, which 

 fights and poisons its antagonist, is brilliant in green and gold. 

 Many assume a threatening attitude. " Toads normally have 

 the sections of the breast-bones overlapping, so that they can 

 swell themselves enormously when angry. "^ 



Ec'dysis. — All amphibians shed the epidermis. The first 

 ecdysis occurs at the time the metamorphosis is completed, 

 preparatory to terrestrial life. The Anu'ra roll up the cast-off 

 skin and swallow it. The Urode'la also eat it. The skin of the 

 Anura generally splits down the back, but that of the Urodela 

 breaks loose around the mouth, and the animal slips out, turn- 

 ing its hide wrong side out. So long as growth continues, the 

 skin must be shed often, as this outside layer will not "give" 

 to make room for growth. The adult Urodela do not molt 

 often, but usually at the breeding season, when they go to the 

 water to deposit their eggs. The Anura molt frequently, at 

 least every few months, probably to keep the skin moist. 



Voice. — Most of the Anura and some of the Urodela have a 

 voice produced by the larynx, which is often provided with a 

 complicated cartilaginous and muscular apparatus and with 

 vocal cords. The female of the Anura is mute or utters only a 

 grunt. The sound made by the male is called a croak. The 

 voice of Urodela is a feeble squeak. The song of frogs and toads 

 is usually of the nature of a serenade to its would-be mate, for 

 they do not, as a rule, cry out in fright nor in rage. A notable 

 exception is that of the vicious horned frog of South America, 

 which is said to defy its foes with a sort of bark, but which has a 

 clear bell-like tone for its friends. Our common green frog is 



' Gadow, " Amphibia and Reptiles," p. 38. 

 ' Baskett, p. 29. 



