222 AMPHIBIA 



the case, the animal remains in its normal position but turns its 

 limbs over its back so as to show as much as possible of their 

 lower surface and of the red markings of the belly. Dendro- 

 bates in South America offers an example of a tree-frog which 

 instead of being protectively coloured like the Hylidae is 

 warningly coloured and poisonous : some are black and white, 

 others black and yellow or black and red, one species is red 

 with small dark marks on the back, and black legs. A very 

 curious use is made in Brazil of the poison secreted by the skin 

 of Dendrobates tinctorius : the feathers of the head and neck 

 or other parts of green Amazon parrots are plucked out and 

 the skin is then rubbed with the poison or simply with the skin 

 of the living frog and as a consequence the new feathers which 

 grow are yellow instead of green, so that artificially coloured 

 parrots are produced, which are valued as curiosities. In 

 Colombia the Indians are said to use the same poison for 

 poisoning the tips of their arrows, which are employed especi- 

 ally for shooting monkeys. The poison acts on the heart and 

 central nervous system. 



The contrast between the lizard-like shape of the newts 

 and their modes of locomotion and the structure of the frog 

 or toad, adapted for leaping and destitute of tail, is very con- 

 spicuous. As in the original Amphibian the limbs were 

 evolved from the fins of fishes by adaptation to terrestrial 

 conditions, so in the Anura the elongation of the hind limbs 

 for leaping and the loss of the tail could scarcely have been 

 due to the requirements of locomotion in the water. At the 

 same time both the Urodela and the Anura usually pass 

 part of their lives in the water, and their different types of struc- 

 ture are adapted to both aquatic and terrestrial movement. In 

 the Urodela when the animals are either temporarily or per- 

 manently aquatic the tail is furnished with a membranous fin ; 

 in the common British newts this fin diminishes greatly when 

 the animals leave the water after the breeding season ; in the 

 salamanders which are almost entirely terrestrial, the fin is 

 absent, as it is also in the genus Ambly stoma. In some species 

 there is a membrane along the dorsal edge of the body as well 

 as on the tail ; this is known as the crest and is confined to the 

 males as in Triton cristatus and vulgaris. This crest occurs 

 in those species which perform a lengthy courtship in the 



