LIFE OF AMPHIBIANS. 445 



Life of Amphibians. — Most Amphibians live in or near fresh water 

 ponds, swamps, and marshes. Even those adults which have lost all 

 trace of gills, are usually fond of water. The tree-toads, such as Hyla, 

 are usually arboreal in habit, while the Gymnophiona and some toads 

 are subterranean. 



The black Salamander (Salamandra atra) of the Alps lives where 

 pools of water are scarce, and instead of bringing forth giUed young, as 

 its relative the spotted salamander (S. maculosa) does, bears them as 

 lung-breathers, and only a pair at a time. But if the unborn young are 

 removed from the body of the mother and placed in water, they form gills 

 like other tadpoles. Within the mother, the respiration and nutrition 

 of the young seem to be effected by crowds of red blood-corpuscles 

 which are discharged from the walls of the uterus. 



Species of Hylodes, such as H. martinicensis of the West Indian 

 Islands, live in regions where there are few pools. The development is 

 completed within the egg-case, and a lung-breathing tailed larva is 

 hatched in about fourteen days. It is likely that the tail helps in respira- 

 tion before hatching, but one observer reported the presence of small 

 gills. 



In some Mexican and N. American lakes, there is an interesting 

 amphibian known as Amblystoma or Siredon. It has two forms, one 

 losing its gills (Amblystoma'), the other retaining them (Axolotl). Both 

 these forms reproduce, and both may occur in the same lake. Formerly 

 they were referred to different genera. But the fact that some Axolotls, 

 kept in the Jardin des Plantes in Paris, lost their gills when their 

 surroundings were allowed to become less moist than usual, led 

 naturalists to recognise that the two forms were but different phases of 

 one species. It has been shown repeatedly, that a gilled Axolotl may 

 be transformed into a form without gills, and this metamorphosis seems 

 to occur constantly in one of the Rocky Mountain lakes. We must not 

 leap to the conclusion, that a difference in the moistness of the environ- 

 ment alone determines whether this amphibian remain a gilled Axolotl 

 or become a gill-less Amblystoma. For both forms may occur in the 

 same lake, the change from Axolotl to Amblystoma may take place in 

 the water, and besides the persistence or non-persistence of gills, there 

 are other differenees between the two forms. 



Amphibians are very defenceless, but their colours often conceal them. 

 Not a few have considerable power of colour-change. 



Many Amphibians live alone, but they usually congregate at the 

 breeding seasons when the amorous males often croak noisily. Alike 

 in their love and their hunger they are most active in the twilight. 



Their food usually consists of worms, insects, slugs, and other small 

 animals, but some of the larval forms are for a time vegetarian in diet. 

 They are able to survive prolonged fasting, and many hibernate in the 

 mud. Though the familiar tales of " toads within stones " are for the 

 most part inaccurate, there is no doubt that both frogs and toads can 

 survive prolonged imprisonment. Besides having great vital tenacity, 

 Amphibians have considerable power of repairing injuries to the tail 

 or limbs. 



Although' the life of Amphibians seems to have on an average a low 

 potential, even the most sluggish wake up in connection with reproduc- 



