LIFE OF AMPHIBIANS. 607 



from the parietals ; the palatines are fused with the maxillae. The 

 eggs are large and meroblastie. They are altogether peculiar archaic 

 Amphibians. Examples : Ccecilia (S. America) ; Ichthyophis (Ceylon, 

 India, Malay); Hypogeophis (E. Africa); Siphonops, without scales 

 (America). 



Order STEGOCEPHALI 



Extinct forms, occurring from Carboniferous to Triassic strata. 

 The earliest known digitate animals. 



Dermal armour is present, the teeth are frequently folded in a 

 complex manner (Labyrinthodonts). Mastodonsaurus, Dendrerpeton, 

 Archegosaurus, Branchiosaurus. 



LIFE OF AMPHIBIANS 



Most Amphibians live in or near fresh-water ponds, swamps, and 

 marshes. They are fatally sensitive to salt. 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 (Sala- 

 mandra atra} of the Alps lives 

 where pools of water are scarce, 

 and instead of bringing forth 

 gilled young, as its relative the 

 spotted salamander (S. maculosa) 

 does, bears them as lung- 

 breathers, and only a pair at a 

 time. The unborn young have 

 gills which are pressed against FIG. 328. Csecilian (Ichthyophis'] 

 the vascular wall of the uterus. with eggs. After Sarasin. 



It is said that the respiration (and 



nutrition) of the young is helped by crowds of red blood corpuscles 

 which are discharged from the walls of the uterus ; the debris of 

 unsuccessful eggs and embryos seems also to be used for food. 



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

 Islands, live in regions where there are few pools. In such cases the 

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

 tailed larva is hatched in about fourteen days. 



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 



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