LIFE OF AMPHIBIANS. 607 
from the parietals; the palatines are fused with the maxille. The 
eggs are large and meroblastic. They are altogether peculiar archaic 
Amphibians. Examples :—Cacd/¢éa (S. America) ; Zchthyophis (Ceylon, 
India, Malay); Aypogeophis (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). MJastodonsaurus, 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 Ay/a, are usually 
arboreal in habit, while the 
Gymnophiona and some toads 
are subterranean. 
The black salamander (Sa/a- 
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. mzaczlosa) 
does, bears them as_ lung- 
breathers, and only a pair at a 
time. The unborn young have os . 
gills which are pressed against Fic. 328.—Cecilian (Zchthyophis) 
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 débris of 
unsuccessful eggs and embryos seems also to be used for food. 
Species of Hylodes, such as A. 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. a 
In some Mexican and N. American lakes there is an interesting 
amphibian known as Amélystoma or Siredon. It has two forms—one 
losing its gills (Ambystoma), 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 
