PERENNIBRANCHIATE BATRACHIA. 99 
less complete than in the Frog, being checked at a less 
advanced stage. Thus in the common Water-Newt, the tail 
is retained during the whole of life, and the animal continues 
to be an inhabitant of the water, though breathing air alone. 
There are some very curious animals, however, in which the 
change is stopped, as it were, at a much earlier period, so that 
the gills also are retained ; and in these, the lungs are suffi- 
ciently developed to enable the animals to breathe air, so that 
they can live either on land or in water. Such Batrachia are 
scientifically known as perennibranchiate, this term express- 
ing the persistency of their gills. In fig. 40 is represented 
Fig. 40.—AxXoLorTL. 
an animal of this kind, the Azolotl, which inhabits some of the 
lakes of Mexico. And in fig. 41 is shown the form of a still 
more remarkable animal, the Lepidosiren, or mud-fish, recently 
Pig. 41.—LEPprposiREN. 
brought from th> rivers of Africa, the metamorphosis of 
which appears to be checked at a still earlier period, so that 
itis very difficult to decide whether it should be regarded as 
H 2 
