98 METAMORPHOSIS OF BATRACHIA. 
loosely in the water on either side of the head. At a later 
period, however, these gills, which are merely temporary, 
disappear ; and the breathing is carried on by another set, 
which are situated behind the head, and are covered in by at 
fold of skin; the water gains access to these by passing — 
through the mouth, exactly as in Fishes. The form is then 
that which is represented in fig. 36. In a short time after- 
wards, the animal still breathing by its gills, the hind-legs — 
begin to sprout forth, as it were, at the base of the tail; this 
Fig. 39. 
stage is shown in fig. 37. At a still later period, the fore- 
legs begin to be developed, as seen in fig. 38; and from that 
time they are nourished at the expense of the tail, which 
gradually disappears, as seen in fig. 39, a,b. During this’ 
period, other important changes are taking place in the inte- 
rior of the body; the chief of which are the development of 
the lungs and‘the gradual disuse of the gills, so that the 
animal becomes fitted to live on land and breathe air, and is | 
no longer capable of remaining long under water without 
coming to the surface to respire. “ 
87. The metamorphosis in other members of the group is 
