TOADS AND FROOS. 
187 
also of Central America, Peters found traces of external 
gills. The Pipa, or Surinam toad {Pipa Americana), 
which has no tongue, neither teeth in the upper jaw, has 
similar breeding habits. In this interesting toad the young 
are provided with small gills, which, however, are of no 
use to them, as the tadpoles do not enter the water, but 
are carried about in cavities on the back. The eggs are 
placed by the male on the back of the female. The female 
then enters the water; the skin thickens, rises up around 
each egg and forms a mai'supial sac or cell. The young 
pass througli their metamorphosis in 
the sacs, having tails and rudimentary 
gills; these are absorbed before they 
leave their cells, the limbs develop, 
and the young pass out in the form 
of the adult. 
The toad {Bitfo le7itigi?iosus) is ex- 
ceedingly useful as a destroyer of 
noxious insects. It is nocturnal in 
its habits; is harmless, and can be 
taken up with impunity, though it 
. \ -n n -T^ Fig. 232.— The Martinique 
gives out an irritant acrid liuid irom Tree-toad carrying the 
the skin, which if transferred to the young on its back, 
eye or lids occasions some pain. In the Northern States 
toads begin to make their peculiar low trilling notes from 
the middle to the 20th of April; from the latter date until 
the first of June they lay their eggs in long double strings, 
and the tadpoles are usually hatched in about ten days 
after the eggs are laid. 
Of the true frogs {Rana) there are numerous species; of 
these the largest is the bull-frog, which makes a deep, 
hoarse, grunting noise. Smaller and more common species 
are the pickerel-frog and the marsh-frog. The frogs lay 
their eggs in roundish masses in ponds and pools from 
April to June, according to the latitude. 
While most frogs are greedily devoured by herons and 
other large wading birds, as well as ducks and geese, and 
