364 MOSTLY MAMMALS: 
a tree-frog (Hyla abéreviata) have been observed adhering 
to rocks by means of the flat surface of the abdomen, 
which acts as a sucker. Nothing is, however, known with 
regard to the eggs. 
In all the foregoing instances the peculiarities of develop- 
ment are confined to the situations in which the spawn 
is deposited and the tadpoles are developed. There is, 
however, another and far more remarkable class of cases 
in which the bodies of either the male or female parent 
are specially modified to act as receptacles for the eggs 
and tadpoles. The best instance of this class is that of 
the well-known Surinam toad (Pipa americana),* in which 
the eggs are evenly distributed, as they are laid, over the 
back of the female by the male. Around these the skin 
of the back speedily thickens until each egg is enclosed in 
a separate cell, furnished with a lid. The eggs hatch in 
about eighty-two days, and the young are stated to find 
safety and nourishment on the parental back until their 
transformation is completed. The limbs make their appear- 
ance at an unusually early age, even before the external 
gills are shed. 
Equally remarkable are the “nursery” arrangements of 
the pouched frogs (JVototrema) of South America. In these 
frogs the back of the female is furnished with a long tube- 
like pouch, having its opening at the posterior end. In 
this pouch the eggs, which are about fifteen in number, 
are deposited and hatched; and the tadpoles also undergo 
the whole of their metamorphosis in the same chamber. 
In some cases, at least, the pouch splits longitudinally 
* The breeding habits of this and some of the following forms have 
been already referred to in a previous article ; but, in order to render 
the present one complete in itself, it has not been considered advisable 
to eliminate such repetition as may exist. 
