176 THE HAUNTS OF LIFE 
frogs in March or April, then look for the 
clumps of jelly-like eggs, take them home and 
keep them in a properly shaded vessel, and we 
can follow the whole fascinating story. But we 
must be careful to keep water-plants growing 
in our aquarium, that the water may be aerated, 
to supply food, but to remove all decaying 
matter, and to provide a foothold for the little 
creatures when they are about to make their 
great change from the tadpole to the frog stage. 
All the members of the group have in their 
full-grown state the great characteristic of 
adult terrestrial animals—they breathe, by 
means of lungs, the oxygen in the air. But the 
young of almost all of them have gills 
and breathe the oxygen dissolved in water. 
The time the tadpole breathes by gills may 
be longer in one family than another, it may 
even vary in the same family, according to 
surroundings and weather, but, long or short, 
it is very rarely omitted. 
Another fact that shows the direction in 
which they are tending is that even the adults 
are not all equally terrestrial in habit. Both 
frogs and toads spend some time in the water 
in spring, and leave it when their eggs are 
safely deposited. But as winter approaches, 
