FROGS AND TOADS 
121 
from eggs which are usually deposited in the 
water by the females, or occasionally upon 
dry land. But in some instances the eggs do 
not see the light of day, the young being born 
in an active state. 
Before reaching maturity the tadpoles 
undergo a series of changes, and in the meta¬ 
morphosis of the common frog the newly- 
hatched young one commences its free existence 
as an elongated creature with a large head 
and compressed tail, the mouth being furnished 
with small projections, known as “ holders,” 
which enable the creature to attach itself to 
water-plants. As growth proceeds the tail 
becomes much broader, a vertical and 
membrane-like crest arising both above and 
below that member. The limbs then make 
their appearance, the hinder ones being the 
first to show, followed a few days later by the 
front ones. Finally the tail is gradually 
absorbed into the system, the cleft of the 
mouth becomes much extended, and the 
creature assumes the form of a miniature 
frog. 
The skin of adult frogs and toads is covered 
with numerous glands which, in the majority 
of the latter, are developed into wart-like 
excrescences upon the body and large swellings 
on the sides of the head, behind the eyes. 
