THE COMMON FROG. 443 
water. The food of the adult Frog is wholly of an animal character, and 
consists of slugs, possibly worms, and insects of nearly every kind, the wire- 
worm being a favourite article of diet. A little colony of Frogs is most 
useful in a garden, as they will do more to keep down the various insect 
vermin that injure the garden than can be achieved by the constant labour 
of a human being. 
The chief interest of the 
Frog lies in the curious 
changes which it under- 
goes before it attains its 
perfect condition. Every- 
one is familiar with the 
huge masses of transpa- 
rent jelly-like substance, 
profusely and regularly 
dotted with black spots, 
which lie in the shallows 
of a river or the ordinary 
ditches that intersect the 
fields. Each of these 
little black spots is the 
egg of a Frog, and is 
surrounded with a glo- 
-bular gelatinous envelope 
about a quarter of an 
inch in diameter. 
In process of time, 
certain various changes 
take place in the egg, and 
at the proper period the 
form-of the young Frog 
begins to become appa- COMMON FROG.—(Rana temporaria.) 
rent. In this state it is 
a black grub-like creature, with a large head anda flattened tail. By degrees 
it gains strength, and at last fairly breaks its way through the egg and is 
launched upon a world of dangers, under the 
various names of tadpole, pollywog, toe-biter, or 
a : c 
horsenail...  . i. j ; 
_ As it is intended for the present to lead an 
aquatic life, its breathing apparatus is formed on 
the same principle as the gills of a fish, but is 
visible ‘externally, and when fully developed con- 
sists of a double tuft of finger-like appendages 
on each sidé of the head. The tadpole, with the 
fully-developed branchia, is shown at Fig. a on 
the accompanying illustration. No sooner, how- 
ever, have these organs attained their size than 
they begin again to diminish, the shape of the d 
body and head being at the same time much altered, 
as is seen in Fig. 6. Ina short time they entirely 
disappear, being drawn into the cavity of the 
chest and guarded externally by a kind of gill-cover. TADEOLES: 
Other changes are taking place meanwhile. Just behind the head two little 
projections appear through the skin, which soon develop into legs, which, 
however, are not at all employed for progression, as the tadpole wriggles its way 
