156 
DEVELOPMENT OF THE TADPOLE . 
We now come to the best known of all the batra, chians, the Common Feog. 
The general form and appearance of this creatnre are too well known to need mnch 
description. It is fonnd plentifully in all parts of Europe and America, wandering to consid- 
erable distances from water, and sometimes getting into pits, cellars, and similar localities, 
where it lives for years without ever seeing 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 favorite 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 labor of a human being. 
The chief interest of the Frog lies in the cnrious changes which it undergoes before it 
attains its perfect condition. Every one is familiar with the huge masses of transparent 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 globular gelatinous envelope about a quarter of an 
inch in diameter. According to gipsy lore, rheumatism may be cured, by plunging into a 
bath filled with Frog spawn. 
On comparing these huge masses with the dimensions of the parent Frog, the observer 
is disposed to think that so bulky a substance must be the aggregated work of a host of 
Frogs. Such, however, is not the case, although the mass of spawn is forty or fifty times 
DEVELOPMENT OF THE EGG AND OF THE TADPOLE OF THE GREEN FROG.— 1. Eggs just laid. 
3. The same, a short while later. 3. Tadpole in the Egg. 4 and 5. Tadpoles just out of Egg. 
6 to 13. Further development of the Tadpole, up to its last transformation. 
larger than the creature which laid it. The process is as follows : The eggs are always laid 
under water, and when first deposited, are covered with a very slight but firm membranous 
envelope, so as to take up very little space. No sooner, however, are they left to develop, than 
the envelope begins to absorb water w T ith astonishing rapidity, and in a short time the eggs are 
inclosed in the centre of their jelly-like globes, and thus kept well apart from each other. 
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 apparent. In this state it is a black grub-like 
creature, with a large head and a 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 horsenail. 
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 
consists of a double tuft of finger-like appendages on each side of the head. The tadpole, with 
the fully developed branchiae, is shown at Fig. 6, on the accompanying illustration. No sooner, 
however, have these organs attained their size than they begin again to diminish, the shape of 
