THE LIVING WORLD. 
*33 
FROGS AND TOADS. 
Though some naturalists do not include frogs in their classification of 
reptiles, reserving them for a general order, called batrachia , I have preferred 
to follow the arrangement of equally reliable authorities and introduce this 
order as the one in most natural sequence to fishes on account of a similarity 
which exists between the two orders in many essentials. The two prime differ¬ 
ences that serve to distinguish the frog and the toad is in the former being 
largely an inhabitant of the water, and having a smooth, flecked skin, while the 
latter, though not extremely averse to water, spends his life upon land, clothed 
in a much less inviting raiment than his aquatic first-cousin. The water frog 
is admirably adapted to his element by being provided with webbed feet and 
ANTED!I.UVIAN LAND REPTIT.ES. 
long hind legs, which enable him to move through the water at great speed. 
His toes, however, are of considerable length, by which he can chug to limb 
or log, and which make his footing sure on shore. Like all amphibians, the 
heart of a frog has a single ventricle, permitting the blood to circulate without 
the help of lungs, thus enabling it to remain for a long while under water. 
Professor Raesel, of Nuremberg, devoted several years of his life to a study 
of the frog in all its metamorphoses, and upon this subject supplies us with 
some very curious, as well as useful information, upon whose authority most 
naturalists rely for the following facts: - r 
The common frog, in which designation both the toad and water-frog may 
be included, since the propagation of each is identical, chooses his mate early m 
