18 REPTILES AND BIRDS. 
aérial respiration, and so ought to form a separate class of Verte- 
brates.* 
Batrachians establish a transitional link between Fishes and 
Reptiles—they are, as it were, a bond of union between those two 
groups of animals. In the adult state Batrachians are cold-blooded 
animals with incomplete circulation, inactive respiration, and the 
skin bare. In the introductory section to this chapter we have given 
the general characteristics which belong to them. The Frogs—Tree 
Frogs, Toads, Surinam Toads, Salamanders, and Newts—are the re- 
presentatives of the principal families of Batrachians of which we 
propose giving the history. 
The Frogs (Rana) have suffered injury by their resemblance to 
Toads. ‘This circumstance has given rise to an unfavourable pre- 
judice against these innocent little Batrachians. Had the Toad not 
existed, the Frog would appear to us as an animal of a curious form, 
and would interest us by the phenomena of transformation which it 
undergoes in the different epoclis of its development. We should 
see in it a useful inoffensive animal of slender form, with delicate and 
supple limbs, arrayed in that brilliant colouring which is so pleasant 
to the eye, and which mingles so harmoniously with the carpeting of 
our fields. 
The bedy of the Edible Frog, Rana esculenta (Fig. 4), sometimes 
attains a length, from the extremity of the muzzle to the end of the 
hind feet, of six to eight inches. ‘The muzzle terminates in a point ; 
the eyes are large, brilliant, and surrounded with a circle of gold 
colour. The mouth is large; the body, which is contracted behind, 
presents a tubercular and rugged back. It is of a more or less 
decided green colour on the upper, and whitish on the under parts. 
These two colours, which harmonise well, are relieved by three yellow 
lines, which extend the whole length of the back, and by scattered 
black marblings. It is, therefore, much to be regretted that prejudice 
should cause some at least of us to dislike this pretty little creature. 
For ourselves, we cannot see the banks of our streams embellished 
by its presence and animated with its gambols without pleasure. 
Why should we not follow with our eyes their movements in our 
ponds, where they enliven the solitude without disturbing its tran- 
quillity. Frogs often leave the water, not only to seek their nourish- 
ment, but to warm themselves in the sun. When they repose thus, 
* They are regarded by some naturalists as a sub-class of Fishes rather than 
as Reptiles; as gzscine forms, certain of which develop to a parallelism with the 
ordinary reptilian condition of advancement ; their reproduction especially favour 
ing this view.—ED. 
