BATRACHIA. 187 



RANA, Linnaeus. 



Frogs have four legs in their perfect state, but no tail. Their head is flat, 

 muzzle rounded, and the opening of their jaws large ; 

 the tongue, in most of them, is soft, and not attached 

 to the bottom of the gullet, but to the edges of the 

 jaw, and folds inwards. There are but four toes to 

 the anterior feet; the hind ones frequently exhibit 

 the rudiment of a sixth. 



There are no ribs to their skeleton, and a promi- 

 nent cartilaginous plate supplies the place of a tym- 

 panum, and renders the ear visible externally. The eye is furnished with two 

 fleshy lids, and a third, which is transparent and horizontal, concealed under 

 the lower one. Inspiration is effected by the muscles of the throat, which, by 

 dilating, receives air from the nostrils, and by contracting while the nostrils 

 are closed by the tongue, compel the air to enter the lungs ; expiration on the 

 contrary is produced by the muscles of the lower part of the abdomen. The 

 young frog, which is called a tadpole, is at first furnished with a long fleshy 

 tail, and a small horny beak, having no other apparent limbs than little fringes 

 on the side of the neck. These disappear in a few days, and the hind feet of 

 the tadpole are very gradually and visibly developed ; the fore feet are also 

 developed, but under the skin, through which they subsequently penetrate. 

 The tail is gradually absorbed. The beak falls and discloses the true jaws, 

 which at first were soft and concealed beneath the skin ; and the branchiae are 

 annihilated, leaving to the lungs alone the function of respiration in which 

 they participated. The eyes, which at first could only be discerned through a 

 transparent spot in the skin of the tadpole, are now visible with their three 

 lids. Tadpoles reproduce their limbs almost like salamanders. 



The period at which each of these changes takes place varies with the spe- 

 cies. In cold and temperate climates, the perfect animal passes the winter 

 under ground, or in the mud under water, without eating or breathing, though 

 if we prevent it from respiring during the summer for a few minutes by keep- 

 ing its mouth open, it dies. 



HYLA, Laurent. 



Tree-Frogs only differ from frogs in the extremities of their toes, each of 

 which is expanded into a round, viscous pallet, that enables them to adhere 

 to the surface of bodies and to climb trees, where in fact they remain all sum- 

 mer, living upon insects. They spawn, however, in water, and enter the mud 

 in water like other frogs. There is a pouch under the throat of the male, 

 which dilates whenever he cries. 



Rana arborea, L. (The common Tree- Frog). Green above, pale beneath ; 

 a black and yellow line along each side of the body. They are adult in four 

 years. The tadpole completes its metamorphosis in the month of August. 



