

RANA. REPTILES. 365 



ORDER IV. BATRACHIA. 



Heart with one auricle ; body covered with a naked skin ; 

 lungs two when mature, but with branchiae like fishes in their 

 early stage. 



BATRACHIA, (from /2ctTg*^oc, a frog.) The animals of this order have a heart 

 with a single auricle and ventricle. They have all two lungs, to which are added, 

 in the first stage of their existence, branchice or gills, more or less analogous to those 

 of fishes. The greater part lose these branchiae on arriving at their perfect state. 

 In two genera only, Sirena and Proteus, they are preserved during life. While the 

 branchiae subsist, the aorta in going from the heart is divided into as many branches 

 on each side as there are gills. The blood of the branchiae returns by veins, which 

 unite towards the back into a single arterial trunk ; and it is from this trunk, or 

 from the veins which form it, that the arteries arise which nourish the body, and 

 even those which conduct the blood to the lung. In the species which lose their 

 branchiae, the branches which lead to them become obliterated except two, which, 

 uniting in a dorsal artery, give off each a little branch to the lung. It is, as Cuvier 

 observes, the circulation of a fish changed into that of a reptile. 



Batrachian reptiles have neither scales, nor shield, nor nails on their toes, a naked 

 skin covering the whole body. The envelope of their ova is membranous. In 

 some species the male assists in their extrusion, and impregnates them as they are 

 extruded ; in others the ova are deposited. The young differ not only from the 

 adult by the presence of gills ; their feet are developed only by degrees ; and many 

 species possess in their first stage a snout and a tail, which they afterwards lose. 



Gen. 1. RAN A, Lin. 



Body slender ; hind-feet very long, muscular, and completely 

 palmated ; skin smooth ; upper jaw furnished with a row of 

 small teeth, and an interrupted transverse one in the middle 

 of the palate ; males with a thin membrane under the ear, 

 which is inflated with air when they cry. 



In their perfect state frogs have four legs and no tail. Their head is flat, their 

 snout rounded, and the opening of their jaws large. Their tongue is soft, not attached 

 to the gullet, but to the edge of the jaw, and folds inwards. They have four toes 

 on the fore feet ; the hind feet have five, and sometimes the rudiment of a sixth. 

 The skeleton of this family is entirely destitute of ribs ; and a cartilaginous plate on 

 the head supplies the place of a tympanum. The eye has two fleshy eyelids, and a 

 third, transparent and horizontal, concealed under the inferior one. Inspiration in 

 these animals is effected by the muscles of the throat, which in dilatation receive the 

 air by the nostrils, and, contracting while the nostrils are shut by the tongue, 

 force the air to penetrate into the lungs. Expiration, on the contrary, is performed 

 by the muscles of the lower belly. The embraces of the male are long continued. 

 His thumbs are furnished with a spongy inflation, which is increased in the coup- 

 ling season, and which assists in attaching him to the female. The ova are im- 

 pregnated at the moment of expulsion. The tadpole is at first provided with a long 

 fleshy tail, and a horny beak, and has no other apparent members but little 

 fringes at the sides of the neck. These disappear at the end of a few days, and are 

 replaced by branchiae or gills. These gills, by which they respire at this period, are 

 formed of numerous small tufts attached to four cartilaginous arches placed on 

 each side of the neck, adhering to the hyoid bone, and enveloped in a membra- 

 nous tunic covered by the general skin. The water which enters by the mouth 

 passes in the intervals of the cartilaginous arches, and is extruded sometimes by two 

 openings, sometimes by one, in the middle or left side of the exterior skin, accord- 

 ing to the species. The hind feet of the tadpole are developed by degrees, the 

 fore feet being developed under the skin, which they afterwards pierce; the tail 

 is gradually absorbed; the beak falls off, and discovers the true jaws, which 



