REPTILIA. 85 



entirely naked. To this genus belongs the common Orvet 

 or Slow Worm. 



ORDER IV. BATRACHIA. 



No carapax, nor scales, nor nails ; body covered with a 

 naked skin; limbs most generally; a heart with two auricles 

 and one ventricle ; two equal lungs, to which, at first, are 

 added branchiae supported on each side of the neck by carti- 

 laginous arches. The greater part lose these branchiae and 

 the apparatus which supports them in passing from the con- 

 dition of Fish to that of Reptile. Three genera among which 

 are the Protei retain them for life. Eggs enveloped in a 

 simple membrane, and becoming greatly enlarged in the 

 water. Two families. 



FAMILY I. RANA. FROG. 



Four legs, but no tail, in their perfect state. Head flat ; 

 muzzle rounded; opening of the jaws wide; anterior feet 

 short, terminated by four toes ; the posterior longer and fre- 

 quently having six. In the greater part there is a soft tongue 

 not attached to the bottom of the gullet, but to the edges of 

 the jaw, and folding inwards. Skeleton without ribs ; inspi- 

 ration being effected by a motion of deglutition, expiration by 

 a contraction of the abdominal muscles. The young, which 

 issues from an egg, is called a Tadpole', it is provided with a 

 long fleshy tail, and with a little beak of horn; and its only 

 limbs are small fringes at the side of the neck which disap- 

 pear at the end of a few days. Respiration is effected by 

 branchiae affixed to the hyoid bone ; the water which enters 

 the mouth and traverses them, issues by one or two openings. 

 At a certain period these organs decay; the horny beak falls; 

 the intestines become shortened; to the herbivorous regimen 

 succeeds a carnivorous one ; the tail is insensibly absorbed ; 

 the legs perceptibly develop themselves, the hind ones ap- 

 pearing sooner than the anterior, which grow beneath the 

 skin. Four remarkable genera. 



