XXVIII INTRODUCTION. 



Young specimens reproduce lost portions of the body with great readiness. 

 The flesh of many species is good for food. 



This class contains three orders. To the first or footless order the name 

 Apoda is applied; another title for the same has been Coecilia. To the 

 second, in which feet and tail are present, the name Urodela is given ; this 

 has also been called IcMhyodi. And the third, having feet but lacking a 

 tail in the adult forms, is known by the name Anura. 



The Apoda are snake-like or vermiform. Some of them are very long 

 and slender, others short and thick. As the name indicates, they are 

 without feet. The tail is short. The skin is smooth, slimy, and arranged 

 in transverse folds, between which rudimentary scales are sometimes found. 

 Usually but a single lung is developed. As might be expected from their 

 habits, burrowing in the ground to feed on worms, insects and the like, 

 the sight is somewhat imperfect, the eyes being partially hidden under 

 the skin. The young resemble the adults; the metamorphosis is slight. 

 Apoda are found between the tropics of both old and new worlds. The 

 only North American species yet found were taken in southern Mexico. 



In Urodela limbs and tail are present. The number of limbs varies. 

 When there are but two, as in Siren, the hinder are lacking. The earlier 

 or larval stages resemble the fishes in means of breathing and progressing. 

 Siren, Proteus, and Necturus have persistent branchiae, and their lungs 

 remain rudimentary. The majority develop lungs and lose the gills. After 

 the gills are resorbed, the branchial openings close in most cases; a few, 

 as Menopoma,*ret&m a small opening through life. Very young larvae have 

 a cutaneous gular flap, free at the hinder margin, which extends backward 

 over the branchial arches and the isthmus between them; it unites first 

 with the skin of the sternal region, and later, as the gills disappear, with 

 that of the shoulders. The process is similar in larvae of those Anura in 

 which one side is entirely closed and a small passage is left for the passage 

 of the water on the other. Many species spend the greater portions of 

 their lives in damp localities on the land rather than in the water. Those 

 preferring the land are marked by greater roundness of the tail, the 

 aquatic forms having this organ compressed and expanded. There are 

 teeth on both jaws, and most often on the palate. The tongue is pedi- 

 cellate in some, has free margins in others, or is attached along the 

 center in others. The toes are without claws.f The fore legs appear first. 



r 'Cryptobranchus. t Except Onychodaclylus. 



