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 Cecilia. To the 
second, in which feet and tail are present, the name Uvrodela is given; this 
has also been called Jchthyodi. And the third, having feet but lacking a 
tail in the adult forms, is known by the name Anura. 
The Apopa 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 UropeEta 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 branchize, 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;*retain a small opening through life. Very young larvie 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 larvee 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, bas free margins in others, or is attached along the 
center in others. The toes are without claws.f The fore legs appear first. 
© Cryptobranchus. TExcept Onychodactylus. 
