INTRODUCTION 



Batrachians occupy an intermediate position in the 

 system between Reptiles and Fish. From the former, as 

 explained in the opening chapter on Reptiles, they differ 

 in the skull articulating by means of two condyles, and 

 by usually undergoing metamorphosis, breathing by gills 

 during the first stages of their existence, and from the 

 latter by the absence of rayed fins, as well as by the struc- 

 ture of the limbs, which conform to the type of Reptiles 

 and higher Vertebrates (Pentadactyle type). 



Before passing on to a more detailed account of these 

 animals it is well to indicate the following three orders 

 into which the class is divided. They are — 



I. The Anura, or Tailless Batrachians (Frogs and Toads). 

 II. The Urodela or Tailed Batrachians (Newts and 

 Salamanders). 

 III. The Apoda or Limbless Batrachians (Caecilians). 



The skin of Batrachians is naked, except in the Apoda, 

 which may have minute scales hidden under the skin. 



In form they vary extremely, being either short, as in 



a Frog or Toad, more or less elongate or lizard-like, as 



in a Newt or Salamander, or eel-shaped or worm-like, as 



in a few of the Urodeles and in the Apoda. The neck is 



either completely absent or very much abbreviated ; the 



head is more or less flattened ; the eyes, which are usually 



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