FIRE-BELLIED FROGS (nat. size). 



AMPHIBIANS. 



CHAPTER I. 



GENERAL CHARACTERISTICS, Class Amphibia. 

 FROGS AND TOADS, Order ECAUDATA. 



IN popular estimation frogs and toads, together with their near relatives the newts 

 and salamanders, are regarded as Reptiles, but they are really very different, and 

 constitute a class by themselves, being in many respects intermediate between 

 Reptiles and Fishes. From the mode of life of its members the very appropriate 

 name of Amphibians has been proposed for the class, and is the one which should 

 be adopted, although the term Batrachians, w^hich more properly applies to frogs 

 and toads alone, is not unfrequently used in the same sense. Agreeing with the 

 higher Vertebrates in the structure of their limbs, which are divided into the same 

 number of segments as in Mammals and Reptiles, and supported by corresponding 

 bones, existing Amphibians are distinguished from Reptiles by the absence of any 

 ossification in the basioccipital region of the lower surface of the hinder-part of 

 the skull, in consequence of which the latter is articulated to the first vertebra by 

 means of two condyles formed exclusively by the exoccipital bones. A further 

 important point of distinction is afforded by the absence in the embryo of those 

 membranous structures known as the amnion and allantois. Moreover, the great 

 majority of Amphibians pass through a metamorphosis, or rather a series of 

 VOL. v. 17 



