

#■.- 



[INTRQDUCTIQNI 



I. Distinction of Batrachians from Fishes and Reptiles 



The Batrachians represent a Class of Vertebrate animals 

 occupying a position between Fishes and Reptiles. There is con- 

 siderable variation in general appearance among the different 

 living members of the Class, so that a Batrach ian is n ot as easily 

 defined and identified as is a fish,_a bird, or a mammah There 

 islib one chafactei^istic By which it may be known, as there is 

 in each of these other Classes. 



Batrachians, however, are distinguished from Fishes by sev- 

 eral easily recognizable characteristics. They usually have piairgd 

 limbs furnished with Jingers and loes (pentadactyle limbs), and 

 never have fins stiffened by bony ray^ (although they may have 

 fins soft and filmy in character in the young stages). With the 

 exception of one order (Apoda), tjiey do not have scales, but pos- 

 sess a skin either smooth and slimy or rough with warts and 

 nearly dry*.'"' TTsTies'TreatHe throughout their lives by means of 

 gills, but the Batrachians, while usually living in the water and 

 breathing by gills in the early stages of life, as |^ rule breathe 

 during adult^Jife by means of l ungs, and are more or less well 

 developed itor land life.^ 



A popular distinction from the Reptiles is not easily made, 

 since Batrachians and Reptiles sometimes correspond almost ex- 

 actly in form. That is, they both have limbs of the pentadactyle 

 type and in the case of Salamanders (Batrachians) and Lizards 

 (Reptiles) both possess tails and elongated bodies. In fact, some 

 of the common Salamanders are popularly called Lizards, show- 

 ing the great superficial resemblance of certain members of the 

 two Classes. 



However, Batrachians and Reptiles are very different indeed 

 in all fundamental points. Instead of a more or less smooth and 

 slimy skin, Reptiles have a skin protected by overlapping scales, 



^There are certain technical points of difEerence in characteristics of the skeletons; i.e., the 

 vertebrfe of Fishes are never pseud ocentrous or ngtocentrous. The Batrachian has two occipital cou=_- 

 dyles, except in the case of some Stegocephali. The Batrachian is characterized by the presence of a // 

 jfenestra ovalis and stapes ancQii internal nares. 



" I 



