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CLASS II 

 REPTILIA.— REPTILES, 



The Class Reptilia constitutes another of the great groups of 

 vertebrated animals. Respiration is effected in some of the 

 Reptiles by lungs and gills ; in others by lungs only. The 

 blood is cold. The heart consists of three cavities. The 

 young are produced from eggs. 



The great majority of these creatures are regarded by man 

 with suspicion and distrust ; yet there is no class of verte- 

 brated animals which presents the same variety of form and 

 structure. Among quadi'upeds, the tiny Field-mouse {Mus 

 messorius) that suspends her nest from a blade of corn, re- 

 sembles, in all essential points of structure, the ponderous 

 elephant. Among birds, in like manner, the diminutive Wren 

 claims a place in the same phalanx with the majestic Condor 

 of the Andes. But who, except the naturalist, could venture 

 to affirm that the flexile Snake should be class-fellow to the 

 sheU-covered Tortoise ? 



Reptiles are most numerous in the countries of the torrid 

 zone, a few only being found in those of more temperate 

 regions. It has been well remarked, that "they can more 

 easily bear the rigours of a severe winter than suffer the 

 absence of a hot summer." The number of living species 

 which is known and described amounts to six hundred and 

 fifty-seven. They are divided by Cuvier into four orders ; and, 

 although some changes have been proposed by naturalists 

 whose opmions are entitled to great respect, it wiU better suit 

 the simplicity which is desirable in an elementary work, to ad- 

 here to the former arrangement, and treat of them as Tortoises, 

 Lizards, Serpents, and Frogs. 



