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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 vertebrated 

 animals which presents the same variety of form and structure. 

 Among quadrupeds, the tiny Field-mouse (Mus messorius) 

 that suspends her nest from a blade of corn, resembles, 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 Shell-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 opinions are entitled to great respect, it will better 

 suit the simplicity which is desirable in an elementary work, 

 to adhere to the former arrangement, and treat of them as 

 Tortoises, Lizards, Serpents, and Frogs. 



