OF REPTILES IN GENERAL. 101 



and apparent in the structure of a loathsome reptile, as 

 in the formation of a paradise-bird. 



(105.) The general structure of this class may be 

 thus briefly explained. The body is either covered with 

 scales, as in lizards and serpents, or enclosed in a hard 

 horny covering, as in the tortoises. The feet are always 

 short, but in the serpents these members are entirely 

 wanting. Their blood is red, but cold ; hence, as M. 

 Cuvier remarks, they have no occasion for teguments 

 capable of retaining heat. In all cold-blooded animals, 

 not aquatic, the vital principle is much stronger than in 

 those whose blood is warm. The cruel experiments of 

 Redi, and the naturalists of that school, while they 

 establish this fact, are too revolting to be detailed. The 

 tortoise will continue to live and exhibit voluntary 

 motion, after having lost its brain, and even for a con- 

 siderable time after decapitation : the heart will beat 

 for several hours after it has been taken out, and its loss 

 does not hinder the body from moving, long after its 

 extraction. All reptiles proceed from eggs *, which are 

 deposited by the female, and left to hatch. In general 

 the young emerge from the egg under the form they 

 always retain. 



(106.) The relations of this class to the other verte- 

 brated animals, and to the Mollusca, is in many respects 

 obscure. No one can doubt that they are one of the most 

 imperfect divisions of the Vertebrata; that is to say, 

 having a structure greatly inferior to that seen among 

 quadrupeds or birds. The class is therefore aberrant, 

 and makes the nearest approach of any other to the 

 molluscous animals. It has long ago been remarked 

 that the tortoises, more than any other reptiles, evince 

 the greatest affinity to the Cephalopoda, or cuttle-fish ; 

 but it is also obvious, that between these two groups 

 there is a wide and strongly-marked distinction. No 

 animal, it is true, yet discovered, militates against these 

 relations ; but the numerous fossil remains attest the 

 fact, that the Cephalopoda was a class of animals much 



* Excepting a few almoit solitary instances of viviparous species. 



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