CHAPTER XXX. 



Reptilia {Reptiles). 



Like the Fishes and the Amphibians, the animals of which 

 we have now to speak are cold-blooded : that is, their 

 power of producing heat in the process of breathing is so 

 small, that their temperature scarcely rises above that of 

 the medium, whether air or water, in which they reside. 

 Like Fishes, they are mailed ; their bodies are protected 

 by a hard and dry skin, which takes the form of over- 

 lapping scales, or compact broad plates or shields, or, as 

 in some of the Lizards, a combination of these two. They 

 increase by eggs, which are laid singly, and are always 

 enveloped in a calcareous covering, which, according to the 

 greater or less ratio of the earthly element, is a parchment- 

 like skin, or a hard and brittle shell. In the latter case, 

 the eggs have a close resemblance to those of Birds. In 

 several respects there is an advance in organisation over 

 the Amphibians ; the heart is composed of two auricles 

 and one ventricle ; the respiration is performed by means 

 of lungs exclusively ; and there is no metamorphosis in 

 the Class, the animals presenting the perfect form even 

 from the egg. 



There is more diversity in form and structure among 

 the animals that compose this Class than among those of 



