REPTILES. 
285 
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 o 
the medium, whether air or water, in which they reside. 
Like Fi sties, 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. 1 hey 
increase by eggs, which are laid singly, and are always 
enveloped in a calcareous covering, which, according to the 
neater 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 resemblanoe to those of Bums. 11 
several rospects there is an advance in organisation over 
the Amphibians ; the heart is composed of two auric es 
and one ventricle ; the respiration is performed by means 
of luno-s exclusively; and there is no metamoip iosis m 
the Class, the animals presenting the perfect oim even 
“e if more diversity in form and structure among 
the animals that compose this Class than among lose o 
