REPTILES. 



The remarkable beings which are classed together under the general 

 title of Reptiles, or creeping animals, are si3read over those portions 

 of the globe where the climate is tolerably warm, and are found in the 

 greatest profusion under the hotter latitudes. 



Some reptiles inhabit the dry and burning deserts, but the generality 

 of these creatures are semi-aquatic in their habits, are fitted by their 

 structure for progression on land or in water, and are able to pass a 

 considerable time below the surface without requiring to breathe. This 

 capacity is mostly the result of the manner in which the circulation and 

 aeration of their blood is effected. 



In all mammalia and birds the heart is divided into a double set of 

 compartments, each having a direct communication with the other. In 

 the Reptiles, however, this structure is considerably modified, so that 

 the blood is never so perfectly aerated as in the higher animals, and is 

 consequently much colder than in the creatures where the oxygen ob- 

 tains a freer access to its particles. 



In consequence of this organization, the whole character of the Rep- 

 tiles is widely diflTerent from that of the higher animals. Dull sluggish- 

 ness seems to be the general character of a Reptile, for though there are 

 some species which whisk about with lightning speed, and others, espe- 

 cially the larger lizards, which can be lashed into a state of terrific 

 frenzy by love, rage, or hunger, their ordinary movements are inert, 

 their gestures express no feeling, and their eyes, though bright, are 

 stony, cold, and passionless. 



The young of Reptiles are produced from eggs, being mostly hatched 

 after they have been laid, but in some cases the young escape from the 

 eggs before they make their appearance in the world. As a general 

 fact, however, the eggs are placed in some convenient spot where 

 they are hatched by the heat of the sun. 



TORTOISES. 



The very curious reptiles which are known by the general name of 

 Tortoises are remarkable for affording the first example of a skeleton 

 brought to the exterior of the body — a formation which is frequent 

 enough in the lower orders, the crustaceans and insects being familiar 

 examples thereof. In these reptiles the bones of the chest are devel- 

 oped into a curious kind of box, more or less perfect, which contains 



4sy 



