CHAPTEE XIII 



motion, hiding-places, hibernation, haunts, distri- 

 bution, migration, play, battle, enemies, dis- 

 ease, age, and size of reptiles 



Means of Motion 



IS^owHERE has Nature been more liberal in modes 

 of motion than in the Reptiles. Here she has run 

 the whole scale. Many swim ; some wriggle only ; 

 others burrow : most walk on four feet, a few on 

 two ; one glides or sails on the air like a flying 

 squirrel ; while another ancient form doubtless had 

 well-sustained flight, Uke that of a bat. As varia- 

 tions of these methods some have leaped on two legs 

 as a kangaroo, and others have waded in a sort of 

 upright, half -floating way in deep water. This record 

 can not be excelled in any class of creatures. Be- 

 sides mere wriggling, the snakes (having lost their 

 limbs by indulging too largely in that) seem to have 

 needed some means of slow, gradual motion ; where- 

 upon T^ature loosed the hold of the ribs from 

 the breast-bone, caused the bone to absorb, bi'ought 

 the tips of the ribs to the lowest surface, connected 

 them with the scales below, and strung to each a 



separate active muscle. Along the back-bone she 



111 



