AUSTRALIAN SNAKES. 15 



passing through thick grass it is probable that 

 tlie belly shields play but a small part in progression : 

 the snake moves in quick, sinuous curves, and loco- 

 motion is effected as in swimming, the grass affording 

 the resistance which in aquatic progression is supplied 

 by the water. The movements of snakes are so rapid 

 that no one unaccustomed to these reptiles can form 

 any idea of their agility. You may be holding one in 

 your hand, when, almost before you are conscious of it, 

 it has thrown two or three coils round your arm without 

 you being able to realise how the trick was done ; or it 

 may as suddenly uncoil, and, as the writer once ex- 

 perienced, have passed its tail up your coat sleeve, and 

 be half-way down your back with equal speed and facility. 

 " Except flying," wrote the late Professor Huxley, 

 "there is no limit to their locomotion." 



The progression of a snake on land will now be 

 understood ; but let us consider the case of a tree snake 

 traversing a slender branch. If rounded, the smallest 

 possible portion of the belly of the snake would be in 

 contact with the branch, a condition that would na 

 doubt render rapid movement impossible. The con- 

 formation of the tree snakes is therefore specially 

 adapted for an arboreal life, and may be more fully 

 considered. The green tree snake of Australia will form 

 an excellent example for study : on examining this 

 common species it will be seen that the belly does not 

 form an even curve, as in most snakes, but presents two 



