REPTILES AND AMPHIBIANS 141 



the ribs with the ventral plates, all of which end in 

 a sharp edge, directed inwards. Hence when a rib is 

 drawn forward, the edge of the corresponding ventral 

 scale is brought into a vertical position and must take a 

 grip in front ; on account of its sharpness it cannot slip 

 back, and when it is drawn to the body by the next 

 movement of the ribs, the body itself must slide forward. 

 By working the apparatus rapidly and extensively the 

 serpent advances quickly enough, but can, of course, 

 always be caught up by a human being. The lizards 

 also have the aid of this winding of the body in running, 

 and make use of the tail for the purpose ; hence a 

 lizard with a broken tail cannot get along nearly as 

 quickly as one that has the full use of that organ. 



Everyone who has tried to catch one with the hand 

 knows that the lizard's tail is easily broken off. If you 

 take hold of it by the tail, you will be sure to find this 

 quivering vigorously in your hand, and its former 

 possessor hurrying away without it. This is a great 

 advantage for the animal ; the number of tailless 

 lizards one sees in nature show best how often the 

 species is saved in this way. The chief enemy of the 

 lizards, the smooth adder, generally catches them by the 

 tail when it is after them ; and if the tail breaks off and 

 dances about in a lively way before the eyes of the 

 snake, the latter eats it and the lizard is saved. The 

 best way to catch lizards without injury is to take a long 

 grass-stalk, make a loop at the end of it, and slip it 

 carefully over the animal's head. It does not suspect 

 its danger, and is captured by lifting up the stalk. 



But nature, which has given this means of escaping 



