LIZARDS 233 



hind-limbs are fixed and the body stretched out once more (line 3), it is 

 brought forward by the distance a. The animal derives support in creeping 

 by propping the scales on the under side of the body against any inequali- 

 ties of the surface. Prom this manner of progression we can understand 

 the length and the great mobility of the body of these animals (see 

 vertebrae of snakes) ; while it becomes at once evident that the more the 

 limbs of a reptile are atrophied, the more elongated its body needs to 

 become. Hence limbless lizards {e.g., the blind-worm) must of necessity 

 assume the shape of a snake. 



(b) The tail executes similar undulating movements, and consequently 

 helps in pushing the body forwards. It, too, is accordingly very long 

 and flexible. Its importance as an aid to locomotion is at once evident 

 from the fact that lizards which have lost their tails are not able to run 

 nearly as fast as unmutilated specimens. Moreover, the motions of such 

 an animal become less steady, showing that the tail acts in addition 

 as a sort of balancing-rod for the maintenance of equilibrium ; while, 

 finally, by forcibly striking the ground with its tail the lizard can execute 

 wide and rapid leaps, which is of considerable advantage to it, especially 

 in the capture of butterflies. If the tail is broken off when seized by an 

 enemy, it grows again, but not to its original length. 



(c) The long sharply-clawed toes enable the animals to climb nimbly 

 and safely along rocks and on low bushes. 



3. Mouth. — Such prey as has been captured while leaping and 

 running, the lizard can only kill and crush with 



(a) Its small teeth, which are placed in the jaws and palate (not 

 lodged in sockets), and directed backwards (see snakes). 



(b) The gape of the mouth is wide, as the prey has to be swallowed 

 whole and unmasticated. 



F. Reproduction. 



The female in June lays from five to ten white eggs (about the size 

 of sparrows' eggs) in the sands or between stones. They are hatched by 

 the heat of the sun's rays, and the young emerge mostly in August. 



For hibernation, see p. 230. 



Other Lizard Species. 



The Common or Viviparous Lizard (L. vivipara) is slightly smaller 

 "than the sand lizard. These two species never occur in the same 

 localities, since the last-named species pursues and consumes the young 

 of the common lizard wherever it can obtain them. Consequently the 

 latter retires to places where it is beyond the reach of its inveterate foe 



