84 THE STORY OF REPTILE LIFE. 



cricket-like noise, intended apparently as a decoy 

 for grasshoppers, on which the wily performers 

 largely feed. Stridulating organs of this kind 

 are rare among vertebrates. 



From the Geckos we must pass now to the 

 Lizards proper, which in numbers surpass all 

 other orders of Reptiles, since, up to the present 

 time, more than 1500 distinct species have been 

 described. The general form of the body we 

 have already indicated (p. 79), consequently 

 we are free to proceed to discuss the various 

 modifications which have taken place therein as 

 a result of the struggle for existence. These 

 take the form of adaptations to various and often 

 widely different modes of life. In this connection 

 it is a point of some significance and extreme 

 interest to remark that the degree of modification 

 varies to a surprising extent, even among rep- 

 tiles living amid precisely similar surroundings ; 

 some of these creatures undergoing profound 

 changes, obviously directly adapted to their 

 peculiar habitat, whilst others apparently succeed 

 in holding their own without suffering any very 

 obvious transformation. 



The common English Lizards Lacerta mvipara 

 and Lacerta agilis, and the Giant monitors serve 

 as admirable examples of the ground-dwelling 

 forms which have succeeded in holding their 

 own without undergoing any conspicuous modi- 

 fication of form. Both the English species are 

 heath dwellers, the vivaparous lizard exhibiting 

 a preference for moist places, and occasionally 

 taking to the water, being a good swimmer. 

 The monitors are to be met with in Africa, 



