116 BRITISH LIZARDS 



" To state the problem clearly, it is necessary at the 

 outset to recognise the distinction between protective 

 coloioration and colour variation. The former term is 

 used to describe the resemblance in appearance between 

 many creatures and their surroundings, by means of 

 which resemblance the members of the species are 

 protected from attack, and thus the species from 

 extinction. Thus every sportsman knows how difficult 

 it is at a little distance to distinguish partridges from 

 the earth on which they are crouching. . . . But this 

 protective colouration is quite a different phenomenon 

 from that of colour variation. This latter term is 

 descriptive of the varying colours seen in any given 

 species, whether that species exhibits any protective 

 colouring or not." ^ 



In the present case, in other words, the problem is 

 not to account for the specific markings and colourings 

 of the different lizards which may be protective or not, 

 but to ascertain the reason why these specific markings 

 and colours exhibit such striking variations, i.e. to solve 

 the problem of colour variation in lizards. 



Every student of natural history knows that there 

 are many factors which are usually considered to take 

 part in producing colour variation in animals. Most 

 of these factors, perhaps, will fall under one or other 

 of the following : — 



Variations due to Heredity. 

 „ ,, Climate. 



^ Leighton, British Serpents, pp. 109, 110. 



