COLOUR VARIATION IN LIZARDS 



117 



Variations due to Food. 



Locality. 



Age. 



Sex. 



Temperature. 



Moisture. 



Light. 



It is quite obvious that in many of the instances 

 of colour variation, two or more of the above factors 

 will be exerting their influence concurrently. For 

 example, the temperature and degree of moisture 

 which form the environment of an animal depend 

 upon its geographical distribution, i.e. the locality ; 

 while both these factors are part of all those which 

 go to make up the climate. In like manner, what we 

 term seasonal changes are associated with climate and 

 locality. The old view that brilliancy of colour is 

 dependent upon light and high temperature, is found 

 to be unsatisfactory, since it does not follow that the 

 animals of the hot and glaring desert present the 

 brightest hues, and much of the deep-sea favma is of 

 very brilliant colouring, though living in comparative 

 darkness. 



But these considerations apply to the question of 

 colour variation in its widest sense. When we come 

 to consider the problem in a somewhat restricted area, 

 many of the factors just mentioned are at once found 

 to be inoperative to a great extent. In a country the 

 size of Great Britain, it can hardly be supposed that 

 climate can be responsible for any great extent of 



