110 BRITISH SERPENTS. 



their fur or feathers to their surroundings, are part 

 of the general harmony existing throughout nature." 1 

 Thus every sportsman knows how difficult it is at 

 a little distance to distinguish partridges from the 

 earth on which they are crouching. Many serpents 

 also afford examples of this protective colouration, 

 the British ring snake, for example, being very much 

 the hue of the grass anion st which it moves and 

 looks for food. But some serpents are most 

 brilliantly coloured, and thus rendered conspicuous. 

 These will generally be found among the poisonous 

 species, whose formidable weapon of defence makes 

 it unnecessary for them to be otherwise protected 

 from attack. Indeed their very striking colours 

 may be regarded as in a sense protective, as giving 

 warning of their presence. But this protective 

 colouration is quite a different phenomenon from 

 that of colour variation. This latter term is descrip- 

 tive of the varying colours seen in any given species, 

 whether that species exhibits any protective colour- 

 ing or not. 



In the particular case under notice the problem is 

 not to account for the specific markings and colours 

 seen in adders, but, granting that adders arc marked 

 and coloured in a given n<<< n ncr, why do these colours 

 exhibit such variation ? In other words, what is 

 the cause of the striking colour variation to be seen 

 in any collection of British adders ? 



1 Packard. 



