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CHAPTER IX. 
THE ADDER—Continued. 
COLOUR VARIATION IN BRITISH ADDERS. 
COLOUR VARIATION AND PROTECTIVE COLOURATION—COLOURS 
FOUND IN ADDERS—FACTORS CONCERNED— HEREDITY— 
CLIMATE—LOCALITY—SEX—AGE—CONCLUSION. 
EVEN a very casual observer of a collection of British 
adders could hardly fail to notice the ereat variety of 
colouring they exhibit. In this chapter an attempt 
will be made to examine, and if possible to throw 
some heht upon, the causes of these variations. To 
state the problem clearly it is necessary at the out- 
set to recognise the distinction between protective 
colouration 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. “The disguises worn by 
animals, the exquisite adaptation of the colours of 
