109 



CHAPTER IX. 



THE ADB'ER— Continued. 



COLOUR VARIATION IX BRITISH ADDERS. 



COLOUR VARIATIOX 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 great variety of 

 colouring they exhibit. In this chapter an attempt 

 will be made to examine, and if possible to throw 

 some light 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 



