COLOUR VARIATION IN BRITISH ADDERS. 49 



(/) SLOUGHING. 



But while sex and age are, in my opinion, the two great factors 

 in colour variation, there is another point to be considered in 

 the special case of reptiles, viz., sloughing. Casting the slough 

 does not really affect the production of colour, but the colours 

 are undoubtedly brightest immediately after that process. Thus, 

 the most brilliant adder is a young male just after casting the 

 slough, while the female shades are also brighter then than at 

 other times. The effect of sloughing is far more noticeable in 

 the cases of the grass snake and smooth snake, with which we 

 are not dealing to-day. 



CONCLUSION. 



Our conclusion, then, is that colour variation of adders is 

 mainly a matter of sex and age, certain colours being char- 

 acteristic of one sex or the other, that young males are the most 

 brilliant, old females the dullest in colour, that the colours are 

 best seen after sloughing, and that locality cannot account lor 

 the variation, even if it is responsible for some slight resemblance. 



REPTILIA IN CENTRAL DORSET. 



The following is a record of the reptiles taken and measured 

 during a few days' reptile hunting at the end of April, 1901, 

 within a radius of about three miles of Buckland Newton, 

 Central Dorset. I have to thank my friend, the Rev. F. W. 

 Brandreth, a member of the Dorset Field Club, for giving me the 

 opportunity of making this investigation : 

 i. Adder, Male, 22 inches. 



