118 BRITISH SERPENTS. 



with the zigzag line almost black, occurs in the male, 

 but 1 have never seen that striking contrast of colour 

 nearly so well marked in a female specimen. The 

 general colouring of the female tends to dull shades, 

 that of the male to sharp colours. Olive-green body 

 and brown markings are characteristic of the female; 

 while the yellowish body and blacker markings are 

 more significant of the males. Such, at least, is my 

 own experience. Here again analogy is suggested. 

 It is almost a rule in nature (except in the genus 

 Homo perhaps) that the male is the more attractive in 

 appearance, especially in birds. Thus we have a 

 choice of analogies ; but while neither analogy is to be 

 regarded as proof, the one may be misleading and the 

 other correct. It is at least suggestive that in both 

 the amphibians and birds — one group on either side 

 nearly related to the reptiles — this particular attrac- 

 tiveness of the males should be so pronounced a feature. 

 Female adders outnumber the males by three or four 

 to one, and when this is the case in a species, the male 

 is, as a rule, the brighter coloured of the two. The 

 full bearing of the influence of sex can, however, only 

 be appreciated when considered in connection with the 

 other most important factor — viz., age. 



6. Age. — The difficulty at once arises here, How is 

 the age of any given adder to be determined ? I readily 

 admit that after an adder has reached its full growth 

 it is very hard to say what is the exact age in years. 

 Certainly I cannot do so to my own satisfaction ; but 



