118 BRITISH SERPENTS. 
with the zigzag line almost black, occurs in the male, 
but I 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 
cestive that in both 
other correct. It is at least sug 
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 onee arises here, How is 
the age of any given adder to be determined? I readily 
adinit 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 
