110 BRITISH SERPENTS. 
their fur or feathers to their surroundings, are part 
of the general harmony existing throughout nature.” 4 
Thus every sportsman knows how difficult it is at 
a little distance to distinguish partridges from the 
earth on which they are crouching. Many serpents 
also afford examples of this protective colouration, 
the British ring snake, for example, being very much 
the hue of the grass among which it moves and 
looks for food. But some serpents are most 
brilliantly coloured, and thus rendered conspicuous. 
These will generally be found among the poisonous 
species, whose formidable weapon of defence makes 
it unnecessary for them to be otherwise protected 
from attack. Indeed their very striking colours 
may be regarded as in a sense protective, as giving 
warning of their presence. But this protective 
colouration is quite a different phenomenon from 
that of colour variation. This latter term is descrip- 
tive of the varying colours seen in any given species, 
whether that species exhibits any protective colour- 
ing or not. 
In the particular case under notice the problem is 
not to account for the specific markings and colours 
seen in adders, but, granting that adders arc marked 
and coloured im a given manner, why do these colours 
exhibit such variation? In other words, what is 
the cause of the striking colour variation to be seen 
in any collection of British adders ? 
' Packard. 
