114 BRITISH SERPENTS. 
light-brown description ; while those found in dark 
woods, or on black soil, no less obviously come under 
the description of black, dark-brown, or olive-green. 
Very simple, but unfortunately not borne out by the 
facts. Then the case of the colour variation in fish at 
once occurs to the mind. I know nothing about fish 
myself, but no one can live in the neighbourhood of a 
trout-stream without hearing others discourse on the 
varying colours of trout. A correspondent of mine, 
who lives at Newcastle Emlyn, South Wales, where 
adders are very common, writing on this subject, says: 
“The varying colours are, I think, due to the actual 
spot that the adder frequents, and to which they get 
adapted lke a trout. For instance, on open slopes 
facing the south, they [7c., adders] get a reddish tinge 
like parched grass. In the Tivy, trout vary in tint 
within a few yards. Thus, one taken in a deep rocky 
pool would be a deep green on the head and back, 
and one taken a few yards away in a shallow stream 
would be a heht gravelly-golden tint.” Now my cor- 
respondent is a good fisherman and observant, and 
doubtless all practical fishermen will agree that what 
he says of the trout in the Tivy is true of trout else- 
where. Whether he is correct in attributing the 
variation of trout colourines entirely to their habitat, 
I leave to authorities on piscatorial matters to say, 
But having noticed this in trout, he very naturally 
concludes that the case of the adder is analogous. 
It should always be remembered in science that 
