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 like a trout. For instance, on open slopes 

 facing the south, they [i.e., 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 light 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 colourings 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 



