THE ADDER. 115 



analogy is not proof. Forgetfulness of this leads to 

 many an error. Analogy may be good, for purposes of 

 illustration or to point an argument, but in itself it 

 can never constitute actual proof. 



In this case of the trout and the adder I believe the 

 analogy to be a misleading one. It is a very tempting 

 one, nevertheless; for adders do, like trout, keep very 

 much to the same spot. But ihe crucial test is this : 

 If the varying colours of adchrs are due to the 'actual 

 spot they frequent, then all the adders taken in any one 

 given spot ought to shovj the same variety of colouring. 

 Is this so ? As a matter of fact, it is very far from 

 being the case. I have a series of adders l)efore me, 

 all taken from the southern slopes of Garway Hill, 

 Herefordshire, which shows every degree of variation 

 from ^black to light-brown, and in the same place I 

 once saw, though I did not capture, a white specimen. 

 Half a mile from this place across the Monnow Valley 

 is the northern slope of the Graig Hill, and a second 

 series of adders from this locality shows the same 

 variations as the Garivay Hill series. Now these two 

 hills facing each other, having opposite aspects, the 

 river Monnow running between, and moreover differ- 

 ing in the nature of the surface (Garway being covered 

 with bracken, the Graig wooded), produce, neverthe- 

 less, adders showing the same colour variations. I do 

 not mean to say that I could pick out an identical 

 series of adders from both localities, heccmse no tivo are 

 exactly alike, even in the same loccdity, which is the very 



