THE ADDER, P15 
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. Itis a very tempting 
one, nevertheless; for adders do, like trout, keep very 
much to the same spot. But the crucial test is this: 
If the varying colours of adders are due to the actual 
spol they frequent, then all the adders taken in any one 
given spot ought to show 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 before 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 Garway 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, because no two are 
exactly alike, even tn the same locality, which is the very 
