TO BRITISH SERPENTS. 
the skin is in an unhealthy condition, the snake has 
more difficulty, or makes no effort, and the cuticle 
comes off in pieces.” + This supposition that the health 
of the serpent is the determining factor in the slough 
coming off whole or in pieces seems to have become 
widely believed; at any rate, I have often heard 
it mentioned in conversation. But Miss Hopley’s 
favourite ophidian is the ring snake, about which 
she has written so much and so delightfully, and 
she seems to have had this species in her mind when 
writing the above-quoted sentence. At any rate, I 
have not found it to be the case in adders, unless the 
adder population of Herefordshire and Monmouth- 
shire is assumed to contain a very large proportion 
of invalids, which is hardly likely to be the case, con- 
sidering the large size they grow to in these counties. 
My experience with adders is that the slough is more 
often cast in pieces than whole. The whole process 
resolves itself into two distinct phases — first, the 
separating of the external cuticle from the under- 
lying skin; and second, the dropping or leaving 
behind of the portion to be east off. The first is a 
physiological process, explained before; the second is 
a mechanical process, dependent on external circum- 
stances, over which the snake may have no control. 
I regard it as almost accidental, when the slough once 
is loosened from the body, whether it comes off whole 
or im separate pieces. In other words, it all depends 
' British Reptiles, p. 27, 
