O they are called; and if the almost 
unanimous rustic opinion, with its an- 
cient tradition and reliable witness, is 
to be credited, such they are in very 
truth. Indeed, there would seem to be 
few better attested facts in the whole range of 
natural history than the pedigree of this white or 
brown thread-like creature which is found in sum- 
mer shallows and pools. Go where you will in 
the rural districts and it is the same old story. 
41 They come from horse-hairs," and in some sec- 
tions they are destined finally to become full-grown 
water-adders. It is commonly no mere theory. It 
is either an indisputable fact, tested by individ- 
ual observation, or else is accepted as a matter of 
course, much as Pliny of old accepted the similar 
natural history " discoveries " of his time. He 
says, for example, on a similar subject, " I have 
heard many a man say that the marrow of a man's 
backbone will breed to a snake. And well it may 
so be, for surely there be many secrets in nature 
