249 The Common Fel 
on this account escape detection. This is certainly a matter well 
worth investigating. 
To catch the eels on their downward course and allow them to 
escape on their upward is not a wise procedure, for by the time they 
are going seawards they have done all the damage they can do, 
while if caught on their upward progress a marketable size two or 
three years old could be got. This arrangement would prevent an 
enormous destruction of salmon fry, for I consider the eel by far the 
greatest enemy that salmon and trout have. The young of the salmon 
hide under stones during the winter, and an eel after a fish is like a 
ferret after a rabbit—it can not only go wherever a trout can go, but 
its body remains concealed under a stone, with only its mouth and its 
eyes exposed to view. There he lies in wait for any living thing that 
comes near him. 
Not until April 1906 was it known where eels spawned. Professor 
Grassi, of Rome, discovered the breeding-ground to be out in the 
Atlantic Ocean from Norway, Denmark, France, and Spain, in some 
parts 1000 miles from shore, at a depth of 560 fathoms, with the 
eel larva 50 to 100 fathoms overlying this depth. The generic 
name ‘‘ Leptocephalus” was applied to the eel larve before their 
history was known. 
The Leptocephalus develops from the egg, grows to the length 
of about 3 inches, then ceases to feed until the metamorphosis 
is complete and the little fish has become an elver. These larve 
have perfectly clear ribbonlike bodies, which are as transparent as 
glass, and free from colouring, except in the case of the eyes, which are 
black. Their length is about 3 inches and their breadth three-eighths. 
The metamorphosis takes place in four stages, and when complete 
the length is reduced to about 23 inches, and the width to a little more 
than one-eighth. When in the sea they are known as glass elvers, 
but on arriving in fresh water pigment is developed in the skin and 
they are now known as elvers. The times of migration to our shores 
vary very much. In some localities it takes place in December, and 
in others not till April. In the Shannon district it is as early as 
