36 
ANIMAL CURIOSITIES 
then keeps a vigilant watch over them until 
the young ones emerge; the incubation period 
varying from six to nine days. 
The three species of lampreys found in 
British waters, known respectively as the sea 
lamprey, the river lamprey or lampern, and 
the small lamprey, resort to the practice of 
excavating trenches or furrows in the soil 
of the river beds for the reception of their 
eggs. Should an individual come across a 
stone during the progress of its work, it lifts 
up the obstacle with the aid of its sucker like 
mouth and places it to one side. 
The spawning habits of the salmon are 
very similar to those of the lampreys inasmuch 
as the female makes a nest or “ redd ” in the 
form of a trench excavated in the bed of a 
river. There appears to be some difference 
of opinion, however, as to how the fish accom¬ 
plishes this work, some authorities stating 
that she employs her tail in the making of 
the trench, while others are of the opinion 
that the structure is formed by the pressure 
and wriggling of the lower part of her body 
against the underlying soil. When once she 
has deposited her eggs in the redd she covers 
them up with fine gravel, and, after a period 
varying from one hundred and twenty to 
one hundred and forty days, according to the 
