60 MARVELS OF FISH LIFE 
The silvery appearance of the parr is due to the 
fact that the scales become covered with the light reflect- 
ing spicules already mentioned in an earlier chapter. 
If the scales are removed from a smolt the parr 
markings, due to the arrangement of pigment cells in 
the skin of the little fish, are seen as clearly as ever. 
In April and May the smolts drop down into the 
sea and disappear. 
It has been comparatively easy to watch the parr 
and the smolt while in fresh water, but when the smolt 
goes to sea it is a totally different matter. 
During the last fifty years the hfe of the salmon 
has engaged the attention of scientists and fishermen, 
and the earlier knowledge gained about his life in the 
sea has been obtained by the recapture of specimens 
that had been marked. 
At first the method of marking fish mainly consisted 
in cutting the fins, and this rough and ready method 
is probably responsible for many of the conflicting state- 
ments in the description of the life history of the salmon. 
Latterly, fish have been marked by means of plates or 
silver wire attached to the dorsal fin, each plate or wire 
bearing a distinguishing number, and by this means 
reliable information has been gained. 
In addition to marking, the fact that the age of 
many bony fishes can be read by the formation of their 
scales has been made use of. 
The scales consist of bony plates, which are partially 
buried in pockets in the skin, and they overlap one 
