as in the well-known case of a cut through the trunk of a tree, in 
which the counting of the rings gives the age of the tree in years. 
In the scales shown in figure 11 it will be seen that the broad 
Fic 11.—Scales of two plaice of about the same length, the left of one nearly two years 
old from Passamaquoddy bay, the right of one more than six years old from 
the Bay of Islands, Newfoundland. 
like the teeth of a comb. 
- 
free when the scale is still in the skin of the fish, the remainder being 
A short part of this end of the scale is the cnly part uncovered and 
covered by the other scales just in front. 
end of the scale is fringed with teeth, 
The covered part is — 
The lines 
are partly distant from each other and 
marked by many parallel lines, which are roughly in the shape of 
half circles, the centre of which is a point—the centre of growth— 
, 
just inside the middle of the toothed end of the scale. 
which are called circuli 
partly crowded together. 
The plaice begins to grow in the spring 
and this 
In the part of 
warm up, 
CF. 
at a rapid rate as soon as the water starts to 
rapid growth lasts during spring and early summ 
In late 
summer and in autumn the growth of the fish gradually lessens 
and the scale formed during this slow growth has the circuli close 
the scale formed at this time the circuli are far apart. 
21 
