18 THE ROYAL SOCIETY OF CANADA 
For comparison with this scale one from the smallest adult fish 
examined (65.5 cm. in length) is shown in Plate VI. fig. 1. It is un- 
necessary to go into details regarding this; it shows exactly the same 
zones as the larger fish, the only difference being that the zones are not 
so broad. This fish, accordingly, was also its way to the spawning 
grounds in its fourth year. And since the same story is told by the 
scales of all the fish with lengths between these extremes, that isto say of 
fish of 73.0, 76.0, 80.0, 82.0, 82.5, 84.0, 89.5, 91.5, 92.5, 101.0 and 108 
em., the conclusion is evident that all adult Spring Salmon, no matter 
what their size may be, are four year old fish, that the typical life-cycle 
of O. tsehawytscha is one of four years. 
fee 3rd year 
ne. 
ann 
2nd year 
in sea. 


Ist year 
in sea. 
Fresh 
he — water 
| dues 
.5 92.5 101 112 

Text-fig. 4.—Diagram showing the relative amounts of growth in successive years 
as shown by the scale-markings of adult Spring Salmon of various 
sizes. 
But while there is perfect unanimity in the scale records as to the 
length of the life-cycle, there are nevertheless variations ‘n detail which 
seem to throw some light on the great difference in the size of individual 
fish. Thus while in both the 112.0 em. and the 65.5 cm. fish the 
growth during the first two years in the sea was fairly uniform and that 
of the third year somewhat less, the two individuals differing in the 
amount of total growth rather than in the amounts of growth in suc- 
cessive years, other fish show quite different conditions. In the diagram 
(Text-fig. 4) I have represented the relative amount of growth in each 
