418 Es, ALLEN, 
rings will be the length which the fish had at the time the ring was formed. 
This will be clear from the diagram Fig. 7. 
Fig. 8 illustrates the composition of three samples of Norwegian Spring 
Herring taken in March, 1907, and analysed by Dahl (3), by an examina- 
tion of the scales, into age groups. It will be seen that the majority of 
Total curve 
924 Herrings 
SS OS ois 
<a Sa eae 
Zi 28) 29 250M 33 327) 552 054 55 36. 37 38 
Centimeter 
22. 23' 24 29; 26 
Fic, 8.—Analysis of three samples of Norwegian Spring Herring 
taken in March, 1907, into age groups. (After Dahl.) 
the fish belong to the IV, V, VI, VII and VIII year-classes, the best- 
represented class being IV. The position of the apex of each curve gives 
us the size of fish most frequently found in each age group. 
Samples of Norwegian Spring Herring have been examined in this 
way every year since 1907 and the results obtained are given in the 
following table (p. 419), the number of fish belonging to each year-class 
being expressed as a percentage of the whole sample (Hjort, 12, p. 219, 
Table I). 
An examination of the figures in this table reveals a very remarkable 
fact. If we commence with the year 1908, we see that 34-8 per cent. of 
the fish belong to the year-class IV, that is to say, they are fish which 
were born in the year 1904. We see further that no other year-class 
is nearly as well represented, the next in order being the IX year-class, of 
which the sample contains 14-4 per cent. Now look at the percentages 
for the year 1909; the best represented class is the V year-class, with 
45-7 per cent. But in 1909 the V year-class is composed of fish born in 
