Eee 
14.4 % and 17.6 %, and may earlier have been very numerous. The figure shows two 
distinct summits for this year class, in 1908 and 1909; it is of especial interest as being 
the only rich year elass of the disappearance of which the material gives us any inform- 
ation. In the last year in which this year class was present in considerable numbers, 
(1909) it was 10 years old. 
The investigations as to the average composition in point of age of the large and 
spring herring thus strongly support the conclusions arrived at from the study of the 
fat herring, viz; that a single year class has played a very great part in the stock of herring 
during the past years, and it would seem difficult to believe that so many facts, all tend- 
ing in the same direction, should be due to mere accidental circumstances in the samples 
examined, rather than to general conditions applying to the whole of the stock. 
Comparison of different samples as a means of checking results. 
In dealing with a question of so great importance, however, the available material 
should naturally be utilised to the greatest possible extent for the elucidation of the 
problem. We will therefore, as regards the large and spring herring, proceed to consider 
1906 05 04 03 02 Of 1900 99 
Fig. 17. Spring herring district. Fig. 18. Spring herring samples 1910. Composition 
in point of age. 
the different samples separately, and not merely from the point of view of average re- 
sults. Such consideration of the samples affords a clearer view, not only of the accuracy 
of the average results, but also as to how many and how large samples are required 
in order to give an idea of the composition in point of age and size of the stock. 
This latter point is of the greatest importance, not least from a practical point 
of view. I have therefore shown, in the following table, the results of age deter- 
