2% of the year class 1904, in 1909, over 40%. A great immigration to the spring 
herring shoals from those of the fat herring must therefore have taken place in the mean- 
time. This occurred during the spring fishery of 1908, which explains the paucity of 
these fish in the early (February) catch, and the great contrast presented by the later 
(April) hauls. The immigration is not however, restricted to this period; it continues, 
and not until 1910 do we find the highest percentage (77.3) among the spring herring, 
(vide Table p. 26). This agrees with the fact that the fat herring samples, at any rate 
up to the summer of 1909 inclusive, contained large percentages of the 1904 year class, 
whereas in 1910 this year class had almost entirely disappeared from the fat shoals. 
A far closer comprehension of this emigration from the fat herring shoals and cor- 
responding immigration to the shoals of large and spring fish is furnished by an inter- 
esting observation made by LEA, which he describes as follows: “A very large part of 
the rich 1904 year class have lived, during their first years, in northern Norwegian wa- 
Fig. 23. Scales of two five year old herring from the North Coast of Norway; 
a, normal growth, 6, “marked” fish (LEA). 
ters, and it appears that most of them, in 1906 (their third year of life) exhibited an 
unusually poor increment of growth. The scales, which furnish, as it were, a graphical 
illustration of the growth, reveal this most distinctly. If we observe the scale marked 
b in Fig. 23 we find that the distance between the second and third winter rings is re- 
markably small. For purposes of comparison, another scale, marked a, is shown, 
illustrating the manner in which the winter rings are generally found to lie. 
“Most of the herrings from the northern Norwegian waters exhibited scales as that 
marked b. The only reasonable explanation of this would seem to be that these fish 
in 1906 (their third year of life) must have lived under conditions unfavourable to their 
growth. The theory of a racial phenomenon is here untenable, since the fact is only 
apparent in those of the Norwegian herrings which occurred in northern Norwegian 
waters in 1906. 
“The peculiar appearance of these scales enables us to distinguish them from others, 
and the presence in a sample of a large number of herrings having such scales indicates 
more or less certainly that one has to deal with fish which have lived in northern Nor- 
vo 
