22 
BULLETIN OF THE BUREAU OF FISHERIES 
the fish themselves fall into fairly distinct size groups corresponding to different 
ages, and the size groups of eggs is merely a reflection of this condition. 
The acceleration of the growth of the eggs during the last growing season is 
shown clearly in Figure 1. This graph shows the proportional changes in the size 
of the eggs of fish with ocean nuclei during their third year — first, for those mature 
fish taken inside the river; second, for the mature fish taken outside; and third, 
for the immature fish taken outside. The points on this graph indicate the position 
of the weighted arithmetic means of the logarithms of the egg sizes.' 
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Fig. 1. — Changes in the sizes of the eggs of females in their third year, ocean nuclei, during 
the course of the fishing season. Columbia River and the ocean off the mouth of the 
Columbia 
In addition to the fact that the eggs of the immature fish are distinctly smaller, 
it is apparent from Figure 1 that the slope of the curve for the mature fish is much 
steeper than that for the immature fish, indicating unmistakably that the eggs of 
the maturing fish are increasing in size, not only actually, but relatively, at the 
more rapid rate. If the two curves were projected back into the months preceding 
the opening of the fishing season, they would evidently meet some time in March 
or early in April, which would indicate that the differential growth probably begins 
at about that time. 
This differential growth of the eggs of the maturing fish is shown in another 
way in the following table, which gives the proportional size of the eggs in relation 
to the length of the fish in a few selected groups chosen largely because they were 
better represented than the others. 
' See pages 24 and 25 for an explanation of the use of logarithms in this connection. 
