GROWTH AND MATURITY OF SALMON IN THE OCEAN 
25 
ing percentage variation rather than actual variation in the size of the eggs, any 
confusion will be avoided.^ 
The tables and text figures have been arranged with class intervals of 0.02 in 
the logarithm of the diameter of the eggs. This is the same as saying that the 
mid-value of each class has been made 4.713 per cent greater than the mid-value 
of the next preceding class. 
If the variations in the sizes of the eggs are such that the relative maturity of 
the fish can be determined from then* study, several consequences will naturally 
follow, which may be used as criteria in determining the validity of the method. 
First, it must be possible to separate the fish taken in the ocean into at least two 
Fig. 2. — Distribution of egg sizes in two typical collections, one containing only mature fish 
and the other both mature and immature specimens 
groups on the basis of the size of the eggs — -one group corresponding approximately 
to the undoubtedly mature fish taken in the stream, and the other group char- 
acterized by distinctly smaller eggs and composed of fish that would not mature 
dming the year in which they were taken. A comparison of almost any of the 
tables on pages 81 to 88, which show the variations in the siz'e of the eggs of fish 
taken in the ocean, with a similar table of fish taken within the river at about the 
same time, will show that this is the case. One such example is shown in Figure 
2, which shows the distribution of egg sizes in a collection made just outside the 
Columbia River, July 28, 1919, and also the similar distribution in a collection 
made inside, at Warrendale, Oreg., on July 16, 1919. 
Figure 2 shows clearly that the fish taken outside the mouth of the river are 
sharply separated into two main groups — one with larger eggs, which closely agree 
''For the benefit of those unfamiliar with the use of logarithms it may be stated that the logarithm of 1 is 0, that the loga- 
rithms of all values lying between 1 and 10 are less than 1 and greater than 0, and that the logarithms of all values lying between 
1 and 0.1 lie between 0 and —1. The logarithms of values intermediate between 1 and 10 appear, therefore, as simple decimal 
fractions. Those of values intermediate between 0.1 and 1 are customarily shown as a decimal fraction preceded by the figure 
1 over which is placed the minus sign, thus: 1. The logarithm of 0.9 is therefore written 1.9642 and the logarithm of 1.1 is written 
0.0414. It is also customary to abbreviate the phrase "logarithm of" to "log"; thus, in this paper "log D" has frequently been 
used to indicate "the logarithm of the diameter." 
