LIFE HISTORY OF LAKE HERRING OF LAKE HURON 



315 



Table 11. 



-KlV ratios based on X scales and on non-X scales of several year classes of Bay City 

 herring collected in fall of the years 1921, 1922, and 1923 ' 



 The number of specimens employed is shown in parentheses. 



It is to be noted in Table 10 that where large numbers of individuals are employed 

 the ratios of two consecutive age groups vary only slightly, and that on the whole a 

 tendency exists for the body-scale ratios to decrease with the older age groups. This 

 suggests that the fortuitous fluctuations in the ratios of each collection may be due 

 to the small nmnber of specimens employed for the averages of some of the age groups. 

 As the corresponding ratios of the various collections are comparable, they may be 

 combined and treated as units. The grand averages are shown at the bottom of 

 Table 10. 



We now find that the two series of K/V ratios give consistent and comparable 

 results. Both decrease consistently with each older age group. Though the dif- 

 ference between the ratios of any two consecutive age groups is stUl small, that 

 between the extreme averages is significant. We find that the difference between the 

 grand averages of fish in years III and VI is 1.67 for the ratios based on X scales and 

 1.32 for the ratios based on non-X scales. These differences can not be accounted 

 for by random sampling; nor can they be due to the personal errors involved in the 

 measurements, as can be seen by referring to the differences given in the last column 

 of Table 12. The K/V ratios of fish of several age groups were determined twice; 

 but the same identical scale was not always employed for the two ratio determinations 

 of an individual. This and the fact that only a few specimens were used should 

 make the differences between the two series of ratios represent the maximum. And 

 yet, the differences between the extreme grand averages of Table 10 equal or exceed 

 those of Table 12. The former may then be significant. Another factor might 

 possibly be considered significant here. I found (p. 283) that the big fish of an age 

 group possessed more scales in the lateral liae thaa the small fish. I found, also 

 (p. 279), that the size of the scales varies inversely as their number in the lateral Una 

 in an age group, but it is possible that the average size of the scales of the large fish with 

 the greater number of scales is about the same as that of the scales of the small fish with 

 fewer scales. If age groups II and III of Table 10 are represented by the bigger 

 fish of the year class, as I believe (p. 333), and the average size of the scales of these 

 bigger fish is no greater than that of the scales of the smaller, the body-scale (K/V) 

 ratios of these younger fish must then be abnormally high; the body length (K) 

 would be too high, whereas the scale length (V) would be normal for these groups. 

 If this be true, the differences between the extreme grand averages of Table 10 are 



