GENERAL BIOLOGY 



767 



samples representing immature fat - herrings from northern 

 Norway in the years 1907-1910,^ the frequency of each annual 

 class being given in percentages of the total sample for each 

 year : — 



This table shows that the fat-herrings in 1907 consisted 

 mainly of fish two and three years old, in 1908 they were mainly 

 two and four years old, and in 19 10 again the majority were 

 two and three years old. This apparent irregularity has an 

 enhanced interest when we remember that the herrings, which 

 in 1907 were three years old, in 1908 were four years old, and 

 so on. The annual classes born in 1904 and in 1907 are 

 printed in heavy type, and the table shows a decided regularity 

 in the abundance of certain annual classes. The same regularity 

 appeared when older herrings were studied. When four years 

 old the fat-herrings begin to " migrate " away from the shoals 

 of immature herrings, and mingle with the "spring-herring" 

 shoals (the spawners). In such spawning shoals from western 

 Norway the year class born in 1904 proved to have the 

 occurrence shown in the following table in percentages of the 

 total sample analysed each year, comprising sixteen annual 

 classes : — 



Among the great number of annual classes composing the 



^ J. Hjoit and E. Lea, "Some Results of the International Herring Investigations, 1907- 

 [911," Pul>L de Cinonstance^ No. 61, Copenliague, 191 1, 



