OF LIFE IN GENERAL. 



323 



Heincke seems to be of the opinion that these differ- 

 ences are largely the direct result of the environment, 

 for he says that all the local races of herring are sub- 

 jected to a very complex combination of environmental 

 conditions, and that these react upon them to produce 

 their especial characters. The White Sea herring is 

 the most divergent from the general mean in respect 

 of other characters besides the number of vertebra) and 

 of scales. Thus it has only 2 to 10, or, on an average, 

 6 vomerine teeth, mostly in a single series, whilst other 

 races have, on an average, 10 to 20 teeth, arranged in 

 several series. 



Heincke finds that the spring herring and the au- 

 tumn herring are two more or less distinct races, not 

 only in the Baltic Sea, but in other localities as well 

 (West and East coasts of Scotland, North Sea, etc.). 

 The spring herring differs from the autumn herring in 

 that it is, as a rule, considerably larger; it has longer 

 anal fins, and often a larger number of vertebrae. It 

 always has a smaller number of keeled ventral scales, 

 and a narrower skull, and very seldom has less than 9 

 rays in its ventral fins. Autumn herring with 8 ven- 

 tral fin-rays occur fairly frequently, however (20 to 30 



