30 



Dan'sh authors believe that a period of eighteen months 

 elapses between two successive spawning periods in which 

 case the spring herring of one year would become the 

 autumn herring of the next, and the autumn herring of 

 one year would become the spring herring of the next year 

 but one. 



Heincke vigorously contests this opinion. He says* 

 if the intei"val between two successive spawning periods 

 exceeded one year, then we should get an equal distribution 

 of spawning herring in all months of the year. This he 

 states does not actually occur. His argument, however, 

 does not apply if the interval were approximately eighteen 

 months, since we should then still have two principal 

 spawning periods — in spring and autumn. 



It is thus seen that considerable diversity of opinion 

 exists as to the separation of the herring into two groups 

 ■ — autumn and spring spawning. 



If it be granted, for the sake of argument, that such a 

 separation really exists, it now remains to inquire into 

 the alleged differences between such supposed races. 



Heincke, in a colossal work already cited, has gone into 

 great detail Avith regard to these differences, and has put 

 forward a formula based upon body and head measure- 

 ments by means of which he claims to be able to separate 

 the two races. 



Although the present paper is devoted to a criticism of 

 Heincke's methods and results, it is more with a view of 

 re-opening the whole question for discussion than of 

 deprecating the conclusions of Heincke. 



In the first place it is necessary to explain the 

 " Formulae " of Heincke, and the methods of measurement 

 applied by him on which the formulse are based, and 

 according to which he differentiates herring into autumn 

 and spring-spawning races. 



* op. eit., p. 49. 



