322 THE EFFECTS OF CONDITIONS 



The local races of the herring have been studied by 

 Dr. Friedrich Heincke * with even greater minuteness 

 than those of the mackerel by Garstang. Samples of 

 herring from no less than a hundred different locali- 

 ties were examined, most of them in respect of about 

 25 different characters, and some in respect of over 50 

 characters. Heincke came to the conclusion that the 

 various local races of herring examined by him differed 

 from each other in the very characters which are used 

 to differentiate the species of the genus Clupea from 

 each other, though, as a rule, the differences were 

 smaller. For instance, the most extreme variations 

 noticed in the average number of vertebrae ranged from 

 57.6 in the Norwegian spring herring to 53.6 in the 

 White Sea herring, or a difference of four vertebrae. 

 The average number of vertebrae in the species Her- 

 ring can be taken as 56, or eight more than in the 

 Sprat, which can be taken as having 48. On the other 

 hand the species Clupea pilcliardus has, on an average, 

 about 52 vertebrae, or does not differ any more from 

 the sprat on the one hand, and the herring on the other, 

 than do the most widely divergent local races of the 

 herring. 



Heincke found that, as a rule, the more widely the 

 races are separated from each other geographically, or 

 rather, the more their environmental conditions differ, 

 the more do they differ in respect of certain characters. 

 For instance, the number of vertebrae, and of scales 

 between the ventral fin and the anus, showed the fol- 

 lowing mean variations: 



* ' ' Naturgeschichte des Herings," Abhandl. d. Deutsch. Seefisch- 

 erei-Vereins, Bd. ii. Heft i. u. ii. 



