of the Fishery Board for Scotland. 



281 



spring-spa wners. It must not be thought that the differences are very 

 great between the groups or that they are sharply marked off: there is no 

 fixed line in nature ; but if the habits, characters, and variations of these 

 be regarded in the herrings as a whole, the grouping is seen to be perfectly 

 natural. 



Sea-herrinr/ or Autumn-spatrners (Bank-herring). 



These dwell in the open sea from the coast of Scotland and England 

 through the whole North Sea, the Skagerrak, Kattegat, and western 

 Baltic, gradually tailiug-off in the middle portions of the eastern Baltic, 

 towards Gotland. They all, in summer or autumn, come from the open 

 sea to spawn on the sandy or stony banks which lie at some distance 

 from the coast towards deeper water. Their body-characteristics ure 

 locally very different ; in the eastern Baltic they are quite different 

 from those on the Scottish coast. But all the races of this series show 

 certain co-ordinate peculiarities in the composition of their race-characters, 

 differentiating them from the other group of winter- or spring-spawners. 

 They all display a moderate number of vertebrae (56 '5 to 55*5 on average), 

 with a high number of keeled scales behind the ventral fins (15'0 to 14'0 

 on average), and a strong development of these scales, which in the young 

 are often like those of the sprat in their sharpness. The number of the 

 vertebrae to the first haemal arch is great, mostly 25 and more. The head is 

 thick-set, high, with varyingly prominent foreshortening of the snout, and 

 weaker or stronger hrachijceplialism of the skull. Also characteristic are 

 the length of the back, and the relative shortness of the tail — they are 

 brachyuric. Lastly, the pronounced disposition to change the number of 

 the fin-rays in the ventral from 9 to 8, is distinctly characteristic. 



These characteristics vary with their dwelling-places ; from west to 

 east we get a gradual transition from highest number of vertebrae, of 

 keeled scales, ■ and strongest hracJiycephaJism, through decreasing 

 number of these, to a distinctly lower number of vertebra?, of keeled 

 scales, less breadth of skull, and smaller size. 



Coast-herring or Spring-spawners. 



These dwell in the coast waters of the whole North and Baltic Seas 

 to the innermost corner of the last. They all spawn in winter or spring 

 in the immediate proximity of the coast, and come very often 

 into narrow and brackish bays or river-mouths. Also, their body 

 characteristics are locally very different, even more different than between 

 those of the corresponding races of sea-herring. But they show certain 

 determinate characters in the composition of their race-characteristics 

 which differentiate them from the large group of sea- herring. Thus, the 

 small number of keeled scales (14'0 and fewer on average), and the weak 

 development of these scales. The number of vertebrae is, as a rule, not 

 smaller, but the number to the first haemal arch is relatively smaller. 

 The head is coarser, longer, with stronger development and elongation 

 of the snout, and mostly smaller skull-breadth — prominent dolichocep- 

 halism. The back is shorter ; head, and especially tail, long — in the 

 extreme forms clearly dolichuric. Lastly, the relatively seldom occur- 

 rence of 8 rays in the ventral fins. 



There are probably two groups of these, geographically : — 



(a) Those of the southern North Sea and western Baltic from 

 the Zuyder See to the Schley and other brackish bays of the 

 west Baltic. 



