963 



the first ineasiiriiif;' (i7 — 111 mm. in Icnulli nC hndy. 

 the second Kill — 201 mm., tlic third 2(i:;— 2 1(1 mm., 

 :iiiil the fdiii'tli (■(iiitaiiiing all llic lai-.Uf sj)eciiiu'iis, be- 



tween "242 and 34.5 mm. in lenojth. The first three 

 groups roughly answer, according to other calcu]ation.s 

 of mine, to the age-clas.ses of the first three years. 



After the second year tiiere thus ajipcars, on an 

 average, by no means a liackward removal, but a re- 

 gular advancement both of the dorsal and the ventral 

 fins. The normal development of the StrOmming, in 

 accordance with the rules for the Herring-type, termi- 

 nates in general at the end of the second year. And 

 it then shows, as we have seen above (the table on 

 p. 961, relation no. 8), at an average length of 203 

 nun., the same position of the venti-al fins as the Nor- 

 wegian Herring does at a length of 170 mm. As re- 

 gards the position of the dorsal fin (relation no. 5), the 

 same rule applies to the BohusMn Herrings. 



That a racial difference exists here, seems, in a 

 certain sense, undeniable. But this difference evidently 

 agrees, as Petersen" has stated, ^\ith the geographical 

 separation, and Winther's' observations go to show 

 that this separation is sometimes evanescent. "The 

 entire alteration in the Herring inhabiting the Sound", 

 he writes, "may be summed up as follows. The little 

 Baltic Herring (Kivik Herring, Xilhs.), which flocks 

 together at the beginning of autumn at the south end 

 of the Sound, advanced in 1867 right to the middle 

 of the strait, north of the Flint Channel, where it found 

 the great basin known as the "Hidkene" untenanted by 

 the Boffom Herring', which had already departed. x\fter 

 the spawning it followed the northward current out 

 of the Sound into the south of the Cattegat, whence 

 it returned year after year to its old spawning-place, 

 constantly increasing, under the favourable influence 

 of more congenial environments (the greater saltness 

 of the water?), in size and fecundit^^ It continued to 



"improve" in this manner until 1873, when its deve- 

 lopment liad ad\-anced so far that it could no longer 

 content itself within the conflned limits of the Sound, 

 but as it gradually attained the size and form of the 

 "Kiilhi Herrlufi", began to repair to the spawning- 

 places of the latter variety. Only few returned in 187.5 

 to the old spawning-places in the Sound, where a new 

 stock of Baltic Herring this year (1875) replaced the 

 old one in the Hulkene, north of the Flint Channel". 

 The Stromming can thus become Kulla Herring, an 

 alteration which, as we have seen, involves nothing 

 more than a higher degree of the typical development 

 of the species. But it by no means follows that all 

 Strommings become Herrings, nor does it seem pos.sible 

 for anyone to show tliat all young BohusUln Herrings, 

 loddsiUar as they are called, in course of time become 

 Ocean Herrings. 



That a particular stage of development under per- 

 manent circum.stances may become fixed as the termi- 

 nation of the development of a species under those 

 circumstances, is nothing unusual, and the characters 

 of Aouth, especiall}- in fishes that breed before they have 

 attained their full specific size and development, may 

 become hereditary and, under certain conditions, remain 

 unaltered. This is, no doubt, the explanation both of 

 the actual difference between the average StrOmming and 

 the average Herring, and of the fact that the young of 

 the so-called Spring Herring and Coast Herring differ 

 from the fry of the Autumn Herring and Ocean Her- 

 ring'. But the difference appears, to the best of our 

 knowledge, only in the averages and, probably, only 



" Kritik etc., Vid. Meddel. Naturli. For. Kbhvn, 1888, p. 1. 

 ' Nord. Tidskr. Fisk., Aarg. 3 (1876), p. 12. 



' The name given by the fishermen to the shoals of larger Herring in llie Sound. 



'' "II faut necessairement admettre la residence de ces poissons sur des fonds differents, ou la diversite de la grandeur et de la gros- 

 seur constitue autant de varietes ou de races qui se perpetuent par voie de generation '; Cm., Val., 1. c, XX, p. 49. 



