82 



Appendices to Fourth Annual Report 



Position of Dorsal Fin. 



The position of the dorsal fin has probably had more attention bestowed 

 on it than any other character, with the purpose of discovering or demon- 

 strating by its means some method of distinguishing the varieties, if there 

 be such, of herrings from each other, as well as from the other members 

 of the genus Clupea. Commonly the variation of this characteristic has 

 been determined by the position of the first ray of the fin, the few excep- 

 tions being those where the fin generally is referred to as a whole, no special 

 point in it being particularised. 



The examination of a very few herrings discloses the fact that not only 

 does the dorsal fin vary in position, but it also varies in basal length ; 

 consequently in limiting our inquiry to the position of the dorsal fin as 

 expressed by the position of its first ray, we are mixing up two distinct 

 characters, and the result is doubt as to the actual position of the fin. On 

 this account my examination into the position of the dorsal fin has been 

 made with regard to the centre of the fin — a separate examination being 

 then made of the various lengths presented by the fin relatively to the 

 body length. I have, however, also ascertained the variation in position 

 of the first ray, and shall have to make some reference to it also. 



In this investigation the position of the centre of the dorsal fin has been 

 found with reference to two different measures of length, viz., its position 

 relatively to the body alone {i.e., the body length minus the head and tail 

 lengths), and, secondly, to the total length of the fish from tip of closed 

 lower jaw to tip of caudal fin. 



The variation in position of the fin centre relatively to the body length 

 runs from -465 to -540 in the examples of winter fish. Among the summer 

 herrings the extent of variation is rather less, being from "474 to -540. A 

 similar distinction, though small, has already been noted in respect to the 

 length of head. 



It is rather difficult to reconcile the varied results which the position of 

 the dorsal fin gives us on winter and summer fish, mature and immature, 

 and relative to the length of body only, and to the total length. Table IX. 

 shows the range of variation divided into five classes, and a study of these 

 shows that a much larger percentage of the summer herrings had the centre 

 of the dorsal fin placed relatively far back than was the case with the 

 winter fish. 



TABLE IX. showing the percentage of Herrings arranged according to position 

 of centre of dorsal fin relatively to length of body. 



Kange of Variation. 



•465 



to 

 •480 



•481 

 to 

 •495 



•496 

 to 

 •510 



•511 

 to 

 •525 



•526 

 to 

 •540 



















Mature \ 



Winter 



11-5 



34-5 



30-2 



18-6 



5^2 



Herrings 



Summer 



2-7 



15-8 



32-6 



41-8 



7-1 



Immature 



Winter 



32-6 



42-8 



24-6 







Herrings 



Summer 



29-6 



37-0 



29-6 



3^7 





