of the Fishery Board for Scotland. 



49 



and winter herring, with the result of satisfying myself of their identity 

 with these. 



The result of this examination of a large number of specimens has 

 been to show that a considerable individual variation exists among both 

 the sprats and herring. The position of the fins on the body and with 

 respect to each other, the length of the head as compared with total 

 length and other external characters as stated absolutely by some observers 

 (Parnell, Cuvier, Yarrell, Mitchell, &c), I have found to be inconstant ; 

 and although the variation is not very large, yet it is sufficiently consider- 

 able and in such variety as to make it impossible to lay down any fixed 

 rule on the subject. The measurements for determining these points 

 were all made on fresh fish, laid so that the fork or shortest ray of the 

 caudal fin was in a line with the tip of the closed lower jaw — the most 

 anterior point of both the sprat and herring. The position of the fins, 

 &c, being accurately marked off round the body, perpendiculars were 

 drawn from these points to the centre line, and the measurements taken 

 on it, this affording also at a glance a view of the relative position of fins, 

 &c. I believe this method gives more accurate results than is got by 

 measuring the actual distance diagonally from fin, &c, to mandible, since 

 the slightest curvature upwards or downwards on the dead fish causes a 

 change of these dimensions. 



The variations which I have referred to, occurred not only between 

 specimens taken from the separate samples which I received at various 

 periods during the winter, but also among fish in the same sample, and 

 therefore caught at the same time and place, rendering it improbable 

 that these differences were owing to the presence of specific varieties 

 among the sprats or young herring. 



External Characters. — It is difficult to describe in words the 

 difference which exists in the general shape of the body between a sprat 

 and a young herring ; but a short experience in observing them generally 

 enables one at a glance to distinguish the one from the other. 



The general shape of the sprat is more graceful than that of the small 

 herring, which has not yet reached the elegant form of the adult. The 

 body increases in depth from the head backwards for nearly one-third of 

 the total length (about 40 mm. in a sprat 110 mm. long), this increase in 

 depth being caused partly by the arching of the back, and partly by the 

 curved outline of the belly, the latter, in a typical fresh specimen, being 

 nearly equal in amount to the former. Cuvier and Valenciennes give the 

 depth as equalling the length of head, that being one-fifth of the total 

 length. The head varies so much in its relative length that this is not 

 altogether accurate ; but in several sprats which I selected on account of 

 their large size the greatest depth was one-fifth of the length, including 

 caudal rays. In the young herring, however, the greatest depth is less 

 and nearer the head (occurring about 32 mm. from the anterior end in 

 a fish of 110 mm. long), and the downward curve of the belly is much 

 less. The young herring consequently has a less graceful outline, and 

 appears to taper almost immediately from the head backwards (Plate III. 

 figs. 1, 2). The sprat also is slightly thicker in the body than the young 

 herring. 



This thinner and more elongated appearance of the young herring as 

 compared with an equal-sized sprat is still further increased by the dorsal 

 surface of the head of the young herring being almost always proportion- 

 ally slightly longer than the sprat's, but I believe this only applies to the 

 comparison between sprats and young herring, for I find that several full- 

 grown herring do not show a proportionally longer head than the sprat. 

 Just as the head of the young herring is longer than the sprat's, so its 

 operculum extends rather further back, and its most backward point is at 



H 



