April 2Z, 1881] 



NA TURE 



609 



to such vibrations. In a dark night, when the water is 

 phosphorescent or, as the fishermen say, there is plenty 

 of " raerefire,'' it is a curious spectacle to watch the effect 

 of sharply tapping the side of the boat as it passes over 

 a shoal. The herrin.^s scatter in all directions, leaving 

 streaks of light behind them, like shooting stars. 



The herring, like other fishes, breathes by means of the 

 gills — the essential part of which consists of the delicate, 

 highly-vascular filaments, which are set in a double row 

 on the outer faces of each of the gill arches. The venous 

 blood which returns from all parts of the body to be 

 collected in the heart, is pumped thence into the gills, 

 and there exchanges its excess of carbonic acid gas 

 for the gaseous oxygen which is dissolved in sea-rtater. 

 The freedom of pas- age of the water, and the great size 

 and delicacy of the gills, facilitate respiration when the 

 fish is in its native element ; but the same peculiarities 

 permitting of the rapid drying and coherence of the gills, 

 and thus bringing on speedy suffocation, render its tenure 

 of life, after removal from the water, as short as that of any 

 fish. It may be observed, in passing, that the wide clefts 

 behind the gill-covers of the herring have some practical 

 importance, as the fish, thru-ting its head through the 

 meshes of the drift-net, is caught behind them and cannot 

 e.\tricate itself. In the herring, the upper end of the last 

 gill cleft is not developed into a sac or pouch, such as we 

 shall find in some of its near neighbours. 



The only other organs of the herring, which need be 

 mentioned at present, are the milt and roe, found in the 

 male and female herring respectively. 



These are elongated organs attached beneath the air- 

 bladder, which lie, one on each side of the abdominal 

 cavity, and open behmd the vent by an aperture common 

 to the two. The spermatic fluid of the male is developed 

 in the milt and the eggs of the female in the roe. These 

 eggs, when fully formed, measure from one-sixteenth to 

 one-twenty-fifth of an inch in diameter ; and, as, in the 

 ripe female, the two roes or ovaries stretch from one end 

 of the abdominal cavity to the other, occupying all the 

 space left by the other organs, and distending the cavity, 

 the number of eggs which they contain must be very 

 great. Probably 10,000 is an under-estimate of the 

 number of ripe eggs shed in spawning by a moderate-sized 

 female herring. But I think it is safer than the 30 000 of 

 some estimates, which appear to me to be made in forget- 

 fulness of the very simple anatomical considerations that 

 the roe consists of an extensive vascular framework as 

 well as of eggs ; and, moreover, that a vast number of 

 the eggs which it contains remain immature, and are not 

 shed at the time of spawning. 



In this brief account of the structure of the herring I 

 have touched only on those points which are peculiarly 

 interesting, or which bear upon what I shall have to say 

 by and by. An exhaustive study of the fish from this 

 point of view alone would require a whole course of 

 lectures to itself. 



The herring is a member of a very large group of fishes 

 spread over ad parts of the world, and termed that of the 

 Clupcida, after C/iipea, the generic name of the herring 

 itself. Our herring, the Cliipea hareitpus, inhabits the White 

 Sea and perhaps some parts of the Arctic Ocean, the tem- 

 perate and colder parts of the Atlantic, the North Sea, 

 and the Baltic, and there is a very similar, if not identi- 

 cal, species in the North Pacific. But it is not known to 

 occur in the seas of southern Europe, nor in any part of 

 the intertropical ocean, nor in the southern hemisphere. 



There are four British fishes which so closely resemble 

 herrings, externally and internally, that, though prac- 

 tical men may not be in any danger of confounding 

 them, scientific zoologists have not always succeeded in 

 defining their differences. These are the Sprat, the AUice 

 and Twaite Shads, and the Pilchard. 



The sprat comes nearest ; indeed young herrings and 

 sprats have often been confounded together, and doubts 



have been thrown on the specific distinctness of the two. 

 Yet if a sprat and a young herring of the same size are 

 placed side by side, even their e.\ternal differences leave 

 no doubt of their distinctness. The sprat's lower jaw is 

 shorter ; the shields in the middle of the belly have a 

 sharper keel, whence the ventral edge is mere like a saw ; 

 and the ventral fin lies vertically under the front edge of 

 the dorsal fin, or even in front of it ; while in the herring, 

 though the position of the ventral fin varies a little, it lies 

 more or less behind the front margin of the dorsal fin. 

 The anal fin is of the same length as the dorsal, in the 

 herring, longer than the dorsal in the sprat. But the best 

 marks of distinction are the absence of vomerine teeth 

 in the sprat, and the smaller number of pyloric caeca, 

 which do not e.-cceed nine, their openings being disposed 

 in a single longitudinal series. 



Shads and pilchards have a common character by 

 which they are very easily distinguished from both sprat 

 and herring. There is a horizontal fold of scaly skin on 

 each side of the tail above and below the middle line. 

 Moreover they have no teeth in the inside of the mouth, 

 and their pyloric ca;ca are very numerous — a hundred or 

 more — their openings being disposed five or six in a row. 



The shads have a deep narrow notch in the middle line 

 of the upper jaw, which is absent in the pilchard. The 

 intestine of the shad is short and straight, like that of the 

 herring ; while that of the pilchard is long and folded 

 several times upon itself. 



Both of these fishes, again, possess a very curious struc- 

 ture, termed an accessory branchial organ, which is found 

 more highly developed in other fishes of the herring 

 family, and attains its greatest development in a fresh- 

 water fish, the HcteroCis, which inhabits the Nile. This 

 organ is very rudimentary in the shad (in which it was 

 discovered by Gegenbaur '), but it is much larger in the 

 pilchard, in which, so far as I know, it has not heretofore 

 been noticed. In Chanos and several other Clupeoid fishes 

 it becomes coiled upon itself, and in Heterotis the coiled 

 organ makes many turns. The organ is commonly supposed 

 to be respiratory in function ; but this is very doubtful. 



Herrings which have attained maturity and are dis- 

 tended by the greatly enlarged milt or roe are ready to 

 shed the contents of these organs or, as it is said to spawn. 

 In 1862, we found a great diversity of opinion prevailed as 

 to the time at which this operation takes place, and we 

 took a great deal of trouble to settle the question, with 

 the result which is thus staled in our Report : — 



" We have obtained a very large body of valuable evi- 

 dence on this subject, derived partly from the examination 

 of fishermen and of others conversant with the herring 

 fishery ; partly from the inspection of the accurate records 

 kept by the fishery officers at difierent stations, and partly 

 from other sources ; and our clear conclusion from all 

 this evidence is, that the herring spawns at two seasons 

 of the vear, in the spring and in the autumn. We 

 have hitherto met with no case of full or spawning her- 

 rings being found, in any locality, during what may be 

 termed the solstitial months, namely June and December ; 

 and it would appear that such herrings are never (or very 

 rarely) taken in May or the early part of July, in the latter 

 part of November, or the early part of January. But a 

 spring spawning certainly occurs in the latter part of 

 January, in February, in March, and in April ; and an 

 autumn spawning in' the latter part of July, in August, 

 September, October, and even as late as November. 

 Taking all parts of the British coast together, February 

 and ]\farch are the great months for the spring spawning, 

 and August and September for the autumn spawning. It 

 is not at all likely that the same fish spawn twice in the 

 year ; on the contrary, the spring and the autumn shoals 

 are probably perfectly distinct ; and if the herring, accord- 

 ing to the hypothesis advanced above, come to maturity 



' •■ Ueber das Kopfskelet von Alcfoceplialm rostratus" Morfhologuch/s 

 Jahrluch, Bd. iv., Suppl. 187S. 



