THE HERRING. 439 



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 behind 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 dis- 

 tending 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 forgetfulness of the very simple anatomical con- 

 siderations 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 all parts of the world, and termed that of the Clupeidm, after 

 Clupea, the generic name of the herring itself. Our herring, the 

 Cliqjea hareiigus, inhabits the White Sea, and perhaps some parts of 

 the Arctic Ocean, the temperate and colder parts of the Atlantic, the 

 North Sea, and the Baltic, and there is a very similar, if not identical, 

 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 practical men may not be in 

 any danger of confounding them, scientific zoologists have not always 

 succeeded in defining their differences. These are the Sj^rat, the Allice 

 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 external 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 tho 

 ventral edge is more like a saw ; and the ventral fin lies vertically 



