THE HERRING. 435 



Like most fishes, the herring is propelled chiefly by the sculling 

 action of the tail-fin, the rest serving chiefly to preserve the balance 

 of the body, and to keep it from turning over, as it would do if left 

 to itself, the back being the heaviest part of the fish. 



The mouth of the herring is not very large, the gape extending 

 back only to beneath the middle of the eye, and the teeth on the 

 upper and lower jaws are so small as to be hardly visible. Moreover, 

 when a live herring opens its mouth, or when the lower jaw of a dead 

 herring is depressed artificially, the upper jaw, instead of remaining 

 fixed and stationary, travels downward and forward in such a manner 

 as to guard the sides of the gape. This movement is the result of a 

 curious mechanical arrangement by which the lower jaw pulls upon 

 the upper, and I suspect that it is useful in guarding the sides of the 

 gape when the fish gulps the small living prey upon which it feeds. 



The only conspicuous teeth, and they are very small, are disposed 

 in an elongated patch upon the tongue, and in another such patch, 

 opposite to these, on the fore part of the roof of the mouth. The 

 latter are attached to a bone called the vomer, and are hence termed 

 vomerine teeth. But, if the mouth of a herring is opened widely, 

 there will be seen, on each side, a great number of fine, long, bristle- 

 like processes, the pointed ends of which project forward. These are 

 what are tenned the gill-rakers, inasmuch as they are fixed, like the 

 teeth of a rake, to the inner sides of those arches of bone on the outer 

 sides of w^hich the gills are fixed. The sides of the throat of a her- 

 ring, in fact, are, as it were, cut by four deep and wide clefts, which 

 are separated by these gill arches, and the water which the fish con- 

 stantly gulps in by the mouth flows through these clefts, over the gills 

 and out beneath the gill-covers, aerating the blood, and thus effecting 

 respiration, as it goes. But, since it would be highly inconvenient, 

 and indeed injurious, were the food to slip out in the same way, these 

 gill-rakers play the part of a fine sieve, which lets the water strain off, 

 while it keeps the food in. The gill-rakers of the front arches are 

 much longer than those of the hinder arches, and, as each is stiffened 

 by a thread of bone developed in its interior, while, at the same time, 

 its sides are beset with fine sharp teeth, like thorns on a brier, I sus- 

 pect that they play some part in crushing the life out of the small 

 animals on which the herrings prey. 



Between these arches there is, in the middle line, an opening which 

 leads into the gullet. This passes back into a -curious conical sac which 

 is commonly termed the stomach, but which has more the character 

 of a crop. Coming off from the under side of the sac and commu- 

 nicating with it by a narrow opening, there is an elogated tubular 

 organ, the walls of which are so thick and muscular that it might 

 almost be compared to a gizzard. It is directed forward, and opens 

 by a narrow prominent aperture into the intestine, which runs straight 

 back to the vent. Attached to the commencement of the intestine 



