These curious creatures live in ponds and even in ditches as well as in rivers, and are very plentiful in all parts of the northern hemisphere. During the daytime, although they will sometimes bask at the surface in the warm sunshine, they generally lie buried in the mud at the bottom of the water, coming out soon after sunset to feed. And when the weather is damp, so that their gills are kept moist as they wriggle through the herbage, they will often leave the water and travel for some little distance overland. They frequently do this when they are traveling toward the sea. For it is a strange fact that, although they are fresh-water fishes, eels both begin and end their lives in the sea. In the first place, the eggs are laid in the sea--generally quite close to the mouth of a river. When the little elvers, as the young eels are called, hatch out, they make their way up the river in immense shoals. In the English river Severn, for instance, several tons of elvers are often caught in a single day; and about thirty million elvers go to the ton! After being pressed into cakes and fried, these little creatures are used for food; but they are so rich that one cannot eat very many at once. When they have traveled far enough up the river, most of the elvers which have escaped capture make their way to different streams and pools and ditches, and there remain until their growth is completed. They then begin to journey back to the sea, and when they reach it they lay eggs in their turn. After this, apparently, they die. In the rivers of South America a most wonderful eel is found which has the power of killing its victims by means of an electric shock, wherefore it is called the electric eel. The electricity is produced and stored up in two large organs inside the body, but how it is discharged nobody knows. If the fish is touched it merely gives a slight shudder. But the shock is so severe that quite a large fish can be killed by it, while a man's arm would be numbed for a moment right up to the shoulder. LAMPREYS The lamprey, which is found plentifully in many northern rivers, is very much like an eel in appearance. But it has no side fins, and instead of possessing jaws, it has a round mouth used for sucking, and resembling that of a leech; and on either side of its neck it has a row of seven round holes, through which water passes to the breathing-organs. Lampreys seem to spend the greater part of their lives in the sea, but always come up the rivers to spawn. They lay their eggs in a hollow in the bed of the stream, which they make by dragging away stone after stone till the hole is sufficiently deep. Very often a large number of lampreys combine for this purpose, and make quite a big hole, in which they all lay their eggs together. The length of the lamprey is generally from fifteen to eighteen inches, and its color is olive brown. CHAPTER XXXI SALT-WATER FISHES