The reason why these fishes take their long leaps through the air appears to be that they are much persecuted by other fishes, bigger and stronger than themselves, and that they know quite well that they will be overtaken if they remain in the water. They do not usually rise to a height of more than a few feet above the surface, and the greatest distance to which they can travel without falling back into the water seems to be about two hundred yards. Whether they can alter the direction of their course while they are in the air is uncertain. Some observers say that they can, while others declare that they cannot. But it is possible that they may sometimes do so by just touching the crest of a wave with their tails. Flying fishes are found in all the warmer parts of the sea, and are very common in the Mediterranean and the West Indies. THE HERRING Like the mackerel, the herring is one of those fishes which live in vast shoals and are of great value as a cheap and nutritious food. These shoals consist of millions upon millions of fishes, and when they are swimming near the surface of the sea their presence can generally be detected by the numbers of sea-birds which follow them and devour them in countless thousands. Whales, too, often follow the shoal for days together, and sharks and many other big fishes do the same. Yet nothing seems to lessen their numbers. These shoals generally appear in the same parts of the sea, year after year, at the same season. But sometimes the herring will desert their favorite haunts without any apparent cause. During spring and early summer they remain in deep water; but in June and July they come in nearer the coast in order to spawn. GOBIES There are still several very curious and interesting fishes about which we should like to tell you; and among these are the gobies. Many different kinds of these odd little creatures are found in different parts of the world other than North America; but perhaps the best known of all is the black goby, which is very common off British coasts. You can often catch it by fishing with a small net in the pools which are left among the rocks as the tide goes out. And if you look into these pools from above, you may often see it clinging to the rocks round the margin. It does this by means of the fins on the lower part of its body, which are made in such a manner that when they are placed side by side together they form a kind of sucker. And if you keep the fish in an aquarium, it has an odd way of suddenly darting at the side of the tank, clinging to it with its fins, and staring at you through the glass.