The largest and fiercest of all the members of the dolphin family is undoubtedly the grampus, which is also known as the killer, or killer-whale. It often reaches a length of twenty feet, or even more, and is so savage and voracious that it has sometimes been called the wolf of the sea. One of these animals was once found floating on the surface of the sea, choked by a seal which it had attempted to swallow; and when its body was opened fourteen other seals and thirteen porpoises were taken from its stomach. Three or four killers will often combine in an attack upon a large whale, leaping upon it again and again, and striking terrific blows upon its body with their tails, hanging upon its lips like so many bulldogs, biting and tearing its flesh, and often actually killing it. The whale seems terrified by the onslaught of the ferocious creatures, and sometimes scarcely attempts to resist them, apparently knowing quite well that they are sure to be victorious in the end. The grampus is most plentiful in the northern seas, but is found now and then in almost all parts of the ocean. It occasionally visits the British shores. Once a living specimen was exhibited in the Brighton Aquarium, and did very well for some little time. But one day it got its snout jammed in the rock-work at the bottom of its tank, so that it could not rise to the surface to spout. And when the keeper discovered what had happened to it the poor creature was dead. THE BLACKFISH Almost as large as the grampus, but not nearly so savage, is the blackfish, which is so called on account of its color, for it is not a fish, being a member of the dolphin family. It is found in great shoals, generally consisting of two or three hundred animals, and often of a great many more, which are always under the guidance of a single leader. Wherever he goes they will always follow, and they are such stupid creatures that if he swims into shallow water and casts himself ashore, they will all swim after him and fling themselves on the beach also. In Iceland, and also in the Faroe Islands, large numbers of them are often killed, the fishermen arranging their boats in a semicircle between the shoal and the deep sea, and then driving them forward till they strand themselves upon the shore in their efforts to escape. Large herds have also been driven ashore in the Orkneys and the Shetlands. On the east coast of North America the blackfish is one of the most abundant cetaceans. Off Cape Cod more than a hundred blackfish have been seen in one school, and they are eagerly hunted for the sake of the soft oil yielded by their fat. DOLPHINS There are two groups of dolphins, the first of which contains three animals that live in rivers, and therefore are generally called fresh-water dolphins.