On the back of most of the Cetacea there is another fin, which is merely a part of the skin. They have no hind fins, and their great front fins or arms are of little use for locomotion through the water, but serve to balance their movements. The skin of the different members of the Whale family is generally quite hairless, which very rarely happens in the case of other Mammalia. The largest of other animals are small when compared with many of the Cetacea. These great creatures swim quite rapidly, however. Because of the air contained in their chest, and the great quantity of grease with which their tissues are charged, and the great strength of their tail in pushing them forward, they move easily through the waves, looking for the Fish, Molluscs and Crustacea, which they eat in enormous quantities. The Whale family is first divided into two classes, the Blowing Cetacea, and the Herbiverous Cetacea. The Herbiverous class includes the Manatees and the Duyongs who live on the weedy, shallow shores around the islands and mouths of rivers, and feed on the sea-weed. The class of Blowing Cetacea includes the Whale proper, the Rorquals and the great Cachalot or Sperm Whale, in which the head constitutes in itself one-third, or even one-half of the total length of the creature, the Whalebone Whale; and a second division containing the Dolphin, the Porpoise, Narwhal, etc., in which the head is in the usual proportion to the body. THE WHALE, AND ITS ENEMIES. We hear surprising stories of the Whales of past ages which measured from one or two hundred feet in length; and from the skeletons that have been discovered, it is found that even if they did not reach this great length, it is probably true, as Goldsmith claims, that they were very much larger in the past than now. It is the same as with the quadrupeds, the huge Mastodons, etc., from the skeletons that have been dug up from time to time it is evident that there must have been terrestrial animals twice as large as the Elephant, but these, being rivals with mankind for the large territory required for their existence, must have been destroyed in the contest. And in the sea, as well as upon land, Man has destroyed the larger tribes of animals.