Imagine, if you can, a Shark about fifteen feet long and weighing a ton or so. Now suppose the top jaw of this monster to be drawn out into a hard, flat blade six feet in length. Then suppose there are sharp ivory teeth, one inch apart, fixed on each side the blade, and you have an idea of the Saw-fish. This strange Shark is said to be as strong as it is fierce. It kills its prey by tearing them open with side blows from its sharp, two-edged saw. Its big mouth is fitted with a great many rows of needle-like teeth. The Sword-fish wears a different weapon--a lance instead of a saw. He is not a Shark, but a cousin of the beautiful Mackerel. This warrior of the deep is more dreaded than the Saw-fish, and braver than any Shark. His speed in the water is marvellous; it makes him safe from attack. He carries in front of him a terrible weapon, and all sea-creatures hasten from his path as fast as they can. You may have seen the Sword-fish in a museum. There is a fine one in the London Natural History Museum, where there is also a "sword" from one of these fish, driven eighteen inches into the solid oak of a ship. The Sword-fish never thinks twice about attacking, no matter if his enemy is ten or twenty times as large as himself. He sees a Whale, and, like a flash, hurls himself at it, stabbing his sword as deep as it will go into the Whale's side. With a twist of his body the sword is wrenched free, only to be driven savagely in again. EXERCISES 1. Mention three ways in which sea-creatures try to escape their enemies. 2. How do the Sting-fish and Sting Ray defend themselves? 3. What is the Saw-fish like? 4. How does the Sword-fish attack its prey? LESSON IX THE FISH OF OUR ROCK-POOLS The pools left by the falling tide have many an interesting thing to show us. There are living creatures in plenty, besides the pretty weeds, shells, and other objects. Shrimps, Prawns and Crabs abound in the rock-pools and shallows, with anemones and shellfish of all kinds. In the rock-pools we shall also find the interesting little fish whose story we glance at in this lesson. Of course there are baby flat-fish, and large fish too, along the shore. But these are only visitors. The real rock-pool fish are those which live their lives there. Some of them are tiny things, two or three inches long. With quick movements like Shrimps they dart away as you approach. They have a way of hiding under weeds and rocks, being very clever at "hide-and-seek," and knowing all the dodges. But, by using a net, you will soon capture a few of them. Then you can put them in a small pool and examine them; or even keep them in an aquarium, giving them clean sea-water, seaweed, and the small shrimps on which they feed. [Illustration: PIPE-FISH AND FLUTE MOUTH]