"Well," said his sister, "I"ve been looking at the fishes in your picture book, and I find that they all have small, sharp, pointed teeth in both jaws. There are a great many of them, but they don"t seem to be meant either for tearing or chewing. I should like to know what food the fish feeds upon, and how it feeds.""Then suppose we have a closer look at the teeth," said Fred. "The teeth are, as you say, simply little sharp spikes, but they allpoint backwards towards the throat. Where have we seen teeth like this before?""The snakes have teeth just like this," said Norah. "They feed upon animals, and swallow their prey whole.""Fishes," said Fred, "feed on one another, and they too swallow their prey whole without waiting to chew it. They are very fierce and greedy, and from the largest to the smallest, prey upon and devour each other. They hunt their prey through the water as the lion, tiger, and other fierce flesh- eaters hunt theirs on the land.""This explains," said Willie, "why they are made for easy and rapid movement through the water. At one time they are the hunters, at another they are the hunted prey.""The backward pointed teeth are meant to seize the prey," said Fred. "They must be strong enough also to hold the struggling, slippery victim fast, while the work of swallowing goes on.
