One day, a baby snail(蜗牛)found that he had to carry a hard and heavy shell(壳)at any time. He wanted to know why，so he went up to his mother and asked, "Why was I born with a shell and it grew(变得) so hard and heavy?" His mother said, "Because we have no bones(骨头). We can only move slowly, so we need a shell to protect(保护) us. "
The baby snail asked again, "The caterpillar(毛毛虫) has no bones, either, and she can't move quickly. Why can she live without a shell?" The mother snail answered, "That's because a caterpillar will become a butterfly(蝴蝶). She can fly high into the sky. The sky can protect her. "
The baby snail had one more question, "But the earthworm (蚯蚓) moves like us. He has no bones and he won't become a butterfly. Why doesn't he carry a hard and heavy shell?" His mother said, "He can dig(挖) a hole and hide(藏) in the ground, and then the earth(土地) can protect him. "
The baby snail then cried, "We are so poor! We have no protection from the sky or from the ground!" His mother smiled at him, "That's why we have a shell. My dear, if we don't have the shells, what will happen to us? The hot sun will dry out(干硬) our bodies and we'll have nowhere to sleep. Without a shell, maybe we'll die in the heavy rain. How bad it is! We don't depend on(依靠) the sky or the ground for protection. We should depend on ourselves. "
