But you can not always tell what is going to happen in this world. If, just then, a white rabbit had not scooted out of the bushes and run through the woods right in front of Zip, perhaps this part of the story would never have been written. It is certain that if there had been no rabbit to chase, Zip wouldn't have run as fast as he did. For he ran very fast. And, just as I told you, it was because the white rabbit popped out of the bushes right in front of the dog. "Bow-wow!" barked Zip, as he saw the bunny. "Bow-wow!" and that meant: "I guess I'd better chase you!" And that's what Zip did. Up he sprang from the grass, and after the white rabbit he ran. The dog started off so quickly that Russ and Laddie were almost thrown out of the cart. If they had not held to the sides of the box very hard they would have fallen out. As it was they were jerked and tossed about as Zip ran after the rabbit. "Oh, what's the matter?" asked Laddie, who had not seen the bunny. "Did a bee sting Zip?" This had happened once, and the dog had run around yelping and barking, no one knowing what was the matter with him for a while. "No, I don't believe it was a bee," answered Russ. "It was a rabbit. Whoa, Zip! Whoa!" called the little boy, pulling on the leather lines. But Zip did not stop. Very few dogs would, when once they had started to run after a rabbit. [Illustration: "BOW-WOW!" BARKED ZIP, AND ON HE RAN, FASTER AND FASTER. _Six Little Bunkers at Grandma Bell's_] "Bow-wow! Bow-wow!" barked Zip, and on he ran, faster and faster. He seemed to enjoy it very much. It was a good thing the woods were not of the roughest kind just at this place, for otherwise the dog-cart would have been smashed to pieces. As it was it bumped and swayed from side to side, and Laddie and Russ had all they could do to keep from bouncing out. "Whoa! Whoa!" called Russ, but Zip paid no attention. Nor did he care how much the little boy driver pulled on the lines. As Zip had no bit in his mouth to hurt him when it was pulled on hard, he was not going to stop. The leather muzzle around his nose did not hurt him as a bit would have done. I don't know just how far Zip would have run after the white rabbit, if something had not happened to put an end to the chase. The rabbit, probably getting tired of being run after, suddenly darted down inside a hole. This was his burrow, or underground house, and once down in that, the rabbit knew no dog could get him. So into his hole, as if he were going down cellar, went the bunny. And Zip, with a howl of disappointment, saw the rabbit disappear. The dog stopped at the outside edge of the hole, and barked as loudly as he could. Perhaps he thought he was giving the bunny an invitation to come up. But the bunny never answered. They don't bark, but they can make a funny little squeaking sound at times. This one didn't do even that. "He's gone, Zip! You can't get him," said Russ.