But Bolo and Fisher obeyed. Bolo had drawn a little away from the rest of the hunters. He had swung his stout bow down from his shoulder and carefully fitted an arrow to the taut string. No one noticed the sharp twang as the arrow left the bowstring, but all saw one of the mammoths rear suddenly with pain and plunge into the midst of the herd. Startled at this sudden onslaught, the herd pressed a little closer to the edge of the cliff, and then--