As he drifted on with the inharmonious throng, he noticed what seemed the objective of the war. This was the caves which lined the tunnel. Some were apparently rigid, others were mobile. A large red-and-gray animal was pushed into the mouth of one of the latter, and the walls instantly closed; then they opened, and the creature drifted out, limp and colorless, but alive; and with him came fragments of the wall, broken off by the pressure. This happened again and again, but the large creature was never quite killed—merely squeezed. The tentacled non-combatants and the large white fighters seemed to know the danger of these tunnel mouths, possibly from bitter experiences, for they avoided the walls; but the dog-faced invaders sought this death, and only fought on their way to the caves. Sometimes two, often four or more, would launch themselves together into a hollow, but to no avail; their united strength could not prevent the closing in of the mechanical maw, and they were crushed and flung out, to drift on with other debris. Soon the walls could not be seen for the pushing, jostling crowd, but everywhere the terrible, silent war went on until there came a time when fighting ceased; for each must look out for himself. They seemed to be in an immense cave, and the tide was broken into cross-currents rushing violently to the accompaniment of rhythmical thunder. They were shaken, jostled, pushed about and pushed together, hundreds of the smaller creatures dying from the pressure. Then there was a moment of comparative quiet, during which fighting was resumed, and there could be seen the swiftly flying walls of a large tunnel. Next they were rushed through a labyrinth of small caves with walls of curious, branching formation, sponge-like and intricate. It required energetic effort to prevent being caught in the meshes, and the large red-and-gray creatures were sadly torn and crushed, while the white ones fought their way through by main strength. Again the flying walls of a tunnel, again a mighty cave, and the cross-currents, and the rhythmical thunder, and now a wild charge down an immense tunnel, the wall of which surged outward and inward, in unison with the roaring of the thunder. The thunder died away in the distance, though the walls still surged—even those of a smaller tunnel which divided the current and received them. Down-stream the tunnel branched again and again, and with the lessening of the diameter was a lessening of the current’s velocity, until, in a maze of small, short passages, the invaders, content to fight and kill in the swifter tide, again attacked the caves.