Mr. Damon came to a pause in the compartment from which the diving chamber gave access to the ocean outside. Tom, standing before the sliding steel door, had summoned to him several of his men and was rapidly giving them directions.

"What are you going to do, Tom Swift?" asked the eccentric man.

"I'm going out there to save Ned!" was the quick answer. "He's in the grip of some strange monster of the sea. What it is I don't know, but I'm going to find out. Koku, you come with me!"

"Yes, Master, me come!" said the giant simply, as if Tom had told him to go for a pail of water instead of risking his life.

"Barnes, the electric gun!" cried the young inventor to one of his helpers, while others were getting out the diving suits.

"The electric gun!" exclaimed the man. "Do you mean the small one?"

"No, the largest. The improved one."

"Right, sir! Here you are!"

"Do you mean to say you are going out there, where that monster is, and attack it with a gun?" asked Mr. Hardley.

"That's what I'm going to do!" answered Tom, as he began to put on the suit of steel and rubber, an example followed by Koku.

"But you may be attacked by the monster! You may be killed! You are risking your life!" cried the gold seeker.

"I know it." Tom spoke simply. "Ned would do the same for me!"

"But hold on!" cried Mr. Hardley. "If you are killed there will be no one to navigate this boat to the place of the wreck! You can't desert this way!"

Tom gave the man one look of contempt. "You need have, no fears," he said. "This submarine is under international maritime laws. If I die, Captain Nelson, the next in command, takes charge, and the original orders will be carried out. If it is possible to get the gold for you it will be done. Now let me alone. I've got work to do!"

"Bless my apple cart, Tom, that's the way to talk!" exclaimed Mr. Damon, and he, too, for the first time, seemed ready to break with Hardley. "If I were a bit younger I'd go out with you myself and help save Ned."

"Koku and I can do it--if he's still alive!" murmured the young inventor. "Lively now, boys! Is that gun ready?"

"Yes, and doubly charged," was the answer. "Good! I may need it. Koku, take a gun also!"

"Me take axe, Master," replied the giant.

"Well, perhaps that will be better," Tom agreed. "If two of us get to shooting under the water we may hit one another. Quick, now! The helmets. And, Nash, you work the big searchlight!"

"Aye, aye, sir!" answered the sailor.

The helmets were now put on, and any further orders Tom had to give must come through the telephone, and it was by that same medium that he must listen to the talk of his friends. It was possible for the divers to talk and listen to one another while in the water by means of these peculiarly constructed telephones.

"All ready, Koku?" asked Tom.

"All ready, Master," answered the giant, as he grasped his keen axe.

The inner door of the diving chamber was now opened, and, the water having been pumped out of the chamber since Ned and the sailor had emerged, it was ready for Tom and Koku. They entered, the door was closed, and presently they felt the pressure of water all about them, the sea being admitted through valves in the outer door.

While this was going on Mr. Damon, the gold-seeker, and some of the crew and officers went into the forward chamber to observe the undersea fight against the monster that had attacked Ned.

Suddenly the waters glowed with a greatly increased light, and in this illumination it was seen that the monster, whatever it was, had almost completely enveloped Tom's chum with its five arms.

"What makes it possible to see better?" asked Mr. Damon.

"I've turned on the big searchlight," was the answer. "Mr. Swift had it installed at the last moment. It's the same kind he invented and gave to the government, but he retained the right to use it himself."

"It's a good thing he did!" exclaimed the eccentric man. "Now he can see what he's doing! Poor Ned! I'm afraid he's done for!"

"Look!" exclaimed one of the crew. "Norton, the sailor who went out with Mr. Newton, is trying to kill the monster with his spear!"

This was so. Ned's companion, armed with a lone pole to which he had lashed a knife, was stabbing and jabbing at the black form which almost completely hid Ned from sight. But the efforts of the sailor seemed to produce little effect.

"What in the world can it be?" asked Mr. Damon. "Tom says it isn't an octopus, and it can't be, unless it has lost three of its arms. But what sort of monster is it?"

No one answered him. The powerful searchlight continued to glow, and in the gleam Ned could be seen trying to break away from the grip of the Atlantic beast. But his efforts were unavailing. It was as if he was enveloped in a sort of sack, made in segments, so that they opened and closed over his head. About all that could be seen of him was his feet, encased in the heavy lead-laden boots. The form of the other sailor, who had gone out of the submarine with him, could be seen moving here and there, stabbing at the huge creature.

"Here comes Tom!" suddenly exclaimed Mr. Damon, and the young inventor, followed by the giant Koku, came into view. They had emerged from the diving chamber, walked around the submarine as it rested on the ocean floor, and were now advancing to the rescue. Tom carried his electric rifle, and Koku an axe.

So desperately was Norton engaged in trying to kill the sea beast that had attacked Ned, that for the moment he was unaware of the approach of Tom and Koku. Then, as a swirl of the water apprised him of this, he turned and, seeing them, hastened toward them.

"What is it?" Tom asked through the telephone, this information being given to the watchers in the submarine later, as all they could gather then was by what they saw. "What sort of monster is it?"

"A giant starfish!" answered Norton, speaking into his mouthpiece and the water serving as a transmitting medium instead of wires. "I never knew they grew so big! This one has its five arms all around Mr. Newton!"

"A starfish!" murmured Tom. This accounted for it, and, as he looked at the monster from closer quarters, he saw that Norton had spoken the truth.

Small starfish, or even large ones, two feet or more in diameter, may be seen at the seashore almost any time. Nearly always the specimens cast up on the beach are in extended form, either limp, or dead and dried. In almost every instance they are spread out just as their name indicates, in the conventional form of a star.

But a starfish alive, and at its business of eating oysters or other shell animals in the sea, is not at all this shape. Instead, it assumes the form of a sack, spreading its five radiating arms around the object of its meal. It then proceeds to suck the oyster out of its shell, and so powerful a suction organ has the starfish that he can pull an oyster through its shell, by forcing the bivalve to open.

And it was a gigantic starfish, a hundred times as large as any Tom had ever seen, that had Ned in its grip. The creature had doubtless taken the diver for a new kind of oyster, and was trying to open it. An octopus has suckers on the inner sides of its eight arms. A starfish has little feelers, or "fingers," arranged parallel rows on the inner side of its armsÄthousands of little feelers, and these exert a sort of sucking action.

The gigantic starfish had attacked Ned from above, settling down on him so that the head of the diver was at the middle of the creature's body, the five arms, dropping over Ned in a sort of living canopy. And the arms held tightly.

"Come on, Koku, and you, too, Norton!" called Tom through his headpiece telephone. "We'll all attack it at once. I'll fire, and then you begin to hack it. The electric charge ought to stun it, if it doesn't kill the beast!"

Tom's new electric gun, unlike one kind he had first invented, did not fire an electrically charged bullet. Instead it sent a powerful charge of electricity, like a flash of lightning, in a straight line toward the object aimed at. And the current was powerful enough to kill an elephant.

Bracing his feet on the white sand, which gleamed and sparkled in the glare of the searchlight, Tom aimed at the gigantic starfish which had enveloped Ned. Standing on either side of him, ready to rush in and attack with axe and lance, were Koku and Norton.

For an instant Tom hesitated. He was wondering whether the powerful electric charge might not penetrate the body of the starfish and kill his chum.

"But the rubber suit ought to insulate and protect him," mused the young inventor. "Here goes!"

Taking quick aim, Tom pulled the switch, and the deadly charge shot out of the rifle toward the sea monster.