“WHAT do you know about that?” muttered Joe Lewis, staring at the animal. “A white pigmy elephant! Wouldn’t our dads be tickled if they could see it?”

“That’s an idea,” said Bob quickly. “Why can’t we shoot it for them?”

Joe laughed.

“Impossible,” he said. “Why, these revolver cartridges wouldn’t even stop it, let alone kill it. Not much chance of doing that. Then too, we want to find our party.”

But Bob persisted.

“I tell you we can get that elephant some way,” he went on. “As for finding the safari, well—I don’t believe a few minutes’ delay would make much difference. And I feel sure we’ll find them before long. But right now let’s get that elephant.”

“But how?” demanded the other.

The animal was about twenty yards away and seemed not to notice the human invaders. And the wind was blowing away from it, so that it could not get their scent.

As silently as they could the boys crept along through the tall grass, keeping their revolvers in readiness. Bob led the way, confident that he could manage to get an effective shot.

When within five yards of it, the young hunters stopped and waited. The little elephant had its back toward them, making it impossible to fire.

Then it turned and faced them, perhaps sensing danger.

“Now!” said Bob, and together the youths fired, aiming at the eyes.

Without an outcry the elephant fell, writhed about for a second, and then was still.

“Yay!” cried Bob. “Killed it instantly. Both of those bullets found their way to the brain. And,” facing his chum, “you said it couldn’t be done.”

“I’m sorry,” grinned Joe. “I guess there isn’t anything we can’t do, eh, Bob?”

The youths hardly knew what to do with the carcass. They could not take the time to skin it, and yet they knew hyenas and vultures would soon appear if it were left where it was.

Finally they decided to do a quick job of skinning it, although perhaps they could not perform the task as well as it should be done.

Using their hunting knives, they hastily ripped off the white hide, which they were finally able to move several yards from the carcass. Then they gathered thorn bushes and surrounded it by an impenetrable boma. Over the hide as well as around it they placed several thicknesses of thorns and brambles.

“Maybe that’ll keep the vultures and hyenas away,” said Joe, as he turned to leave. “Now, if we can just find the safari.”

For a half hour the boys trudged on, their hopes slowly becoming lessened. At frequent intervals they fired their revolvers, stopping shortly after to listen.

On one occasion Bob thought he heard a shout but was not sure. Again he fired, and again he listened.

Sure enough, a faint cry was breaking the vast stillness. It was repeated again and again, and then came the sound of a rifle shot.

“It’s our party!” cried Joe happily. “They’ve heard us.”

“Come,” said Bob, setting off at a rapid pace. “Let’s hurry.”

Five minutes later the chums broke through the foliage and faced none other than Mr. Lewis and Mr. Holton.

“Boys!” cried Bob’s father, his joy beyond words. “We’ve found you at last!”

Mr. Lewis was equally affected.

“We were afraid something happened to you,” he said, patting them affectionately. “We didn’t see how you could possibly go through this forest unharmed. Especially with all the strange things here.”

“Just what do you mean by that?” demanded Bob, wondering if the naturalists had also seen or heard unexplainable phenomena.

“What I said,” returned Mr. Lewis, his face grave. “Howard and I heard all kinds of mysterious noises from the depths of the forest. We haven’t any idea what they were. And there’s something else that we haven’t been able to explain.”

“What was that?” inquired Joe, thoroughly interested.

“Last night we saw a strange phosphorescence very near our camp,” his father resumed. “It shone quite brilliantly, and we weren’t able to tell what caused it. We played our flashlights on it, but could make out nothing. Some trick of nature, I suppose.”

“You weren’t the only ones to see mysterious things,” said Joe, and then told of the peculiar footprint and of the long spear that had so nearly ended his life.

When he had finished, the naturalists looked grave.

“You boys certainly had a thrilling experience,” Mr. Holton said. “Of course,” he went on, “there’s an explanation to everything that has happened. Whether we’ll be able to delve into it we have yet to see.”

“But there’s something else that will interest you,” put in Bob. “Joe and I shot a white pigmy elephant.”

“What? Not fooling us, are you?”

“Come, and we’ll show you,” said Bob, and led the way through the forest.

When they finally reached the spot, they found the boma just as they had built it. The carcass, however, had been torn to pieces by vultures and hyenas.

The youths removed the thorn and bramble bushes from the enclosure and then turned to get the elephant skin.

To their great surprise, it was gone!

“Of all things!” exclaimed Bob, rubbing his forehead in perplexity. “That skin has disappeared as if by magic!”

Joe glanced at his chum, then at the boma. He looked around the other side, but the white skin was nowhere in sight. Finally he straightened up, a look of supreme bewilderment on his face.

“Gone sure enough,” he said.

“Are you certain you put it there?” inquired Mr. Holton.

“Certainly we did,” Bob assured him. “What I can’t understand is why the boma wasn’t torn to pieces. If some wild animal——”

“Maybe it wasn’t a wild animal,” put in Joe.

“Then—what could it have been?”

“Beyond me.” Joe had no suggestion of an idea.

The two naturalists took up where their sons had left off and searched the vicinity of the boma. But they had to admit defeat.

“Another mystery to add to our already long list,” commented Mr. Lewis. “It seems that there is no end to them.”

“Perhaps,” suggested Mr. Holton suddenly, “natives got that skin. They could have been watching the boys place it there. And they could have covered up the thorn enclosure just as it was.”

“Possibly,” came from Mr. Lewis. “But now let’s get back to camp. We’ll have some busy days before us.”

Noko and the other natives gave Bob and Joe a royal welcome on seeing them alive and well. For none knew better than the blacks the dangers of a tropical hurricane.

The two naturalists had already collected a large number of specimens. During the days that followed they added more, many of which were unknown.

Bob and Joe did their share of collecting, bringing down not a few curious wild creatures. They also spent their time in taking motion pictures of the wild country about them.

On one occasion they left camp on an all-day trip, taking two of the bearers with them. They hoped to photograph unusual scenes and perhaps solve some of the mysteries that so bewildered them.

They were following a strictly compassed course, so as to take no chance of becoming lost from the others. Their previous experience had taught them to have even more respect for the great African forest.

When the sun was overhead, they sat in the shade of a great raffia palm, to escape the heat and partake of lunch.

Joe gazed off rather absently through the trees. Suddenly his jaw dropped.

“What’s the matter?” asked Bob in surprise. “What do you see?”

“Look away over there,” Joe pointed out. “See that high ant hill?”

“Why—yes. And look. There’s a hut on top of it. Who do you suppose lives there?”

“Let’s go and see.”

Together the young explorers trekked through the forest until they came to the ant hill. The latter was all of thirty feet in height, and built firmly on its summit was a small thatched hut.

“Boy, this is a mystery,” murmured Bob. “Shall we go up and investigate?”

“I’m willing.”

There was a crude ladder running up the side of the ant hill. Up this the chums made their way. They feared at every moment that the ladder might collapse with their weight.

“Keep a hand on your revolver,” warned Bob. “There’s no telling what may be in that hut. Maybe some savage is asleep there, for all we know.”

When halfway to the top, they heard a shout from below.

Looking down they saw a man—a white man!