muscles knotted beneath the smooth, brown skin of his arms and
shoulders, the veins stood out upon his temples from the force of his
exertions--a strand parted, another and another, and one hand was free.
Then from the jungle came a low guttural, and the ape-man became
suddenly a silent, rigid statue, with ears and nostrils straining to
span the black void where his eyesight could not reach.

Again came the uncanny sound from the thick verdure beyond the camp. A
sentry halted abruptly, straining his eyes into the gloom. The kinky
wool upon his head stiffened and raised. He called to his comrade in a
hoarse whisper.

"Did you hear it?" he asked.

The other came closer, trembling.

"Hear what?"

Again was the weird sound repeated, followed almost immediately by a
similar and answering sound from the camp. The sentries drew close
together, watching the black spot from which the voice seemed to come.

Trees overhung the boma at this point which was upon the opposite side
of the camp from them. They dared not approach. Their terror even
prevented them from arousing their fellows--they could only stand in
frozen fear and watch for the fearsome apparition they momentarily
expected to see leap from the jungle.

Nor had they long to wait. A dim, bulky form dropped lightly from the
branches of a tree into the camp. At sight of it one of the sentries
recovered command of his muscles and his voice. Screaming loudly to
awaken the sleeping camp, he leaped toward the flickering watch fire
and threw a mass of brush upon it.

The white officer and the black soldiers sprang from their blankets.
The flames leaped high upon the rejuvenated fire, lighting the entire
camp, and the awakened men shrank back in superstitious terror from the
sight that met their frightened and astonished vision.

A dozen huge and hairy forms loomed large beneath the trees at the far
side of the enclosure. The white giant, one hand freed, had struggled
to his knees and was calling to the frightful, nocturnal visitors in a
hideous medley of bestial gutturals, barkings and growlings.

Werper had managed to sit up. He, too, saw the savage faces of the
approaching anthropoids and scarcely knew whether to be relieved or
terror-stricken.

Growling, the great apes leaped forward toward Tarzan and Werper.
Chulk led them. The Belgian officer called to his men to fire upon the
intruders; but the Negroes held back, filled as they were with
superst