ma!" he muttered; but he did not stop. Numa might not be
at home--he would investigate. The entrance was so low that the
ape-man was compelled to drop to all fours before he could poke
his head within the aperture; but first he looked, listened, and
sniffed in each direction at his rear--he would not be taken by
surprise from that quarter.

His first glance within the cave revealed a narrow tunnel with
daylight at its farther end. The interior of the tunnel was not so
dark but that the ape-man could readily see that it was untenanted
at present. Advancing cautiously he crawled toward the opposite
end imbued with a full realization of what it would mean if Numa
should suddenly enter the tunnel in front of him; but Numa did not
appear and the ape-man emerged at length into the open and stood
erect, finding himself in a rocky cleft whose precipitous walls
rose almost sheer on every hand, the tunnel from the gorge passing
through the cliff and forming a passageway from the outer world
into a large pocket or gulch entirely enclosed by steep walls of
rock. Except for the small passageway from the gorge, there was no
other entrance to the gulch which was some hundred feet in length
and about fifty in width and appeared to have been worn from the
rocky cliff by the falling of water during long ages. A tiny stream
from Kilimanjaro's eternal snow cap still trickled over the edge
of the rocky wall at the upper end of the gulch, forming a little
pool at the bottom of the cliff from which a small rivulet wound
downward to the tunnel through which it passed to the gorge beyond.
A single great tree flourished near the center of the gulch, while
tufts of wiry grass were scattered here and there among the rocks
of the gravelly floor.

The bones of many large animals lay about and among them were
several human skulls. Tarzan raised his eyebrows. "A man-eater,"
he murmured, "and from appearances he has held sway here for a long
time. Tonight Tarzan will take the lair of the man-eater and Numa
may roar and grumble upon the outside."

The ape-man had advanced well into the gulch as he investigated
his surroundings and now as he stood near the tree, satisfied that
the tunnel would prove a dry and quiet retreat for the night, he
turned to retrace his way to the outer end of the entrance that he
might block it with boulders against Numa's return, but even with
the thought there came something to his sensitive ears that froze
him into sta