red Jim to Denny. "How do they know their city
is besieged just at this spot, and that their help is needed?"

Dennis shrugged. His eyes were shining. This was the kind of thing he
had come here for. This unhampered observation of a strange and terrible
race at war and at work--it was well worth all the personal risks he
might run.

"No man can answer your question, Jim. They're blind--they can't see
their danger so as to know how to combat it. They couldn't hear, and be
alarmed by, the vibrations of battle for a distance of more than a few
yards. My only guess is that they are constantly and silently commanded
by the unknown intelligence, the ruling brain, that hides deep in the
earth beneath us and directs these 'soldier' termites in some marvelous
way--though itself never seeing or hearing the actual dangers it guards
against."

"The queen?" suggested Jim.

Again Denny shrugged. "Who knows? She might be the brains, as well as
the egg layer, of the tribe. But don't talk too much. The vibration of
our voices might lead them to us in spite of their blindness."

* * * * *

Now the main avenue before them was humming with a new kind of traffic.
From side to side it was being filled with a new sort of termite. These
were smaller than the soldiers, and entirely unprotected by either horn
armor plate or slashing mandibles.

Each of these carried an unwieldy block of gleaming substance. And each
in turn dropped its block in a growing wall behind the savage defenders
against the ants, and fastened it in place with a thick and viscous
brown liquid that dried almost immediately into a kind of cement.

"The workers," whispered Dennis, enthralled. "The building blocks are
half-digested wood. The cement is a sort of stuff that exudes from
their own bodies. In ten minutes there will be a wall across the tunnel
that no ants on earth could penetrate!"

"But the home guards, the brave lads and all that sort of thing, will be
shut off on the outside of the wall with the enemy. And there are
hundreds of the enemy," protested Jim.

"A necessary sacrifice," said Denny. "And so perfect is their
organization that no one, including the soldiers to be sacrificed, ever
makes any objection."

Jim shivered a little. "It's terrible, somehow. It's--it's inhuman!"

"Naturally. It's insectian, if there is such a word. And a wise man once
predicted that the termite organization, being so much more perfect a