ng to ask him when he sprung it on us first, but
he was pretty busy then and I haven't thought of it since. Something
pretty serious, though--they've jumped their acceleration almost to
Tellurian gravity, and none of them can live through much of that."

"Tellurians?" came the voice of Barkovis from the speaker. "We have
just...."

"All x--we were on your wave and heard it," interrupted Stevens. "We're
with you. What are those Sedlor, anyway? Maybe we can help you dope out
something."

"Perhaps--but whatever you do, do not use your heat-projector. That
would start a conflagration raging over the whole country, and we shall
have enough to do without fighting fire. But it may be that you have
other weapons, of which we are ignorant, and I can use a little time in
explanation before we arrive. The Sedlor are a form of life, something
like your..." he paused, searching through his scanty store of Earthly
knowledge, then went on, doubtfully, "perhaps some thing like your
insects. They developed a sort of intelligence, and because of their
fecundity, adapted themselves to their environment as readily as did
man; and for ages they threatened man's supremacy upon Titan. They
devoured vegetation, crops, animals, and mankind. After a world-wide
campaign, however, they were finally exterminated, save in the
neighborhood of one great volcanic crater, which they so honeycombed
that it is almost impregnable. All around that district we have erected
barriers of force, maintained by a corps of men known as 'Guardians of
the Sedlor.' These barriers extend so far into the ground and so high
into the air that the Sedlor can neither burrow beneath them nor fly
over them. They were being advanced as rapidly as possible, and in a
few more years the insects would have been destroyed completely--but
now they are again at large. They have probably developed an armor or
a natural resistance greater than the Guardians thought possible, so
that when the walls were weakened, they came through in their millions,
underground and undetected. They are now attacking our nearest city--the
one you know, and which you have called Titania."

"What do you use--those high-explosive bombs?"

"The bombs were developed principally for use against them, but proved
worse than useless, for we found that when a Sedlor was blown to pieces,
each piece forthwith developed into a new, complete creature. Our most
efficient weapons are our heat rays--not yours rememb