d
quietly. "They make study difficult by dying. It's as if they knew that
they couldn't win here. So they retreat--to keep their secrets. But Dr.
Pacetti, our head of Medical Research, says that we can never know that
they won't find a way to attack us directly. That's what the waiting
napalm line is for. I don't think he is exaggerating."

"Why do you say that?" Nelsen asked.

He was encouraging her, of course. But he wasn't being patronizing.
Frost tingled in his nerves. He wanted to know her version.

"I'll show you the little museum we have," she replied, her eyes
widening slightly. "This is probably old hat to you--but it's weird--it
gives you the creeps..."

He followed her along a covered causeway to another dome. In a gallery
there, a series of dry specimens were set up, inside sealed boxes made
of clear plastic.

The first display was centered around a tapered brass tube--perhaps one
of the barrels of an antique pair of fieldglasses. Wrapping it was a
spiny brown tendril from which grew two sucker-like organs, shaped like
acorn tops. One was firmly attached to the metal. The other had been
pulled free, its original position on the barrel marked by a circular
area of corrosion. The face of the detached sucker was also shown--a
honeycomb structure of waxy vegetable tissue, detailed with thousands of
tiny ducts and hairlike feelers.

"Some settler dropped the piece of brass out on a trail in Syrtis
Major," Nance explained. "Later, it was found like this. Brass is
something that people have almost stopped using. So, it was new to
_them_. They wouldn't have been interested in magnesium, aluminum, or
stainless steel anymore. The suckers aren't a usual part of them either.
But the suckers grow--for a special purpose, Dr. Pacetti believes. A
test--perhaps an analysis. They exude an acid, to dissolve a little of
the metal. It's like a human chemist working. Only, perhaps,
better--more directly--with specialized feelers and sensing organs."

Nance's quiet voice had a slight, awed quaver at the end.

Frank Nelsen nodded. He had examined printed pictures and data before
this. But here the impact was far more real and immediate; the impact of
strange minds with an approach of their own was more emphatic.

"What else?" he urged.

They stood before another sealed case containing a horny, oval pod, cut
open. It had closed around a lump of greenish stone.

"Malachite," Nance breathed. "One kind of copper ore. _They