Ultraviolet light stimulated growth under all circumstances. Total darkness, and to a lesser extent infrared light, inhibited growth.

Oxygen inhibited growth in all circumstances, but carbon dioxide stimulated growth. Nitrogen had no effect.

Thus, best growth was achieved in 100-per cent carbon dioxide, lighted by ultraviolet radiation. Poorest growth occurred in pure oxygen, incubated in total darkness.

CULTURE DESIG - 779.233.187

ANDROMEDA

MEDIA DESIG - 779

ATMOSPHERE DESIG - 223

LUMIN DESIG - L87 UV/H1

FINAL SCANNER PRINT

An example of a scanner printout from the photoelectric eye that examined all growth media. Within the circular petri dish the computer has noted the presence of two separate colonies. The colonies are "read" in two-millimeter-square segments, and graded by density on a scale from one to nine.

"What do you make of it?" Stone said.

"It looks like a pure conversion system," Leavitt said.

"I wonder," Stone said.

He punched through the coordinates of a closed-growth system. Closed-growth systems studied bacterial metabolism by measuring intake of gases and nutrients, and output of waste products. They were completely sealed and self-contained. A plant in such a system, for example, would consume carbon dioxide and give off water and oxygen.

But when they looked at the Andromeda Strain, they found something remarkable. The organism had no excretions. If incubated with carbon dioxide and ultraviolet light, it grew steadily until all carbon dioxide had been consumed. Then growth stopped. There was no excretion of any kind of gas or waste product at all.

No waste.

"Clearly efficient," Stone said.

"You'd expect that," Leavitt said.

This was an organism highly suited to its environment. It consumed everything, wasted nothing. It was perfect for the barren existence of space.

He thought about this for a moment, and then it hit him. It hit Leavitt at the same time.

"Good Christ."

Leavitt was already reaching for the phone. "Get Robertson," he said. "Get him immediately."

"Incredible," Stone said softly. "No waste. It doesn't require growth media. It can grow in the presence of carbon, oxygen, and sunlight. Period."

"I hope we're not too late," Leavitt said, watching the computer console screen impatiently.

Stone nodded. "If this organism is really converting matter to energy, and energy to matter—directly—then it's functioning like a little reactor."

"And an atomic detonation . . ."

"Incredible," Stone said. "Just incredible."

The screen came to life; they saw Robertson, looking tired, smoking a cigarette.

"Jeremy, you've got to give me time. I haven't been able to get through to—"

Listen," Stone said, "I want you to make sure Directive 7-12 is not carried out. It is imperative: no atomic device must be detonated around the organisms. That's the last thing in the world, literally, that we want to do."

He explained. briefly what he had found.

Robertson whistled. "We'd just provide a fantastically rich growth medium.

"That's right," Stone said.

The problem of a rich growth medium was a peculiarly distressing one to the Wildfire team. It was known, for example, that checks and balances exist in the normal environment. These manage to dampen the exuberant growth of bacteria.