"Let us say a culture wishes to scan the universe," he said. "Let us say they wish to have a sort of 'coming-out party' on a galactic scale—to formally announce their existence. They wish to spew out information, clues to their existence, in every direction. What is the best way to do this? Radio? Hardly—radio is too slow, too expensive, and it decays too rapidly. Strong signals weaken within a few billion miles. TV is even worse. Light rays are fantastically expensive to generate. Even if one learned a way to detonate whole stars, to explode a sun as a kind of signal, it would be costly.

"Besides expense, all these methods suffer the traditional drawback to any radiation, namely decreasing strength with distance. A light bulb may be unbearably bright at ten feet; it may be powerful at a thousand feet; it may be visible at ten miles. But at a million miles, it is completely obscure, because radiant energy decreases according to the fourth power of the radius. A simple, unbeatable law of physics.

"So you do not use physics to carry your signal. You use biology. You create a communications system that does not diminish with distance, but rather remains as powerful a million miles away as it was at the source.

"In short, you devise an organism to carry your message. The organism would be self-replicating, cheap, and could be produced in fantastic numbers. For a few dollars, you could produce trillions of them, and send them off in all directions into space. They would be tough, hardy bugs, able to withstand the rigors of space, and they would grow and duplicate and divide. Within a few years, there would be countless numbers of these in the galaxy, speeding in all directions, waiting to contact life.

"And when they did? Each single organism would carry the potential to develop into a full organ, or a full organism. They would, upon contacting life, begin to grow into a complete communicating mechanism. It is like spewing out a billion brain cells, each capable of regrowing a complete brain under the proper circumstances. The newly grown brain would then speak to the new culture' informing it of the presence of the other, and announcing ways in which contact might be made."

Samuels's theory of the Messenger Bug was considered amusing by practical scientists, but it could not be discounted now.

"Do you suppose," Stone said, "that it is already developing into some kind of organ of communication?"

"Perhaps the cultures will tell us more," Leavitt said.

"Or X-ray crystallography," Stone said. "I'll order it now."

Level V had facilities for X-ray crystallography, though there had been much heated discussion during Wildfire planning as to whether such facilities were necessary. X-ray crystallography represented the most advanced, complex, and expensive method of structural analysis in modern biology. It was a little like electron microscopy, but one step further along the line. It was more sensitive, and could probe deeper—but only at great cost in terms of time, equipment, and personnel.