Professor Christian Danchekker was perplexed. One of the cornerstones of what had been regarded as an unquestionable and universal tenet of biological theory looked as if it might be resting on shaky ground. Accepted scientific beliefs had not been arrived at lightly, and he was not of a nature to change them lightly.

He sat hunched in his office in the Biosciences building at Goddard, his lean, balding frame and gangling limbs splayed at an odd composition of angles in one of those chairs that never seemed to be the right size or shape no matter how many models he tried, and frowned at the offending papers strewn around the desk, while he polished the lenses of his anachronistic gold-rimmed spectacles. Then he perched them back on the bridge of his nose and returned his attention to the references that he had listed on one of the displays on the side panel. The reports were on work done in various places around the world to duplicate and extend some experiments performed by a research group in Australia on nutrient-metabolizing pathways in certain strains of bacteria. In general, each type of bacterium depended on a primary food that it possessed the genes to break down and utilize. Probably the most familiar example was the common E. coli, found in humans, which required the sugar lactose. It sometimes happened that if the mechanism to digest the primary food was disabled, mutations were possible that could create an alternative metabolic pathway to exploit a different food instead. In the case of E.coli, two particular point mutations occurring simultaneously enabled it to feed on a different sugar. The mutation rates were known, and under the conditions of a typical laboratory experiment would be expected to occur together about once in a hundred thousand years. In practice, scores of examples were observed within a few days. But it happened only when the alternative target sugar was present in the nutrient solution used for the culture.

What this meant was that the mutations were not random, as biological doctrine had steadfastly maintained for over a century, but triggered by cues in the environment. And that in turn meant that the genetic "programs" for responding to those cues must already have been there, in the bacterial genome to begin with. They hadn't arisen over millions of years of trial-and-error selection from random mutations. The process by which it was achieved had been uncovered in the form of messenger proteins encoding externally acquired information that was written into the genome by special-purpose enzymes-misinterpreted as components of antibodies to viruses that turned out never to have existed, and a cause of a huge medical scandal and a spate of class-action suits in years gone by. One of the central dogmas of evolutionary theory was thus shown to be violated. That the whole business was a far more complex affair than had been confidently supposed was, to put it mildly, the least troubling interpretation that could be put on it.

Danchekker still wasn't sure if a senior directorship in the UNSA hierarchy, with all the attendant bureaucratic chores and deference to academic convention, really suited him. In his quieter moments, when he relaxed in his apartment to the music of Mahler or Berlioz, or sat contemplating the trees by some secluded tributary of the Potomac, his mind still soared with the Jupiter mission ships to the icy wastes of Ganymede and saw again the pale green, orange-streaked skies of Jevlen above the towering alien cityscapes. Across the vast tract of worlds that the Thuriens had spread to, there dwelt more strange and wondrous forms of life than could be so much as glimpsed in the remainder of a lifetime. On Crayses there was a creature that was both animal and plant, rooting itself in the ground when conditions were agreeable, moving on when they changed. Yaborian Two had somehow produced a reversed planetwide chemistry in which oxy-carbon based life flourished in a reducing atmosphere of methane.

He realized that he had drifted away into musings again when Sandy Holmes, his technical assistant, stuck her head in from the lab area outside the office. Divisional director or not, Danchekker wouldn't let administrative matters prevent him from keeping his practical hand in. Taking care of them was what staff were for. He refused to accept calls while he was working.

"Excuse me, Professor?"

"Hm? What?… Oh." Danchekker returned reluctantly to planet Earth. He sighed and gestured at the papers lying in front of him. "It appears that much of what we considered to be unquestionable may have to be rethought from basics, Sandy. The development of organisms is much more closely coupled with the environment than existing theory can account for. You need to read this… Anyway, what is it?"

"Mildred is downstairs in reception. You're due to have lunch with her, remember?"

"Ah, yes." Normally, Danchekker blanched at the mention of the name. His cousin from Austria had been camped in the Washington, DC, area for a couple of months while researching her latest book, which was on Thurien culture and sociology. She had latched onto Danchekker as her prime reference and research source. But today he was actually looking forward to seeing her. "Can you organize an aircab to the front door for us, Sandy?"

"It's on its way. I told them, the Olive Tree. Is that okay?"

"That will do splendidly."

"And Ms. Mulling asked me to remind you that you're meeting Vic Hunt and Gregg Caldwell at the Carnarvon at six-thirty tonight." Ms. Mulling was Danchekker's personal secretary, whom he thankfully left to take command of administrative and fiscal matters from her domain on the far side of the top floor, from whence she ruled the building. She had come with his appointment as director in the UNSA reorganizational shuffle and was the main reason for his refusing to take calls when immersed in the things that interested him. Her name was usually sufficient to evoke a reflex grimace too, but on this occasion Danchekker merely nodded matter-of-factly as he slipped off his lab coat and draped it on the stand inside the door. "You seem in great spirits today, Professor," Sandy remarked as she walked with him back across the lab area to where she had been working with a technician preparing microscope slides.

"It looks as if our devious scheme is about to pay off," Danchekker replied breezily. "A week from now, our persistent and pestering authoress will be on her way to distant reaches of the Galaxy, and peace will return to the realm."

"You've heard back from Frenua?"

"Earlier this morning. It's as good as arranged. You know how informal the Thuriens are. I shall convey the joyous tidings forthwith, over lunch, and I have no doubt that cousin Mildred will be suitably thrilled."

"I'm glad it worked out. Enjoy your lunch."

"Oh, indubitably."

Danchekker hummed to himself in the elevator all the way down, oblivious of the clerk carrying a sheaf of papers who got in at the eighth floor and left at the fifth. When the doors opened on the ground level, he sailed out with a broad, toothy smile to greet his cousin, waiting in the lobby area beyond. Mildred was momentarily taken aback but recovered quickly.

"Christian, you're exactly on time! You look quite on top of the world today."

"And why not? I might ask. We should not let the chores of our humdrum lives mar the splendor of such a heaven-sent day. I can see more shades of green from my window on the top floor than would grace a legion of leprechauns." Danchekker held the main door aside graciously to usher Mildred through. She looked at him uncertainly.

"Are you all right?"

"Never better. And you look radiant too-a fitting tribute to spring."

In fact, Danchekker thought she looked mildly ridiculous in one of those floppy, wide-brimmed hats with flowers that even he knew had been out of style for years, a floral dress that was doubtless practical but seemed grannyish, and a pair of equally practical lightweight boots that might have done service on the Appalachian Trail. But beyond that, she talked.