and were in the next room, and Giskard could hear the conversation clearly.

"Would this mean, do you suppose, that we Spacers are now a different species than Earthpeople?" was asking, as he listened to 's 'report'.

Every week, each roboticist would give the other a summary of how he was progress with the Auroran World Legislature, history, and biology.

Fastolfe was frowning.

"I'm not quite sure."he said, leafing through his papers. "The mutations are very minor, but they're there."

"It would mean almost that there are two species of humanity?"Sarton wasn't sure how else to put it.

"I don't know. Apparently, Aurorans are more adapted to Aurora, of course. Hmm, I wonder…would this mean that other Spacers are more adapted to their own worlds, as well?! If as you say, there are two species of humanity, then there would be fifty one?"

"I hadn't considered that."Sarton frowned. "But then that would also mean that among themselves, Spacers also couldn't interbreed with one another? An Auroran with a Hesperian, for example?"

"I hadn't considered that, either!"exclaimed Fastolfe.

He shuffled through his papers again.

"It's really extremely rare that any Spacer would interbreed with someone from another Spacer World! There are some early records of such incidents, but really, nothing very recent. After all, most Spacers have never left their native planet!"

Fastolfe frowned, and Sarton tapped his fingers on the table.

"But this would mean, as well, that Earth diseases wouldn't harm us. Terrestrial bacteria and viruses would only affect Earthmen! If we are completely different, that would mean they are probably harmless to us!"exclaimed Fastolfe.

"Of course!"agreed Sarton.

"I could be wrong, however."

"But that would help swing the Legislature to grant us permission."Sarton pointed out.

Fastolfe nodded, looking thoughtful.

"We must go to Earth, after all!"said Fastolfe. "It would be the only way to figure this out!"

Fastolfe put his papers aside.

"Hopefully this will serve as evidence for the Legislature."he handed the papers to Sarton. "Now,"he continued, moving on to a new subject. "I have come across something else. Among the history of Aurora, don't you see that less and less new planets have been colonized?"

"What do you mean?"

"Well…"Fastolfe wasn't sure how to explain himself. "It's just that there are only fifty inhabited worlds. Fifty one, if you count Earth. Earthpeople are short-lived, and they live that horrid existence, in those Cities, their planet over-populated, and here we are, long-lived, in our perfect worlds."

"And we must help Earthmen escape their planet to make them more comfortable or something? Is that what you're getting at?"asked Sarton looking amused.

Fastolfe chuckled.

"Perhaps. But no, no. It seems to me, well, Aurora is the most populous of the Spacer Worlds, as you know. In looking the mutations, which, by the way, also has to do with our long lives, did you know that? Like I said, I came across something new. In looking at the mutations, it has led me to…to other things."Fastolfe explained. "One being, not just genetics, but Auroran history. Our population is declining, as is that of the other Spacer Worlds."he finished.

Sarton stared.

"Well, how else would you expect to keep a decent standard of living? Enough space for everyone?"he asked.

Fastolfe shook his head.

"I'm no sociologist, of course, however, I've tracked it very carefully, and according to this, it would seem to me that if this keeps on, the Spacer Worlds will die out in a millennium or so."