Nearly a millenium later, however, the Seed-Ship _Orana_ arrived. By that time humanity had spread very widely and very far. There were colonies not less than a quarter of the way to the Galaxy's rim, and Earth was no longer over-crowded. There was still emigration, but it was now a trickle instead of the swarming flood of centuries before. Some of the first-colonized worlds had emigrants, now. Mankind did not want to crowd itself together again! Men now considered that there was no excuse for such monstrous slums as overcrowding produced. Now, too, the star-ships were faster. A hundred light-years was a short journey. A thousand was not impractical. Explorers had gone many times farther, and reported worlds still waiting for mankind on beyond. But still the great majority of discovered planets did not contain life. Whole solar systems floated in space with no single living cell on any of their members. So the Seed-Ships came into being. Theirs was not a glamorous service. They merely methodically contaminated the sterile worlds with life. The Seed-Ship _Orana_ landed on this planet--which still had no name. It carefully infected it. It circled endlessly above the clouds, dribbling out a fine dust,--the spores of every conceivable microörganism which could break down rock to powder, and turn that dust to soil. It was also a seeding of moulds and fungi and lichens, and everything which could turn powdery primitive soil into stuff on which higher forms of life could grow. The _Orana_ polluted the seas with plankton. Then it, too, went away. More centuries passed. Human ships again improved. A thousand light-years became a short journey. Explorers reached the Galaxy's very edge, and looked estimatingly across the emptiness toward other island universes. There were colonies in the Milky Way. There were freight-lines between star-clusters, and the commercial center of human affairs shifted some hundreds of parsecs toward the Rim. There were many worlds where the schools painstakingly taught the children what Earth was, and where, and that all other worlds had been populated from it. And the schools repeated, too, the one lesson that humankind seemed genuinely to have learned. That the secret of peace is freedom, and the secret of freedom is to be able to move away from people with whom you do not agree. There were no crowded worlds any more. But human beings love children, and they have them. And children grow up and need room. So more worlds had to be looked out for. They weren't urgently needed yet, but they would be. Therefore, nearly a thousand years after the _Orana_, the Ecology-Ship _Ludred_ swam to the planet from space and landed on it. It was a gigantic ship of highly improbable purpose. First of all, it checked on the consequences of the _Orana's_ visit.