The central idea of The Seedling Stars is that it is preferable to adapt human beings genetically to different planetary conditions (pantropy) rather than making the planets habitable for humans (terraforming). In the first story, this idea is considered to be criminal by the Greater Earth Port Authority, which, in the near future, controls space travel and wants to terraform Mars in order to collect landing fees and to get rid of part of the pullulating masses of Earth. Sweeney, a genetically altered man brought up in total isolation in a Moon laboratory, is sent to Ganymede. His task is to bring back for public execution a group of Adapted Men led by a scientist named Rullman. Their respiration is a complex hydrogen-to-methane cycle. Sweeney has been told that he will be changed back into an oxygen-breathing human once he has accomplished his mission, but on Ganymede he learns that this is impossible; only the offspring can be changed, not full-grown beings. He also discovers that the Adapted Men are not space pirates but are sought because the Authorities want to make an example of them and of pantropy. The Ganymedians succeed in sending off a seeding ship full of humans adapted to yet another galactic planet.
In “The Thing in the Attic,” heretics of a society living in the treetops of a giant forest world are sentenced to be lowered to the ground for doubting the existence of giants, which is claimed in their holy book. They survive on...
(The entire section is 439 words.)