Salmon divergence. Salmon eggs are laid in freshwater streams typically at high latitudes. The eggs hatch into alevin or sac fry. The fry quickly develop into parr with camouflaging vertical stripes. The parr stay for six months to three years in their natal stream before becoming smolts, which are distinguished by their bright, silvery colour with scales that are easily rubbed off. Only 10% of all salmon eggs are estimated to survive to this stage. The smolt body chemistry changes, allowing them to live in salt water. While a few species of salmon remain in fresh water throughout their life cycle,
The Salmon of Doubt six is a better kind of number." The book as published is divided into two main sections: "Life, the Universe and Everything", which utilizes fiction, essays and interviews with Adams, and "The Salmon of Doubt", which presents the most complete version of the novel as Adams left it. The first section is then subdivided into three: "Life" touches upon Adams' own life, "The Universe" covers Adams' views of reality and "Everything", which is more wide open and includes the original version of the Hitchhiker's short story "Young Zaphod Plays It Safe". The UK edition includes an introduction by Stephen Fry,