Sally Coulthard explores the miraculous world of the earthworm, the modest little creature without whom life as we know it would not be possible. For Charles Darwin - who estimated every acre of land contained 53,000 earthworms - the humble earthworm was the most important creature on the planet. And yet, most people know almost nothing about these little engineers of the earth. 'The Book of the Earthworm' offers a feast of quirky facts and practical advice about the world's most industrious - but least understood - invertebrate.