Jellyfish

While they may be outnumbered and outweighed by insects, the terrestrial world is really the kingdom of the vertebrates. Mammals, birds, reptiles and amphibians dominate most ecosystems. Yet, as Drew Harvell points out in her fascinating new book, the seeming diversity of the terrestrial vertebrates is deceptive. In fact all are contained within just one of the 34 groups of animals that live on our planet, and their many designs are really variations on a quite narrow set of themes. This means that all share bilateral symmetry – heads with eyes and brains atop bodies with four limbs that contain their organs. By contrast, the other 33 groups of animals,

Philip Reeve roams across realms of his own making with effortless brio. If I say that Thunder City (Scholastic, £8.99) is based on the premise that the world’s great cities have detached themselves from their terrestrial foundations and are floating across the sky like so many urban space ships, swallowing up smaller fry, you’d probably think this is asking a bit much of the reader, but somehow you take it all on board. In this futuristic scenario the characters and their modes of thinking are in fact rather quaint – like Miss Torpenhow, a governess whose floating town of Thorbury has been captured by a diabolical former protégé. The assurance