Originally published during the early part of the twentieth century, the Cambridge Manuals of Science and Literature were designed to provide concise introductions to a broad range of topics. They were written by experts for the general reader and combined a comprehensive approach to knowledge with an emphasis on accessibility. Geoffrey Smith's Primitive Animals, which was first published in 1911, contains an account of the chief groups in the animal kingdom and the evidence by which some of the main streams of animal evolution can be traced.