This book succeeds in bringing together the previously scattered literature on invertebrate phylogeny, forming a unique introduction to this fascinating and controversial subject. Phylogenetic study is an important corner-stone of biology, for the evolutionary relationships between groups of animals bear heavily upon the analysis of their physiology, behavior and ecology. Until now, there have been few books which analyse the diversity of animal life in terms of its origins and the relationships between different groups. After reviewing the current state of the subject, the author discusses the various sources of evidence which bear upon the question of how living animals are related to each other. Then, these lines of evidence are applied to particular groups of invertebrates. The prevalence of convergent evolution is a strong theme, as it becomes clear that many features, from details of cell chemistry and structure to overall body plan and life history, have been invented repeatedly and independently under similar selection pressures. Pat Willmer has drawn upon her experience teaching invertebrate zoology to undergraduates at Cambridge and Oxford to produce a stimulating, meaningful account of the relationships between invertebrate phyla and of the phylogenetic pattern of the animal kingdom.