This excellent translation of the German Das Phylogenetische System explains, simply and logically, the functions of the phylogenetic system how it must be built up. Written by one of Germany's most distinguished systematic zoologists, the text clarifies several basic concepts, such as monophyly, the stem lineage, autapomorphy, and synapomorphy. The presentation is illustrated mainly by examples drawn from arthropods and vertebrates and will thus be widely intelligable to students of biology.