This work on parasitology concentrates in detail on one group - the symbiotic platyhelminthes. As the majority of these symbiotes are parasitic, the author presents a detailed explanation of the nature of such associations. The book adopts an organismal/systematic approach setting the biology of parasitic platyhelminthes in an evolutionary context. Factual material is supplemented by illustrations and references. This text should appeal to parasitologists, evolutionary biologists and zoologists interested in animal associations. The text should be of interest to postgraduate students studying parasitology, biologists and naturalists, and parasitologists.