Isopod crustaceans are a diverse and ecologically important group of arthropods that range from terrestrial habitats to the deep sea. They constitute an early and successful evolutionary branch of the crustacean family tree. Dr. George Wilson of the Scripps Institute of Oceanography proposes a study of the evolutionary relationships among the major groups of isopods. Representative species from all isopod suborders will be sampled for histological sectioning, light, and electron microscopy. Genitalic anatomy and morphology will provide most of the data for an analysis of evolutionary relationships. The proposed research will establish an evolutionary framework for the isopod crustaceans, thereby creating a platform on which other research projects can be built. As a result of this project, future studies of the form, function, development and biogeography of isopods will be set in an evolutionary context, providing new insight into the history of crustaceans and the process of evolution itself.