general questions that are unapproachable in the more complex nervous systems of higher animals. Nevertheless, a curiosity about nervous system evolution has invariably pervaded much of the work. The return on this effort has been mixed, depending to a large extent on the usefulness of the preparation under examination. For example, work on cnidarians, to many the keystone phylum in nervous system evolution simply because they possess the "first" nervous systems, lagged behind that carried out on protozoans, because the latter are large, single cells and, thus, far more amenable to microelectrode-based recording techniques. Furthermore, protozoans can be cultured easily and are more amenable to genetic and molecular analyses.