This book represents the proceedings of a NATO Advanced Research Workshop of the same name, held at St. Andrews University, Scotland in July of 1989. It was the first meeting of its kind and was convened as a forum to review and discuss the phylogeny of some of the cell biological functions that underlie nervous system function, such matters as intercellular communication in diverse, lower organisms, and the electrical excitability of protozoans and cnidarians, to mention but two. The rationale behind such work has not necessarily been to understand how the first nervous systems evolved; many...