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 of the animals in question provide excellent opportunities for examining 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.

Zusammenfassung
Proceedings of a NATO ARW held at St. Andrew's University, Scotland, July 2-5, 1989

Inhalt
I. Intercellular Communication.- 1 Cnidarian Gap Junctions: Structure, Function and Evolution.- 2 Intercellular Junctions in Ctenophore Integument.- 3 Chemical and Electrical Synaptic Transmission in the Cnidaria.- 4 Control of Morphogenesis by Nervous System-derived Factors.- 5 Differentiation of a Nerve Cell-Battery Cell Complex in Hydra.- 6 Chemical Signaling Systems in Lower Organisms: A Prelude to the Evolution of Chemical Communication in the Nervous System.- 7 Neurons and their Peptide Transmitters in Coelenterates.- 8 Peptidergic Neurotransmitters in the Anthozoa.- 9 Catecholamines, Related Compounds and the Nervous System in the Tentacles of some Anthozoans.- 10 The Antiquity of Monaminergic Neurotransmitters: Evidence from Cnidaria.- 11 Rethinking the Role of Cholinergic Neurotransmitters in the Cnidaria.- 12 Wide Range Transmitter Sensitivities of a Crustacean Chloride Channel.- 13 Two Pathways of Evolution of Neurotransmitters-Modulators.- 14 Summary of Session and Discussion on Intercellular Communication.- II. Electrical Excitability.- 15 Ion Channels of Unicellular Microbes.- 16 Ion Currents of Paramecium: Effects of Mutations and Drugs.- 17 Membrane Excitability and Motile Responses in the Protozoa, with Particular Attention to the Heliozoan Actinocoryne contractilis.- 18 Ion Channels and the Cellular Behavior of Stylonychia.- 19 Ionic Currents of the Scyphozoa.- 20 The Electrophysiology of Swimming in the Jellyfish Aglantha digitale.- 21 Ionic Currents in Ctenophore Muscle Cells.- 22 Polyclad Neurobiology and the Evolution of Central Nervous Systems.- 23 Enigmas of Echinoderm Nervous Systems.- 24 Summary of Session and Discussion of Electrical Excitability.- III. Sensory Mechanisms.- 25 Chemoreception in Unicellular Eukaryotes.- 26 The Functional Significance of Evolutionary Modifications found in the Ciliate, Stentor.- 27 Hydromedusan Photophysiology: An Evolutionary Perspective.- 28 Summary of Session and Discussion on Sensory Mechanisms.- IV. Plenary Lecture.- 29 Evolution of Cnidarian Giant Axons.- 30 Concluding Remarks.