The most conspicuous function of the nervous system is to control animal behav­ ior. From the complex operations of learning and mentation to the molecular con­ figuration of ionic channels, the nervous system serves as the interface between an animal and its environment. To study and understand the fundamental mecha­ nisms underlying the control of behavior, it is often both necessary and desirable to employ biological systems with characteristics especially suitable for answering specific questions. In neurobiology, many invertebrates have become established as model systems for investigations at both the systems and the cellular level. Large, readily identifiable neurons have made invertebrates especially useful for cellular studies. The fact that these neurons occur in much smaller numbers than those in higher animals also makes them important for circuit analysis. Although important differences exist, some of the questions that would be tech­ nically impossible to answer with vertebrates can become experimentally tractable with invertebrates.

Table of Contents:
I. Neural Circuitry.- 1 Tritonia Swimming: A Model System for Integration within Rhythmic Motor Systems.- 2 Neural Networks Controlling Locomotion in Locusts.- 3 Neural Mechanisms for the Production of the Lobster Pyloric Motor Pattern.- 4 Extrinsic Inputs and Flexibility in the Motor Output of the Lobster Pyloric Neural Network.- 5 Modulation of Central and Peripheral Rhythmicity in the Heartbeat System of the Leech.- 6 Neural Network Analysis in the Snail Brain.- 7 Nonspiking and Spiking Local Interneurons in the Locust.- II. Development.- 8 Metamorphosis of the Insect Nervous System: Influences of the Periphery on the Postembryonic Development of the Antennal Sensory Pathway in the Brain of Manduca sexta.- 9 The First Neuronal Growth Cones in Insect Embryos: Model System for Studying the Development of Neuronal Specificity.- 10 The Development of Serotonin-containing Neurons in the Leech.- 11 Dynamic Regulators of Neuronal Form and Connectivity in the Adult Snail Helisoma.- III. Learning and Plasticity.- 12 Cellular Studies of an Associative Mechanism for Classical Conditioning in Aplysia: Activity-dependent Presynaptic Facilitation.- 13 The Logic of Limax Learning.- 14 Neural Mechanisms of Behavioral Plasticity in an Invertebrate Model System.- IV. Neurotransmitters and Neuromodulators.- 15 Neuropeptides and the Control of Egg-laying Behavior in Aplysia.- 16 The Central Nervous System of Aplysia californica: A Model System for Cellular Studies of Central Neurotransmission.- 17 Neurotransmitter Modulation of the Stomatogastric Ganglion of Decapod Crustaceans.- 18 The Well-Modulated Lobster: The Roles of Serotonin, Octopamine, and Proctolin in the Lobster Nervous System.- 19 Neurosecretory Role of Crustacean Eyestalk in the Control of Neuronal Activity.- 20 Activationof Neuronal Circuits by Circulating Hormones in Insects.- 21 Are Skeletal Motoneurons in Arthropods Peptidergic?.- V. Cellular and Membrane Biophysics.- 22 Electrical Behavioral Correlates of Calcium and Potassium Currents in Molluscan Nerve Cells.- 23 Calcium and cAMP: Second Messengers in Gastropod Neurons.- 24 Synaptic Facilitation and Residual Calcium.- VI. Neurogenetics and Molecular Neurobiology.- 25 A Monoclonal Antibody to an Internal Molecule Differentiates Three Electrically Coupled Leech Neurons.- 26 Neuropeptide Gene Expression and Behavior in Aplysia.- 27 The Drosophila Thorax as a Model System for Neurogenetics.- 28 Genetic and Molecular Studies of a Potassium Channel Gene in Drosophila.