1. Hat is Communication?.- Problems Of Definition.- The interval between emission and response.- Variability in communication behaviour.- Contextual information.- The Functions Of Communication.- Interspecific interactions.- Intraspecific interactions.- Exploitation Of Existing Communication Systems.- 2. Sensory Systems.- The Nature of the Stimulus and the Receptor.- The complement of receptors.- Perception and reception.- Perceptual capability, behavioural approach.- Receptor capability, physiological approach.- Principles And Constraints In Sense Organ Design.- The Coding of Basic Stimulus Parameters.- The Coding Of Complex Stimulus Parameters.- Form and pattern.- Directional sensitivity.- Frequency discrimination and analysis.- Conclusions.- Acoustic communication in insects and birds.- Visual communication in the firefly and the stickleback.- Comparison of visual and other modalities.- 3. External Stimuli, Internal Factors and Behaviour.- Sign Stimuli and the Innate Releasing Mechanism.- Intervening Variables in Behaviour.- Selective attention.- Centrifugal control.- Feedback control.- The "reafference" principle.- Motivational Gating.- Conclusions.- 4. Integration and the Control of Behaviour.- Mechanisms of Filtration and Integration.- Synaptic processes.- Axonal processes.- Non-spiking interneurones.- Examples Of Central Sensory Integration.- The olfactory system.- The auditory system.- The visual system.- Multimodal integration.- The Motor System And Behaviour.- The fixed action pattern-a valid concept?.- Reflex control.- Control by central pattern generators.- Command neurones.- Conclusions.- 5. Signals and Their Evolution.- Chemical Signals and Their Evolution.- Acoustic Signals.- Characteristics of the acoustic channel.- Mechanisms of sound production.- Evolution of song patterns in Orthoptera.- Further considerations.- Visual Signals and Their Evolution.- Origins and Evolution of Vertebrate Signals.- Behaviour resulting from "conflict" of underlying tendencies.- Ritualization.- Numbers of Displays.- Conclusions.- 6. The Shaping of Communication Sequences, Courtship.- Butterfly Courtship.- Fish Courtship.- Courtship in the Newt, the Problem of the Spermatophore.- Courtship in Birds.- Conclusions.- 7. Some Methods of Analysing Sequences of Behaviour.- Intra-Individual Transition Matrices.- Inter-Individual Matrices.- Information Analysis.- Multivariate Analysis.