Investigations of modular systems encompass many colonial organisms with a high level of morphological and physiological integration. Bryozoan colonies are a very promising model in this respect, and studies of colonial behaviour are one of the approaches in evaluating the degree of colonial integration. Bryozoans demonstrate a variety of group behavioural reactions which are connected with different vital functions. Co-ordinated activities of polypides are regulated neurophysiologically, physiologically, structurally and, possibly, hormonally. Different manifestations of the regulatory mechanisms have been studied previously, and we here present a review that discusses the history of theseinvestigations.