The territorial and courtship behaviour of C. cyanea was studied on a reef off the South-coast of Curaçao, Netherlands Antilles. Protocols of the behaviour were made by means of an underwater taperecorder. The protocols were subjected to sequence analysis. The result of this analysis showed that the different motor-patterns could be ranked into groups characterized by the motor-patterns within a group showing more correlations among them then with motor-patterns outside this group. Further analysis showed that the associations of motor-patterns could be ascribed to them having internal factors in common. In this way different behavioral systems could be distinguished. The occurrence of different colour patterns shown by C. cyanea was also analyzed. It appeared that the presence of each colour pattern was correlated with a specific group of motor-patterns. These groups appeared to be the same as distinguished in the analysis of the motor-patterns. The correlation between the colour patterns and motor-patterns could be shown to be based on internal factors. The nature of the linkage between the behavioral systems and the mechanism controlling the colour patterns is discussed and it appears that the colour patterns can be used to gain further insight into the causation of the different motor-patterns. In the discussion I tried to show that the results of the analysis of the courtship behaviour are open to other explanations than the traditional one in which it is assumed that the causation of courtship behaviour is dependent on the interactions of three systems, i.e., sex, aggression and flight. A more parsimonious explanation of the data shows that there is no need to assume a separate sexual system for the causation of the courtship actions. These actions can be explained by interactions between an aggressive and a nesting system. The proportion in which each of these systems partakes in the causation of each separate action is regulated by a different system.