Summary
The intertidal sandy-beach mysid, Gastrosaccus psammodytes, has been studied with respect to burrowing behaviour, substrate discrimination, reactions to water currents, responses to light, detection of changes in hydrostatic pressure, methods of feeding, reproduction and development, and distribution. Some mention is also made of the animal's defence mechanisms, its tolerance of reduced salinities and certain other aspects of its ecology. Despite the success with which G. psammodytes has colonized the intertidal zone of surf-swept sandy beaches, it is concluded that this colonization has been achieved without drastic deviation from the usual mysid patterns of structure and behaviour.