1. Prior to spawning the thickness of the gonadal layer of shallow water oysters was approximately twice that of the oysters living at a 30-foot depth.2. The spawning of oysters at all depths began on and about July 9.3. The shallow water oysters discharged spawn in larger quantities and more rapidly than the oysters of deeper water.4. Among the oyster population living in shallow water there was a small group of individuals whose spawning was completed within a week.5. Ripe-but-unspawned oysters were found in the samples collected as late as six weeks after the beginning of the spawning season. This indicates that some of the ripe oysters, living under natural conditions, cannot always be induced to spawn by a relatively high temperature and or by the chemical stimulation caused by sex products discharged by the oysters living in the immediate vicinity.6. Approximately 50 per cent of the oyster population had half its spawn discharged by August 8. This date, therefore, is considered as the midpoint of the spawning period. Shallow water oysters reached the half-spawned stage several days earlier than the deep water individuals.7. The spawning activities of the oyster population, living at depths ranging from 10 to 30 feet, were finished about September 3. The majority of the shallow water oysters completed their spawning somewhat earlier than those of deep water.