The reproductive cycle in a typical estuarine mollusc Nausitora hedleyi Schepman based on a study of the Gonad Index

1. Previous work on the methods employed for the determination of the breeding season of shipworms is briefly reviewed.
2. The method adopted for studying the reproductive cycle by using the “gonad index” is described.
3. The reproductive cycle of Nausitora hedleyi is described in detail based on a study of the gonad index of different sexes collected at monthly intervals from the estuarine environment of Cochin harbour.
4. The fact that breeding is restricted as marked by seasonal activity is shown from the size and activity of the gonad during the different months of the year.
5. The environment, and the hydrographic conditions prevailing in the habitat of N. hedleyi in the Cochin harbour are described.