In the little-neck clam,Paphia staminea, as occurring in British Columbia waters, the first sign of the gonad was found in individuals slightly over 1 mm. in length. Sex differentiation occurs at lengths of 15 to 30 mm. or in 2nd or 3rd year. Maturity is achieved at 22 to 35 mm.P.stamineais not protandric. Seasonal gonad changes are: by end of October all active spawning over; by December to January tubules of ovary filled with follicle cells; active growth of sex cells reaches peak in March; first spawning in April and by September most clams spawned out. Male spawning cycle parallels that of female, with certain time lag apparent. Some males may remain in spawned-out state during most of winter.