The barnac1e Balanus amphitrite communis Darwin is one of the most serious marine fouling organisms found in the vicinity of Tsingtao. Its breeding season begins at the middle of May when water temperature rises above 16℃ and continues up to the end of December. Maturation of the gonad of each individual is periodic at intervals of about 2-3 weeks. It is longer in the early summer while the temperature is lower and becomes shorter in September. In winter, even the gonad is atrophic, breeding cycle may be rcstored if they are reared in 26℃ water for about one month. Temperature is onc of the most important factor influencing the breeding cycle of this species.