THE ANNUAL REPRODUCTIVE CYCLE OF AN APODOUS HOLOTHURIAN, LEPTOSYNAPTA TENUIS: A BIMODAL BREEDING SEASON.

1. Gonads of Leptosynapta tenuis were examined histologically, and gametogenesis in this apodid holothurian is described. 2. L. tenuis is a simultaneous hermaphrodite. Each animal produces and sheds spermatozoa and oocytes during the same breeding season, although sperm seem to be shed somewhat earlier than oocytes. 3. Testicular maturity indices and oocyte diameter measurements revealed a bimodal annual reproductive cycle in a North Carolina population sampled at monthly intervals over a fifteen-month period. Breeding occurred for about three months both preceding and following a month, or so, of breeding inactivity in July or August. 4. The mid-summer absence of mature gametes in the population coincided with the highest seawater temperatures, suggesting a temperature regulated gametogenic cycle. 5. The high oocyte growth rate leading to the second spawning season in the autumn is perhaps five times that of the winter rate.