The gametogenesis of the surf clam, Tresus keenae, were investigated by SEM and TEM. Both the testis and the ovary had follicle tubes surrounded by inter-tubal tissue composed of adipogranular cells that provided storage function. In the vitellogenic oocyte, lipid droplets and lipid yolk granules were found in the vacuoles formed by the Golgi apparatus. Proteid yolk granules were formed by the endoplasmic reticulum and cortical granules in the cytoplasm during vitellogenesis. The mature sperm was primitive and resembled a jar with a cover. The sperm heads were approximately $2.00-2.30 {cal}um$. The acrosomal rod projected in front of the acrosome. In addition, four large mitochondria were in the midpiece.