Abstract
The gonad and gametogenesis in a common species of chiton, Acanthopleura (=Liolophura) japonica (Lischke), have been studied by paraplast section using both Azan and Feulgen staining methods. The gonad showing a single lobulated structure is located along the dorsal aorta under the shell valves. In both ovary and testis, flattened ovarian and testicular folds are elongated from the germinal epithelium onto the dorsal aorta. Oocytes in three different developmental stages can be distinguished in the ovary ; previtellogenic, vitellogenic and full-grown oocytes. Oocytes of the former two stages are attached to the ovarian folds, while oocytes in the last stage are scattered in the lumen of the ovary. The breakdown of oocytes is often found to occur and a number of them will disappear before maturation. In the testicular folds, the spermatogonia layer is nearest to the basal membrane, and next, are layers of primary spermatocytes and spermatids respectively. Spermiogenesis occurs in the lumen of the testis.
