The structure and function of the digestive diverticula of Sinonovacula constricta were studied using light and transmission electron microscopy and histochemical methods .The digestive diverticula is the type of compound tubuloacinar gland which communicates with the stomach by a system of ducts .The glandular epithelium is composed of four types of cells :embryo cell (E-cell), fibrillar cell(F-cell), resorptive cell(R-cell) and secretory cell(B-cell).These cells are different from each other in distribution , structure and function .E-cells are mostly located at the proximate position of tubules connecting the duct and the big nuclear-cytoplasmic ratio shows that they may be involved in mitotic activity for production of other cell types which comprise the glandular epithelium.F-cells contain plenty of rough endoplasmic reticulum and free ribosome suggesting that they may synthesize and secrete digestive enzymes .Lipid and glycogen are abundant throughout R-cells suggesting that these cells are the sites of significant energy stores .B-cells distribute only in the distal end of alveoli and have their cytological features :congested microvilli on the free border , numerous secondary lysosome and residual body support the view that B-cells are capable of absorption and intracellular digestion of food .B-cells and R-cells have the strong function of digesting lipid .The duct is composed of simple ciliated columnar epithelium and abundant mucous cell , and the former can synthesize and secrete digestive enzymes .The digestive diverticula may also participate in the metabolism of inorganic salt .