Tubule and duct of digestive diverticula in thirty species of Bivalvia（four species of Arcoida and four species of Mytiloida in Filibranchia, three species of Pterioida and five species of Ostreoida in Pseudolamellibranchia, and one species of Unioida and thirteen species of Veneroida in Lamellibranchia) were observed histologically with the sections stained with Mallory-Azan dye. The tubule of Filibranchia show the simple branching type II（The tubules branch off irregularly from regions more or less distant from the distal ends of the ducts), and those of Lamellibranchia the simple branching type I（The tubules always branch off from the distal end of the duct). In Pseudolamellibranchia, three species of Pterioida (Pearl oyster Pinctada fucata martensii, Black-lip pearl oyster P. margaritifera and Pen shell Atrina （Servatrina）lischkeana）and three species of Ostreidae（Japanese oyster Crassostrea gigas, Rockoyster C. nippona and Spiny oyster Saccostrea kegaki）show the simple branching type I. However, two species of Pectinidae in Ostreoida（Akazara-scallop Chlamys（Azumapecten）farreri nipponensis and Common scallop Patinopecten yessoensis）show the simple branching type II.