Abstract: Objective To examin and analyze the structure, ultrastructure and the circulation of the spleen ellipsoid in the soft-shelled turtle, EM>Pelodiseus sinensis/EM>.  Methods Twelve turtles were used and observed by light- and electron-microscopy and injection of ink suspension in this study. Results The spleen white pulp was consisted of the periarteriolar lymphatic sheath (PALS) and periellipsoidial lymphatic sheath (PELS). There was no lymphoid nodule in the spleen. Red pulp included splenic cords and splenic sinusoids. The marginal zone was not found in the turtle spleen. When the central arteriole left out of the PALS, it divided into several ellipsoid capillaries which were surround by the PELS. The end of the ellipsoid capillary opened directly to the splenic cord and the blood cells then entered into the splenic sinusoid through the gap between the endothelial cells. The ellipsoid capillary was consisted of simple cuboidal epithelium with an uncompleted basement membrane. The ellipsoid wall was consisted of supporting cells,ellipsoid-associated cells and reticular fibres. Lymphocytes and red cells were always found on the ellipsoid wall. After 40min of the injection of ink suspesion, much carbon particles of ink were restricted on the wall. Conclusion The ellipsoid capillary in the soft-shelled turtle, just like the high endothelial venule, was the important passage of the lymphocytes and blood cells going out and into the lymph tissue. The splenic circulation in the turtle belongs to the opening model.

Key words: Spleen, Ellipsoid, Circulation, Transmission electron microscopy, EM>Pelodiseus sinensis/EM>