Inorganic corpuscles like Indian ink and latex particles as well as erythrocytes penetrate via stomata on the peritoneal surface of the diaphragm into the subperitoneal lymphatics when injected intraperitoneally. Electronmicroscopic examinations showed that stomata are formed by intercellular gaps between neighbouring mesothelial and endothelial cells. In these areas there is a lacunar dilatation of the lymphatics, and a basement membrane as well as collagenous fibres are absent. The back flow of the lymph fluid from the stomata into the peritoneal cavity is prevented by overlapping of mesothelial and endothelial cells during inspiration as well as valve like cell processes of endothelial cells. The lymph flow is particularly affected by anchoring filaments of the lymphatics and the respiratory movement of the diaphragm.