Fine structure and presumed functions of the gastric hemal tufts of the Asteroid, Asterias rubens L.

Asteroid gastric hemal tufts are paired mesenteric-like organs containing enlarged hemal lacunae. They connect the gut hemal system to that of the gonad through the upper part of the axial organ. Gastric tufts are covered by an heavily folded mesothelium in which microscopic pores occur. Tuft lacunae contains a finely granular ground substance (the hemal fluid) in which two cell types are seen. It is suggested that the gastric tufts are Kemal fluid-collector organs and that they could also function as hemal fluid-filtering organs.