Glycogen and degeneration in the pyloric gland of Dendrodoa grossularia (Ascidiacea, Tunicata).

Degeneration is observed in cells of the pyloric gland of Dendrodoa grossularia in which glycogen storage occurs. The ultrastructure of four phases of the degeneration cycle is described. Natural senescence seems to be the cause of the degeneration. Glycogen storage might be the result of metabolic disturbance, but its presence reveals the importance of glycogen in the function of the organ. The role of the pyloric gland is discussed.