The Contractile Vacuole and Related Structures in Tetrahymena pyriformis*

SYNOPSIS. The nephridial system of T. pyriformis consists of a contractile vacuole with its two pores and an elaborate network of tubules. Both the vacuole and its tubules constitute a continuous system of single membranes of approximately 70 Å in thickness. Tubular fibrils of about 250 Å extend from the pore wall to the vacuole membrane and appear to function in dilating the pore prior to systole. The nephridial tubules arise directly from the wall of the vacuole and are continuous with it throughout the vacuolar cycle. The tubules appear to be contiguous with the granular endoplasmic reticulum. A typical Golgi complex was not found. Some speculation about the interrelation of these structures as regards function is offered.