Structural Changes in Tetrahymena rostrata during Induced Encystment*

SYNOPSIS. Experimentally induced precystic stages and mature cysts from 3 clones of Tetrahymena rostrata were examined by light and electron microscopy. It was demonstrated by cytochemical staining and fine‐structural observations that precystic stages release mucocyst material that provides for the production of a cyst wall. Early and late cysts also contain numerous autophagous vacuoles. In late cysts there is a replacement of depleted mucocyst organelles. The developmental evidence obtained from sampling of sequential developmental stages suggests an ∼24‐h timetable of cytoplasmic events associated with encystment in this organism.