Fig. 1

Section of a scanning electron micrograph of a deciliated P. tetraurelia cell showing the cortical units that cover the cell surface. Rows of cortical units run between the anterior and posterior poles. One or two basal bodies are in each unit but cannot be seen here. The small structures (arrow) in some of the units are stubs of cilia, which break off at the transition zone during deciliation. Anterior is to the left. Scale bar is 4 μm