The pellicular structure of Euglena gracilis consists of a series of relatively rigid strips (Fig. 1) composed of ridges and grooves which are helically oriented along the cell and which fuse together into a common junction at either end of the cell. The strips are predominantly protein and consist in part of a series of fibers about 50 Å in diameter spaced about 85 Å apart and with a secondary periodicity of about 450 Å. Microtubules are also present below each strip (Fig. 1) and are often considered as part of the pellicular complex. In addition, there may be another fibrous component near the base of the pellicle which has not yet been very well defined.The pellicular complex lies underneath the plasma membrane and entirely within the cell (Fig. 1). Each strip of the complex forms an overlapping junction with the adjacent strip along one side of each groove (Fig. 1), in such a way that a certain amount of sideways movement is possible between one strip and the next.
