Abstract
Cells of the freshwater nannoplankton flagellate Chrysococcus rufescens Klebs (Chrysophyceae or Chrysomonadida) were isolated from a pool in the English Lake District and the clonal cultures established were used for a morphological investigation by light and electron microscopy. A novel feature was a system of flattened sacs and tubules just below the cell surface, possibly connected with the formation of the thick fibrous lorica. The structure and disposition of the main organelles however resembled those of other members of the Chrysophyceae investigated.