THE DINOFLAGELLATE PELLICULAR WALL LAYER AND ITS OCCURRENCE IN THE DIVISION PYRRHOPHYTA1

Forty-five species of dinoflagellates were surveyed for the presence of a pellicular layer in the amphiesma or cell covering. Such a layer was found in 15 of the 20 genera studied. Half the pellicles tested were resistant to acetolysis and may contain a sporopollenin-like material similar to that of some dinoflagellate cyst walk. Most organisms which formed pellicles were capable of reinforcing this layer with cellulose. Pellicles of Heterocapsa niei (Loeblich) Morrill & Loeblich and Scrippsiella trochoidea (Stein) Loeblich were studied with the electron microscope. Evidence is presented indicating that dividing cells of S. trochoidea from new walls while still enclosed in the parental pellicular layer.