The motion of Euglena viridis: the role of flagella.

A description of the movement of Euglena viridis has previously been published (Lowndes, 1941, 1944), but the present study has yielded additional information, particularly concerning the flagellar wave parameters. Although it is generally accepted that the flagella of such organisms as spermatozoa are directly responsible for propelling the organism through its liquid environment, it has been suggested by Lowndes (1944, 1945) that the flagella of certain organisms, e.g. E. viridis and Monas stigmatica, are only indirectly responsible for the movement of the organism. Lowndes considers that the flagellum causes rotation and gyration of the organism's body which thus acts as a rotating inclined plane and produces the main propulsive thrust. Experiments with model organisms have been carried out by Lowndes (1944) and Brown (1945) to test the feasibility of such a system and they conclude that gyrating organisms could propel themselves by body movement alone although the flagellum might also provide some forward thrust. More recent observations (Bovee, Jahn, Fonseca & Landman, 1963) suggest that the body gyrations of Mastigamoeba contribute to the propulsive force. In the present paper the movement of E. viridis is analysed experimentally and also theoretically using equations developed by the method of Gray & Hancock (1955) and the propulsive effects of body gyration and flagellar undulation are compared.