- 1 The primary function of the flagellum in a monoflagellate organism is to produce both rotation and gyration of the organism about a certain axis which constitutes the main direction in which the organism is swimming.
- 2 The mechanical principle by which the organism is propelled is simply that of the inclined plane which is caused to rotate. In other words it is that of the screw or propeller.
- 3 Since the disturbances or waves pass down the flagellum in the form of a spiral they produce two distinct components. It is the resultant of these two components which causes the tip of the organism both to rotate and gyrate.
- 4 So long as this rotation and gyration is maintained it will supply the necessary force for the propulsion of the organism.
- 5 The flagellum itself may or may not produce a forward component. If it is more or less swung out at right angles, as in Menoidium, it will produce no forward component but if it is swung back, as in Euglena, it will do so.
- 6 A large amount of gyration would be normally a disadvantage to the propulsion of the organism. One way of reducing gyration would be to increase the number of flagella.
- 7 There is no evidence that the waves or impulses ever start at the tip of the flagellum and thus constitute a tractellum.