The group gets its name from the fact that they all possess flagellated cells at some stage of their life cycles, and the flagella are typically of two types. One type of flagellum is covered with thin, stiff hairs, and is usually directed into the direction of swimming. The other type is shorter, lacks the coating of stiff hairs, and is usually directed away from the direction of motion while swimming. The anterior flagellum is variously referred to as a tinsel, pleuronematic, of flimmer flagellum, while the thin hairs are called mastigonemes. It is this the presence of these two different flagella that give the division its name, the Heterokontophyta.