The stiff outer membrane in euglena and paramecium is called the pellicle.

Here's why:

* Euglena: Euglena have a flexible pellicle made of protein strips that run longitudinally under the cell membrane. This allows them to change shape for movement, but it still provides structural support.

* Paramecium: Paramecium have a more rigid pellicle composed of protein plates that interlock. This structure provides more structural support and a defined shape for the organism.

While both organisms have a pellicle, their structures and functions differ slightly due to their different modes of movement.