The short, threadlike structures that extend from the cell membrane of animal-like protists are called cilia.

Here's why:

* Cilia: These are hair-like structures that beat in a coordinated rhythm, propelling the protist through its environment. They are much shorter and more numerous than flagella.

* Flagella: These are longer, whip-like structures that also aid in movement, but are typically present in fewer numbers.

Animal-like protists, also known as protozoans, use cilia and flagella for locomotion, feeding, and sensory perception.