All animals can move parts of their bodies. The majority are also capable of locomotion—movement of the whole body from place to place. Many simple animals, such as rotifers and flatworms, move with the help of microscopic hairlike structures called cilia.
These beat in a coordinated way, propelling the animal through water or making it glide over solid surfaces at the rate of a few inches an hour. Another form of creeping movement, seen in earthworms, involves changes in body shape. The worm's segments extend and contract in a set sequence, allowing it to force its way through the surrounding soil.
Some of the earthworm's relatives have flaps called parapodia that help them to move, but even with these, their speed is fairly modest. With a few notable exceptions—such as squid and octopuses, which can move by a form of jet propulsion—the fastest animals by far are ones that have skeletons and jointed limbs.