Answer:
Animal locomotion is accomplished through the force of muscles acting on a rigid skeletal system. There are three types of skeletal systems in the animal kingdom: hydraulic
skeletons,
exoskeletons
and endoskeletons.
Hydrostatic skeletons are primarily found in soft bodied invertebrates such as earthworms and jellyfish.As the muscles contract, the fluid in the cavity moves and
changes the shape of the cavity. In an earthworm, for example,a wave of contractions of circular muscles begins anteriorly and compresses each segment of the body, so that the fluid pressure pushes it forward. Contractions of
longitudinal muscles then pull the rear of the body forward.
whereas,in snails and slugs there is present the muscular foot.when there is need to move,animal produces the wave like contractions and relaxations and animal can move.