. For example, when a snail moves, it is contracted by the longitudinal muscles of its feet. When it contracts to the highest peak, the sole of the foot is partially lifted off the ground, and then the longitudinal muscle spirals, and the lifted part falls back to the ground, so that it can move forward. Such contraction wave can be carried out in the local range of the foot, or it can occur in the whole length of the foot, or it can contract alternately from left to right. The contraction of longitudinal muscles pushes the body forward from the back, so the stretching wave is in the same direction as the movement wave. Some kinds stretch through the extensor muscles of the feet and then contract the transverse muscles to drag the body forward. This stretching wave is opposite to the direction of motion.
Some small species living in soft sand bottom can push their bodies forward through the cilia movement of their feet, such as snails and Lymnaea. Their feet are rich in glands or glandular cells, and their secretions form a film on the ground or plants, and then slide on the film by cilia movement, just like plane animals. Some species also make holes in the sand. When exercising, they form a plow or an anchor with bloodshot feet, and then drag their bodies forward, such as Terebra. There are also some aquatic hind gills that contract by the side of the body, or their feet swim in the water with their wings. Generally, the spiral part of the shell is low and flat, and the species attached to the rock are not good at sports;
Shells with high spiral parts parallel or inclined to the back are mostly sand-bottom life-style and are generally good at sports. Many marine species have spines, spines and other decorations on the shell surface to help fix the position of the body in the sediment. The primitive species also had a pair of columella muscles, which extended from the foot to the shell axis to control the expansion and contraction of the foot. However, most gastropods only keep one side of the columella muscle because of their body torsion.