Mollusca is one of the largest phyla of animals in number of living species and in individuals. Mollusks have a coelom, which is a significant characteristic that develops in the medosperm. The mesoderm is the middle germ layer of an animal embryo, giving rise to muscle, blood, bone, connective tissue. All mollusks have a soft body (their name is derived from the Latin word mollus, meaning "soft"), which is generally protected by a hard, calcium-
containing shell. Mollusks are quite distinct from other organisms in other structures. They are bilaterrally symmetrical and have guts with mouths and anuses.
containing shell. Mollusks are quite distinct from other organisms in other structures. They are bilaterrally symmetrical and have guts with mouths and anuses.