Starting life as zooplankton, after several molts the juvenile barnacle lands and glues itself to a hard surface before changing to its adult form. A six part cone shaped shell is excreted over the soft body, while six pairs of larval legs become cirri, a fan-like structure that waves in the currents, pulling plankton to consume. Like other crustaceans, barnacles grow by molting. However, they do not cast off their shell. The covering of the soft inner body is replaced and the outer shell enlarges to accommodate it.