Q.Locomotion in Echinodermata is chiefly brought about by

An exclusively marine phylum with a spiny, calcareous endoskeleton of ossicles just beneath the skin. Adults are radially symmetrical, but the free-swimming larvae are bilaterally symmetrical, showing that adult radial symmetry here is secondarily acquired rather than primitive (unlike Coelenterata). The phylum's defining organ system is the water vascular system, a network of water-filled canals that hydraulically operates external tube feet used for l …