Most of the adults have radial symmetry. If they are not sessile or attached, they are at least benthic (bottom-dwellers). In contrast, echinoderm larvae are planktonic, and have bilateral symmetry. Echinoderm larvae are ciliated free-swimming organisms that have a bilaterally symmetry rather like embryonic chordates. The first stage in all groups except the crinoids is the dipleurula, which has a row of cilia winding round its body. All the groups have second and third stage larvae. The larvae grow, and are carried away from their parents.