Most echinoderms develop via bilaterally symmetrical larvae.
A juvenile forms within the larval body as an imaginal rudiment. At metamorphosis the radially symmetrical juvenile reshapes, or resorbs, or casts off portions of the larval body. Development via a larva is indirect development because specialized non-adult morphologies and metamorphosis are used to reach the adult body plan. Few species of echinoderms lack larvae and undergo direct development. In direct development the adult body plan develops from the embryonic organization thus obviating metamorphosis.