Polychaete eggs undergo spiral cleavage. Many develop into a free-swimming trochophore larva. This larva grows at the “growth zone” on the posterior end, by forming sequential serial segments in a process called teloblastic growth. After a period of larval elongation, the larvae settles from the plankton and becomes a juvenile worm. Other polychaetes undergo direct development (without a larval stage), or short, non-feeding trochophore stage (Brusca and Brusca 2003)