The larva swims freely,leads a plantonic life feeding on minute organisms, and metamorphoses into an adult worm. During metamorphosis, the size is reduced probably due to loss of water. Transparency, ciliary bands, sensory cilia and eye spots are lost. Body becomes differentiated into roboscis,collar and trunk by the aearance of two constrictions, and the trunk region is elongetedd. The hydroore ersists as proboscis pore, and the buccal diverticulum and gill-slits appear as outgrowths of the alimentary canal. The animal now sinks to the bottom to lead a benthonic life as an adult.
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