The ribbon worm are cylindrical to somewhat flattened, highly contractile, soft-bodied, unsegmented worms. Most of them are small, but a
few attain considerable size and may grow in excess of 20 ft. (6 m). Usually they are very slender and brightly colored.
These animals are secretive, burrowing in sand and living in algal clumps or mats or in oyster shells.
Some ribbon worms have an unusual anterior proboscis equipped with a sharp spine that is used to capture prey. In some species
this also injects a slightly toxic secretion that may cause swelling and temporary pain.
Nemertines have sexual reproduction; they may also reproduce asexually by fragmentation. The worms break easily when handled, and the
separte parts may regenerate lost parts and form new complete individuals.
Ribbon worms are very common in the sea, dwelling from the shore to the greatest depth of the ocean trenches. Most require microscopic examination
for identification; however, a few are recognizable by their size and color.
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