Nemerteans are mostly marine but there are some freshwater and terrestrial species. They have a complete digestive tract with a mouth at one end and anus at the other and a closed circulatory system. Nemerteans are triploblastic, bilaterally symmetrical, and unsegmented worms. Most species are dioecious but asexual reproduction is common. Nemerteans have a unique feature called a proboscis, which is a long tube like structure on the head of the animal. The proboscis is used to capture prey. (Brusca et al., 2003, Kozloff, 2000)

References:

Brusca, R.C., and Brusca, G.J. (2003). Invertebrates. Library of Congress Catologing-in-Publication-Data: USA.

Kozloff, Eugene N. (2000). Seashore Life of the Northern Pacific Coast. University of Washington Press: Seattle and London.