The Nemertini are mostly bottom-dwelling marine organisms, although some are found in freshwater and terrestrial habitats.
Most nemerteans are carnivores, some are scavengers, and others have evolved relationships with some mollusks that are benefit the Nemertean but do not harm the mollusk.
Nemerteans vary greatly in size and are bilaterally symmetrical; they are unsegmented and resemble a flat tube which can change morphological presentation in response to environmental cues.
Nemertini have a simple nervous system comprised of a ring of four nerve masses called "ganglia" at the anterior end between the mouth and the foregut from which paired longitudinal nerve cords emerge and extend to the posterior end.