The head is not readily distinguishable from the body, which is flattened and gradually tapers towards the tail, where there is a slender caudal cirrus.

[3] The proboscis is everted (turned inside out) and the lower half of the Atlantic jackknife clam (Ensis directus) is enveloped.

Reproduction can also occur by fragmentation, as this worm readily breaks into pieces which can grow into new organisms.

[1] Cerebratulus lacteus produces several homologous polypeptide cytotoxins that are active in breaking down the membranes of human red blood cells, as well as several neurotoxins.

Because Cerebratulus lacteus is a threat to such activities, research is ongoing into the ribbonworm and what governs its patchy distribution, with a view to being able to better control it.