Features include chaetae (spines) restricted to the ventral surface and a large pharynx (part of the feeding system).
I'm not sure of the anatomy but I believe the pharynx is the space immediately behind the mouth, followed by what looks like a very narrow tube leading the the large sac-like 'stomach' with food in the posterior half.
In a large dish these worms appear as one continuous worm; put them on a microscope slide under a coverglass and they start to break up into 2 or 3 pieces each of which appears to be alive.
Olympus BHS DIC 10x S Plan Apo, 1.25x intermediate tube, 2.5x NFK relay lens, flash, single frame.

NUM10118