In the video the worm projects a slimy net onto the man’s hand!
Believe It or Not, that web is part of the worms’ body!
It’s called a proboscis and the worm keeps that inside its body until it forcefully squeezes out the appendage to catch small animal prey.
Kyle Hill from the Nerdist Blog explains:
But what sets ribbon worms apart from all other worms is their namesake proboscis. This feeding appendage is held in a sheath or sac above a ribbon worm’s gut. When prey is detected, muscles rapidly contract and force fluid into the sheath, which turns the proboscis inside-out and forces it through the proboscis pore at the head of the worm. It wraps around prey and is then drawn in for a meal. In some species the proboscis can extend out 30 times the length the worm.