pilidium

Meanings

1. The free-swimming larva of certain proboscis worms, somewhat resembling a deerstalker hat. It has no resemblance to its parent, and the young worm undergoes development in its interior.

Etymology

From Ancient Greek πῑλίδιον (pīlídion, “little cap”), diminutive of πῖλος (pîlos), probably influenced by other formations in -idium, like miracidium, planidium, and coracidium.