pilidium

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

pilidium (plural pilidia)

1. (zoology) 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.

• pileus
• pilidial

• “pilidium”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.

pilidium m (invariable)

1. (zoology) pelagic larva of certain nemertean worms