A flame cell is a specialized excretory cell found in flatworms (except the turbellarian order Acoela), rotifers and nemerteans. Flame cells function like a kidney, removing waste materials.
The nephridium is an invertebrate organ that occurs in pairs and performs a function similar to the vertebrate kidney. Nephridia remove metabolic wastes from an animal's body.
The malpighian tubule is a tubular excretory organ, numbers of which open into the gut in insects and some other arthropods.
Green glands are excretory organs in Crustaceans.