Solenocytes are the main excretory structures in

Solenocytes (also called flame cells) are meant for excretion and osmoregulation in Platyhelminthes. Annelids have metanephridia for excretion. Molluscs have kidneys (although different from vertebrate kidneys) for excretion. In echinodermates, no special excretory organs are found for excretion. In them, excretion takes place through diffusion or osmosis or through active transport.