In each segment (metamere) of the being a pair of complete excretory structures called metanephridium exists. The metanephridium has an extremity, the nephrostoma, which collects residuals from the coelom, filtering them and causing reabsorption along its extension (similar to human nephron tubules). The material to be excreted goes out through a pore, the nephridiopore, which opens in the body surface.
