A worm's excretory system is different because it has excretory organs in almost every segment of its body. The system is made up of coiled tubes called nephridia that open into the body cavity.
Each segment feeds into a main tube called the nephridiostome, which then carries the waste outside the body once all the useful nutrients are removed from the fluids and passed along the body to the end. The excretory system does dual duty to remove waste and to function as a kidney. The canals which make up another part of the system excrete a saline like solution to maintain the salt balance of the worms body.