Page "Echiura" Paragraph 8

Although some species lack a blood vascular system, where it is present, it resembles that of other annelids.

The blood is essentially colourless, although some haemoglobin-containing cells are present in the coelomic fluid of the main body cavity.

There can be anything from one to over a hundred metanephridia for excreting nitrogenous waste, which typically open near the anterior end of the animal.