The digestive tract of Phoronids consists of a short oesophagus which leads into a spherical stomach and then into the intestines which end in the anus. Phoronids have a simple blood system of one descending artery and ascending vein linked by a network of fine capillaries. There are also blood vessels into each of the tentacles. The blood is colourless but contains corpuscles with a haemoglobin-like pigment that helps to carry oxygen.