Blood vascular system in Herdmania

The circulatory system of Herdmania is well d eveloped and greatly modified. It includes (i) Heart and pericardium (ii) Blood and (iii) Blood vessels. Pericardium is non-contractile, running obliquely below the right gonad and transparent tube. It is closed at the both ends and filled with pericardial fluid. Heart is enclosed with in the pericardium. Blood is slightly redish, transparent and hypertonic to sea water.