Give scientific reasons :
The blood vascular system of leeches is also called haemocoelomic system. 

Explanation

In leeches there is no true blood vascular system has coelomic space and fluid have been modified to form the circulatory system. Hence it is called haemocoelomic system and the coelomic fluid is called haemocoelomic fluid. Blood is red due to the presence of respiratory pigment haemoglobin or erythrocruorin found dissolved in plasma. Tree amoeboid blood corpuscles are present but there are no red blood corpuscles.