The hemocytes of the tunicate Halocynthia roretzi are classified into six types based on their size, cellular form, and fine structure of the cytoplasmic granules: hyalinocytes, granulocytes, phagocytes, nephrocytes, morula cells, and multi-vacuole cells. Based on cell size, they are ordered multi-vacuole cells ($7.5{mu}m$)>nephrocytes ($7.1{mu}m$)>phagocytes ($6.8{mu}m$)>granulocytes ($6.1{mu}m$)>morula cells ($5.7{mu}m$)>hyalinocytes ($5.4{mu}m$). The proportion of hemocytes is ranked in the order multi-vacuole cells (54.8%)>nephrocytes (16.9%)>granulocytes (9.9%)>morula cells (8.8%)>phagocytes (6.1%)>hyalinocytes (3.5%).