Fig. 12. Graph summarizing hemolymph circulation through the forward (A,B) and backward beating heart (C,D). (A,C) Overview; (B,D) detail, showing the central location of the anterior heart and its strategically favourable connection to the venous channels (VC). The lateral thoracic hemolymph flows through these channels directly to the first ostia. During diastole of the backward beating heart, thoracic hemolymph enters these anterior ostia exclusively. During forward beating, hemolymph is aspired from the heart through all ostia, including the first ones. Thus a lateral circulation in the thorax is maintained independently of heartbeat direction. S, pericardial septum.