passes ventrally and sends branches to the major part of the liver 

 and to the stomach. 



A short distance in front of the cartilage the anterior aorta 

 bends ventrally, passes through the liver and gives off a few 

 small branches to it, sends a vessel to the palps in passing, and 

 passes on to supply the foot and the visceral mass. The vessel 

 that supplies the foot (fig. 13, fa.) leaves the aorta a short dis- 

 tance ventral to the mouth, passes along the body wall until the 

 foot is reached and extends into the foot along its dorsal border. 

 Just before entering the foot this, the pedal artery, gives rise to 

 a small vessel that passes posteriorly along the single retractor 

 muscle of the foot supplying it with blood. From the point of 

 origin of the pedal artery the aorta extends into the visceral 

 mass following along the enlarged portion of the intestine that 

 leads away from the stomach, and supplying this and other por- 

 tions of the intestine and the reproductive organs with small and 

 with large branches. The enlarged portion of the intestine that 

 comes from the stomach is especially well supplied (compare 

 figs. 12 and 13), there being numerous small branches that are 

 given out directly from the aorta, and large branches that follow 

 along on the different sides of this portion of the intestine and 

 likewise supply it with branches. A short distance ventral to 

 the foot a large branch leaves the aorta and passes postero- 

 ventrally to divide again and form small branches that supply 

 the remaining loops of the intestine and the postero-ventral por- 

 tions of the reproductive organs. 



This completes what might be called the systemic arterial 

 system. Beginning with tbe heart the system ends in the capil- 

 lary spaces of the various organs. This system is most easily 

 injected through the vessel in the suspensory membrane 

 of the gills that is farthest from the adductor muscle, 

 (fig. II, bv.) with a hypodermic syringe, injecting toward 

 the heart. If a starch mass that will not pass through the 

 capillary spaces is used, all of the vessels thus far described will 

 be injected, as will also the veins that return blood from the 

 gills, as this vessel is the one that returns blood from the gills 

 to the heart. If a gelatin mass is used all of the systems may 

 be injected; but as the injecting mass may pass out of the spaces, 

 between the cells of the various organs, such injection does not 

 aid' in tracing the course of blood flow. 



38 



