230 OILMAN A. DREW. 



trally 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. 3, fa) leaves the aorta a short distance 

 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 portions 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. 2 and 

 3), there being numerous small branches that are given off 

 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 portions of the 

 reproductive organs. 



This completes what might be called the systemic arterial sys- 

 tem. Beginning with the heart the system ends in the capillary 

 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. i, bv], with a hypo- 

 dermic syringe, injecting toward the heart. If a starch mass that 

 will not pass through the capillary spaces is used, all of the ves- 

 sels 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. 



