80 



Tlie otlier laig-e vessel arisino- from tlie posterior aorta 

 is the Adductor Artery (fig. 14, A. add.). This leaves the 

 aorta at a right angle, and plunges into the adductor 

 muscle immediately in front of the deep cleft dividing the 

 striped muscle from the unstriped. On entering the 

 muscle, small vessels are given off from its posterior side, 

 which pass out of the main bundle of striped muscle and, 

 crossing the cleft, enter and supply the unstriped portion. 

 The mail] artery, however, passes down towards the middle 

 of the addiictor, where it divides, sending branches in all 

 directions. The figure shows the course taken in one of 

 the specimens where the injection mass went very 

 sviecessfully, but probably here, as in other places, there 

 is great variation in the smaller branches. 



The Yexous System (tig. 1(S) consists largely of 

 sinuses, and contrasts thereby with the fine arterial 

 vessels. There are three main sinuses situated between 

 the adductor muscle and its connective tissue sheath, 

 which account for the large outflow of blood when the 

 muscle is cut from a valve. 



A large Dorsal Sinus (fig. IcS, ;S'. D.) is situated under 

 the pericardium and digestive gland; anteriorly, this 

 communicates on both sides with the renal organs. On 

 the ventral side of the adduct(u", there are two sinuses, 

 which extend from the cleft dividing the striped and 

 unstriped portions of the muscle up to the renal organs. 

 They are continued under these and the visceral mass, and 

 communicate with one another. The main opening of 

 these sinuses to the renal organ is at the dorsal end, and 

 by slitting up the outer surface, the renal veins may be 

 seen branching and becoming much smaller as they pass 

 from the pericardial end towards the reno-genital opening 

 (fig. 12, Ro. 7:). 



A large Hepatic vein (fig. 18, 1'. A.) on each side of 



