64 



This, however, is not the only path for blood 

 entering the renal organ. We have already seen that a 

 large vessel runs round the margin (fig. 37, lam. v.). 

 From this vessel branches arise which run across in the 

 plane of the outer surface and divide up close to this 

 surface. The system of anastomosing channels is 

 extremely complicated, and minute, and finally all 

 is resolved into two outgoing paths. One of these 

 is seen right on the surface when the renal organ 

 is injected, and is shown in fig. 35. It consists of 

 delicate vessels running almost at right angles to 

 the left margin (fig. 35). These delicate vessels 

 enter a large lymph-like gland, the nephridial gland, 

 which extends along the side of the renal organ against 

 the pericardium. It was supposed that the nephridial 

 gland communicated only with the auricle and that blood 

 passed to it by means of the nephridio-cardiac vein and 

 back again by the same course. A detailed study of this 

 point in the whelk has clearly shown that there is a direct 

 path from the renal organ through the nephridial gland 

 to the heart. The other path is more internal and is 

 made up of another series of small vessels which open into 

 the reno mucous vessel running along the right side of the 

 renal organ (fig. 38). Thus there are two lines of com- 

 munication bringing blood to the renal organ and two 

 paths along which blood leaves. 



Blood Circulation in Pallial Complex. 



The blood from the " kidney " which pours into the 

 reno-mucous vessel passes forwards into that part of the 

 latter bounding the mucous gland. Blood from the rectal 

 region and mantle also enters this vessel, and from it 

 passes through the mucous gland to the afferent 

 branchial vessel. The mucous gland is exceptionally 



