164 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



The other two renal sacs, the posterior sacs, lie at the .sides of the body, widely separated 

 from each other. A little posterior to the inner sacs, they are considerably outside them, to close 

 the ventral sides of the shell muscles. 



The dorsal wall of each sac is formed by the inner wall of the mantle fold, and is that 

 portion of the inner wall of the mantle fold lying between the anterior renal pores and the base 

 of the posterior gill. The posterior and anterior walls of the sac are formed by septa extending 

 backward and downward from the inner wall of the mantle. They unite around the lobular 

 appendages to form a closed sac, from the posterior edge of which a thin ligament extends back- 

 ward and somewhat inward, attached along one edge to the visceral body wall. (Fig. 36, L.) The 

 outer end of the sac is narrowed to form a canal which, running in the substance of the mantle 



vc 



RG PO 



RSA I BVAl 



Text-pig. 9.- 



-DIAGRAM OF THE RENAL SACS AND NEIGHBORING ORGANS OF NAUTILUS, AS 

 VIEWED FROM THE DORSAL SIDE. 



AC, auricular expansion of left anterior branchial vein. 



BAA, anterior branchial artery. 



BAP, posterior branchial artery. 



BVA, anterior branchial vein. 



BVP, posterior branchial vein. 



H, heart. 



PGA, anterior pericardial appendage. 



PGP, posterior pericardial appendage. 



PO, pericardial pore. 



RG, anterior renal appendage. 



ROA, anterior renal pore. 



ROP, posterior renal pore. 



RSA, anterior renal sac. 



RSP, posterior renal sac. 



VC, vena cava. 



X, outline of pericardial division of cceloni. 



Y, cul de sac of anterior renal sac. 



close to the ventral surface of the shell muscle outside and ventral to the branchial artery, opens 

 to the exterior through one of the posterior renal pores. (Fig. 3, RP.) The posterior branchial 

 arteries run through the posterior walls of the outer renal sacs. (Text-fig. 9, BAP.) 



Between the inner and outer renal sacs is left a narrow offset of the pericardial cavity 

 extending into the mantle fold. The auricular enlargements of the anterior branchial veins lie 

 in this space. From the outer end of the enlarged auricular portion of the vein where it turns 

 upward to pass through the inner wall of the mantle fold, a triangular septum stretched between 

 the outer and inner walls of the mantle fold extends outward to the lateral edge of the pericardial 

 space. By this means a narrow passage is formed between the anterior side of the outer renal 

 sac and the septum. This passage, passing along the outer side of the anterior branchial vein, 

 opens to the exterior through the pericardial pore. (Fig. 3, PP.) 



