MOLLUSGA—THE NEPHRIDIA 



223 



the apex of the visceral dome on tlie anterior side of the paired renal sacs {cf. Fig. 

 177, p. 213). The veins returning from the body to the heart run in the partition 

 between the unpaired anterior and the paired posterior sacs, and may here bulge out 

 to form venous appendages, not only posteriorly, i.e. into tlie cavities of the two 

 paired renal sacs, but also anteriorly, into that of the unpaired connecting sac. Near 



Fig. 185.— Renal sac, coelom, genital organs, etc., of Sepia. A, female ; B, male. The 

 visceral dome is seen from behind ; the mantle, the body wall, the ink-bag, and in A the hind-gut 

 and the nidamental gland are removed (after Grobben). a, Heart ; 1>, genital vein ; c, genital 

 artery ; d, stomach ; c, female germinal body ; /, ajierture of the oviduct in the ovarial cavity ; 

 g, oviduct ; h, unpaired anterior renal sac ; i, abdominal vein ; k, appendage of the branchial 

 heart (pericardial gland); I, branchial heart; m, paired posterior renal sac; n, gill; o, canals of 

 the cojloni leading to the kidneys ; p, gland of the oviduct ; q, female genital aperture ; r, renal 

 aperture. In B, 1, testes ; 2 (the indicator points rather beyond the right place), aperture of the 

 male germinal body into the genital cavity or capsule ; /, aperture of the seminal duct into the 

 male genital capsule ; 3, section of the coelom containing the vas deferens (peritoneal sac) ; 5, anus ; 

 6, rectum ; q, male genital aperture. 



the point where each renal sac is produced into the ureter, the reno-pericardial canal 

 springs from it, opening into the secondary body cavity which contains the heart, 

 and corresponds with the pericardium of other Molluscs. 



The form of the renal sac is at least partly determined by the form and position 

 of the surrounding viscera, the stage of maturity of tlie genital organs, and the 

 different shape of these organs in the two sexes. All viscera which press against the 

 renal wall from Avithout, bulging it inward, are naturally covered at the points of 



