vii MOLLUSCATHE PALLIAL COMPLEX 75 



the pericardium, containing the ventricle and auricle, the latter lying in front of 



S 



7 



r, 



fffr, 



FIG. 72. Helix aspersa, fully extended from the right (after Howes), a, Anus appearing in the 

 respiratory aperture, pl- 2 ; s, shell ; p, edge of shell aperture ; ga, genital aperture ; ti, optic tentacle ; 

 t, anterior tentacle ; ?->, upper lip. 



the former. From the ventricle the aortic trunk runs upward and backward, and 

 from the auricle rises the pulmonary vein, 

 which runs forward along the roof of the 

 pulmonary cavity. 



4. The respiratory vascular network 

 spreads over the whole remaining surface 

 of the roof of the pulmonary cavity, and 

 is thus in front of the kidney and peri- 

 cardium. 



5. An osphradium has till now only 

 been found in the Basommatophora (Plan- 

 orbis, Physa, Limnaeus}, near the respira- 

 tory aperture, and among the Stylommato- 

 ph&ra in Testacella on the floor of the 

 pulmonary cavity at its extreme posterior 

 angle. 



The floor of the pulmonary cavity (the 

 dorsal nuchal integument) is smooth and 

 devoid of organs. 



The arrangement of the efferent ducts 

 of the renal organ varies and deserves 

 special description (Fig. 73). 



1. The anterior side of the renal sac 

 opens on a simple papilla in the mantle 



cavity (Bulimus oblongus, and some species 

 of Planorbis) (Fig. 73 A). 



2. The papilla lengthens and runs for- 

 ward as a straight ureter (primary ureter). 

 This occurs in most Basommatophora, and 

 some species of Eulimus, Cionella, Pupa, 

 Helix (B). 



3. The ureter runs backward along the 



kidney, and opens at the base of the respiratory cavity, 

 of Helix (C). 



4. A secondary urinary duct is added, becoming constricted from the wall of 



FIG. 73. Six diagrams illustrating the 

 variations in the renal ducts in the Pul- 

 monata. The organs are supposed to be seen 

 through the mantle above them. 1, Free edge 

 of mantle ; 2, respiratory aperture ; 3, rectum ; 

 4, kidney ; 5, pericardium ; 6, auricle ; 7, ven- 

 tricle; 8, primary urinary duct; 9, secondary 

 urinary duct, which, in D, is a groove. Further 

 explanations found in the text. 



Testacella, and some forms 



