vii MOLLUSGATHE PALLIAL COMPLEX 75 



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



s 



7 



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

 respiratory aperture, pi? ; s, shell ; p, edge of shell aperture ; </, genital aperture ; t lt optic tentacle ; 

 t, anterior tentacle ; ?o, 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 (Pln- 

 orbis, Physa, Limnaeus), near the respira- 

 tory aperture, and among the Stt/lommato- 

 phora in Tcstticella 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 (ulu>iusoblongus,a.nd some species 

 of Planorbis) (Fig. 73 A). 



2. The papilla lengthens and runs for- 

 ward as a straight ureter (primary ureter). 



FK;. 73. Six diagrams illustrating the 

 variations in the renal ducts in the Pul- 

 monata. The organs are supposed to he seen 

 through the mantle above them. 1, Free edge 

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



This occurs inmost Basommatophora, and 4 - kidney; 5, pericardium; 6, auricle; 7, ven- 

 tricle ; 8, primary urinary duct ; 0, secondary 

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



explanations found in the text. 



some species of Bulimus, Gionella, Pupa, 

 Helix (B). 



3. The ureter runs backward along the 



kidney, and opens at the base of the respiratory cavity. Testacclla, and some forms 

 of Helix (C). 



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



