The anatomy of Lucapina cremilata. 



459 





r g ^ pti .. i =M Tioi5Wfgm **»^ T 7^«rTTgT n rrrafj^saisiaaaigEgE: 



pressure of the liquids in the kidney, thus etïectually closing the open- 

 ing into the duct. Near the point where the genital duct leaves the 

 reproductive cavity is an opening into its posterior dorsal wall. This 

 opening, which is only a short slit in the wall of the oviduct, connects 

 with the pericardial cavity. It is difficult to homologise this arrange- 

 ment with that of the other molluscs. Apparently the morphological 

 relation of the parts has been turned around, the reno-pericardial 

 duct here opening into the genital duct, which in turn opens into the 

 right kidney. Thus the pericardial fluids enter the kidney only in- 

 directly through the genital duct. 



The reno-pericardial duct 

 leaves the pericardial cavity 

 on the right side (Fig. H 

 B.F) just behind the auricle. 

 The opening is between two 

 membranes, continuations of 

 the dorsal and ventral walls 

 of the pericardial cavity, 

 which are continuous with 

 the walls of the genital cavity 

 at this point. The epithehal 

 cells lining the reno-peri- 

 cardial duct are longer than 

 those of the cavities (Fig. H 

 c) and are provided with very 

 long ciha. This duct may 

 be very easily seen in dis- 

 secting and by taking a series Fig. H. Sections l, through one side of the 

 of sections through the region reno-iierleardial duct, 2 through the duct, c cilia, 

 nf thp Hurt (V\o- U\ T fnnnrl <?• ^^ genital duct, or oviduct, P. r pericardial cavity, 

 01 ine aUCl (^rig. n;, l lOUna ^ ,^ i-jgj^t nephridium, i?.P reno-pericardial duct, 



the epithelial membranes un- « position of shell. 



broken proving that the opening is a natural one. The duct is so 

 constructed that nothing from the genital cavity will pass into it. 

 The ventral wall at the outer end of the duct presses up against the 

 dorsal, thus closing the opening, but fluids from the pericardial cavity 

 are always free to pass out. 



The inner wall of the genital mass is closely attached to the 

 outer edges of the liver, it being difficult to separate them in the upper 

 part. This wall continues up past the Hver, and attaches to the 

 dorsal wall of the visceral cavity beneath the shell. The outer or 



