MANTLE-CAVITY 111 



Slit open the kidney longitudinally : wash it out with a 

 gentle stream of water, and note its structure. 



b, The ureter is a thin-walled duct which commences 

 at the proximal end of the kidney and runs back 

 along its right side to the distal end. It then 

 turns sharply forwards, and runs along the right 

 side of the mantle-cavity to its anterior end, 

 lying dorsal to the rectum, and just within the 

 prominent ridge-like fold that marks the junction 

 of the roof and right side of the mantle-cavity. 



In front it opens into the mantle-cavity imme- 

 diately above and to the right of the pulmonary 

 aperture. The opening is slit-like, and is con- 

 tinued as two divergent grooves with prominent 

 lips, which run down the right and left sides of 

 the pulmonary aperture, the right groove being 

 continuous below with the spout-like groove of 

 the rectum. 



Insert one blade of a pair of scissors into the pulmonary 

 aperture from the outside, and cut through the collar, keeping 

 close to the left side of the aperture. Turn the right lip of 

 the aperture over to the right side. Pass a seeker into the 

 rectum from the anus so as to identify it. Note the ureter 

 running along the right side of the rectum, but dorsal to it in 

 the natural position of the parts. Trace the ureter forwards 

 to its opening, and inflate it with a blowpipe. Insert a seeker 

 into the opening; and, using it as a guide, slit up the ureter 

 along its whole length, following it back to the hinder end of 

 the mantle-cavity, and then forwards close alongside the kidney 

 to its anterior end, into which it opens. 



3. The rectum is a wide tube running along the right side 

 of the mantle -cavity, ventral to the ureter. It opens 

 in front at the anus, which has already been seen. 



Insert a bristle or seeker into the rectum from the anus, 

 and note carefully the relations of the anus and the respira- 

 tory and renal apertures. 



