DIGESTIVE SYSTEM. 119 



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 hloivpipe. Insert a seeker 

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

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

 the mantle-cavity, and then forwards close alongside the 

 kidney to-its anterior end, into ivhich 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 7'ectum from the anus, 

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

 tory and renal apertures. 



III. DISSECTION OF THE DIGESTIVE SYSTEM. 



Cut away the part of the collar to the left of the pul- 

 monary aperture. Detach the right side of the collar, with 

 the anal aperture, from the body-wall. Separate the rectum 

 from the body by cutting along the right side of the mantle, 

 just below the rectum, as far hack as the hinder end of the 

 mantle-cavity. Turn the rectum hack, and pin it down. 



Make a median longitudinal incision through the floor of 

 the mantle-cavity, and continue it forwards along the head to 

 its anterior end. Dissect the'flaps away from the underlying 

 parts, and pin them out right and left. 



Carefully remove the thin skin covering the spiral visceral 

 mass ; and unravel the reproductive organs, which are white 

 in colour and very bulky, and the alimentary canal, the coils 

 of which are very intimately connected ivith the liver. 



Arrange the reproductive organs on the right, the digestive 

 organs on the left side of the dissection. 



The removal of the integxoment from the visceral mass 

 requires care, but presents no great difficulty. Special care 

 is needed at the posterior end of the mantle-cavity, ivhere the 

 parts a/re rather firmly hound together. 



