156 PRACTICAL ZOOLOGY. 



and the entrance of their common duct into the 

 stomach. Observe the place where this tube enters 

 the stomach, in reference to the corresponding lobe 

 of the latter. 



Carefully cut the mesentery along the aboral wall 

 and wholly free the caeca of this ray from all attach- 

 ment above. Note that the mesentery is double. 

 9. Hold the starfish inverted and pour water through 

 the mouth into the stomach to show its shape. 



10. In the other two rays which have been opened, cut 

 across the common ducts of the caeca close to the 

 stomach, and leave them attached to the aboral walls. 



11. Find the extremely short intestine connecting the 

 stomach with the upper wall of the disk, near the 

 junction of the extensor muscles of the rays. Find, 

 also, some small branched appendages of the intestine. 

 The anal opening is minute. 



12. Sever the intestine close to the aboral wall, cut across 

 the disk close to the madreporic body, and remove 

 entirely the roof of the disk and the three rays. 



Make a drawing of the organs now exposed, show- 

 ing the caeca in one ray, the reproductive bodies in 

 another, and the ampullae in the third. 



13. Thoroughly examine the stomach, and remove it after 

 cutting across the short esophagus. 



14. The S-shaped stone canal may now be seen passing 

 downward from beneath the madreporic body. 



15. Traced to its lower end, the stone canal may be found 

 to enter a membranous hollow ring, whose outer bor- 

 der rests against the inner surface of the hard parts 

 surrounding the mouth ; this tube is the circum-oral 

 water-ring. Connected with its inner, surface, find 



