THE STARFISH 



123 



Find the connection between them. Observe the specimen 

 which is injected with coloring matter. Near the base of 

 the ray on each side are the reproductive bodies. 



(5) Cut along the sides of the two rays lying on either 

 side of the first ray cut, and extend the opening nearly across 

 the disk, being careful not to cut into the body parts. 

 Raise up the parts severed and find the membraneous 

 stomach. 



Pass the bristle in at the mouth and explore the interior. 



(6) Observe the lobes of the stomach. Do they extend 

 into the rays ? Lift one of the lobes and see if you can find 

 how the muscles are attached. Trace the liver toward the 

 stomach, do you find where the opening is ? 



(7) Do you find the anus on the top of the stomach next 

 the aboral side?- Remove the roof from the three rays and 

 make a drawing showing the organs exposed. 



(8) Remove the stomach by cutting across the esopha- 

 gus. This exposes the crooked S-shaped stone canal ex- 

 tending downward from the madreporic body. Trace this 

 canal to its lower end and find that it forms a ring — the 

 circum-oral water ring — which conveys the water from the 

 madreporic body to the ampullae and thence to the am- 

 bulacral feet. This system of circulation is the water vas- 

 cular system. 



(9) Cut across a ray in two places about an inch apart 

 and notice all that is included in the part thus cut out. 

 Remove the liver, noting how it was attached to the body 

 wall. 



Notice the part through which the ambulacral feet ex- 

 tend. 



Probe with a needle the middle portion of the ambulacral 



