122 COELENTERATES 



Alcoholic Specimen. — (i) Briefly review the points 

 noticed in tlie dried specimen. Notice especially the ar- 

 rangement of the spines on the oral side, and the ambu- 

 lacral feet, in the furrow. Observe the arrangement, size 

 and attachment. Note the arrangement of spines around the 

 mouth. 



(2) Compare the spines of different areas as to size, 

 shape and degree of flexibility. Look around the spines 

 for a ring of small projections. These are the pedicellariae. 

 Remove one and put it under a microscope. Find a stalk 

 bearing pincherlike parts for grasping. 



These are used to clean the spines and remove foreign 

 matter from the body. Make drawing. 



(3) Press apart the ambulacral or tube feet and exam- 

 ine the opening, and if a yellowish line is found it is the 

 nerve cord. Trace it back toward the disk and find a 

 nerve ring surrounding the mouth. Look in one of the 

 other rays to see if it is present in all. Follow the nerve 

 to the end of the ray and find the eye at the end. Draw 

 nervous system. The eye spot is borne on a distinct plate. 

 Draw oral side. 



(4) The arm opposite the madreporic body is the anterior 

 ray. Cut through the aboral wall near the outer end with 

 scalpel, and from this point cut with scissors toward the 

 disk about two inches. Raise the flap to see that you are 

 not injuring the internal organs and cut to the disk. The 

 branched body under the aboral side is the liver. Along 

 the middle line of the aboral wall is the extensor muscle — 

 a yellowish streak. Along the floor of the ray find little 

 sacs, (sometimes distended, but generally flat in alcoholic 

 specimens). These ampullae are the ambulacral vesicles. 



