Descriptive Zoology. 



the oral surface, especially along the borders of the 

 grooves on the oral surfaces of the rays, are movable 

 spines attached to the ossicles of the body wall. 



On the aboral surface are many small pinchers, consist- 

 ing of a short stalk bearing two calcareous blades. The 



FIG. 188. COMMON STARFISH. 



stalks are flexible, and the blades of the pinchers may be 

 seen opening and closing. It is thought they are for the 

 purpose of keeping the body clean by picking up and re- 

 moving small particles. These pinchers are called pedi- 

 cellariae. 



The Water Tube System. Before we can understand 

 how the starfish locomotes we must get an idea of the 

 water tube system, or water vascular system, as it is usually 

 called. In the first place, an examination of a live starfish 

 will show the rows of soft, flexible, cylindric tube feet in 

 the grooves in the rays. By watching the live animal it 



