STAEFISH 115 



note that the various rays and the multitude of 

 ambulacral feet all move in such a way as to 

 attain a common object. Study also the co- 

 ordinated movements by which a starfish rights 

 itself after having been overturned. "Where 

 does the righting movement begin? Does it 

 ever begin on opposite sides of the body at the 

 same time? Overturn the same animal repeat- 

 edly and see if the righting movements always 

 begin on the same side of the body. With a 

 pair of scissors remove one or more of the rays 

 from the body of a vigorous starfish and put the 

 parts back into the water. Does this treatment 

 kill the starfish ? Have the detached rays or the 

 body lost their powers of motion, sensation, co- 

 ordination, etc. ? What is the direction of the 

 motion of a detached ray? Of the body with 

 the remaining rays ? How do yoa explain this ? 

 Find a specimen which is progressing in a defi- 

 nite direction, and prick the skin on that side 

 of the body towards the point to which the an- 

 imal is going. Does the animal change its 

 course ? 



D. Reproduction. 



I. Regeneration of lost portions of the hody. — With a 

 pair of scissors or a sharp knife remove one of the 

 rays close to the disk. Place the parts back into 

 the water and study their behavior. What takes 

 place at that part of the disk where the ray was 

 removed ? Watch the mutilated parts from day 

 to day to see what changes are going on at the 

 point of injury. How long before the opening 

 into the body-cavity caused .by the removal of the 



