136 S. J. HOLMES 



Strong light thrown upon the tube feet causes them to be 

 withdrawn. 



Cutting the oral nerve ring does not interfere with the local 

 reflexes of the spines or tube feet, but it prevents the sea urchin 

 from crawling away from the light. While reactions to local 

 stimulation by light are of -a character to aid in the photo- 

 tactic response they cannot alone effect the locomotion of the 

 animal. Phototaxis, like movements away from mechanical 

 stimulation, depends upon a co-ordinated activity of various 

 organs of locomotion. 



