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the tube feet which seem to indicate that they all act very much 

 like their neighbors, but with too much independence to lead to the 

 belief that they are subject to the control of a higher center. Tube 

 feet act only in response to stimuli which affect them or spread to 

 them from neighboring tube feet, 



Possible physiological explanation in the traction on the 

 tube feet resulting from the movement of the rays over the substrate, 



It seams to me that the only constant factor that could ac- 

 count for the behavior observed, is the traction of the substrate on 

 the tube feet. This traction is the mechanical result of the move- 

 ment of the starfish over the substrate, (See Cole 1913lr), 



Thu^B Mangold's starfish (fig, ) is moving in the direction 



of the ant>w. The various tube feet may receive stimuli from the aub- 



I ***i 



vx <y 



strate which result in their orienting this direction. 



Similarly the righting starfish has set in action by the 

 activity * the rays a and b_ (fig. 14) a somersaulting motion on a 

 horizontal axis. This results in pulling the rays, c and e in the 

 direction of the arrow tnat indicates their motion. It is this trac- 

 tion that may orient the tube feet. In this connection it is to be 

 noted that if the rays o and e do not droop down to the substrate but 

 are carried over at a level of or above the disk ( as is more often 

 the case) their coordinated impulse does not reverse but remains, as 

 indicated by the parallel extension of the tub feet, in haroiony with 

 that of the rest of the animal. 



In the case of the deviating starfish, the axis of the rota- 

 tion that is involbed in the avoiding erf the obstacle is of course the 

 obstacle itself. There is, in th progress of the reaction first a 

 pushing against the obstacle which involves cessation of locomotion on 

 the part of the rays on one side of the body, but its continuation 

 ( or quick resumption after temporary cessation) 



