i^'^''] Jennings. — Behavior of the Starfish. 97 



ai-iii. This also looks like intellioence, for the animal seems to be 

 able to avoid a danger. The late Professor Norman called my 

 attention to the fact that when one arm of a starfish is stimulated 

 the feet of this arm are drawn in and the arm becomes inactive. 

 This is, however, only trne of the stinnilated arm ; the others re- 

 main active. Therefore, according to the parallelogram of forces, 

 a movement away from the point of stimulation takes place. 

 Intelligence plays no part in this phenomenon." (Loeb, 1900, 

 p. 65). 



We are not here concerned with the question regarding intel- 

 ligence, but only with the explanation of the movement of the 

 starfish away from the side stimulated. It is certainly difficult 

 to conceive how such an explanation could be given by anyone 

 that had observed with care the locomotion of the starfish. It is 

 possible that in some cases when one ray is stimulated locomotion 

 takes place entirely with the other rays, but such cases are very 

 rare; though I have watched carefully for this, I have never 

 seen one. As a rule the walking away from the stimulated 

 region is due, like the usual locomotion of the starfish, to the 

 cooperation and coordination of the tube feet of all the rays. 

 To imagine that the tube feet of each ray merely pull toward that 

 ray, and that locomotion follows merely in the direction of the 

 resultant of these discordant pulls, partly against the action of 

 the tube feet of certain rays, is to have an extraordinarily crude 

 and mistaken idea of the behavior of the starfish. The active tube 

 feet of all the rays are pushed forward in the direction in which 

 the starfish is going ; their suckers attach themselves, and by the 

 contraction of the tube feet (in the way described below) the 

 starfish is carried forward, the action of all the tube feet aiding 

 in this. Thus the tube feet of each of the five rays have a dif- 

 ferent movement from those of the other rays. In the anterior 

 ray the feet are pushed toward the tip; in the posterior ray or 

 rays they are pushed toward the disk; in transverse rays they 

 are set transversely to the long axis of the rays; in oblique rays 

 they take an oblique direction. All the tube feet are extended 

 in such a way as to be parallel. There is a single coordinated 

 impulse, causing all to cooperate in moving the starfish in a 

 given direction. This coordinated extension of the tube feet 



