1907] Jrnnings. — Behavior of the Starfish. 117 



4. Effect of Previous Stimuli. — This persistence of an im- 

 pulse to move in a certain way is sometimes evident even when 

 the animal has not yet begun to move ; it produces a striking after 

 effect of stimulation. Thus, the starfish was placed on a smooth, 

 flat surface. The rays began their usual exploring movements ; 

 under these conditions if one of the rays touches some object. 

 the animal begins to move in that direction. Before locomotion 

 began the tube feet of the tip of the ray c were allowed to come 

 in contact with the side of the vessel. Now, before the starfish 

 began to move toward that side, it was taken up and turned 

 around, so that the ray c was directed toward the open part of 

 the vessel, instead of toward the side. Now the tube feet of the 

 ray c began to extend and explore, as if searching for the object 

 which they had before touched. At the same time the feet of the 

 other rays were moved about and extended in the same direction 

 as were those of c, while the starfish began to move toward c. 

 This experiment was repeated many times, and under various 

 conditions, with the same results. Thus, when the starfish is 

 moving on a plane surface away from a window, a solid object 

 is allowed to touch for an instant the tube feet of one of the 

 lateral rays, and is then removed. Thereupon the tube feet of 

 that side extend, and the starfish sidles off in the direction in 

 which it had touched the solid object. 



The behavior of the starfish is in these relations objectively 

 like that of a higher animal which, having experienced a certain 

 stimulus, searches for this after it has disappeared. Such an 

 animal is commonly said to show memory of the past stimulation. 



These results recall and perhaps partly explain certain ex- 

 periments of Preyer (1886), in which the starfish was found to 

 have a decided tendency to move toward certain rays. Preyer 

 gave no explanation of these results. They are discussed further 

 in a later section (p. 150). 



The strong tendency which the starfish shows to continue a 

 movement once begun is evidently akin to the formation of a 

 habit. One is led to inquire Avhether this tendency could not be 

 increased and made lasting by repetition of a given movement; 

 in other words, whether the starfish may not form real habits. 

 This question will be dealt with in a section devoted especially 

 to this matter (pp. 148-169). 



