116 University of California Publications in Zoology. [Vol. 4 



spite of changed conditions. For example, in a certain case the 

 sun was allowed to shine on the starfish in such a way that the 

 ray d was on the side opposite the source of light. The animal 

 tlien began to move, as we should expect, toward its ray d, away 

 from the source of light. Now the creature was suddenly seized 

 with the hand, taken from the bottom, turned around, and re- 

 placed on the bottom in such a position that the ray d was di- 

 rected toward the sun. The interrupted movement toward the 

 ray d was at once resumed, so that the starfish was now moving 

 toward the sun. If the moving animal was suddenly placed with 

 the advancing ray transverse or oblique to the direction of the 

 sunlight, it continued as before to move toward d, without re- 

 lation to the direction of the light. 



This persistence in a direction of movement (relatively to 

 its own structure) when once begun, usually lasts under such 

 conditions as we have just described only for about five to seven 

 seconds. Then the animal is likely to stop, and slowly to begin 

 moving away from the source of light. But sometimes it per- 

 sists in a given direction much longer, in spite of change in 

 the outward conditions. This is particularly likely to occur 

 when the animal has been moving for some time in a given 

 direction. 



This persistence in a given direction is shown in exactly the 

 same way whether the original source of the impulse to move is 

 light or something else. At times a starfish shows an obstinate 

 tendency to move toward a certain one of its rays, without much 

 relation to external conditions. Thus, a starfish placed in a 

 flat vessel near a window started to move toward its ray d, — 

 which led it, contrary to the usual rule, toward the window. I 

 now covered the side next the window with a black cloth, so that 

 the starfish was going straight into the dark instead of toward the 

 light; it continued in the same direction, the ray d in advance. 

 I now took up the creature and turned it quickly around, so that 

 the ray d, was headed away from the dark ; the starfish continued 

 toward d, as before. Shading various parts of the body or rays 

 had no effect on the movement ; the animal persisted in moving 

 toward the ray d, quite independently of the distribution of light 

 and shade. 



