EXPERIMENTS ON ECHINODERMS 65 



that the ventral side of the starfish is positively ste- 

 reotropic, or, in other words, that the starfish becomes 

 restless if its ambulacral feet are not in contact with 

 solid bodies. 



3. Preyer accredits the starfish with possessing 

 " intelligence." He placed one arm of an Ophiuris 

 in a piece of rubber tubing in order to see whether 

 the animal would be clever enough to rid itself of this 



o 



impediment to its movements. He found that after 

 a time the arm " freed itself " from the tube. I have 

 repeated the experiment in these animals and found 

 that the Ophiuris pays no attention to the rubber 

 tube. The animal of course loses it after a time un- 

 less it fits too closely, but it is always purely a matter 

 of chance, and there is no more intelligence involved 

 than the clothes-line displays when the clothes are 

 blown from it by the wind. Romanes found that 

 when one arm of a starfish is stimulated the animal 

 moves in a direction opposite to the stimulated arm. 

 This also looks like intelligence, for the animal seems 

 to be able to avoid a danger. The late Professor 



O 



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 true of the stimulated arm ; 

 the others remain active. Therefore, accordine to the 



o 



parallelogram of forces, a movement away from the 

 point of stimulation will take place. Intelligence 

 plays no part in this phenomenon. 



4. The tendency to crawl upwards on vertical 



