64 Instinct and Intelligence 



time after an arm of a star-fish has been am- 

 putated, its circulation and consequently meta- 

 bolic processes cease, and with this change the 

 potential energy of the nerve cell fails, and all 

 instinctive or any other movements of the am- 

 putated arm cease. If the sensory organs of 

 an amputated arm are removed, or if they are 

 not appropriately stimulated the limb remains 

 motionless. 



From experiments made on various species 

 of living star-fish we learn that the function 

 performed by its central nervous system is to 

 bring about the co-ordinate working of the arms 

 and various parts of its body in a purposive 

 manner. If the circum-oral rings are removed 

 the animal completely and permanently loses 

 all power of co-ordinating its arms or their 

 sucker feet. 



The result of excision of the sensory organs 

 of jelly-fish and star-fish leads us to conclude 

 that the exciting cause of the animal's instinc- 

 tive behaviour depends, to a large extent, on 

 work performed by these organs; for if they 

 are destroyed all such action is abolished, 

 although the animal may continue to live. This 



