Modifiahility in Behavior. 457 



those of another part of the same disk will still carry it to 

 the mouth. This shows clearly that a general lack of hunger on 

 the part of the organism as a whole cannot be the only factor 

 involved. In Aiptasia No. 2 I tried experiments to determine 

 whether there was the same independence in the tentacles of 

 different regions. Crab meat was given to the tentacles of the 

 left side; these carried it to the mouth, where it was swallowed, 

 the tentacles of the right side playing no part in the reaction. 

 After the tentacles of the left side had taken five pieces they 

 reacted very slowly, a piece of meat resting against them for several 

 seconds before it was seized. When it was finally carried to the 

 mouth, however, it was swallowed readily. The next piece of 

 meat, not being seized at once by the left tentacles, was trans- 

 ferred to those of the right side. They seized it instantly and 

 quickly carried it to the mouth. Thus it is clear that the experi- 

 ence of the individual tentacles plays some part in the behavior; 

 either from fatigue or some other cause, tentacles frequently 

 stimulated gradually lose the tendency to respond. The fact 

 that this result is produced by meat, the purest form of food, 

 seems to indicate that fatigue may be the cause. 



But the rest of the experiment indicates that this plays only a 

 minor part in the change of behavior. After a short rest the 

 giving of food to the tentacles of the left side was resumed. They 

 continued to carry it slowly and with much delay to the mouth, 

 where it was very slowly swallowed. After taking four more 

 pieces, the tentacles of the left side absolutely refused to carry 

 any more food to the mouth. The mouth had now almost ceased 

 taking food when directly applied to it, though after some minutes 

 the food was finally ingested. Now a piece of meat was given to 

 the tentacles of the right side, which had only reacted once, and 

 that more than fifteen minutes ago. Yet they behaved in exactly 

 the same way as did the others, refusing to react at all, save by 

 hanging back from the disk along the column. 



Thus it is clear that the animal is a unit so far as hunger and 

 satiety are concerned. If the satiety has arisen through the activ- 

 ity of the tentacles of one side, the tentacles of the other side are 

 equally affected by it. It is the general progress of metabolism 

 that is the chief factor in determining the reactions to food. 



As Torrey ('04) has already noted for Sagartia, the reactions of 

 satiated sea anemones differ in many other ways from those of 



