160 MODIFICATIONS OF BEHAVIOR 



carried by the tentacles to the mouth and there swallowed, 

 to be ejected as inedible after a longer or shorter period. 

 After a few days, the number varying in different individuals 

 from two to five days, the fragment is no longer swallowed 

 and, in about an other two days, the tentacles will no longer 

 take hold of it. This procedure is more regular in the case 

 of pellets of paper than in the case of India rubber, in which 

 results were very variable. The results seem to indicate a 

 certain amount of persistence of impressions, when the latter 

 are received several times in succession at short intervals. 



"The first impression which persists is one in the mouth 

 region leading to refusal of the pellet. As this is strengthened 

 the sequence is further abbreviated, an inhibitory stimulus 

 would seem to proceed from the mouth to the tentacles 

 preventing them from gripping, when the stimulation due to 

 contact with the filter-paper has passed from them to the 

 mouth. 



" A further point of interest is that what does persist seems 

 to remain a property of the tentacles affected, and of that 

 part of the mouth directly related to them. It does not 

 appear to be a possession of the entire animal, for other 

 tentacles, on the opposite side for instance, can be tricked 

 subsequently, at any rate once or twice, before they too 

 exhibit the inhibitory reaction." The effects of the ex- 

 perience were found to be lost after from six to ten days. 



Whether or not we have in this instance the formation of 

 a new association, as the behavior of the anemone seems 

 to indicate, is not entirely certain. It is possible that the 

 seat of the change of behavior is in the tentacles alone. 

 Allabach has shown that after the tentacles of Metridium 

 have responded to a stimulus a few times their production 

 of mucus becomes much diminished and this probably 

 affects their subsequent activity. If this factor would 



