200 G. H. PARKER 



I can confirm her results, namely, the tentacles fall off in re- 

 sponsiveness. In view of what has already been stated I am 

 unable to explain this phenomenon except as a result of sensory 

 fatigue. 



But there are also changes in the tentacular responses of actin- 

 ians that are by no means so easily explained as are those that 

 have just been considered. Jennings ('05, p. 457) states that 

 when the tentacles on the left side of an Aiptasia were plied with 

 crab meat, they transferred the food to the mouth quickly five 

 times, after which they reacted slowly on the sixth trial and 

 hardly at all on the seventh. 



On trying the meat on the tentacles of the right side, it was 

 found that the transfer to the mouth was quickly accomplished. 

 Returning now to the left side four sluggish deliveries were 

 effected after which the right side would now take no meat at 

 all. AUabach ('05, p. 39) states that Metridium can be fed from 

 one side of its disc till no more food will be accepted, whereupon 

 food will likewise not be accepted by the tentacles of the oppo- 

 site side. Gee ('13, p. 321) has also recorded essentially the 

 same condition in Cribrina. From these observations it seems 

 clear that changes induced in the muscular responses of the 

 tentacles of one side profoundly influence the reactions of the 

 tentacles on the other side. As Jennings ('05, p. 457) has put 

 it, the animal reacts as a unit, one side influencing the other. 



I have repeated experiments of this kind on Metridium and 

 though my results are not as striking as those described by the 

 authors already quoted, I am convinced that when a Metridium 

 is fed persistently by means of the tentacles of one side and so 

 as to avoid touching with the food those of the other side, the , 

 opposite tentacles a^e nevertheless eventually influenced in their i 

 reactiveness and become less responsive as the feeding proceeds, i 

 Here would seem to be a good instance of some such general 

 effect as that of changed metabolism or the general utilization 

 even of nervous experience. 



To ascertain whether changes in the tentacular responses of 

 one side of the disc are transmitted nervously to the other side, 

 I fed small pieces of mussel to the tentacles of one side of a 



