FOOD AND THE NEEVE-NET 145 



from Gee's experiment, that muscular fatigue is not ac- 

 countable for the change in the responsiveness of the ten- 

 tacles, but it is entirely possible that it may have been 

 caused by sensory fatigue. It is a common observation 

 that if a sensory surface is placed under active stimula- 

 tion, it is often only a short time before it will fall off 

 very considerably in its receptiveness, and it is this form 

 of fatigue in all probability that is accountable for the 

 change in the tentacular responses of Metridium on con- 

 tinuous feeding. A repetition of Allabach's experiment 

 of placing food on the tentacles of Metridium and, after 

 they have responded, of removing it from the lips before 

 it has been swallowed has in all instances confirmed her 

 results; namely, the tentacles fall off in responsiveness. 

 In view of what has already been stated it seems impos- 

 sible to explain this phenomenon except as a result of 

 sensory fatigue. 



But there are also changes in the tentacular responses 

 of actinians that are by no means so easily explained as 

 are those that have just been considered. Jennings 

 (1905) 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. Allabach (1905) 

 states that Metridium can be fed from one side of its disc 

 till no more food will be accepted, whereupon food will 

 likeT-ise not be accepted by the tentacles of the opposite 

 side. Gee (1913) has also recorded essentially the same 

 10 



