THE BEHAVIOR OF THE SHORE-ANEMONE 325 



accept food. Upon watching an anemone in its normal habitat 

 one observes the dozens of times that it partially contracts and 

 expands under the stimulation of the waves and it is perhaps 

 due to this type of response enforced upon the animal by the 

 conditions of its very existence that the muscular fibrils do not 

 become so easily fatigued. Certainly also a single injection of 

 beef juice causing the animal to contract only once cannot cause 

 the muscles to become fatigued solely through the power of a 

 single contraction. There seems to be some other more funda- 

 mental reason involved, though no doubt the marked contrac- 

 tion following such a treatment may to a certain extent be an 

 accessory factor. 



Diminution of responsiveness from mucus secretion. — Parker's 

 conclusion from his experiments on the feeding reactions of 

 anemones is ''that the successive application of a very weak 

 stimulus is accompanied, not by the summation of the effects 

 of stimulation, but by a gradual decline in these effects till 

 finally the response fails entirely." Jennings concludes in 

 regard to the modifiability in Stoichactis helianthus and Aiptasia 

 annulata that "it is clear that the animal is a unit so far as 

 hunger and satiety are concerned." In case the satiety has 

 arisen through the efforts of the tentacles of one side, the ten- 

 tacles of the other side are equally affected by it. The chief 

 factor in determining the reaction to food is the general progress 

 of metabolism. 



Allabach (1905) observes in her paper on Metridium that in 

 taking food the region in contact with the food produces a very 

 large quantity of mucus enveloping the food body. Holmes 

 (1911) in discussing the claims of Fleure and Walton (1907) 

 for the power of associative memory in the sea anemone says: 

 "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 pro- 

 duction of mucus becomes much diminished and this probably 

 affects their subsequent activity. If this factor would modify 

 the irritability of the tentacles for some time it might explain 

 the change of behavior." 



There can be no doubt that the reaction accompanying the 

 excessive secretions of mucus as the result of beef juice and 

 potassium chloride does alter the irritability of the tentacles. 



