254 The Animal Mind 



indeed reports that while the responses of Actinia equina 

 and A. rubra to mechanical stimulation cease on repetition 

 of the stimulus, those to food stimulation continue indefi- 

 nitely (581). If the change from food-taking to negative 

 reaction has a conscious accompaniment, this might natu- 

 rally be thought of as a change from pleasant to unpleasant 

 affective tone. Nagel observed that if a ball of filter paper 

 soaked in fish juice were placed upon one of the tentacles 

 of the sea-anemone Adamsia, it was seized as eagerly as a 

 ball of fish meat, but that when this deception had been 

 several times repeated, the ball was held for a shorter 

 period each time, and was finally rejected as soon as offered. 

 Nagel is inclined to think that this is learning by experi- 

 ence, and points out that the psychic life of Adamsia must 

 possess little unity, for the "experience" of one tentacle 

 does not lead other tentacles to reject the paper balls at 

 once (521). Parker finds similar behavior in Metridium, 

 and explains it by saying that the filter paper offers but a 

 weak food stimulus, and that "the successive application 

 of a very weak stimulus is accompanied by ... a gradual 

 decline in the effects, till finally the response fails entirely" ; 

 in other words, that we have adaptation to a food stimulus 

 (533). Jennings fed Aiptasia alternately with pieces of 

 crab meat and with filter paper soaked in meat juice, the 

 result being that the fifth piece of filter paper was rejected 

 but so was the crab meat thereafter. Jennings came 

 to the conclusion that the phenomenon is due simply to 

 loss of hunger on the animal's part, and that where Parker 

 found that the crab meat would be taken after the filter 

 paper was refused, it was because the latter was a weaker 

 stimulus and naturally was the first to call forth the effects 

 of satiety. The objection to the hunger hypothesis is that 

 other tentacles of the same animal will react after one 



