BEHAVIOR OF METRIDIUM. 39 



The loss of reaction on the part of the tentacles after much 

 food has been taken is not due to fatigue resulting from their 

 activity in taking food. This is demonstrated by the following 

 facts : (i) The animal may be fed from one side of the disk till 

 it is satiated. Now meat given to the opposite side of the disk 

 is not taken, though the tentacles of this side have not been 

 active, and so cannot have become fatigued. (2) Seven hours 

 after the animal has been fed all it will take, the tentacles still 

 refuse to take food, though they have had this period for recuper- 

 ation. Actual fatigue, as we shall see later, lasts but a few 

 minutes. 



The effects of hunger and satiety are further seen in the reac- 

 tions of Mctridinin to indifferent bodies, such as bits of filter 

 paper. These are commonly taken readily by hungry specimens 

 of Mctridinui. The tentacles react to them, just as to meat, so 

 that they are carried to the mouth. Here they cause the 

 reversal of the ciliary movement in the same way as does meat, 

 so that they are carried inward. But after the animal has been 

 fed a considerable quantity of meat, it will no longer take filter 

 paper. First the outer tentacles refuse it, later the inner ten- 

 tacles, and finally the mouth. A piece of filter paper placed 

 squarely on the mouth no longer causes the reversal of the 

 stroke of the cilia of the oesophagus, so that it is not carried 

 inward. 



The fact that the reversal of the cilia under such stimuli 

 depends on the physiological state of the animal is one of much 

 interest. It shows that the cilia are not entirely independent of 

 such states, as some other facts would seem to indicate. 



Seven hours after the animals had been fed an abundant meal 

 of mussel meat, they still refused to take filter paper, though 

 before the meal paper was taken readily. 



Thus it is clear that the state of the processes of metabolism is 

 in j\lctridinin, as in other sea anemones, a most important factor 

 in determining behavior under mechanical and chemical stimuli. 

 But it is equally clear that this will not explain the results of 

 Parker's experiments, described in the first paragraphs of this 

 paper. Parker found that after one side of the disk has refused 

 to take paper, the other side still accepts it. In repeating 



