454 ^' ^' 'Jennings. 



the mouth. A piece of meat or filter paper may be completely 

 enclosed by either species within ten seconds of the time it comes 

 in contact with a tentacle. 



With these two species of Aiptasia the experiments of Nagel 

 and Parker, mentioned on page 448, were repeated and varied, 

 with somewhat peculiar results. Pieces of crab meat and of 

 filter paper (plain or soaked in juice of crab meat) were given 

 alternately to the individual under experimentation. In Metri- 

 dium and Adamsia, as we have noted, the animal soon comes to 

 reject the filter paper, while still accepting the meat. 



In Aiptasia annulata a typical experiment is as follows: The 

 animal is fed alternately filter paper soaked in crab juice and crab 

 meat. Both are taken readily till four pieces of each have been 

 ingested. At the fifth piece of paper — the ninth piece of the whole 

 series — the animal balks and rejects it. But it likewise rejects the 

 immediately following fifth piece of meat! It has evidently lost 

 its hunger, and refuses to take anything. This is the usual result 

 with Aiptasia annulata. 



In Aiptasia No. 2 plain filter paper (not soaked in crab juice) 

 was given alternately with pieces of crab meat. In a typical 

 experiment six pieces of filter paper and six of meat were 

 taken in regular alternation. But the seventh piece of paper and 

 the immediately following seventh piece of meat were rejected. 



The results above given are the usual ones. But sometimes, 

 though rarely, results are reached which are analogous to those 

 attained in Metridium by Parker. Thus, in one case a specimen 

 of Aiptasia annulata accepted the first piece of plain paper, but 

 thereafter refused paper consistently, while accepting meat offered 

 in regular alternation with it. 



For all these results the following explanation suggests itself: 

 The animals when hungry take both meat and filter paper; when 

 satiated they take neither. Usually the tendency to take both 

 ceases at the same point, but sometimes the reaction to the weaker 

 stimulus (filter paper) cease before that to the stronger stimulus — 

 as a higher animal that is not hungry may refuse most things, 

 while accepting peculiarly tempting morsels. 



If the degree of hunger is thus the determining factor, then it 

 should be possible to produce the rejection of the filter paper by 

 feeding meat alone. This turns out to be the case. Indeed, 

 usually the rejection of filter paper may be induced more readily 



