452 H . S. "Jennings. 



region lying behind the mass (between it and the center of the 

 disk) begins to swell, producing a high, rounded elevation, with 

 tentacles plump and swollen. The waste mass is now on a steep 

 slope, and is bound soon to slide down and over the edge. Some- 

 times by a continuation of this process the entire disk comes to 

 take a strongly inclined position, with the side bearing the debris 

 below. Often one portion of the edge of the disk after another 

 is lowered in this way, till all the waste matter has been removed. 

 The disk then resumes its horizontal position, with nearly flat 

 or slightly concave surface. 



Sometimes the edge bearing the debris cannot be lowered, 

 owing to the fact that it is almost against an elevation in the 

 irregular rock to which the anemone is attached. In this case, 

 after perhaps an attempt to bend the edge downward, the part 

 between the edge and the waste body swells and rises, rolling 

 the mass toward the center, while at the same time the region 

 between it and the center sinks down. The sinking continues 

 till it reaches the opposite edge, so that the mass is rolled 

 across the disk to the opposite side and there dropped off' the 

 disk. The process is slow, often taking fifteen minutes to half 

 an hour. 



The rejecting reaction is characterized by great flexibility and 

 variability. The debris or refused food sets in operation cer- 

 tain activities; if these do not remove the source of stimulation, 

 other activities are induced until one is successful. 



Thus in Stoichactis the same stimulus — crab's meat — may in 

 the same individual produce sometimes the long train of activities 

 resulting in the ingestion of food; in other cases the complicated 

 and variable behavior resulting in rejection, in still others a com- 

 bination of the two. The deciding factor is internal — the con- 

 dition of the metabolic processes. 



Aipt: 



asia. 



Two species of Aiptasia were studied. One was Aiptasia 

 annulata Les.; the other a smaller and darker species, with shorter 

 tentacles, which I have been unable to identify with certainty. 

 I shall call it Aiptasia No. 2. Both came from the moat surround- 

 ing Fort Jeff^erson. Rather small specimens, with columns 4 to 10 

 cm. in length, were used in most of the work. 



