468 WAYLAND M. CHESTER 



during the time the two fragments were kept under observation, 

 but at the end of the experiments it was proved by study of sec- 

 tions, that the cavities of the grafted pieces were continuous. 

 On each day after union, tests were made to determine the direc- 

 tion of cihary motion, and the responses to touch. The ciha 

 were not reversed in any of the experiments, but moved in opposite 

 directions in the united fragments. Whether, in response to 

 touch, the tentacle bent toward or away from the point of contact, 

 could not always be determined, but in response to a slight touch, 

 the contraction was always proximal to the point of contact for 

 that graft fragment, while the response did not extend to the other 

 fragment. Finally, when the ends of such grafts were cut off, 

 each grafted part behaved as if it were separate. In the grafts 

 with the basal ends united, the cut tips contracted slightly, and 

 in a few hours became rounded and closed like distal ends of free 

 excised fragments. In the grafts with distal ends united the cut 

 ends continued to behave like proximal ends, remaining open for 

 a long time without constriction, and showing the wrinkles 

 peculiar to proximal ends. In Metridium, therefore, no reversal 

 of the ciliary or muscular polarity in the. tentacles was found to 

 occur. 



SUMMARY 



Metridium exhibits the same method of closing a cut tentacle 

 that was found by Rand for other sea anemones. When a part of 

 the tentacle is cut off, the cut edge of the attached stump rolls in 

 slightly as the tentacle collapses. The adjacent tentacles may 

 bend in toward it, and the neighboring region of the disk may be 

 invaginated. As the cut tentacle expands, a small, muscular, 

 nipple-like sphincter closes the end tightly. Within twelve to 

 twenty-four hours after cutting, the tentacle becomes structurally 

 closed and the sphincter is gradually relaxed. 



In an excised tentacle whose tip is cut off, the distal cut end 

 becomes rounded and shows, by its shape and change of color, 

 evidence of muscular contraction comparable to that which pro- 

 duces the nipple of the attached stump, although the end does 

 not actually become nipple shaped. If the end of an attached 



