452 WAYLAND M. CHESTER 



diameter of 1 mm. at the base and 0.1 mm, at the tip. Except 

 where otherwise stated the results are with tentacles of approxi- 

 mately this size. 



A tentacle of such an animal, when fully expanded, was cut 

 off with sharp scissors about midway of its length. The imme- 

 diate result was the collapse of the tentacle stump, owing to the 

 pressure of the liquid within the tentacle being released ; and this 

 was followed by its contraction to the disk. The collapse and 

 contraction of the tentacle were accompanied, however, by the 

 bending of the adjacent tentacles toward it, and the contraction 

 of the disk at that point, so that a marked indentation and infold- 

 ing occurrred there. Then the disk as a whole rolled in and the 

 column sphincter closed. The tentacle stump was hidden by 

 the adjacent tentacles and by the inrolling of the disk for nearly 

 two minutes. At the end of that time the disk had regained its 

 expanded condition and the tentacles adjacent to the stump were 

 expanding. The tentacle stump was also expanding and, within 

 five minutes, its distal end meanwhile having been closed, was 

 extended almost as much as before the cut was made. The clos- 

 ure of the tentacle had resulted in a rounded end, which carried a 

 short and constricted nipple-like protrusion (fig. 1). Within 

 half an hour the protrusion was, if anything, more constricted 

 and the tentacle appeared more inflated than its neighbors, or 

 than it was before the cut was made. The marked contrast to 

 the adjacent tentacles is in part due to a change of shape, for it 

 is now cylindrical from its base to the rounded end, whereas, 

 before it was cut, it was conical. Figure 1 shows the difference 

 of shape between the cut and uncut tentacle one hour after the 

 cut was made. 



Light brown animals were found to be better for observation 

 than the darker specimens. The endoderm of their tentacles, or 

 a part of it, is black. At the constricted end of the cut tentacle, 

 this shows as a black plug in the axis (fig. 1). The exterior of 

 the constriction is white and opaque, but where the tentacle 

 resumes its normal diameter this white color grades into the usual 

 pale brown. The black of the endoderm as seen in optical section 

 is shown in figures 1, 2, 4, 5 and 6 by stippling. 



