Wound Reparation—A ctinian Tentacles 225 
and the proximal end of the piece lying distad of that plane.) 
The results of this study may be summarized as follows. 
During the first half hour after the cutting the behavior of prox- 
imal and distal cut ends was not strikingly different. The prox- 
imal ends showed a somewhat greater tendency to wrinkle than 
the corresponding distal ends. As already noted, the wrinkling 
was more marked in the pieces nearer the base of the tentacle. 
Further, the tendency of the pieces to collapse was much greater 
in pieces from the base of the tentacle than in those from its tip, 
a difference which is evidently due to the difference in diameter 
at base andtip. The openings at all the cut ends were diminished 
in area by the characteristic inbending of the cut edges. In many 
cases it could be seen that a distal opening was slightly smaller 
than its corresponding pruximal opening. Immediately after 
cutting, the cut edges are slightly ragged and more or less angular 
in outline as a result of the pressure of cutting. In some cases 
even during the first half hour a difference arose between proximal 
and distal ends in that a distal end became more nearly smoothly 
circular in outline than its corresponding proximal end. We have 
already noted that excised fragments of tentacles ordinarily do not 
exhibit the nipple condition except under the influence of a little 
artificially applied internal pressure. In these polarity experi- 
ments no attempt was made to apply internal pressure becausel 
desired to introduce no unnecessary disturbances into the experi- 
ments in order that conditions at proximal and distal cut ends 
should be as nearly as possible identical so far as outside factors 
were concerned. Nevertheless there were many cases in which 
a fairly distinct nipple did appear at the distal end of the middle 
one of the three pieces into which a tentacle was cut, but there was 
no case where a nipple formed at the distal end of one of the most 
proximal of the three pieces. When the tentacle was cut into two 
pieces a nipple often formed at the distal end of the proximal frag- 
ment. In a few cases, too, the proximal end of the most distal 
piece assumed a nipple-like form resembling, therefore, the distal 
ends of those middle pieces which formed nipples. All of these 
proximal nipples were of comparatively brief duration. Gradually 
becoming less marked, at the end of an hour they had disappeared, 
