Wound Reparation—A ctinian Tentacles 215 
Almost immediately after cutting a tentacle there is to be seen 
a slight but distinct inbending of all the cut edges. In its abrupt- 
ness this change differs from the later slow closing of the cut edges, 
which may require as much as a day for completion. It certainly 
appears to be quite distinct from the muscular contractions which 
ensue. This abrupt initial inbending is similar in nature to what 
has been seen in so many two-layered organisms, both embryo 
and adult, where cut walls promptly bend so that ectoderm is 
on the convex side of the curve, a condition which suggests some 
preéxisting inequality of tension in the two body layers. 
When a transverse slit is cut in the side wall of a tentacle the 
closing of the wound takes place in much the same way as when 
a piece is removed. ‘There is immediately a muscular contraction 
of the tissue around the slit as a result of which the slit is virtually 
closed. The appearance of the tissue around the slit is as if a ring 
of muscle fibers surrounding the slit was in a state of contraction. 
However, this appearance may very well result from the local 
contraction of both the longitudinal and circular muscle fibers in 
the near vicinity of the cut. The sharp bending of the tentacle, 
which looks so beautifully protective, is perhaps nothing more 
than an incidental result of the local and one-sided contraction 
of tissues. Then, during the next day or two, there takes place a 
slow structural closing of the opening. ‘The muscular contraction 
diminishes as this closing progresses. ‘There is no external evi- 
dence of formation of new tissue. 
Comparing the behavior of the transversely cut tentacle of one 
of these large actinians with the behavior of the similarly cut trunk 
of Hydra it will be seen that the processes of closing a cut end are 
to a certain extent very similar in the two cases, if not identical. 
In both there is an immediate, although slight, inbending of the 
wall at the cut edge, probably due to difference of tension in the 
body layers. Then ensues a slow continuous inbending of the 
wall at the cut end, the opening being thus gradually diminished 
until the end is completely and structurally closed. (In the attached 
tentacle this process is obscured by the presence of the nipple.) 
In Hydra the closure may be completed within half an hour. In 
a Condylactis tentacle it requires several hours or even a day. 
