Wound Reparation—A ctinian Tentacles 197 
entirely independent of any contraction of the tissues themselves. 
At the center of the tip of a normal tentacle there is a minute pore. 
Presumably this pore is kept closed while the tentacle is extended. 
If, however, the animal is suddenly lifted out of the water, fine 
jets of fluid spurt with considerable force from the tips of the ten- 
tacles. It seems to me probable that when a tentacle contracts 
this terminal pore is opened so as to allow escape of internal fluid— 
an arrangement which would, apparently, facilitate quick con- 
traction. However, I have no experimental proof of this matter. 
When the stump of a cut tentacle has become extended after the 
fashion described, the cut end is closed in the sense that it is able 
to resist the pressure within the tentacle, so that the fluid does not 
escape and the tentacle remains well distended. But this closure 
of the cut end is not necessarily permanent. Usually, when the 
stump contracted, the nipple persisted during the contraction 
phase. However, it was several times clearly seen that, in the 
contracted condition, the axis of the nipple was pierced by a fairly 
large pore. In occasional cases of extreme contraction, the 
nipple disappeared and the end of the contracted stump became 
again broadly open. In such cases, at the beginning of the proc- 
ess of extension the opening was rapidly narrowed and the nipple 
reappeared. 
The foregoing account refers to tentacles which were cut mid- 
way.of theirlength. ‘Tentacles cut nearer the base or nearer the tip 
differed in some points of behavior from those which were cut mid- 
way of their length. When a tentacle is transected near its base, 
the resulting contractions are much more marked and persist for 
alonger time. The invagination of disc and column into which the 
cut tentacle is withdrawn is deeper than when the cut is midway of 
the tentacle’s length, and from a half hour to an hour may elapse 
before sufficient relaxation takes place to bring the cut tentacle 
again into view. ‘The closing of the cut end and the formation of 
the nipple occur as already described. The nearer the tip the ten- 
tacle is cut, the less is the amount of the resulting contraction and 
the shorter is the duration of it. If only the distal fourth or fifth 
of the tentacle is cut away the contraction may not extend beyond 
the stump of the tentacle itself. For example, a piece one or two 
