Wound Reparation—A ctinian Tentacles 201 
perfectly transparent except for irregular transverse bands, which 
are whitish and opaque. 
The results of transection of tentacles in Aiptasia were sub- 
stantially the same as in Condylactis. ‘The following differences 
as to details may be noted. ‘The contractions caused by the cut- 
ting were less extensive and of shorter duration than in Condylac- 
tis. Even when the tentacle was cut near its base, so that more or 
less contraction of neighboring parts of disc and column and of the 
nearby tentacles ensued, there was full expansion of these parts 
within two to five minutes after the operation and the stump of 
the cut tentacle extended to its full length with a conspicuous 
nipple on its hemispherical closed end. The nipples were, upon 
the average, longer in proportion to their diameter—more slender 
—than in Condylactis. The nipple was whitish and opaque, 
while the wall of the closed end showed a gradual shading-off from 
the whitish opacity immediately around the base of the nipple to 
the transparency of the lateral wall. When only a very short 
piece was clipped from the end of a well extended tentacle of 
Aiptasia there was only a slight contraction of the tentacle, and the 
closing of the cut end and the formation of the nipple took place 
almost instantaneously. In one case a large tentacle of the inner- 
most cycle was transected very near its base. Fig. 3 shows the 
appearance of the stump of this tentacle, a half hour after the 
operation, as seen in a lateral view of the upper end of the column. 
This case showed more conspicuously than any other the important 
part played by the nipple in the closing of the wound. Here a 
large portion of what remains of the wall of the base of the ten- 
tacle is gathered in to form the nipple and consequently the ex- 
treme lower part of the wall of the tentacle is pulled down so as to 
lie almost in the plane of the disc, being only slightly convex up- 
ward. ‘he nipple has every appearance of a strong sphincter 
operating to resist the pressure of internal fluid. 
In a few exceptional cases, both in Condylactis and in Aiptasia, 
the cut end of a tentacle closed without the formation of a nipple. 
The tissue at the center of the closed end appeared merely some- 
what thickened. 
A modification of these experiments consisted in making an 
