200 Herbert W. Rand 
anormal tentacle. It remained extended while the other tentacles 
were extended and participated in any general contraction of 
tentacles, as well as responding in the usual way to individual 
tactile stimulation. 
Experiments similar to those which I have described thus far were 
performed upon more than fifty tentacles and with fairly uniform 
results. What, now, is the further history of the closed end of the 
cut tentacle? 
Usually on the day following the operation it was noted that the 
nipple was distinctly smaller than at first. ‘This diminution in 
the size of the nipple progressed gradually and on the second day, 
in the majority of cases, the nipple had entirely disappeared. 
The closed end of the tentacle was then smoothly hemispherical. 
The point at which the nipple had disappeared was marked by a 
small whitish spot. During the period of retrogression of the 
nipple the whitishness and opacity of the hemispherical wall of 
the closed end gradually gave way to yellowishness and trans- 
lucency. No pore could be found in any case at the point where 
the nipple had disappeared. Even the whitish spot which at first 
marked this point gradually faded away in the next few days. 
Within the longest period that any one tentacle was kept under 
observation=—about seven days—-there were no signs of regener- 
ative activity at the closed cut end nor was there any very con- 
spicuous regulatory change in the proportions of the tentacle. 
In some cases it seemed to me that the repaired stump was longer 
than at first and that its distal end had become somewhat more 
tapering, like that of a normal tentacle. But the change, if any, 
was very slight and [ undertook no measurements. 
Experiments similar to those which have been described were 
made also upon specimens of Aiptasia whose dimensions were 
approximately as follows.—Height of column, 45 mm.; diameter 
of disc, 40 mm.; length of tentacles, 50 to 55 mm.; diameter of 
largest tentacles, 2.5 to 3 mm. ‘These tentacles were of nearly 
uniform diameter from base to tip instead of tapering as in Condy- 
lactis. As these dimensions show, this actinian was much smaller 
than the individuals of Condylactis which were used. The ten- 
tacles of Aiptasia have extremely thin filmy walls, which are almost 
