Wound Reparation—A ctinian Tentacles 213 
internal fluid pressure in relation to the form and activities of 
Cerianthus. 
As previously mentioned, the pieces of tentacle which had been 
detached from the column never exhibited a state of complete 
relaxation. ‘Their changes of form were always relative to a 
certain and considerable degree of persistent contraction in all 
dimensions. ‘This contraction was only partially, never completely, 
overcome by the artificial application of internal pressure, thus 
proving that the failure to attain full expansion was not due merely 
to the absence of the normal pressure of the gastro-vascular fluid, 
but rather to some lasting change in the tissues themselves oc- 
casioned by the cutting of the tentacle. However, as regards the 
behavior of the tissues at a distal cut end, whether the stump of 
tentacle was attached normally to the column or ligated to the 
pressure tube or not attached to anything, there was in one respect 
entire uniformity, namely in this,—that under conditions of gen- 
eral extension the distal opening became narrowed or quite closed, 
while under conditions of general contraction the cut end became 
more broadly open. ‘These rapid changes in the area of the open- 
ing certainly depend upon muscle action. Furthermore, this 
behavior indicates that a band of circular fibers at the cut end is 
working independently of other fibers and, to a certain extent in 
opposition to them. ‘Thus, when a tentacle elongates the circular 
fibers in general may not contract, as appears usually to be the 
case in a normal tentacle, or they may contract as sometimes 
noted in detached fragments of tentacles. However that may be, 
there is at a distal cut end a band of circular fibers which znvari- 
ably contract when the tentacle elongates and which may relax 
more or less when the tentacle shortens. ‘The more the extending 
tentacle becomes dilated under general relaxation of circular 
fibers, the more tightly closed is the distal end. ‘The nipple, then, 
results from the extreme contraction of a distal band of circular 
muscle fibers. 
The experiments have shown that in the course of a few days 
the nipple disappears, the cut end becomes completely closed, even 
lacking the terminal pore characteristic of a normal tentacle, and 
the whitish opacity indicative of contracted tissues fades away. 
