Wound Reparation—A ctinian T entacles 229 
to secure a piece of tentacle onto the hydrostatic tube in orienta- 
tion the reverse of that of the preceding experiments—that is, to 
tie the distal end of the fragment onto the tube, leaving the prox- 
imal end free. I attempted to do so first with tentacles of Condy- 
lactis. After many trials | abandoned the attempt owing to the 
fact that the manipulation of the distal end of the excised tentacle 
induced such excessive contraction that the tentacle was reduced 
to a shapeless lump into which the glass tube could not possibly 
be inserted properly. But the very failure of this attempt demon- 
strated a striking physiological polarity, since it appeared that 
irritation of the distal end of a tentacle caused much more severe 
contraction than similar irritation of a proximal end. [I shall 
refer to this matter again. I then tried the same experiment on 
tentacles of Aiptasia. Of many attempts, only one succeeded. 
At the expense of much mutilation of the distal region of a large 
tentacle I finally secured it to the end of the glass tube. Within 
five minutes the tentacle began to stretch out a little although so 
sharply contracted in diameter that its lumen must have been 
practically closed. I then began applying internal pressure. 
Moderate pressures produced no change in the appearance of the 
tentacle. But under a pressure of about 80 mm. the contraction 
was partially overcome and the tentacle became distended. It 
elongated considerably and also swelled out laterally, but its free 
proximal cut end remained so much contracted that only a small 
pore-allowed the contained water to escape. The form of the 
tentacle under these conditions is shown in Fig. 17... A few min- 
utes later I cut a small fragment off the proximal end, thus obtain- 
ing a new cut surface lying at a slightly different region of the 
tentacle. Upon application of internal pressure the conditions of 
Fig. 17 were repeated. The removal of a second proximal frag- 
ment transferred the cut surface into a still more distal region of the 
tentacle and with perfect repetition of the preceding behavior. 
In this experiment the distention of the tentacle was certainly 
nothing more than the direct mechanical effect of the water pres- 
sure. But why did the free proximal end remain contracted ! 
Is this condition in any way comparable to that of the free distal 
cut end which closed and formed a nipple? I believe that it cer- 
