Wound Reparation—A ctinian Tentacles 223 
havior exhibited by the smaller and simpler ccelenterate struc- 
tures. In the earthworm, with much greater diversity of struc- 
ture, the reparation process is still more complex than it is in the 
actinian tentacle. The immediate closing of the wound in the 
earthworm is effected by contraction of the the body-wall muscu- 
lature and the formation of the cicatricial plug. Therefore these 
acts are, in a sense, the physiological equivalent of the muscular 
control of the cut end of an actinian tentacle. ‘The covering of 
the surface of the earthworm cicatrix by migration of epidermal 
cells is represented in the actinian tentacle by those internal read- 
justments which bring about the relief of the muscular control of 
the cut end and effect the structural closing of it, for these are the 
processes which, similarly in the two organisms, reéstablish normal 
relations and conditions of tissues. Only the impaired form then 
remains to be corrected, so far as the organisms are able, by regen- 
eration. 
It must not be inferred that the foregoing discussion purports 
in any sense to explain what happens in the actinian tentacle. 
My aim has been to describe and to analyze the events in the hope 
that the so doing may enable us to see a little more clearly the nature 
and scope of the phenomena which remain to be explained. 
POLARITY 
Thus far we have described the behavior of only the distal cut 
end of a tentacle. If now we consider what happens at a proximal 
cut end we shall immediately find some differences which are note- 
worthy. The immediate reactions of an excised tentacle of Con- 
dylactis are described on p. 203. The characteristic features of 
the behavior of the proximal cut end are as follows. ‘The cut 
edges bend inward slightly within a few seconds after the cutting. 
This inbending very gradually becomes more decided and as it 
does so the walls of the proximal end develop deep folds or wrinkles. 
Figs. 6a and 6) show the condition of proximal cut ends about one 
and a third hours after the cutting. Fig. 12 represents the con- 
dition of three consecutive fragments of a single tentacle about 
one hour after the cutting. Fig. 13 shows two pieces of a tentacle 
