232 Herbert W. Rand 
cisely the intensity of the stimuli and the degree of the contractions, 
it was quite evident that the amount of contraction varied with 
the intensity of the stimulus—more particularly, that the stimuli 
which caused contraction on only the proximal side of the point 
of contact were upon the average less intense than those which 
caused contraction of the whole tentacle. | 
It is apparent, then, that there is a certain polarity in the effects 
of a tactile stimulus, in that motor responses are produced upon 
the proximal side of the point of contact more readily than upon 
the distal side of it. Some features in the behavior of cut tentacles 
are in accord with these facts. When a piece of tentacle is ex- 
cised the stump of the tentacle contracts proportionately much 
more than the piece which is cut off. If an excised tentacle 1s 
cut into two pieces the proximal piece contracts more and shows 
much more conspicuous motor disturbances than the distal one. 
(See p. 203.) Still further, I found it comparatively easy to 
ligate the proximal end of a tentacle onto the hydrostatic tube, 
but my efforts to ligate a distal end onto the tube were, with one 
exception, failures on account of the excessive contraction induced 
by cutting and manipulating the distal end. 
This behavior of the tentacle is strikingly similar to the behavior 
of worms as shown by the experiments of Norman (’00), who 
found that transection of a worm was followed by conspicuous 
motor disturbances in the portion of the animal posterior to the 
cut, while the anterior portion exhibited only slight response to 
the cutting, or none at all. 
In the beat of the cilia and in the reactions of tentacles to tactile 
stimulation and to cutting, we see a physiological polarity Under- 
neath it may lie some as yet undiscovered structural polarity. 
In the different forms of proximal and distal cut ends of fragments 
of an excised tentacle we have an instance of morphological 
polarity. Is there any significance in the fact that proximal and 
distal cut ends of a detached portion assume different forms? It 
seems to me obvious that there is. The distal cut end tends to 
assume the form and condition of the tip of a normal tentacle. 
This tendency is to be seen in the tapering form of the distal cut 
end and in its prompt closure, which is effected by the same 
