98 G. H. PARKER 



often appears in a partly contracted tentacle as the internal 

 pressure increases shows that the applied pressure itself is a 

 stimulus to contraction (Rand, '09, p. 206). 



If then, the contraction of a severed tentacle is not due, simply 

 to a release from pressure, it may depend upon some influence 

 emanating from the stump of the tentacle or from the polyp as a 

 whole, which influence on being interrupted by the cut allows the 

 tonus of the tentacular muscles to exert itself unrestrainedly. 

 To test this hypothesis, tentacles were partly cut through about 

 midway their length and then allowed to come to a condition of 

 quiescence. Such tentacles became normally expanded and 

 elongated proximal to the cut but were somewhat contracted 

 distal to it, the cut itself exhibiting a well marked lateral pucker. 

 Such tentacles, if stimulated vigorously at the base, would ex- 

 hibit longitudinal contractions not only in the basal portions but 

 also to some extent in the portions distal to the wound. It thus 

 appears that the contraction of the distal part of a tentacle is 

 not overcome even through the connection of this part with the 

 proximal part by a bridge of tissue capable of transmitting im- 

 pulses from the polyp or basal part of the tentacle to the periph- 

 eral part of this organ. 



If the contraction of the severed tentacle is not due to loss of 

 pressure, or loss of a proximally located influence inhibiting ten- 

 tacular tonus, it is most probably due to the influence of the cut 

 itself. It is well known that wherever an actinian is injured the 

 muscular tonus of the given region is greatly increased and it is 

 therefore not surprising that on cutting off a tentacle the whole 

 organ should contract in a more or less permanent way. That 

 this is the probable explanation of the partial contraction of a 

 severed tentacle is seen from the fact that if such a tentacle is 

 firmly tied at its base, whereby its injury is considerbly increased, 

 it becomes permanently still more contracted in that the tonus 

 of its neuromuscular mechanism is appreciably increased. 



On the assumption that the partial contraction of the severed 

 tentacle had an operative source, I tried to avoid this difficulty 

 by anesthetizing the base of a tentacle so as to obtain a non- 

 responsive part to cut and tie and leave the greater part still 



