MOVEMENTS OF TENTACLES IN ACTINIANS 109 



though this question is obviously a relative one, when the activi- 

 ties of an isolated actinian tentacle are compared with those of 

 the separate appendage of a higher animal there seems to me 

 not the least ground for the opposition raised to the view of the 

 high degree of organic independence of the tentacles from the 

 rest of the body of actinians. 



SUMMARY 



1. The severed tentacles of Condylactis may be suspended in 

 seawater with least disturbance to themselves by means of a 

 small metal hook. 



2. Under such circumstances they can be inflated by running 

 water into them till they have attained about two-thirds their 

 natural length. In this condition they are under a fluid pres- 

 sure very nearly that which was natural to them and not greater 

 than a few millimeters of water. 



3. If this internal pressure is increased much beyond that at 

 which the tentacle expands to about two-thirds its former 

 length, the tentacle will contract vigorously and discharge much 

 of the contained seawater. 



4. The slightly contracted state of the expanded, excised ten- 

 tacle is not due to lack of pressure, nor to the absence of inhib- 

 itory influences from the rest of the polyp, but to the cut at 

 its base, which increases the tonicity of its neuromuscular mech- 

 anism. 



5. Excised tentacles when stimulated by mechanical means, by 

 food, or by chemicals react in essentially the same way as attached 

 tentacles do. Excised tentacles are feebler and less precise in 

 their reactions than attached tentacles are, a difference due to 

 their part'y contracted state, which in turn is dependent upon 

 operative complications. 



6. Stimuli when applied to the ectoderm of a tentacle are fol- 

 lowed quickly by a muscular response; when applied to the ento- 

 derm they are followed slowly by the same form of response. 

 This difference is due to the fact that the entodermal surface is 

 not receptive and that stimulating substances applied to that 



