104 G. H. PARKER 



tration of the wall by acid was obtained in 45 seconds and in 

 55 seconds. 



To be certain that the reddening of the litmus paper was not 

 due to any leakage through the pores at the end of the tentacle, 

 the experiment was repeated with a tentacle the tip of which 

 was tied. This brought about an extreme contraction of the 

 tentacle. Nevertheless the transfusion of acid through the wall 

 of the tentacle was observed in from two to two and a half 

 minutes. The longer period needed for the transfusion in this 

 instance, as compared with that in tentacles not tied at the tip, 

 is doubtless due to the increased thickness of the wall of the 

 tentacle in contraction. It therefore seems not improbable that 

 the response of a tentacle to chemical stimuli discharged into 

 its interior is not due to the stimulation of entodermic recep- 

 tors but to the transfusion of the substances through the wall of 

 the tentacle to the ectoderm, where a normal external stimula- 

 tion probably takes place. 



Another method of testing for an entodermic nervous system 

 is as follows. It has already been stated that a suspended iso- 

 lated tentacle will contract when a one per cent solution of 

 quinine hydrochloride is discharged on it or into it; quickly in 

 the former case, more slowly in the latter. If such a tentacle 

 is bathed externally in a preliminary way with a half per cent 

 solution of cocaine hj^drochloride, after five to eight minutes it 

 will no longer respond to the quinine solution. If now this so- 

 lution is at once discharged into the interior of the tentacle 

 there is likewise no response. Thus the tentacular entoderm 

 does not appear to be a receptive surface for internal stimuli, 

 but merely transmits in a physical way substances which 

 'become effective stimuli only after they reach the ectoderm. 

 The view that the tentacular entoderm is not a receptive sur- 

 face and may contain no nervous tissue whatever, is supported 

 by the fact that the muscles responding to all the stimuli ap- 

 plied to the interior of the tentacle are the distantly located 

 longitudinal muscles, not the near-by circular muscle. 



These various lines of evidence naturally raise the question 

 whether there is after all in the entoderm of the actinian ten- 



