122 THE ELEMENTARY NERVOUS SYSTEM 



tacles reproduce very closely the behavior of the nor- 

 mally attached tentacles. 



In response to slight or to vigorous mechanical stimuli 

 the severed tentacles reproduce in a most striking way 

 the movements of the attached ones under like stimula- 

 tion. When an attached tentacle is gently touched on 

 one side midway its length, the tentacle as a whole con- 

 tracts but without much bending. If it is touched on the 

 tip, the response is mostly a terminal waving back and 

 forth. If it is stimulated on one side near the base, the 

 contraction is chiefly basal and on the stimulated side. 

 These responses are reproduced quite clearly by isolated 

 tentacles. Thus the responses of the two classes of ten- 

 tacles to localized stimuli are strikingly similar. 



If a small amount of a 1 per cent, solution of acetic 

 acid is discharged on an expanded severed tentacle, the 

 tentacle contracts quickly with a curious appearance as 

 though it were withering. After it has been washed with 

 seawater, it may be distended again in about three to 

 four minutes. A second and a third response have been 

 elicited from such tentacles and these responses repro- 

 duce most strikingly the movements of attached tentacles. 

 To a tenth per cent, solution of acetic acid both classes 

 of tentacles show a slight local shortening. To a hun- 

 dredth per cent, solution they respond by a slight curv- 

 ing. To a thousandth per cent, solution neither kind of 

 tentacle shows any response whatever, as is also the 

 case when pure seawater is discharged on them from 

 a pipette. 



To seawater discharged on the tentacles from a small 

 pipette, no noticeable response is made by either class, 

 but to seawater containing the juice from a crushed mus- 

 sel, the attached tentacle exhibits active writhings often 



