652 RAYMONP TRAUL. 



rjL pel' cent. — Neg-ative reaction, but dccidctlly less pro- 

 nounced tlian Avitli preceding concentrations. Does not 

 cause any movement whatever in resting specimen. 



■5L. per cent. — Negative reaction, less strong than in pre- 

 vious cases. In some cases positive reaction. Noticeabk? 

 tendency to give slight positive reaction just before tlie 

 definite negative response. 



_i_ per cent. — Well-marked positive response. 



Summary. — The same conclusions are to be drawn from 

 the experiments on organic acids as from those on mineral 

 acids, viz. that to strong concentrations of a given substance 

 the negative reaction is given, wliile weak concentrations 

 cause a positive response. Oxalic acid is rather peculiar in 

 that it appears to furnish in all concentrations a stimulus of 

 the proper quality to induce the positive response, but is at 

 the same time excessively harmful in any above the v/cakest 

 solutions. 



Alkalies. 



Sodium Hydrate, i per cent., ^V P^^" cent., and ^Vr P^'" 

 cent. — Immediate strong negative response. Specimens 

 turn away very sharply. In ^rV P^i' cent, the reaction is 

 slightly weaker than in the other two. 



i_ per cent. — Negative reaction. Stimulus applied to pos- 

 terior end of body is sufficiently strong to cause ci-awling 

 movement. 



_L. per cent. — Weaker negative reaction. Suflficiently 

 strong to start resting animal into movement. 



yi^ per cent. — Weak negative reaction. Ineffective on 

 I'esting worm and on posterior end of body of moving 

 specimen. 



^^rr P^^' cent. — Veiy weak negative response. In one 

 specimen sharp positive reaction ; performs whole food re- 

 action on the end of the tube. 



■^{yj- per cent. — Positive reactions from all s]K>cimcns. The 

 complete food reaction is given. 



