Physiological "Polarity" and Electrical Polarity. 341 



Experiment J. Lumbricus terrestrls. Zero point of galvanom- 

 eter, 28.6; deflection caused by electrodes to 30.5. 



One electrode at girdle, the other anterior 



to it, and near 20.5 Girdle negative 



One electrode at girdle, the other posterior 



to it, and near 39.0 " " 



Experiment 8. Lumbricus terrestris. Zero point of galvanom- 

 eter, 28.6; deflection caused by electrodes to 30.0, at end of 

 experiment. 



One electrode at 15th seg- 

 ment, the other ante 

 rior to it and near. . 29. S 15th segment negative, probably 



One electrode at 15th seg- 

 ment, the other poste- 

 rior to it and near. . . .31.5 " " " 



The girdle is definitely of a lower potential than the surface 

 near it, anterior or posterior, and this was found to be the case 

 for four worms tested. At the fifteenth segment the difference 

 was not so great, and though this region was negative with respect 

 to a surface posterior to it, with respect to one anterior it was only 

 very slightly, or, perhaps, not at all so. In another worm the fif- 

 teenth segment was evidently positive with respect to a surface an- 

 terior to it. 



ELECTRODES APPLIED AT TWO TRANSVERSE SECTIONS. 



Experiment 9. Lumbricus terrestris. Pieces cut out from 

 worm. The zero point of the galvanometer was 27.3. The 

 electrodes deflected it to varying amounts. In two cases, namely 

 the fourth and the seventh readings in the table, where the elec- 

 trodes deflected the galvanometer to 26.1 and to 29.5, respectively, 

 these deflections come near the readings given by the worm. In 

 the other cases it is not necessary to take deflection caused by the 

 electrodes into account, since they would not affect the direction of 

 the reading. The data are as follows : 



