Physiological "Polarity" and Electrical Polarity. 335 



direction. Irregularities were often observed at about the fif- 

 teenth segment, where the male reproductive organs open to the 

 exterior and the crop-gizzard region begins. Irregularities also 

 occurred at the girdle. In the worm used for this experiment 

 negative deflection of the galvanometer occurred only once, im- 

 mediately behind the middle of the worm, but the positive deflec- 

 tion was diminished at the fourteenth segment and at the other 

 cut ends in the posterior regions of the worm. 



Experiment 2. Lumbricus terrestris. Cut end posterior. The 

 zero point of the galvanometer was 27.3, and the electrodes 

 caused a deflection to 27.5 at the beginning and to 30.0 at the end 

 of the experiment, which does not affect the sense of the deflection 

 for any reading. The galvanometer record for the different levels 

 is as follows : 



[a. 28.0 Cut end positive 

 Successive sections from the posteriori L. 19.5 Surface positive 



end to the middle of the worm. . . c. 23.0 



I d. 23.5 ;; ;; 



Section about the middle e. 24.0 



Section anterior to middle f. 25.0 



Section at 23rd segment g. 39.0 Cut end positive 



Section at 15th segment h. 20.0 Surface positive 



Section anterior to 15th segment. ... i. 17.7 " 



The surface has a higher potential than the cut end at all but 

 two levels, one where only a few segments are cut oflf from the pos- 

 terior end, where the difference of potential is small; and the other 

 at the twenty-third segment. The reversal of current at the extreme 

 posterior end occurred in all the worms in which a full series of 

 sections was made. The twenty-third segment is between the fif- 

 teenth segment and the girdle. In this region two other worms 

 showed possible cases of reversal of current, though the more usual 

 condition was that the current was reversed at the fifteenth seg- 

 ment or at the girdle, or at both points, but between them flowed 

 in the same direction as in the rest of the worm. The worm used 

 in this experiment showed the same distribution of potential that 

 is found in a majority of individuals, except at the fifteenth seg- 

 ment, where one-half of the worms tested showed a reversal of 



