340 T. H. Morgan and Abigail C. Dimon. 



idea of the distribution M'ithin the worm. This was done in the 

 following experiment. 



Experiment 6. Lumbricus terrestris. Both electrodes applied 

 to the surface. The zero point of the galvanometer was 26.9, 

 and the electrodes varied from 26.7 to 22.0 after the third read- 

 ing, when they were regulated to 24.3, and at the end registered 

 only 26.0. The readings of the galvanometer were as follows: 



One electrode at anterior end, the other 



near 32.0 Head end negative 



One electrode at anterior end, the other 



at middle 30.0, then up, off scale. 



Head end negative 

 One electrode at anterior end, the other 



at posterior end 16.0 " " positive 



One electrode at posterior end, the 



other at middle 28.0 Tail end positive 



One electrode at posterior end, the 



other near i8.oi ,, ,, 



negative 



22.5^ 



It is difficult to explain these data so that they are consistent. 

 There Is no one point that has a high potential relative to all 

 others, though the deflections are sufficiently strong to indicate 

 that they are not due to variability In the electrodes themselves. 

 The variation may perhaps be due partly to local muscular con- 

 traction and partly to the excretion of slime at points on the sur- 

 face, for in Allohophora, where the body cavity fluid extruded 

 through the dorsal pores is yellow and noticeable. Its excretion 

 was observed to have a great effect upon the deflection of the 

 galvanometer. 



Different worms, too, show the greatest differences as to their 

 reactions when electrodes are touched to different parts of their 

 surface. In general, the two ends tend to have a lower potential 

 than other parts of the surface, and the middle tends to have a 

 higher potential with respect to points on either side of It. At 

 the girdle and at the fifteenth segment, however, the results are 

 more definite, as Is shown in the two following experiments. 



