334 T. H. Morgan and Abigail C. Dimcn. 



flow of blood from cut surfaces, the excretion of slime from the 

 skin, local or general muscular contractions might all tend to af- 

 fect the results. Such effects could sometimes be distinctly seen 

 in an increase or decrease in the deflection of the galvanometer. 

 It seemed possible that the presence or absence of food in the 

 digestive tract might in itself or by stimulating the flow of digest- 

 ive fluids influence the distribution of electric potential, but this 

 was not observable from tests made with worms that had been 

 starved for several days. 



Experiment i. Lumbricus terrestris starved two days.^ Cut 

 ends anterior at several levels. The left hand electrode was ap- 

 plied to the cross-section and the right hand electrode to the dor- 

 sal surface one-third to one-half inch behind the section. The 

 zero point of the galvanometer was 27.1, and the effect of the 

 electrodes varied, deflecting it between the limits 26.1 and 29.3, 

 both of which deflections are less than those caused by the worm 

 itself, and may therefore be disregarded. The galvanometer 

 readings at different levels on the worm were as follows : 



Cut at fourth segment. ... a. 45.0+ (off scale) Surface positive 



Cut at fourteenth segment. b. 35.5 



Successive sections between 1 c. 45.0+ (off scale) 



the fourteenth segment J d. 42.5 



and the middle of the 1 e. 40.0 



worm I r. 43.5 



Successive sections posterior I g. 11.5 Cut end positive 



to the middle J h. 34.0 Surface positive 



[ 1- 32.2 



The readings are all definite and represent the state of affairs 

 in a majority of the worms examined. From these data it will 

 be seen that when a worm is cut in two it is found that in the 

 anterior regions of the worm the anterior cut end of the posterior 

 piece is negative with respect to the near-lying surface. In the 

 posterior regions of the worm where there was more variation the 

 differences in potential were usually less, and sometimes reversed in 



^Since the results seemed not to be affected by the absence of food from 

 the digestive tract, this specimen was chosen because a more complete series 

 of sections were made from it than from any unstarved worm. 



