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



only two readings were made, one giving a very slight result, the 

 other deflecting the galvanometer to 5.2. 



If we attack this subject by another method, namely, by mak- 

 ing a direct comparison between two freshly-cut ends on one worm, 

 the results are equally indefinite. When five or six segments were 

 cut from each end of the worms, of a series of fifteen readings on 

 different worms made with one electrode at the anterior-cut end 

 and the other at the posterior-cut end, the posterior end was posi- 

 tive in eleven and the anterior end positive in four. When the 

 worm was cut through the middle and at the posterior end, the 

 posterior end was positive in three cases, and the middle in one 

 case. When the cuts were made through the middle and anterior 

 end, in five cases the middle was positive, and in two the anterior 

 end positive. From these considerations it would therefore ap- 

 pear that no invariable connection between rate of regeneration 

 and electrical polarity exists in the earthworm, at least as measured 

 on a freshly cut surface. 



From the foregoing experiments we conclude : 



( 1 ) That a freshly cut end of an earthworm is generally nega- 

 tive with respect to a near-lying uninjured surface. 



(2) That the freshness of the cut surface has an Important in- 

 fluence In determining the amount of difference of potential. 



(3) That the result is often complicated by the presence of se- 

 cretions or exudations on the surface, or by the presence of certain 

 organs at the cut end, or by the contractions of the worm, etc. 



(4) That in the region of the girdle and also in the region of 

 the fifteenth segment (near which the crop and gizzard lie), the 

 results are often different from those elsewhere. 



(5) That there Is no apparent relation between the differences 

 In potential at freshly cut surfaces and the kind of regeneration 

 (head or tail) that occurs. 



(6) That cut surfaces from which heteromorphic growth 

 would take place show the same sort of differences in potential 

 as those from which orthomorphic regeneration occurs. 



(7) That the differences in potential present when a cut sur- 

 face Is exposed can probably be accounted for by the chemical 

 changes taking place at the surface; and these need have, and do 



