THE PHYSIOLOGY OF REGENERATION 



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limited, and is usually less than the number removed, but the 

 processes governing the length and number of segments of the 

 regenerant portion are as yet uncertain, though two hypotheses 

 may be mentioned. 



Morgan and Dimon (1904) investigated the electrical properties 

 of the earthworm body, observing that the mid-region of the body 



Fig. 36. Lumbriculus variegatus : sagittal section of a regenerating 

 tail (1 day old), the portion ventral to alimentary canal, ec. 

 epidermis ; en. endoderm of lower wall of hind end of alimentary 

 canal; ch, giant fibre cut in section; chl, chloragogen cell; n, neo- 

 blasts (from Stephenson, 1930). 



was more electronegative than the rest of the body. They also 

 found that when the animal was divided the cut surface was nega- 

 tive with respect to the adjacent tissue. Watanabe (1927) also found 

 that the electrical potential of the body of Perichaeta varied 

 from place to place, being greatest anteriorly, least in the mid-body 

 region, and rising again towards the rear end. Similar observations 



