472 E. J. LUND 



results. These have been summarized by Morgan,^ Loeb,^ 

 Child/ and others, and need not be referred to at this time. 

 However, so far as I am aware, no successful attempt has been 

 made to study the effect of the direct electric current upon the 

 axial orientation of organs during regeneration. 



The experiments given below will, I believe, conclusively 

 show that polarity in regenerating pieces of the stem of Obelia 

 commissuralis may be completely controlled and established 

 at will by the action of a direct electric current of proper den- 

 sity, provided the material used has the capacity to regenerate 

 in the absence of the electric current. 



In a previous paper on form regulation of a unicellular or- 

 ganism (Bursaria) the following facts regarding polarity and 

 reversal of polarity in the cell were found. ^ First, reversal of 

 polarity often occurred in cut halves of cells undergoing re- 

 generation, with the result that typical heteromorphic indi- 

 viduals arose. Second, it was found that a normal cell would 

 occasionally transform directly into a heteromorphic individual 

 when the former was isolated from the native wild culture 

 medium and placed in tap-water or a medium made of a weak 

 solution of Horlick's malted milk in tap-water. Third, it was 

 also found that the signs for this heteropolarity in the cell could 

 be reduced to simply a reversed heat of the cilia, without the 

 presence of the complicated oral apparatus aud mouth. Several 

 intermediate degrees of this reduction of structural differentia- 

 tion were observed, from two perfectly normal and fully 

 differentiated cells attached end to end to an oval-shaped mass 

 of protoplasm with bipolar beat of the cilia. An example of this 

 is shown in figure 1, a, b, c. The conditions for the appearance 

 of these heteromorphic individuals were of course obscure, but 

 at that time I called attention to the similarity of the direction of 

 beat of the cilia in these individuals to the direction of the ciliary 

 beat in Paramecium when under the influence of the direct 



2 Morgan, T. H., Regeneration. 1901. The Macmillan Co. 

 ' Loeb, J., Studies in general physiology, part I. 



* Lund, E. J., Reversibility of morphogenetic processes in Bursaria. Jour. 

 Exp. Zool., 1917, vol. 24, p. 1. 



