RECONSTITUTIONAL PATTERNS IN EXPERIMENT 421 



present rather than a determination of the patterns. Doubtless it does 

 alter gradients that may be present, and perhaps with proper procedure 

 it may determine axiate pattern. 



Single cells of the red alga Griffithsia hornetiana, subjected to electric 

 current, develop rhizoids toward the anode, irrespective of the original 

 polarity; and chromatophores migrate toward the anode. This localiza- 

 tion of rhizoid formation is regarded as resulting from migration of charged 

 particles (Schechter, 1934). 



Internodes, that is, pieces of stem between successive branches, of the 

 hydroid Ohelia in sea water usually give rise to hydranth-stem axes at 

 both ends, development distally being more rapid than proximally. In 

 this hydroid reconstitution involves outgrowth of tissue from the ends, 

 rather than reorganization without outgrowth, as in Tuhularia and Cory- 

 morpha. Electric current of proper density, flowing longitudinally, deter- 

 mines a high frequency of hydranth-stem development on the end toward 

 the anode and delays or completely inhibits similar development at the 

 end toward the cathode (Lund, 1921c). With certain current density, hy- 

 dranth development is inhibited at the cathodal ends of Tuhularia pieces, 

 as reported by Lund for Obelia; but with a sufficient increase in current 

 density the inhibition is reversed and becomes greatest at the anodal 

 end. In Eudendrium pieces inhibition is greatest at the cathode end, 

 but in Pennaria pieces it is greatest at the anodal end with all current 

 densities used (Barth, 1934a). According to Barth, effect of current in 

 these cases appears to be largely a difference in degree of inhibition at the 

 two ends, although in Tuhularia pieces hydranth frequency is higher at 

 the anodal end in current densities which determine cathodal inhibition 

 than in controls. This, however, may result from the cathodal inhibition, 

 for it has been repeatedly shown that hydranths develop more rapidly at 

 proximal ends of pieces when distal hydranth development is inhibited. 



Strictly speaking, electric current, like the oxygen differential, deter- 

 mines in these cases which of two possible polarities shall express itself 

 in development. The activation following section determines the polarity 

 or polarities in the piece, and the current obviously affects the activation 

 at cathode and anode differentially or in different degree. The result is, 

 of course, determination of polarity of the piece, but perhaps the current 

 should be regarded as selecting the polarity rather than as determining it. 

 Whether electric current can determine a new polarity in hydroid tissue 

 independently of a cut end has not yet been discovered, but that it can 

 do so seems highly probable. Undoubtedly, a sufficient difference in many 



