RECONSTITUTION IN DISARRANGED STENTORS 229 



The operation of rotating anterior on posterior halves was first 

 used to demonstrate that primordium formation can occur in such 

 loci of stripe contrast (Tartar, 1956a), but it was also observed that 

 stripe disharmonies were resolved by resorption of the anterior 

 striping and extension of the posterior to take its place. If regenera- 

 tion was delayed by leaving the membranellar band intact, the 

 forward resorption of the anterior ectoplasm occurred so rapidly 

 that when an anlage was formed it appeared only in the primordium 

 site from the posterior half (Fig. 66a). Even when regeneration was 

 not induced, anterior striping could be dissolved as it was replaced 

 by the posterior (b). Alternatively, in some cases in which regenera- 

 tion was not induced the striping of anterior and posterior halves 

 appeared to interpenetrate, parts of both anterior and posterior 

 striping being preserved. 



Later it was found that grafts with this astonishing interpenetra- 

 tion of stripes could be produced quite readily (Tartar, 1959b). 

 Figure 66c shows how the fine line zone or primordium site of 

 each half plows through the striping of the other half as it extends 

 in length and gradually reaches the opposite pole. Specimens with 

 two good primordium sites which reorganize as doublets are 

 therefore generally produced. Later readjustments, in which the 

 fine lines of either side become wider, then lead to eventual 

 recovery of the single form. In one instance the animal divided. 



C. Stentor cut in half, fine-line zones interpenetrating next 

 day to reach opposite poles of the cell, with result that two loci 

 of stripe-width contrast are extended and specimen becomes a 



doublet. 



D. Front and back views of dividing specimen with interpene- 

 trating stripes, showing how fission line forms indiflferent to 



suture between stripes of the rotated halves. 



E. Racial difference in interpenetration of striping. Same 

 operation as in c, but with EUetsville race. First sketch: two 

 days after operation with striping still unchanged. Second : i ith 

 day, with striping now running pole to pole forming two primor- 

 dium sites, one with reversed asymrrietry and therefore producing 



anlagen which gave incomplete stomatogenesis. 



F. Stage-3 divider cut with anterior part larger. Specimen 

 reorganizes instead of dividing, with only anterior portion of the 

 primordium developing, the posterior part resorbed. Posterior 



striping is gradually resorbed as anterior stripes extend. 



