PRIMORDIUM IN RELATION TO STRIPE PATTERN 183 



Such cases also illustrate another point. In the normal primor- 

 dium site the anlage appears in and across the fine-stripe area near 

 that part of the cell which carries the broadest pigment stripes. 

 Broad and fine stripes as well as the kinetics between them are of 

 course homopolar and presumably in intimate continuity since the 

 wide-stripe zone is continually transforming into the fine-line zone 

 by stripe sphtting. If there is interaction between the two areas, 

 this would seem to be an action at a distance and not something 



C. Same, implanted heteropolar. The anlage now forms on 

 the other side where the stripe contrast is greatest. Initially, the 

 ectopic anlage bends at its posterior end, but later the polarity 

 of host predominates and mouthparts are induced at the other 



end, incomplete and of reversed asymmetry. 



D. Fine-line zone of host split by an implanted sector of wide 

 striping. Three anlagen are formed in correspondence to the 

 three loci of stripe contrast : one in the host primordium site {x) 

 and one on each side of the graft. Adjacent anlagen join to form 



V-primordium which may or may not produce mouthparts. 



E. Pair of stentors grafted by wound surfaces from removal 

 of the heads develop primordia in the normal sites but extending 

 around the suture where wide abut narrow stripes in heteropolar 



orientation. 



F. Head of one stentor replaced by fine-line zone of another, 

 grafted at 90°. Anlage extends from primordium site into the 



newly created l.s.c. 



G. Anterior half rotated 180' on posterior. Anlagen appear 

 in separated halves of the primordium site and are joined by 

 extension which may run halfway around the specimen where 



wide stripes abut fine stripes end-to-end. 

 H. Left half rotated 180° on right. First sketch shows anlage 

 formed in normal primordium site and extended to new l.s.c. 

 where fine stripes meet wide-stripe area of the other half. Second 

 drawing shows third primordium induction in minor l.s.c. 

 produced on the opposite side. 

 I. Wide-stripe patch implanted transversely into fine-line 

 zone of host develops an extra primordium, which however forms 

 no mouthparts, probably because too distant from posterior pole. 

 J. Aboral half, folded upon itself, develops regeneration 

 primordium where the widest stripes lie next to their narrowing 

 prolongations. 

 K. Summary diagrams showing primordium formation 

 (indicated by bar) to be correlated with loci of contrasting 

 pigment stripe widths but independent of the orientation of 

 those stripes. (After Tartar, 1956a, b.) 



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