PRIMORDIUM IN RELATION TO STRIPE PATTERN I91 



is accomplished simply by a widening of the narrow striping so 

 that the contrast with neighboring areas disappears (see Fig. 58B). 

 Stentor graft complexes in general often show a waxing or waning 

 of supernumerary l.s.c, always tending eventually toward the 

 single form. 



Fig. 51. Resorption and formation of loci of stripe-width 

 contrast, a : Graft of 6 aboral halves without fine striping plus 

 one primordium site, b: Initial oral regeneration only from the 

 site with its maximum l.s.c. c: Reorganized now from three 

 primordia as fine striping multiplies in two sutures with minor 

 l.s.c. Original fine-line zone being resorbed. d: Re-reorganized 

 from the two new l.s.c. only, original l.s.c. nearly obliterated. 

 (After Tartar, 1956a). 



6. Exceptions 



The correlation between loci of contrasting stripe widths and 

 primordium formation is not without its puzzling exceptions. 

 Primordia have on rare occasions been observed to be formed 

 w^here no l.s.c. was evident, and still less frequently the primor- 

 dium appeared at some place other than the good primordium site 

 w^hich w^as present. These exceptions w^ere so few that almost all 

 of them can be presented in Fig. 52. In two cases of doublish or 

 mixed up stentors, as explained in the caption, the single or 

 secondary primordium appeared far from the major locus of stripe 

 contrast (a and b). Another case showed a primordium in the 

 primordium site but also another on the opposite side of the cell 

 where there was no significant stripe contrast (c). Other cases 

 showed primordium formations or extensions in regions where 

 the stripe widths were apparently uniform (d, e, f, g). A special 

 case was a double primordium with a single kinety or clear stripe 

 separating the two halves which also appeared in an area without 

 significant stripe contrast (h). 



