1 86 



THE BIOLOGY OF STENTOR 



length, anlagen formation reliably follows its contour. Yet when 

 the wide stripes were bent and the fine stripes not, the primordia 

 was normal and straight, confirming that the anlage comes from 

 the fine-line zone. Neighboring sectors of fine striping put in 

 wide-stripe areas usually result in V-shaped primordia. If short 

 and far anterior, such anlagen contribute only a section of mem- 

 branelles to the regenerant ; if long and extending posteriorly, well 

 formed mouthparts are generally produced at the angle, even 

 though this involves the co-operative coiling of two membranellar 

 bands in a way that does not naturally occur (see Fig. 411). When 

 a small patch of fine striping becomes surrounded by wide-stripe 

 areas the patch is encircled by a new membranellar band as a 

 continuous ring. Especially when in the form of a loop, such anlagen 

 still attempt to form mouthparts toward the posterior end but 

 these are never very complete (Fig. 41J). When in the form of 

 small rings, they contribute at most a section of membranelles 

 enclosing an extra oral pouch. Schwartz informed me (1958) that 

 the same occurs when small patches of wide striping find them- 

 selves surrounded by a fine-stripe area, and that this may occur 

 even though the patch is very small, suggesting to him that the 

 materials of the primordium probably do not come from wide- 

 stripe areas. Perhaps the case shown in Fig. 47F was of this origin ; 

 at least it carries the same implication. 



Fig. 48. Cases of primordia (x) curving in the wrong direction: 

 into the wide stripe area. A. In main portion of a graft of 12 

 coeruleus reorganizing on the fifth day. Only one of the anlagen 

 is abnormal and it formed only a short tube and no adequate 

 mouthparts. B. In a doublet stentor, but in this case the 

 abnormal primordium apparently formed good mouthparts 

 notwithstanding. 



