PHYSIOLOGY OF REGENERATION IN TUBULARIA. I 55 



from the oral end accelerated basal development, for more of it 

 would be shut off in longer pieces, although not proportionally 

 more. The new experiments showed that in some cases the 

 pieces ligated nearer the basal end developed as soon as those 

 ligated more orally. Moreover the ligature itself if too near 

 the basal end may interfere with development there. It appears 

 then that it is still unsafe to draw any conclusions from these 

 experiments. 



Stolon Formation. 



Stolons develop after several days in a small percentage of 

 cases from the basal ends of pieces lying on their side in the dish. 

 More often the basal ends produce heteromorphic polyps. The 

 absence of stolons from the oral ends was first noted by Loeb. 

 The potentiality to produce stolons must of course be present 

 throughout the piece, since they may form from basal cut ends 

 at any level. I attempted in the following way to produce them 

 at the oral ends by first tying pieces so that basal polyps or 

 primordia appeared, and then by cutting off the piece behind the 

 ligature. The presence of the basal polyp might be imagined to 

 make the conditions favorable for the development of oral stolons. 

 This would certainly be the expectation if the polarity of the 

 whole piece is reversed as Loeb supposed. In no case were 

 oral stolons produced in this way, even when the pieces w r ith 

 basal polyps were cut off near to the polyps. 



In one case the pieces were cut off below the ligature 10 hours 

 after tying. After 48 hours from the beginning there were 3 oral 

 primordia and no basal. Other pieces had been cut off after 24 

 hours (when the ligatured controls showed 10 of 27 pieces with 

 basal primordia). All 14 pieces showed oral primordia, and 8 

 of these had primordia also at the basal end more developed than 

 those at the oral end. The presence of basal primordia had not 

 delayed the development of oral primordia. In fact the latter 

 appear to have been accelerated — not however necessarily owing 

 to the basal development but to other changes in the piece. 



It is probable that external factors combined with the internal 

 factor called polarity has something to do with stolon-formation. 

 But even when the oral ends of pieces with basal polyps were 



