PHYSIOLOGY OF REGENERATION IN TUBULARIA. I 53 



been delayed if a larger basal piece had been cut off, but un- 

 fortunately no experiments were made to show this. It is how- 

 ever probable that the changes are especially confined to the basal 

 region near the cut end and are less at more distant points. 



The converse experiment consisted in cutting off pieces of the 

 oral end. The basal end was tied in the first experiments, although 

 this is not necessary, because tying the basal end does not accel- 

 erate the oral development. 



When the oral ends were cut off after ten hours the six pieces 

 showed, 23^ hours after the beginning, 3 faint oral primordia. 

 The 6 controls had all oral primordia. After 72 hours all the 

 6 cut-off pieces had oral polyps, while only two of the controls 

 had oral polyps and two oral primordia. The cut-off pieces 

 appear to have fully caught up with the controls. The data are 

 indeed very few, but the results confirm earlier ones thus 

 obtained. In order to see whether when both ends of a piece 

 are closed any processes take place that accelerate development 

 if the ends are later exposed, the following experiment was 

 made. Both basal and oral ends were tied and later the piece 

 was cut in two in the middle. In order to ascertain the rate for 

 normal regeneration control pieces were cut off and left open. 

 These developed oral primordia after 19 hours in 9 of 14 pieces. 

 These pieces were then also cut in two in the middle. After 55 

 hours (from the time of tying) the basal halves of the tied and 

 cut set produced 5 oral primordia, while of the control 6 had 

 oral primordia, 2 basal primordia, and one was a double piece. 

 The results indicate that when a piece is closed at both ends no 

 changes take place in it that accelerate the development in the 

 middle of the piece. The result may throw some light on the 

 preceding experiment, and if so, shows that the changes that there 

 took place were due to the open end. 



Is Basal Development Accelerated by Allowing the 

 Oral End to Begin its Development ? 



In one of my previous papers a I gave the results of an experi- 

 ment in which pieces were tied near the oral end after having 

 been left open for several hours. The experiment was made in 



1 Joum. Exp. Zoology, II., 1905. 



