Experiments en Polarity in Tiibularia. 577 



in the series of short pieces. So much irregularity occurs, 

 however, that- it is doubtful if the result establishes any definite 

 conclusion. 



In the first series the long pieces were cut into short pieces 

 (5-6 mm.) after 6, 15, 16, 20, 24 hours. This series, kept in a 

 warmer room, regenerated much faster than the second series. 

 The figures indicate the sequence of the oral polyps, and x indi- 

 cates an aboral hydranth. 



After 6 hours, as shown in these tables, the intervals between 

 the time of emergence of the polyps in succeeding pieces are not 

 very different, although, as a rule, the piece nearest the oral end 

 developed first. After 15 hours the irregularity is so great that 

 no conclusion can be safely drawn. The following series, after 

 16 hours, shows a slightly regular sequence from oral to aboral 

 end. After 20 hours a greater regularity is observable, and it 

 will be recalled that at about this time the primordium of the 

 polyp can usually be seen. Also after 24 hours the sequence is 

 more marked. 



In the next series the intervals were different, the short pieces 

 averaged less in length and the development was very much re- 

 tarded, largely due to lower temperature, as compared with the 

 preceding series. The figures indicate observations 24 hours apart. 



In the check series the pieces from the same stem developed in 

 about the same time, although in some cases the more basal 

 pieces were later. In the third row the most aboral piece pro- 

 duced a stolon and later its end developed a polyp. The 8-hour 

 series is not good, but so far as it goes, it shows no more than the 

 check series. The 12-hour series is not different from the pre- 

 ceding. The 18-hour series shows no special influence of the 

 changes that were going on at the oral end of the piece before it 

 was cut into small pieces. The first two rows developed very 

 slowly. The 24-hour series developed much better, i. e., earlier 

 than the preceding, but while in most cases the oral pieces de- 

 veloped first, there was not a relatively great difference between 

 these and the more aboral pieces. After 36 hours there is a 

 decided difference shown by the oral pieces, the remainder of each 

 set being much the same, and this is also true for the 48-hour series. 



