568 



T. H. Morgan and N. M. Stevens. 



A 



sort of neutral zone without any polarity or with a weak polar 

 condition, if such a thing is possible. The results show that 

 the original polar condition still manifests itself in this region, 

 as seen in the following figures for five pieces (Fig. 2). 



The aboral head at b in piece 5 can be accounted for without 

 assuming it to be due to a change of polarity, for aboral heads, as 

 we have seen, sometimes develop on short pieces. The absence 



of a polyp at d on the other half 

 indicates that the change caused 

 \f by the aboral polyp is not great. 

 Later a polyp appeared on piece 

 I a.t b and at d. 



In the next series (Fig. 3), with 

 three pieces, the influence of the 

 aboral polyp is better seen, but 

 the old polarity still shows itself 

 in the oral heads. These pieces 

 were cut June 30. Record A 

 was taken July 2; record B, 



July 3- 

 In another series four pieces developed as shown in Fig. 4. 



In the first and third pieces the old and the new polarity are 



exhibited in the aboral half. 



The following table gives the results for 19 

 pieces cut as above at different dates, from June 

 27 to July 24. The figures indicate the order in 

 which the hydranths appeared. The letter s 

 indicates a stolon. 



The appearance of hydranths simultaneously 

 at b and c and of stolons at c in several cases may 

 indicate a more or less unstable condition of 

 polarity near the middle of the piece; but as a 

 whole, the table shows a stronger tendency to produce hydranths at 

 c (oral) than at b (aboral), /. e., the original polarity in most cases 

 overbalances whatever change may have been effected by the 

 development of a hydranth at the aboral end of the original 

 piece. 



Fig. 3. 



Fig. 4. 



