Experiments on Polarity in Tubularia. 



569 



In order to determine whether, if a neutral zone exists in double- 

 headed pieces, it lies nearer the oral or the aboral end, several 

 pieces were cut nearer the old oral end, and others nearer the old 

 aboral end. The results are shown in Tables II and III. 



In Table III the number of pieces which produced hydranths 

 at c is proportionately much greater than in Table II. The 



III S. I I 1 I I 1121, 



s 5 s ' 2 3 I Z I s. s 



Table I. 



fl / / 



/ I I I I I 



z a, a, 1-2, 



d 3. J / / 



Table II. 



.//lis J 



Table III. 



results so far obtained might be construed to mean that the 

 influence of the aboral polyp extends only a short distance and 

 that its influence extends much farther in some cases than in 

 others. Under this supposition we must account for the hydranths 

 at b in Table III as in other double-headed pieces. 



Experiment 3. In this experiment the oral end of the pieces 

 was stuck into sand and kept there until the aboral head devel- 

 oped at the free end. The pieces were stuck into sand July I. 

 After 48 hours a few pieces had regenerated aboral heads, and 

 after 72 hours nearly all had new heads. The pieces were then 

 taken from the sand and the new polyp (old aboral end) and the 

 old distal end cut off". The result ought to show whether any 



