EXPERIMENTS ON POLARITY IN TUBULARIA. 



BY 



T. H. MORGAN AND N. M. STEVENS. 

 With 5 Figures and 20 Tables. 



In the discussion that has arisen in regard to the factors that 

 determine the formation of new hydranths in Tubularia, the red 

 pigment in the stem and in the current has played a conspicuous 

 role. Loeb first suggested the idea in 1891 without, however, 

 stating clearly whether he referred to the pigment in the wall or in 

 the current, although the former appears to have been intended, 

 as he makes no mention of a current or of pigment in the current. 

 In his last publication, however, he argues in favor of the 

 pigment in the current being an important factor in the regenera- 

 tion of hydranths. Driesch also thought that the pigment in 

 the circulation might have at least a quantitative relation to 

 hydranth formation. Morgan has presented evidence which, 

 he believes, disproves that the red pigment, as such, takes any 

 part in the formation of the hydranth, pointing out, among other 

 objections to the views of Loeb and of Driesch, that the pigment of 

 the current is not absorbed, but is gathered together in the diges- 

 tive cavity within the new hydranth; and Stevens has observed 

 that this ball of pigment is later vomited forth from the 

 mouth of the fully formed hydranth. We had hoped that our 

 observations had laid to rest the question of the supposed role of 

 the pigment in regeneration, but such appears not to be the case, 

 since in his recent publication Loeb returns once more to 

 the problem. For this reason it has seemed to us worth while to 

 undertake a new series of experiments, although we think the 

 evidence already advanced more than sufficient to disprove the 

 view that the pigment has any direct influence on the regeneration 

 of hydranths. While we have considered this question somewhat 



