168 Regeneration 



but the velocity with which the two polyps are 

 formed is not the same, the polyp at the oral end 

 of the piece being formed much more rapidly — a day 

 or one or two weeks sooner — than the aboral polyp. 

 The process of polyp regeneration at the aboral pole 

 could, however, be accelerated and its velocity made 

 equal to that of the regeneration of the oral polyp by 

 suppressing the formation of the latter. This was 

 accomplished by depriving the oral pole of the oxygen 

 necessary for regeneration, e. g., by merely putting the 

 oral end of the piece of stem into the sand. It was, 

 therefore, obvious that the formation of the oral polyp 

 retarded the formation of the aboral polyp. This 

 inhibition might have been due to the fact that a 

 specific organ-forming material needed for the forma- 

 tion of a polyp existed in sufficient quantity in the stem 

 for the formation of one polyp only at a time. This 

 idea, however, was found to be incorrect since when the 

 stem was cut into two or more pieces each piece formed 

 a polyp at once at its oral pole and regenerated the 

 aboral polyps also, but again with the usual delay. It 

 seemed more probable then that the cause of the 

 difference in the rapidity of polyp formation at both 

 ends lay in the fact that certain material flowed first 

 to the oral pole and induced polyp formation here but 

 that this flow was reversed as soon as the polyp at the 

 oral pole was formed or as soon as the formation of the 

 oral polyp was inhibited by lack of oxygen. The partial 



