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HELEN DEAN KING. 



face, B, the rest had, as yet, developed only tentacle anlagen ; 

 in the control stems, no development from the aboral surface, B, 

 had taken place in any case. 



It is seen from the above experiments, that the development 

 of a hydranth at the oral end of a piece of the stem of Tubit- 

 laria crocca is not hastened by artificially closing the aboral end. 

 Tying the oral end of a distal piece of the stem, however, hastens 

 the development of the aboral end of the piece as compared with 

 the development that takes place from the aboral surface of a 

 piece of stem of similar length that is not closed at the oral end, 

 as Driesch has shown. This result also agrees with that obtained 

 by Loeb (7) in experiments in which he stuck the oral end of 

 pieces of the stem of Tulntlaria mesembryanthemum in fine sand, 

 leaving the other end freely surrounded by water. He found 

 that " Durch Hemmung der Polypenbildung am oralen Ende 

 kann man also die Polypenbildung am aboralen Ende besch- 

 leunigen." 



In a third set of ten experiments, hydranth bearing stems 

 about 30 mm. in length were removed from the colony and kept 

 until a polyp formed on the cut aboral end. The time required 

 for the development of these aboral polyps varied from three to 

 five days in different cases. After all of the pieces had developed 

 hydranths at the aboral end, each stem was cut transversely 

 through the middle as in Fig. 2, B, C. The object of these 

 experiments was to ascertain whether the presence of a hydranth 

 at the aboral end, D, of the proximal piece, CD, would alter the 

 polarity of the piece and thus prevent or retard the development 

 of a hydranth at the oral end, C. The stems were cut through 

 the middle region on June 19. Not until June 22 were there 

 any indications of a development of a hydranth at the oral sur- 

 face, C, and then only faint traces of tentacle anlagen were found 

 in three stems. At this time, no development had taken place 

 from the aboral surface, B, of any of the anterior pieces, AB. 

 For control experiments, pieces of stem about 30 mm. in length 

 were cut through the middle as in Fig. I, BC, at the same time 

 that the transverse cuts were made across the stems bearing a 

 hydranth at each end, and on June 22, well developed hydranths 

 were present at the oral end of all of the proximal pieces. On 



