NOTES ON REGENERATION IN TUBULARIA 



CROCEA. 



HELEN DEAN KING. 



The following experiments on Tnbitlaria (Parypha)crocca were 

 made during the summer of 1903, at Woods Holl, Mass., while I 

 was occupying a research room of the Carnegie Institution in the 

 Marine Biological Laboratory. The work was done under the 

 direction of Prof. T. H. Morgan to whom I am indebted for 

 many helpful suggestions. 



I. THE EFFECT OF THE EARLIER CLOSING OF ONE END OF A 

 LONG PIECE OF THE STEM OF TUBULARIA. 



In experimenting on the European hydroid Tnbnlaria mes- 

 embryanthemum, Morgan (10) allowed the ends of long pieces of 

 the stem to close and then, after an interval of from one to eight 

 hours, he cut the pieces transversely through the middle region so 

 that two new cut surfaces were exposed (Fig. i, B, 

 C). As a result, the aboral development of the proxi- 

 mal piece CD, was hastened. In many cases a polyp 

 appeared on the aboral surface, D, as soon as did a 

 polyp on the oral end, C, and in a few pieces a 

 hydranth developed at D as early as did the hydranth 

 on the distal end of the anterior piece, AB. This re- 

 sult is explained by Morgan as follows: "When a 

 piece is cut in two in the middle one, two, three or 

 more hours after its ends have closed, the influence 

 of the oral end is temporarily removed, and the aboral 

 end, which now has a start on the new oral end. 

 may gain the ascendency and be the first to pro- 

 duce a polyp. Often, however, the polarity of the 

 piece is sufficiently strong to give the precedence to 

 the influences acting on the oral end. When the 

 two influences are equally balanced, two hydranths may simul- 

 taneously develop." 



In repeating these experiments on the American hydroid, 



287 



FIG. i. 



