2QO HELEN DEAN KING. 



There is a great similarity in the results of these experiments. 

 In all cases a hydranth formed on the oral end, A, of the an- 

 terior piece before one developed at any other cut surface, and 

 the rate of development of a polyp from the aboral surface, D, 

 was more rapid than that from the aboral surface, B, even in 

 those cases in which D had only two hours start over B. In no 

 case, however, did a polyp form at D before one developed at C, 

 even in the experiments in which D closed eight hours before C. 

 As was the case in the experiments made by Morgan, an interval 

 of eight hours between the two cuttings has, apparently, no more 

 effect on the regeneration than has an interval of only two hours. 

 The formation of a polyp at the oral end, C, of the proximal 

 piece, CD, does not prevent the early development of a polyp at 

 the aboral end of the same piece, and in some cases there is only 

 a few hours interval between the formation of the two hydranths. 

 The earlier development of a hydranth at A, however, seems to 

 check the formation of a hydranth at the aboral end, -B, of the 

 distal piece for some time, as in no case did a hydranth develop 

 at B until five days after the experiment began. This difference 

 in the rate of development at D and at B cannot be due to a 

 difference in the lengths of the pieces, because, in making the ex- 

 periments, the stems in all cases were cut as nearly as possible 

 through the middle and any difference in the lengths of the anterior 

 and of the proximal pieces would be too slight to have any ap- 

 preciable influence on the result. The earlier closing of the 

 aboral end, D, of the proximal piece, CD, evidently counter- 

 balances to some extent the influence of the oral end, as sug- 

 gested by Morgan. As a result, the development of a polyp at 

 D is hastened somewhat, although in no case is a hydranth 



formed here before or as soon as one develops at the oral end of 

 the piece. 



The effect of the earlier closing of the aboral end of long 



pieces of the stem, in both Titbularia mesembryanthemum and in 

 Tubularia crocca, is to hasten the development of the aboral sur- 

 face. The influences that bring about this result are apparently 

 not as strong in the latter species as in Tubularia mesembryan- 

 themum where the aboral development may be hastened so much 

 that polyps develop simultaneously at both ends of the piece. 



