!OO 



HELEN DEAN KING. 



and of Tnbularia crocea. He finds, as did Driesch, that pieces 

 about I mm. in length from the region immediately behind the 

 old hydranth usually die, even when longer than pieces from a 

 more proximal region that regenerate. When this distal region 

 does regenerate, it produces a greater number of single proboscides 

 than of other forms, a result that might be expected as this part 

 of the stem ordinarily goes into the proboscis of the new hydranth 

 when a long piece of stem is regenerating. 



In another set of experiments, Morgan cut pieces of the stem 

 of Tubnlaria mesembryanthemum into a series of small pieces 

 about i mm. in length in order to observe the behavior of con- 

 secutive pieces from one stem and to compare the results with 

 those obtained from similar pieces cut from other stems. His 

 tables do not show any very definite results although there seems 

 to be a certain similarity in the behavior of pieces of the same 

 stem, and the incomplete structures are found most frequently 

 at the distal end of the stem. 



At the suggestion of Professor Morgan, I repeated his experi- 

 ments, using Tnbularia ci-occa, in order to furnish more data from 

 which definite conclusions could be drawn. In making the ex- 

 periments the old hydranths were removed and the distal part of 

 the stem was cut into consecutive pieces about I mm. in length. 

 The pieces were than laid in rows on the bottom of flat dishes 

 filled with fresh sea water. For the sake of brevity the follow- 

 ing abbreviations are used in the tables given : hy. = complete 

 hydranth without any stalk ; hy. + stalk = hydranth with a 

 short stalk that has been formed by a withdrawal of the coeno- 

 sarc from the perisarc ; hy. -f stem = hydranth with a stem 

 attached to the perisarc ; pb. = single proboscis ; d. pb = double 

 proboscis ; reprod. = reproductive organs. The results tabulated 

 are from observations made three to four days after the operation. 







TABLE V. 



