288 



HELEN DEAN KING. 



Tnbularia crocea, the hydranths already present at the anterior 

 ends of the stems were removed .by a transverse cut about 2 mm. 

 behind the proximal circle of tentacles, and then pieces of .stem 

 varying in length from 3040 mm. were cut off and the ends 

 allowed to close. After an interval of from two to eight hours 

 the stems were cut through the middle as in Fig. I, B, C, thus 

 producing a freshly cut surface (Fig. I, >) at the aboral end of 

 a distal piece, and also one at the oral end (Fig. I, C) of a 

 proximal piece. The results of this series of experiments are 

 given in Table I. to IV. The first column gives the total number 

 of individual stems operated upon ; the second column shows the 

 time that elapsed between the removal of the hydranth and the 

 cutting of the stem through the middle ; and in the following 

 columns the results two, three, and four days after the operation 

 are indicated. Hy. signifies the regeneration of a complete hy- 

 dranth ; t. a. indicates the formation of tentacle anlagen only ; 

 while is used to indicate that no regeneration had taken place 

 when the observations were made. The letters A, B, C and D 

 refer to surfaces thus marked in Fig. I ; and the numbers in 

 parentheses show the number of cases in which similar results 



were obtained. 



TABLE I. 



Owing, probably, to differences in the temperature of the 

 water in which they live, regeneration in Tubularia crocea is much 

 slower than in Tubnlaria uicscnibryantlieuiuui. In the former 

 species a new hydranth rarely develops until two days after the 

 removal of the old hydranth, while in the latter species a new 

 hydranth frequently regenerates in the course of twenty-four 

 hours. In all of the experiments in this series, as shown in the 

 above table, a polyp formed on the oral end, A, of the anterior 



