REGENERATION IN TUBULARIA CROCEA. 



295 



FIG. 4. 



branching stems a short piece of a branch or of a stem regener- 

 ates as does an isolated short piece, /. e., the region of the ten- 

 tacle anlagen is reduced and the rate of development of a 

 hydranth is much slower than that of a hydranth from the cut 

 end of a long piece of stem. Both of these factors may help to 

 bring about the delay in the development 

 of a hydranth from the oral end of the 

 shorter piece in all of these experiments 

 with branching stems in which there is a 

 marked difference in the length of the stem 

 and of the branch. 



Series 2.-- Seventeen branching stems 

 from different colonies were cut so that the 

 anterior portion of the stem above the place 

 of union with the branch was only about i 

 mm. in length, while the length of the 

 branch varied in different cases from 825 

 mm. (Fig. 4). Two days after the opera- 

 tion, hydranths had developed at the cut 



ends of thirteen branches, and well developed tentacle anlagen 

 were found at the oral ends of the other four branches. No 

 hydranths were found at this time at the oral end of any of the 



stems, and tentacle anlagen were only 

 faintly defined in some few cases. On 

 the next day, hydranths had developed 

 at the distal end of all of the branches, 

 but only five stems bore hydranths at 

 the oral end. In this set of experiments 

 the development of a hydranth took place 

 more rapidly from the cut end of the 

 lone branch than from the oral end of 



o 



the main stem. 



Series j. - - Twelve experiments were 

 made in which the anterior end of the 

 stem and the distal end of the branch 

 were cut off so that the length of the 

 branch and of the stem above the place 

 of union was practically the same, varying in different cases 



FIG. 5. 



