REGENERATION IN TUBULARIA CROCEA. 297 



with equal rapidity from the cut oral surface of the branch and of 

 the stem, as was the case in the experiments described under 

 series 3. If the pieces above the place of union of the branch 

 and stem are of approximately the same length, no matter how 

 long or how short they may be, the influences for hydranth for- 

 mation appear to be alike in both, and one piece has, seemingly, 

 no effect on the other. Where the ccenosarc is withdrawn entirely 

 from one part of the hydroid, as was noted in some few cases in 

 the last set of experiments, no regeneration of the piece is 

 possible. 



In experimenting on Tubnlaria crocea, Morgan (9) found that 

 if he cut off both the main stem and the branch a little above the 

 place of union, the results varied considerably in different cases. 

 In some instances he obtained the regeneration of a hydranth 

 on the branch and not on the oral end of the stem ; in other 

 cases a polyp formed only at the oral end of the main stem ; 

 and in still other individuals regeneration took place from the cut 

 surfaces of both branch and stem. It seems probable that the 

 lack of uniformity in these results can be attributed to a difference 

 in the relative lengths of the branch and of anterior portion of 

 the stem above the point of insertion of the branch. It is, of 

 course, impossible to cut the branch and stem at absolutely 

 equal distances from the place of their union, and in those cases 

 in which regeneration from one cut surface took 

 place before it did from the other, there may have 

 been just enough difference in the lengths of the 

 pieces to bring about the earlier regeneration of a 

 hydranth on the cut oral surface of the longer 

 piece. 



Scries >'. In twenty-eight cases the stem was 

 cut off transversely just above the origin of the 

 branch as shown in Fig. 7. The oral end of the 

 branch was then removed leaving a piece, from 3 

 to 5 mm. in length, still attached to the stem. The object 

 of these experiments was to see whether the regeneration of a 

 hydranth at the oral end of the stem could be entirely pre- 

 vented by this means. Two days after the operation, hydranths 

 had developed at the cut end of the branch in nine of the hy- 



