CRAFTING AND REGENERATION l6/ 



Tubularia is not so well suited as hydra to show the influence 

 of grafting on the united parts, since pieces of tubularia produce 

 hydranths, both at the oral and aboral ends, although the latter 

 hydranths take longer to develop. Peebles has shown, nevertheless, 

 that grafting has an influence on the behavior of a piece. In order 

 to show that the polarity of a small piece could be affected by a 

 larger piece, the following experiment was carried out. After cutting 

 off the old hydranth from the end of a stem, a short piece was then 

 cut from the distal end of the same stem, turned around, and its oral 

 end brought in contact with the oral end of the original piece, as 

 indicated in Fig. 49, F. The two pieces, being held together for a 

 few minutes, stuck together and subsequently united perfectly. 

 From eighty-eight pieces united in this way the following results were 

 obtained. Thirty-six formed a single hydranth at the end at which 

 the grafting had been made. The distal row of tentacles appeared 

 in the smaller reversed component, the proximal row in the larger 

 piece (Fig. 49, B}. The new hydranth pushed out later through the 

 perisarc of the smaller piece (Fig. 49, C). In this experiment the 

 smaller component was shorter than the average length of the hy- 

 dranth-forming region. In two cases, in which the smaller component 

 was larger, both circles of tentacles appeared in this piece. In six of 

 the experiments the tips of the proximal tentacles arose from a part 

 of the wall of the smaller piece, hence these tentacles had a double 

 origin (Fig. 49, F). In five of the unions the smaller as well as the 

 larger component produced a hydranth ; the two were stuck together 

 by their oral ends (Fig. 49, D, E}. The remaining four unions gave 

 somewhat different results. In three of these the smaller piece pro- 

 duced only a part of a hydranth that remained sticking to the end of 

 the hydranth formed by the larger component. In the thirty-six 

 cases in which the minor component took part in the formation of 

 the single hydranth, the influence of the larger component was shown 

 not only in reversing the polarity of the smaller component, although 

 this might in part be accounted for by the closing of the oral end of 

 the smaller piece, but also in the time of development, since the 

 hydranth appeared sooner than does the aboral hydranth and at the 

 same time as does the oral hydranth. 



In another series of experiments, a short piece was cut from the 

 basal end of a long piece (three to four centimetres) and brought 

 forward and grafted in a reversed position on the anterior end of 

 the same long piece (Fig. 49, A). Of five unions of this sort, one 

 produced a hydranth in each component, neither being reversed. 

 Another of the pieces produced a hydranth partly out of each com- 

 ponent (and at the same time another at the aboral end of the large 

 piece). The other two pieces produced a single hydranth, a part of 



