Grafting of Tubularia 



341 



that the long piece might exert some influence on the short one. 

 The results from one series of twenty-seven grafts is shown in 

 Table 13. 



Nine of the long pieces formed hydranths on the oral ends first, 

 while this took place only twice in the short pieces. Nine of the 

 long pieces formed hydranths while no new hydranths appeared 

 on the short ones. 



Experiment J. In order to determine if the distance from the 

 original hydranth had any influence on the rate of development, 

 a set of experiments was made where the pieces were grafted so 

 that when cut the oral end of one component should be much 

 nearer the original hydranth than the oral end of the other (Fig. 

 15). The results showed no diff^erence in the time of develop- 

 ment of the oral hydranths on the two components. 



Experiment ^. In the fourth experiment the pieces forming the 

 graft were cut off^ at equal lengths, very close to the line of union 

 (Fig. 16), each piece measuring 2 to 4 mm. With scarcely any 

 exceptions (about three out of forty), the hydranths formed first 

 on the oral end of the inner piece ( Fig. 16, X) and if one formed 

 at all on the outer piece {T) it appeared at least one day later. 



The results of these four series of experiments seem to me to be 

 of pecuhar interest, and they are not without weight in consider- 

 ing the problem of polarity. Why should a compound (grafted) 

 individual with two oral ends exposed at the same time, in a large 

 majority of cases develop a hydranth first on one oral end, and 

 and then on the other ? Shall we say that there is such a thing as 

 polarity in this new double individual, or shall we say that all the 

 "hydranth-forming material" has been carried to one end so 

 that development at the other was delayed .^ It is evident from 

 experiments that I shall describe later, that the direction of the 



