Grafting of Tiibularia 



339 



large component of the graft is greatly reduced, while a relatively 

 large number form on the aboral ends of the smaller component. 

 The pieces J and C, upon which the aboral hydranths appeared 

 before the oral, were kept until the first hydranths were lost, and 

 new ones developed. Without exception, the second set of oral 

 hydranths appeared first, even in cases where the aboral hydranths 

 had developed one to tw^o days earher than the oral ones. This 

 shows without doubt that the polarity is not permanently reversed. 

 Experiment J. In this experiment the second operation fol- 

 lowed the first after six hours The results show that the aboral 

 ends had not had a suflficient start to produce hydranths before 



TABLE II 



12 12 1 111 



8122 2211J1 Sllii 



II 1 



1 1 1 I2 1 l2 



2 2 2 2 



1 1 



2 2 2 2 1111 1 

 2 2 2 112 



the oral ends. None of the grafts formed hydranths on their oral 

 ends, instead, the majority developed a hydranth first at the aboral 

 end of the short piece, and several hours later at the aboral end of 

 the longer piece. 



TWO LONG PIECES 



GRAFTED TOGETHER BY THEIR ABORAL 

 ENDS 



It has been demonstrated by many observers that a piece cut 

 from the stem of Tubularia, if sufficiently long, shows marked 

 polarity, i. e., a hydranth develops first on the oral end of the stem 

 and then later on the aboral end. I have shown that when two 



