ORGANIZATION AND GROWTH 215 



only apparent. It may be that I had to do with a bifur- 

 cation of a root which had been produced through contact 

 stimuli, of which the one branch continued to grow without 

 contact. But, as before, I did not succeed in causing the 

 growth of a root at the oral pole in even a single instance; 

 it may be that this is impossible in Tubularia by any of the 

 means which I have employed thus far. In the light of my 

 previous experiments on Antennularia and Aglaophenia, I 

 need not emphasize that this is only a special characteristic 

 of Tubularians. 



If a root is formed at one extremity of a Tubularian, 

 and this has grown vigorously for some time, its tip not 

 infrequently becomes faintly red, and this coloration deepens 

 rapidly ; in such cases a polyp forms at the tip of the root, 

 which then immediately bends away from the substratum 

 upon which the root has grown and grows almost perpendic- 

 ularly upward, We then have a colony of two polyps which 

 are attached to the base upon which they grow by a common 

 root. The difference between such an animal and the 

 heteromorphic bioral animal lies in the fact that the latter 

 lacks an inherited organ, the root. In its place a polyp has 

 been formed. 



VI. EXPERIMENTS ON ORGANIZATION IN CIONA INTESTINALIS 



1. The animals in which I have thus far been able to 

 produce heteromorphoses stand low in the animal scale ; we 

 have dealt only with Hydrozoa. It might bethought that 

 these "colony-forming" animals are an exception to the gen- 

 eral rule, and that only in them a movement of formative 

 substances can take place in both directions in the sense of 

 Sachs's theory. Such a view is supported by the fact that 

 "polarity" is very pronounced in a series of Actinia?, and 

 that, in spite of my efforts, I have not succeeded in bringing 

 about heteromorphoses in them. The fact that a solitary 



