122 



STUDIES IN GENERAL PHYSIOLOGY 



Contrary fo the theory of the "polarity" of the animal 

 body, therefore, fragments of Tubularia mesembryanthemum 

 are able to form polyps even at their aboral ends. 



2. I supported pieces cut from the stem of Tubularia 

 mesembryanthemum in such a way that both cut ends were 



surrounded by water. To do this I sup- 

 ported them in the meshes of a long wire 

 net, or in the holes of a metal plate set up 

 in the aquarium for this purpose. Polyps 

 were formed at both the oral and the aboral 

 ends of the fragments, so that the stem 

 terminated in a head at each end. Fig. 

 16 represents such an animal sketched from 

 life and enlarged twice. ab is the piece 

 removed from the old Tubularian. Polyps 

 were formed at both ends, and the stem 

 then grew in length from both ends, ac 

 and bd are the new pieces that grew after 

 the formation of the polyps. 



I have in this way been able to produce 

 at any time any number of animals which 

 terminate in an oral pole at each of the two 

 ends of their body. I shall hereafter 

 designate animals which terminate in a head 

 at each end bioral animals. 

 I would particularly emphasize the fact that such an 

 animal remains bioral for the rest of its life. It is a 

 well-known fact that in a normal animal the oral polyp is 

 lost spontaneously after some time, and that a new one is 

 formed sooner or later in its place. In the case of the bioral 

 animals a constant blooming, shedding, and reappearance of 

 the polyps occurs, not only at the oral end, but also at the 

 aboral end, during the entire duration of their life. 



3. I was able, therefore, not only to cause the develop- 



FIG. 16 



