HETEROMORPHOSIS 145 



When the roots were brought in touch with the surface 

 of the water, the latter acted upon the root as a solid body. 

 The root began to grow rapidly in length, attaching itself to 

 the surface of the water (as if it were the surface of a solid 

 body). Whenever a root adhered to a solid body new stems 

 arose from that surface of the root which lay diametrically 

 opposite to the solid body. Usually these branches then grew 



FIG. 24 



perpendicularly away from the surface of the solid body. 

 When new stems arose from roots growing along the surface 

 of the water, the stems grew vertically downward. 



X. ON THE FORMATION OF TENTACLES IN CERIANTHUS 

 MEMBRANACEUS 



1. I shall now discuss some experiments upon animals 

 which seem to behave in accordance with Allman's theory of 

 polarity, inasmuch as in these I did not succeed in producing 

 a head in the place of an aboral pole. The experiments 

 led however to the production of several heads lying one 

 above the other in one and the same animal (see Figs. 24, 

 25). The irritability of the new heads could easily be com- 

 pared with that of the old. In these experiments, more- 



