HETEROMORPHOSIS 125 



solid body and became a root; however, when contact with 

 the wall of the aquarium was broken so that water sur- 

 rounded the root on all sides, a polyp was formed also at the 

 end of the root. In my further experiments I shall try to 

 find conditions under which the animal will form roots at 

 both poles with just as great certainty as it now forms heads. 

 From the experiments thus far discussed, I can only con- 

 clude that the formation of polyps in Tubularia mesembry- 

 anthemum can be brought about much more easily than the 

 formation of roots. 



III. THE LIFE-PHENOMENA OF THE ORAL POLE OF TUBU- 

 LARIA MESEMBRYANTHEMUM 



Doubt might arise as to whether the two heads of a bioral 

 Tubularian manifest the same life-phenomena ; as to whether 

 the two morphologically equal poles are also identical physio- 

 logically. I shall show that this is, indeed, the case, and in 

 doing so shall dwell a little more upon the differences in the 

 irritability of stem and root. 



1. The stem and root of Tubularia mesembryanthemum 

 have an entirely different contact-irritability. If the root is 

 brought in contact with a solid body, it attaches itself to it, 

 and in its further growth remains closely attached to the sur- 

 face of the solid. If an attempt is made to lift the stem 

 from the solid body, it tears off close to the root, the latter 

 remaining attached to the base upon which it grew. The 

 polyp has exactly the opposite irritability. When the polyp 

 comes in contact with a solid body for example, when the 

 stem lies horizontally upon the bottom of the aquarium it 

 soon grows away from it. The growing region of the stem 

 (which is situated close behind the polyp) becomes convex 

 against the solid substratum. 



This (stereo tropic) bending occurs only in the growing 

 part of the stem, and persists when growth has ceased, just 



