TRANSFORMING AND REGENERATING ORGANS 629 



reaction of a root. It looks as if the contact with a solid 

 body brought about a transformation of the stem into root 

 material which is morphologically and physiologically dif- 

 ferent from the stem. 1 But as neither Antennularia nor 

 Margelis is sufficiently transparent, it was not possible to 

 ascertain that a transformation of polyps and stems into 

 stolons occurs in this case. 



Miss Bickford made an observation in my laboratory 

 which helped in making the assumption of a transformation 

 of organs more probable. Small pieces were cut from a 

 stem of a Tubularian. These pieces were smaller in size 

 than a normal polyp. Miss Bickford found that within 

 sixteen hours such a piece assumed the form of a polyp. 2 

 Driesch confirmed her observation. 3 



Last summer I had an opportunity to observe directly 

 the transformation of organs under the influence of contact. 

 My observations were made at Woods Hole on a transparent 

 Hydroid, Campanularia. This Hydroid attaches itself with 

 stolons to solid bodies. The stem with the polyps grows at 

 right angles with the solid body to which its stolons are 

 attached. If these Campanularia be cultivated on a ver- 

 tical wall all the stems assume an exactly horizontal position 

 in the water. The stem of a Campanularia is the most per- 

 fect specimen for negative stereotropism I have ever ob- 

 served. If a stem be cut off and put on the bottom of a 

 watchglass filled with sea-water, all the polyps that touch 

 the glass are transformed into the material of the stem. 

 This material creeps out of the stem, forming stolons wher- 

 ever it comes in contact with the glass, giving rise to polyps 

 on its upper surface which is in contact with sea-water. 

 The polyps continue growing at right angles toward the 



1 LOEB, Woods Hole Biological Lectures, 1893. 



2 BICKFOED, Journal of Morphology, Vol. IX (1894), p. 417. 



3 DEIESCH, Vierteljahrschrift der Naturforscher-Gesellschaft, Zurich, 1896. 



