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.’ 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.’ 
Driesch confirmed her observation.’ 
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 Campanulariz 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 mest 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 LoEeB, Woods Hole Biological Lectures, 1893. 
2 BICKFORD, Journal of Morphology, Vol. IX (1894), p. 417. 
3 Driescu, Vierteljahrschrift der Naturforscher-Gesellschaft, Ziirich, 1896. 
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