Vol. V. November, ipoj. No. 6 



BIOLOGICAL BULLETIN. 



ABSORPTION OF THE HYDRANTH IN HYDROID 



POLYPS. 



H. F. THACHER. 



In 1900 there appeared a paper 1 by Professor Loeb on the 

 "Transformation and Regeneration of Organs," the first part of 

 which contained a discussion of the process of absorption in 

 campanularia hydroids. His results were obtained from a study 

 of the effects produced on the polyps by placing them in shallow 

 dishes of sea water, so that they were in contact with the glass ; 

 under these conditions he found that they were gradually trans- 

 formed and at length absorbed completely into the stem. To 

 summarize briefly Loeb's account of this process, he states that 

 there is noticeable first a contraction of the animal into the cup, 

 followed by the fusion of the tentacles and later by the with- 

 drawal of the whole polyp now a shapeless mass of proto- 

 plasm - - into the stem. This complete transformation he ascribes 

 to contact, since it "is certain that contact with sea- water favors 

 the formation of polyps with their more solid elements, while the 

 contact with solid bodies favors the formation of the more fluid 

 material of the stem or stolon." It seemed probable that a his- 

 tological examination of these changes, in which the hydroid is 

 represented as transforming and creeping back into the stein, might 

 prove of interest, since they involved a complete transformation 

 of well-differentiated structures. Therefore, at Professor Mor- 

 gan's suggestion, I worked on this subject at Woods Holl during 

 the summer of 1902. I was able to obtain a table first through 

 the kindness of the director, and later was appointed to the 

 Bryn Mawr table. 



On examining the literature it will be found that there are 

 frequent references to the absorption or disappearance of polyps. 

 Loeb finds for Margelis and Antcnnnlaria that the polyps 



1 The American Journal of Physiology-, IV., 1900. 



297 



