1923] Dedifp^erentiation in Hydroids and Ascidians 41 



jecting gonophore-string's. Each string consists of several, often 3-5, 

 gonophores, following on one another in a long single row. A number 

 of such gonosomes were amputated at the base from the rest of the 

 colony {July 30, 1910) and were kept in laboratory dishes. The 

 gonophores burst one after another, liberating sperm. This continued 

 during the next three days until most of the strings had been trans- 

 formed into short, hollow lobes, projecting like tentacles from the 

 aborted hydranth which was now considerably larger and better 

 marked off from the stem than it originally was. The mortality among 

 the amputated gonosomes was high and in the actual experiment only 

 a few reached the stage just described. These were preserved (Aug. 

 2). One especially gave clear evidence that the tentacle-like lobes 

 were being absorbed into the body of the hydranth. In the case of 

 some of the strings of gonophores all the gonophores had not burst at 

 the closing of the experiment ; such strings remained as hollow tentacle- 

 like lobes each with a single terminal gonophore. Doubtless the re- 

 duction of the gonosomes can be made to go farther than it was car- 

 ried in the actual experiment. 



A number of years ago some of Driesch's experiments (Archiv f. 

 Entw.-Mech. 1902, 1906) on reduction and restitution in simple ascidi- 

 ans were repeated at Beaufort, N. C, on Perophora viridis. Driesch 

 used ClaveUina, as did Schultz (Archiv f. Entw.-Mech. 1907) in his 

 later study. Huxley in his recent work (Quart. Journ. Micr. Sci. 

 1921) along the same line used Perophora. At Beaufort I was able 

 tt) make the following mainly confirmatory observations. 



Very small pieces of young fresh stolons, grown in the laboratory, 

 were pinched off with needles in such a way as to attach the pieces, 

 which were no longer than wide, to the cover. The attachment was 

 strengthened by draining the cover as it was passed to each new bowl 

 of fresh sea water. Of four pieces thus prepared (July 7, 1910), three 

 died but one transformed in three days into a little ascidian with 

 open retractile siphons ; the heart was beating vigorously on the 

 second day. The piece of stolon was so small that it was all used up 

 directly in forming the ascidian body, the process being one not of 

 budding but of morphallaxis. 



An effort was made to test the regenerative powers in vitro of 

 mesenchyme cells pressed out of the stolon. Clumps of cells sticking 



