33° 



Florence Peebles 



formed double hydranths, one at the aboral end of the long piece, 

 and one on the short piece, the original direction of the small com- 

 ponent was always maintained (Fig. 7). In one graft where the 

 short piece developed a hydranth in the original direction (Fig. 

 8) it finally pushed the graft apart and emerged. 



{B) Loeb ('04) has described a series of experiments on Tubu- 

 laria in which he claims that the polarity was reversed. His experi- 

 ment was as follows: A long piece cut from the stem was Hga- 

 tured near the oral end. New hydranths developed at both ends. 

 After the hydranths had emerged from the perisarc he cut a piece 

 out of the region aboral to the ligature. Two days after the second 

 operation ten pieces had formed aboral hydranths and only five 

 had oral hydranths. From this result he concluded that the polar- 

 ity was reversed. In other words the aboral end having formed 

 a hydranth once, after the second operation, formed one again 

 because the hydranth-forming material had been carried to that 

 end. 



In my experiment the piece B (Figs, i and 2) corresponds in 

 position to the piece described by Loeb. Instead of waiting until 

 a hydranth had formed at each end, the piece from which it was 

 cut was united with another piece at its oral end and given a start 

 of twenty-four hours at its aboral end. Some changes must have 

 been going on at these two ends as some of the pieces did not 

 behave like corresponding pieces cut immediately from stems that 

 had not been grafted. The results are given in the following 

 table: 



TABLE 2 B 



Oral hydranths not followed by aboral 23 



Oral hydranths followed by aboral 15 



Oral and aboral hydranths simultaneously 7 



Lost 2 



Total number of pieces 47 



The majority of pieces behaved hke similar pieces in the con- 

 trol experiment, but in a few cases (seven out of forty-five) the 

 development of the aboral hydranth was hastened. Not one 

 piece developed a hydranth first on the aboral end. 



