210 STUDIES IN GENERAL PHYSIOLOGY 



had regeneration begun in all of these specimens. In 

 other experiments, also, the same results were obtained. 

 That the orientation of the Tubularian stem toward the 

 center of gravity has no effect I have mentioned in the 

 preceding paper iv; and I have corroborated this finding 

 by careful control experiments. I suggested in paper iv 

 that regeneration perhaps occurs more rapidly at the oral 

 pole because a distinct difference in the diameter of the 

 lumen usually exists between the two extremities. The 

 experiments cited above show that this suggestion is incorrect ; 

 there is no difference in diameter at a transverse section, 

 and yet regeneration always occurs much earlier at the one 

 cut end than at the other. 



5. If the Tubularian stems used in the experiment are 

 very turgescent, and highly pigmented, the difference in 

 time between the formation of the oral and the aboral polyps 

 may be very slight, and amount to only a few days. Very 

 often one finds pale Tubularise which form polyps within the 

 usual time at the oral pole, in which, however, the polyps at 

 the aboral pole are formed only after one or more weeks. 

 I made the following experiment upon such animals : I fixed 

 eight animals (I) taken from one colony vertically, in the 

 sand, but with their oral ends downward, in order to prevent 

 the formation of polyps at these ends. At the same time I 

 suspended seven other animals (II) of the same colony also 

 vertically and in an inverted position in the aquarium, but 

 so that both ends were surrounded by water. These animals 

 had to form polyps at both cut ends. All animals were kept 

 in the same aquarium, and were therefore exposed to the 

 same temperature. After three days the first few new polyps 

 were formed at the oral pole of those Tubularians (II) of 

 which both ends were surrounded by water. On the next 

 day all of these had formed polyps at the oral cut end. The 

 same day, however, polyps were formed in five of the animals 



