Production of New Hydranths in Hydra 9 
shorter regenerated ones (Fig. 30). By April 1, these four ten- 
tacles were of the same length, and by April 5, a fifthtentaclehad 
appeared, so that the hydra was a typical double-headed animal 
(Fig. 31). In the other similar graft, after the outgrowth of two 
small hydranths at the base of each grafted tentacle, they migrated 
from opposite sides so as to be adjacent (Fig. 32). A process of 
fusion then set in, so that ten days after grafting, the two regener- 
ated hydranths, each with three tentacles, were separate only at 
their distal ends (Fig. 33). ‘This fusion was complete two days 
later, resulting in the formation of a double-headed hydra. 
Result 2. In two other cases of similar grafts, only one of the 
grafted tentacles gave rise to a new hydranth, the other one being 
gradually absorbed (Fig. 34). 
Result 3. In the other two cases, both tentacles were absorbed 
without any regeneration. 
From this group of experiments it is evident that each of two 
tentacles with peristome tissue at their base, when grafted intothe 
middle region of a hydra, may cause the regeneration of a new 
hydranth. However, a process of fusion or absorption sets in 
sooner or later, so that only one of the regenerated hydranths 
remains. 
Group ‘& 
Tentacle Without Peristome at Base as Graft 
Having obtained so definite a response on the part of the stock 
to a grafted tentacle, I next tried to find out what part of the grafted 
tentacle was responsible for the regeneration. In this group of 
experiments I grafted just the tentacle without any peristome 
tissue at its base into the stock. This operation was somewhat 
difficult as the raw surface of the tentacle healed over rapidly and 
would not then adhere to the cut surface of the stock. About 
eight times, however, by performing the operation very quickly, 
I was successful. All the experiments gave the same result, 
whether the graft was made in the middle or foot region of the 
stock. There was no outpushing of the body wall of the stock, no 
regeneration whatever, but, on the contrary, the grafted tentacle 
