12 Ethel Nicholson Browne 
this purpose, I cut off a small ring of tissue from various regions 
of the body, including the region just beneath the circlet of tentacles 
and grafted it into the middle region of a hydra. These rings in 
no case gave rise to a new hydranth, but were soon absorbed. 
If, however, instead of a small ring of tissue, a large ring was 
grafted, the result was different. “The experiments were done in 
the following manner: A hydra was cut in two beneath the circlet 
of tentacles; the foot was then cut off from the lower part. The 
aboral end of this band of tissue was then grafted into the side 
of anormal hydra. On the following day, the graft had developed 
tentacles. In this case, however, it must be noted that the regener- 
ation is entirely on the part of the graft and not of the stock, and 
the stock takes no part in the formation of new tissue. 
The conclusions drawn from these experiments is that no other 
tissue than that at the base of the tentacles is capable of so stimu- 
lating the stock as to cause it to produce from its body wall a new 
hydranth. . 
Group G 
Regenerating Tissue as Graft 
This series of experiments was undertaken for the purpose of 
finding out whether tissue which has begun, in the process of regen- 
eration, to be differentiated into tentacle-forming material, would, 
when grafted, influence the body wall of the stock to regenerate a 
new hydranth. ‘The method adopted was as follows: A green 
hydra was cut in two at about the middle of the body. The pos- 
terior half was ther left till the following day when the wound had 
healed and the process of regenerating a new hydranth had started, 
although no tentacles had formed. A very small piece was cut off 
from the oral surface, and this was grafted into the side of a normal 
hydra. On the next day an outpushing of the body wall had 
occurred and a day later two tentacles had formed on the new 
hydranth (Figs. 40, 41). By leavingthe regenerating piece different 
lengths of time before grafting part of it into the stock, it was 
found that about ten hours was the minimum that would give 
regeneration. If left only seven hours before grafting, the graft 
