16 Ethel Nicholson Browne 
We conclude then, that when a piece of tissue is grafted into a 
normal hydra and does not cause regeneration, the grafted tissue 
is incorporated into the body wall of the stock. The cells that 
have formed tentacle or body wall tissue are made over in the stock 
into body wall cells. The tissue is absorbed, not in the sense that 
it disappears, but in the sense that it becomes one with the tissue 
of the stock. 
Group C 
Grafts of White and Green H ydranths 
A few experiments were performed with green and white hydras 
to discover if possible whether a hydranth that was grafted in the 
side of another hydra kept its individuality or whether the tissues 
of the two hydras fused. In one of the two successful grafts in 
which a short green head was grafted into a white hydra at about 
the middle region, the graft retained its individuality and was of 
approximately the same size and in about the same position at the 
end of two weeks as at the time of graft (Fig. 52). As the hydra 
did not live until the graft pinched off, the final result was un- 
decided, but it seemed probable that it would pinch off at the 
line of union of graft and stock. The second graft was more 
interesting for the reason that the green grafted head increased in 
size until of equal length with the head of the stock and then mi- 
grated down toward the foot end of the white hydra (Fig. 46). 
The point to be noted is that in increase in size, the new material 
came not from the larger white hydra but was formed by the green 
hydranth. The graft not only kept its individuality but also 
completed itself by regenerating new material. A third experi- 
ment of somewhat different kind shows the same principle. A 
white and green head were grafted together by their aboral ends, 
the green one being somewhat shorter than the white one (Fig. 
53). Both hydranths kept their individuality and the green one 
regenerated new tissue so as to become of equal length with the 
white one (Fig. 54). In this condition, the graft died, evidently 
just before separation would have taken place. 
From these experiments we conclude that the grafted hydranth, 
although intimately associated with the stock, keeps its individual- 
