20 Ethel Nicholson Browne 
asserts itself in the new material which now becomes a part of its 
own body. If this secondary polarity be conceived as prepon- 
derating over the primary polarity of the graft, this original polar- 
ity would be entirely submerged, and this is probably the case in 
the former experiments where only heteromorphic tentacles were 
formed. On the other hand if the primary polarity preponderates 
over the secondary we should have tentacles at the junction of 
graft and stock and no heteromorphic structure. Many cases of 
this result have been reported by Peebles and King. 
In three cases I succeeded in obtaining heteromorphic feet by 
grafting the two cut aboral ends of a white and a green hydra 
and then cutting off the head of the green end leaving an exposed 
oral surface of green tissue (Fig. 65). ‘This graft resulted in the 
formation of a normal hydra consisting of a head end of white 
material and a foot end of green material (Fig. 66). The foot 
end consisted of a true foot as evidenced by the presence of the 
characteristic sticky secretion which made the foot adhere to the 
substratum. These were evidently cases of heteromorphosis, 
the polarity of the stock so influencing the graft as to preponderate 
over its original polarity, thus calling forth a foot from its exposed 
oral surface. ‘The production of heteromorphic feet in these experi- 
ments confirms the like experiment of Wetzel and is opposed to 
the results of Peebles who obtained no heteromorphic foot in the 
fifteen cases tried. No hook-like processes such as described by 
Wetzel as preceding the formation of a heteromorphic foot appeared 
in my experiments. 
CONCLUSIONS 
As a result of the experiments recorded in this paper, the follow- 
ing conclusions may be drawn: 
1. The fate of a graft in Hydra viridis depends on several 
factors. Rand states that “the fate of the graft depends upon its 
degree of specialization.” King states that “the fate of a graft 
depends, not upon its degree of specialization, but primarily on 
Its size and to some extent on its position in the stock.” From 
my experiments, I should conclude that the fate of a graft depends 
(1) primarily on its specialization. If the tissue grafted is a smal 
