148 STUDIES IN GENERAL PHYSIOLOGY 
spring from the lower cut surface; the upper cut surface f 
is free from tentacles. The cut surface ac (Fig. 27) suffers 
changes which lead to a rounding off of this part, and make 
it resemble a foot. JI have made more than a hundred such 
experiments, and yet have always obtained the same result. 
In order to have new tentacles form it is necessary to pre- 
vent the lips of the wound from healing together during the 
first few days after the operation. I attained this end most 
easily by laying the operated animals upon a wire screen; 
the animals would push their aboral ends through the 
meshes of the screen up to the incision. The wire then 
pushed itself between the lips of the wound, and so prevented 
the edges from healing together. First the outer row of 
tentacles and an oral plate were formed; then an inner row 
of tentacles originated; so that finally such an animal pos- 
sessed two morphologically identical heads the one situated 
above the other. Such animals are represented in Figs. 24 
and 25; a is the old, b the new head. The new head in 
Fig. 24 is about three months old; that in Fig. 25 is much 
younger. By similar means I also succeeded in producing 
animals with three heads, situated one above the other. 
There was nothing to prevent the production of a still larger 
number of heads lying one above the other, if there had 
been any object in doing this. I noticed that the formation 
of a new head and the growth of the new tentacles generally 
occurred more quickly and were the more considerable the 
nearer the incision lay to the oral pole. In animals with 
three heads, that lying nearest the foot had the smallest 
tentacles. 
When the incision was made very near the aboral pole, 
no new head whatsoever was formed. Fig. 25 shows an 
animal into which I made two incisions at the same time— 
b near the middle and ¢ near the aboral end of the animal. 
It will be seen that new tentacles have grown from the 
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