148 STUDIES IN GENERAL PHYSIOLOGY 



spring from the lower cut surface; the upper cut surface/ 

 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. I 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 r<>\v 

 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 

 6 near the middle and c near the aboral end of the animal. 

 It will be seen that new tentacles have grown from the 



