Studies on Regulation. 523 



when the piece was creeping; the other, Fig. 19, when the piece 

 was at rest. 



B. (Figs. 20-23.) Three pieces regenerated in this manner. 

 Here the contraction of the cut surface was somewhat greater than 

 in A and continued to increase thoughout the experiment. The 

 new tissue grew out from the wound at first in rounded form 

 (Fig. 21), but later acquired the tapering form shown in Fig. 22. 

 No traces of ganglia or eyes appeared at any time. The differ- 

 ences between the three pieces were slight. Figs. 22 and 23 

 represent, respectively, the extended form and the form during 

 quiescence of these pieces. The new tissue was more pointed 

 during the former condition. 



C. (Figs. 24-26.) One piece regenerated in this manner. 

 The course of regeneration in this case was much like that from 

 more posterior levels; the contraction of the cut surface was 

 greater than in the other cases and continued to increase. The 

 new tissue filled the space between the sides of the wound, but 

 never extended beyond the rounded margins of the old tissue. 

 In this piece the differences in form during movement and rest 

 were very slight. 



All of the pieces showed a somewhat greater degree of motor 

 activity and power of coordination than pieces from which the 

 anterior third or more of the body had been removed. After 

 stimulation progression continued for a considerable time and 

 the pieces changed their positions in the dishes from time to time 

 without perceptible external stimulation. Differences in motor 

 activity among the different pieces were not great but it seemed 

 to me that the pieces A and B were somewhat more active than 

 C, though'in all cases of this kind differences are not strongly 

 marked. In A and to a less extent in B the new tissue occasionally 

 showed movements resembling the searching movements of the 

 head in normal animals and some slight irregular play of the 

 margins of this region was observed. In C nothing of this kind 

 occurred. The changes in form of the anterior ends in A (Figs. 

 18 and 19) and B (Figs. 22 and 23) are of interest; when the 

 pieces extended and advanced the new tissue became somewhat 

 more slender and pointed as if it were pushed forward by internal 



