Studies on Regulation. IV. 121 



little motor activity. As regeneration proceeded, however, it be- 

 gan to revolve in circles scarcely greater in diameter than its own 

 length, appearing almost as if revolving on a pivot. 



The extreme curvature of the direction of locomotion renders 

 the piece of interest and certain points require consideration. 

 During the first period after section when locomotion was slight 

 regeneration was almost uniform over the whole cut surface, 

 i. e., there was no marked extension of the portion representing 

 the posterior region. Figure 28 represents the piece ten days 

 after section. A comparison of this figure with Figure 24 the 

 corresponding stage of Series II In which active locomotion has 

 occurred during the ten days suggests the possibility that the 

 tension or other conditions connected with locomotion may not 

 only determine the direction of outgrowth of new tissue but may 

 also affect the amount of regeneration, a point which will be dis- 

 cussed more fully elsewhere. 



Within the next few days the piece began to move in the manner 

 described above and twenty days after section appeared as repre- 

 sented in Figure 29. The axis of the regenerated portion forms 

 an angle of more than ninety degrees with the original longitud- 

 inal axis. The protruding mass of nerve tissue has united with 

 the new tissue and delayed growth at that point. The rapid 

 change of form which has occurred in the new tissue during ten 

 days indicates the marked effect which use of the parts exerts 

 upon regeneration. 



Twenty-two days later, forty-two days after section, the form 

 was much the same. Figure 30 represents the piece during or- 

 dinary locomotion. Frequently the piece assumed the form shown 

 in Figure 3 1 in which the tip of the tail was overlapped by the 

 lateral margin of the head. Figure 32 represents the form as- 

 sumed when the piece attached Itself by the tail and contracted, 

 drawing Itself backward; In this condition folds appear at x, 

 indicating that pressure Instead of tension occurs In that region. 



About ten days later the piece died without further changes. 

 This case differs from the preceding in that no marked change in 

 the direction of the body-axis occurred during the whole history, 

 although the piece lived as long as many others in which the 



