Studies on Regulation. 499 



experiments. If the level of the posterior ends of these pieces was 

 posterior to the pharynx the amount of regeneration was not very 

 great in any case, and differences were comparatively slight, 

 though apparently in agreement with the hypothesis, i. e., the 

 shorter pieces, those from which larger portions of the nerve cord 

 had been removed, seemed to show somewhat less regeneration 

 than the others, though it was often difficult to be certain that 

 chance individual differences were not concerned. The reasons 

 for the small amount of posterior regeneration from levels near 

 the posterior end of the body have been discussed in the preceding 

 section. It was also found that small pieces from the posterior 

 regions of the body live at most only a few weeks after section, 

 and for some time before death are much contracted and show 

 scarcely any motor activity. The contracted condition of these 

 pieces renders exact measurements impossible. 



In order to obtain results at all satisfactory it was necessary to 

 use pieces whose posterior ends were somewhat anterior to the 

 posterior end of the pharynx. With such pieces only the anterior 

 half of the body could be examined in this way, but we are justi- 

 fied in concluding that the same relations between functional 

 activity and regeneration exist in the different regions of the body. 



Two series of these experiments afforded definite results. In 

 one of these (Series 69) five pieces were cut as in Fig. 28, the 

 posterior ends being somewhat posterior to the middle of the 

 pharynx and the anterior ends at the anterior end of the pharynx. 

 In the other series (Series 71) five pieces were cut with posterior 

 ends at the same level but with anterior ends just posterior to the 

 cephalic ganglia (see the dotted line in Fig. 28). The two 

 series differ in respect to the region between the cephalic ganglia 

 and pharynx, which is present in one series and absent in the 

 other. Some difference in the motor activity of the two series 

 was noted, the pieces of Series 71 being considerably more active 

 and more successful in locomotion : the differences were, however, 

 not very great. Figs. 31 and 32 represent the two extremes 

 found among the pieces of Series 69 seventeen days after section 

 and Fig. 33 shows the condition of the pieces of Series 71 at the 

 same time, there being little difference among these. In general 



