Studies on Regulation. 543 



parts, for the latter were originally much more extended and have 

 not lost that power completely. When the piece extends these new 

 parts cannot stretch as far as the old and consequently the piece 

 assumes the spiral form shown in Fig. 62. This is the nearest 

 approach to straightening that is possible in this piece. In this 

 condition the piece simply creeps over itself in the direction of the 

 arrow. As the piece becomes quiet it gradually assumes the form 

 of Fig. 60, though it is of course smaller than at that stage. Re- 

 generation in this piece has not advanced perceptibly during the 

 two months since the stage of Fig. 60. 



When we compare the two pieces it is evident that although the 

 amount of material removed was almost exactly the same in both 

 yet the results are very different. Here, as in other cases, the 

 only satisfactory interpretation of the difference in results is that 

 which regards them as the consequence of the differences in 

 functional activity of the two pieces. 



The results of longitudinal section near the median plane were 

 examined in numerous other series. In every case where one 

 piece contained most of the ganglionic tissue and the other only a 

 small portion the results were similar to those just described. In 

 cases where the plane of section was nearer the median plane the 

 difference between the two pieces was not as great and the piece 

 containing the smaller part of the ganglia regenerated the missing 

 parts more or less completely, and in all such cases the motor 

 activity and general regenerative power approached that of the 

 other piece as the part of the ganglia remaining became larger. 



In a few cases I succeeded in making the section so near to the 

 median plane that both pieces contained approximately equal 

 parts of the cephalic ganglia. Both behaved essentially like 

 normal animals and regenerated completely. Other cases of this 

 sort are described in another connection in an earlier paper 

 (Child, '04a). 



In all pieces capable of complete regeneration, like the right 

 piece in Series 64, certain features of interest were noted. First, 

 the new tissue in the region anterior to the pharynx regenerated 

 more rapidly than that in other regions and finally became wider 

 than at any other point (Figs. 57, 59, 61); second, in this region the 



