486 C. M. Child. 



pares the behavior of two such pieces can fail to be convinced of 

 this fact and of its importance in connection with regeneration. 



The second question — why the difference in the amount of 

 regeneration in the two sets of pieces is most marked in the an- 

 terior regions of the body follows directly from the answer to the 

 first. It is evident that when a large part of the body has been 

 removed the regenerating tissue which arises in its place must 

 be subjected to a much greater degree of functional activity than 

 when it supplies the place of only a small part. For example if 

 the whole body posterior to the anterior end of the pharynx be 

 removed as in Series 73 and 82 the new tissue which grows out 

 from the cut surface is the functional representative of the part 

 removed. In locomotion it serves not only as a posterior end for 

 'attachment but also takes the place of the lateral margins of the 

 long piece removed. There can be little doubt that in such a 

 case all conditions correlated with functional activity must be 

 present in much greater degree than in new tissue which grows 

 out from a cut surface near the posterior end and which supplies 

 the place of only a small portion of the body. If these conditions 

 constitute factors in regeneration posterior regeneration must 

 decrease in amount with the approach of the cut surface to the 

 posterior end. The three sets of pieces with ganglia, Series 82 

 (Fig. 11), Series 78 (Figs. 15 and 16), and Series 80 (Figs. 24 and 

 25) show this difference in the amount of regeneration very clearly. 

 In the pieces without ganglia, however (Series 73, Figs. 9 and 10; 

 Series 79, Figs. 17 and 18; Series 81, Figs. 26 and 27), the differ- 

 ence is much less marked. In the first series in which the cut 

 surface was near the anterior end (Figs. 9 and 10) the amount 

 of regeneration is slightly greater than in the other two series 

 (Figs. 17 and 18 and 26 and 27) but between these two there is 

 little difference. 



It is necessary here to recall what was said in an earlier section 

 (pp. 471 and 472) on the relation between size and coordination in 

 pieces deprived of ganglia. Of two pieces with anterior ends at the 

 same level the larger piece seems to be slightly less helpless than the 

 smaller piece though the latter is often more active. In view of 

 these facts we cannot expect to find any such difference between 



