5i6 CM. Child. 



margins of the head during creeping are famiHar to all who have 

 observed turbellarian movements. In the absence of the anterior 

 part of the head, which is the chief organ for these movements, 

 the other parts are apparently used to a greater extent than usual 

 and the new tissue becomes functional early in the course of 

 regeneration, being also extremely active. Discussion of the 

 question as to the relation between the motor activity and regener- 

 ation is postponed until the results of section at other levels have 

 been considered. 



2. Anterior Regeneration after Section Through the Ganglia. 



The results of section through the cephalic ganglia differ accord- 

 ing to the amount of ganglionic substance which remains intact- 

 In cases where the plane of section passes through the anterior 

 half of the ganglia the course of regeneration is essentially similar 

 to that after section anterior to the ganglia, but if the greater part 

 of the ganglionic substance is removed the regeneration is less 

 rapid and is usually very incomplete. 



The history of a single series will serve to illustrate these points. 

 In Series 17 (August 16, '02) ten specimens were cut transversely 

 as nearly as possible through the middle of the ganglia. There was 

 some variation in the position of the cut in the different speci- 

 mens: The three transverse lines in Fig. 6 will show approximately 

 the levels of the cuts: in seven cases the cut was near the level of 

 the anterior line, in one near the level of the middle line, and in two, 

 one of which was lost, it was near the level of the posterior line. 

 In the first eight pieces in which the cut passed through the middle 

 or anterior part of the ganglia anterior regeneration was complete; 

 in the ninth in which only the posterior portion of the ganglia 

 remained it was very incomplete. 



The posterior regeneration of the anterior pieces of this series 

 was described in the preceding paper (Child, '04b). It will be 

 remembered that seven of the anterior pieces (Group C) in which 

 the cut was anterior to the middle of the ganglia showed only 

 slight posterior regeneration, one piece (B) in which the cut 

 passed somewhere near the middle region of the ganglia regener- 

 ated somewhat more completely, and two pieces (Group A) in 



