122 C. M. Child. 



change occurred. The continued circular locomotion is of course 

 directly responsible for the absence of change in form and this 

 in turn may be due to the delayed regeneration of the right ce- 

 phalic ganglion and consequent imperfect coordination of the 

 new lateral margin. As a matter of fact the right lateral margin 

 of the head appeared much less functionally activ^e than in the 

 other cases described. Regeneration of the ganglion was delayed 

 by the presence of the old ganglionic tissue which did not lose its 

 connection with the left ganglion until about four weeks after sec- 

 tion. And finally this long-continued attachment of the injured 

 ganglionic tissue to the left ganglion is doubtless to be ascribed 

 to the fact that scarcely any locomotion occurred during the first 

 two weeks after section, so that the new tissues with which the 

 ganglionic tissue was united were not subjected to tension which 

 would aid in removing this tissue from the region where its pres- 

 ence interfered with regeneration. I have no doubt that had the 

 piece lived sufficiently long before exhaustion occurred, the right 

 lateral margin of the head would have acquired its characteristic 

 activity and so would have counterbalanced the motor effect of 

 the old tissue, thus bringing about the change in direction of the 

 body-axis which occurred in Series I and II. 



In all of the cases described thus far the transverse cut surface, 

 originally posterior, becomes oblique in consequence of the con- 

 traction and in most cases the outgrowth of new tissue forming 

 the body occurs in a direction nearly perpendicular to this surface, 

 though there is considerable variation in different cases. Thus 

 in Figures 15 and 16 of Series I the angle between the axis of 

 the new body and the cut surface is somewhat more than 90°, 

 while in Figures 23, 24 and 25 of Series II it is approximately 

 90°, and in Figures 28, 29 and 30 of Series III It is again more 

 than 90°. These cases therefore are open to the objection that 

 the direction of growth may have been determined in some degree 

 by the direction of the cut surface rather than by the tension due 

 to movement, for it is a well known fact that in many cases regen- 

 eration takes place chiefly at right angles to the cut surface. Al- 

 though I did not consider this objection valid I prepared other 

 series in which the posterior cut surfaces of the pieces were 



