I 12 



C. M. Child. 



when one side of the body is cut away, since the axis usually be- 

 comes bent and there is nothing to counterbalance the effect of the 

 cilia and muscular movements of the opposite side. The results 

 of experiments with pieces of this kind demonstrated in a most 

 satisfactory manner the correctness of my belief. Numerous ex- 

 periments were performed, the results in all cases being unequivo- 

 cal. In the following sections some of these experiments are de- 

 scribed. 



CIRCULAR LOCOMOTION AND REGENERATION IN PIECES 



OF HEADS. 



A very satisfactory method of obtaining pieces which move in 

 curves is that of separating the anterior end by a cut a short dis- 

 tance posterior to the cephalic ganglia and splitting this piece lon- 

 gitudinally in half at or near the median line. This method of 

 preparation is illustrated by Figures 8 and 9. Figure 8 shows the 



Fig. 9. 



direction in which the cuts are made and Figure 9 the piece after 

 contraction of the cut surfaces has taken place. It is evident from 

 the latter figure that the contraction is an important factor in 

 bringing about circular locomotion. The longitudinal axis of the 

 piece becomes bent toward the cut side and movement in a straight 

 line is impossible. The curve of locomotion approximates more 

 or less closely the curve of the axis but does not necessarily coin- 

 cide with it since the irregular form of the piece often alters the 

 direction. The tissue giving rise to the new posterior region soon 

 begins to show the effect of the direction of movement and the tail 

 forms at an angle with the old parts. The description of the fol- 

 lowing series will serve to illustrate the course of regeneration. 



