Studies on Regulation. 503 



indefinitely unless righted. Later, presumably after the effect of 

 shock had passed or the injury to the remaining portion of the 

 ganglia had been to some extent repaired, the behavior of the 

 piece B was observed to be somewhat different from that of the 

 pieces C. It was usually found adhering to the substratum and 

 parts of the margins of the body occasionally underwent irregular 

 extensions or contractions; in fact, the movements of this piece 

 were very much like those of Stylochus. Occasionally very slow 

 and irregular progression occurred. The pieces C continued to 

 behave as before. 



Six days after section: 



A. The two pieces are almost identical in appearance (Fig. 37). 

 Regeneration is occurring rapidly and the new tissue possesses 

 the characteristic tapering form with concave lateral margins. 

 The intestinal branches have penetrated the new tissue to a con- 

 siderable extent. At this time the new tissue was being used for 

 attachment to some extent and was often visibly stretched. 



B and C. The one piece B and the six pieces C — one having 

 died — show no marked difference in behavior or regeneration. 

 In some the cut surface is more contracted than in others, but in 

 all the amount of regeneration is very much less than in A. Fig. 

 38 shows the piece B and Fig. 39 the condition of the pieces C. 

 In the latter a few eye-spots are present but the small pieces 

 of the ganglia cannot be distinguished with certainty; in one case, 

 however, a small rounded mass of cells, probably the remains of 

 the ganglia, was protruding from the dorsal surface just posterior 

 to the cut surface and was apparently fused with the epithelium 

 of the new tissue; this is indicated in Fig. 39 by the shaded area. 

 In none of the pieces did the new tissue show any intestinal 

 branches. 



Eighteen days after section : 



A. Fig, 40 shows the condition of the two pieces of this 

 group. The new tissue has attained a length greater than the 

 old, the pharynx is well developed and the intestinal branches 

 extend throughout the new part. 



B. Fig. 41 shows the condition of the piece B. The new 

 tissue is much less in amount than in A and with few intestinal 



