Studies on Regulation. 



479 



the same level which were not originally intended as controls for 

 them. These experiments were performed during the winter 

 when the temperature of the water was much lower than in sum- 

 mer and the total amount of regeneration in the various cases is 

 less than in summer experiments. In all cases the pieces were 

 kept until regeneration ceased, in order that comparison of the 

 total regeneration might be made. 



Series 73. Six pieces, each representing the region of the 

 body between the cephalic ganglia and the pharynx, were 

 obtained by the two transverse cuts indicated in Fig. 6. 



Series 82. Five pieces were obtained by transverse cuts just 

 anterior to the pharynx (the lower line in Fig. 6) but the head 



and cephalic ganglia were left intact. This series was not origi- 

 nally intended as a control for Series 73 consequently the inter- 

 vals between examinations are somewhat different though not 

 enough to prevent comparison. 



Fig. 7 shows the condition of the pieces of Series 73 eighteen 

 days after section and Fig. 8 the posterior ends of the pieces of 

 Series 82 fourteen days after section. In Series J^ the contraction 

 of the cut surface is greater, the new tissue contains fewer intes- 

 tinal branches, and the amount of the new tissue is somewhat less 

 than in Series 82. 



The different pieces of each series were so closely similar that 

 these two will serve as examples. 



