Studies on Regulation. 



All 



The course of regeneration in the posterior direction from a 

 level between the cephalic ganglia and the pharynx is illustrated 

 in Figs. 1-5. On these figures the organs are indicated in a 

 somewhat diagrammatic manner. The intestine is not drawn in 

 the old parts, but the general distribution of its branches is indi- 

 cated in the regenerated parts. Fig, i indicates the level of 

 the cut and the shape ol the anterior end before section. After 

 section the cut surface contracts and becomes concave posteriorly, 

 and within two or three days new unpigmented tissue appears. In 

 Fig. 2 the condition of the piece ten days after section is indi- 

 cated. An outgrowth of new tissue tapering posteriorly is present, 

 into which intestinal branches extend from the old part — and it 

 may be mentioned in passing that the intestine in regenerated 



areas apparently always arises in connection with the old parts 

 present. In the median line is a small ill-defined area which 

 represents the developing pharynx. Fig. 3, sixteen days after 

 section, shows a more advanced condition. The regenerated 

 area is longer and the pharynx is distinct. From this time on a 

 marked decrease in size occurs but the old part is much more 

 affected than the new, as is indicated by Fig. 4 twenty-seven 

 days after section. Here the new and old parts are of equal 

 length, the new being longer, though perhaps not containing more 

 material than in Fig. 3, and the old shorter. The pharynx 

 has increased in size and beyond it a small clear area, which may 

 be called the genital area, indicates that regeneration of the genital 

 ducts is taking place. Fig. 5 shows a stage fifty-one days after 



