FORM REGULATION IN CERIANTHUS. 



6 9 



a cylindrical piece slit down one side and represented as cut 

 across obliquely to show the separation of the cut surfaces ; 

 the cut surfaces have rolled inward and the oblique section at the 

 lower end of the figure shows that the inrolling along the longi- 

 tudinal cut is so great that the cut surfaces are not in contact. 

 The growth of new tissue and closure begins at the oral end (it 

 may begin at the aboral end also) where the cut surfaces are 

 much more closely approximated and the numerous folds afford 



FIG. 25. 



FIG. 27. 



FIG. 30. 



FIG. 28. 



FIG. 26. 



FIG. 29. 



FIG. 3 r. 



various points of contact. From this region it gradually extends 

 along the longitudinal cut, drawing the cut surfaces together as it 

 proceeds, as is shown by the two transverse sections, Figs. 28 

 and 29, Fig. 28 from a level where union has already occurred 

 (the upper transverse line in Fig. 27) and Fig. 29 from a level 

 just beyond where the cut surfaces have united (the level of the 

 lower transverse line in Fig. 27). In Fig. 28 the margins have 

 been drawn together and united, in Fig. 29 they are not yet in 

 contact but are nearer together than at the level of the oblique 

 section at the lower end of Fig. 27. In Fig. 30 the closure is 



