246 



C. M. CHILD. 



Fig. 3 1 shows the oral end of a collapsed piece in which in- 

 folding has occurred. The numerous radiating foldings of the 

 body wall are evident. Figs. 4 and 5 show the aboral ends 

 of similar pieces. By this unfolding of the cut edges the open- 

 ings at the ends of the piece are reduced to slits as is seen from 



the figures, and various parts of the circumference of the cut 

 edge are approximated, though actual contact between parts of 

 the cut edge cannot occur everywhere, owing to the irregular 

 wrinkling of the margin as it folds inward. Indeed, since the 

 margin does not contract transversely to any great extent as 

 the infolding occurs, actual contact of all parts of the cut edge 

 is a physical impossibility, as it could occur only by the reduc- 

 tion of the cut margin to a point at the center of the circle formed 



1 In Figs. 3, 4, 5, 6, 7, 8, 9, 10, 12 the longitudinal pigmentation of the body is 

 not shown. The new tissue, where present, is indicated by stippling. 



