WOUND CLOSURE AND POLARITY IN METRIDIUM 



457 



had been. On the second day the tentacle was mflated, had a 

 rounded end, and the color was alike in all parts. Not only was 

 this permanent structural closure not effected by muscle action, 

 but the muscular contraction of the nipple was diminished as it 

 proceeded. It was a process of radial in-closing so gradual as 

 not to be perceived save by the observation that, at successive 

 intervals, the nipple was shorter, and the opening, when the 

 stump was stimulated to contract, was smaller. 



Some study was made of this closure of the cut edges after the 

 muscle action was eliminated (fig. 3). In cut tentacles subjected 

 to chloretone there is a movement of the tissues of the tip radially 



Fig. 3 Camera sketch of longitudinal section of the distal cut end of a tentacle 

 stump after six and one-half hours in chloretone solution. The ectoderm and 

 entoderm have proceeded beyond the mesoglea (black). X 60. 



across the end of the tentacle, the pressure of fluid within holding 

 the end in rounded form as it closes. The process is, in effect, 

 somewhat like the initial inrolling; but that is abrupt while this is 

 gradual and slow. Other causes probably underlie the first inroll- 

 ing of the edges. In the final closure, the ectoderm moves in 

 advance of the other tissues, retaining its normal thickness for 

 some distance from the edge, though the cells become arranged 

 obliquely to the surf ace. of the layer. 



The appearance of a longitudinal section of a closed tentacle is 

 shown in figure 8, which represents the closed end of a tentacle 

 fragment which was not subjected to chloretone. Near the region 

 of union of the ectoderm of the opposite sides of the orifice, the cells 

 differ in shape from the adjacent normal cells, being much shorter 

 so that the layer is thinner at the region where the meeting occurs. 



