2 5 8 



C. M. CHILD. 



old body-wall are becoming involved in the regenerative changes 

 in the same manner as at the oral end, for the pigment stripes 

 are gradually fading out in the region which was before infolded. 

 Fig. 29 shows a still later stage in which the gradual fading of 

 the pigment-stripes is clearly seen. The significance of this loss 

 pigment is made clear by Fig. 30, a longitudinal section of the 

 aboral end at this stage. Here it is seen that a reduction of the 

 muscular layer is occurring, /. c., the old body-wall is becoming 



27 



28 



29 



involved in the regulative changes for a short distance oral to the 

 cut end : In other words the new aboral end is formed not 

 merely from the new tissue which closes the end soon after op- 

 eration, but, as in the regeneration of the oral end, in part from 

 tissue derived from the margins of the body-wall near to the cut 

 surface, by reduction of the muscular layer and growth of the 

 ectoderm and entoderm. Thus the distinction between " old 

 tissue" and "new tissue," at first well-marked, gradually disap- 

 pears in this region. 



