3IO C. M. CHILD. 



the others probably being due to the fact that the cut separating 

 C from D in the one case was slightly more oral than in the 

 other three. 



The differences in the rapidity and the amount of regeneration 

 are best shown at the oral ends of regenerating pieces, for it is 

 difficult to determine with exactness the amount of actual new 

 tissue at the aboral ends of the pieces, since the line of demarca- 

 tion between the unpigmented tip and the normally pigmented 

 regions oral to it is not at all sharp, extending in many cases 

 over two to three millimeters. As regards the aboral ends the 

 pieces A and B showed little difference, but regeneration at the 

 aboral end of C was in all cases distinctly less than in A and B. 



In general the series seems to indicate that not only is regen- 

 eration less rapid with increasing distance from the oral end, but 

 that there is a corresponding difference in the amount of regen- 

 eration. In the pieces A, B and C the differences are compara- 

 tively slight, though without doubt present as can be seen by 

 comparing the data for these pieces thirty -five days after section. 

 When the pieces D are taken into consideration, however, the 

 difference between these and all other pieces is marked, for in no 

 case did these aboral ends show anything approaching complete 

 regeneration. There is then, according to these results, a rapid 

 decrease in regenerative power near the aboral end of the body, 

 and apparently complete absence of this power in an aboral region 

 representing approximately one fifth of the body-length. As 

 will be shown below, much smaller pieces than this from other 

 regions of the body are capable of complete regeneration ; more- 

 over, the size of the area within which regeneration does not 

 occur differs according to conditions. 



SERIES 54 AND 55. 



December i 5, 1902. The tentacles, disc and cesophageal region 

 were removed from twenty large specimens ; ten of the remain- 

 ing pieces were then divided by a transverse cut into two pieces, 

 A and B (Fig. 4), the cut being made near the aboral end so 

 that the pieces A comprised the greater part of the body aboral 

 to the oesophagus, while the pieces B represented the extreme 

 aboral end, about one sixth of the body-length. These two sets 

 of pieces constituted Series 54. 



