272 



C. M. CHILD. 



series we have pieces ending orally at the same level of the body, 

 but of very different lengths. For purposes of direct comparison 

 as regards rapidity and amount of regeneration pieces must 

 always end at the same level of the parent body for the rapidity 

 and amount of regeneration differ markedly with the difference 

 in level (Child, '03^). 



Comparing 54/2 and 5 $A it was found that, although the 

 former pieces were about four times as long as the latter, the re- 

 generation at the oral end was the same in both during more than 

 a month. Finally in the latest stages the shorter pieces fell 

 slightly behind the others, but even then the differ- 

 ence in length of tentacles in the two sets was only 

 1-2 mm. Figs. I and 2 1 represent diagrammatic 

 sections of 54/2 and 55^4, thirty-one days after sec- 

 tion, when regeneration was about completed - 

 the experiment was performed during December 

 and January, consequently the total amount of re- 

 generation was much less than in the summer speci- 

 mens. The length of the tentacles in the figures 

 is the average length for the pieces of each set, 

 but since there was little difference in individual 

 pieces the figures would serve equally well to re- 

 present almost any of the pieces of the two sets. 

 The marginal tentacles in the pieces 54^ (Fig. i) 

 were 78 mm. in length, while those of 55^ (Fig. 

 2) were 6-8 mm. in length, i. e., in some of the 

 shorter pieces the tentacles were slightly shorter 

 than in the long pieces, probably in consequence of 

 the relative exhaustion of these pieces (see Child, 

 '03^). The labial tentacles show scarcely any per- 

 ceptible difference; the average length of these in 54^ is 1.25 

 mm. and in 55^ i mm. or a little more, but as these vary more 



1 All the figures of this paper are diagrammatic outlines drawn from measurements 

 of the living specimens. The stippled region at the aboral end represents the aboral 

 new tissue. It is represented as if the body were seen in surface view, not in section, 

 in order to indicate the shading in color between new and old parts and the absence 

 of a sharp distinction. The oral end of the body is represented in section but the 

 oesophagus is not drawn in most cases since it was usually impossible to determine its 

 length in regenerating specimens. 



FIG. i. 



FIG. 2. 



