356 G. E. GATES. 



from the second series of operations. In Table III. is a con- 

 densed statement of hypomeric and hypermeric regeneration in 

 the same region but including results of more than one series of 

 operations. 



TABLE III. 



HYPOMERIC AND HYPERMERIC ANTERIOR ENDS REGENERATED AT CUTS 

 BETWEEN SEGMENTS Six AND EIGHTEEN. 



Number of Seg- Number of Seg- 



ments Removed. ments Regenerated. 



7 ' 3, 6, 8 



8 6, 7 



9 6, 8, 10 



10 ii 



11 8, 10 



12 8, 10 



13 - ii, 14 



14 



15 ii, 12, 13 



16 14 



17 .... 13, 14, 15 



REGENERATION OF POSTERIOR ENDS. 



No special attempt was made to study tail regeneration by an- 

 terior pieces. Numbers of amputated anterior portions were kept 

 in conditions similar to those of the regenerating tail pieces and 

 the daily records of the experiments contain some notes on these 

 amputated pieces. Anterior ends of more than twenty segments 

 may regenerate new tails. No information is available as to tail 

 regeneration anterior to segment twenty. Amputation at various 

 levels posterior to 20/21 usually resulted in rapid formation of 

 new posterior ends. None of these regenerating anterior portions 

 were kept alive longer than four weeks so that it is not possible 

 to make any positive statement as to the ratio of segments re- 

 placed to those lost. There is no reason to suspect, however, 

 that anterior portions of twenty segments or more cannot replace 

 all segments especially if provided with food. 



MUTILATIONS. 



While the first series of experiments was under way a collec- 

 tion of worms containing several regenerating specimens of P. 

 excavatus was brought into the laboratory. Arrangements were 



